JP2016186029A - Removable adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a removable adhesive and an adhesive sheet substantially preventing problems of contaminating property and productivity, suppressing contamination and having good wettability.SOLUTION: The removable adhesive comprises a urethane resin (A), a curing agent (B), and an organic acid diester or triester (C), in which the organic acid diester or triester (C) shows a weight loss of 3 wt.% or less after heated at 150°C for 10 minutes. The organic acid diester or triester (C) preferably has a molecular weight of 300 to 600. The removable adhesive contains the organic acid diester or triester (C) by 0.5 to 50 parts by weight with respect to 100 parts by weight of the urethane resin (A).SELECTED DRAWING: None

Description

  The present invention relates to an adhesive having removability.

  The pressure-sensitive adhesive sheet is widely used for label applications by taking advantage of the function of being peeled after being applied, and is also used for surface protection when manufacturing electronic devices. The pressure-sensitive adhesive sheet is used for surface protection to prevent breakage of the glass surface when manufacturing a liquid crystal display, but when the pressure-sensitive adhesive sheet is pasted, bubbles are involved in the interface between the pressure-sensitive adhesive layer and the glass. There is a case. Therefore, the re-peelable pressure-sensitive adhesive used for the pressure-sensitive adhesive sheet is required to have a property (hereinafter referred to as wettability) that makes it difficult for air bubbles to be involved in the interface between the pressure-sensitive adhesive layer and the adherend in addition to the re-peelability. It was.

  Therefore, Patent Documents 1 and 2 disclose a pressure-sensitive adhesive containing a polyurethane-based resin and a fatty acid ester.

JP2011-190420A JP 2014-111701 A

However, conventional adhesives have high volatility of fatty acid esters, so when applying adhesives, the production of adhesive sheets is stopped by the large amount of fatty acid esters that have volatilized in the drying oven and become contaminated. As a result, the drying oven has to be cleaned frequently. Furthermore, the fatty acid ester volatilizes during coating, and the amount of the fatty acid ester contained in the pressure-sensitive adhesive sheet is insufficient, so that the removability is lowered, and it is difficult to obtain desired wettability.
On the other hand, in order to suppress the volatilization of the fatty acid ester, a measure to reduce the drying temperature and the coating speed can be considered, but there has been a problem that the productivity of the pressure-sensitive adhesive sheet is greatly reduced.

  In addition, the conventional pressure-sensitive adhesive had no problem under normal use conditions, but when it was used at extremely high or low temperatures, after the pressure-sensitive adhesive sheet was peeled off, the fatty acid monoester may migrate to the adherend and cause contamination. .

  An object of the present invention is to provide a re-peelable pressure-sensitive adhesive and a pressure-sensitive adhesive sheet that hardly cause contamination and productivity problems, suppress contamination, and have good wettability.

  The re-peelable pressure-sensitive adhesive of the present invention includes a urethane resin (A), a curing agent (B), and a diester or triester (C) of an organic acid, and the diester or triester (C) of the organic acid is The weight loss after heating at 150 ° C. for 10 minutes is 3% by weight or less.

  According to the present invention, an adhesive component at the time of coating is obtained by using an organic acid diester or triester (C) having a weight loss rate of 3% or less after heating at 150 ° C. for 10 minutes. Volatilization can be suppressed. Thereby, the contamination in the drying oven could be suppressed. Furthermore, conventionally, coating was performed at a low drying temperature and a low coating speed in order to prevent volatile contamination of fatty acid esters, etc., but it became possible to produce each with a high setting, which greatly improved productivity. . Moreover, since fatty acid ester containing a long-chain alkyl chain has low polarity, compatibility with a urethane resin having a highly polar urethane bond is deteriorated. In the present invention, an organic acid ester having a plurality of ester groups is used. The polarity could be improved by using it. Thereby, adherend contamination could be suppressed by improving compatibility with the urethane resin (A). Furthermore, the pressure-sensitive adhesive sheet using the releasable pressure-sensitive adhesive containing a diester or triester (C) of an organic acid also has an effect of improving wettability.

  An object of the present invention is to provide a re-peelable pressure-sensitive adhesive and a pressure-sensitive adhesive sheet that hardly cause contamination and productivity problems, suppress contamination, and have good wettability.

