KR20170097555A - Removal-type pressure-sensitive adhesive and surface protection film - Google Patents

Abstract

The present invention provides a re-releasable adhesive excellent in re-releasability, moist heat resistance, wettability and punching workability. The re-releasable adhesive comprises a urethane resin which is a reaction product of a polyol and a polyisocyanate, a curing agent, an ester compound excluding a urethane resin, and a deterioration inhibitor, wherein the polyol contains 50 wt% or more of a polyester polyol in 100 wt% of total polyol.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a pressure-

The present invention relates to a re-release type adhesive and a surface protective film using the same.

The surface protective film is preferably used for surface protecting applications such as substrates used in electronic parts materials, displays, and their manufacturing processes, taking advantage of the ability to peel off after attaching. For example, when manufacturing a liquid crystal display, it is used for surface protection in order to prevent breakage of the glass surface. The surface protective film is used by being punched out in accordance with the sizes of electronic members and displays. During the punching process, the pressure sensitive adhesive is adhered to the cutting blade in powder form, and the electronic member, the display, and the like may be contaminated with the pressure sensitive adhesive gas.

Patent Document 1 discloses a pressure-sensitive adhesive composition comprising an acrylic resin, an isocyanate crosslinking agent and a dimethyl silicone compound having a polyoxyalkylene, and a surface protective film using the pressure-sensitive adhesive composition (Claims 1 and 3).

Japanese Patent Application Laid-Open No. 2009-292959 Japanese Patent Application Laid-Open No. 2006-182795 Japanese Patent Application Laid-Open No. 2014-028876 Japanese Patent Application Laid-Open No. 2000-073040

However, in the surface protective film described in Patent Document 1, an acrylic resin is used as the pressure-sensitive adhesive layer, and bubbles are attracted to the interface between the pressure-sensitive adhesive layer and the adherend during use, which lowers the workability. Further, compatibility of the acrylic resin and the silicone compound is not sufficient and there is a problem that adherend contamination occurs. Recently, a surface protective film using a urethane resin having a high wettability to a pressure-sensitive adhesive layer has been published (Patent Documents 2 to 4, etc.).

In general, the performance of the urethane pressure-sensitive adhesive is greatly influenced by the type of polyol used. As the polyol component used in the urethane adhesive, polyester polyol and polyether polyol are well known.

Generally, the urethane pressure-sensitive adhesive using a polyester polyol has a high cohesive strength and accordingly can have high re-peeling property and good processability. However, these urethane pressure-sensitive adhesives have a high glass transition point and therefore have crystallinity, so that the coating workability can be deteriorated by increasing the viscosity of the resin solution. There is a possibility that the transparency or the hydrolysis resistance of the obtainable pressure-sensitive adhesive layer becomes insufficient. In addition, since the pressure-sensitive adhesive layer is hardened, there is a possibility that the low-temperature property is lowered.

On the other hand, when a polyether polyol is used as the polyol component, the urethane pressure-sensitive adhesive has a lower glass transition temperature than the polyester polyol, so that the coating film is smooth and the low-temperature property is good, but the cohesive force of the pressure-sensitive adhesive itself is low. If the cross-linking density of the pressure-sensitive adhesive is increased in order to improve this, it is difficult to obtain an optimum pressure-sensitive adhesive, since the coating becomes too hard and adherence becomes lower, the working time becomes short, and processing becomes problematic.

Although a pressure-sensitive adhesive using a combination of a polyether polyol and a polyester polyol is also shown for such improvement, it is a reality that a pressure-sensitive adhesive for re-peeling excellent in punching workability due to low cohesion of the pressure-sensitive adhesive itself is not obtained.

The present invention aims to provide a re-peelable pressure-sensitive adhesive excellent in re-peelability, moisture resistance, wettability and punching workability, and a surface protective film using the same.

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies to solve the above problems and found that the above problems can be solved by using a separating type pressure-sensitive adhesive containing a specific urethane resin and a deterioration inhibitor, and based on this knowledge, did.

That is, the re-peelable pressure-sensitive adhesive of the present invention comprises a reaction product of a polyol and a polyisocyanate, a urethane resin, a curing agent, an ester compound (except for a urethane resin) and a deterioration inhibitor, wherein the polyol comprises 100% , And 50% by mass or more of a polyester polyol.

The surface protective film of the present invention is provided with a base material and a pressure-sensitive adhesive layer which is a cured product of the releasable pressure-sensitive adhesive.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a peelable pressure-sensitive adhesive excellent in re-peelability, heat resistance, wettability and punch workability and a surface protective film using the same.

Before describing the present invention in detail, terms are defined. Unless otherwise specified, sheets, films and tapes are synonymous. The adherend refers to the other side to which the surface protective film is attached.

&Quot; Re-peelable pressure-sensitive adhesive "

The re-peelable pressure-sensitive adhesive of the present invention comprises a reaction product of a polyol and a polyisocyanate, a urethane resin, a curing agent, an ester compound (except for a urethane resin) and a deterioration inhibitor, wherein the polyol is a poly And an ester polyol in an amount of 50% by mass or more.

≪ Urethane resin &

The urethane resin used in the present invention is a resin obtained by reacting a polyol and a polyisocyanate, and has a plurality of hydroxyl groups. The polyol (raw material polyol) contains 50% by mass or more of the polyester polyol in 100% by mass of the total polyol.

[Polyol]

The urethane resin raw material polyol is polyester polyol in an amount of 50% by mass or more in 100% by mass of the total polyol. By using the polyester polyol as the main component of the starting polyol in this way, a urethane resin which is tough and excellent in abrasion resistance can be obtained and a re-peelable pressure-sensitive adhesive excellent in punching workability can be obtained. The amount of the polyester polyol in the total polyol is preferably 50 to 100 mass%, more preferably 65 to 100 mass%, more preferably 70 to 100 mass%, and most preferably 80 to 100 mass%.

The polyester polyol can be produced, for example, by using an acid component and a polyhydric alcohol.

Examples of the acid component include terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid and trimellitic acid, among which adipic acid is particularly preferable.

Polyhydric alcohols include polyhydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexane glycol, 3-methyl-1,5-pentanediol, 3,3'-dimethylolheptane, polyoxyethylene glycol, poly Propylene glycol, isopropylene glycol, 1,4-butanediol, neopentyl glycol, butyl ethyl pentane diol, glycerin, trimethylol propane and pentaerythritol.

As the polyester polyol, an aliphatic polyester polyol is preferable, and an adipic acid polyester polyol is particularly preferable. A polyester polyol obtainable by using adipic acid as an acid component and using a glycol-based diol with a polyhydric alcohol is preferable.

