JP2002129128A - Adhesive composition, polyurethane composition, and adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive composition which is extremely easy to control freely a recrystallization rate (or the finish time of recrystallization) of a polymer contained as a crystallization component and is capable of increasing effectively the easiness of peeling and the clean peelability. SOLUTION: The adhesive composition comprising a crystalline polymer and a crosslinked pressure-sensitive polymer, is characterized in that the crystalline polymer used is a polyurethane having a crystalline polyol unit in the molecule.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an adhesive composition containing a tackifying polymer and a polyurethane containing a crystalline polyol unit in a molecule. In particular, the present invention, after adhering to the adherend, when desired, by heating to a temperature higher than the melting point of the crystalline polyol, to reduce the peel strength to a value lower than the value before heating. The present invention relates to an improvement in an adhesive composition that can be easily peeled. Such an adhesive composition is particularly useful, for example, as an adhesive used for an adhesive layer of an adhesive sheet or an adhesive tape.

[0002]

BACKGROUND OF THE INVENTION 1. Adhesives Containing Polyurethane Adhesives containing polyurethane have hitherto been used in various applications. For example, Japanese Patent Laid-Open No. 6-1
No. 0848 discloses a heat-sensitive adhesive containing polyurethane as a thermoplastic resin. The heat-sensitive adhesive disclosed herein is a thermoplastic resin such as polyurethane,
It consists of a composition comprising a combination of a tackifier, a crystalline plasticizer and a colloid. The crystalline plasticizer refers to a low-molecular-weight one such as diphenyl phthalate or dihexyl phthalate. The crystalline plasticizer can, on the one hand, soften the thermoplastic resin upon melting to give the heat-sensitive adhesive a tackiness, and on the other hand, reduce the tackiness at room temperature (about 25 ° C.). However, the crystalline plasticizer softens to some extent depending on conditions such as a storage temperature even at a temperature lower than the melting point, and imparts plasticity to the resin to cause blocking. Therefore, in order to improve the blocking resistance of the adhesive surface of the adhesive, it was necessary to contain a colloid. The colloid is
For example, inorganic particles such as colloidal silica. This publication does not disclose the use of a polyurethane containing a crystalline polyol unit in the molecule as a thermoplastic resin. Also, no composition containing a tacky polymer in combination with a polyurethane is disclosed.

JP-A-7-53939 discloses a tacky / adhesive composition having good adhesiveness to both polyolefins and polyurethanes and having oil resistance. The adhesive / adhesive composition disclosed herein contains a diene polymer or a hydrogenated product thereof, a polymer polyol, and an isocyanate compound. The diene polymer or a hydrogenated product thereof has a number average molecular weight of from 1.5 to 5.0 having 1.5 to 5.0 hydroxyl groups in one molecule.
000, and can be obtained, for example, by radical polymerization of isoprene monomer. As the isocyanate compound, for example, isophorone diisocyanate can be used. The amount of the polymer polyol is 1.5 to 5.
Number average molecular weight having 0 hydroxyl groups is 300 to
It is a crystalline polyol having a crystallinity of 10,000. As such a crystalline polyol, a polycondensate of 3-methyl-1,5-pentanediol and terephthalic acid is preferably mentioned from the viewpoint of compatibility with other essential components. In addition to the above components, a tackifying resin may be contained as long as the adhesive strength and oil resistance are not impaired. The diene-based polymer or a hydrogenated product thereof is a polymer exhibiting tackiness and adhesiveness. This composition has good tackiness and adhesion to both polyolefins and polyurethanes, and can be used as a tacky / adhesive having excellent oil resistance. One of the features of this composition is that the crystalline polymer polyol is crosslinked with an isocyanate compound. However, this publication does not propose to crosslink the diene-based polymer (and its hydrogenated product). Also, when using this adhesive / adhesive composition, it is not assumed that the adhesive composition is finally adhered, peeled during use or after use is completed. Further, “crystalline” as defined in this publication means that the polymer polyol has a melting point. However, controlling the crystallinity of polyurethane obtained by polymerization with a polymer polyol and an isocyanate compound is not disclosed in this publication.
Further, it does not describe how the crystallinity of the polymer polyol contributes to the performance of the adhesive and the adhesive. Furthermore, it is not disclosed that polycaprolactone can be used as the polymer polyol.

On the other hand, JP-A-8-27282 discloses that
An isocyanate group-containing crystal that can be bonded to inorganic porous materials such as porous ceramics and lightweight cement boards with practical strength in a relatively short time even under low temperature conditions such as 10 ° C or lower and low humidity conditions. A polyurethane-based adhesive is disclosed. The isocyanate group-containing crystalline polyurethane adhesive has a solid content of 10 to 80% by weight and is made of a solution of an inert organic solvent which does not react with isocyanate groups such as xylene and acetone. When the solvent permeates into the surface layer of the porous material and the solvent evaporates, the adhesive precipitates and crystallizes. A cohesive force is developed by crystallization and adheres with a certain level of strength.
Alternatively, it reacts with water to polymerize, completely hardens and joins strongly. The isocyanate group-containing crystalline polyurethane has a molecular weight of several thousand to tens of thousands obtained by reacting an excess of a polyisocyanate compound with an alcohol such as a polyester polyol or a polyether polyol. However, there is no disclosure of using a sticky polymer.

Japanese Patent Application Laid-Open No. Hei 10-245536 discloses that the crystal hardening time can be shortened and adjusted without changing the composition of a polyol of a urethane prepolymer having crystallinity.
A reactive hot melt adhesive is disclosed. The reactive hot melt adhesive containing the urethane prepolymer as a main component is characterized in that a nucleating agent, for example, a wax or a wax mixture is added in an amount of 0 to 10% by weight. If necessary, a thermoplastic polymer, a tackifier resin, a filler, a catalyst, a pigment, and the like are added. It is described that, for example, polyurethane or the like can be used as the thermoplastic polymer. In addition, there is no disclosure of using an adhesive polymer. In addition, the adjustment of the crystal hardening time is performed not by changing the composition of the polyol but by the amount and type of the nucleating agent. The urethane prepolymer having the above crystallinity can be obtained by reacting a polyol such as a polyester polyol with a polyisocyanate. However, the use of polycaprolactone as a polyol is not disclosed. As the polyisocyanate, isophorone diisocyanate and the like are disclosed. In the above publication, it has not been proposed to effectively use an adhesive or an adhesive composition containing a combination of a crystalline polyurethane and a tacky polymer.

[0006] 2. Adhesives containing crystalline polymers On the other hand, adhesives containing crystalline polymers other than polyurethane have been disclosed in several documents. For example, JP-A-2000-119624 discloses an adhesive composition comprising a specific tacky polymer and a polyester such as polycaprolactone. Using the adhesive composition disclosed herein, the article can be bonded to the adherend by thermocompression bonding (compression bonding after heating, or compression while heating). The adhesive polymer disclosed herein is required to have two functional groups of a hydroxyl group and a phenyl group in a molecule. By the action of these functional groups, compatibility with polycaprolactone is improved.

Further, US Pat. No. 5,412,035 (corresponding to Japanese Patent Publication No. Hei 6-510548) discloses a pressure-sensitive adhesive which becomes a pressure-sensitive adhesive at at least one temperature in the range of 20 ° C. to 40 ° C. An adhesive composition, which is a polymer pressure-sensitive adhesive component and an adhesive composition (pressure-sensitive adhesive) comprising a crystalline polymer, is disclosed. The crystalline polymer is usually non-tacky at room temperature and is intimately mixed with the polymer pressure-sensitive adhesive component. If the melting point of the crystalline polymer itself is Tm ° C,
Melting point of crystalline polymer Ta ° C. as measured in the composition
Is lower than Tm, and Tm−Ta is preferably 1 ° C. to 9 ° C. It is noted that Tm is preferably from 20C to 102C. This composition has a so-called thermal peeling in which the peeling strength P2 [g / cm] at a certain temperature higher than Ta is smaller than the peeling strength P1 [g / cm] at a certain temperature lower than Ta. It is an adhesive having ease (referred to as a heat-peelable adhesive or a heat-peelable adhesive). This publication does not disclose the use of polycaprolactone as a crystalline polymer or the use of crystalline polyurethane having a crystalline polyol unit such as polycaprolactone in the main chain molecule.