  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 comprises a urethane resin (A), a curing agent (B), and a diester or triester (C) of an organic acid, and after heating the organic acid ester at 150 ° C. for 10 minutes. Is 3% by weight or less. The re-peelable pressure-sensitive adhesive of the present invention is preferably used as a pressure-sensitive adhesive sheet provided with a base material by coating to form a pressure-sensitive adhesive layer. The organic acid diester or triester (C) means an organic acid diester or organic acid triester.

  In the present invention, the urethane resin (A) is a resin having a plurality of hydroxyl groups, and can be synthesized by reacting polyol and polyisocyanate. As the polyol, for example, polyester polyol, polyether polyol, polycarbonate polyol, acrylic polyol, and the like are preferable.

The polyester polyol is obtained by reacting an acid component with a glycol component.
Examples of the acid component include terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, trimellitic acid, and the like.
Examples of the glycol component include ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexane glycol, 3-methyl-1,5-pentanediol, 3,3′-dimethylol heptane, polyoxyethylene glycol, poly Examples of the oxypropylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, and polyol component include glycerin, trimethylolpropane, and pentaerythritol. Other examples include polyester polyols obtained by ring-opening polymerization of lactones such as polycaprolactone, poly (β-methyl-γ-valerolactone), and polyvalerolactone.
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 for polyester polyol, 10-70 mol% is preferable among the total 100 mol% of the polyol used for the synthesis | combination of a urethane resin.

Examples of the polyether polyol include polypropylene glycol, polyethylene glycol, and polytetramethylene glycol. The polyether polyol can be produced by polymerizing a cyclic ether compound using a low molecular weight polyol as an initiator.
Examples of the low molecular weight polyol include propylene glycol, ethylene glycol, glycerin and trimethylolpropane.
Examples of the cyclic ether compound include ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran.

  The number average molecular weight of the polyether polyol is preferably 1,000 to 5,000. When the number average molecular weight is 1,000 or more, it becomes easier to control the reaction at the time of synthesis, and when the number average molecular weight is 5,000 or less, the time until completion of the reaction can be easily shortened. The removability is further improved by easily maintaining the cohesive strength of the layer. Further, the polyether polyol usually has two hydroxyl groups, but can also have three or more hydroxyl groups. When a polyether polyol having three or more hydroxyl groups is used, the cohesive force of the pressure-sensitive adhesive layer can be easily adjusted. As for polyether polyol, 30-90 mol% is preferable among the total 100 mol% of the polyol used for the synthesis | combination of a urethane resin (A).

  Polycarbonate polyols include, for example, polytrimethylene carbonate diol, polyhexamethylene carbonate diol, poly 3-methyl (pentamethylene) carbonate diol, copolymers thereof, ethylene glycol, 1,3-trimethylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,18- Examples thereof include polycarbonate diols obtained by dealcoholization reaction between polyhydric alcohols such as octadecanediol and dialkyl carbonates such as diethylene carbonate and dimethyl carbonate.

  In the present invention, the polyol can be further improved in peel strength and adhesive strength by using polyester polyol and polyether polyol in combination.

  A known compound can be used as the polyisocyanate. Specifically, aromatic polyisocyanate, aliphatic polyisocyanate, araliphatic polyisocyanate, alicyclic polyisocyanate, and the like are 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 (A). 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 part by weight based on 100 parts by weight of the total of polyol and polyisocyanate.

  In the present invention, the polyol used for the synthesis of the urethane resin is not limited. However, if a polyol having an ester bond is used, the compatibility with the diester or triester (C) of the organic acid is further improved, so at least the polyester polyol is used. It is preferable to use a polyester polyol and a polyether polyol in combination. On the other hand, since both polyols have different reactivity, it is preferable to use a catalyst suitable for each polyol.

  The synthesis of the urethane resin (A) includes (1) a method in which a polyol, a catalyst, and a polyisocyanate are charged in a total amount in a flask, and a reaction method. (2) a method in which a polyol and a catalyst are charged in a flask and the polyisocyanate is dropped. preferable.

  A known solvent can be used for the synthesis of the urethane resin (A). Specific examples include methyl ethyl ketone, ethyl acetate, toluene, xylene and acetone.

  The weight average molecular weight (Mw) of the urethane resin (A) 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, re-peelability improves more by becoming 400,000 or less.