The polyester polyol is preferably an amorphous polyester polyol, and for example, a polyester polyol obtainable by using adipic acid and 3-methyl-1,5-pentanediol is particularly preferable. The polyester polyol is amorphous, easy to handle since it is a low-viscosity liquid at room temperature, and may have high hydrolysis resistance due to the presence of a methyl group derived from 3-methyl-1,5-pentanediol.

The starting polyol of the urethane resin preferably contains at least 50% by mass of at least the amorphous polyester polyol among 100% by mass of the total polyol, more preferably 60% by mass or more, and more preferably 65% by mass or more.

The number average molecular weight of the polyester polyol is preferably 500 to 5,000, more preferably 1,000 to 5,000, and particularly preferably 2,000 to 5,000. The number average molecular weight is 500 or more, the reaction control at the time of synthesis becomes easier and the number average molecular weight is less than 5,000, the time to completion of the reaction is shortened and the cohesive force of the pressure-sensitive adhesive layer is easily maintained, do.

As the polyester polyol, a polyfunctional polyester polyol having two or more hydroxyl groups in the molecule can be used. Among them, from the viewpoint of reactivity, those having two or three hydroxyl groups are preferably used, and polyester diols having two hydroxyl groups are particularly preferable.

The raw material polyester polyol of the urethane resin preferably contains 20% by mass or more, more preferably 20 to 100% by mass, further preferably 30 to 100% by mass, of the polyester diol in 100% by mass of the total polyester polyol, Preferably 50 to 100% by mass.

The raw material polyester polyol contains 20 mass% or more of polyester diol to prevent the pressure-sensitive adhesive layer from being excessively hardened by reaction with the curing agent, thereby improving the workability. When the polyester diol is contained in an amount of 30 mass% or more, the coating performance is improved.

The number average molecular weight of the polyester diol is preferably 500 to 5,000, more preferably 1,000 to 5,000, and particularly preferably 2,000 to 5,000.

As the raw material polyol, other polyol may be used in combination with the polyester polyol as needed within the range not impairing the effect of the present invention. Other polyols include polyether polyols, polycarbonate polyols and acrylic polyols, among which polyether polyols are preferred.

Examples of the polyether polyol include polyoxytetramethylene glycol (PTMG), polyoxypropylene glycol (PPG), and polyoxyethylene glycol (PEG).

From the viewpoint of reactivity, the polyether polyol preferably has two or three hydroxyl groups. And a number average molecular weight of 500 to 15,000.

[Polyisocyanate]

As the polyisocyanate, a known compound can be used. Specifically, aromatic polyisocyanate, aliphatic polyisocyanate, aromatic aliphatic polyisocyanate and alicyclic polyisocyanate are preferable.

Examples of the aromatic polyisocyanate include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4- Diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4'-diphenyl ether diisocyanate, 4,4 ', 4 "-triphenyl methane triisocyanate, and the like.

Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3- , Dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

Examples of the aromatic aliphatic polyisocyanate include ω, ω'-diisocyanate-1,3-dimethylbenzene, ω'-diisocyanate-1,4-dimethylbenzene, ω'-diisocyanate- Benzene, 1,4-tetramethylxylene diisocyanate, and 1,3-tetramethylxylene diisocyanate.

Examples of the alicyclic polyisocyanate include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl Cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylene bis (cyclohexyl isocyanate), 1,4-bis (isocyanatomethyl) cyclohexane, Bis (isocyanatomethyl) cyclohexane, and the like.

For the synthesis of the urethane resin, a catalyst may be used if necessary. The reaction time is shortened by the use of a catalyst. As the catalyst, a tertiary amine compound and an organometallic compound are preferable.

Examples of the tertiary amine compound include triethylamine, triethylenediamine, and 1,8-diazabicyclo [5,4,0] -undecene-7 (DBU).

The organometallic compounds include tin-based compounds and non-tin-based compounds.

Examples of the tin compound include dibutyltin dichloride, dibutyltin oxide, dibutyltin bromide, dibutyltin dumarate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulphide, Tributyl tin oxide, tributyl tin acetate, triethyl tin ethoxide, tributyl tin ethoxide, dioctyl tin oxide, tributyl tin chloride, tributyl tin trichloroacetic acid and 2-ethylhexanoic acid Comments, and the like.

Examples of the non-tin compound include titanium compounds such as dibutyltitanium dichloride, tetrabutyl titanate and butoxy titanium trichloride; Lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate and lead naphthenate; Iron compounds such as iron 2-ethylhexanoate and iron acetylacetonate; Cobalt compounds such as cobalt benzoate and cobalt 2-ethylhexanoate; Zinc compounds such as zinc naphthenate and zinc 2-ethylhexanoate; And zirconium compounds such as zirconium naphthenate.

The catalyst is preferably used in an amount of about 0.01 to 1% by mass based on the total of 100% by mass of the polyol and the polyisocyanate. Since the reactivity differs depending on the polyol, a suitable catalyst can be used depending on the polyol used.

The urethane resin may be synthesized by (1) a method in which a polyol, a polyisocyanate and, if necessary, a catalyst are charged in a flask, or (2) a method in which a polyol and, if necessary, a catalyst are dropped into a flask and reacted while dropping the polyisocyanate .

For synthesis of the urethane resin, a known solvent may be used if necessary. Specific examples thereof include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone.

The weight average molecular weight (Mw) of the urethane resin is preferably 30,000 to 400,000, more preferably 50,000 to 300,000. When the weight average molecular weight is 30,000 or more, the heat resistance is improved. In addition, it is less than 400,000 won, the re-peelability is further improved.

The urethane resin preferably has a hydroxyl value per solid solid of resin of 5 to 40 mgKOH / g, more preferably 5 to 35 mgKOH / g. The hydroxyl value of the urethane resin is 5 mgKOH / g or more, which improves the adhesive strength and improves the heat resistance and the heat and humidity resistance. When the hydroxyl value is 40 mgKOH / g or less, punching workability is improved. The hydroxyl value can be measured by a titration method using potassium hydroxide according to JIS K0070.

<Curing agent>

The curing agent is preferably a compound capable of reacting with the hydroxyl group of the urethane resin, and a polyfunctional isocyanate compound is more preferable.

Examples of polyfunctional isocyanate compounds include aromatic diisocyanates such as tolylene diisocyanate, hexadiisocyanate, isophorone diisocyanate, xylene diisocyanate, hydrogenated xylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylene diisocyanate, Polyisocyanate compounds such as isocyanate, triphenylmethane triisocyanate, and polymethylene polyphenyl isocyanate;

An adduct of the polyisocyanate compound with a polyol compound such as trimethylolpropane, or a burette / isocyanurate;

Examples of the polyisocyanate compound include known polyols (polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol, etc.) and adducts.

