JP2017145333A - Removable adhesive and surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a removable adhesive excellent in removability, moisture heat resistance and wettability as well as excellent in punching property, and a surface protective film having the above adhesive layered thereon.SOLUTION: The removable adhesive comprises a urethane resin obtained by the reaction of polyol and polyisocyanate, a curing agent, an ester compound (excluding an ester compound that is a urethane resin), and a deterioration preventive. The polyol contains polyester polyol by 50 wt.% or more in 100 wt.% of the polyol.SELECTED DRAWING: None

Description

  The present invention relates to a re-peelable pressure-sensitive adhesive excellent in re-peelability, heat-and-moisture resistance, wettability, and excellent in punching workability, and a surface protective film formed by laminating the same.

  The surface protection film is used for surface protection when manufacturing electronic components by taking advantage of the function of being peelable after being applied. For example, when manufacturing a liquid crystal display, the surface protection film is used for surface protection to prevent breakage of the glass surface. It is used. These surface protective films are used by punching according to the size of electronic parts and displays. However, the adhesive adheres to the cutting blade in the form of powder during punching, and the electronic parts and displays are contaminated with adhesive residue. There was a problem that occurred.

  Thus, Patent Document 1 discloses a protective film containing an acrylic resin, an isocyanate crosslinking agent, and a dimethylsilicon compound having a polyoxyalkylene group.

JP 2009-292959 A JP 2006-18295 A JP 2014-028876 A Japanese Patent No. 2000-073040

  However, the conventional surface protective film uses an acrylic resin for the pressure-sensitive adhesive layer, and there is a problem that, when used, air bubbles are involved in the interface between the pressure-sensitive adhesive layer and the adherend, and workability is lowered. Further, the compatibility between the acrylic resin and the silicone compound is not sufficient, and there is a problem that adherend contamination occurs. Therefore, in recent years, a protective film using a urethane resin having high wettability as an adhesive layer has been disclosed. (Patent Document 2, Patent Document 3, Patent Document 4)

  In general, the performance of the urethane-based pressure-sensitive adhesive is greatly affected by the type of polyol used. As polyol components used for urethane pressure-sensitive adhesives, polyester polyols and polyether polyols are well known. Urethane-based adhesives using polyester polyol have high cohesive force, which results in high removability and processability, but high glass transition point and high crystallinity, thus increasing the viscosity of the resin solution. There are problems such as poor workability and transparency due to the above, and weakness to hydrolysis. Moreover, since the pressure-sensitive adhesive layer becomes hard, the low-temperature characteristics and the like were not satisfactory.

  On the other hand, when a polyether polyol is used as the polyol component, the coating film is soft because the glass transition temperature of the urethane-based pressure-sensitive adhesive is lower than that using a polyester polyol, and the low-temperature characteristics are good. Adhesive residue tends to occur because the cohesive strength of the adhesive itself is low. If the cross-linking density of the adhesive is increased to improve these, the optimal adhesive can be used, such as the coating film becoming too hard and tackiness is reduced, and the workable time is shortened and handling problems occur. It was difficult to get.

  For these improvements, a pressure-sensitive adhesive using a mixture of polyether polyol and polyester polyol is also disclosed, but a re-peeling pressure-sensitive adhesive having low cohesive strength and excellent punching processability is obtained. The current situation is not.

  An object of the present invention is to provide a re-peelable pressure-sensitive adhesive that is excellent in re-peelability, heat-and-moisture resistance, and wettability, and is excellent in punching workability, and a surface protection film formed by laminating the same.

  As a result of intensive studies to solve the above problems, the present inventors have solved the above problems by using a re-peelable pressure-sensitive adhesive containing a specific urethane resin and an alteration inhibitor. And the present invention has been made based on this finding.

  That is, the re-peelable pressure-sensitive adhesive of the present invention contains a urethane resin obtained by reacting a polyol and a polyisocyanate, a curing agent, an ester compound (excluding when it is a urethane resin), and an anti-altering agent. Is characterized by containing 50% by weight or more of polyester polyol in 100% by weight of polyol.

  According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet and a surface protective film that are excellent in removability, heat-and-moisture resistance, wettability, and excellent in punching workability by using the above-described re-peelable pressure-sensitive adhesive.

  Prior to describing the present invention in detail, terms will be defined. Sheet, film and tape are synonymous. An adherend means the other party which affixes an adhesive sheet.

  The re-peelable pressure-sensitive adhesive of the present invention has a urethane resin obtained by reacting a polyol and a polyisocyanate, a curing agent, an ester compound (excluding when it is a urethane resin), and an anti-altering agent, and the polyol However, it contains 50% by weight or more of polyester polyol in 100% by weight of polyol.

<Urethane resin>
The urethane resin of the present invention is a resin obtained by reacting a polyol and a polyisocyanate, and has a plurality of hydroxyl groups. The polyol contains 50% by weight or more of polyester polyol in 100% by weight of polyol.

[Polyol]
The polyol is composed of polyester polyol at 50% by weight or more out of 100% by weight of the total polyol constituting the urethane resin. Thus, by using a polyester polyol as a main component, it becomes a urethane resin which is tough and excellent in wear resistance, and a re-peelable pressure-sensitive adhesive excellent in punching workability can be obtained. Preferably it is 50-100 weight%, More preferably, it is 65-100 weight%, More preferably, it is 70-100 weight%, Most preferably, it is 80-100 weight%.

  The polyester polyol used in the present invention can be produced using, for example, several kinds of acid components and a polyhydric alcohol.

Examples of the acid component include terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, trimellitic acid, and among them, adipic acid is particularly preferable.
Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexane glycol, 3-methyl-1,5-pentanediol, 3,3′-dimethylol heptane, polyoxyethylene glycol, Examples of the polyoxypropylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, and polyol component include glycerin, trimethylolpropane, and pentaerythritol. Among these, an aliphatic polyester polyol is preferable, and an adipic acid-based polyester polyol is particularly preferable.

  In the present invention, a polyester polyol obtained using a glycol diol as the polyhydric alcohol is particularly preferable.