On the other hand, although there is no description about the ease of thermal peeling, International Patent Publication No. WO 91/6424 (US Pat. Nos. 5,192,612 and 5,346,766;
European Patent Application Publication No. 451260, Japanese Patent No. 302
No. 1646) discloses a pressure-sensitive adhesive containing a pressure-sensitive adhesive base resin (adhesive polymer such as an acrylic polymer), a deadhesive resin and deadhesive fine particles. Specific and preferred examples of the deadhesive resin include about 3,0
Substantially linear polycaprolactone having a molecular weight of from about 00 to about 342,000 is disclosed. Polycaprolactone is a crystalline polymer that is non-tacky at room temperature (about 15 ° C. to 30 ° C.). The above-mentioned pressure-sensitive adhesive can be bonded by pressing toward the adherend at room temperature. On the other hand, the deadhesive resin as described above, in cooperation with the deadhesive particles,
The tack on the adhesive surface at room temperature is effectively reduced, and the removability is enhanced. The term “removability” refers to a property in which adhesion-peeling-reattachment-repeeling is possible before final bonding, and repositioning or position adjustment is easy. Removability is Re
It is also known in the art as terms such as positionability. Note that this publication does not assume that peeling is performed during use or after use is completed after the final adhesion.

Further, as a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing a crystalline component, International Patent Publication WO97 / 4
No. 6,633 (US Pat. No. 5,889,118) and WO 97/46631. In the pressure-sensitive adhesive layer of this pressure-sensitive adhesive sheet, a crystalline acrylate component is introduced as a continuous layer into the pressure-sensitive adhesive polymer. Note that these publications do not describe improvement in thermal peelability, which facilitates peeling by heating after final bonding, during use, or after use is completed.

[0010] 3. Current Status of Peelable Adhesives Conventional peelable adhesives are still insufficient in terms of overall required performance. For example, it is still improved in the property that it can be peeled cleanly (peeling cleanability) without leaving an organic component of the adhesive (a polymer component such as an adhesive polymer or a low molecular weight component of a crystalline polymer) on the adherend. There was room for On the other hand, after heating the adhesive above the melting point of the crystalline polymer, it is also possible to freely control the rate at which the crystalline polymer recrystallizes (or the time until recrystallization is completed). It was difficult with adhesives containing polymers. For example, in order to control the recrystallization rate of a crystalline polymer, it is possible to adjust the molecular weight of the crystalline polymer. However, if the molecular weight of the crystalline polymer is too large, the compatibility with the adhesive polymer may be reduced, and the ease of peeling may be reduced. Conversely, if the molecular weight of the crystalline polymer is too small, there is a possibility that the delamination detergency may decrease.

By the way, if the recrystallization rate of the crystalline polymer can be controlled, for example, the time during which the easy-peeling state can be maintained during the heat-peeling operation, that is, the easy-peeling time, is lengthened or shortened. It is very advantageous for. On the other hand, in the case of the conventional adhesive, the above-mentioned effect of easy thermal peeling is relatively quickly lost when the temperature of the adherend falls below a predetermined temperature, and it has been difficult to extend the easy peeling time. For example, in about 2 to 3 minutes after heating, the peel strength of the adhesive is restored to almost the same level as before heating, and peeling becomes difficult.

Such an adhesive is used, for example, for an adhesive layer of an outdoor adhesive sheet (exterior decorative sheet, sign reflective sheet, etc.), and a peeling operation is performed under relatively low ambient temperature conditions such as in winter. In this case, before the entire surface of the sheet is peeled, the temperature of the once heated adherend is cooled (natural cooling) to a temperature lower than a predetermined temperature. In the case of an outdoor adhesive sheet having a relatively large area (usually 400 cm ² or more), the following problem occurs. That is, after heating a certain portion of the adherend from above the adhesive sheet, while heating another portion, cooling starts in a once heated portion.
Further, even when the whole can be heated uniformly, cooling is started in another part while the adhesive sheet is being peeled in one part. That is, when the peelable time is short, the peeling operation becomes difficult.

In the case of an adhesive sheet having relatively small components (such as electronic components) as adherends, the following problems occur. In other words, when peeling the adhesive sheet from relatively small parts, multiple parts are put together in an oven or the like and heated,
It is efficient to remove them all from the oven and perform the stripping operation. However, if the number of components is relatively large, the remaining components will be cooled while working on some components. Furthermore, after using for a relatively long time (several months or more), it may be required to peel off the adhesive sheet from the adherend. When the article is peeled off from the adherend after being used for a long time, the adhesive layer has a strong tendency to undergo cohesive failure and remain on the adherend (leave a polymer component such as an adhesive polymer). Such adhesive residue should be particularly prevented when the adherend is recycled.

However, the above-mentioned publication does not disclose any specific means for solving the above-mentioned problems. In the above-mentioned publication, after peeling,
No re-adhesive hot-peelable adhesive is disclosed. In this way, it is possible to re-adhere after peeling,
This is an important property when it is necessary to replace or recycle the sign substrate, which is the adherend, and to change the bonding position on the substrate surface. In such applications, an adhesive which can be easily re-adhered only by a pressure bonding operation is particularly advantageous. Therefore, in the application as a heat-peelable adhesive, (I) after bonding to an adherend, at a desired time, heating to a predetermined temperature and reducing the peel strength to a value lower than the value before heating. (II) The easy peeling state can be maintained for a predetermined time,
(III) It is peelable while keeping the adherend clean, and (I)
V) There is a strong demand that it can be easily re-adhered to an adherend (including another adherend after replacement) after peeling.

[0015]

That is, a first object of the present invention is to extremely easily control the recrystallization speed (or recrystallization completion time) of a polymer contained as a crystalline component. Another object of the present invention is to provide an adhesive composition capable of effectively improving the ease of peeling and the cleanability of peeling. A second object of the present invention includes a crystalline polyurethane capable of freely controlling the recrystallization rate (or recrystallization completion time) without reducing the compatibility with the adhesive polymer. To provide a polyurethane composition for an adhesive. A third object of the present invention is to provide an adhesive layer containing a crystalline polyurethane, and a recrystallization rate (or recrystallization completion time) of the polyurethane.
It is an object of the present invention to provide an adhesive sheet in which the adhesive sheet can be freely controlled, whereby the ease of peeling and the cleanability of peeling are effectively improved.

[0016]

According to the present invention, there is provided an adhesive composition comprising a crystalline polymer and an adhesive polymer, wherein the adhesive polymer is crosslinked. And an adhesive composition, wherein the crystalline polymer is a polyurethane having a crystalline polyol unit in a molecule. In order to achieve the second object, the present invention provides a polyurethane composition used for producing the adhesive composition of the present invention, wherein a starting material substantially consisting of polycaprolactone and diisocyanate is polymerized. A polyurethane composition characterized by comprising the polyurethane obtained by the above. Further, in order to achieve the third object, the present invention comprises a substrate and an adhesive layer comprising the adhesive composition of the present invention fixedly arranged on at least one surface of the substrate. Providing an adhesive sheet.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Action] In the adhesive composition of the present invention, the adhesive polymer is crosslinked, and the polyurethane contained as a crystalline polymer component is a polyurethane having a crystalline polyol unit in the molecule. It is. Therefore, the recrystallization rate (or recrystallization completion time)
Is extremely easy to control, and the ease of peeling and the cleanliness of peeling can be effectively increased. That is, in the present invention, it is possible to control the molecular weight of the crystalline polyol unit and control the recrystallization rate (or recrystallization completion time). Therefore, in the crystalline polyol unit, which is the crystalline polymer portion, several crystalline units can be linked by urethane bonds while keeping the molecular weight per unit small. This makes it possible to increase the molecular weight of the entire polyurethane as much as possible and effectively prevent a decrease in peeling cleanability. On the other hand, since the molecular weight per one crystalline unit is small, the recrystallization rate can be slowed (reduced). When the recrystallization speed is low, the recrystallization completion time becomes long, so that when the adhesive is used as an adhesive which is easy to thermally peel, the easy peel time can be increased. When the molecular weight per crystalline unit is small, the degree of crystallinity can be reduced, so that the surface tack of the adhesive composition at room temperature (about 25 ° C.) can be effectively increased.

