JP2021084331A - Surface protection film - Google Patents

Abstract

To provide a surface protection film that has well-balanced performances including flexibility, stress relaxation, transparency and scratch resistance, and allows reduction in the amount of use of a thermoplastic polyurethane resin layer.SOLUTION: A surface protection film 10 has a thermoplastic polyurethane resin layer (A), an ionomer resin layer (B) containing an ionomer (B1) of an ethylene-unsaturated carboxylic acid-unsaturated carboxylate ester copolymer, and an adhesive resin layer (C) that is provided between the thermoplastic polyurethane resin layer (A) and ionomer resin layer (B) and contains a polymer (C1) obtained by the graft co-polymerization of an olefinic compound with an organic acid.SELECTED DRAWING: Figure 1

Description

The present invention relates to a surface protective film.

As a film for protecting the surface of the vehicle body, a surface protection film using a thermoplastic polyolefin resin or polyurethane resin is generally used (for example, Patent Document 1).

Examples of the technique related to the surface protective film include those described in Patent Document 2.
Patent Document 2 includes a base material of an olefin resin having an adhesive function and a top coat layer of a urethane resin supported by the base material, which is a film used for the exterior of an automobile. Described is an automobile exterior film characterized in that it is attached to an automobile exterior component via a base material.

Japanese Unexamined Patent Publication No. 9-277379 Japanese Unexamined Patent Publication No. 2003-225977

Since the thermoplastic polyurethane resin is an expensive resin, it may be used only in a part of the vehicle body due to cost restrictions. There is a demand for a surface protective film capable of reducing the amount of the thermoplastic polyurethane resin used while maintaining the excellent properties such as flexibility, mechanical strength, and transparency of the thermoplastic polyurethane resin film.
According to the studies by the present inventors, a surface protective film containing a conventional olefin resin base material having an adhesive function and a urethane resin top coat layer supported by the base material has weather resistance and scratch resistance. However, it was revealed that it has the following problems.
The surface protective film is adhered to the surface of the vehicle body using an adhesive while being stretched so as to follow the shape of the vehicle body. However, if the film is hard and difficult to stretch, or if the stretched state is not maintained, the film may peel off over time. That is, according to the study by the present inventors, it is clear that when the surface protective film is stretched and bonded to the vehicle body, the bonded film is likely to be peeled off unless the stress applied to the surface protective film is relaxed. became. For this reason, a plurality of skilled workers are required for the construction work, which is difficult in efficiency and economy.

The present invention has been made in view of the above circumstances, and provides a surface protective film having an excellent balance of flexibility, stress relaxation, transparency and scratch resistance, and capable of reducing the amount of the thermoplastic polyurethane resin layer used. To do.

The present inventors have made extensive studies to achieve the above problems. As a result, by laminating a specific ionomer resin layer on the thermoplastic polyurethane resin layer via a specific adhesive resin layer, flexibility and stress relaxation property can be reduced while reducing the amount of the thermoplastic polyurethane resin layer used. , And have found that the performance balance of transparency and scratch resistance can be improved, and have reached the present invention.

That is, according to the present invention, the following surface protective film is provided.

[1]
Thermoplastic polyurethane resin layer (A) and
An ionomer resin layer (B) containing an ionomer (B1) of an ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer,
An adhesive resin layer (C) provided between the thermoplastic polyurethane resin layer (A) and the ionomer resin layer (B) and containing a polymer (C1) obtained by graft-copolymerizing an organic acid with an olefin compound. When,
Surface protective film with.
[2]
In the surface protective film according to the above [1],
In the ionomer (B1) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer, the content of the structural unit derived from the unsaturated carboxylic acid with respect to all the structural units is 1% by mass or more and 20% by mass or less. Surface protective film.
[3]
In the surface protective film according to the above [1] or [2],
According to JIS K7210: 1999, the melt mass flow rate (MFR) of the above ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer ionomer (B1) measured under the condition of 190 ° C. and 2160 g load is 0. A surface protective film of 0.01 g / 10 minutes or more and 50 g / 10 minutes or less.
[4]
In the surface protective film according to any one of the above [1] to [3],
A surface protective film in which the organic acid contains maleic anhydride.
[5]
In the surface protective film according to any one of the above [1] to [4],
The polymer (C1) obtained by graft-copolymerizing an organic acid with the above-mentioned olefin compound is a maleic anhydride graft modified product obtained by graft-copolymerizing maleic anhydride with polyethylene, and maleic anhydride with an ethylene / α-olefin copolymer. A surface protective film containing at least one selected from a maleic anhydride graft modified product obtained by graft-copolymerizing maleic anhydride and a maleic anhydride graft modified product obtained by graft-copolymerizing maleic anhydride with an ethylene (meth) acrylate copolymer. ..
[6]
In the surface protective film according to any one of the above [1] to [5],
A surface protective film having a haze of 5% or less measured according to JIS K7136: 2000.
[7]
In the surface protective film according to any one of the above [1] to [6],
A surface protective film having a total light transmittance of 80% or more measured in accordance with JIS K7136: 2000.
[8]
In the surface protective film according to any one of the above [1] to [7],
A surface protective film further comprising an adhesive layer (D) on either one of the outermost layers.
[9]
In the surface protective film according to the above [8],
The pressure-sensitive adhesive layer (D) is composed of at least one type of pressure-sensitive adhesive selected from urethane-based pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, styrene-based pressure-sensitive adhesives, olefin-based pressure-sensitive adhesives, and acrylic-based pressure-sensitive adhesives. Surface protective film.
[10]
In the surface protective film according to any one of the above [1] to [9],
A surface protection film that is a paint protection film.