  The polyester polyol used in the present invention is preferably an amorphous polyester polyol, and for example, a polyester polyol composed of adipic acid and 3-methyl-1,5-pentanediol is particularly preferable. Since it is non-crystalline, it is liquid at room temperature and easy to handle because of its low viscosity, and the presence of the methyl group of 3-methyl-1,5-pentanediol can improve hydrolysis resistance. In 100% by weight of the total polyol contained in the urethane resin of the present invention, it is preferable to include at least 50% by weight of an amorphous polyester polyol, more preferably 60% by weight or more, and more preferably 65% by weight or more. .

  The number average molecular weight of the polyester polyol is preferably 500 to 5,000. When the number average molecular weight is 500 or more, the reaction control during the synthesis becomes easier, and when the number average molecular weight is 5,000 or less, the time until the completion of the reaction is easily shortened. The removability is further improved by easily maintaining the cohesive force.

As the polyester polyol, a polyfunctional polyester polyol having two or more hydroxyl groups in the molecule can be used. Among them, those having two or three hydroxyl groups are preferable from the viewpoint of reactivity, and two hydroxyl groups are preferably used. The polyester diol having is particularly preferable.
The total polyester polyol constituting the urethane resin of the present invention preferably contains 20% by weight or more of polyester diol in 100% by weight of the total polyester polyol. More preferably, the polyester diol is contained in an amount of 20 to 100% by weight, more preferably 30 to 100% by weight, and particularly preferably 50 to 100% by weight.

  By containing 20% by weight or more of polyester diol, the pressure-sensitive adhesive layer is prevented from becoming too hard due to reaction with the curing agent, and processability is improved. When the polyester diol is contained in an amount of 30% by weight or more, it is preferable because coatability is further improved.

In the present invention, as long as the effects of the present invention are not impaired.
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Thus, other polyols can be used in combination with the polyester polyol. For example, polyether polyol, polycarbonate polyol, or acrylic polyol can be used in combination, and among these, polyether polyol is preferable.
Examples of polyether polyols include polyoxytetramethylene glycol (PTMG), polyoxypropylene glycol (PPG), and polyoxyethylene glycol (PEG).
The polyether polyol preferably has 2 or 3 hydroxyl groups from the viewpoint of reactivity, and preferably has a number average molecular weight of 500 to 15,000.

[Polyisocyanate]
A known compound can be used as the polyisocyanate. Specifically, aromatic polyisocyanate, aliphatic polyisocyanate, araliphatic polyisocyanate, alicyclic polyisocyanate, or the like is preferable.

  Aromatic polyisocyanates include, for example, 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-triylene diisocyanate. Range isocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4 ', 4 " -Triphenylmethane triisocyanate etc. are mentioned.

  Aliphatic polyisocyanates include, for example, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2, Examples include 4,4-trimethylhexamethylene diisocyanate.

  Examples of the araliphatic polyisocyanate include ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene, , 4-tetramethylxylylene diisocyanate, 1,3-tetramethylxylylene diisocyanate, and the like.

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

  A catalyst can be appropriately used for the synthesis of the urethane resin. The reaction time can be shortened by using a catalyst. The catalyst is preferably a tertiary amine compound or an organometallic compound.

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

Examples of the organometallic compound include a tin compound and a non-tin compound.
Examples of tin compounds include dibutyltin dichloride, dibutyltin oxide, dibutyltin dibromide, dibutyltin dimaleate, dibutyltin dilaurate (DBTDL), dibutyltin diacetate, dibutyltin sulfide, tributyltin sulfide, tributyltin oxide, tributyltin acetate. , Triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, tin 2-ethylhexanoate and the like.

  Non-tin compounds include, for example, titanium compounds such as dibutyltitanium dichloride, tetrabutyltitanate, butoxytitanium trichloride; lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate, lead naphthenate; Iron compounds such as iron ethylhexanoate and iron acetylacetonate; cobalt compounds such as cobalt benzoate and cobalt 2-ethylhexanoate; zinc compounds such as zinc naphthenate and zinc 2-ethylhexanoate; Examples include zirconium acid.

  The catalyst is preferably used in an amount of about 0.01 to 1% by weight based on 100% by weight of the total of polyol and polyisocyanate. Moreover, since the reactivity changes with polyol, the catalyst suitable for each polyol can be used.

  The synthesis of the urethane resin is preferably (1) a method in which a polyol, a catalyst and polyisocyanate are charged in a total amount in a flask, and (2) a method in which a polyol and a catalyst are charged in a flask and reacted while dropping a polyisocyanate.

  A known solvent can be used for the synthesis of the urethane resin. Specific examples 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, and more preferably 50,000 to 300,000. Heat resistance improves because a weight average molecular weight becomes 30,000 or more. Moreover, when it is 400,000 or less, re-peelability improves more.

  The urethane resin in the present invention preferably has a hydroxyl value per resin solid content of 5 to 40 mgKOH / g, more preferably 5 to 35 mgKOH / g. When the hydroxyl value of the urethane resin is 5 mgKOH / g or more, the adhesive strength is improved, and the heat resistance and heat and humidity resistance are also improved. Further, when the hydroxyl value is 40 mgKOH / g or less, the punching processability is improved. In addition, the measurement of a hydroxyl value can be performed by the titration method by potassium hydroxide based on JISK0070.

<Curing agent>
The curing agent in the present invention is preferably a compound capable of reacting with the hydroxyl group of the urethane resin, and more preferably a polyfunctional isocyanate compound.
Examples of the polyfunctional isocyanate compound include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenylmethane triisocyanate. Polyisocyanate compounds such as isocyanate and polymethylene polyphenyl isocyanate, adducts of these polyisocyanate compounds with polyol compounds such as trimethylolpropane, burettes, or isocyanurates, and these polyisocyanate compounds and known Polyether polyol or polyester polyol Ol, acrylic polyol, polybutadiene polyol or an adduct such as a polyisoprene polyol and the like. Among these, polyisocyanate compounds having two or three isocyanate groups are preferable, hexamethylene diisocyanate allophanate, hexamethylene diisocyanate isocyanurate, and hexamethylene diisocyanate trimethylolpropane adduct are more preferable. More preferred are isocyanurates of diisocyanates.

  A polyfunctional isocyanate compound may be used independently or may be used in combination of 2 or more types.

