JP2008119911A - Surface protection film - Google Patents

Abstract

A surface protective film excellent in adhesive properties, transparency, rewinding properties and heat resistance is provided.
A surface protective film comprising at least two layers of a surface layer (A) and an adhesive layer (X), wherein the surface layer (A) has a melt flow rate measured at 190 ° C. of 0.01 to 20 g / 10. And an adhesive layer (X) is formed from an ethylene polymer (a) having a specific melt tension value, and the adhesive layer (X) is composed of 20 to 100 mol% of an α-olefin having 3 or more carbon atoms. A surface protective film formed from a composition comprising the olefin polymer (b).
[Selection figure] None

Description

  The present invention relates to a surface protective film used for optical products, building materials, automobile parts and the like. More specifically, the present invention relates to a surface protective film that is excellent in adhesive properties, transparency, and heat resistance, has little contamination to an adherend, and is easy to be drawn out from a roll.

  The surface protective film is used by sticking to adherends such as resin products, metal products, glass products, etc. mainly for building materials and optical applications, and prevents them from being scratched or contaminated during transport, storage or processing. Plays. These surface protective films generally comprise a non-adhesive surface layer and an adhesive layer for adhering to the adherend. The surface layer is usually formed from a polyolefin such as polyethylene or polypropylene, a polyester such as polyethylene terephthalate, or a vinyl polymer such as polyvinyl chloride.

  In recent years, development of materials used for liquid crystal screens, plasma displays (PDP), rear projection screens, and so on, so-called optical products, has been progressing. The surface protective film for protecting these optical products is not only scratched or mixed with foreign matter, but also transparent so that product inspection can be performed with the surface protective film applied, and even when applied at high temperatures. Properties such as the development of adhesive strength are desired.

  On the other hand, when the surface protective film is used for building materials or automotive parts, it may be thermoformed with the surface protective film attached, and high heat resistance is required.

  In addition, since a surface protective film having a relatively high adhesive strength is difficult to be fed out from a roll-shaped product, it is formed into a roll shape with a release film bonded to an adhesive layer, and applied to an adherend. The release film is peeled off and used. When such a process is employed, a large amount of waste is generated, and thus a surface protective film that can be easily fed out from a roll without a release film is required.

Japanese Unexamined Patent Application Publication No. 2006-116769 discloses a surface protective film mainly composed of a polyethylene component. However, although the method according to the publication can be applied to some use members, the adhesive strength is low and the transparency is insufficient, and the use of the adherend is limited.
JP 2006-116769 A

  The present invention has characteristics required as a surface protective film for protecting optical products, building material products and automobile parts during storage, transportation, processing and inspection, in particular, adhesive properties, transparency, heat resistance and feeding from a roll. It is in providing the surface protection film excellent in property.

As a result of intensive studies in view of the above problems, the present inventors have found that the above problems can be solved by a surface protective film having a surface layer made of a specific resin composition, and have completed the present invention.
That is, the present invention
1. A surface protective film comprising at least two layers, a surface layer (A) and an adhesive layer (X), and the surface layer (A) has a melt flow rate (abbreviated as MFR ₁₉₀ ) measured at 190 ° C. of 0.01 to 20 g. The relationship between the melt tension (abbreviated as MT) measured at 190 ° C. and MFR _{190 in} the range of / 10 minutes is represented by the following formula (1)
40 × (MFR ₁₉₀ ) ^−0.67 ≦ MT ≦ 250 × (MFR ₁₉₀ ) ^−0.67
(1)
A composition comprising an olefin polymer (b) which is formed from an ethylene polymer (a) satisfying the above and the adhesive layer (X) is composed of 20 to 100 mol% of an α-olefin having 3 or more carbon atoms. A surface protective film characterized by being formed,

2. 2. The surface protective film according to claim 1, wherein the olefin polymer (b) is a propylene copolymer,
3. The surface protective film according to 1 or 2, wherein the adhesive layer (X) is a propylene copolymer, and the total number of carbon atoms of each monomer is 8 or more,
4). The surface protective film according to any one of 1 to 3, wherein the ethylene polymer (a) is a high-pressure low-density polyethylene,
5. The surface protective film according to any one of 1 to 4, which is a multilayer film obtained by extruding at least two layers of a surface layer (A) and an adhesive layer (X) from a T-die,
It is.

  The surface protective film of the present invention is excellent in adhesive properties, transparency, unwinding power and heat resistance, and has an extremely high industrial value as a protective film for optical applications, building materials applications, and automotive parts applications.

