JP2013181073A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protective film which has excellent adhesion characteristics, transparency, and unwinding properties and of which the adhesive strength is maintained even after roll storage.SOLUTION: A surface protective film comprises at least two layers of a surface layer (A) and an adhesive layer (X), wherein the surface layer (A) is formed from a composition comprising 50-99.9 wt.% of a polyolefin resin (a-1) and 0.1-50 wt.% of a silylated olefin (a-2) (wherein the total of (a-1) and (a-2) is 100 wt.%).

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 easy to draw out from the roll and roll, and that maintains the adhesive strength even after roll storage.

  The surface protective film is used by sticking to adherends such as resin products, metal products, glass products, etc. mainly for optical applications and building materials to prevent scratches or foreign matter contamination during transportation, 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, the transition from cathode ray tube displays to flat panel displays such as liquid crystal displays and plasma displays has progressed. High transparency that can be used for these products, so-called optical product members, to prevent scratches and foreign matter from entering the surface protection film for protecting the member, or to perform product inspection with the surface protection film attached. Is required.

However, in the surface protection film having high transparency, since it is difficult to pay out from a roll-shaped product, it is made into a roll shape with a release film bonded to an adhesive layer, and is applied to an adherend. The release film is peeled off before use. 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. Furthermore, along with the thinning of the optical product member and the improvement of the production speed, it is desired that the feeding property when feeding from the roll shape is easier than ever.

Therefore, it is necessary to impart releasability to the surface layer of the surface protective film.
As a method of imparting releasability to the surface layer of the surface protective film, a method of selecting a polymer having a relatively high surface roughness for the surface layer or blending polymers having different compositions so that the surface roughness is relatively high Is used as a known method. However, the current situation is that the transparency is poor and sufficient payout performance cannot be obtained by the above method alone.

On the other hand, Japanese Unexamined Patent Application Publication No. 2009-235264 discloses a surface protective film in which an olefin wax is added to a surface layer mainly composed of homopolypropylene. However, in the method according to the publication, bleed-out to the surface of the olefin wax causes a shift to the adhesive surface during roll storage, and the adhesive strength may decrease with time, and the surface of the adherend may be contaminated.

Japanese Patent Application Laid-Open No. 2003-41216 discloses a surface protective sheet obtained by coating a release layer containing a release agent on the surface layer of the surface protective sheet. However, in the method according to the publication, a pretreatment step of the coating substrate surface is indispensable in order to ensure the interfacial adhesion between the mold release agent and the surface on which the mold release agent is applied, curing of the mold release agent, etc. The reaction time is required, which leads to a decrease in productivity. In addition, when the interface adhesion between the release agent and the surface to which the release agent is applied is low or the release agent is not sufficiently cured, the adhesive strength is reduced when the roll is stored. May contaminate the adherend surface.

JP 2009-235264 A JP 2003-41216 A

  The present invention is excellent in properties required as a surface protective film for protecting optical products, building material products and automobile parts during storage, transportation, processing and inspection, in particular, transparency and roll-out property, and roll storage. It is in providing the surface protection film with which adhesive strength is maintained afterwards.

  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 is a surface protective film comprising at least two layers of a surface layer (A) and an adhesive layer (X), the surface layer (A) is 50 to 99.9% by weight of the polyolefin resin (a-1), and Surface formed from a composition comprising 0.1 to 50% by weight of silylated polyolefin (a-2) (the total of (a-1) and (a-2) is 100% by weight) It relates to a protective film.

In the surface protective film of the present invention, the polyolefin resin (a-1) forming the surface layer (A) is a propylene homopolymer or a copolymer comprising propylene and at least one α-olefin other than 3 carbon atoms. Preferably it consists of.
Moreover, it is preferable to consist of the silylated polyolefin (a-2) hydrosilane compound which forms a surface layer (A), and the ethylene-type polymer which has terminal vinyl.

Further, in the surface protective film of the present invention, the adhesive layer (X) has an α-olefin elastomer and / or styrene α-, whose main component is an α-olefin having a melting point of less than 50 ° C. or a melting point of which is not observed. An olefin elastomer is preferred.
Furthermore, the surface protective film of the present invention is preferably a multilayer film obtained by extruding at least two layers of a surface layer (A) and an adhesive layer (X) from a T-die, and the surface layer (A) side. The surface roughness (Ra) is preferably 100 nm or less, and the haze measured at a thickness of 50 μm is preferably 15% or less.

  The surface protective film of the present invention is particularly excellent in transparency and roll-out property from the roll, and the adhesive strength is maintained even after roll storage, so that not only optical applications requiring high transparency, but also building material applications, As a protective film for automobile parts, the industrial utility value is extremely high.