According to the present invention, it is possible to provide a surface protective film having an excellent balance of flexibility, stress relaxation property, transparency and scratch resistance, and capable of reducing the amount of the thermoplastic polyurethane resin layer used.

It is sectional drawing which shows typically an example of the structure of the surface protection film of embodiment which concerns on this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Unless otherwise specified, "X to Y" in the numerical range represents X or more and Y or less. Further, in the present embodiment, "(meth) acrylic" means "acrylic, methacrylic" or both acrylic and methacrylic.

1. 1. Surface Protective Film FIG. 1 is a cross-sectional view schematically showing an example of the structure of the surface protective film 10 according to the embodiment of the present invention.
The surface protective film 10 according to the present embodiment is an ionomer of a thermoplastic polyurethane resin layer (A) (hereinafter, also referred to as a resin layer (A)) and an ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer. An olefin-based compound provided between an ionomer resin layer (B) containing (B1) (hereinafter, also referred to as a resin layer (B)), a thermoplastic polyurethane resin layer (A), and an ionomer resin layer (B). It is provided with an adhesive resin layer (C) (hereinafter, also referred to as a resin layer (C)) containing a polymer (C1) obtained by graft-copolymerizing an organic acid.

According to the surface protective film 10 according to the present embodiment, by having the thermoplastic polyurethane resin layer (A) and the ionomer resin layer (B), the amount of the thermoplastic polyurethane resin layer (A) used can be reduced. It is also possible to impart the excellent stress relaxation property and scratch resistance of the ionomer resin layer (B) while maintaining the properties such as excellent flexibility, mechanical strength, and transparency. Further, the thermoplastic polyurethane resin layer (A) and the ionomer resin layer (B) are laminated via the adhesive resin layer (C) to form the thermoplastic polyurethane resin layer (A) and the ionomer resin layer (B). The interlayer adhesiveness of the above can be improved.
From the above, the surface protective film 10 according to the present embodiment is excellent in the performance balance of flexibility, stress relaxation property, transparency and scratch resistance, and the amount of the thermoplastic polyurethane resin layer (A) used can be reduced. it can.

The thermoplastic polyurethane resin layer (A) is preferably composed of a single layer containing the thermoplastic polyurethane resin as a main component, but a plurality of layers having different types and contents of the thermoplastic polyurethane resin. It may be composed of layers.
The "main component" means that the thermoplastic polyurethane resin is contained in the thermoplastic polyurethane resin layer (A) in an amount of 50% by mass or more.

Further, the ionomer resin layer (B) is preferably composed of a single layer containing the ionomer resin as a main component, but is composed of a plurality of layers having different types and contents of the ionomer resin. May be.
The "main component" means that the ionomer resin is contained in the ionomer resin layer (B) in an amount of 50% by mass or more.

In the present embodiment, the overall thickness of the surface protective film 10 is preferably 10 μm or more and 1000 μm or less from the viewpoint of performance balance of stress relaxation property, flexibility, mechanical strength, transparency, interlayer adhesiveness, and scratch resistance. , More preferably 30 μm or more and 500 μm or less.

In the surface protective film 10 according to the present embodiment, the thickness of the resin layer (A) is preferably from the viewpoint of performance balance of stress relaxation property, flexibility, mechanical strength, transparency, interlayer adhesiveness, and scratch resistance. The thickness of the resin layer (B) is preferably 3 μm or more and 400 μm or less, more preferably 10 μm or more and 200 μm or less, and the thickness of the resin layer (C) is preferably 3 μm or more and 400 μm or less, more preferably 10 μm or more and 200 μm or less. It is 3 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less.

In the surface protective film 10 according to the present embodiment, the haze measured in accordance with JIS K7136: 2000 is preferably 5% or less, more preferably 4% or less, and preferably 3% or less. Especially preferable. The lower limit of the haze of the surface protective film 10 is not particularly limited, but is, for example, 0% or more.
As a result, the transparency of the surface protective film 10 can be further improved.