On the contrary, the recrystallization rate can be increased (increased) by increasing the molecular weight of one crystalline polyol unit. In this case, 1
Without unnecessarily increasing the molecular weight of one crystalline unit
Some crystalline polyol units can be linked by urethane linkages to increase the overall molecular weight of the polyurethane. Therefore, it is possible to effectively prevent a decrease in compatibility with the adhesive polymer due to an excessive molecular weight of the crystalline unit. Thereby, a decrease in the ease of peeling can be effectively prevented. When the molecular weight per crystalline unit is large, the degree of crystallinity can be increased, so that the surface tack of the adhesive composition at room temperature (about 25 ° C.) can be effectively reduced.

(Polyurethane) The polyurethane used in the present invention usually has a crystalline polyol unit in the main chain molecule. When the crystalline polyol unit is present not in the side chain but in the main chain molecule, even if the crystalline polyol unit is formed from a polyol compound having a relatively short molecular chain (that is, a relatively low molecular weight), It is easy to increase the degree of crystallization and the rate of crystallization. Therefore, it is advantageous to increase the degree of crystallization and the crystallization rate of the polyurethane without impairing the compatibility with the adhesive polymer.

The crystalline polyol unit is formed from a crystalline polyol compound. That is, the polyol compound is incorporated into the urethane molecule by the reaction between the isocyanate compound such as diisocyanate and the polyol compound, and forms a crystalline polyol unit as a repeating unit. In the present specification, "polyol compound"
The term refers to a polymer or oligomer that is substantially non-tacky at room temperature (about 25 ° C.) and has two or more hydroxyl groups in the molecule. Further, the number of hydroxyl groups of the polyol compound is preferably substantially 2 from the viewpoint of easily controlling the degree of crystallization and the rate of crystallization. Note that “crystalline” refers to a property that can be melted by heating.

Generally, the weight average molecular weight of the polyol compound is usually 1,000 to 200,000, preferably 1.5 to 1.5.
00 to 50,000, particularly preferably 3,000 to 15,
000. If the weight average molecular weight is too small, the crystallinity may not be effectively increased, and the ease of thermal peeling may be reduced. On the other hand, if it is too large, it may be difficult to control the crystallization rate, or the compatibility with the adhesive polymer may be reduced, and the above-mentioned predetermined effect may not be obtained. In this specification, "molecular weight"
Is the molecular weight in terms of polystyrene measured using GPC.

As the crystalline polyol compound, for example, a crystalline polyol compound is selected from polyester polyol, polyether polyol, polycarbonate polyol and the like. For example, from the viewpoint of easily controlling the crystallinity (crystallinity and crystallization rate) of polyurethane, a preferred polyester polyol is polycaprolactone. From the same viewpoint, a suitable polyether polyol is polytetramethylene glycol. The polyol compound may be one kind or a mixture of two or more kinds.

On the other hand, the chemical structure and steric structure of the isocyanate compound (cyclic or linear, aliphatic or aromatic, etc.)
Is not particularly limited, and the crystallinity and crystallization rate of the polyurethane can be freely controlled by these structures. The isocyanate compound is usually a diisocyanate having two isocyanate groups in the molecule. Examples of the diisocyanate include isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI), hydrogenated MDI,
A mixture containing one or more diisocyanates selected from the group consisting of tolylene diisocyanate (TDI) and 1,6-hexanediol diisocyanate (HDDI) can be used. Further, a compound having a biuret structure or an isocyanurate structure, which is obtained by reacting the above-described diisocyanates, can also be used. Preferred as the isocyanate compound is an alicyclic diisocyanate such as isophorone diisocyanate. Without reducing the compatibility of the polyurethane with the tacky polymer,
This is because it is particularly easy to control the crystallinity of the polyurethane as a whole.

Further, in order to further facilitate the control of crystallinity, the starting material used for the polymerization of polyurethane does not contain a chain extender (short-chain diol) and consists essentially of a polyol compound and a diisocyanate. Is preferred.
In this case, a particularly suitable polyol compound is polycaprolactone. In order to deactivate the terminal isocyanate residue of the polyurethane molecule, a lower monohydric alcohol may be used. In this case, a monohydric alcohol residue is introduced into the end of the polyurethane molecule, but the molecular main chain other than the end substantially comprises a polymerized unit formed from a polyol compound and a diisocyanate.

On the other hand, although the details will be described later, it is preferable that the adhesive polymer be compatible with the polyurethane at a temperature higher than the melting point of the crystalline polyol unit in the adhesive composition. Thereby, control of the surface tack becomes easy, and the thermal peelability can be effectively improved.
The “melting point of the crystalline polyol unit” means the melting point of a crystalline polyol compound that is a raw material of urethane.
The melting point of the crystalline polyol compound is usually from 30 to 70 ° C, preferably from 35 to 65 ° C, particularly preferably from 4 to 70 ° C.
0-60 ° C.

The polyurethane is formed (polymerized) by, for example, heating a liquid formed by dissolving or dispersing the starting materials in a solvent while stirring. Examples of the solvent include compounds containing no active hydrogen such as ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, aromatic hydrocarbon solvents such as toluene and xylene, and ester solvents such as ethyl acetate. Available.

The mixing ratio of the polyol compound and the isocyanate is usually such that OH contained in the total amount of the polyol compound is
Ratio of the number of moles of the group (H1) to the number of moles of the NCO group (N1) contained in the total amount of the isocyanate compound (H1: N
1), and this ratio is usually 1: 1 to 1: 1.6.
0, preferably in the range of 1: 1.01 to 1: 1.50. Further, a catalyst used for usual polymerization of polyurethane, for example, dibutyltin laurate and the like can also be used. When polyurethane is polymerized in a solvent as described above, a solution (or dispersion) containing polyurethane is directly used as a polyurethane composition for an adhesive for producing the adhesive composition of the present invention. Can be used.

The molecular weight of the polyurethane may be within a range in which a predetermined adhesive force is exhibited, and the weight average molecular weight is usually 5,000 to 200,000, preferably 10,000.
-100,000, particularly preferably 15,000-8
It is in the range of 0000. If the molecular weight is too small, there is a possibility that the peeling cleanliness is reduced, and if it is too large, on the contrary,
The compatibility with the adhesive polymer may be reduced, and the above-mentioned predetermined effect may not be obtained.

(Polycaprolactone) As described above, a preferable example of the polyol compound is polycaprolactone. The polycaprolactone suitably used in the present invention means (i) polycaprolactone obtained by polymerizing a starting material containing caprolactone, or (ii) a polymerized unit (unit) obtained by ring-opening polymerization of caprolactone. And polycaprolactone contained in the molecule. In a composition containing an adhesive polymer and a polyurethane obtained from polycaprolactone, almost no adhesiveness can be eliminated at room temperature by crystallization of the polycaprolactone portion (polyol unit). However, by applying pressure to the adherend at room temperature or while heating, a predetermined adhesive force can be developed. If stronger bonding is required, thermocompression bonding can be used.

(Tacky Polymer) The tacky polymer used in the present invention is a polymer which exhibits tackiness at normal temperature (about 25 ° C.), and when heated to a temperature not lower than the melting point of the polyol unit contained in the polyurethane, Preferably, it is compatible with the polyurethane. The adhesive polymer is preferably crosslinkable. When the adhesive composition is used as a heat-peelable adhesive, the adhesive polymer is particularly preferably crosslinked.

Whether or not the tacky polymer is compatible with the polyurethane when heated to a temperature equal to or higher than the melting point of the polyol unit can be determined by the transparency (that is, change (decrease) in haze) of the adhesive composition. For example, a film adhesive (film-like adhesive) composed of the adhesive composition of the present invention and having a thickness in the range of 30 to 60 μm is heated to a temperature higher than the melting point of the polyol unit and lower than the melting point (normal temperature,
About 25 ° C is good. ). At room temperature, polyurethane usually forms a plurality of fine crystals, and the polyurethane is dispersed in a matrix containing an adhesive polymer, so that the transparency is relatively high, but the haze measured using a color difference meter is at least. 5% or more (usually 20% or less). On the other hand, at a temperature higher than the melting point of the polyol unit, the polyurethane melts, and when the polyurethane and the tacky polymer are compatible with each other, the haze is reduced and the film adhesive becomes almost transparent. Further, even when the polyurethane is melted, the haze hardly changes when the polyurethane and the adhesive polymer are not compatible. In such a case, the smaller the haze, the better the compatibility. Therefore, the haze measured using a color difference meter is preferably 3% or less, particularly preferably 2% or less when the polyurethane and the adhesive polymer are compatible.