Among them, a polyisocyanate compound having two or three isocyanate groups is preferable, and an allophanate compound of hexa diisocyanate, an isocyanurate compound of hexa diisocyanate, and a trimethylol propane adduct of hexa diisocyanate More preferred is an isocyanurate of hexadiisocyanate.

The polyfunctional isocyanate compound may be used alone or in combination of two or more.

The amount of the polyfunctional isocyanate compound to be used is preferably from 1.0 to 4.0 equivalents, more preferably from 1.25 to 3.75 equivalents, still more preferably from 1.5 to 3.5 equivalents, based on the hydroxyl group equivalent of the urethane resin.

If the amount of the polyfunctional isocyanate compound is more than 4.0 equivalents based on the hydroxyl equivalent of the urethane resin, the urethane resin becomes excessively hard and the punching workability due to contamination by the pressure-sensitive adhesive gas may deteriorate. When the amount of the polyfunctional isocyanate compound is less than 1.0, And the residue adheres to the adherend when the surface protective film is separated. By adjusting the amount of the polyfunctional isocyanate compound to be 1.0 to 4.0 equivalents based on the hydroxyl equivalent of the urethane resin, it becomes easier to balance the punching workability and re-releasability.

&Lt; ester compound &

The releasable pressure-sensitive adhesive of the present invention includes an ester compound. However, except for urethane resin. The ester compound imparts a role as a plasticizer, and its molecular weight is preferably 300 to 850, more preferably 300 to 700. When an ester compound having a molecular weight of 300 or more is used, heat resistance is more excellent, and when an ester compound having a molecular weight of 850 or less is used, low temperature characteristics and wettability are excellent. Molecular weight is a formula.

As the ester compound, various known ester compounds may be used depending on the compatibility with the urethane resin to be used. For example, monoester-based, polyester-based and ether-ester-based ones. Among them, an ester compound having a high polarity is preferable from the viewpoint of compatibility with a urethane resin, and an ether ester compound is particularly preferable.

Examples of the ether ester compound include adipic acid dibutoxyethyl, adipic acid di (butoxyethoxyethyl), adipic acid di (methoxy tetraethylene glycol), adipic acid di (methoxypentaethylene glycol) and adipic acid An ester compound of an adipic acid such as tetraethylene glycol) or adipic acid (methoxypentaethylene glycol) and an ether bond-containing alcohol; Ester compounds of azelaic acid such as dibutoxyethyl azelate and azelaic acid (butoxyethoxyethyl) with an ether bond-containing alcohol; Ester compounds of sebacic acid such as dibutoxy ethyl sebacate and sebacic acid (butoxyethoxyethyl) with an ether bond-containing alcohol; Ester compounds of phthalic acid such as dibutoxyethyl phthalate and di (butoxyethoxyethyl) phthalate with an ether bond-containing alcohol; Ester compounds of isophthalic acid such as dibutoxyethyl isophthalate and di (butoxyethoxyethyl) isophthalate and ether bond-containing alcohol; Polyethylene glycol and polypropylene glycol and an acidic component such as a monocarboxylic acid such as butanoic acid, isobutanoic acid and 2-ethylhexyl acid or a dicarboxylic acid such as adipic acid and phthalic acid Ester compounds containing a polyether component and the like.

The ester compound may be used alone or in combination of two or more kinds.

The ester compound is preferably used in an amount of 0.5 to 50 parts by mass, more preferably 1 to 40 parts by mass, and still more preferably 5 to 40 parts by mass in 100 parts by mass of the urethane resin. When the ester compound is used in an amount of 1 part by mass or more, the re-peelability, the low-temperature characteristics and the wettability are further improved. Further, if it is used in an amount of 50 parts by mass or less, it is possible to further suppress contamination to adherends.

&Lt; Deterioration inhibitor >

The re-peelable pressure-sensitive adhesive of the present invention comprises a detackifying agent. As a result, deterioration or deterioration of the re-peelable pressure-sensitive adhesive in a high temperature and high humidity atmosphere can be prevented, suppression of re-peelability can be suppressed, and deterioration of adherence can be suppressed.

The content of the decalcifying agent is preferably 0.1 to 5 parts by mass, more preferably 0.5 to 4.5 parts by mass, and still more preferably 0.5 to 4.0 parts by mass with respect to 100 parts by mass of the urethane resin.

It is preferable to use at least one member selected from the group consisting of moisture release agents, antioxidants, ultraviolet absorbers and light stabilizers. Even if one kind of the deterioration inhibitor is used alone, two or more kinds of the same kind of the deterioration inhibitor may be used or two or more kinds of the different types of the deterioration inhibitor may be used together. Use of two or more kinds of other types of deterioration inhibiting agents is preferable because deterioration or deterioration of the ester compound can be more effectively prevented in a high temperature and high humidity atmosphere, deterioration of re-peeling property of the pressure-sensitive adhesive and deterioration of adhering contamination can be suppressed more effectively.

In combination with antioxidants, I can remove moisture with antioxidants, I release moisture with ultraviolet absorber, I release moisture with light stabilizer, I release moisture with antioxidant, I release moisture with ultraviolet absorber, Ultraviolet absorbers, antioxidants and light stabilizers, ultraviolet absorbers and light stabilizers, and the like. Preferably, an antioxidant is required, and this is a case of using a water-releasing or ultraviolet absorber together, and more preferably, an antioxidant and a water-releasing agent are used together. By using the antioxidant in combination with the water release or ultraviolet absorber, deterioration or deterioration of the ester compound in the high temperature and high humidity atmosphere can be more effectively prevented, deterioration of the releasability of the pressure-sensitive adhesive agent and deterioration of adherent contamination can be suppressed more effectively, It is preferable because moisture release and ultraviolet ray inhibitor itself can be suppressed from yellowing and coloring of the pressure-sensitive adhesive can be suppressed. It is also preferable to use at least three kinds of deterioration inhibitors in combination. Particularly preferred is a combination of an antioxidant and an ultraviolet absorber.

When two or more kinds of antitarnish agents are used in combination, it is preferable that the total amount of the moisture release, the ultraviolet absorber and the light stabilizer is 10 to 400 parts by mass in 100 parts by mass of the antioxidant. This makes it possible to suppress the decomposition of moisture and the ultraviolet inhibitor itself and the yellowing of heat.

