JP5707715B2 - Urethane adhesive - Google Patents

Description

  The present invention relates to a urethane pressure-sensitive adhesive used for pressure-sensitive adhesive tapes and pressure-sensitive adhesive labels, and preferably surface protective pressure-sensitive adhesive sheets such as glass and mirror surfaces.

  In recent years, surface protective adhesive sheets have been used in order to prevent the surface of glass, mirrors, metals, plastics and the like from being stained or damaged. One of the pressure-sensitive adhesives constituting this is an acrylic pressure-sensitive adhesive. However, acrylic adhesives have excellent adhesive strength, but if they are applied to the adherend and then peeled off from the adherend again, the adhesive remains on the adherend due to the strength of the adhesive strength. There was a problem that it was poor (that is, adhesive residue), and in general, the adhesive strength increased with time after application, so that the removability was poor.

  On the other hand, various improvements have been made. For example, by using a urethane-based pressure-sensitive adhesive as disclosed in Patent Document 1, the problem of removability as described above has been solved. However, for example, when a sheet coated with an adhesive on a PET film is pasted as a protective sheet on a window glass or automobile glass, it is not easy to stick the air bubbles together or to remove the air bubbles that have been pinched. Absent. There are many insufficient points for adhesion to various adherends, in particular wettability at the time of sticking, and foam-removability, and improvements are strongly desired from the viewpoint of improving the efficiency of sticking work.

JP 2001-192636 A

In the present invention, while maintaining removability, adhesion to a substrate, wet spreadability (after the adhesive surface of the adhesive sheet is brought into contact with the adherend , the adhesive sheet adheres to the adherend with its own weight. It is an object of the present invention to provide a urethane-based pressure-sensitive adhesive having a good foam-removing property (whether or not bubbles that have been sandwiched at the time of application are removed when they are spread with a finger).

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have introduced a specific fatty acid ester into the urethane pressure-sensitive adhesive used for constituting the pressure-sensitive adhesive sheet. It has been found that a urethane pressure-sensitive adhesive having excellent pull-out properties can be obtained.

That is, in the first invention, the polyurethane polyol (A) is 50 to 85 % by weight, the polyfunctional isocyanate compound (B) is 0.5 to 20% by weight, and the fatty acid ester (C) having 10 to 30 carbon atoms. It is a urethane pressure-sensitive adhesive containing 0.5 to 31.5 % by weight.

  2nd invention is an adhesive tape characterized by having a base material and the adhesive layer formed from the urethane adhesive of the said invention.

  According to the present invention, it was possible to provide a urethane pressure-sensitive adhesive having good adhesion to a base material, wet spreadability, and foam removal property while maintaining removability.

First, the polyurethane polyol (A) used in the present invention will be described.
The polyurethane polyol (A) used in the present invention is obtained by reacting a polyester polyol (a1) and a polyether polyol (a2) with an organic polyisocyanate compound (a3) in the presence or absence of a catalyst. .

  A known polyester polyol is used as the polyester polyol (a1) used in the present invention. Examples of the acid component include terephthalic acid, adipic acid, azelaic acid, sebacic acid, phthalic anhydride, isophthalic acid, trimellitic acid, and the like, and the glycol component includes ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, 1,6-hexane glycol. , 3-methyl-1,5-pentanediol, 3,3′-dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, polyol component Examples 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.

  Although the molecular weight of the polyester polyol can be used from a low molecular weight to a high molecular weight, a polyester polyol having a number average molecular weight of 500 to 5,000 is preferably used. When the number average molecular weight is less than 500, the reactivity increases and gelation tends to occur. On the other hand, when the number average molecular weight exceeds 5,000, the reactivity becomes low, and the cohesive force of the polyurethane polyol (A) itself becomes small. The amount used is preferably 10 to 90 mol% in the polyol constituting the polyurethane polyol (A).

  As the polyether polyol (a2) used in the present invention, a known polyether polyol is used. For example, polyether polyols obtained by polymerizing oxirane compounds such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran using low molecular weight polyols such as water, propylene glycol, ethylene glycol, glycerin and trimethylolpropane as initiators Specifically, those having 2 or more functional groups such as polypropylene glycol, polyethylene glycol, and polytetramethylene glycol are used. The molecular weight of the polyether polyol can be used from a low molecular weight to a high molecular weight, but a polyether polyol having a number average molecular weight of 1,000 to 5,000 is preferably used. When the number average molecular weight is less than 1,000, the reactivity becomes high and gelation tends to occur. On the other hand, when the molecular weight exceeds 5,000, the reactivity is low, and the cohesive force of the polyurethane polyol (A) itself is low. The amount used is preferably 20 to 80 mol% in the polyol constituting the polyurethane polyol (A).