In the surface protective film 10 according to the present embodiment, the total light transmittance measured in accordance with JIS K7136: 2000 is preferably 80% or more, more preferably 85% or more, and 90% or more. It is particularly preferable to have. The upper limit of the total light transmittance of the surface protective film 10 is not particularly limited, but is, for example, 100% or less.
As a result, the transparency of the surface protective film 10 can be further improved.

The surface protective film 10 according to the present embodiment is, for example, a paint protection film (PPF) for protecting the vehicle body of an automobile, an aircraft, a ship, a motorcycle, etc. from dirt, scratches, etc .; a light guide plate, a polarizing plate, a retardation plate, etc. Protective film for electronic parts to protect the surface of electronic parts; Protective film to protect the surface of synthetic resin plates, decorative plates, metal plates, etc .; windows, building materials, digital signage, packaging, office supplies, medical care It can be suitably used as a protective film for protecting the surface of equipment and the like. Among these, it can be particularly preferably used as a paint protection film.

When the surface protective film 10 according to the present embodiment is used, the resin layer (A) surface may be on the protective object side, or the resin layer (B) surface may be on the protective object side.

Hereinafter, each layer constituting the surface protective film 10 will be described.

<Thermoplastic polyurethane resin layer (A)>
The thermoplastic polyurethane resin layer (A) contains a thermoplastic polyurethane resin as a main component.
The content of the thermoplastic polyurethane resin in the resin layer (A) according to the present embodiment is preferably 50% by mass or more, more preferably 60% by mass or more, assuming that the entire resin layer (A) is 100% by mass. It is more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. When the content of the thermoplastic polyurethane resin in the resin layer (A) according to the present embodiment is at least the above lower limit value, the performance balance such as transparency, flexibility, and mechanical strength of the surface protective film 10 is further improved. Can be good.
The upper limit of the content of the thermoplastic polyurethane resin in the resin layer (A) according to the present embodiment is not particularly limited, but is, for example, 100% by mass or less.

The thermoplastic polyurethane resin constituting the resin layer (A) is not particularly limited, and known ones can be used. For example, block copolymers having polyurethane as a hard segment and polyether; polyester such as adipate-based polyester and caprolactone-based polyester; polycarbonate and the like can be mentioned as soft segments.

The thermoplastic polyurethane resin constituting the resin layer (A) is more specifically a resin formed of a bifunctional polyol, a diisocyanate, and a chain extender and containing a urethane group in the molecular structure. Examples thereof include those having thermoplasticity.

The thermoplastic polyurethane resin may be a block copolymer containing a hard segment formed by a reaction between a chain extender and a diisocyanate and a soft segment formed by a reaction between a bifunctional polyol and a diisocyanate. preferable.

Further, the thermoplastic polyurethane resin is classified according to the type of the bifunctional polyol or the like as a raw material, and examples thereof include a polyether-based thermoplastic polyurethane resin, a polyester-based thermoplastic polyurethane resin, and a polycarbonate-based thermoplastic polyurethane resin. One type of these thermoplastic polyurethane resins may be used alone, or two or more types may be used in combination.

The bifunctional polyol is not particularly limited, and examples thereof include polyether-based polyols, polyester-based polyols, and polycarbonate-based polyols.
One type of these bifunctional polyols may be used alone, or two or more types may be used in combination.

Examples of the polyether polyol include polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol and the like. These polyether polyols may be polycondensed with 1,2-ethanediol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, etc., or ethylene oxide, propylene oxide, tetrahydrofuran, etc. It can be obtained by ring-opening polymerization of the cyclic ether of.
Examples of the polyester-based polyol include polyester polyols obtained by polycondensation of dibasic acids such as adipic acid, sebacic acid and terephthalic acid with low molecular weight polyols, polycaprolactone glycol and the like.
Examples of the polycarbonate-based polyol include a polycarbonate polyol obtained by polycondensing a dialkyl carbonate such as dimethyl carbonate and diethyl carbonate, phosgene, chloroformate, diallyl carbonate, alkylene carbonate and the like with a low molecular weight polyol. ..

Examples of the diisocyanate include toluene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), polypeptide MDI, tolylene diisocyanate, p-phenylenedi isocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, norbornene diisocyanate hydrogenated MDI and the like. Can be mentioned.

Examples of the chain extender include polyoxyethylene glycol, polyoxypropylene glycol, 1,4-butanediol, trimethylolpropane, bishydroxyethoxybenzene and the like.

The resin layer (A) according to the present embodiment may contain various additives as long as the object of the present invention is not impaired. The various additives are not particularly limited, but for example, a plastic agent, an antioxidant, an ultraviolet absorber, a wavelength converter, an antioxidant, a surfactant, a colorant, a light stabilizer, a foaming agent, a lubricant, and a crystal nucleus. Agents, crystallization accelerators, crystallization retardants, catalyst deactivators, heat ray absorbers, heat ray reflectors, heat dissipation agents, thermoplastic resins other than ionomer resins, thermosetting resins, inorganic fillers, organic fillers, resistance to Impact improver, slip agent, cross-linking agent, cross-linking aid, tackifier, silane coupling agent, processing aid, mold release agent, hydrolysis inhibitor, heat stabilizer, anti-blocking agent, anti-fog agent, difficult Examples thereof include flame retardants, flame retardants, photodiffusing agents, antibacterial agents, anti-crosslinking agents, dispersants and other resins. Various additives may be used alone or in combination of two or more.