  The urethane resin (A) in the present invention preferably has a hydroxyl value of 10 to 40 mgKOH / g, more preferably 15 to 35 mgKOH / g. When the hydroxyl value of the urethane resin (A) is 10 mgKOH / g or more, the adhesive strength is improved, and the heat resistance and heat and humidity resistance are also improved. Moreover, when a hydroxyl value will be 35 mgKOH / g or less, cohesion force will improve and adhesive force will also improve. The hydroxyl value was measured by a titration method using potassium hydroxide according to JISK0070.

  The urethane resin (A) may further have an acid value. Preferably it is 20-80 mgKOH / g, 30-70 mgKOH / g is more preferable, 40-60 mgKOH / g is further more preferable. The acid value was measured by a titration method using potassium hydroxide in accordance with JISK0070.

In the present invention, an organic acid diester or triester (C) (hereinafter also referred to as an ester (C)) has a plurality of ester bonds and thus has a high polarity. Therefore, the organic acid diester or triester (C) has a good compatibility with a highly polar urethane resin. . Furthermore, ester (C) provides a softness | flexibility to an adhesive layer and wettability improves. Therefore, for example, when the pressure-sensitive adhesive sheet is attached to a smooth adherend such as a glass plate, it is difficult for air bubbles to be caught in the interface between the pressure-sensitive adhesive layer and the glass. In addition, since the compatibility is good, the ester (C) is difficult to bleed from the pressure-sensitive adhesive layer when used at extremely high or low temperatures, so that contamination of the adherend can be suppressed.
Moreover, since the weight reduction rate after heating for 10 minutes at 150 degreeC is 3% or less, since ester (C) is hard to volatilize by heating, the contamination in the drying oven at the time of coating can be suppressed. Furthermore, unlike fatty acid esters, etc., the re-peelable adhesive can be applied at a higher drying temperature without worrying about volatile contamination, making it possible to increase the coating speed and increasing the productivity of the adhesive sheet. Can be improved. In addition, if it is in the range which can solve the subject of this invention, the organic acid ester (a monoester, a diester, or a triester) which does not satisfy | fill the characteristic that the weight loss rate after heating for 10 minutes at 150 degreeC is 3% or less is included. Can be used together.

  The ester (C) is an ester obtained by reacting a dicarboxylic acid with an alcohol, or an ester obtained by reacting a tricarboxylic acid with an alcohol. The dicarboxylic acid and tricarboxylic acid (hereinafter also referred to as carboxylic acid component) preferably have a linear or cyclic hydrocarbon group, and more preferably a linear hydrocarbon group. When the ester (C) having a linear hydrocarbon group is used, wettability is further improved, and contamination of the adherend can be further suppressed. The carboxylic acid component is preferably a saturated hydrocarbon group or an unsaturated hydrocarbon group. Among these carboxylic acid components, those composed of linear and saturated hydrocarbon groups are more preferred. The carboxylic acid component is preferably dicarboxylic acid and tricarboxylic acid, and more preferably dicarboxylic acid.

  Among the carboxylic acid components, dicarboxylic acids having a linear hydrocarbon group are, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, etc. Is mentioned. Similarly, the tricarboxylic acid having a linear hydrocarbon group is, for example, 1,2,3-propanetricarboxylic acid, 1,2,3-butanetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,3. -Pentanetricarboxylic acid, 1,2,4-pentanetricarboxylic acid, 1,2,5-pentanetricarboxylic acid, 1,3,4-pentanetricarboxylic acid, 1,3,5-pentanetricarboxylic acid, 2,3,4 -Pentanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,1,6-hexanetricarboxylic acid, 1,3,5-hexanetricarboxylic acid, 1,2,6-hexanetricarboxylic acid, 1,3,3 -Hexanetricarboxylic acid, 1,2,4-hexanetricarboxylic acid, 2,4,4-hexanetricarboxylic acid, 1,4,5-hexanetricarboxylic acid, 1,4-hexanetricarboxylic acid, 1,3,6-hexanetricarboxylic acid, 2,3,5-hexanetricarboxylic acid, 1,4,8-octanetricarboxylic acid, 1,5,10-nonanetricarboxylic acid and the like. .