  The surface protective film of the present invention has at least two layers of a surface layer (A) and an adhesive layer (X), or at least three layers of a surface layer (A), an intermediate layer (B) and an adhesive layer (X) as necessary. Consists of. Here, when the adhesive layer (X) is the innermost layer, the surface layer (A) is located in the outermost layer, and when the film is rolled, the surface layer (A) and the adhesive layer (X) are in contact with each other. To do.

The surface layer (A) is formed from 50 to 99.9% by weight of the polyolefin resin (a-1) and 0.1 to 50% by weight of the silylated polyolefin (a-2). Preferably, (a-1) is 60 to 99.7 wt%, and (a-2) is 0.3 wt% to 40 wt%, more preferably (a-1) is 70 to 99 wt%, and (A-2) is 1% by weight to 30% by weight (the sum of (a-1) and (a-2) is 100% by weight).

As polyolefin resin (a-1) which forms the surface layer (A) of the surface protection film of this invention, well-known polyolefin resin, such as a polypropylene and polyethylene, can be mentioned. Examples of polypropylene include homopolypropylene, random polypropylene, block polypropylene, and polyethylene. High pressure method low density polyethylene, linear low density polyethylene, and high density polyethylene can be exemplified. Among these, polypropylene is preferable from the viewpoint of transparency, rigidity, and heat resistance, and a propylene homopolymer or a copolymer composed of propylene and at least one α-olefin other than 3 carbon atoms is more preferable.

The silylated polyolefin (a-2) forming the surface layer (A) is obtained by reaction of a hydrosilane compound and a polyolefin having a terminal vinyl as disclosed in JP 2011-26448 A. .

The hydrosilane compound forming the silylated polyolefin (a-2) contains one or more structures represented by the following general formula (1).

X1
｜
-Si-Y- (1)
｜
X2

X1 and X2 in the structure represented by the general formula (1) represent a hydrogen atom, a halogen atom, a hydrocarbon group, an oxygen-containing group or a silicon-containing group, and may be the same or different, The hydrocarbon group, oxygen-containing group, and silicon-containing group may contain one or more heteroatoms, and Y is O, S, or NR (R represents a hydrogen atom or a hydrocarbon group).

X1 and X2 are one or more atoms or groups selected from the group consisting of a hydrogen atom, a halogen atom, a silicon-containing group having 1 to 50 silicon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group, and an alkyl group. In addition, it is preferable that at least one of X1 and X2 is a polysiloxyl group having 1 to 50 silicon. Among these, X1 and X2 are particularly preferably a hydrogen atom, a halogen atom or a hydrocarbon group. Y is particularly preferably O.

The polyolefin having terminal vinyl forming the silylated polyolefin (a-2) is selected from the group consisting of an ethylene chain or an olefin having 2 to 50 carbon atoms, except for one or more vinyl groups and excluding the vinyl group. An olefin polymer comprising a copolymer chain of two or more olefins, further comprising an ethylene homopolymer chain, a propylene homopolymer chain, or ethylene, propylene, butene, vinyl norbornene, and two or more double bonds More preferred is an olefin polymer comprising a copolymer chain of two or more olefins selected from the group consisting of cyclic polyenes having a chain and chain polyenes having two or more double bonds. In particular, an ethylene homopolymer, or an ethylene-based polymer composed of an ethylene chain and a copolymer chain composed of an ethylene chain and an α-olefin chain having 3 or more carbon atoms is preferred. The ethylene homopolymer, copolymer of ethylene and propylene More preferred are copolymers and copolymers of ethylene and norbornene.

Silylated polyolefin (a-2) is -Si-C-C in which -Si-H in the hydrosilane compound reacts with -C = C (vinyl group) contained in the polyolefin having terminal vinyl. -Including a structure, and when the structure represented by the general formula (1) in the hydrosilane compound and a plurality of vinyl groups in the polyolefin having terminal vinyl are plural, the above -Si-H and -C = C (vinyl group) ) To form a network polymer, which is not preferable.

The Si content of the silylated polyolefin (a-2) is preferably in the range of 3 to 50 wt%, more preferably in the range of 4 to 40 wt%.
The weight average molecular weight (Mw) is preferably in the range of 300 to 300,000, more preferably in the range of 600 to 60,000.

In the composition for forming 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.

As the pressure-sensitive adhesive layer (X) of the surface protective film of the present invention, any known pressure-sensitive adhesive used as the pressure-sensitive adhesive layer of the surface protective film can be used. From the viewpoint of damage, transfer of the adhesive to the adherend, so-called adhesive residue, α-olefin elastomer and / or styrene elastomer is preferable.