<Ionomer resin layer (B)>
The ionomer resin layer (B) contains an ionomer resin as a main component.
As the ionomer resin, an ionomer (B1), which is an ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer, is preferable.
The ionomer (B1) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer according to the present embodiment contains ethylene, at least one unsaturated carboxylic acid, and at least one unsaturated carboxylic acid ester. It is an ionomer of a polymer obtained by copolymerizing with and, and is a resin obtained by neutralizing at least a part of carboxyl groups with a metal ion with respect to an ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer. Examples of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer include a copolymer containing ethylene, an unsaturated carboxylic acid, and an unsaturated carboxylic acid ester.
The ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer may be used alone, or two or more types of ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer may be used in combination. You may.

Examples of the unsaturated carboxylic acid constituting the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer according to the present embodiment include acrylic acid, methacrylic acid, etaclilic acid, itaconic acid, itaconic anhydride, and fumal. Examples thereof include unsaturated carboxylic acids having 4 to 8 carbon atoms such as acids, crotonic acid, maleic acid, and maleic anhydride. These unsaturated carboxylic acids may be used alone or in combination of two or more. Among these, it is preferable to contain at least one selected from acrylic acid and methacrylic acid.

As the unsaturated carboxylic acid ester constituting the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer according to the present embodiment, an unsaturated carboxylic acid alkyl ester is preferable. The number of carbon atoms in the alkyl moiety of the alkyl ester is preferably 1 to 12, more preferably 1 to 8, and even more preferably 1 to 4. Examples of the alkyl moiety include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, secondary butyl, 2-ethylhexyl, isooctyl and the like. Specific examples of unsaturated carboxylic acid alkyl esters include methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, and methacrylic acid. Examples thereof include (meth) acrylic acid alkyl esters such as isobutyl, n-butyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, dimethyl maleate, and diethyl maleate.

When the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer according to the present embodiment is a quaternary or more multidimensional copolymer, a monomer forming a multidimensional copolymer (fourth copolymerization component). May include. Examples of the fourth copolymerization component include unsaturated hydrocarbons (eg, propylene, butene, 1,3-butadiene, penten, 1,3-pentadiene, 1-hexene, etc.), vinyl esters (eg, vinyl acetate, etc.). (Vinyl propionate, etc.), oxides such as vinyl sulfuric acid and vinyl nitrate, halogen compounds (for example, vinyl chloride, vinyl fluoride, etc.), vinyl group-containing primary and secondary amine compounds, carbon monoxide, sulfur dioxide, etc. can be mentioned. ..

The form of the copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer, and may be any of a ternary copolymer and a quaternary or more multidimensional copolymer. Among them, a ternary random copolymer or a graft copolymer of a ternary random copolymer is preferable, and a ternary random copolymer is more preferable, because it is industrially available.

Specific examples of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer according to the present embodiment include ternary copolymers such as ethylene / methacrylic acid / acrylic acid butyl ester copolymers.

In the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer according to the present embodiment, the total amount of the constituent units constituting the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer is 100% by mass. The content ratio of the structural unit derived from the unsaturated carboxylic acid is preferably 1% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, and further preferably 1% by mass or more. It is 12% by mass or less. When the structural unit derived from the unsaturated carboxylic acid is at least the above lower limit value, the transparency, flexibility, and the like of the surface protective film 10 can be improved. Further, when the structural unit derived from the unsaturated carboxylic acid is not more than the above upper limit value, the mechanical strength, processability, etc. of the surface protective film 10 can be improved.

In the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer according to the present embodiment, the total amount of the constituent units constituting the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer is 100 mass by mass. When% is taken, the content ratio of the structural unit derived from the unsaturated carboxylic acid ester is preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 25% by mass or less, and particularly preferably 3% by mass. % Or more and 20% by mass or less. When the content ratio of the structural unit derived from the unsaturated carboxylic acid ester is at least the above lower limit value, the flexibility of the surface protective film 10 can be improved. Further, when the content ratio of the structural unit derived from the unsaturated carboxylic acid ester is not more than the above upper limit value, the processability of the surface protective film 10 can be improved.