  Further, in the present invention, if necessary, a part thereof may be selected from glycols such as ethylene glycol, 1,4-butanediol, neopentyl glycol, butylethylpentanediol, glycerin, trimethylolpropane, pentaerythritol, ethylenediamine, N- It can be used in combination with polyamines such as aminoethylethanolamine, isophoronediamine, xylylenediamine and the like.

  As the polyether polyol (a2) used in the present invention, a bifunctional polyether polyol can be used, but the number average molecular weight is 1,000 to 5,000, and at least 3 or more in one molecule. By using part or all of the polyether polyol having a hydroxyl group, the balance between adhesive force and removability can be further increased. When the number average molecular weight is less than 1,000, a tri- or higher functional polyol is highly reactive and easily gelled. When the number average molecular weight exceeds 5,000, a tri- or higher functional polyol has low reactivity, and further, the cohesive force of the polyurethane polyol (A) itself is small. Preferably, a part or all of a polyol having a number average molecular weight of 2,500 to 3,500 and at least trifunctional or higher is used.

  Examples of the organic polyisocyanate compound (a3) used in the present invention include known aromatic polyisocyanates, aliphatic polyisocyanates, araliphatic polyisocyanates, and alicyclic polyisocyanates.

  As aromatic polyisocyanates, 1,3-phenylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate Isocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanatebenzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4 ', 4 "- And triphenylmethane triisocyanate.

  Aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4 , 4-trimethylhexamethylene diisocyanate and the like.

  As the aromatic aliphatic polyisocyanate, ω, ω′-diisocyanate-1,3-dimethylbenzene, ω, ω′-diisocyanate-1,4-dimethylbenzene, ω, ω′-diisocyanate-1,4-diethylbenzene, 1, Examples include 4-tetramethylxylylene diisocyanate and 1,3-tetramethylxylylene diisocyanate.

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

  Further, a trimethylolpropane adduct of the above polyisocyanate, a burette reacted with water, a trimer having an isocyanurate ring, and the like can also be used in combination.

  As the polyisocyanate used in the present invention, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, 3-isocyanate methyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate) and the like are preferable.

  As the catalyst used in the present invention, a known catalyst can be used. Examples thereof include tertiary amine compounds and organometallic compounds.

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

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

  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, Examples include triethyltin ethoxide, tributyltin ethoxide, dioctyltin oxide, tributyltin chloride, tributyltin trichloroacetate, and tin 2-ethylhexanoate.

  Examples of non-tin compounds include titanium compounds such as dibutyltitanium dichloride, tetrabutyltitanate and butoxytitanium trichloride, lead compounds such as lead oleate, lead 2-ethylhexanoate, lead benzoate and lead naphthenate, 2- Examples include iron series such as iron ethylhexanoate and iron acetylacetonate, cobalt series such as cobalt benzoate and cobalt 2-ethylhexanoate, zinc series such as zinc naphthenate and zinc 2-ethylhexanoate, and zirconium naphthenate. It is done.

  When these catalysts are used, problems such as gelation or turbidity of the reaction solution tend to occur in a single catalyst system due to a difference in reactivity in a system in which two types of polyols, a polyester polyol and a polyether polyol are present. . Therefore, by using two types of catalysts, the reaction rate, catalyst selectivity, etc. can be controlled, and these problems can be solved. As the combination, tertiary amine / organometallic system, tin system / non-tin system, tin system / tin system, etc. are used, preferably tin system / tin system, more preferably dibutyltin dilaurate and 2-ethylhexane. It is a combination of acid tin. The compounding ratio of the 2-ethylhexanoic acid tin / dibutyltin dilaurate is less than 1 by weight. Preferably it is 0.2-0.6. When the blending ratio is 1 or more, gelation tends to occur due to the balance of catalyst activity. The amount of these catalysts used is 0.01 to 1.0% by weight based on the total amount of polyol and organic polyisocyanate.