The amount of the polyfunctional isocyanate compound used is preferably 1.0 to 4.0 equivalents, more preferably 1.25 to 3.75 equivalents, and more preferably 1.5 to 3 equivalents as an isocyanate group with respect to the hydroxyl equivalent of the urethane resin. More preferred is 5 equivalents.
If the amount of the polyfunctional isocyanate compound is more than 4.0 equivalents relative to the hydroxyl group equivalent of the urethane resin, the urethane resin becomes too hard and the pressure-sensitive adhesive
1455585016643_1
by
1455585016643_2
As a result, the punching processability deteriorates, and if it is less than 1.0 equivalent, the urethane resin becomes too soft, and adhesive residue may be generated on the adherend when the surface protective film is peeled off. By making the usage-amount of a polyfunctional isocyanate compound into 1.0-4.0 equivalent with respect to the hydroxyl group equivalent of the said urethane resin, it becomes easier to balance punching workability and removability.

<Ester compound>
The re-peelable pressure-sensitive adhesive in the present invention contains an ester compound. However, it is excluded when it is urethane resin. The ester compound of the present invention serves as a plasticizer and has a molecular weight of 300 to 850, preferably 300 to 700. When an ester compound having a molecular weight of 300 or more is used, the heat resistance is more excellent. On the other hand, when an ester compound having a molecular weight of 850 or less is used, low-temperature characteristics and wettability are excellent. The molecular weight is a formula weight.

As said ester compound, well-known various ester compounds can be used according to compatibility with the applied urethane resin. For example, ester system, polyester system, and ether ester are mentioned. Among these, since the polyester polyol has a higher polarity than the polyether polyol and the polarity of the urethane resin is increased, a highly polar ester compound is preferable from the viewpoint of compatibility, and an ether ester compound is particularly preferable.
For example, ether ester compounds include dibutoxyethyl adipate, di (butoxyethoxyethyl) adipate, di (methoxytetraethylene glycol) adipate, di (methoxypentaethylene glycol) adipate, and adipic acid (methoxytetraethylene). Glycol) (methoxypentaethylene glycol) and the like an ester compound of an adipic acid and an ether bond-containing alcohol; an azelaic acid dibutoxyethyl, an azelaic acid di (butoxyethoxyethyl) and the like an ester compound of an azelaic acid and an ether bond-containing alcohol; Ester compounds of sebacic acid such as dibutoxyethyl sebacate and di (butoxyethoxyethyl) sebacate and alcohols containing ether linkages; dibutoxyethyl phthalate, di (butoxy phthalate) Ester compounds of phthalic acid such as ethoxyethyl) and ether bond-containing alcohols; Ester compounds of isophthalic acid such as dibutoxyethyl isophthalate and di (butoxyethoxyethyl) isophthalate and alcohols containing ether bonds; polyethylene glycol and polypropylene glycol A polyether component easily obtained by reacting a polyether component such as butanoic acid, isobutanoic acid, monocarboxylic acid such as 2-ethylhexylic acid or a dicarboxylic acid such as adipic acid or phthalic acid The ester compound containing is mentioned.

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

  The ester compound is preferably used in an amount of 0.5 to 50 parts by weight, more preferably 1 to 40 parts by weight, and still more preferably 5 to 40 parts by weight with respect to 100 parts by weight of the urethane resin. When the ester compound is used in an amount of 1 part by weight or more, the removability, low temperature characteristics and wettability are further improved. Moreover, when it is 50 parts by weight or less, contamination of the adherend can be further suppressed.

<Anti-alteration agent>
The re-peelable pressure-sensitive adhesive in the present invention contains an alteration preventing agent. As a result, it is possible to prevent alteration or deterioration of the re-peelable pressure-sensitive adhesive in a high-temperature and high-humidity atmosphere, suppress re-peelability reduction, and decrease adherend contamination.

  The alteration inhibitor is preferably at least one selected from the group consisting of hydrolysis-resistant agents, antioxidants, ultraviolet absorbers, or light stabilizers. It can be used alone, or two or more of the same type of alteration inhibitors can be used, or two or more different types of alteration inhibitors can be used in combination, but by using two or more different types of alteration inhibitors. Further, it becomes possible to prevent the deterioration or deterioration of the ester compound in a high-temperature and high-humidity atmosphere, and it is possible to further suppress the decrease in the removability of the adhesive, the decrease in the adherend contamination, and the like.

Specifically, hydrolysis-resistant and antioxidant, hydrolysis-resistant and ultraviolet absorber, hydrolysis-resistant and light stabilizer, hydrolysis-resistant and antioxidant, hydrolysis-resistant and ultraviolet absorber, Anti-hydrolysis agent and light stabilizer, antioxidant and ultraviolet absorber, antioxidant and light stabilizer, or ultraviolet absorber and light stabilizer, etc. Preferably, antioxidant is essential , A case where a hydrolysis-resistant agent or an ultraviolet absorber is used in combination, and a case where an antioxidant and a hydrolysis-resistant agent are used in combination is more preferable. By using in combination with an antioxidant, it becomes possible to prevent alteration or deterioration of the ester compound in a high-temperature and high-humidity atmosphere, and it is possible to further suppress the decrease in removability of the adhesive, the decrease in adherend contamination, and the like. It is preferable because the hydrolytic agent and the ultraviolet light inhibitor itself can suppress thermal yellowing and can suppress coloring of the pressure-sensitive adhesive.
Moreover, the case where 3 or more types of alteration inhibitors are contained is also preferable, and the case where a hydrolysis-resistant agent, an antioxidant and an ultraviolet absorber are contained is particularly preferable.

  When two or more kinds of alteration inhibitors are contained, the total amount of the hydrolysis-resistant agent, ultraviolet absorber, or light stabilizer is preferably 10 to 400 parts by weight with respect to 100 parts by weight of the antioxidant. Thereby, decomposition | disassembly and thermal yellowing of a hydrolysis-resistant agent and an ultraviolet-ray prevention agent itself can be suppressed.

[Hydrolysis-resistant agent]
It is preferable to use a hydrolysis-resistant agent in order to block the carboxyl group generated when the urethane pressure-sensitive adhesive is hydrolyzed in a high-temperature and high-humidity atmosphere.
The hydrolysis-resistant agent is selected from, for example, carbodiimide, isocyanate, oxazoline, and epoxy systems, and carbodiimide is more preferable because it has an effect of suppressing hydrolysis more effectively. It may be used alone or in combination of two or more.
The hydrolysis resistance is preferably 0.01 to 2.0 parts by weight, more preferably 0.02 to 1.5 parts by weight, and still more preferably 0.05 to 100 parts by weight of the urethane resin. -1.0 part by weight.

