CN107090265B

CN107090265B - Re-peelable adhesive and surface protective film

Info

Publication number: CN107090265B
Application number: CN201710080299.XA
Authority: CN
Inventors: 青谷朋之; 入江刚史
Original assignee: Toyo Ink SC Holdings Co Ltd; Toyochem Co Ltd
Current assignee: Toyochem Co Ltd; Artience Co Ltd
Priority date: 2016-02-18
Filing date: 2017-02-15
Publication date: 2021-03-12
Anticipated expiration: 2037-02-15
Also published as: KR20170097555A; KR102598844B1; JP6172312B1; JP2017145333A; CN107090265A

Abstract

The invention provides a removable adhesive which is excellent in removability, moist heat resistance and wettability, and further excellent in punching processability. The removable adhesive comprises a polyurethane resin which is a reaction product of a polyol and a polyisocyanate, a curing agent, an ester compound, and a deterioration inhibitor, wherein the ester compound does not include the polyurethane resin, and wherein the polyol contains 50 mass% or more of the polyester polyol in 100 mass% of the total polyol.

Description

Re-peelable adhesive and surface protective film

Technical Field

The present invention relates to a removable adhesive and a surface protective film using the same.

Background

The surface protective film has a function of being peelable after being stuck, and is preferably used for surface protection of electronic components, displays, and substrates used in the production process thereof. For example, in the manufacture of liquid crystal displays, they are used for surface protection purposes to prevent breakage of the glass surface. The surface protective film is used by punching the electronic component, the display, or the like in size. When the punching is performed, the adhesive may be attached in a powdery form to the dicing blade, and the electronic component, the display, or the like may be contaminated with the adhesive residue.

Patent document 1 discloses an adhesive composition containing an acrylic resin, an isocyanate crosslinking agent, and a dimethyl silicon compound having a polyoxyalkylene group, and a surface protective film using the adhesive composition (claims 1 and 3).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-292959;

patent document 2: japanese patent laid-open publication No. 2006-182795;

patent document 3: japanese patent laid-open publication No. 2014-028876;

patent document 4: japanese patent No. 2000-073040.

Disclosure of Invention

However, the surface protective film described in patent document 1 uses an acrylic resin for the pressure-sensitive adhesive layer, and has a problem that bubbles are taken up at the interface between the pressure-sensitive adhesive layer and the adherend when used, and workability is deteriorated. Further, there is a problem that compatibility between the acrylic resin and the silicon compound is insufficient and contamination of adherend occurs. In recent years, therefore, surface protective films using a polyurethane resin having high wettability as an adhesive layer have been disclosed (patent documents 2 to 4 and the like).

In general, the performance of polyurethane-based adhesives is greatly affected by the type of polyol used. As polyol components for polyurethane adhesives, polyester polyols and polyether polyols are well known.

In general, a polyurethane-based pressure-sensitive adhesive using a polyester polyol has high cohesive force, and thus can have high removability, good processability, and the like. However, since such a polyurethane-based adhesive has a high glass transition temperature and crystallinity, the coating workability may be deteriorated due to an increase in viscosity of the resin solution. Further, the transparency or hydrolysis resistance of the obtained pressure-sensitive adhesive layer may become insufficient. In addition, the adhesive layer may become hard, and the low-temperature characteristics may be degraded.

On the other hand, when a polyether polyol is used as the polyol component, the polyurethane-based adhesive has a lower glass transition temperature, so that the coating film is soft and has good low-temperature characteristics, but the adhesive itself has a lower cohesive force, so that the adhesive tends to remain. If the crosslinking density of the binder is increased to improve the above-mentioned situation, the coating film becomes excessively hard, the viscosity decreases, the working time is shortened, problems occur during the working, and the like, and it is difficult to obtain an optimum binder.

In order to improve the above-mentioned situation, a pressure-sensitive adhesive using a polyether polyol in combination with a polyester polyol has been disclosed, but at present, the cohesive force of the pressure-sensitive adhesive itself is low, and a removable pressure-sensitive adhesive having excellent punching processability cannot be obtained.

The purpose of the present invention is to provide a removable adhesive that is excellent in removability, moist heat resistance, wettability, and punching workability, and a surface protective film using the removable adhesive.

The present inventors have intensively studied to solve the above problems, and as a result, they have found that the above problems can be solved by using a removable adhesive containing a specific urethane resin and a change-inhibiting agent, and have completed the present invention based on this finding.

That is, the removable adhesive of the present invention includes a polyurethane resin which is a reaction product of a polyol and a polyisocyanate, a curing agent, an ester compound, and a deterioration inhibitor, and the ester compound does not include the polyurethane resin, and the polyol contains 50 mass% or more of a polyester polyol in 100 mass% of the total polyol.

The surface protective film of the present invention has a base material and a pressure-sensitive adhesive layer composed of a cured product of the removable pressure-sensitive adhesive.

The present invention can provide a removable adhesive that is excellent in removability, moist heat resistance, wettability, and punching workability, and a surface protective film using the removable adhesive.

Detailed Description

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

Re-peelable adhesive

The re-releasable adhesive of the present invention comprises a polyurethane resin which is a reaction product of a polyol and a polyisocyanate, a curing agent, an ester compound, and a deterioration inhibitor, wherein the ester compound does not include the polyurethane resin, and wherein the polyol contains 50 mass% or more of a polyester polyol in 100 mass% of the polyol.

< polyurethane resin >

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

[ polyhydric alcohol ]

As a raw material polyol of the polyurethane resin, 50% by mass or more of all polyols 100% by mass is a polyester polyol. By using a polyester polyol as the main component of the raw material polyol in this manner, a polyurethane resin which is tough and excellent in abrasion resistance can be obtained, and a removable adhesive which is excellent in punching processability can be obtained. The amount of the polyester polyol in the total polyol is preferably 50 to 100% by mass, more preferably 65 to 100% by mass, even more preferably 70 to 100% by mass, and most preferably 80 to 100% by mass.

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

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

Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, butanediol, 1, 6-hexanediol, 3-methyl-1, 5-pentanediol, 3' -dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, 1, 4-butanediol, neopentyl glycol, butylethylpentanediol, glycerol, trimethylolpropane, pentaerythritol, and the like.

The polyester polyol is preferably an aliphatic polyester polyol, and particularly preferably an adipic acid polyester polyol. Further, polyester polyols obtained by using adipic acid as an acid component and ethylene glycol-based diols as polyols are preferred.