Further, the compatibility of these two polymers can be easily determined by whether or not the solution containing the polyurethane and the adhesive polymer is transparent. That is, one of the prerequisites for good compatibility between the adhesive polymer and the polyurethane is a transparent first solution containing the dissolved adhesive polymer and a transparent second solution containing the dissolved polyurethane. Are mixed to form a transparent mixed liquid.

Also, by examining the transmittance of polarized light using a polarizing microscope, it can be confirmed whether or not the polyurethane and the adhesive polymer are compatible. As is well known, when the polarization axes of two polarizing plates are orthogonal to each other, light is not transmitted, and the visual field is almost completely dark. A film adhesive made of the adhesive composition of the present invention is placed between the two polarizing plates orthogonal to each other in this manner, and observed. At room temperature, the microcrystals of polyurethane rotate the plane of polarization of the light incident on the film adhesive and transmit the two polarizing plates. Since the direction of the crystal axis is usually random,
Crystals that transmit the two polarizing plates by rotating the polarization plane by exactly 90 degrees and crystals that do not easily pass light are mixed. The smaller and more dispersed the microcrystals of the polyurethane, the higher the compatibility between the polyurethane and the adhesive polymer. Therefore, the higher the compatibility of the polymers with each other, the smaller the crystal size, and the whole film looks slightly brighter in a microscope visual field (100 to 200 times). When the compatibility of the polymers is low, the crystal size is large and the crystals are visible as bright dots scattered on a dark base. In the state where the polyurethane is melted and the tacky polymer and the polyurethane are compatible with each other, the mixture of these polymers contained in the film adhesive is optically isotropic, and therefore becomes darker than at room temperature. .

Examples of the adhesive polymer include an acrylic polymer and a nitrile-butadiene copolymer (NBR).
Styrene-butadiene copolymers (SBR, etc.),
Non-crystalline polyurethane, silicone-based polymer and the like. The adhesive polymer is composed of one of these polymers alone or a mixture of two or more thereof.

When the polyol unit of the polyurethane is polycaprolactone, that is, when the polyurethane is a polycaprolactone-based polyurethane, in order to increase the compatibility between the polyurethane and the tacky polymer, for example, the tacky polymer is incorporated into the molecule. It preferably has (a) a hydroxyl group and (b) a phenyl group as essential functional groups. In addition, in order to impart crosslinking properties,
(C) It is preferable to have a cross-linking functional group as an essential functional group. The crosslinking functional group is a functional group capable of performing a crosslinking reaction by irradiation with electromagnetic waves (including ultraviolet rays), an electron beam, or the like, or by heating, and is a functional group that usually reacts with a crosslinking component contained in the adhesive composition. . Further, the adhesive polymers may be directly crosslinkable via a crosslinkable functional group.
Details of the crosslinking functional group and the crosslinking component will be described later.

The polymer having the essential functional group in the molecule is a mixed monomer containing a monomer having a hydroxyl group in the molecule, a monomer having a phenyl group in the molecule, and a monomer having a cross-linking functional group in the molecule. It can be obtained by polymerization using (starting monomer). Alternatively, after the polymerization, a carboxyl group in the molecule may be reacted to be converted into a hydroxyl group and a phenyl group.

Here, a preferred example of an acrylic polymer that can be used in combination with the polycaprolactone-based polyurethane in the present invention will be described. Such polymers include (A) a (meth) acrylic monomer having a hydroxyl group in the molecule, (B) a (meth) acrylic monomer having a phenyl group in the molecule, and (C) a crosslinking functional group in the molecule. A (meth) acrylic monomer having
(D) An acrylic polymer obtained by polymerizing a mixed monomer containing an alkyl acrylate having an alkyl group having 4 to 10 carbon atoms. Such a polymer can be prepared by copolymerization by a usual method, for example, solution polymerization or the like.

The component (A) includes, for example, 2-hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, Hydroxy-3-phenoxypropyl acrylate and the like can be mentioned. Among them, 2-
Monomers containing both hydroxyl and phenyl groups in the molecule, such as hydroxy-3-phenoxypropyl acrylate, are preferred. Thereby, the compatibility of the adhesive polymer with the polyurethane can be particularly effectively increased. As the component (B), for example, those having a phenoxy group as a phenyl group such as phenoxyethyl acrylate and phenoxypropyl acrylate are preferable.

As the component (C), those having a thermally crosslinkable functional group such as an unsaturated acid such as (meth) acrylic acid and an epoxy group-containing (meth) acrylic monomer such as glycidyl (meth) acrylate are used. it can. Alternatively, a (meth) acrylic monomer having an unsaturated double bond and the photocrosslinkable functional group in the molecule, such as acryloylbenzophenone, may be used to form a photocrosslinkable adhesive polymer. The component (C) may include both a heat crosslinkable functional group and a photocrosslinkable functional group, and may be crosslinkable by both heat and light. Examples of the component (D) include n-butyl acrylate, isobutyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, and the like. The component (D) does not have the functional groups (a) to (c) in the molecule.

The ratio (mass percentage) of the total of the units derived from the components (A) and (B) to the total polymerized units of the above-mentioned adhesive polymer is usually 40 to 9%.
0% by weight, preferably 41 to 85% by weight, particularly preferably 4% by weight.
2 to 80% by mass. If the units derived from the components (A) and (B) are too small, the compatibility with the polyurethane may be reduced. Conversely, if the units are too large and the components having other functional groups are too small, crosslinking may occur. There is a possibility that the properties and adhesiveness are reduced, and the above-mentioned predetermined performance cannot be effectively improved. For example, a decrease in crosslinkability may impair the adhesive residue prevention effect. In addition, a decrease in the tackiness of the tacky polymer itself may result in adhesion by pressure bonding between the adherend and the adherend, that is, there is a possibility that the pressure-bonding performance is reduced. When importance is placed on such pressure-bonding performance, the total ratio of units derived from the components (A) and (B) is 42 to
A range of 60% by mass is preferred.

The proportion of the unit derived from the component (B) in the total polymerized units of the adhesive polymer is at least 0.5 mol%, preferably at least 1 mol%, particularly preferably 5 to 25 mol%.
Mol%. If the number of units derived from the component (B) is too small, the compatibility with the polyurethane may decrease,
Conversely, if there are too many units derived from the component (B), the pressure-bonding performance may be reduced. On the other hand, the total ratio (mass percentage) of the units derived from the component (C) in the total polymerized units of the adhesive polymer is usually 0.5 to 1%.
It is from 5% by weight, preferably from 0.7 to 10% by weight, particularly preferably from 1 to 7% by weight.

As long as the effects of the present invention are not impaired, the above-mentioned adhesive polymer may be used in addition to the above-mentioned polymer containing essential functional groups (hydroxyl group, phenyl group, and cross-linking functional group), and a polymer having no such functional group. They can be used together. However, the proportion of the polymer containing these essential functional groups in the entire adhesive polymer (total mass) is usually 50% by mass or more, preferably 60% by mass or more, and particularly preferably 70% by mass or more.

On the other hand, as another preferred example of the acrylic polymer having good compatibility with the polycaprolactone-based polyurethane, (i) an alkyl acrylate mixture composed of 2-ethylhexyl acrylate, butyl acrylate, and methyl acrylate; An acrylic polymer obtained by polymerizing a mixed monomer containing acrylic acid or methacrylic acid can be used. Such an acrylic polymer also has good compatibility with the polyol. When such a polymer is used as the tacky polymer, the adhesive composition preferably contains a crosslinking component that reacts with the carboxyl group of (meth) acrylic acid in the above (ii). The ratio (mass percentage) of the units derived from the component (i) to the total polymerized units of such an adhesive polymer is usually 70 to 99% by mass, preferably 80 to 97% by mass. Particularly preferably 85 to 9
5% by mass. On the other hand, the total ratio (mass percentage) of the units derived from the component (ii) is usually 0.5%.
It is from 30 to 30% by mass, preferably from 2 to 20% by mass, particularly preferably from 4 to 15% by mass.