  The temperature when using the catalyst is preferably less than 100 ° C. More preferably, it is 85 degreeC-95 degreeC. If it is 100 ° C. or higher, it becomes difficult to control the reaction rate and the crosslinked structure, and it becomes difficult to obtain a polyurethane polyol (A) having a predetermined molecular weight.

  The synthesis of the urethane resin can be performed without a catalyst. In that case, the reaction temperature is preferably set to 100 ° C. or higher. More preferably, it is 110 degreeC or more. In the absence of a catalyst, the reaction is preferably performed for 3 hours or more.

  In order to obtain the polyurethane polyol (A), 1) a method in which the polyester polyol, polyether polyol, catalyst, and organic polyisocyanate are charged to the flask in a total amount, 2) a polyester polyol, polyether polyol, and catalyst are charged in the flask, and the organic polyisocyanate is charged. It is possible to add it dropwise. In particular, the method 2) is preferable for controlling the reaction.

  As the solvent used in the present invention, known solvents can be used. For example, methyl ethyl ketone, ethyl acetate, toluene, xylene, acetone and the like can be mentioned. In view of the solubility of the polyurethane polyol (A) and the boiling point of the solvent, toluene is particularly preferable.

  As the polyfunctional isocyanate compound (B) used in the present invention, the aforementioned organic polyisocyanate compounds and their trimethylolpropane adducts, burettes reacted with water, trimers having an isocyanurate ring, or the like are used.

  The fatty acid ester (C) used in the present invention has 10 to 30 carbon atoms. In the fatty acid ester having less than 10 carbon atoms, the fatty acid ester moves to the surface of the pressure-sensitive adhesive after sticking, and as a result, the adherend is contaminated. On the other hand, when the carbon number is larger than 30, the compatibility with the polyurethane polyol (A) is deteriorated, the cohesive force is lowered, and the removability is deteriorated.

  The fatty acid ester (C) used in the present invention is an ester of a monobasic acid or polybasic acid having 8 to 18 carbon atoms and a branched alcohol having 18 or less carbon atoms, or an unsaturated fatty acid having 14 to 18 carbon atoms. Or ester of alcohol of branched acid and tetrahydric or less alcohol is preferably used.

  Examples of the ester of a monobasic acid or polybasic acid having 8 to 18 carbon atoms and a branched alcohol having 18 or less carbon atoms include isostearyl laurate, isopropyl myristate, isocetyl myristate, octyldodecyl myristate, isopalmitate palmitate Stearyl, isocetyl stearate, octyldodecyl oleate, diisostearyl adipate, diisocetyl sebacate, trioleyl trimellitic acid, triisocetyl trimellitic acid, isopropyl myristate, isocetyl myristate, octyldodecyl myristate are preferred, myristic Isopropyl acid is particularly preferred.

Examples of the unsaturated fatty acid or branched acid having 14 to 18 carbon atoms include myristoleic acid, oleic acid, linoleic acid, linolenic acid, isopalmitic acid, and isostearic acid.
Specific examples of the tetravalent or lower alcohol include ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, and sorbitan.

The pressure-sensitive adhesive used in the present invention contains a polyurethane polyol (A), a polyfunctional isocyanate compound (B), and a fatty acid ester (C) having 10 to 30 carbon atoms as essential components. In 100% by weight, 50 to 95% by weight of polyurethane polyol (A), 0.5 to 20% by weight of polyfunctional isocyanate compound (B), and 0.5 to 10% of fatty acid ester (C) having 10 to 30 carbon atoms. It is preferable to contain ˜50% by weight, the polyurethane polyol (A) is 65 to 85% by weight, the polyfunctional isocyanate compound (B) is 10 to 15% by weight, and the fatty acid ester (C) having 10 to 30 carbon atoms. It is more preferable to contain 5 to 25% by weight.
When the polyfunctional isocyanate compound (B) is less than 0.5% by weight, the cohesive force as a pressure-sensitive adhesive is reduced, and when it exceeds 20% by weight, the adhesive force is reduced. When the fatty acid ester (C) having 10 to 30 carbon atoms is less than 0.5% by weight, the effect of adding the fatty acid ester hardly appears. When the fatty acid ester exceeds 50% by weight, the polyurethane polyol (main component of the pressure-sensitive adhesive) As a result of relatively less A), the cohesive force of the pressure-sensitive adhesive is insufficient and the removability is deteriorated.