The polyester polyol is preferably a noncrystalline polyester polyol, and for example, a polyester polyol obtained using adipic acid and 3-methyl-1, 5-pentanediol is particularly preferred. The polyester polyol is amorphous and is a liquid having a low viscosity at ordinary temperature, and therefore is easy to handle, and is preferably high in hydrolysis resistance because of the presence of a methyl group derived from 3-methyl-1, 5-pentanediol.

The raw material polyol of the polyurethane resin preferably includes at least 50 mass% or more, more preferably 60 mass% or more, and still more preferably 65 mass% or more of the amorphous polyester polyol in 100 mass% of the total polyol.

The number average molecular weight of the polyester polyol is preferably 500 to 5000, more preferably 1000 to 5000, and particularly preferably 2000 to 5000. Since the number average molecular weight is 500 or more, it is easier to control the reaction during synthesis, and since the number average molecular weight is 5000 or less, it is easier to shorten the time until the reaction is completed, and it is easier to maintain the cohesive force of the pressure-sensitive adhesive layer, and further improve the removability.

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

The polyester polyol as a raw material of the polyurethane resin may preferably contain 20 mass% or more of the polyester diol, more preferably 20 to 100 mass%, further preferably 30 to 100 mass%, and particularly preferably 50 to 100 mass% of the total polyester polyol.

Since the raw material polyester polyol includes 20 mass% or more of polyester diol, the adhesive layer is prevented from becoming excessively hard due to the reaction with the curing agent, and the processability is improved. When the polyester diol is contained in an amount of 30% by mass or more, the coating property is further improved, and therefore, the polyester diol is preferable.

The number average molecular weight of the polyester diol is preferably 500 to 5000, more preferably 1000 to 5000, and particularly preferably 2000 to 5000.

As the raw material polyol, other polyols can be used in combination with the polyester polyol as desired within a range not impairing the effects of the present invention. Examples of the other polyol include polyether polyol, polycarbonate polyol, and acrylic polyol, and among them, polyether polyol is preferable.

Examples of the polyether polyol include Polyoxytetramethylene glycol (PTMG), Polyoxypropylene glycol (PPG), and Polyoxyethylene glycol (PEG).

As the polyether polyol, polyether polyols having two or three hydroxyl groups are preferred from the viewpoint of reactivity. Further, polyether polyol having a number average molecular weight of 500 to 15000 is preferable.

[ polyisocyanate ]

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

Examples of the aromatic polyisocyanate include 1, 3-phenylene diisocyanate, 4 ' -diphenyl diisocyanate, 1, 4-phenylene diisocyanate, 4 ' -diphenylmethane diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, 4 ' -toluidine diisocyanate, 2, 4, 6-triisocyanate toluene, 1, 3, 5-triisocyanate benzene, dimethoxyaniline diisocyanate, 4 ' -diphenyl ether diisocyanate, and 4, 4 ', 4 ″ -triphenylmethane triisocyanate.

Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1, 2-propylene diisocyanate, 2, 3-butylene diisocyanate, 1, 3-butylene diisocyanate, 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-diethylbenzene, 1, 4-tetramethylxylylene diisocyanate, and 1, 3-tetramethylxylylene 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-2, 6-cyclohexane diisocyanate, 4' -methylenebis (cyclohexyl isocyanate), 1, 4-bis (isocyanatomethyl) cyclohexane and 1, 4-bis (isocyanatomethyl) cyclohexane.

When the polyurethane resin is synthesized, a catalyst may be used as needed. By using a catalyst, the reaction time can be shortened. The catalyst is preferably a tertiary amine compound, an organometallic compound, or the like.

Examples of the tertiary amine compound include triethylamine, triethylenediamine, and 1, 8-diazabicyclo [5.4.0] undec-7-ene (DBU).

Examples of the organometallic compound include tin compounds and non-tin compounds.

Examples of the tin-based compound include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin oxide, tributyltin acetate, triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, and tin 2-ethylhexanoate.

Examples of the non-tin compound include titanium compounds such as dibutyltitanium dichloride, tetrabutyl titanate and butoxytitanium trichloride; lead compounds such as lead oleate, lead 2-ethylhexoate, 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; zirconium compounds such as zirconium naphthenate.

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

As a method for synthesizing a polyurethane resin, (1) a method of charging the entire amount of polyol, polyisocyanate, and if necessary, a catalyst into a flask and reacting them, or (2) a method of charging a polyol and if necessary, a catalyst into a flask and then reacting them while dropping polyisocyanate are preferable.

When the polyurethane resin is synthesized, a known solvent can be used as needed. Specific examples thereof include methyl ethyl ketone, ethyl acetate, toluene, xylene, and acetone.

The weight average molecular weight (Mw) of the polyurethane resin is preferably 3 to 40 ten thousand, and more preferably 5 to 30 ten thousand. When the weight average molecular weight is 3 ten thousand or more, the heat resistance is improved. Further, when the weight average molecular weight is 40 ten thousand or less, the removability is further improved.

The hydroxyl value of the polyurethane resin is preferably 5 to 40mgKOH/g, more preferably 5 to 35mgKOH/g, per resin solid content. When the hydroxyl value of the polyurethane resin is 5mgKOH/g or more, the adhesion is improved, and the heat resistance and the moist heat resistance are also improved. Further, when the hydroxyl value is 40mgKOH/g or less, the punching processability is improved. The hydroxyl value can be measured by titration with potassium hydroxide in accordance with JISK 0070.

< curing agent >

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

Examples of the polyfunctional isocyanate compound include polyisocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate and polymethylene polyphenyl isocyanate; adducts of the above polyisocyanate compounds with polyhydric alcohol compounds such as trimethylolpropane and/or biuret/or isocyanurate; adducts of the above polyisocyanate compounds with known polyols (polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, and the like), and the like.

Among these, polyisocyanate compounds having two or three isocyanate groups are preferable, allophanate of hexamethylene diisocyanate, isocyanurate of hexamethylene diisocyanate, trimethylolpropane adduct of hexamethylene diisocyanate, and the like are more preferable, and isocyanurate of hexamethylene diisocyanate is further preferable.

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

The polyfunctional isocyanate compound is used in an amount of preferably 1.0 to 4.0 equivalents, more preferably 1.25 to 3.75 equivalents, and still more preferably 1.5 to 3.5 equivalents, based on the hydroxyl equivalent of the polyurethane resin.