The molecular weight of the pressure-sensitive adhesive polymer used in the present invention may be within a range where a predetermined adhesive force is exhibited, and is usually 10,000 to 1,000,000 in weight average molecular weight.
It is in the range of 0. Also, like conventional pressure-sensitive adhesives,
Tackifiers can also be used with the tacky polymer.

(Cross-Linking Functional Group) The cross-linking functional group of the adhesive polymer is preferably a functional group different from (a) a hydroxyl group and capable of reacting with a thermal cross-linking component. Preferably, the crosslinking functional group contains at least one of a carboxyl group and an epoxy group. Also, both may be included at the same time. In such a case, a suitable thermal crosslinking component is a compound having in its molecule two or more crosslinking functional groups capable of reacting with a carboxyl group and / or an epoxy group, which are crosslinking functional groups of the adhesive polymer. It is not particularly limited. Such compounds are usually monomers or oligomers.

Suitable combinations of the crosslinking functional group of the adhesive polymer and the thermal crosslinking component include the following. When the crosslinking functional group is a carboxyl group, a bisamide-based crosslinking agent or an epoxy resin is suitable as the thermal crosslinking component. When the crosslinking functional group is an epoxy group, rosin having a carboxyl group in the molecule (carboxyl rosin) is suitable as the thermal crosslinking component. Regardless of whether the crosslinking functional group is a carboxyl group or an epoxy group, thermal crosslinking can be performed without hindering the compatibilizing action of the hydroxyl group and the phenyl group of the adhesive polymer with the polyol. Further, a sufficient crosslinking density to enhance the heat resistance as an adhesive and the effect of preventing adhesive residue can be easily achieved by a thermal crosslinking reaction. In the above case,
A carboxyl rosin can be used in combination, and in the above case, an epoxy resin and / or a bisamide-based crosslinking agent can be used in combination. When the cross-linking functional group is a carboxyl group, an isocyanate-based cross-linking agent can be used as long as the effect of the present invention (such as facilitating the recrystallization speed of polyurethane) is not impaired.

(Crosslinking Component) The epoxy resin reacts with the carboxyl group of the adhesive polymer and acts to thermally crosslink the adhesive polymer. As the epoxy resin, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, cresol novolak type epoxy resin, phenol novolak type epoxy resin and the like can be used. The epoxy equivalent of the epoxy resin is usually 70 to 40.
0, preferably 80-300. As the bisamide-based crosslinking agent, for example, a dibasic acid bisaziridine derivative such as isophthaloylbis (2-methylaziridine) can be used. The bisamide-based crosslinking agent is particularly preferable because it can react with the adhesive polymer having a carboxyl group at a relatively low temperature and can easily obtain a sufficient crosslinking density.

On the other hand, when the adhesive polymer has an epoxy group in the molecule, it is preferably carboxyl rosin as a crosslinking component. Carboxyl rosin has a carboxyl group in the molecule and reacts with the adhesive polymer to act to thermally crosslink the adhesive polymer. As the carboxyl rosin, gum rosin, wood rosin, tall oil rosin, or those obtained by chemically modifying them (for example, polymerized rosin) can be used. In addition, the carboxyl rosin can be used alone or as a mixture of two or more, and a rosin having substantially no carboxyl group can be used in combination as long as the effect of the present invention is not impaired.

When the crosslinking component as described above is used, the proportion of the adhesive in the entire adhesive (total mass) is usually 0.05 to 30% by mass or more, preferably 0.1 to 25% by mass. Also,
A reaction accelerator for a crosslinking component such as an epoxy resin can also be added. Thereby, the crosslinking condition by heating can be made mild. The crosslinking component is not limited to those described above, and can be selected according to the type of crosslinking functional group and crosslinking conditions.

(Production Method of Adhesive Composition) The adhesive composition of the present invention can be prepared by uniformly mixing the respective raw materials by a usual mixing operation. For example, a liquid composition can be prepared by mixing an adhesive polymer, a polyurethane, a crosslinking agent, a solvent, and the like with a mixing device such as a homomixer or a planetary mixer to uniformly dissolve or disperse each material. The polyurethane can be prepared as described above, and when polymerized in a solvent, a solution containing the polymerized polyurethane can be used as a raw material as it is.

This liquid composition is usually mixed with a first solution containing the above-mentioned adhesive polymer dissolved therein and a second solution containing the above-mentioned polyurethane dissolved therein, and the above-mentioned adhesive polymer and the above-mentioned polyurethane are mixed. It can be prepared as a precursor solution containing uniformly dissolved, and this precursor solution can be dried to form an adhesive composition comprising a dried product of the precursor solution. In this manner, a unique morphology (interconnection structure) between the polyurethane and the adhesive polymer having good compatibility with the polyurethane can be formed, and the above-described performance (non-adhesiveness at room temperature and high adhesive strength) can be obtained. , Especially effectively. When a crosslinking component is added, a third solution containing the crosslinking component is usually added to the precursor solution.

For example, the precursor solution prepared as described above can be applied on a substrate and dried to form a film adhesive (or an adhesive layer) comprising an adhesive composition. Known means such as a knife coater, a roll coater, a die coater, and a bar coater can be used as the application means. As the substrate, a liner or the like having releasability, a substrate (support) of an adhesive sheet, or the like can be used. Drying for forming the film adhesive is usually performed at a temperature of 60 to 180 ° C. The drying time is usually several tens of seconds to several minutes. The thickness of the film adhesive is usually 5 to 1,000 μ
m, preferably 10 to 500 μm, particularly preferably 15 to 1
00 μm.

When the film adhesive according to the present invention is used by bonding it to an appropriate adherend, for example, after being laminated on the adherend, 1 to 50 kg / cm ² (about 0.1 to 4. 9
Under pressure conditions in the range of (MPa), the bonding can be completed using a crimping operation. In addition, at the time of pressure bonding,
Cooling (natural cooling) can increase the initial adhesive strength. In this case, the heating conditions are not particularly limited, but the heating temperature is usually 60 to 120 ° C., and the heating time is usually 30 seconds to 5 seconds.
Minutes. The film adhesive of the present invention can also be used as an adhesive layer of an adhesive sheet.

(Easily Heat-Peelable Adhesive) The adhesive composition of the present invention is similar to the above-mentioned conventional heat-peelable adhesive composition, and comprises (I) an adhesive polymer and (II) a crystalline polymer. And a polymer. The crystalline polymer comprises the crystalline polyurethane described above. The characteristics of the adhesive composition according to a preferred embodiment of the present invention include [1] the polyurethane as the crystalline polymer, and [2] the adhesive polymer,
When heated to a temperature equal to or higher than the melting point of the polyol unit contained in the polyurethane, the polymer contains a polymer compatible with the polyurethane, and [3] the polymer compatible with the polyurethane is crosslinked. Thereby, when desired, heating to a predetermined temperature is performed to make the peeling state in which the peel strength is reduced to a value lower than the value before heating, to enhance the thermal peelability, and to maintain the peelable state. It is possible to extend the easy peeling time to a predetermined time, to be able to peel without leaving adhesive on the adherend, to enhance the cleanliness of peeling, and to reapply by peeling and pressing against the adherend. It is possible to provide an adhesive composition having heat releasability, which is capable of enhancing re-adhesiveness so as to enable adhesion.

The requirement of the above [1], that is, the inclusion of the above-mentioned specific crystalline polyurethane particularly effectively contributes to the above. The polyol unit in the polyurethane molecule easily melts when heated to a temperature equal to or higher than the melting point of the polyol unit, and the polyurethane and the adhesive polymer are compatible with each other to enhance the ease of peeling. In addition, since the polyol unit in the polyurethane molecule, that is, the polyol compound, is a non-adhesive polymer, it is possible to effectively enhance the delamination cleanliness and prevent the adhesive surface from remaining after the release.

The above requirement [2] particularly effectively contributes to the above. That is, since the tacky polymer is compatible with the molten polyol unit, it is advantageous to delay recrystallization of the polyol unit, that is, the polyurethane after heating. Further, the melting and recrystallization of such a polyol unit in the composition is a substantially reversible physical reaction (phenomenon). Thus, after heating, when re-bonding or after re-bonding, the composition returns to substantially the same phase state as before heating. Therefore, it can be re-bonded in the same manner as when it is used initially (first). Further, after re-adhesion, it can be peeled off by heating again. In addition, when the adhesive composition of the present invention contains a relatively large amount of the adhesive polymer, it can be adhered only by pressure bonding at room temperature (about 15 to 30 ° C.). In the case where the amount of the adhesive polymer is relatively small, or in the case where the adhesive polymer is adhered to an adherend that is difficult to adhere, the adhesive can be applied by thermocompression bonding. Furthermore, after heat peeling,
The operation of re-adhering to the adherend may be performed before the adhesive is cooled.