Next, the present invention will be described in detail.
The surface protective film of the present invention comprises at least two layers of a surface layer (A) and an adhesive layer (X).

The surface layer (A) is formed from an ethylene polymer (a).
The ethylene polymer (a) has a melt flow rate (abbreviated as MFR ₁₉₀ ) measured at 190 ° C. of 0.01 to 20 g / 10 minutes, preferably 0.03 to 15 g / 10 minutes, more preferably 0.00. It is in the range of 05-12 g / 10 minutes.
The relationship between the melt tension (abbreviated as MT) measured at 190 ° C. and the MFR ₁₉₀ is represented by the following formula (1);
40 × (MFR ₁₉₀ ) ^−0.67 ≦ MT ≦ 250 × (MFR ₁₉₀ ) ^−0.67
(1)
Meet.
Here, the melt tension (MT) is a value obtained by measuring a stress when a melted ethylene polymer is stretched at a constant speed. Specifically, a value (unit: mN) measured using a Toyo Seiki MT measuring instrument under conditions of a resin temperature of 190 ° C., an extrusion speed of 15 mm / min, a winding speed of 15 m / min, a nozzle diameter of 2.09 mmφ, and a nozzle length of 8 mm. ).

The ethylene polymer (a) has a density of 0.900 to 0.960 g / cm ³ , preferably 0.905 to 0.950 g / cm ³ , more preferably 0.910 to 0.930 g / cm ³ . Is in range.
When the MFR ₁₉₀ , MT, and density are in the above ranges, the formability of the surface protective film of the present invention and the feedability from the roll are improved.

  Such an ethylene-based polymer can be obtained by homopolymerization of ethylene or copolymerization of ethylene and another α-olefin in the presence of a catalyst capable of polymerizing ethylene. Low density polyethylene or long chain branched low density polyethylene. More preferably, it is a high pressure method low density polyethylene.

The surface layer (A) in the surface protective film of the present invention is formed from the ethylene polymer (a).
In the ethylene polymer (a) used as the surface layer (A), an antistatic agent, a release agent, an antioxidant, a weathering agent, a crystal nucleating agent, etc., as long as the characteristics as the surface protective film of the present invention are not impaired. These additives and resin modifiers such as polyolefin, polyester, polyamide, and elastomer can be added.

  The ethylene polymer (a) and additives and modifiers added as necessary are kneaded with, for example, a single-screw or twin-screw extruder or a feeder ruder, and further processed into a film. However, it can also be directly put into a T-die molding machine that also has an extruder to form the surface layer of the surface protective film of the present invention.

The adhesion layer (X) is formed from a composition comprising an olefin polymer (b) having 20 to 100 mol% of α-olefin having 3 or more carbon atoms.
The olefin polymer (b) is composed of 20 to 100 mol%, preferably 40 to 100 mol%, more preferably 60 to 100 mol% of an α-olefin having 3 or more carbon atoms. Here, when 2 or more types of α-olefins having 3 or more carbon atoms are contained in the olefin polymer (b), the total content thereof is shown. Examples of the α-olefin having 3 or more carbon atoms include propylene, 1-butene, 4-methylpentene-1, 1-hexene, 1-octene, 1-decene, 1-dodecene, and the like. -Butene, 4-methylpentene-1.

  The preferred olefin polymer (b) is a propylene polymer comprising propylene as a constituent component, preferably 20 to 100 mol%, preferably 30 to 90 mol%. Specific examples thereof include amorphous or low crystallinity. Propylene homopolymer, propylene / ethylene copolymer, propylene / 1-butene copolymer, propylene / ethylene / 1-butene copolymer, propylene / 4-methylpentene-1 copolymer, propylene / 1-butene / 4-methylpentene-1 copolymer. Preferably, a propylene-based copolymer in which the total number of carbon atoms of the respective constituent monomers is 8 or more, more preferably in the range of 9 to 20, specifically, a propylene / ethylene / 1-butene copolymer, Propylene / 4-methylpentene-1 copolymer and propylene / 1-butene / 4-methylpentene-1 copolymer.

  As the adhesive layer (X) of the surface protective film of the present invention, the olefin copolymer can be used alone, but for the purpose of controlling the adhesive force, the composition with other olefin elastomers or styrene elastomers. It can also be used as a product.