If the amount of the polyfunctional isocyanate compound is more than 4.0 equivalents based on the hydroxyl equivalent weight of the urethane resin, the urethane resin becomes too hard and the punching processability may be deteriorated due to contamination of the adhesive residue, while if it is less than 1.0 equivalent, the urethane resin becomes too soft and the adhesive residue may be generated on the adherend when the surface protective film is peeled off. By making the amount of the polyfunctional isocyanate compound used 1.0 to 4.0 equivalents relative to the hydroxyl equivalent weight of the polyurethane resin, the balance of punching workability and re-detachable workability can be more easily obtained.

< ester Compound >

The re-releasable adhesive of the present invention includes an ester compound. Wherein the case of the polyurethane resin is excluded. The ester compound functions as a plasticizer, and has a molecular weight of preferably 300 to 850, more preferably 300 to 700. When an ester compound having a molecular weight of 300 or more is used, the heat resistance is further excellent, and when an ester compound having a molecular weight of 850 or less is used, the re-peelable adhesive is excellent in low-temperature characteristics, wettability, and the like. The molecular weight is expressed in formula weight.

As the ester compound, various known ester compounds can be used depending on their compatibility with the polyurethane resin to be used. For example, monoester ester, polyester ester and ether ester are exemplified. Among them, from the viewpoint of compatibility with the polyurethane resin, a highly polar ester compound is preferable, and an ether ester compound is particularly preferable.

Examples of the ether ester-based compound include ester compounds of adipic acid and an alcohol having an ether bond, such as dibutoxyethyl adipate, di (butoxyethoxyethyl adipate), di (methoxytetraethylene glycol) adipate, di (methoxypentaethylene glycol) adipate, and (methoxytetraethylene glycol) (methoxypentaethylene glycol) adipate; ester compounds formed from azelaic acid and alcohol having ether bond such as dibutoxyethyl azelate and di (butoxyethoxyethyl azelate); ester compounds formed from an alcohol having an ether bond and sebacic acid such as dibutoxyethyl sebacate and dibutoxyethoxyethoxyethyl sebacate; ester compounds formed from an alcohol having an ether bond and an phthalic acid such as dibutoxyethylphthalate and dibutoxyethoxyethyloxyphthalate; ester compounds formed from an alcohol having an ether bond and an isophthalic acid such as dibutoxyethyl isophthalate and dibutoxyethoxyethoxyethyl isophthalate; and ester compounds containing a polyether component obtained by reacting a polyether component such as polyethylene glycol or polypropylene glycol with an acid component such as a monocarboxylic acid such as butyric acid, isobutyric acid or 2-ethylhexanoic acid or a dicarboxylic acid such as adipic acid or phthalic acid.

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

The ester compound is used in an amount of preferably 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, based on 100 parts by mass of the polyurethane resin. If the ester compound is used in an amount of 1 part by mass or more, the re-detachable property, the low temperature property and the wettability are further improved. Further, when 50 parts by mass or less is used, contamination of the adherend can be further suppressed.

< deterioration inhibitor >

The re-releasable adhesive of the present invention includes a deterioration inhibitor. This can prevent the re-releasable adhesive from being deteriorated or deteriorated under high-temperature and high-humidity environments, can suppress reduction in re-detachable property, and can reduce contamination of adherends and the like.

The content of the deterioration inhibitor 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, based on 100 parts by mass of the polyurethane resin.

As the deterioration inhibitor, at least one selected from the group consisting of a hydrolysis resistance agent, an antioxidant, an ultraviolet absorber, and a light stabilizer is preferably used. One kind of deterioration inhibitor may be used alone, two or more kinds of the same deterioration inhibitor may be used, or two or more kinds of different deterioration inhibitors may be used in combination. The use of two or more different types of deterioration inhibitors is preferable because deterioration or degradation of the ester compound under a high-temperature and high-humidity environment can be more effectively prevented, and a decrease in removability of the adhesive and a decrease in adherend contamination can be more effectively suppressed.

Examples of the combination of the deterioration inhibitor include hydrolysis resistant agent and antioxidant, hydrolysis resistant agent and ultraviolet absorber, hydrolysis resistant agent and light stabilizer, antioxidant and ultraviolet absorber, antioxidant and light stabilizer, ultraviolet absorber and light stabilizer, and the like. It is preferable that an antioxidant is contained and used in combination with a hydrolysis resistance agent or an ultraviolet absorber. More preferably, the antioxidant is used in combination with the hydrolysis resistant agent. The use of an antioxidant in combination with a hydrolysis resistant agent or an ultraviolet absorber is preferable because it is possible to more effectively prevent the ester compound from being deteriorated or deteriorated under a high-temperature and high-humidity environment, to more effectively suppress the decrease in removability of the adhesive and the contamination of adherend, and to suppress the thermal yellowing of the hydrolysis resistant agent and the ultraviolet inhibitor themselves and the coloring of the adhesive. It is also preferable to use three or more of the deterioration inhibitors in combination, and it is particularly preferable to use the hydrolysis resistance agent, the antioxidant and the ultraviolet absorber in combination.

When two or more types of deterioration inhibitors are used in combination, the total amount of the hydrolysis resistant agent, the ultraviolet absorber and the light stabilizer is preferably 10 to 400 parts by mass per 100 parts by mass of the antioxidant, whereby the hydrolysis resistant agent and the ultraviolet inhibitor themselves can be inhibited from being decomposed and thermally yellowing can be inhibited.

[ hydrolysis resistance agent ]

The urethane adhesive preferably contains a hydrolysis resistant agent in order to block carboxyl groups generated when hydrolysis occurs in a high-temperature and high-humidity environment.

The hydrolysis resistance agent is selected from carbodiimide-based, isocyanate-based, oxazoline-based and epoxy-based ones, for example. Among these, the carbodiimide type is preferable because of its high hydrolysis inhibition effect. The hydrolysis resistance agent may be used alone or in combination of two or more.

The amount of the hydrolysis resistant agent 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 part by mass, based on 100 parts by mass of the polyurethane resin.

Preferably, hydrolysis resistance agents and antioxidants are used in combination. Specifically, a combination of a carbodiimide-based hydrolysis resistance agent and a phenol-based antioxidant is preferable, and a combination of a carbodiimide-based hydrolysis resistance agent, a phenol-based antioxidant and a phosphorus-based antioxidant is more preferable. By using a hydrolysis resistance agent and an antioxidant in combination, the hydrolysis resistance can be further improved, and the decomposition of the hydrolysis resistance agent itself and thermal yellowing can be suppressed.

The carbodiimide-based hydrolysis resistant agent is a compound having at least one carbodiimide group in a molecule.