Examples of the metal ion constituting the ionomer (B1) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer according to the present embodiment include lithium ion, potassium ion, sodium ion, silver ion and copper ion. Monovalent metal ions such as calcium ion, magnesium ion, zinc ion, aluminum ion, barium ion, beryllium ion, strontium ion, copper ion, mercury ion, tin ion, lead ion, iron ion, cobalt ion and nickel ion, etc. Examples include polyvalent metal ions.
Among these, it is preferable to contain one or more selected from lithium ion, potassium ion, sodium ion, calcium ion, magnesium ion, zinc ion, aluminum ion, and barium ion, and potassium ion, sodium ion, zinc ion. And at least one selected from magnesium ions is more preferred, and at least one selected from sodium and zinc ions is particularly preferred.

The degree of neutralization of the ionomer (B1) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer according to the present embodiment is not particularly limited, but the flexibility, adhesiveness, and mechanical strength of the surface protective film 10 are not particularly limited. From the viewpoint of improving processability and the like, 5 to 95% is preferable, 10 to 90% is more preferable, 15 to 85% is further preferable, and 20 to 80% or less is particularly preferable.
Here, the degree of neutralization of the ionomer (B1) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer is contained in the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer. Refers to the proportion (%) of carboxyl groups neutralized by metal ions in the total carboxyl groups.

The method for producing an ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer constituting the ionomer (B1) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer according to the present embodiment is particularly applicable. It is not limited and can be produced by a known method. For example, it can be obtained by radical copolymerizing each polymerization component under high temperature and high pressure. Further, the ionomer (B1) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer according to the present embodiment contains an ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer and a metal compound. It can be obtained by reacting. Further, as the ionomer (B1) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer, a commercially available one may be used. Examples of commercially available products include the Hymilan (registered trademark) series manufactured by Mitsui Dow Polychemical Co., Ltd.

In this embodiment, the melt mass flow rate of an ionomer (B1) of an ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer measured at 190 ° C. and a load of 2160 g according to JIS K7210: 1999. The (MFR) is preferably 0.01 g / 10 minutes or more and 50 g / 10 minutes or less, more preferably 0.1 g / 10 minutes or more and 30 g / 10 minutes or less, and 0.1 g / 10 minutes or more and 10 g. It is particularly preferable that it is / 10 minutes or less. When the MFR is at least the above lower limit value, the processability of the ionomer (B1) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester-based copolymer can be further improved. When the MFR is not more than the above upper limit value, the heat resistance and mechanical strength of the obtained surface protective film 10 can be further improved.

The content of the ionomer resin in the ionomer resin layer (B) according to the present embodiment is preferably 50% by mass or more, more preferably 60% by mass or more, when the entire ionomer resin layer (B) is 100% by mass. , More preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. When the content of the ionomer resin in the ionomer resin layer (B) according to the present embodiment is equal to or higher than the above lower limit value, the performance balance of the surface protective film 10 such as workability, interlayer adhesiveness, transparency, and mechanical strength is balanced. Can be made even better.
The upper limit of the content of the ionomer resin in the ionomer resin layer (B) according to the present embodiment is not particularly limited, but is, for example, 100% by mass or less.

The resin layer (B) according to the present embodiment may contain various additives as long as the object of the present invention is not impaired. The various additives are not particularly limited, but for example, a plastic agent, an antioxidant, an ultraviolet absorber, a wavelength converter, an antioxidant, a surfactant, a colorant, a light stabilizer, a foaming agent, a lubricant, and a crystal nucleus. Agents, crystallization accelerators, crystallization retardants, catalyst deactivators, heat ray absorbers, heat ray reflectors, heat dissipation agents, thermoplastic resins other than ionomer resins, thermosetting resins, inorganic fillers, organic fillers, resistance to Impact improver, slip agent, cross-linking agent, cross-linking aid, tackifier, silane coupling agent, processing aid, mold release agent, hydrolysis inhibitor, heat stabilizer, anti-blocking agent, anti-fog agent, difficult Examples thereof include flame retardants, flame retardants, photodiffusing agents, antibacterial agents, anti-crosslinking agents, dispersants and other resins. Various additives may be used alone or in combination of two or more.

<Adhesive resin layer (C)>
The resin layer (C) according to the present embodiment contains at least one kind of polymer (C1) obtained by graft-copolymerizing an organic acid with an olefin compound. By arranging the resin layer (C) between the resin layer (A) and the resin layer (B), the adhesive strength between the resin layer (A) and the resin layer (B) is enhanced. Further, the resin layer (C) may be formed by using a polymer other than the polymer (C1) or other components such as additives.

The content of the polymer (C1) obtained by graft-copolymerizing an organic acid with the olefin compound in the resin layer (C) according to the present embodiment is preferably 100% by mass when the entire resin layer (C) is 100% by mass. Is 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more. When the content of the polymer (C1) obtained by graft-copolymerizing an organic acid with the olefin compound in the resin layer (C) according to the present embodiment is at least the above lower limit, the interlayer adhesiveness of the surface protective film 10 is increased. Can be made even better.
The upper limit of the content of the polymer (C1) obtained by graft-copolymerizing an organic acid with the olefin compound in the resin layer (C) according to the present embodiment is not particularly limited, but is, for example, 100% by mass or less.