The above requirement [3] particularly effectively contributes to the above. Since the cohesive force is effectively increased by the crosslinking, the adhesive polymer is effectively prevented from remaining on the adherend during peeling. On the other hand, in the easily peelable state, the polyol unit is compatible with the crosslinked adhesive polymer. Therefore, it is possible to effectively prevent the adhesive from remaining as an adhesive without necessitating crosslinking of the polyurethane itself, which hinders the melting-recrystallization reaction of the polyol unit. From such a viewpoint, when the adhesive composition further contains a crosslinking agent (crosslinking component), it is preferable to use a crosslinking component which does not substantially react with polyurethane.

In order to obtain the effects of the present invention as described above, the content of the tacky polymer is in the range of 50 to 95% by mass based on the total mass of the composition. If the content of the adhesive polymer is less than 50% by mass, the above effects may not be particularly obtained. On the other hand, if it exceeds 95% by mass, the above effects may not be obtained. On the other hand, the content ratio of the crystalline polyurethane is in the range of 4 to 49% by mass based on the total mass of the composition. If the content of the crystalline polyurethane is less than 4% by mass, the above-mentioned effects (1) to (4) may not be obtained.
If it exceeds 9% by mass, the above-described effects may not be obtained. From these discussions, the content ratio of the adhesive polymer is preferably 52 to 94% by mass, particularly preferably 55 to 94% by mass.
９０90% by mass. The content ratio of the crystalline polyurethane is preferably 5 to 47% by mass, more preferably 9 to 4% by mass.
4% by mass.

(Method of Manufacturing Adhesive Sheet) As described above, the liquid (paint) containing the adhesive composition of the present invention is applied to the surface (or both front and back) of the substrate and dried to form an adhesive layer. Then, an adhesive sheet can be manufactured. Also, a coating containing the adhesive composition is applied to the release surface of the liner (release paper), dried to form an adhesive layer, and then the base material is pressed against the adhesive layer to produce an adhesive sheet. You can also. The drying at the time of forming the adhesive layer is usually performed at a temperature of 60 to 180 ° C., as in the case of the film adhesive described above. The drying time is usually several tens of seconds to several minutes. The thickness of the adhesive layer is usually 5 to 1,000 μm, preferably 10 to 1000 μm.
It is 500 μm, particularly preferably 15 to 100 μm.

As the substrate of the adhesive sheet, a substrate (support) conventionally used for an adhesive sheet can be used.
For example, paper, metal film, polymer film and the like can be used. As the polymer of the film, polyimide,
Synthetic polymers such as polyvinyl chloride, acrylic polymers, polyesters (such as PET), polyurethane, and polyolefin polymers (including ethylene copolymer) can be used. The thickness of the substrate is usually 5 to 500 μm.
m, preferably 10 to 300 μm.

The substrate may be one that transmits visible light or ultraviolet light, or one that reflects light. Further, it may be colored or decorated by printing or the like. In that case, the adhesive sheet contained in the adhesive layer comprising the adhesive composition of the present invention is useful as a decorative sheet or a marking film. The adhesive surface of the adhesive layer is usually protected with a liner. The liner is usually formed from a paper, a plastic film, or a film in which both are laminated.

When the adhesive sheet according to the present invention is used by bonding it to an appropriate adherend, for example, after being laminated on the adherend, 1 to 50 kg / cm ² (about 0.1 to 4.9 MPa)
Under pressure conditions in the range of a), the bonding can be completed using a pressure bonding operation. Further, at the time of pressure bonding, the adhesive strength can be increased by heating and cooling (natural cooling). Examples of the adherend include (1) metals such as aluminum, stainless steel, copper, and zinc steel sheets, (2) resins such as polyimide, acrylic resin, polyurethane, melamine resin, epoxy resin, and vinyl chloride; and (3) ceramics and glass. A surface formed from an inorganic oxide material or the like, that is, a material having an adhered surface can be used. Further, those having a painted surface as the adhered surface can also be used.

The adhesive sheet easily heat-peelable according to the present invention comprises:
An adhesive layer comprising an adhesive composition containing the adhesive polymer and the polyurethane is provided. Therefore, the stickiness at room temperature can be almost eliminated, and the slidability (ease of sliding) can be improved.
When slidability is good, positioning with respect to the adherend is particularly easy in the bonding operation. On the other hand, after positioning, it is possible to cool it by press-fitting or heat-pressing as it is and bond it. Such an easily positionable and pressure-bondable adhesive sheet has an adhesive surface having a relatively large area (usually 400 cm ² or more), such as a decorative sheet (decorative sheet) for interior or exterior, It can be suitably used as a retroreflective sheet for large road signs. Also,
Application tape (or film) because it can be adhered (adhered) to the adherend with desired peel strength and can be peeled off by heating at the desired time without adhesive residue.
It can also be used as a masking tape (or film) for manufacturing electronic components.

For example, when manufacturing a component having an electronic circuit, the adhesive sheet can be used as a masking tape for an electronic component as follows. First, the above-mentioned adhesive sheet (masking tape for electronic components) is adhered to a substrate on which a circuit is to be formed, thereby forming a sheet / substrate laminate. Next, the adhesive sheet is etched to remove a portion of the adhesive sheet corresponding to an electronic circuit pattern to be formed. At this time, it is preferable to use a substrate made of a photo-decomposable material as the base material of the adhesive sheet. In this case, a photomask having a through hole corresponding to the electronic circuit pattern is placed on the surface of the base material of the adhesive sheet, and irradiated with light from above the photomask,
The portion of the adhesive sheet corresponding to the electronic circuit pattern can be disassembled and made removable. As the light, for example, an ultraviolet laser can be used.

As described above, the portion of the adhesive sheet is removed, and an opening corresponding to the electronic circuit pattern is formed in the sheet / substrate laminate. Thus, an exposed surface of the substrate surrounded by the opening is formed. Subsequently, a conductive material for forming an electronic circuit is coated on the surface of the base material of the adhesive sheet. The coating is usually performed by a method such as vapor deposition or sputtering. After the coating, the adhesive sheet is finally peeled off by heating. Thereby, an electronic circuit having a predetermined pattern can be formed on the substrate. Further, since the adhesive sheet has the adhesive layer made of the adhesive composition of the present invention, there is no adhesive residue or the like after the sheet is peeled off, and the cleanliness of the substrate surface is not impaired.

By the way, in the case of an adhesive sheet which can be easily peeled off by heat, it is preferable that the adhesiveness between the adhesive layer and the substrate is as strong as possible. If the adhesiveness between the adhesive layer and the base material is weak, a part or the whole of the adhesive layer is left on the adhered surface when the adhesive sheet is peeled off. In order to increase the adhesion between the substrate and the adhesive layer, it is preferable to apply a primer to the surface of the substrate on which the adhesive layer is disposed.

The polymer of the film forming the base material preferably contains at least one of polyurethane and ethylene-acrylic acid copolymer. This is because these polymer films can be particularly strongly adhered to the adhesive layer made of the above-mentioned adhesive composition without using a primer. Further, conventionally known additives can be added to the adhesive layer as long as the effects of the present invention are not impaired. For example, viscosity modifiers,
Inorganic particles such as defoaming agents, leveling agents, ultraviolet absorbers, antioxidants, pigments, fungicides, elastic microspheres made of sticky polymers or non-sticky rubber-based polymers, tackifiers, crosslinkers A catalyst for accelerating the reaction.

When performing thermal peeling, the temperature is usually 60 to 120 ° C.
At this temperature, heating may be performed for 30 seconds to 5 minutes. In addition, since the adhesive composition of the present invention is used for the adhesive layer, the adhesive composition has an easy peeling time of at least 5 minutes after heating for peeling. The easy peeling state can be maintained even after the adherend and the adhesive layer are cooled to around room temperature (about 25 ° C.), but the adhesive strength (peeling strength) increases again about 15 minutes after cooling, Preferably, the re-adhesion can be completed. Iron, dryer, infrared (far infrared) to heat the adherend and / or adhesive sheet during the thermal stripping operation
A heating device such as a lamp can be used. When the base material includes a metal foil, the adhesive sheet can be heated by an electromagnetic induction heating method. Further, heating can be performed using a liquid or steam as a heat medium.

