JPH1121519A - Surface-protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low-cost surface-protective film having high rigidity and heat resistance, therefore reduced in wrinkling and shrinking in high-temperature use, having weak blocking force during rewinding, having high initial pressure- sensitive adhesiveness and undergoing a small change in pressure-sensitive adhesiveness with the lapse of time after sticking. SOLUTION: There is provided a surface-protective film prepared by laminating a surface layer on one side of a base layer and laminating a pressure- sensitive adhesive layer on the other side, wherein the base layer is made from a resin based on polypropylene, the surface layer is made of a resin based on polyethylene, the pressure-sensitive adhesive layer is made of a pressure- sensitive material based on a copolymer of a 2-12C α-olefin, and the force of rewinding is at most 200 g/25 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protection film for covering and protecting the surface of a molded product such as metal, glass, plastic or the like, a processed product, a painted product, etc., and particularly to an adherend. The present invention relates to a peelable surface protective film that is peeled after being subjected to processing such as transport, storage, and processing.

[0002]

2. Description of the Related Art Steel, metals such as aluminum, glass,
In order to protect the surface of plastics, wood and other plates and other molded products, their processed products and painted products, a peelable surface protection film was applied and transported, stored, and isolated. Later, they are used after peeling.

[0003] This surface protective film can be easily adhered by being adhered to an adherend, and does not easily peel off during transportation, storage, or processing of the adherend. It is required to be easily peelable. Therefore, the surface protective film has moderate adhesion to the adherend, flexibility enough to prevent the film itself from damaging the surface to be protected, corrosion resistance, and resistance to oils such as mechanical oils. Or it does not change with temperature, and furthermore, according to the work forming of the adherend, the mechanical properties such as elongation properties, scratch resistance, tear resistance, cutting, and punching properties are appropriate,
Various properties such as having heat resistance are required. In addition, since this kind of surface protective film is consumed in large quantities and is promptly discarded, it is required that it can be manufactured at low cost.

Heretofore, as a surface protection film of this type, a film obtained by applying an acrylic or rubber-based pressure-sensitive adhesive to one surface of a base film mainly composed of a polymer such as low-density polyethylene, polypropylene, or polyvinyl chloride is known. in use. However, since this type of surface protective film is a surface protective film obtained by applying a pressure-sensitive adhesive made of a different resin to one side of a film serving as a substrate layer, there is a problem in adhesion between the film and the pressure-sensitive adhesive layer, Since the method of using release paper to reduce the unwinding force due to blocking or the method of adding an additive to the base layer has been adopted, the sticking workability is poor, and the temporal change of the adhesive force is seen. And so on.

[0005] As a surface protective film for improving such a point, one or a plurality of base layers made of an α-olefin polymer resin and an adhesive layer mainly containing an α-olefin copolymer are co-extruded. A laminated surface protective film has been proposed (JP-A-7-233354).

When this surface protective film is applied to various adherends, the adhesive layer does not peel off from the base material layer, has a high initial adhesive strength, and has a high adhesive strength (peel strength) after being applied. The change with time is small, the blocking force upon rewinding the film is low, the handling workability is excellent, and the production can be performed at low cost.

Although an α-olefin polymer is mentioned as a substrate layer of the surface film, most of the materials used in the examples are polyethylene. The surface protection film is used at room temperature, and in the case of protective films such as thin steel plates subjected to etching and the like, coated steel plates heated and dried, and laminated panels manufactured by hot pressing, heating to about 130 ° C. In addition, it is required that no deterioration or wrinkling or shrinkage occur. Polyethylene substrates are unsuitable for such applications. Further, when polypropylene is used for the base material layer, there is a problem that the unwinding force is high and the workability is poor, so that it cannot be used.

[0008]

DISCLOSURE OF THE INVENTION The present invention has high rigidity and high heat resistance, so that there is no wrinkling or shrinkage of the film when used at a high temperature, the blocking force at the time of rewinding is small, and the initial adhesive strength is low. An object of the present invention is to obtain a low-cost surface protective film having a high change in adhesive strength with time after application.