  In addition, it is preferable to use the hydrolysis-resistant agent together with an antioxidant described later, specifically, a combination of a carbodiimide-based hydrolysis resistance agent and a phenol-based antioxidant is preferable, and a carbodiimide-based hydrolysis resistance agent and a phenol-based antioxidant. More preferably, an agent and a phosphorus-based antioxidant are included. By using a hydrolysis-resistant agent and an antioxidant in combination, hydrolysis resistance can be further improved, and decomposition of the hydrolysis-resistant agent itself and thermal yellowing can be suppressed.

The carbodiimide-based hydrolysis inhibitor is a compound having at least one carbodiimide group in the molecule.
Examples of monocarbodiimide compounds include dicyclohexyl carbodiimide, diisopropyl carbodiimide, dimethyl carbodiimide, diisobutyl carbodiimide, dioctyl carbodiimide, diphenyl carbodiimide, naphthyl carbodiimide, and the like.
Examples of polycarbodiimide compounds are high molecular weight polycarbodiimides produced by decarboxylation condensation reaction of diisocyanates in the presence of a carbodiimidization catalyst. Examples of such compounds include those obtained by decarboxylation condensation reaction of the following diisocyanates. It is done. 4,4′-diphenylmethane diisocyanate, 3,3′-dimethoxy-4,4′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, 4,4′-diphenyl ether diisocyanate, 3,3 ′ -Dimethyl-4,4'-diphenyl ether diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1-methoxyphenyl-2,4-diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, One kind of tetramethylxylylene diisocyanate or a mixture thereof can be used.
As the carbodiimidization catalyst, 1-phenyl-2-phospholene-1-oxide, 3-methyl-2-phospholene-1-oxide, 1-ethyl-3-methyl-2-phospholene-1-oxide, 1-ethyl- Phosphorene oxides such as 2-phospholene-1-oxide or their 3-phospholene isomers can be used.

  Examples of the isocyanate-based hydrolysis inhibitor include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-. Diphenylmethane diisocyanate, 2,2′-diphenylmethane diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, 3,3′-dimethoxy-4,4′-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, xylylene diisocyanate, tetramethylxylylene diisocyanate, hydrogenated xylylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, 4, Examples thereof include 4′-dicyclohexylmethane diisocyanate or 3,3′-dimethyl-4,4′-dicyclohexylmethane diisocyanate. Examples of the oxazoline-based hydrolysis inhibitor include 2,2′-o-phenylenebis (2-oxazoline), 2,2′-m-phenylenebis (2-oxazoline), and 2,2′-p-phenylenebis. (2-oxazoline), 2,2′-p-phenylenebis (4-methyl-2-oxazoline), 2,2′-m-phenylenebis (4-methyl-2-oxazoline), 2,2′- p-phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′-m-phenylenebis (4,4′-dimethyl-2-oxazoline), 2,2′-ethylenebis (2-oxazoline) ), 2,2′-tetramethylene bis (2-oxazoline), 2,2′-hexamethylene bis (2-oxazoline), 2,2′-octamethylene bis (2-oxazoline), 2,2 - ethylenebis (4-methyl-2-oxazoline), or 2,2'- diphenylenebis (2-oxazoline).

  Epoxy hydrolyzing agents include diglycidyl ethers of aliphatic diols such as 1,6-hexanediol, neopentyl glycol, polyalkylene glycol, sorbitol, sorbitan, polyglycerol, pentaerythritol, diglycerol, glycerol, triglyceride. Polyglycidyl ether of aliphatic polyol such as methylolpropane, polyglycidyl ether of alicyclic polyol such as cyclohexanedimethanol, aliphatic such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, trimellitic acid, adipic acid, sebacic acid, Diglycidyl ester or polyglycidyl ester of aromatic polycarboxylic acid, resorcinol, bis- (p-hydroxyphenyl) methane, 2,2-bis- (p-hydroxyphenyl) Dipanidyl or polyglycidyl ether of polyphenol such as lopan, tris- (p-hydroxyphenyl) methane, 1,1,2,2-tetrakis (p-hydroxyphenyl) ethane, N, N-diglycidylaniline, N-glycidyl derivatives of amines such as N, N-diglycidyl toluidine, N, N, N ′, N′-tetraglycidyl-bis- (p-aminophenyl) methane, triglycidyl derivatives of aminofail, triglycidyl tris (2-Hydroxyethyl) isocyanurate, triglycidyl isocyanurate, orthocresol type epoxy, phenol novolac type epoxy.

[Antioxidant]
Examples of the antioxidant include a radical scavenger and a peroxide decomposer. Examples of the radical scavenger include phenol compounds and amine compounds, and examples of the peroxide decomposer include sulfur compounds and phosphorus compounds. In particular, phenolic compounds that have a role as radical scavengers in terms of stability and antioxidant effect are preferred, and thermal stability is achieved by using a phenolic compound and a phosphorus compound that has a role as a peroxide decomposer. Is more preferable. More preferably, the antioxidant of a phenol type compound and a phosphorus type compound, and a hydrolysis-resistant agent are used together. Thereby, thermal deterioration of the urethane resin can be prevented, and bleeding of the ester compound can be further suppressed.
The antioxidant is preferably from 0.01 to 2.0 parts by weight, more preferably from 0.1 to 1.5 parts by weight, and even more preferably from 0.2 to 100 parts by weight with respect to 100 parts by weight of the urethane resin. 1.0 part by weight.

  Examples of phenolic compounds include 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearin-β- (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 4,4'-butylidenebis (3-methyl-6-tert-butylphenol), 3,9-bis [1,1-dimethyl-2- [Β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] 2,4,8,10-tetraoxaspiro [5,5] undecane 1,1,3-tris (2-methyl-4-hydroxy-5-tert-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, bis [3,3′-bis- (4 '-Hydroxy-3'-t-butylphenyl) butyric acid] glycol ester, 1,3,5-tris (3', 5'-di-t-butyl-4'-hydroxybenzyl) -S-triazine- 2,4,6- (1H, 3H, 5H) trione, tocophenol and the like.