Similarly, dicarboxylic acids having a branched hydrocarbon group are, for example, 2-carboxymethyl-1,3-propanedicarboxylic acid, 3-carboxymethyl-1,5-pentanedicarboxylic acid, 3-carboxyethyl-1,5. -Pentanedicarboxylic acid, 3-carboxyethyl-1,6-hexanedicarboxylic acid and the like.
Among the carboxylic acid components, dicarboxylic acids having a cyclic hydrocarbon group are, for example, 1,2- and 1,3-cyclopentanedicarboxylic acid, 1,2-, 1,3-, 1,4-cyclohexanedicarboxylic acid and the like. Alicyclic dicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 2-methylisophthalic acid And aromatic dicarboxylic acids such as 3-methylphthalic acid and 2-methylterephthalic acid.
Similarly, the tricarboxylic acid having a cyclic hydrocarbon group is, for example, alicyclic tricarboxylic acid such as 1,2,3-cyclohexanetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, Aromatic tricarboxylic acids such as trimellitic acid, trimesic acid and 1,2,5-naphthalene tricarboxylic acid can be mentioned.

As the alcohol, a known alcohol capable of forming an ester bond with the carboxylic acid component can be used. Among the known alcohols, the alcohol is preferably an alcohol having 2 to 15 carbon atoms, more preferably an alcohol having 2 to 12 carbon atoms. When alcohol having 2 to 12 carbon atoms is used, the compatibility between the ester (C) and the urethane resin (A) is further improved, so that the wettability is further improved.
Examples of the alcohol include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, isobutyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, isononyl alcohol, decyl alcohol isodecyl alcohol and 2-ethyl. Examples include hexyl alcohol. Among these, isononyl alcohol, isodecyl alcohol, and 2-ethylhexyl alcohol are preferable.

The ester (C) can be obtained using a known esterification reaction.
Examples of organic acid diesters include dimethyl oxalate, diethyl oxalate, dibutyl oxalate, dimethyl malonate, diethyl malonate, dibutyl malonate, dibenzyl malonate, dimethyl succinate, diethyl succinate, dibutyl succinate, dioctyl succinate, Dimethyl glutarate, dimethyl adipate, diethyl adipate, diisopropyl adipate, dibutyl adipate, diisobutyl adipate, dihexyl adipate, dioctyl adipate, diisononyl adipate, didecyl adipate, diisodecyl adipate, decylisooctyl adipate, Diisooctyl adipate, Dibutyl diglycol adipate, Dimethyl pimelate, Diethyl pimelate, Dimethyl suberate, Diethyl suberate, Dimethyl azelate, Azela Diethyl azelate, di-2-ethylhexyl azelate, diethyl sebacate, diisopropyl sebacate, dibutyl sebacate, dioctyl sebacate, di-2-ethylhexyl sebacate, dimethyl maleate dodecanedioate, diethyl maleate, maleic acid Dibutyl, dioctyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dioctyl fumarate, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, dioctyl phthalate, dioctyl phthalate, diisononyl phthalate, phthalate Examples include didecyl acid, diisodecyl phthalate, ditridecyl phthalate, and di-2-ethylhexyl phthalate.
Examples of the organic acid triester include tris-2-ethylhexyl trimellitic acid and triisodecyl trimellitic acid.
Further, the ester (C) may contain a functional group such as an epoxy group. Specific examples include di-2-ethylhexyl epoxyhexahydrophthalate, diisononyl epoxyhexahydrophthalate, and the like.
Esters (C) can be used alone or in combination of two or more.

  The ester (C) preferably has a molecular weight of 300 to 600, more preferably 300 to 540. When the molecular weight is 300 to 600, the ester (C) is further improved in compatibility with the urethane resin (A), and the heat resistance is further improved. The molecular weight is a formula weight.

  Among the esters (C), esters of dicarboxylic acids and alcohols having a linear hydrocarbon group are preferred, and adipic acid diesters, sebacic acid diesters, and azelaic acid diesters are more preferred.

  The ester (C) 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 (A). When 5 parts by weight or more of ester (C) is used, wettability and removability are further improved. Further, when the amount is 50 parts by weight or less, contamination can be further suppressed.

  In the present invention, the curing agent (B) is a compound having a plurality of functional groups capable of reacting with the urethane resin (A). The curing agent (C) is preferably a polyisocyanate compound, an aziridine compound, a metal chelate compound, or an epoxy compound, and more preferably a polyisocyanate compound.