[0009]

The present invention relates to the following surface protective film. (1) A surface protection film in which a surface layer is laminated on one side of a substrate layer and an adhesive layer is laminated on the other side, wherein the substrate layer is made of a resin containing polypropylene as a main component, and the surface layer is made of polyethylene as a main component. The adhesive layer has a carbon number of 2 to 1
2. A surface protective film comprising a film made of an adhesive having a copolymer of α-olefin as a main component and having a rewinding force of 200 g / 25 mm or less. (2) The polypropylene forming the base material layer is a homopolymer of propylene and propylene with 2 or 4 to 1 carbon atoms.
(1) The surface protective film according to the above (1), which is at least one member selected from copolymers with α-olefins. (3) The surface protective film according to the above (1) or (2), wherein the polyethylene forming the surface layer is at least one selected from low density polyethylene, medium density polyethylene, high density polyethylene and linear low density polyethylene. . (4) The surface protective film according to any one of the above (1) to (3), wherein the adhesive layer is mainly composed of a copolymer of propylene, 1-butene and an α-olefin having 5 to 12 carbon atoms. . (5) an α-olefin copolymer in which the adhesive layer comprises propylene, 1-butene and an α-olefin having 5 to 12 carbon atoms, and (A) a copolymer comprising at least two kinds selected from ethylene, propylene and 1-butene. Polymer, (B)
Cooligomers of ethylene and α-olefin and (C)
The surface protective film according to any one of the above (1) to (4), which is a layer containing a styrene / diene copolymer or at least one copolymer selected from hydrogenated products thereof.

In the present invention, the base layer is made of a polypropylene-based resin as a low-cost material for imparting high rigidity and heat resistance to the surface protective film and reducing wrinkling and shrinkage of the film when used at high temperatures. To form Here, the resin mainly composed of polypropylene is a resin containing more than 50% by weight, preferably 60% by weight or more of polypropylene.

The polypropylene used for the base layer in the present invention is not only a homopolymer of propylene, but also propylene and a carbon atom having 2 carbon atoms.
Alternatively, a copolymer of 4 to 20, preferably 2 or 4 to 12 α-olefins of 30 mol% or less, preferably 10 mol% or less can be used. As the α-olefin for copolymerizing the propylene, ethylene, 1-butene,
Examples thereof include 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 3-methyl-1-butene, 3-methyl-1-pentene, and 4-methyl-1-pentene.

As the polypropylene, 230 ° C.
Melt flow rate (MF) measured under a load of 2.16 kg
R) is 0.5 to 30 g / 10 min, preferably 1 to 1
It is preferable to use one having 0 g / 10 min. Other resins that can be used by being blended with polypropylene include polyethylene and polybutene such as those having 2 or 4 to 10 carbon atoms.
Α-olefin polymer and other resins.
In the present invention, the above polypropylene and other resins can be used alone or in combination of two or more.

When a resin containing polypropylene as a main component as described above is used for the base layer, this resin has a high affinity for an adhesive layer described later, so that when the resin is wound around a roll, the base layer and the adhesive layer have an adhesive property. Shows sex. For this reason, it shows blocking properties when rewinding the film for use, and the rewinding force increases,
Workability deteriorates. Therefore, in the present invention, a resin mainly composed of polyethylene is laminated as a surface layer on the surface side of the base material layer.

The resin containing polyethylene as a main component used in the surface layer is not only a homopolymer of polyethylene, but also polyethylene and α-olefin having 3 to 20 carbon atoms, preferably 3 to 12 carbon atoms, in an amount of 30 mol% or less, preferably 10 mol or less. % Or less of a copolymer can be used. Examples of such a polyethylene resin include low-density polyethylene, medium-density polyethylene, high-density polyethylene, and linear low-density polyethylene.