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

Examples of the polycarbodiimide compound include high molecular weight polycarbodiimides produced by decarboxylation condensation of diisocyanates in the presence of a carbodiimidization catalyst. Examples of the raw material diisocyanate include 4, 4 ' -diphenylmethane diisocyanate, 3 ' -dimethoxy-4, 4 ' -diphenylmethane diisocyanate, 3 ' -dimethyl-4, 4 ' -diphenylmethane diisocyanate, 4 ' -diphenylether diisocyanate, 3 ' -dimethyl-4, 4 ' -diphenylether diisocyanate, 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, 1-methoxyphenyl-2, 4-diisocyanate, isophorone diisocyanate, 4 ' -dicyclohexylmethane diisocyanate, tetramethylxylylene diisocyanate, and the like. Examples of the carbodiimidization catalyst include 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-2-phospholene-1-oxide, and phospholene oxides such as 3-phospholene isomers of the above compounds.

The carbodiimide-based hydrolysis resistant agent is more preferable because the better the compatibility with the polyurethane resin, the better the effect of suppressing hydrolysis. From this viewpoint, a hydrophilic carbodiimide-based hydrolysis resistant agent is preferable, and a carbodiimide-based hydrolysis resistant agent partially or completely dissolved in water is preferable. By using a hydrophilic carbodiimide-based hydrolysis resistance agent, a substance having particularly excellent wet heat stability over time can be obtained.

Examples of the isocyanate-based hydrolysis resistant agent include 2, 4-tolylene diisocyanate, 2, 6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4 '-diphenylmethane diisocyanate, 2' -diphenylmethane diisocyanate, 3 '-dimethyl-4, 4' -biphenylene diisocyanate, 3 '-dimethoxy-4, 4' -biphenylene diisocyanate, 3 '-dichloro-4, 4' -biphenylene diisocyanate, 1, 5-naphthalene diisocyanate, 1, 5-tetrahydronaphthalene diisocyanate, tetramethylene diisocyanate, 1, 6-hexamethylene diisocyanate, and the like, Dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, 1, 3-cyclohexylene diisocyanate, 1, 4-cyclohexylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4 ' -dicyclohexylmethane diisocyanate, 3 ' -dimethyl-4, 4 ' -dicyclohexylmethane diisocyanate, and the like.

Examples of the oxazoline-based hydrolysis resistance agent include 2, 2 '-o-phenylenebis (2-oxazoline), 2' -m-phenylenebis (2-oxazoline), 2 '-p-phenylenebis (4-methyl-2-oxazoline), 2' -m-phenylenebis (4-methyl-2-oxazoline), 2 '-p-phenylenebis (4, 4' -dimethyl-2-oxazoline), 2 '-m-phenylenebis (4, 4' -dimethyl-2-oxazoline), 2 '-ethylenebis (2-oxazoline), 2' -tetramethylenebis (2-oxazoline), 2, 2 '-hexamethylenebis (2-oxazoline), 2' -octamethylenebis (2-oxazoline), 2 '-ethylenebis (4-methyl-2-oxazoline), 2' -diphenylenebis (2-oxazoline), and the like.

Examples of the epoxy hydrolysis resistant agent include diglycidyl ethers of aliphatic diols such as 1, 6-hexanediol, neopentyl glycol, and polyalkylene glycol; polyglycidyl ethers of aliphatic polyhydric alcohols such as sorbitol, sorbitan, polyglycerol, pentaerythritol, diglycerol, glycerol, and trimethylolpropane; polyglycidyl ethers of alicyclic polyols such as cyclohexanedimethanol; diglycidyl esters or polyglycidyl esters of aliphatic or aromatic polycarboxylic acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, trimellitic acid, adipic acid, and sebacic acid; diglycidyl ethers or polyglycidyl ethers of polyhydric phenols such as resorcinol, bis (p-hydroxyphenyl) methane, 2, 2-bis (p-hydroxyphenyl) propane, tris (p-hydroxyphenyl) methane, and 1, 1, 2, 2-tetrakis (p-hydroxyphenyl) ethane; n-glycidyl derivatives of amines such as N, N-diglycidylaniline, N-diglycidyltoluidine, and N, N' -tetraglycidyl-bis (p-aminophenyl) methane; triglycidyl derivatives of aminophenols (アミノフェール); triglycidyl tris (2-hydroxyethyl) isocyanurate, triglycidyl isocyanurate; o-cresol novolac type epoxides; phenol novolac type epoxy compounds, and the like.

[ antioxidant ]

If the urethane resin is thermally degraded, the compatibility with the ester compound is lowered, and the ester compound is likely to bleed out, so that it is preferable to use an antioxidant. Examples of the antioxidant include a radical scavenger and a peroxide decomposer. Examples of the radical scavenger include phenol compounds and amine compounds. Examples of the peroxide decomposer include sulfur compounds and phosphorus compounds. In particular, a phenol compound having an action as a radical scavenger is preferable in terms of thermal stability and antioxidant effect. The use of a phenol compound is preferable because it is more excellent in properties such as high-temperature stability over time, thermal and humid stability over time, and long-term thermal and humid storage property (for the evaluation method of these properties, see [ examples ]). Further, it is more preferable to use a phenol compound in combination with a phosphorus compound having an action as a peroxide decomposer because thermal stability is effectively improved. More preferably, the phenolic compound is used in combination with a phosphorus compound and a hydrolysis resistance agent as an antioxidant. This can more effectively prevent thermal degradation of the polyurethane resin and can more effectively suppress bleeding of the ester compound.

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 part by mass, based on 100 parts by mass of the polyurethane resin.

Examples of the phenolic compound include 2, 6-di-t-butyl-p-cresol, butylhydroxyanisole, 2, 6-di-t-butyl-4-ethylphenol, stearin- β - (3, 5-di-t-butyl-4-hydroxyphenyl) propionate, 2 '-methylenebis (4-methyl-6-t-butylphenol), 2' -methylenebis (4-ethyl-6-t-butylphenol), 4 '-thiobis (3-methyl-6-t-butylphenol), 4' -butylidenebis (3-methyl-6-t-butylphenol), 3, 9-bis [1, 1-dimethyl-2- [ β - (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy ] ethyl ] -2, 4, 8, 10-tetraoxaspiro [5.5] undecane, 1, 3-tris (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1, 3, 5-trimethyl-2, 4, 6-tris (3, 5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis [ methylene-3- (3 ', 5 ' -di-t-butyl-4 ' -hydroxyphenyl) propionate ] methane, ethylene glycol bis [3, 3 ' -bis (4 ' -hydroxy-3 ' -t-butylphenyl) butyrate ] and 1, 3, 5-tris (3 ', 5 ' -di-t-butyl-4 ' -hydroxybenzyl) -S-triazine-2, 4, 6- (1H, 3H, 5H) trione, Tocopherols, and the like.