[I turn off moisture]

It is preferable that the urethane pressure-sensitive adhesive contains moisture release in order to block the carboxyl groups generated when hydrolysis occurs under a high temperature and high humidity atmosphere.

The moisture release is selected, for example, from carbodiimide, isocyanate, oxazoline and epoxy systems. Among them, a carbodiimide system is preferable because of its high hydrolysis inhibiting effect. The moisture release may be used alone or in combination of two or more kinds.

The amount of moisture release is preferably 0.01 to 2.0 parts by mass, more preferably 0.02 to 1.5 parts by mass, and still more preferably 0.05 to 1.0 parts by mass with respect to 100 parts by mass of the urethane resin.

It is good to use the antioxidant in combination with the release of moisture. Concretely, it is preferable to use a combination of a carbodiimide-based moisture release agent and a phenol-based antioxidant, and more preferably a combination of a carbodiimide-based moisture release agent and a phenol-based antioxidant and a phosphorus-based antioxidant. By using the water release and the antioxidant in combination, the hydrolysis resistance is further improved, and the decomposition of the moisture release itself and the occurrence of yellowing of the water can be suppressed.

The release of moisture in the carbodiimide-based compound is a compound having at least one carbodiimide group in the molecule.

Examples of the monocarbodiimide compound include dicyclohexylcarbodiimide, diisopropylcarbodiimide, dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, diphenylcarbodiimide, and naphthylcarbodiimide. Meade and the like.

An example of the polycarbodiimide compound is a high molecular weight polycarbodiimide produced by a decarboxylic acid condensation reaction of a diisocyanate in the presence of a catalyst for addition of a carbodiimide. Examples of the starting diisocyanate include 4,4'-diphenylmethane diisocyanate, 3,3'-dimethoxy-4,4'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'- Isocyanate, 4,4'-diphenyl ether diisocyanate, 3,3'-dimethyl-4,4'-diphenyl ether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, -Methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and tetramethylxylene diisocyanate. Examples of the catalyst for addition of carbodiimide include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phosphorene- -Oxime, 1-ethyl-2-phospholene-1-oxide, and phosphorane oxides such as these 3-phosphorene isomers.

The hydrolysis-inhibiting effect of the carbodiimide-based compound is preferable when compatibility with the urethane resin is good. From this point of view, it is preferable that the carbodiimide-based water-releasing agent is hydrophilic and some or all of it is dissolved in water. The hydrophilicity of the carbodiimide-based resin can be improved by using the water-releasing agent.

The isocyanate-based water-releasing agent is preferably at least one selected from the group consisting of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, , 4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3'-dihydrodemethoxy- , 4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate , 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, xylene diisocyanate, tetramethylxylene di Iso Cyanate, hydrogenated xylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and 3,3'-dimethyl-4,4'-dicyclohexyl Methane diisocyanate, and the like.

The water-releasing of the oxazoline-based ones is performed by using 2,2'-o-phenylenebis (2-oxazoline), 2,2'-m-phenylenebis (2-oxazoline), 2,2'- Bis (4-methyl-2-oxazoline), 2,2'-p-phenylenebis (4,4'-dimethyl-2-oxazoline), 2,2'-m-phenylenebis (4,4'-dimethyl- (2-oxazoline), 2,2'-tetramethylene bis (2-oxazoline), 2,2'-hexamethylene bis (2-oxazoline), 2,2'-octamethylene bis (2-oxazoline), 2,2'-ethylene bis (4-methyl-2-oxazoline) and 2,2'-diphenylene bis (2-oxazoline).

The epoxy-based water-releasing agent includes diglycidyl ether of an aliphatic diol such as 1,6-hexanediol, neopentyl glycol, and polyalkylene glycol; Polyglycidyl ethers of aliphatic polyols such as sorbitol, sorbitan, polyglycerol, pentaerythritol, diglycerol, glycerol, and trimethylol propane; Polyglycidyl ether of an aliphatic cyclic polyol such as cyclohexanedimethanol; Diglycidyl esters or polyglycidyl esters of aliphatic or aromatic polycarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, trimellitic acid, adipic acid and sebacic acid; Resorcinol, bis- (p-hydroxyphenyl) methane, 2,2-bis- (p-hydroxyphenyl) propane, tris (p- hydroxyphenyl) methane and 1,1,2,2-tetrakis (p-hydroxyphenyl) ethane; polyglycidyl ether or polyglycidyl ether; N-diglycidyl aniline, N, N-diglycidyl toluidine and N, N, N ', N'-tetraglycidyl-bis- (p- Glycidyl derivatives; Triglycidyl derivatives of aminophenols; Triglycidyl tris (2-hydroxyethyl) isocyanurate, triglycidyl isocyanurate, orthocresol novolak type epoxy; Phenol novolak type epoxy, and the like.

[Antioxidant]

When the urethane resin deteriorates due to heat, it is preferable to use an antioxidant because the compatibility with the ester compound is poor and the ester compound tends to leak out. Examples of the antioxidant include a radical reinforcing agent and release of peroxide. Examples of the radical reinforcing agent include a phenol compound and an amine compound, and the peroxide decomposer includes a sulfur compound and a phosphorus compound. Particularly, phenolic compounds having a role as a radical reinforcing agent in terms of heat stability and antioxidant effect are preferable. By using a phenolic compound, properties such as stability at a high temperature with time, stability with respect to a wet heat stability with time, and long-term wet heat storage property (refer to the items of [Examples] for evaluation methods thereof) are preferable. It is also preferable that a phenolic compound and a phosphorous compound serving as a release of peroxide are used in combination to improve the thermal stability effectively. More preferably, the antioxidant is a combination of a phenolic compound and a phosphorus compound with a water-releasing agent. As a result, deterioration of the urethane resin due to heat can be prevented more effectively, and the propagation of the ester compound can be more effectively suppressed.

The amount of the antioxidant is preferably 0.01 to 2.0 parts by mass, more preferably 0.1 to 1.5 parts by mass, and still more preferably 0.2 to 1.0 parts by mass based on 100 parts by mass of the urethane resin.

Examples of the phenolic compound include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6- Di-t-butyl-4-hydroxyphenylpropionate, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'- Butylphenol), 4,4'-thiobis (3-methyl-6-t-butylphenol), 4,4'-butylidenebis -Bis [1,1-dimethyl-2 -? - (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro [ T-butyl (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6- (3 ', 5'-di-t-butyl-4'-hydroxyphenylpropionate) methane, bis [3, (3'-hydroxy-3'-t-butylphenyl) butyric acid] glycol ester and 1,3,5-tris (3 ', 5'-di- Benzyl) -S-triazine-2,4,6- (1H, 3H, 5H) trione, tocopherol And the like.