The polyethylene used in the surface layer of the present invention has a density of 0.90 to 0.98 g / cm ³ , preferably 0.91 to 0.97 g / cm ³ , 190 ° C. and a load of 2.1.
The melt flow rate (MFR) measured at 6 kg is 0.
5 to 20 g / 10 min, preferably 1 to 10 g / 10
It is preferable to use the one with the minimum value. These polyethylenes can be used alone or in combination of two or more.

The resin used for the surface layer in the present invention is a resin containing polyethylene as a main component, and a resin containing more than 50% by weight, preferably 70% by weight or more of the above polyethylene. The surface layer is preferably composed of only one or several types of polyethylene.
20, preferably from 3 to 12 other α-olefin polymers and other resins.

In the present invention, an adhesive layer is laminated on the surface of the base material layer opposite to the surface layer. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is an α-olefin having at least two types of α-olefins selected from α-olefins having 2 to 12 carbon atoms as main monomers.
The main component is one or a mixture of two or more olefin copolymers. Examples of the above α-olefin include those described above.

The α-olefin copolymer has a crystallinity of 10% or less, preferably 5% or less by X-ray diffraction, and an MFR of 0.5 to 20 g at 190 ° C. under a load of 2.16 kg. / 10 min, preferably 1 to 10 g /
10 min is preferable. Adhesive material is such α-
It contains more than 50% by weight, preferably 60% by weight or more of an olefin copolymer as a main component, and can contain 50% by weight or less, preferably 40% by weight or less of adhesives and other components other than α-olefin. .

Among the above α-olefin copolymers,
An adhesive layer containing at least 30% by weight, preferably at least 50% by weight, of a copolymer composed of propylene, 1-butene and an α-olefin having 5 to 12 carbon atoms in the α-olefin copolymer is preferable, Especially propylene 10
-85 mol%, preferably 15-70 mol%, 1-butene 3-60 mol%, preferably 5-50 mol% and C-C12 alpha-olefin 10-85 mol%, preferably 15-70 mol% % Of the copolymer in the α-olefin copolymer is 30% by weight or more, preferably 50% by weight.
The pressure-sensitive adhesive contained above is preferable in that it has excellent pressure-sensitive adhesive properties at around normal temperature.

Examples of the pressure-sensitive adhesive comprising propylene, 1-butene and an α-olefin copolymer other than the α-olefin copolymer having 5 to 12 carbon atoms include (A) ethylene, propylene and 1-butene. At least one copolymer selected from the group consisting of at least two selected copolymers, (B) a copolymer of ethylene and an α-olefin, and (C) a styrene-diene copolymer, or a hydrogenated product thereof. can give. These may be used alone or in combination of two or more.

As a specific example of the styrene / diene copolymer (C) or a hydrogenated product thereof, styrene / ethylene / butylene / styrene block copolymer (SEB)
S), styrene-isoprene-styrene block copolymer (SIS) and styrene-ethylene-propylene-
Styrene block copolymers (SEPS) can be used, and these can be used alone or in combination of two or more.

The copolymer (A) comprising at least two kinds selected from ethylene, propylene and 1-butene includes ethylene-propylene copolymer, ethylene / 1-butene copolymer, propylene / 1-butene And copolymers. Specific examples of the copolymer (A) include those commercially available from Mitsui Petrochemical Industries, Ltd. under the trade names: Tuffmer P, Tuffmer S, Tuffmer A, Tuffmer XR, and the like.

The ethylene-α-olefin co-oligomer (B) is a low molecular weight copolymer of ethylene and α-olefin, and is a liquid at room temperature. Examples of the α-olefin include propylene, 1
-Butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1
-Hexadecene, 1-octadecene, 4-methyl-1-
Α-olefins having 3 to 20 carbon atoms, such as pentene. Among them, α-olefins having 3 to 14 carbon atoms are preferable.

The above-mentioned co-oligomer has the following formula (1)

Embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image embedded image ((CH ₂ CH ₂ ) _x (CH ₂ C (R) H) _y )) Equation (1)
In the formula, R is a group represented by C _n H _{2n + 1} (n is a positive integer), and x, y and p are positive integers.