Examples of the olefin compound include polyethylene, polypropylene, a copolymer of ethylene and α-olefin, a copolymer of propylene and α-olefin, a copolymer of ethylene and ethyl acrylate, and a copolymer of methacrylate. A combination of these may be used.

Examples of the organic acid include maleic anhydride, acrylic acid and the like, and maleic anhydride is preferable.

Examples of the polymer (C1) obtained by graft-copolymerizing an organic acid with an olefin compound include a maleic anhydride graft modified product obtained by graft-copolymerizing maleic anhydride with polyethylene, and graft-copolymerizing maleic anhydride with polypropylene. Maleic anhydride graft modified product, maleic anhydride graft copolymer obtained by graft-copolymerizing maleic anhydride with an ethylene / α-olefin copolymer, and a propylene / α-olefin copolymer graft-copolymerized with maleic anhydride. Maleic anhydride is grafted onto an ethylene (meth) acrylate copolymer represented by a maleic anhydride graft modified product obtained by graft-copolymerizing maleic anhydride on an ethylene / ethyl acrylate copolymer modified product. Examples thereof include copolymerized maleic anhydride graft modified products.
Among these, maleic anhydride graft-modified product obtained by graft-copolymerizing maleic anhydride with polyethylene, maleic anhydride graft-modified product obtained by graft-copolymerizing maleic anhydride with an ethylene / α-olefin copolymer, and ethylene ( A maleic anhydride graft modified product obtained by graft-copolymerizing maleic anhydride with a meth) acrylate copolymer is preferable.

A commercially available product may be used as the polymer (C1) obtained by graft-copolymerizing an organic acid with an olefin compound, and as an example of the commercially available product, AR-2011 (ethylene / ethyl acrylate copolymer and anhydrous maleine) may be used. Maleic anhydride graft modified product obtained by graft copolymerizing an acid, manufactured by Mitsui Dow Polychemical Co., Ltd., Toughmer M series (maleic anhydride graft modified product obtained by graft copolymerizing maleic anhydride on an ethylene / α-olefin copolymer. (For example, Toughmer MA8510, MH7010, MH7020, etc., manufactured by Mitsui Chemicals, Inc.), Admer series (maleic anhydride graft-modified product obtained by graft-copolymerizing maleic anhydride with polyolefin (polyethylene, polypropylene, etc.); eg, Admer NF528, NF548, NF558, etc., manufactured by Mitsui Chemicals, Inc.), and the like.

<Adhesive layer (D)>
It is preferable that the surface protective film 10 according to the present embodiment further includes an adhesive layer (D) on one of the outermost layers.
The pressure-sensitive adhesive layer (D) can be formed, for example, by applying a pressure-sensitive adhesive to the resin layer (A) side or the resin layer (B) side. It may be formed directly on the surface of the resin layer, or may be laminated with the resin layer via another layer.
The pressure-sensitive adhesive used for the pressure-sensitive adhesive layer is not particularly limited, and examples thereof include acrylic pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, styrene-based pressure-sensitive adhesives, and olefin-based pressure-sensitive adhesives. Acrylic adhesives are preferable because they are excellent in heat resistance and weather resistance.
The layer thickness of the pressure-sensitive adhesive layer (D) can be, for example, 3 to 100 μm, preferably 5 to 50 μm, and more preferably 10 to 30 μm.
The layer in contact with the pressure-sensitive adhesive layer (D) can be subjected to surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of an undercoat agent.

<Other layers>
Further, the surface protective film 10 according to the present embodiment may be composed of only the resin layer (A), the resin layer (B) and the resin layer (C), or may be composed of only the resin layer (A), or the pressure-sensitive adhesive layer (D) if necessary. From the viewpoint of imparting various functions to the surface protective film 10, other than the resin layer (A), the resin layer (B), the resin layer (C), and the pressure-sensitive adhesive layer (D). It may have a layer (hereinafter, also referred to as another layer). Examples of other layers include a base material layer, an inorganic substance layer, a gas barrier layer, an antistatic layer, a hard coat layer, an adhesive layer, an antireflection layer, an antifouling layer, a sealant layer, an undercoat layer, an adhesive layer and the like. Can be done. The other layers may have one layer alone, or may have two or more layers in combination.

2. Method for Manufacturing Surface Protective Film In the method for manufacturing the surface protective film 10 according to the present embodiment, a commonly used method for forming a multilayer film can be applied. For example, it can be carried out by a known method using a multi-layer T-die extruder, a multi-layer inflation molding machine, or the like.
For example, for forming a resin composition for forming a thermoplastic polyurethane resin layer (A), an adhesive resin composition for forming an adhesive resin layer (C), and an ionomer resin layer (B). The resin composition can be obtained by supplying the resin composition from the hoppers of the main extruder and the slave extruder of the multi-layer T-die extruder and coextruding the resin composition from the tip of the T die into a sheet shape.
When forming the pressure-sensitive adhesive layer (D), a method of extruding the pressure-sensitive adhesive on one of the obtained multilayer films with a T-die extruder or co-extruding all the components to form a sheet. You can also.