  Examples of the olefin elastomer include an α-olefin polymer or copolymer having 2 to 20 carbon atoms, or a copolymer of ethylene and an unsaturated carboxylic acid or unsaturated carboxylic acid ester. Specifically, ethylene / propylene copolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, ethylene / 4-methylpentene-1 copolymer, ethylene / 1-octene copolymer 1-butene homopolymer, 1-butene / ethylene copolymer, 1-butene / propylene copolymer, 4-methylpentene-1 homopolymer, ethylene / vinyl acetate copolymer, ethylene / methacrylic acid copolymer And ethylene / methyl methacrylate copolymer.

  As the styrene elastomer, a known styrene elastomer having a polystyrene phase as a hard segment can be used. Specifically, styrene-butadiene copolymer (SBR), styrene-isoprene-styrene copolymer (SIS), styrene-butadiene-styrene copolymer (SBS), styrene-ethylene-butadiene-styrene copolymer ( SEBS), and their hydrides.

  By using the olefin copolymer (b) alone or as one component of the composition, the pressure-sensitive adhesive layer (X) in the surface protective film of the present invention can be formed. Further, in the present invention, for the purpose of controlling the adhesive force, and within the range not impairing the characteristics of the present invention, resin modifiers such as polyolefins such as polyethylene and polypropylene, acid-modified polyolefins, polyesters and polyamides, Various additives such as an inhibitor, a crystal nucleating agent and an antioxidant may be contained.

  The said olefin copolymer (b) and the resin modifier or additive as needed can be made into the surface protection film of this invention by laminating | stacking with the said surface layer (A).

  Although there is no restriction | limiting in particular about the method of laminating | stacking surface layer (A) and adhesion layer (X), well-known extrusion lamination, extrusion coating, etc. on the surface layer film obtained by T-die shaping | molding or inflation shaping | molding previously The method of laminating by the above-mentioned laminating method, the method of laminating each film by dry lamination after forming the surface layer and the adhesive layer independently into a film, etc. are mentioned. From the viewpoint of productivity, the surface layer, the adhesive layer Coextrusion molding in which each of the above components is subjected to molding in a multilayer extruder is preferred.

In the present invention, it is possible to provide at least one intermediate layer between the surface layer (A) and the adhesive layer (X). Moreover, when the adhesive force with the surface layer (A) and the pressure-sensitive adhesive layer (X) is insufficient, an adhesive or an adhesive layer may be used as the intermediate layer.
Although there is no restriction | limiting in particular as an intermediate | middle layer, Generally, crystalline polyolefins, such as a polypropylene and polyethylene with melting | fusing point of 100 degreeC or more, polyester, polyamide, polyolefin-type elastomer, etc. can be used. When the intermediate layer is used as an adhesive layer, modified polyolefin, polyolefin elastomer, styrene elastomer, polyester elastomer, or the like is used. Among these, from the viewpoint of productivity and transparency, it is preferable to use polypropylene or polyolefin elastomer as the intermediate layer.

  As thickness of the surface layer (A) in the surface protection film of this invention, it is 0.05-200 micrometers, Preferably it is 0.5-100 micrometers, More preferably, it is 1-30 micrometers, More preferably, it is 1-15 micrometers. As thickness of adhesion layer (X), it is 0.05-50micro, Preferably it is 0.3-40micro, More preferably, it is 0.5-30micrometer.

  The thickness of the surface protective film of the present invention is 0.1 to 500 μm, preferably 0.5 to 400 μm, more preferably 3 to 300 μm, including an intermediate layer that may be provided as necessary.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[Evaluation method]
Adhesive force:
The acrylic plate is cut into a width of 50 mm and a length of 125 mm, and is attached to the test plate using a pressure roll laminator. Next, the peel force when peeled at a speed of 300 mm / min (180 degree peel) is measured, and the peel force per 25 mm width is defined as the adhesive strength (N / 25 mm).
Here, the measurement of sticking and peeling force was performed on 23 degreeC conditions.
Unwinding force (feeding ability):
Using a roll-shaped sample, the peeling force (N / 25 mm) when peeling from the roll at a speed of 300 mm / min is measured and used as the rewinding force.
Haze: Measured with a film having a thickness of 50 μm according to JIS K7105.