  In the present invention, the urethane pressure-sensitive adhesive may contain additives such as talc, calcium carbonate, titanium oxide and the like, colorants, ultraviolet absorbers, antioxidants, antifoaming agents, light stabilizers and the like as necessary. May be.

  The pressure-sensitive adhesive tape of the present invention is obtained by applying the urethane pressure-sensitive adhesive to a base material.

  Examples of the substrate include plastic, polyurethane, paper, and metal foil. Examples of the shape include a sheet, a film, and a foam.

  Moreover, you may give an easily bonding process to the surface which contact | connects the adhesive of these base materials as needed. Specific examples include a method for treating corona discharge and a method for applying an anchor coating agent.

  In the present invention, conventionally known methods can be used as a coating method, for example, a roll coater method, a comma coater method, a die coater method, a reverse coater method, a silk screen method, a gravure coater method, and the like.

  In this invention, although the thickness (thickness after drying) of an adhesive layer changes also with uses of an adhesive tape, 0.1-200 micrometers is preferable.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

(Synthesis Example 1)
Polyester polyol P-1010 (bifunctional polyester polyol, OH number 112, molecular weight 1,000, manufactured by Kuraray Co., Ltd.) 81 weight in a 4-neck flask equipped with a stirrer, reflux condenser, nitrogen inlet tube, thermometer, and dropping funnel Parts, polyether polyol G-3000B (trifunctional polyether polyol, OH number 56, molecular weight 3,000, manufactured by Asahi Denka Co., Ltd.) 101 g, hexamethylene diisocyanate (manufactured by Sumitomo Bayer Co., Ltd.) 19 parts by weight, toluene 134 parts by weight Then, 0.05 parts by weight of dibutyltin dilaurate and 0.02 parts by weight of tin 2-ethylhexanoate are charged as a catalyst, and the temperature is gradually raised to 90 ° C. and the reaction is carried out for 2 hours. After confirming the disappearance of the remaining isocyanate groups by IR, the reaction was terminated by cooling to obtain a polyurethane polyol solution. This polyurethane polyol solution was colorless and transparent, had a nonvolatile content of 60%, a viscosity of 3,300 cps, Mn (number average molecular weight) = 15,000, and Mw (weight average molecular weight) = 46,000. The molecular weight measurement was carried out using Prominence manufactured by Shimadzu Corporation (column: TOSgelGMH × 2 connected by TOSOH, detector: RID-10A, solvent: THF, flow rate: 1 ml / min).

(Example 1)
For 100 parts by weight of the polyurethane polyol solution synthesized in Synthesis Example 1, 8.3 parts by weight of isopropyl palmitate (IPP) as a fatty acid ester (C) having 10 to 30 carbon atoms and a compound having an isocyanate group (B ) And 16.7 parts by weight of a 75% by weight ethyl acetate solution of hexamethylene diisocyanate trimethylolpropane adduct were mixed to obtain an adhesive.
The obtained pressure-sensitive adhesive was applied to a release paper so as to have a dry coating film thickness of 25 μm, dried at 100 ° C. for 2 minutes, and a polyethylene terephthalate film (film thickness 50 μm) was adhered. After coating, it was allowed to pass for 1 week at room temperature to obtain a test pressure-sensitive adhesive sheet. Using the pressure-sensitive adhesive sheet, the adhesive strength, re-peelability, wetting and spreading properties, and foam removal properties were tested according to the following methods.

<Adhesive strength>
Release the release paper of the test adhesive sheet obtained, and stick the exposed adhesive layer to a stainless steel plate (SUS304) with a thickness of 0.4 mm in a 23 ° C.-50% RH atmosphere. After the pressure bonding, the film was left for 24 hours or longer, and the peel strength (180 degree peel, pulling speed 300 mm / min; unit g / 25 mm width) was measured with a shopper type peel tester.