The α-olefin-based elastomer is a copolymer mainly composed of an α-olefin having 3 or more carbon atoms and having a melting point of less than 50 ° C. or a melting point measured by a differential scanning calorimeter (DSC). Specifically, for example, propylene homopolymer, propylene / ethylene copolymer, propylene / ethylene / 1-butene copolymer, 1-butene homopolymer, 1-butene / ethylene copolymer, 1-butene / propylene Copolymer, 4-methylpentene-1 homopolymer, 4-methylpentene-1 / propylene copolymer, 4-methylpentene-1 / 1-butene copolymer, 4-methylpentene-1 / propylene / 1 -Butene copolymer and propylene / 1-butene copolymer, preferably propylene / ethylene / 1-butene copolymer.

The melt flow rate (MFR) measured at 230 ° C. of the α-olefin-based elastomer is in the range of 0.1 to 100 g / 10 minutes, more preferably 0.5 to 50 g / 10 minutes.
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 hydrides thereof, styrene / isobutylene / styrene triblock copolymer (SIBS), and styrene / isobutylene diblock copolymer (SIB). Preferably, a styrene / isobutylene / styrene triblock copolymer (SIBS), a styrene / isobutylene diblock copolymer (SIB), or a styrene / isobutylene / styrene triblock copolymer (SIBS) and a styrene / isobutylene diblock copolymer It is a blend of polymer (SIB).

  By using the above α-olefin elastomer and / or styrene elastomer alone or by blending components having different compositions, 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 strength, and in the range not impairing the characteristics of the present invention, the above α-olefin elastomer and / or styrene elastomer, polyolefin such as polyethylene and polypropylene, Resin modifiers such as acid-modified polyolefins, polyesters and polyamides, tackifiers such as petroleum resins, hydrogenated petroleum resins, styrene resins, chroman indene resins, rosin derivatives, terpene resins, antistatic agents, crystals Various additives such as a nucleating agent and an antioxidant may be added.

  In the present invention, it is also possible to provide at least one intermediate layer (B) between the surface layer (A) and the adhesive layer (X). For the purpose of controlling the mechanical strength and transparency of the film, and when the interlayer adhesion between the surface layer (A) and the adhesive layer (X) is insufficient, a polyolefin resin, an adhesive resin or an adhesive is used as an intermediate layer. May be used.

  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, various olefin type elastomers, etc. can be used. When the intermediate layer is used as an adhesive layer, modified polyolefin, various olefin elastomers, styrene elastomers, polyester elastomers and the like are used. These may be used alone or by blending components having different compositions, and if necessary, as long as they do not impair the properties of the surface protective film of the present invention, antistatic agents, antioxidants, and weather resistance. It is also possible to add various additives such as an agent and a crystal nucleating agent, and various resin modifiers. Among these, from the viewpoint of productivity and transparency, it is preferable to use polypropylene or α-olefin elastomer as the intermediate layer.

  There is no particular limitation on the method of laminating the surface layer (A) and the adhesive layer (X), and if necessary, the intermediate layer (B). For example, the surface layer obtained by T-die molding or inflation molding in advance. A method of laminating other layers on a film by a known laminating method such as extrusion lamination or extrusion coating, or after each layer is independently formed into a film, each obtained film is laminated by dry lamination. In view of productivity, coextrusion molding in which each component of the surface layer, intermediate layer, and adhesive layer is subjected to molding using a multilayer extruder is preferable, and T-die molding is preferable from the viewpoint of thickness accuracy. More preferred.

The thickness of the surface layer (A) in the surface protective film of the present invention is 0.1 to 100 μm.
The thickness is preferably 0.3 to 50 μm, more preferably 0.5 to 30 μm, and still more preferably 1 to 20 μm. As thickness of adhesion layer (X), it is 0.1-50 micrometers, Preferably it is 0.3-40 micrometers, More preferably, it is 0.5-30 micrometers.
The thickness of the surface protective film of the present invention is 1 to 300 μm, preferably 2 to 200 μm, more preferably 3 to 100 μm.

By using the surface layer (A), the pressure-sensitive adhesive layer (X), and the intermediate layer (B) as necessary, it is excellent in transparency and rollability from the roll, and has adhesive strength even after roll storage. A surface protective film to be maintained is obtained, and can be suitably used particularly for optical applications.
The surface roughness (Ra) on the surface layer (A) side of the surface protective film of the present invention is preferably 100 nm or less, and the preferred transparency is 15% or less as haze measured with a thickness of 50 μm.

  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 strength:
The acrylic plate is cut to a width of 50 mm and a length of 125 mm, and a surface protective film is attached to the test plate using a 2 kg rubber roller. Next, under the conditions of room temperature 23 ° C. and humidity 50% RH, the peeling force when peeling (180 degree peeling) at a rate of 300 mm / min was measured using an orientec Tensilon universal testing machine RTC-1225A. The peeling force per 50 mm width is defined as the adhesive strength (N / 50 mm).