Examples of the phosphorus-based antioxidant include triphenyl phosphite, diphenylisodecyl phosphite, 4' -butylidenebis (3-methyl-6-t-butylphenyl ditridecyl) phosphite, cyclopentanetetraylbis (octadecyl phosphite), tris (nonylphenyl) phosphite, tris (monononylphenyl) phosphite, tris (dinonylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10- (3, 5-di-t-butyl-4-hydroxybenzyl) -9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-decyloxy-9, 10-dihydro-9-oxa-10-phosphaphenanthrene, tris (2, 4-di-t-butylphenyl) phosphite, cycloneopentanetetraylbis (2, 6-di-t-butyl-4-methylphenyl) phosphite, and 2, 2-methylenebis (4, 6-di-t-butylphenyl) octyl phosphite, and the like.

[ ultraviolet absorbers ]

Examples of the ultraviolet absorber include benzophenone compounds, benzotriazole compounds, salicylic acid compounds, oxalanilide 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 polyurethane resin.

[ light stabilizer ]

Examples of the light stabilizer include hindered amine compounds and hindered piperidine 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 part by mass, based on 100 parts by mass of the polyurethane resin.

< leveling agent >

Preferably, the re-releasable adhesive of the present invention further comprises a leveling agent. Since a polyurethane resin having a high proportion of a polyester polyol in a raw material polyol has high polarity and high surface energy, the affinity with a low-polarity solvent such as toluene used as a reaction solvent or a diluting solvent may be reduced, and the leveling property of a coating film in a drying step may be insufficient. If the leveling property of the adhesive is insufficient, appearance defects such as shrinkage (Cissing), unevenness, and coating streaks may occur when the adhesive is coated.

In the polyurethane adhesive of the present invention, the content ratio of the leveling agent 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 part by mass, relative to 100 parts by mass of the polyurethane resin.

In the polyurethane adhesive of the present invention, by adjusting the content ratio of the leveling agent to be within the above range, contamination of an adherend can be further reduced, and at the same time, sufficient leveling property can be secured, and a smooth coating film can be obtained. The leveling agent to be used may be only one kind, or two or more kinds.

As the leveling agent, any appropriate leveling agent can be used within a range not impairing the effects of the present invention. Examples of the leveling agent include an acrylic leveling agent, a fluorine leveling agent, and a silicon leveling agent. The acrylic leveling agent is preferable because contamination of an adherend can be further reduced.

The weight average molecular weight (Mw) of the leveling agent is preferably 500 to 20000, more preferably 1000 to 15000, and further preferably 2000 to 10000. When the weight average molecular weight (Mw) is 500 or more, the amount of the vaporized component can be suppressed to a low level when the binder is applied and then heated and dried, and contamination of the drying oven by the vaporized component can be suppressed. When the weight average molecular weight (Mw) is 20000 or less, the high molecules are entangled with each other and the molecule movement is not inhibited, thereby improving the leveling property.

< antistatic agent >

The polyurethane adhesive of the present invention may further include an antistatic agent, as needed. Since the antistatic agent is included, when the antistatic agent is used as a surface protective film, troubles of electronic equipment and the like due to static electricity generated at the time of peeling can be suppressed.

As the antistatic agent, inorganic salts, polyol compounds, ionic liquids and the like are preferable, and among them, ionic liquids are more preferable. The "ionic liquid" is also referred to as an ambient temperature molten salt, and is a salt having fluidity at 25 ℃.

Examples of the inorganic salt include sodium chloride, potassium chloride, lithium perchlorate, ammonium chloride, potassium chlorate, aluminum chloride, copper chloride, ferrous chloride, ferric chloride, ammonium sulfate, potassium nitrate, sodium carbonate, and sodium thiocyanate.

Examples of the polyol compound include propylene glycol, butylene glycol, hexylene glycol, polyethylene glycol, trimethylolpropane, pentaerythritol, and the like.

Examples of the imidazolium ion-containing ionic liquid include 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1, 3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide, and 1-butyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide.

Examples of the pyridinium ion-containing ionic liquid include 1-methylpyridinium bis (trifluoromethylsulfonyl) imide, 1-butylpyridinium bis (trifluoromethylsulfonyl) imide, 1-hexylpyridinium bis (trifluoromethylsulfonyl) imide, 1-octylpyridinium bis (trifluoromethylsulfonyl) imide, and 1-hexyl-4-methylpyridinium bis (trifluoromethylsulfonyl) imide, 1-hexyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium bis (trifluoromethylsulfonyl) imide, 1-octyl-4-methylpyridinium bis (fluorosulfonyl) imide, 1-methylpyridinium bis (perfluoroethylsulfonyl) imide, 1-methylpyridinium bis (perfluorobutylsulfonyl) imide and the like.

Examples of the ammonium ion-containing ionic liquid include trimethylheptylammonium bis (trifluoromethanesulfonyl) imide, N-diethyl-N-methyl-N-propylammonium bis (trifluoromethanesulfonyl) imide, N-diethyl-N-methyl-N-pentylammonium bis (trifluoromethanesulfonyl) imide, N-diethyl-N-methyl-N-heptylammonium bis (trifluoromethanesulfonyl) imide, and tri-N-butylmethylammonium bis (trifluoromethanesulfonyl) imide.

In addition, 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.

The antistatic agent is preferably added in an amount of 0.01 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, based on 100 parts by mass of the polyurethane resin.

The re-releasable adhesive of the present invention may further contain additives such as a silane coupling agent, a colorant, an antifoaming agent, a wetting agent, a weather resistant stabilizer, a softening agent, a curing accelerator, and a curing retarder, as required.

Surface protective film

The surface protective film of the present invention has a base material and a pressure-sensitive adhesive layer composed of a cured product of the re-releasable pressure-sensitive adhesive of the present invention. The adhesive layer may be formed on one side or both sides of the substrate.

As methods for producing a surface protective film using the re-releasable adhesive of the present invention, (1) a method in which a re-releasable adhesive is applied to a release liner and heat-dried to form an adhesive layer, and then a substrate is joined, (2) a method in which a re-releasable adhesive is applied to a substrate and heat-dried to form an adhesive layer, and then a release liner is joined, and the like are conventional methods. In addition, generally, until immediately before the surface protective film is used, the adhesive layer is protected by a release liner.