Example 1
The following resin composition is supplied to a three-type three-layer T-die molding machine having a die width of 500 mm, which is equipped with a 30 mmφ short axis extruder for the surface layer and the adhesive layer and a 40 mmφ short axis extruder for the intermediate layer. A surface protective film having a thickness of 10 μm, an adhesive layer thickness of 10 μm, an intermediate layer thickness of 30 μm, and a total thickness of 50 μm was obtained. The evaluation results of the obtained film are shown in Table-1.
Surface layer:
High-pressure low-density polyethylene (brand name: Mirason 1770P, density 0.927 g / cm ³ , MFR ₁₉₀ = 5.9 g / 10 min, MT = 35 mN, manufactured by Prime Polypro) 100% by weight.
Middle layer:
Random polypropylene (brand name; F327, melting point = 138 ° C., MFR ₂₃₀ (melt flow rate measured at 230 ° C.) = 7 g / 10 min, manufactured by Prime Polypro Co.) 100% by weight.
Adhesive layer:
80% by weight of propylene / ethylene / 1-butene copolymer (ethylene content 13 mol%, butene content 19 mol%, no melting point observed, MFR ₂₃₀ = 7 g / 10 min).
Random polypropylene (brand name: F327, melting point = 138 ° C., MFR ₂₃₀ = 7 g / 10 min, manufactured by Prime Polypro) 20% by weight.

Example 2 and Comparative Example 1
A surface protective film was obtained in the same manner as in Example 1 except that the resin composition of the various layers was changed to the resin composition shown in Table-1. The evaluation results of the obtained film are shown in Table-1.

HPLDPE;
High-pressure method low-density polyethylene (brand name; Mirason 1770P, density 0.927 g / cm ³ , MFR ₁₉₀ = 5.9 g / 10 min, MT = 32 mN, manufactured by Prime Polypro).
LLDPE;
Linear low-density polyethylene (brand name: Evolue SP2540, density 0.923 g / cm ³ , MFR ₁₉₀ = 3.6 g / 10 min, MT = 11 mN, manufactured by Prime Polypro).
h-PP;
Homopolypropylene (brand name: F107BV, melting point = 160 ° C., MFR ₂₃₀ = 7 g / 10 min, manufactured by Prime Polypro).
r-PP;
Random polypropylene (brand name; F327, melting point = 138 ° C, MFR ₂₃₀ = 7 g / 10 min, manufactured by Prime Polypro).
PEBR-1;
Propylene / ethylene / 1-butene copolymer (ethylene content 13 mol%, butene content 19 mol%, no melting point was observed, MFR ₂₃₀ = 7 g / 10 min).
PEBR-2;
Propylene / ethylene / 1-butene copolymer (ethylene content 12 mol%, butene content 19 mol%, melting point not observed, MFR ₂₃₀ = 7 g / 10 min).
HSBR;
Styrenic elastomer (hydrogenated SBR, JSR Dynalon 1320P).
PMPBR;
Propylene · 4-methylpentene-1 · butene-1 copolymer (propylene content 50 mol%, 4-methylpentene-1 content 30 mol%, butene content 20 mol%, MFR ₂₃₀ = 10 g / 10 min).

  The surface protective film of the present invention is excellent in adhesive properties, transparency, unwinding force, and heat resistance, and has an extremely high industrial utility value as a protective film for optical applications, building material applications, and automotive parts applications.

Claims (5)

A surface protective film comprising at least two layers, a surface layer (A) and an adhesive layer (X), and the surface layer (A) has a melt flow rate (abbreviated as MFR ₁₉₀ ) measured at 190 ° C. of 0.01 to 20 g. The relationship between the melt tension (abbreviated as MT) measured at 190 ° C. and MFR _{190 in} the range of / 10 minutes is represented by the following formula (1)
40 × (MFR ₁₉₀ ) ^−0.67 ≦ MT ≦ 250 × (MFR ₁₉₀ ) ^−0.67
(1)
A composition comprising an olefin polymer (b) which is formed from an ethylene polymer (a) satisfying the above and the adhesive layer (X) is composed of 20 to 100 mol% of an α-olefin having 3 or more carbon atoms. A surface protective film formed.   The surface protective film according to claim 1, wherein the olefin polymer (b) is a propylene copolymer.   The surface protective film according to claim 1 or 2, wherein the adhesive layer (X) is a propylene-based copolymer, and the total number of carbon atoms of each monomer is 8 or more.   The surface protective film according to any one of claims 1 to 3, wherein the ethylene polymer (a) is a high-pressure low-density polyethylene.   The surface protective film according to any one of claims 1 to 4, which is a multilayer film obtained by extrusion molding at least two layers of a surface layer (A) and an adhesive layer (X) from a T-die.