Although the embodiments of the present invention have been described above with reference to the drawings, these are examples of the present invention, and various configurations other than the above can be adopted.

Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples.

The details of the components used to prepare the surface protective film are as follows.

<Thermoplastic polyurethane resin>
TPU1: Polycarbonate-based thermoplastic polyurethane resin (manufactured by Tosoh Corporation, Miractran XN2004S, hardness 96A, softening point: 102 ° C.)

<Ionomer resin>
(Ionomer of ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer)
Ionomer 1: Zn neutralized product of ethylene / methacrylic acid / acrylate butyl ester copolymer (ethylene unit content: 80% by mass, methacrylic acid unit content: 10% by mass, acrylic acid butyl ester unit content) : 10% by mass, Zn neutralization degree: 70%, MFR (JIS K7210: 1999, 190 ° C., 2160 g load): 1.0 g / 10 minutes)
Ionomer 2: Zn neutralized product of ethylene / methacrylic acid / acrylate butyl ester copolymer (ethylene unit content: 75% by mass, methacrylic acid unit content: 8% by mass, acrylic acid butyl ester unit content) : 17% by mass, Zn neutralization degree: 65%, MFR (JIS K7210: 1999, 190 ° C., 2160 g load): 2.5 g / 10 minutes)

(Ionomer of ethylene / unsaturated carboxylic acid copolymer)
Ionomer 3: Zn neutralized product of ethylene / methacrylic acid copolymer (ethylene unit content: 90% by mass, methacrylic acid unit content: 10% by mass, Zn neutralization degree: 73%, MFR (JIS K7210:) 1999, 190 ° C, 2160 g load): 1.0 g / 10 minutes)
Ionomer 4: Zn neutralized product of ethylene / methacrylic acid copolymer (ethylene unit content: 88% by mass, methacrylic acid unit content: 12% by mass, Zn neutralization degree: 36%, MFR (JIS K7210:) 1999, 190 ° C, 2160 g load): 1.5 g / 10 minutes)

<Polymer obtained by graft-copolymerizing an organic acid with an olefin compound>
AD1: Admer PF508 (maleic anhydride graft modified product obtained by graft-copolymerizing maleic anhydride with polyethylene, manufactured by Mitsui Chemicals, Inc.)

[Example 1]
Using TPU1 as the outer layer 1, AD1 as the intermediate layer, and ionomer 1 as the outer layer 2, the molding temperature of the outer layer 1 was set to 200 ° C. under the condition of a processing speed of 11 m / min using a cast molding machine of 40 mmφ3 type 3 layer. The molding temperature of the intermediate layer was 230 ° C., the molding temperature of the outer layer 2 was 240 ° C., and the thickness ratio was set to outer layer 1 / intermediate layer / outer layer 2 = 70 μm / 20 μm / 60 μm to prepare a laminated film having a total thickness of 150 μm. We evaluated each of them. The results obtained are shown in Table 1.

[Example 2]
Using TPU1 as the outer layer 1, AD1 as the intermediate layer, and ionomer 2 as the outer layer 2, the molding temperature of the outer layer 1 was set to 200 ° C. under the condition of a processing speed of 12 m / min using a cast molding machine of 40 mmφ3 type 3 layer. The molding temperature of the intermediate layer was 230 ° C., the molding temperature of the outer layer 2 was 230 ° C., and the thickness ratio was set to outer layer 1 / intermediate layer / outer layer 2 = 70 μm / 20 μm / 60 μm to prepare a laminated film having a total thickness of 150 μm. We evaluated each of them. The results obtained are shown in Table 1.

[Comparative Example 1]
Using TPU1 as the outer layer 1, AD1 as the intermediate layer, and ionomer 3 as the outer layer 2, the molding temperature of the outer layer 1 was set to 200 ° C. under the condition of a processing speed of 10 m / min using a cast molding machine of 40 mmφ3 type 3 layer. The molding temperature of the intermediate layer was 230 ° C., the molding temperature of the outer layer 2 was 240 ° C., and the thickness ratio was set to outer layer 1 / intermediate layer / outer layer 2 = 70 μm / 20 μm / 60 μm to prepare a laminated film having a total thickness of 150 μm. We evaluated each of them. The results obtained are shown in Table 1.

[Comparative Example 2]
Using TPU1 as the outer layer 1, AD1 as the intermediate layer, and ionomer 4 as the outer layer 2, the molding temperature of the outer layer 1 was set to 200 ° C. under the condition of a processing speed of 11 m / min using a cast molding machine of 40 mmφ3 type 3 layer. The molding temperature of the intermediate layer was 230 ° C., the molding temperature of the outer layer 2 was 240 ° C., and the thickness ratio was set to outer layer 1 / intermediate layer / outer layer 2 = 70 μm / 20 μm / 60 μm to prepare a laminated film having a total thickness of 150 μm. We evaluated each of them. The results obtained are shown in Table 1.