Phosphorus antioxidants include triphenylphosphite, diphenyl isodecyl phosphite, 4,4'-butylidene bis (3-methyl-6-tert-butylphenyldontecyl) phosphite, cyclic neopentanetetraylbis (Octadecylphosphite), tris (nonylphenyl) phosphite, tris (monononylphenyl) phosphite, tris (dinonylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, 9,10-dihydro- 10-phosphaphenanthrene-10-oxide, 10- (3,5-di-tert-butyl-4-hydroxybenzyl) -9,10-dihydro-9-oxa- (2, 3-di-tert-butylphenyl) phosphite, cyclic neopentylsulfosuccinic acid, (2,4-di-tert-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-tert-butyl-4-methylphenyl) phosphite and 2,2- (4,6-di-tert-butylphenyl) octylphosphor It can be a bit like.

[UV absorber]

Examples of the ultraviolet absorber include benzophenone compounds, benzotriazole compounds, salicylic acid compounds, oxalic acid anilide compounds, cyanoacrylate compounds and triazine compounds.

The amount of the ultraviolet absorber is preferably 0.01 to 3.0 parts by mass, more preferably 0.1 to 2.5 parts by mass, and still more preferably 0.2 to 2.0 parts by mass based on 100 parts by mass of the urethane resin.

[Light stabilizer]

Examples of the light stabilizer include hindered amine compounds and hindered piperazine compounds. The light stabilizer is preferably 0.01 to 2.0 parts by mass, more preferably 0.1 to 1.5 parts by mass, and still more preferably 0.2 to 1.0 parts by mass based on 100 parts by mass of the urethane resin.

<Leveling agent>

The releasable pressure-sensitive adhesive of the present invention preferably further comprises a leveling agent. The urethane resin having a high proportion of the polyester polyol in the raw polyol has a high polarity and a high surface energy. Therefore, the affinity with a low polarity solvent such as toluene used as a reaction solvent or a diluting solvent is lowered, The leveling property may become insufficient. If the leveling property of the pressure-sensitive adhesive is insufficient, appearance defects such as lumps, stains, and coating line marks may occur when the pressure-sensitive adhesive is coated.

The leveling agent content in the urethane pressure-sensitive adhesive of the present invention is preferably 0.001 to 2.0 parts by mass, more preferably 0.01 to 1.5 parts by mass, and still more preferably 0.1 to 1.0 parts by mass with respect to 100 parts by mass of the urethane resin.

By adjusting the content of the leveling agent within the above range, the urethane adhesive of the present invention can further reduce the contamination to the adherend, and at the same time, it is possible to secure sufficient leveling property, and a smooth coating film can be obtained. The paper may be good or two or more.

As the leveling agent, any suitable leveling agent can be employed as long as the effect of the present invention is not impaired. Examples of the leveling agent include an acrylic leveling agent, a fluorine leveling agent, and a silicon leveling agent, and the acrylic leveling agent is less likely to be contaminated with the adhesive.

The weight average molecular weight (Mw) of the leveling agent is preferably 500 to 20,000, more preferably 1,000 to 15,000, and still more preferably 2,000 to 10,000. When the weight average molecular weight (Mw) is 500 or more, the amount of the component to be vaporized when the adhesive is heated and dried after coating is suppressed to a low level, so that contamination of the drying oven by the vaporized component can be suppressed. When the weight average molecular weight (Mw) is 20,000 or less, the movement of the molecules is not inhibited by the linkage of the polymer and the leveling property is improved.

<Antistatic agent>

The urethane pressure-sensitive adhesive of the present invention may further contain an antistatic agent if necessary. By including the antistatic agent, it is possible to suppress the failure of the electronic apparatus or the like due to the static electricity generated when the surface protective film is peeled off.

The antistatic agent is preferably an inorganic salt, a polyhydric alcohol compound, or an ionic liquid, and more preferably an ionic liquid. The &quot; ionic liquid &quot; may be a room temperature molten salt, and is a salt having fluidity at 25 [deg.] C.

Inorganic salts include inorganic salts such as sodium chloride, potassium chloride, lithium chloride, lithium perchlorate, ammonium chloride, potassium chlorate, aluminum chloride, copper chloride, ferrous chloride, ferric chloride, ammonium sulfate, potassium nitrate, sodium nitrate, sodium carbonate and sodium thiocyanate have.

Examples of the polyhydric alcohol compound include propanediol, butanediol, hexanediol, polyethylene glycol, trimethylolpropane, and pentaerythritol.

Examples of ionic liquids containing imidazolium ions include 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1,3-dimethylimidazolium bis (trifluoromethylsulfonyl Imide and 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide.

Examples of ionic liquids containing pyridinium ions include 1-methylpyridinium bis (trifluoromethylsulfonyl) imide, 1-butylpyridinium bis (trifluoromethylsulfonyl) imide, 1-hexylpyridinium bis (Trifluoromethylsulfonyl) imide, 1-hexyl-4-methylpyridinium bis (trifluoromethylsulfonyl) imide, 1- Octyl-4-methylpyridinium bis (trifluoromethylsulfonyl) imide, 1-octyl-4-methylpyridinium bis (fluorosulfonyl) imide Methylpyridinium bis (perfluoroethylsulfonyl) imide and 1-methylpyridinium bis (perfluorobutylsulfonyl) imide, and the like.

As the ionic liquid containing ammonium ions, trimethylheptylammonium bis (trifluoromethanesulfonyl) imide, N, N-diethyl-N-methyl-N-propylammonium bis (trifluoromethanesulfonyl) (Trifluoromethanesulfonyl) imide, N, N-diethyl-N-methyl-N-heptylammonium bis (trifluoromethanesulfonyl) imide Imide and tri-n-butylmethylammonium bistrifluoromethanesulfonimide, and the like.

Other commercially available ionic liquids such as pyrrolidinium salts, phosphonium salts and sulfonium salts can be suitably used.

The antistatic agent may be used alone or in combination of two or more kinds.

The amount of the antistatic agent is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the urethane resin.

The re-peelable pressure-sensitive adhesive of the present invention may further contain additives such as a silane coupling agent, a colorant, an extinguishing agent, a wetting agent, a weathering stabilizer, a softener, a curing accelerator, and a curing retarder, if necessary.

"Surface protective film"

The surface protective film of the present invention comprises a substrate and a pressure-sensitive adhesive layer which is a cured product of the re-peelable pressure-sensitive adhesive of the present invention. The pressure-sensitive adhesive layer can be formed on one side or both sides of the substrate.