The peel strength of the adhesive sheet is a value measured at a peeling speed of 180 ° and a peeling speed of 300 mm / min before heating for peeling, and usually exceeds 10 N / 25 mm, preferably 12 to 40 N / 25 mm. And particularly preferably 13 to 35.
N / 25 mm. If the peel strength before the heat-peeling operation is too low, there is a possibility that the adhesive sheet cannot be used in the same manner as a normal adhesive sheet. Conversely, if it is too high, the peel strength during the heat-peeling operation is too high, and the ease of peeling is enhanced. May not be.
The optimum range of the peeling strength during the thermal peeling operation can be appropriately determined depending on the mechanical strength (elastic modulus, elongation at break, etc.) of the substrate and the peeling operation conditions (peeling speed). From the viewpoint of performing the peeling operation quickly, 180 ° peeling, 300 mm /
It is preferably 10 N / 25 mm or less as a value measured at a peeling rate per minute.

[0070]

EXAMPLES Next, examples of the present invention will be described. All "parts" shown below are parts by mass. 1. Preparation of Adhesive Polymers (PSA1 and PSA2) First, 16.5 parts of phenoxyethyl acrylate, 2-
3. hydroxy-3-phenoxypropyl acrylate
5 parts, 7.5 parts of butyl acrylate and 1. part of acrylic acid.
5 parts of the mixed monomer (30 parts) was mixed with 5 parts of ethyl acetate.
It was dissolved in a solvent consisting of 9.5 parts and 10.5 parts of 2-butanone to form a monomer solution. Next, 0.15 parts of azobis 2,4-dimethylvaleronitrile was added as an initiator to this monomer solution. This monomer solution is
The polymerization reaction was carried out at 45 ° C. for 2 hours and further at 65 ° C. for 3 hours under a nitrogen atmosphere to obtain an adhesive polymer solution (PSA1) having a solid content of 30%. In the same manner as above, 9.0 parts of phenoxyethyl acrylate, 4.5 parts of 2-hydroxy-3-phenoxypropyl acrylate, 15.0 parts of butyl acrylate, and 1.5 parts of acrylic acid are polymerized to give a solid content of 30%. An adhesive polymer solution (PSA2) was obtained.

2. Preparation of Polycaprolactone Polyurethane (PUR1, PUR2 and PUR3) Polycaprolactone (Placcel (registered trademark) series manufactured by Daicel Chemical Industries, Ltd.) and isophorone diisocyanate (IPDI) were mixed at the compounding ratio shown in Table 1. And polymerized in a toluene solvent. In the polymerization operation, first, 0.5% by mass of dibutyltin dilaurate (catalyst) based on polycaprolactone was added to the toluene solution, and the solution was heated at 80 ° C. for 5 hours under a nitrogen atmosphere. Thereafter, 10% by mass of n-propyl alcohol based on polycaprolactone was added to the above solution, and the mixture was further heated at 80 ° C. for 1 hour to complete the polymerization.
UR2 and PUR3 were obtained.

[0072]

[Table 1]

[0073] 3. Preparation of Adhesive Composition Solution (Examples 1 to 3)
8, Comparative Examples 1 and 2) The mixing ratios of the adhesive polymer solution and the polyurethane solution obtained as described above, respectively, as shown in Table 2 or Table 3 (the amounts in the tables indicate parts by mass of nonvolatile components). ), And isophthaloylbis (2-methylaziridine) is added as a cross-linking agent to the mixed solution, and the adhesive composition solution of each example (hereinafter, may be referred to as “adhesive solution”). Obtained. The amount of the crosslinking agent is determined by the solid content (non-volatile content) of the adhesive composition.
Was 0.2% by mass. Also, the adhesive solution was transparent.

The adhesive solutions of Comparative Examples 1 and 2 were obtained in the same manner as in Example 1 except that a commercially available polycaprolactone was used instead of the polyurethane. In addition, the compounding ratio is similarly shown in Table 2 or Table 3, respectively. The polycaprolactone used here was a crystalline polycaprolactone manufactured by Daicel Chemical Industries, Ltd., “Placcel ™ H4 (Mw = 76,000)” (Comparative Example 1),
"Placcel (trademark) H1P (Mw = 25,000
0) "(Comparative Example 2).

[0075] 4. Measurement of Crystallinity (ΔH cal / g) The adhesive solution of each example shown in Table 2 was dried in an oven at 100 ° C. for 30 minutes to produce an adhesive composed of nonvolatile components.
Using this adhesive as a test body, the crystallinity was measured as follows. First, the test specimen of each example was heated in an oven at 100 ° C. for 20 minutes to melt the crystalline component contained in the adhesive. Then, the specimen taken out of the oven was
The sample was left for 1, 3, 24, 72 and 168 hours at a temperature of ° C., respectively, and the crystallinity (ΔH cal / g) and the peak temperature (melting point) of endothermic due to melting of the crystal were measured by differential scanning calorimeter (DSC). did. Table 2 shows the results.

The adhesive using the polycaprolactone of Comparative Example 1 was almost completely recrystallized after 1 hour, whereas the adhesives of Examples 1 to 5 had a long time (1
Over time) recrystallization could be delayed. Example 5
With the adhesive of Example 1, recrystallization of the polyurethane did not occur even after one week, and it took more than one week to recrystallize. In addition, it was confirmed that the polyurethane (PUR2) itself used in Example 5 recrystallized in about one hour.

[0077] 5. Measurement of Thermally Active Adhesion (Heat Adhesion) The adhesive solution of each example shown in Table 2 was applied to a 25 μm-thick PE.
The composition was applied on a substrate made of a T film and dried in an oven at 100 ° C. for 30 minutes to form an adhesive layer having a thickness of 30 μm on the substrate. Thereby, the adhesive sheet of each example was obtained. Using these adhesive sheets as test pieces, the heat-activated adhesive strength was measured as follows. Each test piece was placed on a stainless steel plate (SUS304) as an adherend,
After reciprocating the 2 kg roller once, it was heated in an oven at 100 ° C. for 20 minutes to thermally activate the adhesive and thermally bond the test piece and the adherend. In each example, six test pieces were prepared, and all of the test pieces were bonded to the adherend in the same manner. After heat bonding as described above, each specimen was taken out of the oven, and each was 5 minutes, 1 hour, 3 hours, 2 hours.
After leaving at a temperature of 25 ° C. for 4 hours, 72 hours and 168 hours, the 180 ° peeling force (adhesive force) was 300 mm /
It was measured at a peel rate of 1 minute. Table 2 shows the results. The unit of the peeling force was N / 25 mm. In addition, in order to examine the correlation between the crystallinity and the adhesive force (180 ° peel force after thermal activation), the adhesive force after 5 minutes was set to 1.0, and the increase rate of the adhesive force after each standing time (Table 1). 2 in []) was calculated and also shown in Table 2.

In the adhesive according to the present invention, the adhesive strength increases due to the recrystallization of the polyurethane, and the adhesive strength reaches a maximum when the crystallization is completed. When polycaprolactone was used instead of polyurethane (Comparative Example 1), crystallization was almost completed after 1 hour, and the adhesive strength reached a maximum. However, in the adhesive of the example, the recrystallization speed is appropriately controlled, and the adhesive strength at a level that is easy to peel off is maintained even after 1 hour. That is, when the adhesive composition of the present invention is used as a heat-activated adhesive, the open time can be lengthened, and repositioning (peeling, re-adhesion) can be performed after bonding. Examples 2, 3 and 4 are examples in which a polyurethane PUR1 using medium-molecular-weight polycaprolactone as a raw material and a polyurethane PUR2 using low-molecular-weight polycaprolactone as a raw material are mixed and used. In these examples, even after 3 hours, a low adhesive strength at a level that facilitates peeling is maintained. On the other hand, in Example 5 using polyurethane consisting only of PUR2, recrystallization progressed very slowly, and recrystallization was not completed even after one week. (Light peeling force). Therefore, this adhesive can be used as a light-peelable adhesive.