  Examples of the polyisocyanate 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 polymethylene polyphenyl isocyanate, adducts, burettes or isocyanurates of these polyisocyanate compounds and polyol compounds such as trimethylolpropane, and these polyisocyanate compounds and known polyethers Polyol and polyester polyol Acrylic polyols, polybutadiene polyols or adducts, etc. and polyisoprene polyol and the like. Among these, a polyisocyanate compound having three isocyanate groups is preferable, an isocyanurate of hexamethylene diisocyanate and a trimethylolpropane adduct of hexamethylene diisocyanate are more preferable, and an isocyanurate of hexamethylene diisocyanate is more preferable.

  Examples of the aziridine compound include N, N′-hexamethylene-1,6-bis (1-aziridinecarboxamide, trimethylolpropane-tri-β-aziridinylpropionate, N, N′-diphenylmethane 4,4 ′. -Bis (1-aziridinecarboxamide), trimethylolpropane-tri-β- (2-methylaziridine) propionate and the like.

  The metal chelate compound is preferably a metal complex compound. Examples of the metal include nickel, aluminum, chromium, iron, titanium, zinc, cobalt, manganese, copper, tin, and zirconium. Examples of the metal chelate compound include ferric trisacetylacetonate, aluminum trisacetylacetonate, aluminum monoacetylacetonate bis (ethylacetoacetate), and aluminum tris (ethylacetoacetate).

  Examples of the epoxy compound include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane triglycidyl ether. , Diglycidyl aniline, diamine glycidyl amine, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-diamine glycidylaminomethyl) cyclohexane and the like.

  A hardening | curing agent (B) may be used independently or may be used in combination of 2 or more types.

  The curing agent (B) is preferably used in an amount of 1 to 35 parts by weight, preferably 3 to 25 parts by weight, and more preferably 5 to 20 parts by weight with respect to 100 parts by weight of the urethane resin (A). By using 5 to 20 parts by weight of the curing agent, it becomes easy to balance the cohesive strength, adhesive strength and removability.

The re-peelable pressure-sensitive adhesive of the present invention can further contain an alteration inhibitor. With the alteration preventing agent, it is possible to prevent alteration or deterioration of the re-peelable pressure-sensitive adhesive in a high-temperature atmosphere, inhibit re-peelability lowering, and decrease adherend contamination. As the alteration preventing agent, an antioxidant, an ultraviolet absorber, a light stabilizer and the like are preferable.
Examples of the antioxidant include a phenol compound, an amine compound, a sulfur compound, a phosphorus compound, a monophenol compound, and a bisphenol compound.
Examples of the ultraviolet absorber include benzophenone compounds, benzotriazole compounds, salicylic acid compounds, oxalic anilide compounds, cyanoacrylate compounds, triazine compounds, and the like.
Examples of the light stabilizer include hindered amine compounds and hindered piperidine compounds.
Anti-altering agents may be used alone or in combination of two or more.

  It is preferable to mix 0.01-10 weight part with respect to 100 weight part of urethane resin (A), and 0.1-5 weight part is more preferable.

  The re-peelable pressure-sensitive adhesive of the present invention can further contain an antistatic agent. By including the antistatic agent, it is possible to suppress failure of the electronic device due to static electricity generated during re-peeling.

The antistatic agent is preferably, for example, an inorganic salt, a polyhydric alcohol compound, an ionic liquid, etc. Among them, an ionic liquid is more preferable. 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, for example, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1,3-dimethylimidazolium bis (trifluoromethylsulfonyl) imide, and 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide. 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, 1- 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 preliminary 1-methylpyridinium bis (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 (A).

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

The pressure-sensitive adhesive sheet of the present invention preferably includes a pressure-sensitive adhesive layer formed from a re-peelable pressure-sensitive adhesive and a base material.
The method of creating the pressure-sensitive adhesive sheet is (1) a method in which a re-peelable 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 of applying a releasable pressure-sensitive adhesive to a substrate to form a pressure-sensitive adhesive layer and then bonding a release liner is generally used. A cast pressure-sensitive adhesive sheet is obtained by attaching a release liner in place of the substrate by the method (1). Moreover, a double-sided pressure-sensitive adhesive sheet is obtained when a pressure-sensitive adhesive layer is separately formed on the opposite surface of the substrate after the pressure-sensitive adhesive layer is formed by the method (2). When creating a double-sided PSA sheet, other types of PSA may be used in addition to the re-peelable PSA. The pressure-sensitive adhesive layer is usually protected with a release liner until just before using the pressure-sensitive adhesive sheet. Although it is preferable to use the adhesive sheet of this invention for a re-peeling application, it can also be used for the use (for example, permanent adhesive use) which does not require re-peeling.