This co-oligomer (B) usually has a number average molecular weight of 100 to 10,000, preferably 200 to 5,000.
Are used. In addition, cooligomer (B)
The ethylene content therein is usually 30 to 70 mol%, preferably 40 to 60 mol%. This cooligomer (B)
Is usually 0 to 20% by weight, preferably 0 to 10% by weight.

The SEBS is styrene-butadiene.
It is obtained by hydrogenating a styrene block copolymer. The styrene-based polymer block is converted to an average molecular weight of about 12,000 to 100,000, and the ethylene-butylene polymer block is converted to an average molecular weight of 10,000 to 30.
It contains about 0000. The content ratio of the styrene polymer block / ethylene / butylene polymer block in the SEBS is usually 5 to 50/50 to 9 by weight.
5, preferably 10-30 / 70-90.

Specific examples of the SEBS include those commercially available from Shell Chemical Company under the trade name Clayton G. The content ratio of SEBS in the adhesive layer is usually 0 to 50% by weight, preferably 0 to 45% by weight.

The SIS is a block copolymer having a styrene polymer block and an isoprene polymer block. The styrene polymer block is converted to an average molecular weight of about 12,000 to 100,000, and the isoprene polymer block is converted to an average molecular weight. And 10,000 to 300000
The degree is included. The content ratio of styrene polymer block / isoprene polymer block in the SIS is usually 5 to 50/50 to 95, preferably 10 to 10 by weight.
30/70 to 90.

Specific examples of SIS include those marketed by Shell Chemical Company under the trade name Clayton D. The content of the SIS in the adhesive layer is usually 0%.
-50% by weight, preferably 0-30% by weight. However, when SEBS and SIS are used at the same time,
The total content of SEBS and SIS in the adhesive layer is preferably 45% by weight or less. The hydrogenated version of this SIS is SEPS. As a specific example,
Examples include those commercially available from Kuraray Co., Ltd. under the trade names Septon and Hibler.

In the film of the present invention, when an adhesive comprising the above-mentioned α-olefin copolymer and copolymer (A) is used as a component of the adhesive layer, the glass transition temperature decreases and the initial adhesive strength decreases. Can be adjusted to an appropriate range, and the low-temperature adhesive property can be improved. Further, when an adhesive comprising the α-olefin-based copolymer and the co-oligomer (B) is used as a component of the adhesive layer, the glass transition temperature decreases, and the initial adhesive strength is adjusted to an appropriate range. And the viscosity can be adjusted to an appropriate range. Further, when a mixed resin composed of the above-mentioned α-olefin copolymer and SEBS, SIS and / or SEPS adhesive is used as a component of the adhesive layer, the glass transition temperature is lowered and the initial adhesive strength is adjusted to an appropriate range. In addition to the adjustment, the low-temperature adhesive property can be improved.

The pressure-sensitive adhesive layer of the film of the present invention may contain, in addition to the α-olefin-based copolymer, other various pressure-sensitive adhesives as accessory components. For example, copolymers of α-olefins and various vinyl compounds, thermoplastic elastomers represented by resins such as graft-modified products thereof, plasticizers such as liquid butyl rubber, tackifiers such as polyterpenes, etc. Is also good. In the present invention, these sub-components having an adhesive functional group and an unsaturated bond deteriorate the change over time (heating, pressurization, humidity, ultraviolet rays, etc.) of the adhesive strength after application. It is preferable to adjust the type, blending amount, and the like so as not to cause this.

In the pressure-sensitive adhesive layer of the film of the present invention, the pressure-sensitive adhesive layer contains at least two kinds of α-olefins selected from α-olefins having 2 to 12 carbon atoms as main components and has a crystallinity value by X-ray diffraction. It is 10% or less, and in order to obtain a sufficient initial adhesive strength, it is preferable that the crystallinity is 5% or less.