The method for producing the surface protective film using the re-peelable pressure-sensitive adhesive of the present invention includes (1) a method in which a releasable pressure-sensitive adhesive is coated on the release liner and heated and dried to form a pressure-sensitive adhesive layer, A method in which a releasable pressure-sensitive adhesive is coated and heated and dried to form a pressure-sensitive adhesive layer, and then a release liner is stuck thereon. Further, the pressure-sensitive adhesive layer is generally protected with a release liner until just before use of the surface protective film.

Examples of the coating method of the re-peelable pressure-sensitive adhesive include a roll coater method, a comma coater method, a lip coater method, a die coater method, a reverse coater method, a silk screen method and a gravure coater method. After coating, it is generally heated and dried using a hot air oven and an infrared heater.

The thickness of the re-peelable pressure-sensitive adhesive layer (thickness after drying) is usually about 1 to 200 占 퐉, preferably about 5 to 100 占 퐉, and more preferably about 10 to 100 占 퐉.

As the base material, a general material can be used as a base material of a pressure-sensitive adhesive such as nonwoven fabric, paper, plastic and synthetic paper, and plastic is preferable.

The plastic may be a polyolefin such as polyethylene and polypropylene, a polyester such as polyethylene terephthalate, a polyamide such as polyphenylene sulfide (PPS), triacetylcellulose, cycloolefin, polyimide and nylon, Polyethylene terephthalate and the like are preferable.

The substrate may be subjected to this adhesion (easy adhesion) treatment in advance in order to enhance the adhesion between the pressure-sensitive adhesives. Examples of the adhesion treatment method include a dry method directed to a corona discharge and a wet method in which an anchor coat agent is coated. The thickness of the substrate is generally about 5 to 1000 mu m.

The substrate may be provided with an antistatic layer. The antistatic layer includes a resin and an antistatic agent. In addition to the antistatic agent of the above example, the antistatic agent is preferably conductive carbon particles, conductive metal particles and conductive polymer, and the antistatic layer may be formed by vapor deposition, sputtering or plating of a metal with respect to the substrate.

The release liner generally has a release layer formed by coating a release agent on a base material of paper, plastic, and synthetic paper. Examples of the releasing agent include a silicone resin, an alkyd resin, a melamine resin, a fluororesin, and an acrylic resin. The thickness of the release liner is generally about 10 to 150 mu m.

[Example]

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples. Unless otherwise specified, "part" means "part by mass" and "%" means "% by mass".

The weight average molecular weight (Mw) of the resin, the viscosity of the resin and the hydroxyl value of the resin are measured as follows.

(The weight average molecular weight (Mw)

The weight average molecular weight was measured under the following conditions. The weight average molecular weight is a weight average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC). The measurement conditions are as follows.

Device: SHIMADZU Prominence (manufactured by Shimadzu Corporation)

Column: Three TOSOH TSK-GEL GMHXL (manufactured by TOSOH CORPORATION) were connected in series,

Solvent: tetrahydrofuran,

Flow rate: 0.5 ml / min,

Solvent temperature: 40 DEG C,

Sample concentration: 0.1% by mass,

Sample injection amount: 100 μl.

(Viscosity of resin)

The viscosity was measured under the following conditions in accordance with JIS Z8803.

Apparatus: B-type viscometer TVB10M (TOKI Sangyo Co., Ltd.)

Rotor: No.3,

Rotation speed: 12 rpm,

Measuring temperature: 25 캜.

(Hydroxyl value)

Was measured by the neutralization titration method according to JIS K0070 as follows. First, 25 g of acetic anhydride was added to 100 ml of a flask, and pyridine was added to make a total amount of 100 ml. The mixture was sufficiently shaken to prepare an acetylation reagent. The acetylation reagent obtained was stored in a brown bottle so that it could not reach the vapor of moisture, carbon dioxide and acid. Next, the sample was placed in a flat bottom flask, and 5 ml of the acetylation reagent was added to the flask using a pipette. Next, a small funnel was placed at the inlet of the flask, and about 1 cm of the bottom of the flask was immersed in a glycerin bath at a temperature of 95 to 100 DEG C and heated. In this process, to prevent the head portion of the flask from being heated by the heat of the glycerin bath, a circular plate of a cardboard having a round hole at the center thereof was placed on the portion of the head portion of the flask. After one hour from the initiation of heating, the flask was taken out from the glycerin bath, cooled, and then 1 ml of water was added to the funnel and the mixture was shaken to decompose the acetic anhydride. In order to complete the decomposition, the flask was again heated in a glycerin bath for 10 minutes, and after cooling, the funnel and the inner wall of the bottle were washed with 5 ml of ethanol. A few drops of phenolphthalein solution were added to the indicator, titrated with a 0.5 mol / l potassium hydroxide ethanol solution, and the end point of the indicator light was maintained for about 30 seconds. A blank test in which no sample was separately added was performed as described above. The hydroxyl value of the urethane resin (solid content) was calculated by the following equation.

(Formula 1) A = (B-C) x f x 28.05 / S) / (non-volatile matter concentration / 100) + D

A: hydroxyl value (mgKOH / g), B: amount of 0.5 mol / l potassium hydroxide ethanol solution used in the blank test, C: amount of 0.5 mol / l ethanol hydroxide solution used for titration (Concentration correction factor) of potassium hydroxide ethanol solution, S: mass of the sample (g), D: acid value (mgKOH / g).

Next, examples of synthesis of a urethane resin solution will be described using examples and comparative examples.

(Synthesis Example 1)

Necked flask equipped with a stirrer, a reflux condenser, a nitrogen-introducing tube thermometer and a dropping funnel was charged with 100 parts of a polyester polyol P-1010 (bifunctional polyester polyol, hydroxyl value 112, number average molecular weight 1000, , 15.5 parts by mass of hexadiyisocyanate (manufactured by Sumitomo Bayer Co., Ltd.), 77 parts by mass of toluene, 0.25 parts by mass of dibutyltin dilaurate as a catalyst, and 0.01 parts by mass of tin 2-ethylhexanoate. The flask was gradually warmed and reacted at about 90 ° C for 2 hours. The reaction was continued with frequent confirmation of the disappearance of isocyanate groups in the infrared absorption (IR) spectrum. After confirming the disappearance of the isocyanate group, the cooled reaction was terminated immediately. Subsequently, toluene was added so that the nonvolatile component (NV) became 60% to obtain a urethane resin 1 solution having a viscosity (VIS) of 3,000 mPa 1. The urethane resin 1 (solid content) had a hydroxyl value (OH value) of 7.6 mgKOH / g and a weight average molecular weight (Mw) of 55,000. Table 1 shows the solid content (NV) and viscosity (VIS) of the urethane resin solution, the hydroxyl value (OH value) and the weight average molecular weight (Mw) of the urethane resin 1 (solid component).