  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 pressure-sensitive adhesive layer is usually about 1 to 200 μm, preferably about 5 to 100 μm, and more preferably about 10 to 75 μm.

As the base material, general materials such as non-woven fabric, paper, plastic, synthetic paper and the like can be used as the base material for the adhesive. Moreover, when using a base material as a core material of a double-sided adhesive sheet, a nonwoven fabric or a 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.
The base material may be an optical member such as an antireflection (AR) film, a polarizing plate, or a retardation plate.
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. In the re-peelable pressure-sensitive adhesive of the present invention, the peeling force between the pressure-sensitive adhesive layer and the release liner is unlikely to depend on the type of the release agent.
The thickness of the release liner is generally about 10 to 150 μm.

  The pressure-sensitive adhesive sheet of the present invention is preferably used, for example, for surface protection of displays such as mobile phones, smartphones, tablet terminals and monitors, and for surface protection during display production. Specifically, protection of a transparent electrode (indium tin oxide film), protection of a touch screen (touch panel) and a cover glass, protection of a liquid crystal module, and the like. Among these, the use which protects glass surfaces, such as a cover glass, is more preferable. Furthermore, the pressure-sensitive adhesive sheet of the present invention can be used in a wide range of applications regardless of whether or not re-peelability is necessary, not limited to the above applications.

  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”.

(Synthesis Example 1)
Polyester polyol P-1010 (bifunctional polyester polyol, hydroxyl value 112, number average molecular weight 1000, Kuraray Co., Ltd.) under a nitrogen atmosphere in a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel 81 parts by weight, polyether polyol G-3000B (trifunctional polyether polyol, hydroxyl value 56, number average molecular weight 3000, manufactured by Adeka) 101 parts by weight, hexamethylene diisocyanate (Sumitomo Bayer) 19 parts by weight, toluene 134 parts by weight, 0.05 parts by weight of dibutyltin dilaurate and 0.02 parts by weight of tin 2-ethylhexanoate were charged as catalysts. 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. Subsequently, toluene was added so as to have a nonvolatile content of 60% to obtain a urethane resin 1 solution having a viscosity of 3300 mPa.s, a hydroxyl value of 25 mgKOH / g, and a weight average molecular weight of 152,000.

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.

(Synthesis Example 2)
Polyester polyol P-2010 (bifunctional polyester polyol, hydroxyl value 56, number average molecular weight 2000, Kuraray Co., Ltd.) under a nitrogen atmosphere in a four-necked flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel 53.6 parts by weight, 101 parts by weight of polyether polyol G-3000B, 19 parts by weight of hexamethylene diisocyanate, 134 parts by weight of toluene, 0.05 part by weight of dibutyltin dilaurate, 0.02 part by weight of tin 2-ethylhexanoate Was charged. 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 by IR, and immediately after the disappearance was confirmed, the reaction was terminated by cooling. Subsequently, toluene was added so as to have a nonvolatile content of 60% to obtain a urethane resin 2 solution having a viscosity of 4800 mPa.s, a hydroxyl value of 25 mgKOH / g, and a weight average molecular weight of 195,000.

(Acid value measuring method)
It measured by the neutralization titration method according to JISK0070 as shown below. First, the sample was weighed into an Erlenmeyer flask. Next, 100 ml of acetone and a few drops of a phenolphthalein solution as an indicator were added and shaken well until the sample was completely dissolved on a water bath. Next, the solution was titrated with a 0.1 mol / l potassium hydroxide ethanol solution, and the end point was when the light red color of the indicator lasted for 30 seconds. And the acid value was computed by following Formula.
(Formula 1) A = [B × f × 5.611 / S] / (Non-volatile content concentration / 100)
(However, in (Formula 1), A: acid value (mgKOH / g), B: amount of 0.1 mol / l potassium hydroxide ethanol solution used for titration (ml), f: 0.1 mol / l hydroxide) Factor (concentration correction factor) of potassium ethanol solution, S: mass of sample (g))