  Examples of phosphorus antioxidants include triphenyl phosphite, diphenylisodecyl phosphite, 4,4′-butylidene-bis (3-methyl-6-tert-butylphenylditridecyl) phosphite, and cyclic neopentane. Tetraylbis (octadecylphosphite), tris (nonylphenyl) phosphite, tris (monononylphenyl) phosphite, tris (dinonylphenyl) phosphite, diisodecylpentaerythritol diphosphite, 9,10-dihydro-9- Oxa-10-phosphaphenanthrene-10-oxide, 10- (3,5-di-tert-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-tert-butylphenyl) phosphite, cyclic neopentanetetraylbis (2,4-di-tert-butyl) Phenyl) phosphite, cyclic neopentanetetraylbis (2,6-di-tert-butyl-4-methylphenyl) phosphite, 2,2-methylenebis (4,6-di-tert-butylphenyl) octylphos For example, fights.

[Ultraviolet absorber]
Examples of the ultraviolet absorber include benzophenone compounds, benzotriazole compounds, salicylic acid compounds, oxalic acid anilide compounds, cyanoacrylate compounds, and triazine compounds.
The UV absorber is preferably 0.01 to 3.0 parts by weight, more preferably 0.1 to 2.5 parts by weight, and still more preferably 0.2 to 100 parts by weight with respect to 100 parts by weight of the urethane resin. 2.0 parts by weight.

[Light stabilizer]
Examples of the light stabilizer include hindered amine compounds, hindered piperidine compounds, and the like. The light stabilizer is preferably from 0.01 to 2.0 parts by weight, more preferably from 0.1 to 1.5 parts by weight, and even more preferably from 0.2 to 100 parts by weight with respect to 100 parts by weight of the urethane resin. 1.0 part by weight.

<Leveling agent>
The re-peelable pressure-sensitive adhesive of the present invention preferably further contains a leveling agent. The urethane resin with a high ratio of the polyester polyol constituting the urethane resin becomes highly polar, the surface energy becomes high, and the affinity with a low polarity solvent such as toluene used as a reaction solvent or a diluting solvent deteriorates, and the coating film is formed in the drying process. May be insufficient in leveling. When the leveling property of the pressure-sensitive adhesive is insufficient, appearance defects such as repelling, unevenness, and coating stripes occur when the pressure-sensitive adhesive is applied.

In the present invention, the content of the leveling agent is preferably 0.001 to 2.0 parts by weight, more preferably 0.01 to 1.5 parts by weight, with respect to 100 parts by weight of the urethane resin. Preferably it is 0.1-1.0 weight part.
By adjusting the content ratio of the leveling agent within the above range, in the urethane pressure-sensitive adhesive of the present invention, contamination to the adherend can be reduced and sufficient leveling property can be ensured to obtain a smooth coating film. be able to. The leveling agent to be used may be only one type or two or more types.

  Any appropriate leveling agent can be adopted as the leveling agent as long as the effects of the present invention are not impaired. Examples of such a leveling agent include an acrylic leveling agent, a fluorine leveling agent, and a silicon leveling agent. An acrylic leveling agent is preferable because it can reduce contamination of the adherend.

The leveling agent preferably has a weight average molecular weight (Mw) of 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 rate of vaporization when the adhesive is applied does not increase, and the inside of the drying oven is not contaminated.
Further, when the weight average molecular weight (Mw) is 20,000 or less, the leveling property is improved without the movement of the molecule being hindered by the entanglement of the polymer.

<Antistatic agent>
The urethane pressure-sensitive adhesive of the present invention can further contain an antistatic agent. By including an antistatic agent, when used as a surface protective film, it is possible to suppress failure of electronic equipment due to static electricity generated at the time of peeling.

  The antistatic agent is preferably, for example, an inorganic salt, a polyhydric alcohol compound, or an ionic liquid, and more preferably an ionic liquid. In addition, an ionic liquid is also called normal temperature molten salt, and is a salt which has fluidity | liquidity at 25 degreeC.

  Examples of inorganic salts include 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, sodium thiocyanate and the like.

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

The ionic liquid includes imidazolium ions such as 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide and 1- And 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, Octylpyridinium bis (trifluoromethylsulfonyl) imide, 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 and 1-methylpyri Niumubisu etc. (perfluorobutyl sulfonyl) imide. Examples of the ionic liquid containing ammonium ion include trimethylheptylammonium bis (trifluoromethanesulfonyl) imide, N, N-diethyl-N-methyl-N-propylammonium bis (trifluoromethanesulfonyl) imide, N, N-diethyl-N- Methyl-N-pentylammonium bis (trifluoromethanesulfonyl) imide, N, N-diethyl-N-methyl-N-heptylammonium bis (trifluoromethanesulfonyl) imide, tri-n-butylmethylammonium bistrifluoromethanesulfonimide, etc. Can be mentioned. In addition, commercially available ionic liquids such as pyrrolidinium salts, phosphonium salts, and sulfonium salts can be used as appropriate.
Antistatic agents may be used alone or in combination of two or more.

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

  The re-peelable pressure-sensitive adhesive of the present invention can further contain additives such as a silane coupling agent, a colorant, an antifoaming agent, a wetting agent, a weathering stabilizer, a softening agent, a curing accelerator, and a curing retarder.

  The re-peelable pressure-sensitive adhesive of the present invention can produce a surface protective film by the following method. (1) A method in which a releasable pressure-sensitive adhesive is applied to a release liner to form a pressure-sensitive adhesive layer, and then the substrates are bonded together. Alternatively, (2) a method is generally used in which a urethane adhesive is applied to a substrate to form an adhesive layer, and then a release liner is bonded. The pressure-sensitive adhesive layer is usually protected with a release liner until just before using the surface protective film.

  For the application of the re-peelable pressure-sensitive adhesive, known methods such as 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 can be used. After coating, it is common to dry with a hot air oven, an infrared heater or the like.

  The thickness of the re-peelable pressure-sensitive adhesive layer is usually about 1 to 200 μm, preferably about 5 to 100 μm, and more preferably about 10 to 100 μm.

As the base material, general materials such as non-woven fabric, paper, plastic, and synthetic paper can be used as the base material of the adhesive, but plastic is preferable.
Examples of the plastic include polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate, polyphenylene sulfide (PPS), nylon, triacetyl cellulose, cycloolefin, polyimide, and polyamide, among which polyethylene terephthalate is preferable.
The substrate may be subjected to an easy adhesion treatment in order to improve the adhesion with the pressure-sensitive adhesive layer. For the easy adhesion treatment, known methods such as a dry method in which corona discharge is performed and a wet method in which an anchor coating agent is applied can be used. The thickness of the substrate is generally about 5 to 1000 μm.