(Synthesis Examples 2 to 13)

In each case of Synthesis Examples 2 to 13, the same procedures as in Synthesis Example 1 were carried out except that the raw materials and the blending amounts were changed as shown in Table 1 to obtain urethane resin solutions 2 to 13. The solid content (NV) and viscosity (VIS) of the urethane resin solution, the hydroxyl value (OH value) and the weight average molecular weight (Mw) of the urethane resin are shown in Table 1.

[Example 1]

To 100 parts by mass of the urethane resin in the solution of the urethane resin 1 obtained in Synthesis Example 1 was added isocyanurate modified product of hexadienisocyanate (Coronate HX, trade name: Coronate HX, nonvolatile matter 100% by mass, NCO , 5.4 parts by mass as an ester compound and 30 parts by mass of adipic acid bis (2-butoxyethyl) (trade name: D931, non-volatile matter 100% by mass, molecular weight: 346) as an antioxidant 0.8 parts by mass of a phenol-based antioxidant (trade name IRGANOX1010, product of BASF Japan Ltd., nonvolatile content of 100% by mass) and phosphorus-based antioxidant (trade name IRGAFOS168, nonvolatile content of 100% by mass, (CarbodiLite V-09GB, trade name: 75% by mass, nonvolatile content: 75% by mass) in terms of solid content as a water-releasing agent, 0.1 part by mass of ultraviolet ray inhibitor And triazine-based ultraviolet (Trade name: TINUVIN 477, nonvolatile matter 80% by mass, manufactured by BASF Japan Co., Ltd.) as a solid content 0.5 part by mass, a hindered amine light stabilizer (product of BASF Japan, 123, nonvolatile matter: 100 mass%) as a solvent and 5 parts by mass of ethyl acetate as a solvent were blended to obtain a pressure-assisted urethane pressure-sensitive adhesive.

This urethane pressure-sensitive adhesive was coated on a PET substrate (Lumirra T60, Doraisha) having a thickness of 50 占 퐉 so that the thickness after drying was 50 占 퐉, dried at 100 占 폚 for 4 minutes and then exposed to a 25 占 퐉 release liner (250010BD, manufactured by Fujimori Kogyo Co., Respectively. Then, the film was allowed to stand at 23 ° C-50% for 1 week to obtain a surface protective film.

[Examples 2 to 33 and Comparative Examples 1 to 4]

In Examples 2 to 33 and Comparative Examples 1 to 4, a urethane pressure-sensitive adhesive and a surface protective film were obtained in the same manner as in Example 1, except that the raw materials and blending amounts were changed as shown in Table 2.

The following evaluations were made on the surface protective films obtained in each of the Examples and Comparative Examples.

<Glass adhesion strength>

The obtained surface protective film was prepared to have a width of 25 mm and a length of 100 mm to prepare a sample. Subsequently, the release liner was peeled off from the sample under an atmosphere of 23 ° C-50% RH, the exposed pressure-sensitive adhesive layer was bonded to the glass plate, and one reciprocating pressure was applied with a roller of 2 kg and left for 24 hours. The adhesive strength was measured under the condition of a speed of 0.3 m / min. In general, the adhesive strength to glass is low and it is easy to peel again.

<Stability at high temperature>

The obtained surface protective film was prepared to have a width of 25 mm and a length of 100 mm to prepare a sample. Then, the release liner was peeled off from the sample under an atmosphere of 23 ° C-50% RH, and the exposed pressure-sensitive adhesive layer was bonded to the glass plate. The pressure-sensitive adhesive layer was reciprocally pressed once with a 2 kg roller and held at 85 ° C for 48 hours. After sufficiently holding at room temperature, the stability of the adhesive force (peelability) at the high temperature was evaluated. Specifically, the film was manually peeled off from the glass plate to evaluate the peelability. The adhesive force was measured using a tensile tester under conditions of an angle of 180 degrees and a peeling speed of 0.3 m / min. After peeling off the film, the state of the residue of the pressure-sensitive adhesive on the glass plate was evaluated for appearance. The evaluation criteria are as follows.

⊚: easily peelable by hand, no adhesive residue (very good),

?: Relatively easily peelable by hand, no residue of the adhesive (good)

B: Relatively easy peeling by hand, and a small amount of adhesive residue (practically no problem)

X: Adhesive strength is higher than 300 mN / 25 mm and there is residual adhesive (practically problematic).

&Lt; Stability at low temperature aging &

The obtained surface protective film was prepared to have a width of 25 mm and a length of 100 mm to prepare a sample. Then, the release liner was peeled off from the sample under an atmosphere of 23 ° C-50% RH, and the exposed pressure-sensitive adhesive layer was bonded to the glass plate, and was reciprocally pressed once with a 2 kg roller and held at -20 ° C for 48 hours. And the stability of low-temperature aging of the adhesive force (adhesion property and releasability) was evaluated after being sufficiently maintained at room temperature. Specifically, as evaluation of low-temperature adhesion, the presence or absence of lifting on a glass plate of the surface protective film was visually evaluated. For the sample without lifting of the surface protective film, the film was peeled off from the glass plate by hand and evaluated for peelability. The evaluation criteria are as follows.

◎: Peeling of the surface protective film without peeling off, peeling off by hand (very good),

○: The peeling of the surface protective film is not performed, the peeling is relatively easy to peel off by hand (good)

X: Surface protection film lifted (practically problematic).

<Stability of wet heat stability>

The obtained surface protective film was prepared to have a width of 25 mm and a length of 100 mm to prepare a sample. And then kept at 60 ° C and 95% RH for one week. After sufficiently holding at room temperature, the presence or absence of whitening of the pressure-sensitive adhesive layer was visually evaluated. Thereafter, the peeling liner was peeled off from the sample under an atmosphere of 23 ° C-50% RH, the exposed pressure-sensitive adhesive layer was bonded to the glass plate, and the pressure-sensitive adhesive layer was once reciprocated with a 2 kg roller. After 20 minutes of curing, the adhesive strength was measured under the conditions of an angle of 180 degrees and a peeling speed of 0.3 m / min using a tensile tester, and stability of the adhesive strength with respect to wet heat stability was evaluated. The evaluation criteria are as follows.