<Evaluation>
(1) Measurement of modulus strength With respect to the obtained laminated film, using an autograph (manufactured by Shimadzu Corporation), according to JIS-K7127: 1999, the test piece width is 10 mm, the distance between chucks is 100 mm, and the tensile speed is 200 mm / min. Under the conditions, 5%, 10%, 20%, 50%, 100% and 300% modulus intensities were measured. Here, the modulus strength was measured in the MD direction of the laminated film. If the 50% modulus strength (MD) is 10.0 MPa or less, it is judged that there is no practical problem in flexibility.

(2) Stress relaxation property In the measurement of the modulus strength, it was stopped at 50% elongation and maintained in that state for 10 minutes. Then, the modulus intensity after holding for 10 minutes was measured. Here, the modulus strength was measured in the MD direction of the laminated film. If the 50% elongation modulus strength after holding for 10 minutes was 5.5 MPa or less, it was judged that there was no practical problem.

(3) Haze and total light transmittance With respect to the obtained laminated film, the haze and total light transmittance were measured according to JIS-K7136: 2000 using a haze meter (manufactured by Suga Test Instruments Co., Ltd.), and the transparency of the laminated film was measured. Gender was evaluated. It was judged that there is no practical problem if the total light transmittance is 80% or more. In addition, Haze judged that there was no practical problem if it was 5% or less.

(4) Scratch resistance The scratch resistance of the obtained laminated film was evaluated from the degree of scratches formed on the surface of the laminated film by reciprocating steel wool with a load of 1 kg on the surface of the laminated film 5 times. It was carried out from the surface side of the ionomer resin layer.
⊚: Almost no scratches ○: Slight scratches are seen, but the permeability is not significantly reduced ×: Clearly whitened and the transparency is reduced.

The surface protective film of the example was excellent in the performance balance of flexibility, stress relaxation property, transparency and scratch resistance. On the other hand, the surface protective film of the comparative example was inferior in the performance balance of flexibility, stress relaxation property, transparency and scratch resistance.

A Thermoplastic polyurethane resin layer B Ionomer resin layer C Adhesive resin layer 10 Surface protective film

Claims (10)

Thermoplastic polyurethane resin layer (A) and
An ionomer resin layer (B) containing an ionomer (B1) of an ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer,
An adhesive resin layer (C) provided between the thermoplastic polyurethane resin layer (A) and the ionomer resin layer (B) and containing a polymer (C1) obtained by graft-copolymerizing an organic acid with an olefin compound. When,
Surface protective film with. In the surface protective film according to claim 1,
In the ionomer (B1) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer, the content of the structural unit derived from the unsaturated carboxylic acid with respect to all the structural units is 1% by mass or more and 20% by mass or less. Surface protective film. In the surface protective film according to claim 1 or 2.
The melt mass flow rate (MFR) of the ethylene / unsaturated carboxylic acid / unsaturated carboxylic acid ester copolymer ionomer (B1) measured under the conditions of 190 ° C. and 2160 g load according to JIS K7210: 1999 is 0. A surface protective film of 0.01 g / 10 minutes or more and 50 g / 10 minutes or less. In the surface protective film according to any one of claims 1 to 3,
A surface protective film in which the organic acid contains maleic anhydride. In the surface protective film according to any one of claims 1 to 4,
The polymer (C1) obtained by graft-copolymerizing an organic acid with the olefin compound is a maleic anhydride graft modified product obtained by graft-copolymerizing maleic anhydride with polyethylene, or maleic anhydride with an ethylene / α-olefin copolymer. A surface protective film containing at least one selected from a maleic anhydride graft modified product obtained by graft-copolymerizing maleic anhydride and a maleic anhydride graft modified product obtained by graft-copolymerizing maleic anhydride with an ethylene (meth) acrylate copolymer. .. In the surface protective film according to any one of claims 1 to 5,
A surface protective film having a haze of 5% or less measured according to JIS K7136: 2000. In the surface protective film according to any one of claims 1 to 6,
A surface protective film having a total light transmittance of 80% or more measured in accordance with JIS K7136: 2000. In the surface protective film according to any one of claims 1 to 7.
A surface protective film further comprising an adhesive layer (D) on either one of the outermost layers. In the surface protective film according to claim 8,
The pressure-sensitive adhesive layer (D) is composed of at least one type of pressure-sensitive adhesive selected from urethane-based pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, styrene-based pressure-sensitive adhesives, olefin-based pressure-sensitive adhesives, and acrylic-based pressure-sensitive adhesives. Surface protective film. In the surface protective film according to any one of claims 1 to 9,
A surface protection film that is a paint protection film.

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