  Moreover, the base material may be provided with the antistatic layer. The antistatic layer contains a resin and an antistatic agent. As the antistatic agent, conductive carbon particles, conductive metal particles, and conductive polymers are preferable in addition to the antistatic agent described above, and the antistatic layer is formed by depositing, sputtering, or plating a metal on a base material. It can also be formed.

  The release liner generally has a release layer formed by applying a release agent to a substrate such as paper, plastic, or synthetic paper. As the release agent, for example, known compounds such as silicone, alkyd resin, melamine resin, fluororesin, and acrylic resin can be used. The thickness of the release liner is generally about 10 to 150 μm.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to the following examples. Hereinafter, “parts” means “parts by weight” and “%” means “% by weight”.

  In addition, the measuring method of the weight average molecular weight (Mw) of resin, the viscosity of resin, and the hydroxyl value of resin is as follows.

(Weight average molecular weight of resin (Mw))
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.
Device: SHIMADZU Prominence (manufactured by Shimadzu Corporation)
Column: 3 TOSOH TSK-GEL GMHXL (Tosoh Corp.) connected in series Solvent: Tetrahydrofuran Flow rate: 0.5 ml / min
Solvent temperature: 40 ° C., sample concentration: 0.1 wt%, sample injection amount: 100 μl.

(Viscosity of resin)
The viscosity was measured under the following conditions according to JISZ8803.
Apparatus: B-type viscometer TVB10M (Toki Sangyo Co., Ltd.)
Rotor: No. 3
Rotation speed: 12rpm
Measurement temperature: 25 ° C

(Method for measuring hydroxyl value)
It measured by the neutralization titration method according to JISK0070 as shown below. First, 25 g of acetic anhydride was placed in a 100-ml volumetric flask, pyridine was added to make a total volume of 100 ml, and the mixture was thoroughly shaken to prepare an acetylating reagent. The acetylating reagent was kept out of contact with moisture, carbon dioxide and acid vapors and stored in a brown bottle. Next, the sample was weighed into a flat bottom flask, and 5 ml of an acetylating reagent was added to the flask using a total amount of bipet. Next, a small funnel was placed at the mouth of the flask, and the bottom was immersed in a glycerin bath at a temperature of 95-100 ° C. and heated for about 1 cm. In order to prevent the temperature of the flask neck from being heated by the heat of the glycerin bath, a cardboard disc with a round hole in it was put on the base of the flask neck. After 1 hour, the flask was taken out of the glycerin bath, allowed to cool, 1 ml of water was added from the funnel and shaken to decompose acetic anhydride. Furthermore, in order to complete decomposition, the flask was heated again in a glycerin bath for 10 minutes, allowed to cool, and then the funnel and the wall of the flask were washed with 5 ml of ethanol. A few drops of a phenolphthalein solution was added as an indicator, and titrated with a 0.5 mol / l potassium hydroxide ethanol solution. The end point was when the indicator was lightly red for about 30 seconds. The blank test was performed without a sample as described above. And the hydroxyl value of urethane resin solid was computed by following Formula.
(Formula 1) A = ((BC) × f × 28.05 / S) / (Nonvolatile content concentration / 100) + D
(However, in (Formula 2), A: hydroxyl value (mgKOH / g), B: amount of 0.5 mol / l potassium hydroxide ethanol solution used in the blank test (ml), C: 0. 5 mol / l potassium hydroxide ethanol solution amount (ml), f: 0.5 mol / l potassium hydroxide ethanol solution factor (concentration correction factor), S: sample mass (g), D: acid value (mgKOH / g))

  Then, it demonstrates from the manufacturing method of the urethane resin solution used for the Example and the comparative example.

<Urethane resin solution>
(Synthesis Example 1)
In a four-necked flask equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping funnel, under a nitrogen atmosphere, polyester polyol P-1010 (bifunctional polyester polyol, hydroxyl value 112, number average molecular weight 1000, Kuraray Co., Ltd.) 100 parts by weight, 15.5 parts by weight of hexamethylene diisocyanate (manufactured by Sumitomo Bayer), 77 parts by weight of toluene, 0.25 parts by weight of dibutyltin dilaurate and 0.01 parts by weight of tin 2-ethylhexanoate as a catalyst It is. The flask was gradually warmed and reacted at about 90 ° C. for 2 hours. Then, the reaction was continued while confirming the disappearance of the isocyanate group. After confirming the disappearance, the reaction was immediately terminated by cooling. Next, toluene was added so as to have a nonvolatile content of 60% to obtain a urethane resin 1 solution having a viscosity of 3,000 mPa · s, a hydroxyl value (urethane resin solid) of 7.6 mgKOH / g, and a weight average molecular weight of 55,000.

(Synthesis Examples 2 to 11)
Except having changed the raw material and the compounding quantity of the synthesis example 1 as shown in Table 1, it carried out similarly to the synthesis example 1, and obtained the urethane resin solutions 2-11 of the synthesis examples 2-11, respectively.

Table 1 shows the solid content (NV%), weight average molecular weight (Mw), viscosity VIS (mPa · s), and hydroxyl value (OH value mgKOH / g) of the obtained urethane resin solution.

[Example 1]
Isocyanurate modified product of hexamethylene diisocyanate as a curing agent (product name: Coronate HX, manufactured by Nippon Polyurethane Co., Ltd., 100% by weight of a non-volatile content with respect to 100 parts by weight of the urethane resin in the obtained urethane resin 1 solution of Synthesis Example 1. %, NCO% = 21.0), 5.4 parts by weight, bis (2-butoxyethyl) adipate as an ester compound (J Plus Co., Ltd., trade name D931, nonvolatile content 100% by weight, molecular weight 346) 30 parts by weight, phenolic antioxidant (BASF Japan Co., Ltd., trade name IRGANOX 1010, nonvolatile content 100% by weight) and phosphorus antioxidant (BASF Japan Co., trade name IRGAFOS168, as antioxidants) (100% by weight of nonvolatile content) dissolved in 0.8 parts by weight and 0.05 parts by weight toluene, respectively. Furthermore, carbodiimide (trade name Carbodilite V-09GB, non-volatile content: 75% by weight, manufactured by Nisshinbo Co., Ltd.) as a hydrolysis-resistant agent is 0.1 parts by weight in terms of solid content, and a triazine-based UV absorber (BASF) as an UV inhibitor. Japan Co., Ltd., trade name: Tinuvin 477, non-volatile content: 80% by weight, in terms of solid content, 0.5 parts by weight, as a light stabilizer, hindered amine light stabilizer (BASF Japan, Inc., trade name: Tinuvin 123 The urethane adhesive 1 was obtained by blending 0.2 parts by weight of non-volatile content (100% by weight) and 5 parts by weight of ethyl acetate as a solvent and stirring with a disper.