⊚: The change of the adhesive force between 0 and less than 30 [mN / 25 mm] before and after the wet heat treatment time, and almost no whitening of the pressure-sensitive adhesive layer (very good)

?: The change in the adhesive force between 0 and less than 30 [mN / 25 mm] before and after the wet heat treatment time, the pressure-sensitive adhesive layer slightly whitened (very good)

?: The change of the adhesive force between 30 and less than 60 [mN / 25 mm] before and after elapse of the wet heat time, the pressure-sensitive adhesive layer being slightly whitened (good)

?: The change in the adhesive force was 60 or more and less than 90 [mN / 25 mm] before and after the wet heat treatment time, the pressure-sensitive adhesive layer was slightly whitened (practically no problem)

X: The change in adhesive force before and after elapse of the wet heat time was 90 or more [mN / 25 mm], and the pressure-sensitive adhesive layer was whitened (there was a practical problem).

<Wettability>

The obtained surface protective film was prepared to have a width of 25 mm and a length of 100 mm and used as a sample. Then, the release liner was peeled from the measurement sample, and both ends of the surface protective film were held with both hands, and the center of the exposed adhesive layer was brought into contact with the glass plate, and then both hands were released. The wettability of the pressure-sensitive adhesive was evaluated by measuring the time until the entire pressure-sensitive adhesive layer was brought into close contact with the glass plate by the magnetic load of the surface protective film. The shorter the time until the surface protective film comes into close contact with the glass plate, the higher the wettability and practicality for surface protection. The evaluation criteria are as follows.

⊚: Less than 3 seconds until good adhesion (good)

○: from 3 seconds to less than 4 seconds until close contact (practically no problem)

X: Wetting does not spread for more than 4 seconds till close contact (practically problematic).

<Punching workability>

The obtained surface protective film was prepared in a size of 100 mm in width and 100 mm in length and used as a sample. The punching performance was evaluated by punching 50 shots continuously with a round Thomson knife having a diameter of 10 mm by using a punching machine (SA1008 small punching machine type III (manufactured by Tester Industries Co., Ltd.).

⊚: The peeling liner of the punched circular portion can be peeled off lightly (very good) without sticking residue on the knife,

○: Although a sticky residue is slightly attached to the knife, it is possible to peel off the peeling liner of the punched circular portion neatly (good)

?: There is a little resistance (practically no problem) when the adhesive of the knife partially adheres to the knife or peeled off the peeled paper of the punched circular part,

X: The resistance when the adhesive is remarkably adhered to the knife or when the peeling paper of the punched circular portion is peeled off is large (practically problematic).

<Coating property>

The re-peelable pressure-sensitive adhesive thus obtained was coated on a 50 μm thick PET substrate (430 mm in width, manufactured by Lumirra T60 Dorayas Co., Ltd.) so as to have a thickness of 100 μm after drying and dried by heating to obtain a release liner (250010BD, manufactured by Fujimori Kogyo Co., Ltd., 430 mm width), and wound on a 6-inch ABS core by 100 m. The coating and drying conditions are as follows. Coating width 400 mm, coating speed 1.0 m / min, oven length 4 m, heating temperature 130 캜. After heating and drying, the surface of the pressure-sensitive adhesive layer was visually observed to evaluate the coatability.

(A) Whether there is a cluster or a stain

?: Cracking per 400 mm × 500 mm, no more than 2 dirts (good)

○: 400 to 500 mm, 2 to 4 unevenness and unevenness (practically no problem)

×: 5 or more unevenness and unevenness per 400 mm × 500 mm (problems in practice)

(B) presence or absence of coating line marks

&Amp; cir &amp;: No coating line marks observed at a width of 400 mm (less than or equal to 0)

∘: one coating line mark observed at a width of 400 mm (practically no problem)

X: 2 or more coating line marks observed at a width of 400 mm (practically problematic).

<Long-term wet heat storage>

The obtained releasable pressure-sensitive adhesive was coated on a 50 μm-thick PET substrate (430 mm width, manufactured by Lumirra T60 Doresa Co., Ltd.) so as to have a thickness of 100 μm after drying, followed by heating and drying to obtain a release liner (250010BD, manufactured by Fujimori Kogyo Co., Ltd., 430 mm width), and wound on a 6-inch ABS core by 100 m. The coating and drying conditions are as follows. Coating width 400 mm, coating speed 1.0 m / min, oven length 4 m, heating temperature 130 캜.

Subsequently, after leaving for one week at 23 ° C-50%, the surface protective film was slit to a width of 380 mm and wound around a 3-inch ABS core to obtain a surface protective film roll. The film was allowed to stand for one month under an environment of 40 ° C-90% RH, and the end portion of the surface protective film roll was visually observed to confirm whether or not the ester compound had escaped. In addition, the change in color was also confirmed. The evaluation criteria are as follows.

&Amp; cir &amp;: no change before time lapse (good),

?: The surface protective film slightly yellowed compared to before the elapse of time (practically no problem)

X: yellowing occurred on the surface protective film as compared with before the elapse of time, and the ester compound escaped from the end portion (practically problematic).

[Evaluation results]

The evaluation results are shown in Table 3.

As shown in Table 3, in Examples 1 to 33, a surface protective film excellent in re-peelability, wet heat resistance and wettability and excellent punching workability was obtained.

When the amount of the polyester polyol in the urethane resin raw material polyol is 50 mass% or more and the amount of the polyester diol in the polyester polyol is 20 mass% or more, the punching workability is particularly excellent. In addition, when antioxidants and antioxidants were used in combination with moisture release or ultraviolet absorber, storage of long-term wet heat was excellent.

[Table 1]

[Table 2]

[Table 3]

This application claims priority based on Japanese Patent Application No. 2016-028697, filed on February 18, 2016, and incorporates all of its publications therein.

Claims (5)

A urethane resin, a curing agent, an ester compound (except for urethane resin) and a deterioration inhibitor which are reaction products of a polyol and a polyisocyanate,
Wherein the polyol contains 50% by mass or more of a polyester polyol in 100% by mass of the total polyol.
The re-peelable pressure-sensitive adhesive according to claim 1, wherein the polyester polyol comprises 20 mass% or more of a polyester diol in 100 mass% of the total polyester polyol.
The re-peelable pressure-sensitive adhesive according to claim 1 or 2, wherein the deterioration inhibitor is at least one selected from the group consisting of an antioxidant, an anti-moisture release agent, an ultraviolet absorber and a light stabilizer.
The re-peelable pressure-sensitive adhesive according to claim 1 or 2, wherein the polyester polyol has a number average molecular weight of 500 to 5,000.
A surface protective film comprising a substrate and a pressure-sensitive adhesive layer comprising a cured product of the re-peelable pressure-sensitive adhesive according to claim 1 or 2.