(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 was computed by following Formula.
(Formula 2) 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))

<Weight reduction rate>
The volatility of an organic acid diester or triester is measured by the following procedure. First, a mentum can with a can lid was weighed (X), and then about 2 g of the sample was put into a mentum can with a can lid and weighed (Y). Next, the lid of the metal can containing the sample was opened and heated at 150 ° C. for 10 minutes, and then the mentum can was taken out, immediately covered, allowed to cool at room temperature, and the sample after heating was contained. Mentum cans with can lids were weighed (Z). The weight reduction rate after heating at 150 ° C. for 10 minutes was calculated using the following formula 1.
(Formula 3) Weight reduction rate (%) = 100 − ((Z−X) / (Y−X)) × 100
○: Weight reduction rate after heating is 3% or less ×: Weight reduction rate after heating is over 3%

[Example 1]
35 parts by weight of di-2-ethylhexyl adipate as an organic acid ester, and Irganox 1135 as an alteration inhibitor (hindered phenol-based oxidation by BASF) with respect to 100 parts by weight of urethane resin 1 in the obtained urethane resin 1 solution 1.0 part by weight of the inhibitor), 12.0 parts by weight of hexamethylene diisocyanate trimethylolpropane adduct (ethyl acetate solution having a nonvolatile content of 75% by weight) as the polyisocyanate compound, and 20 weight by weight of toluene as the solvent. A re-peelable pressure-sensitive adhesive having a non-volatile content of 62% was obtained by mixing partly and stirring with a disper.

[Example 20]
35 parts by weight of diisodecyl adipate as an organic acid ester, 1.0 part by weight of irganox 1135 as an alteration inhibitor, and 100 parts by weight of a polyisocyanate compound as described above with respect to 100 parts by weight of urethane resin 2 in the obtained urethane resin 2 solution A hexamethylene diisocyanate trimethylolpropane adduct was mixed with 12.0 parts by weight in terms of nonvolatile content, 20 parts by weight of toluene as a solvent, and stirred with a disper to obtain a releasable adhesive having a nonvolatile content of 62%.

[Examples 2-19, 21-22, Comparative Examples 1-5]
Removable molds of Examples 2 to 20 and 22 and Comparative Examples 1 to 7, respectively, by carrying out in the same manner as in Example 1 except that the raw materials and blending amounts of Example 1 were changed as shown in Table 1 and Table 2. An adhesive was obtained.

<Creation of adhesive sheet>
The obtained re-peelable pressure-sensitive adhesive was applied to a PET substrate having a thickness of 50 μm so that the thickness after drying was 10 μm, dried at 100 ° C. for 2 minutes, and then a release liner was bonded thereto. Subsequently, it was left to stand at 23 ° C.-50% for 1 week to obtain an adhesive sheet.

The weight loss rates after heating the organic acid esters in the table at 150 ° C. for 10 minutes are as follows.
Di-2-ethylhexyl adipate 0.2% by weight
Diisononyl adipate 0.2% by weight
Diisodecyl adipate 0.1% by weight
0.1% by weight of di-2-ethylhexyl sebacate
Di-2-ethylhexyl azelate 0.1% by weight
Di-2-ethylhexyl phthalate 0.2% by weight
Diisononyl phthalate 0.1% by weight
Diisodecyl phthalate 0.1% by weight
Diundecyl phthalate 0.1% by weight
Ditridecyl phthalate 0.1% by weight
Epoxy hexahydrophthalate di-2-ethylhexyl 0.1% by weight
Tri-2-ethylhexyl trimellitic acid 0.1% by weight
Isopropyl myristate 15.0% by weight
4.9% by weight methyl oleate
0.8% by weight of isobutyl oleate
Diisobutyl adipate 18.8% by weight

  The following physical property evaluation was performed using the obtained adhesive sheet.

<Adhesive strength>
The obtained pressure-sensitive adhesive sheet was prepared as a sample having a width of 25 mm and a length of 100 mm. Next, in a 23 ° C.-50% RH atmosphere, the release liner was peeled off from the sample, and the exposed adhesive layer was bonded to a 25 μm PET film (Embret S-25 manufactured by Unitika), and was reciprocated once with a 2 kg roller. After standing for a period of time, the adhesive strength was measured using a tensile tester under conditions of a peeling angle of 180 degrees and a peeling speed of 0.3 m / min.