  The urethane pressure-sensitive adhesive 1 was applied to a 50 μm-thick PET base material (Lumirror T60, manufactured by Toray) so that the thickness after drying was 50 μm, dried at 100 ° C. for 4 minutes, and then a 25 μm release liner (250010BD). , Manufactured by Fujimori Kogyo). Subsequently, it was left to stand at 23 degreeC-50% for 1 week, and the surface protection film 1 was obtained.

[Examples 2 to 25, Comparative Examples 1 to 4]
Except having changed the raw material and the compounding quantity of Example 1 as shown in Table 2, it carries out similarly to Example 1, and obtains the surface protection films 2-29 of Examples 2-25 and Comparative Examples 1-4, respectively. It was.

  The following physical property evaluation was performed using the obtained surface protective film.

<Glass adhesive 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. Next, in a 23 ° C.-50% RH atmosphere, the release liner is peeled off from the sample, and the exposed adhesive layer is bonded to a glass plate, pressed once with a 2 kg roller, and allowed to stand for 24 hours before using a tensile tester. Then, the adhesive strength was measured under the conditions of a peeling angle of 180 degrees and a peeling speed of 0.3 m / min.
In general, the lower the adhesiveness to glass and the easier to re-peel, the higher the practicality for surface protection.

<Adhesive strength after heat>
The obtained surface protective film was prepared to have a width of 25 mm and a length of 100 mm to prepare a sample. Next, the release liner was peeled off from the sample in a 23 ° C.-50% RH atmosphere, the exposed pressure-sensitive adhesive layer was attached to a glass plate, and was reciprocated once with a 2 kg roller, and the mixture was aged at 85 ° C. for 48 hours. Thereafter, the sheet was sufficiently cooled at room temperature, and the release liner peeling force was measured using a tensile tester under the conditions of a peeling angle of 180 degrees and a peeling speed of 0.3 m / min to evaluate sheet aging stability. The evaluation criteria are as follows.

A: Easy peeling by hand peeling, no adhesive residue left. (Very good)
○: It can be removed relatively easily by hand peeling, and there is no adhesive residue left. (Good)
(Triangle | delta): It can peel comparatively easily by hand peeling and there are few adhesive residue of an adhesive. (No problem in practical use)
X: Adhesive strength is higher than 300 mN / 25 mm, or there is adhesive adhesive residue. (There are practical problems)

<Low temperature pasteability>
The obtained surface protective film was prepared to have a width of 25 mm and a length of 100 mm to prepare a sample. Next, the release liner was peeled from the sample in a 23 ° C.-50% RH atmosphere, the exposed pressure-sensitive adhesive layer was bonded to a glass plate, and was reciprocated once with a 2 kg roller, and the mixture was aged at −20 ° C. for 48 hours. Thereafter, the sheet was sufficiently cooled at room temperature, and the release liner peeling force was measured using a tensile tester under the conditions of a peeling angle of 180 degrees and a peeling speed of 0.3 m / min to evaluate sheet aging stability. The evaluation criteria are as follows.

(Double-circle): It can peel easily by peeling and a surface protection film does not float. (Very good)
◯: It can be peeled off relatively easily by hand peeling, and the surface protective film does not float. (Good)
X: The surface protective film was lifted. (There are practical problems)

<Heat heat stability over time>
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, it was aged for one week at 60 ° C. and 95% RH. After sufficiently cooling at room temperature, the release liner was peeled off from the sample in a 23 ° C.-50% RH atmosphere, and the exposed pressure-sensitive adhesive layer was bonded to a glass plate, followed by one reciprocal pressure bonding with a 2 kg roller. After curing for 20 minutes, the release liner peel force was measured using a tensile tester under conditions of a peel angle of 180 degrees and a peel speed of 0.3 m / min to evaluate wet heat aging stability. The evaluation criteria are as follows.

A: Change in adhesive strength before and after wet heat aging is 0 or more and less than 30 [mN / 25 mm]. (Very good)
◯: Change in adhesive strength before and after wet heat aging is 30 or more and less than 60 [mN / 25 mm]. (Good)
(Triangle | delta): The change of adhesive force before and behind wet heat aging is 60 or more and less than 90 [mN / 25mm]. (No problem in practical use)
X: The adhesive force change is 90 or more [mN / 25 mm] before and after wet heat aging. (There are practical problems)

<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 measurement sample. Next, the release liner was peeled off from the measurement sample, and the center part of the exposed pressure-sensitive adhesive layer was brought into contact with the glass plate while holding both ends of the pressure-sensitive adhesive sheet by hand. And the wettability of an adhesive was evaluated by measuring time until the whole adhesive layer adhere | attaches a glass plate with the dead weight of the said adhesive sheet. The shorter the time until the pressure-sensitive adhesive sheet is in close contact with the glass plate, the higher the wettability and the higher the practicality for surface protection. The evaluation criteria are as follows.

◎: Less than 3 seconds to adhere (good)
○: 3 seconds or more and less than 4 seconds until contact (no problem in practical use)
X: 4 seconds or more until adhesion, no wetting and widening (practical problem)

<Punching workability>
The obtained surface protective film was prepared to have a width of 100 mm and a length of 100 mm and used as a test sample. Using a punching machine SA1008 small puncher type III (manufactured by Tester Sangyo), 50 shots were continuously punched with a circular Thomson blade having a diameter of 10 mm, and the punching processability was evaluated. The evaluation criteria for punching workability are shown below.