Examples of the coating method of the removable adhesive include a roll coating method, a comma coating method, a lip coating method, a die gap coating method, a reverse coating method, a screen printing method, and a gravure coating method. After coating, the coating is usually dried by heating using a hot air oven, an infrared heater, or the like.

The thickness of the removable pressure-sensitive adhesive layer (thickness after drying) is usually about 1 to 200. mu.m, preferably about 5 to 100. mu.m, and more preferably about 10 to 100. mu.m.

As the substrate, a common material as a binder substrate of nonwoven fabric, paper, plastic, synthetic paper, and the like can be used, and plastic is preferable.

Examples of the plastic include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, Polyphenylene sulfide (PPS), triacetyl cellulose, cycloolefin, polyimide, polyamides such as nylon, and the like, and among them, polyethylene terephthalate is preferable.

The substrate may be subjected to an easy-adhesion treatment in advance in order to improve adhesion to the adhesive layer. The easy adhesion treatment method includes a dry method of performing corona discharge and a wet method of applying an anchor coating agent. The thickness of the base material is usually about 5 to 1000. mu.m.

The substrate may have an antistatic layer. The antistatic layer includes a resin and an antistatic agent. As the antistatic agent, in addition to the above-exemplified antistatic agents, conductive carbon particles, conductive metal particles, conductive polymers, and the like are preferable. For the antistatic layer, it can also be formed by evaporating, sputtering or plating a metal on the substrate.

The release liner is generally provided with a release layer formed by applying a release agent to a substrate such as paper, plastic, or synthetic paper. Examples of the release agent include silicone resins, alkyd resins, melamine resins, fluorine resins, and acrylic resins. The release liner is generally about 10 to 150 μm thick.

[ examples ]

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. Hereinafter, "part" means "part by mass" and "%" means "% by mass" unless otherwise specified.

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

(weight average molecular weight (Mw) of resin)

The weight average molecular weight was measured under the following conditions. The weight average molecular weight is a polystyrene-equivalent weight average molecular weight determined by Gel Permeation Chromatography (GPC). The measurement conditions are as follows.

The device comprises the following steps: shimadzu research (product name, manufactured by Shimadzu corporation, Japan);

a chromatographic column: three Tosoh TSK-GEL GMHXL (manufactured by Tosoh, Inc., of imperial China, Inc.; Bao ソー, Japan) were connected in series;

solvent: tetrahydrofuran;

flow rate: 0.5 ml/min;

temperature of the solvent: 40 ℃;

sample concentration: 0.1 mass%;

sample injection amount: 100 μ l.

(viscosity of resin)

The measurement of viscosity was carried out according to JIS Z8803 under the following conditions.

The device comprises the following steps: type B viscometer, TVB10M (product name, eastern industries co.);

a rotor: number 3;

rotation speed: 12 rpm;

measuring temperature: at 25 ℃.

(hydroxyl value)

As shown below, the measurement was carried out by a neutralization titration method in accordance with JIS K0070. First, a total amount of 25g of acetic anhydride was taken and placed in a100 ml flask, pyridine was added to make the total amount 100ml, and the mixture was thoroughly shaken and mixed to prepare an acetylating reagent. The resulting acetylation reagent was kept in a brown bottle to protect it from moisture, carbon dioxide and acid vapors. Then, a sample was taken in a flat bottom flask, and the entire amount of 5ml of acetylation reagent was added to the flat bottom flask using a pipette. Then, a small funnel was placed on the flask mouth, and the bottom of the flask was immersed in a glycerol bath at 95 to 100 ℃ for about 1cm, followed by heating. In addition, in this process, in order to prevent the bottleneck portion from being heated by the glycerin bath and the temperature from rising, a round cardboard with a circular hole opened at the center portion was covered at the root of the bottleneck portion. After 1 hour of initial heating, the flask was taken out of the glycerin bath, cooled, and then 1ml of water was added from the funnel, followed by shaking to decompose acetic anhydride. Further, in order to completely decompose the reaction mixture, the flask was again heated in a glycerin bath for 10 minutes in the same manner as described above, and after cooling, the inner walls of the flask and the funnel were washed with 5ml of ethanol. After several drops of phenolphthalein solution were added as an indicator, titration was performed with 0.5mol/l potassium hydroxide ethanol solution, and the end point was a time point at which the light red color of the indicator lasted for about 30 seconds. Further, a blank test without adding a sample was performed in the same manner as described above. Then, the hydroxyl value of the polyurethane resin (solid content) was calculated from the following formula.

(B-C) × f × 28.05/S)/(nonvolatile matter concentration/100) + D (equation 1)

Wherein, in (equation 1), a: hydroxyl value (mgKOH/g); b: amount (ml) of 0.5mol/l ethanolic potassium hydroxide solution used for the blank test; c: amount (ml) of 0.5mol/l potassium hydroxide ethanol solution used for titration; f: factor (concentration correction factor) of 0.5mol/l potassium hydroxide ethanol solution; s: mass of the sample (g); d: acid value (mgKOH/g).

Next, examples of the synthesis of the polyurethane resin solutions used in the examples and comparative examples will be described.

(Synthesis example 1)

100 parts by mass of a polyester polyol P-1010 (bifunctional polyester polyol, hydroxyl value 112, number average molecular weight 1000, manufactured by Nippon Coly corporation (クラレ), 15.5 parts by mass of hexamethylene diisocyanate (manufactured by Sumitomo Bayer corporation) (manufactured by Sumitomo バイエル)), 77 parts by mass of toluene, 0.25 part by mass of dibutyltin dilaurate as a catalyst, and 0.01 part by mass of tin 2-ethylhexanoate were charged into a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet, thermometer, and dropping funnel under a nitrogen atmosphere. The flask was slowly heated to react at about 90 ℃ for 2 hours. The reaction was continued while confirming the disappearance of the isocyanate group as needed by infrared absorption (IR) spectroscopy. After confirming the disappearance of the isocyanate group, the reaction mixture was immediately cooled to complete the reaction. Then, toluene was added so that the nonvolatile content (NV) became 60%, to obtain a polyurethane resin 1 solution having a Viscosity (VIS) of 3000 mPas. The hydroxyl value (OH value) of the polyurethane resin 1 (solid content) was 7.6mgKOH/g, and the weight-average molecular weight (Mw) was 55000. The solid content (NV) and Viscosity (VIS) of the polyurethane resin solution, and the hydroxyl value (OH value) and weight average molecular weight (Mw) of polyurethane resin 1 (solid content) are shown in table 1.