<Removability>
The obtained pressure-sensitive adhesive sheet was prepared as a sample having a width of 25 mm and a length of 100 mm. Next, the release liner was peeled off from the sample in an atmosphere of 23 ° C.-50% RH, and the exposed adhesive layer was bonded to a glass plate and pressed once with a 2 kg roller, followed by aging at 40 ° C. for 1 week. Further, after being left for 30 minutes in an atmosphere of 23 ° C.-50% RH, an adhesive strength was measured using a tensile tester under conditions of a peeling angle of 180 degrees and a peeling speed of 0.3 m / min. Separately, the adhesive sheet was peeled off by hand for the samples aged in the same manner as described above, and the removability was evaluated. The evaluation criteria are as follows.
A: The adhesive strength was within 30 mN / 25 mm, and the adhesive sheet could be easily peeled off by hand peeling. (Good)
(Triangle | delta): Adhesive strength was 30-100 mN / 25mm or less, and the adhesive sheet could be peeled comparatively easily by hand peeling. (No problem in practical use)
X: The adhesive strength was higher than 100 mN / 25 mm, and the pressure-sensitive adhesive sheet could not be easily removed by manual peeling. (Not practical)

<Contamination>
The obtained pressure-sensitive adhesive sheet was prepared to have a width of 50 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 exposed pressure-sensitive adhesive layer was attached to a glass plate, and then allowed to stand in an atmosphere of 85 ° C.-95% RH and −30 ° C. for 72 hours. Furthermore, after leaving for 30 minutes under 23 degreeC-50% RH atmosphere, the adhesive sheet was peeled and the adherend contamination | pollution property was evaluated by observing the surface of the glass plate after peeling visually. The evaluation criteria are as follows.
◯: There was no contamination on the glass plate (good)
Δ: The glass plate was slightly contaminated. (No problem in practical use)
X: The glass plate was contaminated. (Not practical)

<Dry oven contamination>
Apply the resulting adhesive to 100 m at an oven length of 1 m, a coating width of 200 mm, a temperature of 130 ° C. and a coating speed of 0.5 m / min so that the thickness after drying using a test coating machine is 50 μm. Worked. After the coating was completed, the glass window provided for observing the inside of the drying oven was observed to evaluate the contamination due to the volatilization of the adhesive depending on the presence or absence of fogging.
○: No fogging occurred on the glass window. (Good)
Δ: Some fogging occurred on the glass window, but the inside could be observed. (No problem in practical use)
X: Cloudiness occurred in the glass window, and the inside could not be visually observed. (Not practical)

<Wettability>
The obtained pressure-sensitive adhesive sheet was prepared in a size of 25 mm in width and 200 mm in length, 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 2.5 seconds to adhere (very good)
◯: More than 2.5 seconds and less than 3 seconds (good)
Δ: 3 seconds or more and less than 4 seconds until contact (no problem in practical use)
X: 4 seconds or more until adhesion, no wet spread (unusable)

  From the results of Tables 4 to 6, Examples 1-22 used organic acid diesters or triesters (C) having a low weight loss rate after heating, and therefore good results were obtained in both contamination evaluations. Therefore, the pressure-sensitive adhesive of the present invention enables high-speed coating with a high drying temperature, and can improve the productivity of the pressure-sensitive adhesive sheet. Furthermore, the re-peeling adhesive of the present invention was excellent in adherend contamination and wettability.

Claims (4)

Including a urethane resin (A), a curing agent (B), and a diester or triester (C) of an organic acid,
The organic acid diester or triester (C) is a re-peelable pressure-sensitive adhesive having a weight loss of 3% by weight or less after heating at 150 ° C. for 10 minutes.   The re-peelable pressure-sensitive adhesive according to claim 1, wherein the organic acid diester or triester (C) has a molecular weight of 300 to 600.   The re-peelable pressure-sensitive adhesive according to claim 1 or 2, comprising 0.5 to 50 parts by weight of the diester or triester (C) of the organic acid with respect to 100 parts by weight of the urethane resin (A). Agent.   A pressure-sensitive adhesive sheet comprising a substrate and a pressure-sensitive adhesive layer formed from the re-peelable pressure-sensitive adhesive according to claim 1.