A: The adhesive residue does not adhere to the blade, and the punched circular part of the release liner can be peeled cleanly and lightly. (Very good)
○: Slight adhesive residue adheres to the blade, but the punched circular part of the release liner can be peeled cleanly and lightly. (Good)
Δ: A part of the adhesive residue adheres to the blade, or there is a little resistance when the release paper of the punched circular part is peeled off. (No problem in practical use)
X: Adhesive is extremely attached to the blade, or the resistance when peeling the punched circular part of the release paper is large. (There are practical problems)

<Coating property>
Each re-peelable pressure-sensitive adhesive was applied to a 50 μm-thick PET substrate (Lumirror T60, manufactured by Toray, 430 mm width) using a test coater so that the thickness after drying was 100 μm, and a 25 μm peel was applied. A liner (250010BD, manufactured by Fujimori Kogyo Co., Ltd., 430 mm width) was bonded, and 100 m was wound around a 6-inch ABS core. (Oven length 4 m, adhesive coating width 400 mm, temperature 130 ° C., coating speed 1.0 m / min) At that time, the state of the coated surface was visually observed to evaluate the coating properties.

(A) repelling and unevenness ◎: 2 or less repelling and unevenness per 400 mm × 500 mm (good)
○: 2 to 4 repellency and unevenness per 400 mm × 500 mm (no problem in practical use)
X: 5 or more repellency and unevenness per 400 mm x 500 mm (practical problem)
(B) Coating streak ◎: 0 or less streaks observed at 400 mm width (good)
○: One streak observed at a width of 400 mm (no problem in practical use)
×: Two or more streaks observed at a width of 400 mm (practical problem)

<Long-term storage>
Each re-peelable pressure-sensitive adhesive was applied to a 50 μm-thick PET substrate (Lumirror T60, manufactured by Toray, 430 mm width) using a test coater so that the thickness after drying was 100 μm, and a 25 μm peel was applied. A liner (250010BD, manufactured by Fujimori Kogyo Co., Ltd., 430 mm width) was bonded, and 100 m was wound around a 6-inch ABS core. (Oven length 4m, adhesive coating width 400mm, temperature 130 ° C, coating speed 1.0m / min)
Subsequently, it was left to stand at 23 ° C.-50% for 1 week, and the surface protective film was slit into a width of 380 mm and wound around a 3-inch ABS core to obtain a surface protective film roll. It was allowed to stand for 1 month in an environment of 40 ° C. and 90% RH, and the end portion of the surface protective film roll was visually confirmed to check for the seepage of the ester compound. In addition, a change in color was also confirmed.

A: No change with time (good)
○: Slight yellowing of the surface protection film compared to before aging (no problem in practical use)
X: Compared with before aging, the surface protective film is yellowed, and the ester compound oozes out from the end (practical problem)

From the results in Table 3, the pressure-sensitive adhesive for re-peeling of the present invention was able to obtain a pressure-sensitive adhesive sheet and a surface protective film that were excellent in re-peelability, moist heat resistance and wettability, and also excellent in punching processability.
Especially, when the content of the polyester diol in the polyol constituting the urethane resin is 20% by weight or more in 100% by weight of the polyester polyol, the punching processability was particularly excellent. In addition, when the anti-degeneration agent used in combination with an antioxidant and a hydrolysis-resistant agent or ultraviolet absorber, it was excellent in long-term storage.

By containing 20% by weight or more of polyester diol, the pressure-sensitive adhesive layer is prevented from becoming too hard due to reaction with the curing agent, and processability is improved. In case the polyester diol is Ru contains 30 wt% or more is preferred in order to further improve the coating property.

In the present invention, within the range not impairing the effects of the present invention, other polyols its can be used in combination with polyester polyols. For example, polyether polyol, polycarbonate polyol, or acrylic polyol can be used in combination, and among these, polyether polyol is preferable.
Examples of polyether polyols include polyoxytetramethylene glycol (PTMG), polyoxypropylene glycol (PPG), and polyoxyethylene glycol (PEG).
The polyether polyol preferably has 2 or 3 hydroxyl groups from the viewpoint of reactivity, and preferably has a number average molecular weight of 500 to 15,000.

The amount of the polyfunctional isocyanate compound used is preferably 1.0 to 4.0 equivalents, more preferably 1.25 to 3.75 equivalents, and more preferably 1.5 to 3 equivalents as an isocyanate group with respect to the hydroxyl equivalent of the urethane resin. More preferred is 5 equivalents.
The amount of the polyfunctional isocyanate compound, if the amount exceeds 4.0 equivalents to hydroxyl equivalent of the urethane resin, urethane resin becomes too hard hitting Chi punching deteriorates, 1.0 urethane resin The less than equivalent When the surface protective film is peeled off, it may become too soft and adhesive residue may be generated on the adherend. By making the usage-amount of a polyfunctional isocyanate compound into 1.0-4.0 equivalent with respect to the hydroxyl group equivalent of the said urethane resin, it becomes easier to balance punching workability and removability.

Table 1 shows the solid content (NV%), weight average molecular weight (Mw), viscosity VIS (mPa · s), and hydroxyl value (OH value mgKOH / g) of the obtained urethane resin solution.

[Examples 2 to 25, Comparative Examples 1 to 4]
Except having changed the raw material and the compounding quantity of Example 1 as shown in Table 2, it carries out similarly to Example 1, and obtains the surface protection films 2-29 of Examples 2-25 and Comparative Examples 1-4, respectively. It was.
However, Examples 12, 15, 21, 23, and 24 are reference examples.

Claims (5)

  A urethane resin obtained by reacting a polyol and a polyisocyanate, a curing agent, an ester compound (except in the case of a urethane resin), and an anti-altering agent, and the polyol contains a polyester polyol in 100% by weight of the polyol. A re-peelable pressure-sensitive adhesive containing 50% by weight or more.   The re-peelable pressure-sensitive adhesive according to claim 1, wherein the polyester polyol contains 20% by weight or more of a polyester diol in 100% by weight of the total polyester polyol.   The re-peelable pressure-sensitive adhesive according to claim 1 or 2, wherein the anti-degeneration agent is at least one selected from the group consisting of an antioxidant, a hydrolysis-resistant agent, an ultraviolet absorber, and a light stabilizer.   The re-peelable pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the polyester polyol has a number average molecular weight of 500 to 5,000.   The surface protection film provided with the base material and the adhesive layer formed from the re-peelable adhesive of any one of Claims 1-4.