The base layer, the surface layer and the adhesive layer of the film of the present invention are each composed of various additives generally blended with these resins, for example, various fillers, pigments, ultraviolet absorbers, antioxidants. , A heat stabilizer, a lubricant and the like.

The surface protective film of the present invention is obtained by laminating a surface layer on one side of the substrate layer and an adhesive layer on the other side, and the thickness of the substrate layer is 10 to 300 μm, preferably 30 to 300 μm.
The thickness of the surface layer is about 1 to 100 μm, and preferably about 2 to 50 μm. The thickness of the pressure-sensitive adhesive layer is usually about 1 to 100 μm, and when the film of the present invention is produced by co-extrusion, a surface protective film having easy control of the film layer constitution and sufficient mechanical strength is required. From the viewpoint that it can be obtained, the thickness is preferably about 3 to 50 μm. The total thickness of the film of the present invention is usually 1
About 0 to 300 μm, preferably 30 to 200 μm
m.

The surface protective film of the present invention comprises the above-mentioned substrate layer,
It is manufactured by integrally laminating a surface layer and an adhesive layer. In particular, a method of producing a three-layer laminated film having a predetermined thickness by melting and heating each resin constituting the base layer, the surface layer, and the adhesive layer to form a three-layer laminated film having a predetermined thickness is highly efficient. Moreover, it is preferable in that the film of the present invention can be produced at low cost. Further, it can be carried out according to a method such as melt-extruding and laminating an adhesive layer on a base material layer.

The surface protective film of the present invention is wound into a roll as a film in which the respective layers are laminated to form a product,
Used for transportation, storage and use.
0 g / 25 mm or less, preferably 150 g / 25 mm or less.

Further, the surface protective film of the present invention has an initial adhesive strength at 23 ° C. of 20 g /
25 mm or more, with a pressure of ² kg / cm ² and 6
Even after being heated at 0 ° C. for 10 days, the film does not break, there is no adhesive residue on the stainless steel surface, and 1 kg / 25 m
It can be peeled with a strength of not more than m.

[0038]

According to the surface protective film of the present invention, the base layer is made of a resin containing polypropylene as a main component, the surface layer is made of a resin containing polyethylene as a main component, and the adhesive layer has an α of 2 to 12 carbon atoms. -Since it is mainly composed of an olefin copolymer, it has high rigidity and high heat resistance, so that wrinkles and shrinkage of the film at the time of high temperature use are small, and the blocking force at the time of rewinding is small, and the initial adhesive force is high. It is possible to obtain a low-cost surface protective film having little change over time in adhesive strength after application.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention and comparative examples will be described. The measuring method of the physical properties in each example is as follows.

Crystallinity; X-ray diffraction method (S, L. AGGA)
RWAL; Polymer Sci. 18, 17,
1955). MFR: Measured according to ASTM 1238. Unwinding force: A spring balance was attached to the tip of a 30 cm-wide film in a constant temperature room at 23 ° C., and the unwinding force was measured from the reading of the spring balance when the film was fed at a feeding speed of 5 m / min. Initial adhesive strength; measured according to JIS Z0237 1991. However, the surface finish of the stainless steel SUS304 was in the state of BA specified in JIS G4305, the polishing with abrasive paper was omitted, and the peel strength measured by a 180-degree peeling method was used as an index of the adhesive strength. Tensile modulus: measured in accordance with JIS K6781.

Example 1 A co-extrusion T-die film molding method was co-extrusion molded under the following conditions so that the following surface layer, base material layer and adhesive layer were laminated in this order to produce a surface protective film. Table 1 shows the results of measuring the unwinding force, initial adhesive strength and tensile modulus of the obtained surface protective film.