Peel strength:
As an index of the unwinding force from the roll, a sample was prepared in the same manner as the adhesive strength measurement, and the surface of the adhesive layer of the other surface protective film was placed on the surface of the surface protective film attached. Install to fit and stick using 2kg rubber roller. Next, surface protection film surface when peeling (180 degree peeling) at a rate of 300 mm / min using Orientec Tensilon Universal Tester RTC-1225A under conditions of room temperature 23 ° C. and humidity 50% RH The peel force between the surface of the layer and the surface of the adhesive layer is measured, and the peel force per 50 mm width is defined as the peel strength (N / 50 mm).
At this time, the two surface protective films to be used are the same composition film.

Haze:
Based on JIS K7105, it measured with the film of thickness 50 micrometers.
Surface roughness (Ra):
The measurement was made using a non-contact surface roughness meter (model number: NT-2000 SYSTEM-Veeco).

Melt flow rate (MFR):
Based on ASTM D1238, the load was 2.16 kg and the temperature was 230 ° C.
Melting point:
In accordance with JIS K 7121, using a differential scanning calorimeter (DSC), the highest temperature at the peak of the melting peak measured at a heating rate of 10 ° C. per minute was defined as the melting point.

Example 1
[Raw materials]
PP-1: Homopolypropylene
(Melting point 160 ° C., MFR (230 ° C.) 7 g / 10 min)
SiPO-1: Silylated polyethylene
Created by the method shown in the example of JP 2011-26448 A,
Silylated polyethylene
(Melting point 117 ° C., Mw = 7,500, Si content 24%)
OE-1: Propylene / ethylene / 1-butene copolymer
(Ethylene content 13 mol%, butene content 19 mol%, melting point not observed,
MFR = 7g / 10min)
SE-1: Styrene-isobutylene-styrene triblock polymer
(Product name: Shibster, Brand name: 062T, MFR = 8.0 g / 10 min.,
Kaneka)
SE-2: Styrene-isobutylene-styrene triblock polymer / styrene-
Isobutylene diblock polymer
(Product name: Shibster, Brand name: 062M, MFR = 8.0g / 10min,
Kaneka)
For the surface layer, intermediate layer, and adhesive layer, the resin is supplied to a three-type three-layer T-die molding machine having a die width of 400 mm that has a single screw extruder of 40 mmφ, and the surface layer thickness is 5 μm. A surface protective film having an intermediate layer thickness of 38 μm, an adhesive layer thickness of 7 μm, and a total thickness of 50 μm was obtained. The evaluation results of the obtained film are shown in Table 1.

Examples 2, 3, 4 and Comparative Example 1
A surface protective film was obtained in the same manner as in Example 1 except that the resin compositions of the various layers were changed to the resin compositions shown in Table 1. The evaluation results of the obtained film are shown in Table 1.
The surface protection film obtained in Example 2 was cut into a paper tube having an inner diameter of 3 inches with a width of 64 mm and a length of 30 m, and 180 in a roll state in which the surface layer (A) and the adhesive layer (X) were in contact with each other. After storage at room temperature for days, roll storage adhesive strength was also evaluated in the same manner as the measurement of adhesive strength.

The obtained results are shown in Table 1.
(Table 1)

The surface protective film of the present invention can be widely used as a protective film for optical materials requiring high transparency, building materials and automobile parts.

Claims (6)

  It is a surface protective film consisting of at least two layers of a surface layer (A) and an adhesive layer (X), and the surface layer (A) is a polyolefin resin (a-1) 50 to 99.9% by weight and a silylated polyolefin (a -2) A surface protective film formed from a composition comprising 0.1 to 50% by weight (the total of (a-1) and (a-2) is 100% by weight).   The polyolefin resin (a-1) forming the surface layer (A) is composed of a propylene homopolymer or a copolymer composed of propylene and at least one α-olefin other than 3 carbon atoms. Item 11. A surface protective film according to Item 1.   The surface according to any one of claims 1 to 2, wherein the silylated polyolefin (a-2) forming the surface layer (A) comprises a hydrosilane compound and an ethylene polymer having a terminal vinyl. Protective film.   The adhesive layer (X) is formed of an α-olefin elastomer and / or a styrene α-olefin elastomer mainly composed of an α-olefin having a melting point of less than 50 ° C. or a melting point of which is not observed. The surface protection film according to claim 1, wherein the surface protection film is a film.   The surface protective film according to any one of claims 1 to 5, 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. The surface protective film according to any one of claims 1 to 6, wherein the surface roughness (Ra) on the surface layer (A) side is 100 nm or less and haze measured at a thickness of 50 µm is 15% or less.