(Synthesis examples 2 to 13)

In each of synthetic examples 2 to 13, solutions of polyurethane resins 2 to 13 were obtained in the same manner as in synthetic example 1 except that the raw materials and the amounts to be blended were changed as shown in table 1. The solid content (NV) and Viscosity (VIS) of the polyurethane resin solution, and the hydroxyl value (OH value) and weight average molecular weight (Mw) of the polyurethane resin are shown in table 1.

[ example 1]

With respect to 100 parts by mass of the urethane resin in the urethane resin 1 solution obtained in synthesis example 1, 5.4 parts by mass of an isocyanurate-modified hexamethylene diisocyanate (product name Coronate (コロネート) HX, non-volatile matter of 100% by mass, NCO% ═ 21.0) as a curing agent, 30 parts by mass of bis (dibutoxyethyl adipate) as an ester compound (product name D931, non-volatile matter of 100% by mass, molecular weight 346), 0.8 parts by mass and 0.05 parts by mass of a phenol-based antioxidant (product name IRGANOX1010, non-volatile matter of 100% by mass) as an antioxidant and a phosphorus-based antioxidant (product name BASF ジャパン (product name) as an antioxidant, each of which are manufactured by japan, a carbodiimide (trade name IRGAFOS168, nonvolatile component 100 parts by mass) as a hydrolysis resistance agent (product name Carbodilite (カルボジライト) V-09GB, nonvolatile component 75 parts by mass%) in terms of solid content, 0.1 part by mass in terms of solid content, a triazine-based ultraviolet absorber (product name Tinuvin (チヌビン)477, nonvolatile component 80 parts by mass) as an ultraviolet inhibitor, 0.2 part by mass, a hindered amine-based light stabilizer (product name Tinuvin (チヌビン)123, nonvolatile component 100 parts by mass%) as a light stabilizer, and 5 parts by mass of ethyl acetate as a solvent were mixed together and stirred by a dispersing machine to obtain a polyurethane adhesive.

The polyurethane adhesive was applied to a 50 μm thick Polyethylene terephthalate (PET) substrate (ルミラー T60, manufactured by Toray レ) so that the thickness after drying became 50 μm, and after drying at 100 ℃ for 4 minutes, a 25 μm release liner (250010BD, manufactured by Tanson industries, Ltd.) was bonded. Then, the mixture was left at 23 ℃ and-50% for one week to obtain a surface protective film.

Examples 2 to 33 and comparative examples 1 to 4

Polyurethane adhesives and surface protective films were obtained in the same manner as in example 1, except that the raw materials and the amounts of the components were changed as shown in table 2 in examples 2 to 33 and comparative examples 1 to 4.

The surface protective films obtained in the respective examples and comparative examples were evaluated as follows.

< glass adhesion >

The obtained surface protective film was prepared into a size of 25mm in width and 100mm in length as a sample. Then, the release liner was peeled from the sample at 23 ℃ and-50% RH, the exposed adhesive layer was bonded to a glass plate, and the resultant was repeatedly pressed and adhered once with a 2kg roller and left for 24 hours, and then the adhesion was measured using a tensile tester under conditions of a peel angle of 180 degrees and a peel speed of 0.3 m/min. In general, a surface protective film that has lower adhesion to glass and is more easily peeled off again has higher utility as a surface protective film.

< high temperature stability over time >

The obtained surface protective film was prepared into a size of 25mm in width and 100mm in length as a sample. Then, the release liner was peeled from the sample at 23 ℃ and-50% RH, and the exposed adhesive layer was bonded to a glass plate, and the glass plate was subjected to reciprocal pressure bonding with a 2kg roller and held at 85 ℃ for 48 hours. After sufficiently retaining at room temperature, the high-temperature stability of the adhesive force (releasability) was evaluated. Specifically, the film was peeled from the glass plate by hand, and the peelability was evaluated. For a film that could not be easily peeled by hand, the adhesion was measured using a tensile tester under conditions of a peeling angle of 180 degrees and a peeling speed of 0.3 m/min. Further, the state of adhesive residue on the glass plate after the film was peeled was visually evaluated. The evaluation criteria are as follows.

Very good: easy peeling by hand, no adhesive residue (very good);

o: can be peeled off by hand relatively simply, without adhesive residue (good);

and (delta): the adhesive can be easily peeled off by hand, and the adhesive has little adhesive residue (no practical problem);

x: the adhesive force was higher than 300mN/25mm, or adhesive residue was present (there was a practical problem).

< Low temperature stability over time >

The obtained surface protective film was prepared into a size of 25mm in width and 100mm in length as a sample. Then, the release liner was peeled from the sample at 23 ℃ and-50% RH, and the exposed adhesive layer was bonded to a glass plate, and the glass plate was subjected to reciprocal pressure bonding with a 2kg roller and held at-20 ℃ for 48 hours. After sufficiently retaining at room temperature, the low-temperature stability of the adhesive force (adhesiveness, releasability) was evaluated. Specifically, as evaluation of low-temperature adhesiveness, the presence or absence of floating matter from the glass plate on the surface protective film was visually evaluated. For the sample having no floating matter in the surface protective film, the film was peeled from the glass plate by hand, and the peeling property was also evaluated. The evaluation criteria are as follows.

Very good: the surface protective film had no floating matter and was easily peeled off by hand (very good);

o: the surface protective film has no floating matter and can be easily peeled off (good) by hand;

x: the surface protective film has floating matter (there is a practical problem).

< stability of Damp Heat over time >

The obtained surface protective film was prepared into a size of 25mm in width and 100mm in length as a sample. Then, the mixture was kept at 60 ℃ and-95% RH for one week. After sufficiently holding at room temperature, the pressure-sensitive adhesive layer was visually evaluated for the presence or absence of whitening. Next, the release liner was peeled from the sample under an environment of 23 to 50% RH, the exposed adhesive layer was bonded to a glass plate, pressure-welded once with a 2kg roller in a reciprocating manner, and after curing for 20 minutes, the adhesion was measured under conditions of a peel angle of 180 degrees and a peel speed of 0.3m/min using a tensile tester, and the wet-heat aging stability of the adhesion was evaluated. The evaluation criteria are as follows.