Surface layer; high density polyethylene (density;
95 g / cm ³ , MFR (190 ° C., 2.16 kg)
1.1 g / 10 min), 70 parts by weight of low-density polyethylene (density: 0.92 g / cm ³ , MFR (190 ° C.,
2.16 kg) 9.5 g / 10 min) 30 parts by weight (10 μm thick). Base layer: propylene homopolymer (MFR (230 ° C.,
2.16 kg) 6.5 g / 10 min) polypropylene resin (thickness 38 to 40 μm). Adhesive layer; propylene / 1-butene / 4-methyl-1-pentene copolymer (propylene; 50 mol%, 1-butene; 20 mol%, 4-methyl-1-pentene; 30 mol%, crystallinity 0) 0.5%, MFR (190 ° C., 2.16 k
g) 4.0 g / 10 min) 60 parts by weight, ethylene / propylene copolymer (ethylene; 80 mol%, propylene; 20 mol%, MFR (190 ° C., 2.16 kg)
1.0 g / 10 min, density; 0.87 g / cm ³ ) 25 parts by weight, SEPS (manufactured by Kuraray Co., Ltd., trade name Septon 20)
63) Adhesive containing 15 parts by weight (thickness: 10 to 12 µ)
m).

Molding conditions Melting temperature: Surface layer = 230 ° C. Base layer = 230 ° C. Adhesive layer = 180 ° C. Coextrusion temperature: 230 ° C.

Example 2 In Example 1, the surface layer and the base material layer were changed as follows. Table 1 shows the results. Surface layer: high-density polyethylene resin (10 μm thick) used in Example 1 for the surface layer. Substrate layer; a resin composition comprising 70 parts by weight of polypropylene made of a propylene / ethylene random copolymer having an ethylene content of 3 mol% and 30 parts by weight of low-density polyethylene used for the surface layer in Example 1 (thickness: 38) ４０40 μm).

Comparative Example 1 In Example 1, the surface layer and the base material layer were changed as follows. Table 1 shows the results. Surface layer: polypropylene resin (10 μm thickness) used for the base material layer in Example 1. Base material layer: polypropylene resin (thickness: 38 to 40 μm) used for the base material layer in Example 1.

Comparative Example 2 In Example 1, the surface layer and the base material layer were changed as follows. Table 1 shows the results. Surface layer: polypropylene resin (10 μm thickness) used for the base material layer in Example 1. Substrate layer: A resin composition (thickness: 38 to 40 μm) comprising 70 parts by weight of polypropylene and 30 parts by weight of low-density polyethylene used as the substrate layer in Example 2.

[0047]

[Table 1]

From the results shown in Table 1, in Examples 1 and 2, the unwinding force was small, the initial adhesive strength was high, the tensile modulus was high and the rigidity was high, and Comparative Examples 1 and 2 in which polypropylene was used for the surface layer were used.
Increases the rewinding force.

Claims (5)

[Claims] 1. A surface protection film having a surface layer on one side of a substrate layer and an adhesive layer on the other side, wherein the substrate layer is made of a resin containing polypropylene as a main component, and the surface layer is mainly made of polyethylene. The unwinding force of a film composed of a resin as a component and an adhesive layer whose adhesive layer is mainly composed of an α-olefin copolymer having 2 to 12 carbon atoms is 200.
g / 25 mm or less. 2. The polypropylene which forms the base material layer is selected from a propylene homopolymer and a copolymer of propylene and an α-olefin having 2 or 4 to 10 carbon atoms.
The surface protective film according to claim 1, which is at least one kind. 3. The surface protective film according to claim 1, wherein the polyethylene forming the surface layer is at least one selected from low density polyethylene, medium density polyethylene, high density polyethylene and linear low density polyethylene. 4. The surface protective film according to claim 1, wherein the pressure-sensitive adhesive layer is mainly composed of a copolymer of propylene, 1-butene and an α-olefin having 5 to 12 carbon atoms. 5. An α-olefin copolymer in which the adhesive layer comprises propylene, 1-butene and an α-olefin having 5 to 12 carbon atoms, and (A) ethylene, propylene and 1-
A copolymer consisting of at least two kinds selected from butenes,
5. A layer comprising (B) a copolymer of ethylene and an α-olefin and (C) at least one copolymer selected from a styrene-diene copolymer or a hydrogenated product thereof. The surface protective film according to any one of the above.