<Removability>
The release paper of the obtained pressure-sensitive adhesive sheet for test was peeled off, and the exposed pressure-sensitive adhesive layer was adhered to a glass plate, and then left for 24 hours under conditions of 40 ° C. and 80% RH. Then, after taking out to 23 degreeC-50% RH and leaving to stand for 30 minutes, re-peelability was evaluated visually.
The evaluation criteria are as follows.
◎: No adhesive layer transfer to glass plate ○: Very little adhesive layer transfer to glass plate Δ: Partial adhesive layer transfer to glass plate ×: Glass plate The adhesive layer transfer to has completely transferred

<Wet spreadability>
The obtained test pressure-sensitive adhesive sheet is cut into a 10 cm × 15 cm rectangle. Next, peel off the release paper, bring the exposed adhesive layer center part into contact with the glass plate while holding both ends of the adhesive sheet by hand, then release the hand until the entire adhesive layer sticks to the glass plate under its own weight. The wet spread state was evaluated by measuring the number of seconds. The evaluation criteria were as follows.
◎: Time required for the entire pressure-sensitive adhesive layer to adhere to the glass plate is less than 3 seconds ○: Time required for the entire pressure-sensitive adhesive layer to adhere to the glass plate is 3 seconds to less than 5 seconds △: Time required for the entire pressure-sensitive adhesive layer to adhere to the glass plate is 5 seconds or longer. ×: The entire pressure-sensitive adhesive layer hardly adheres to the glass plate.

<Bubble removal>
The obtained test pressure-sensitive adhesive sheet is cut into a 10 cm × 15 cm rectangle. Next, the release paper is peeled off and affixed on the glass plate so as to sandwich air bubbles on purpose. The sandwiched bubbles were spread with fingers, and the degree of bubble removal was evaluated. The evaluation criteria were as follows.
◎: Bubbles can be easily spread with fingers. ○: Bubbles can be spread by rubbing with a finger. Δ: Bubbles can be spread by rubbing with fingers. ×: Difficult to spread bubbles with fingers. Things

(Examples 2-3)
A test pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that 16.7 parts by weight (Example 2) and 33.3 parts by weight (Example 3) were added in an amount of isopropyl palmitate (IPP). , Evaluated in the same way.

Example 4
A test adhesive sheet was obtained in the same manner as in Example 1 except that 33.3 parts by weight of isopropyl myristate (IPM) as the fatty acid ester (C) was blended with respect to 100 parts by weight of the polyurethane polyol solution. .

(Comparative Example 1)
A test adhesive sheet was obtained in the same manner as in Example 1 except that the fatty acid ester (C) was not blended, and was similarly evaluated.

(Comparative Example 2)
Instead of the fatty acid ester (C), polyether polyol PP-2000 (bifunctional polyether polyol, OH value 56, manufactured by Sanyo Chemical Industries, Ltd.) was blended in an amount of 33.3 parts by weight with respect to 100 parts by weight of the polyurethane polyol solution. Except for the above, a test pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 and evaluated in the same manner.

(Comparative Example 3)
Instead of the fatty acid ester (C), Perex OTP (a mixture of sodium di-2-ethylhexylsulfosuccinate and methanol, manufactured by Kao Corporation) was added in an amount of 33.3 parts by weight per 100 parts by weight of the polyurethane polyol solution. In the same manner as in Example 1, a test pressure-sensitive adhesive sheet was obtained and evaluated in the same manner.

(Comparative Example 4)
Except that 33.3 parts by weight of Nicanol H-80 (liquid xylene resin, manufactured by Mitsubishi Gas Co., Ltd.) instead of the fatty acid ester (C) was added to 100 parts by weight of the polyurethane polyol solution, the same procedure as in Example 1 was performed. A test pressure-sensitive adhesive sheet was obtained and evaluated in the same manner.

In Comparative Example 1, since the fatty acid ester (C) having 10 to 30 carbon atoms is not added, the removability is good, but the wet spreading property and the bubble removal property are inferior. In Comparative Examples 2 to 4, a wetting agent was added instead of the fatty acid ester (C). However, the wetting spreadability and foam removal property were inferior compared to the Examples, the compatibility with the resin was poor, and the additive was It has been deposited on the surface of the adhesive.
On the other hand, in Examples 1 to 4, it was possible to provide a pressure-sensitive adhesive having good wetting and spreading properties while maintaining removability.

Claims (2)

50 to 85 % by weight of polyurethane polyol (A), 10 to 20% by weight of polyfunctional isocyanate compound (B), and 0.5 to 31.5% by weight of fatty acid ester (C) having 10 to 30 carbon atoms Urethane pressure-sensitive adhesive, characterized by   A pressure-sensitive adhesive tape comprising a base material and a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive according to claim 1.