Very excellent: the change of the adhesion force before and after wet heat treatment is more than 0 and less than 30 mN/25mm,

And the adhesive layer is substantially free of whitening (excellent);

very good: the change of the adhesion force before and after wet heat treatment is more than 0 and less than 30 mN/25mm,

And the adhesive layer was slightly whitened (very good);

good: the change of the adhesive force before and after wet heat treatment is more than 30 and less than 60 mN/25mm,

And the adhesive layer was slightly whitened (good);

and (delta): the change of the adhesive force before and after wet heat treatment is more than 60 and less than 90 mN/25mm,

And the adhesive layer was slightly whitened (no practical problem);

x: the change of the adhesive force before and after wet heat treatment is more than 90 mN/25mm,

And the adhesive layer has whitening (there is a practical problem).

< wettability >

The obtained surface protective film was prepared into a size of 25mm in width and 100mm in length as a sample. Then, the release liner was peeled off 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 to separate both hands. The time until the entire adhesive layer was adhered to the glass plate by the weight of the surface protective film itself was measured, and the wettability of the adhesive was evaluated. The shorter the time until the surface protective film is adhered to the glass plate, the higher the wettability is, and the higher the practicability as a surface protective film for use is. The evaluation criteria are as follows.

Very good: until adhesion, less than 3 seconds (good);

o: 3 seconds or more and less than 4 seconds until the adhesive is adhered (no practical problem);

x: until the adhesive was adhered, the wetting did not spread for 4 seconds or more (there was a practical problem).

< punching workability >

The obtained surface protective film was prepared into a size of 100mm in width and 100mm in length as a sample. Punching was continuously performed by 50 punches by a circular thomson knife (トムソン blade) having a diameter of 10mm using a punching machine (model III of SA1008 mini-punch (manufactured by japan tester corporation, テスター)), and punching workability was evaluated. The evaluation criteria are as follows.

Very good: adhesive residue did not adhere to the knife and the release liner of the punched round part could be peeled off cleanly and lightly (very well);

o: a small amount of adhesive residue adhered to the knife but was able to peel cleanly and lightly the release liner of the die-cut rounded portion (good);

and (delta): a small amount of resistance (no practical problem) is generated when a part of the adhesive residue adheres to the blade or when the release paper of the punched round part is peeled off;

x: the adhesive is attached to the blade or the resistance is large when the release paper of the punched round portion is peeled (there is a problem in practical use).

< coatability >

The obtained re-releasable adhesive was applied to a PET substrate (ルミラー T60, manufactured by Toray corporation, 430mm in width) having a thickness of 50 μm so as to have a thickness after drying of 100 μm using a test coater, and then heated and dried, a 25 μm release liner (250010BD, manufactured by Tenson industries, 430mm in width) was bonded thereto, and the resultant was wound up on a 6-inch Acrylonitrile-Butadiene-Styrene (ABS) core by 100 m. The coating and drying conditions are as follows. The coating width was 400mm, the coating speed was 1.0 m/min, the oven length was 4m, and the heating temperature was 130 ℃. The coatability was evaluated by visually observing the surface of the pressure-sensitive adhesive layer after heat drying.

(A) Presence or absence of shrinkage and unevenness

Very good: shrinkage/unevenness was 2 or less per 400mm × 500mm (good);

o: every 400mm is multiplied by 500mm, the shrinkage and the unevenness are 2-4 (no practical problem);

x: the number of the shrinkages and unevenness was 5 or more per 400mm × 500mm (there was a practical problem).

(B) Presence or absence of coating streaks

Very good: coating streaks observed at a width of 400mm were 0 or less (good);

o: the number of coating streaks observed at a width of 400mm was 1 (no practical problem);

x: the number of coating streaks observed at a width of 400mm was 2 or more (there was a practical problem).

< Long-term Wet Heat storage >

The obtained re-releasable adhesive was applied to a PET substrate (ルミラー T60, manufactured by Toray corporation, 430mm in width) having a thickness of 50 μm using a test coater so that the thickness after drying became 100 μm, and was dried by heating, a 25 μm release liner (250010BD, manufactured by Tanson industries, 430mm in width) was bonded to the substrate, and the substrate was wound up by 100m on a 6-inch ABS die. The coating and drying conditions are as follows. The coating width was 400mm, the coating speed was 1.0 m/min, the oven length was 4m, and the heating temperature was 130 ℃.

Then, after leaving at 23 ℃ and-50% for one week, the surface protective film was slit to a width of 380mm and wound around a 3-inch ABS tube core to obtain a roll of the surface protective film. The roll of the surface protection film was left to stand at 40 ℃ and-90% RH for one month, and the end of the roll of the surface protection film was visually observed to confirm the presence or absence of the ester compound bleeding. In addition, a change in color tone was also confirmed. The evaluation criteria are as follows.

Very good: no change before time (good);

o: the surface protective film turned slightly yellow (no practical problem) as compared with the film before the lapse of time;

x: the surface protective film turns yellow and the ester compound bleeds out from the terminal portion as compared with the case before the lapse of time (there is a practical problem).

[ evaluation results ]

The evaluation results are shown in table 3.

As shown in Table 3, in examples 1 to 33, surface protective films excellent in removability, moist heat resistance and wettability and further excellent in punchability were obtained.

When the amount of the polyester polyol in the raw material polyol of the polyurethane resin is 50% by mass or more and the amount of the polyester diol in the polyester polyol is 20% by mass or more, the punching processability is particularly excellent. Further, when an antioxidant is used in combination with a hydrolysis resistant agent or an ultraviolet absorber as a deterioration inhibitor, the long-term moist heat storage property is particularly excellent.

TABLE 3

The present application is filed and claimed on the basis of japanese patent application No. 2016-.

Claims

1. A re-releasable adhesive which comprises a urethane resin as a reaction product of a polyol and a polyisocyanate, a curing agent, an ester compound and a deterioration inhibitor, wherein the ester compound does not include the urethane resin,

the molecular weight of the ester compound is 300 to 850,

the polyol contains a polyester polyol in an amount of 65 mass% or more based on 100 mass% of the total polyol,

the polyester polyol comprises 30 mass% or more of a polyester diol in 100 mass% of the total polyester polyol,

the polyester diol has a number average molecular weight of 500 to 5000,

the curing agent includes a polyfunctional isocyanate compound,

the polyfunctional isocyanate compound has 1.0 to 4.0 equivalents of isocyanate groups per 1 equivalent of hydroxyl groups of the polyurethane resin.

2. The re-peelable adhesive according to claim 1, wherein the deterioration inhibitor contains at least one selected from the group consisting of an antioxidant, a hydrolysis resistance agent, an ultraviolet absorber and a light stabilizer.

3. A surface protective film comprising a base material and a pressure-sensitive adhesive layer comprising a cured product of the re-releasable pressure-sensitive adhesive according to claim 1 or 2.