[0079] 6. Measurement of pressure-sensitive adhesive force (pressure-bonding adhesive force) The adhesive sheet of each example was prepared in the same manner as in the case of the above-mentioned heat-active adhesive force, and left at about 25 ° C. for one week to sufficiently promote crystallization of the crystal component. After that, these were used as test pieces. Each test piece was placed on an adherend (SUS304) at 25 ° C for 2 kg.
Crimping was performed by one reciprocation of a roller. After pressure bonding, leave at 25 ° C for 2 hours, and then peel 180 degrees (adhesion)
Was measured at a peel rate of 300 mm / min. Table 2 shows the results
Shown in The unit of the peeling force was N / 25 mm.
The higher the surface tack and adhesion at room temperature (about 25 ° C),
Pressure-sensitive adhesive strength tends to show a high value. In Comparative Example 1 using polycaprolactone, the surface tack was low and the tackiness was low because the crystallinity was relatively high. On the other hand, Example 1
In the adhesives of Nos. To 5, polycaprolactone was made into polyurethane to appropriately control the degree of crystallinity, so that surface tack and tackiness could be improved.

[0080]

[Table 2]

[0081] 7. Evaluation of Thermal Peel Adhesive Force (Easy Thermal Peel) Adhesive sheets of the respective examples were prepared in the same manner as in the case of the pressure-sensitive adhesive force described above, and left at about 25 ° C. for one week, and these were used as test pieces. Each test piece was placed on the adherend (SUS304) by 2
Crimping was performed at 5 ° C. by one reciprocation of a 2 kg roller. After crimping, it was left in an oven at 65 ° C./95% RH for 24 hours, and further left in an oven at 25 ° C./50% RH for 24 hours to complete the bonding. , And 300 mm / min. This peeling force was defined as the initial adhesive force.

The test piece produced in the same manner as described above, adhered to the adherend, and completed the adhesion was further heated in an oven at 100 ° C. for 20 minutes, and then heated at 25 ° C. for 5, 10 , 15, 60 and 180 minutes, the 180-degree peeling force (adhesive force) was measured at a peeling speed of 300 mm / min. This peeling force was defined as a heat peeling adhesive force.
Also. For each thermal peel adhesion, the initial adhesion is 1
The reduction rate when it was set to 00% was calculated. Table 3 shows the results. The unit of the peeling force was N / 25 mm.

After the adhesion was completed, the crystallized polycaprolactone portion was melted, whereby the adhesive force (peeling force) was reduced, and the adherend could be easily peeled while keeping it clean. On the other hand, the adhesion increased as recrystallization progressed. In Comparative Example 2 using polycaprolactone, crystallization was almost completed after 1 hour (60 minutes), the adhesive strength increased, and peeling became difficult. However, in Examples 6 and 7 using a polymer in which polycaprolactone was converted to polyurethane, it was possible to control the recrystallization rate to be moderately slow. Therefore, even after 1 hour, the ease of peeling could be maintained, and the adherend could be easily peeled while keeping it clean. On the other hand, in Example 8 containing PUR3 in which polycaprolactone with Mw = 3,800 was made into polyurethane, recrystallization was not completed even after 3 hours (180 minutes), and the peelability was maintained.

[0084]

[Table 3]

(Example 9 and Comparative Example 3) The composition of the adhesive layer (adhesive composition) was changed to that described below, the substrate was changed to a polyurethane film (thickness = 33 μm), and the method described below was used. The adhesive sheet of Example 9 was obtained in the same manner as in Example 1 except that the adhesive sheet was manufactured.

Composition of adhesive layer Crystalline polyurethane: crystalline polycaprolactone “Placcel (registered trademark) 24” manufactured by Daicel Chemical Industries, supra.
0 "(Mw = 11,000, Mw / Mn = 1.9)
Crystalline polyurethane (Mw = 74,000, Mw / Mn) made into a polyurethane in the same manner as described above using IPDI.
= 2.3). Adhesive polymer: PSA2 as described above Crystalline polyurethane: adhesive polymer = 30: 70 (mass ratio of non-volatile components) The same crosslinking agent as in Example 1 was used in the same amount.

Method for Producing Adhesive Sheet An adhesive layer was formed in the same manner as in Example 1 except that the adhesive composition solution was applied on the release surface of the siliconized liner and dried, and then the adhesive layer and the substrate were Was pressed to produce an adhesive sheet. On the other hand, in the composition of the adhesive layer, the above-mentioned polycaprolactone was replaced with “Placcel (trademark) 220N (M
(w = 3,800, Mw / Mn = 1.3, melting point: 50 ° C.) except that the adhesive sheet of Comparative Example 3 was obtained in the same manner as in Example 9.

The following items were evaluated for the adhesive sheets of Example 9 and Comparative Example 3 as described below. Table 4 shows the evaluation results. Evaluation method Peeling force retention: A test piece was adhered to a melamine baked painted plate manufactured by NTP Co., Ltd. as an adherend in an environment of 20 ° C. Pasting operation is JIS Z 0237 8.2.3
The test piece and the adherend were crimped in accordance with the above. 4 at the same temperature
After standing for 8 hours, the 180-degree peel strength was measured with Tensilon. This was defined as the initial peel strength (In). On the other hand, the test piece adhered to the adherend in the same manner as above was heated to about 100 ° C. with an industrial drier, left at room temperature (about 25 ° C.) for 5 minutes, and immediately after cooling, the peel test was performed in the same manner as above. And the peel strength was taken as the thermal peel strength (P). The calculation of the peeling force retention was performed according to the following equation. (Peeling force retention) = (P / In) × 100 [%] Further, a test piece adhered to an adherend in the same manner as above was used.
After heating to about 100 ° C. with an industrial drier, leaving it at room temperature (about 25 ° C.) for 15 minutes and cooling, a peeling test was performed in the same manner as above, and the peel strength was taken as the recovery peel strength. The unit of the peeling force was N / 25 mm.

Adhesive residue: The surface of the adherend after the above-mentioned peeling test was observed, and it was judged OK if no adhesive (polymer component of the adhesive) remained, and NG if there was a slight adhesive residue. Peel residue: Observe the adherend surface after the above peel test,
If a residue (stain) was observed on the surface of the adherend other than the glue, it was judged as NG, and if the surface was clean, it was judged as OK.

Evaluation Results In Example 9, the adhesive strength after heating was reduced to 45%.
Excellent heat peelability. In addition, the peeling cleanability was high, and there was no adhesive residue and residue contamination after peeling. on the other hand,
Comparative Example 3 was excellent in thermal peelability, but residue contamination was observed on the adherend surface. The residue contained low molecular weight components contained in the polycaprolactone used.

Example 10 PSA 1 was prepared by using a mixed monomer having the following composition as the adhesive polymer of the adhesive layer.
The adhesive sheet of this example was obtained in the same manner as in Example 9, except that the polymer obtained in the same manner as in the preparation of was used.
The composition of the mixed monomer (mass ratio of the raw material monomers) used here was 2-ethylhexyl acrylate: butyl acrylate: methyl acrylate: acrylic acid = 33.
8: 49.7: 10: 6.5. In this example, the adhesive sheet was pressed at room temperature (approximately 25 ° C.) onto a melamine plate as an adherend, heated at 85 ° C. for 1 minute to thermally activate and adhered, and then left at room temperature for 24 hours, followed by initial peeling. The strength was measured. On the other hand, in the same manner as described above, heat activation was carried out to adhere, and in the same manner as in Example 9, the film was heated with a drier, left standing at room temperature (about 25 ° C.) for 1 minute, and immediately after cooling, the thermal peel strength was measured. . Table 4 shows the results of these peeling tests. Table 4 also shows the results of the evaluation of peel cleanliness (adhesive residue and residue) in the same manner as in Example 9.

Example 11 An adhesive sheet of this example was obtained in the same manner as in Example 10, except that the adhesive sheet was manufactured as follows. In this example, after the adhesive layer on the silicon-treated liner and the base material were pressed, a heat treatment was further performed at 85 ° C. for 1 minute, and then curing was performed at room temperature for 1 hour to complete the adhesive sheet. The adhesive sheet of this example was pressed against the above-mentioned melamine plate at room temperature, left at room temperature for 24 hours, and the initial adhesive strength was measured. Also, after being pressed on a melamine plate, the mixture was heated with a dryer in the same manner as described above, and was kept at room temperature (about 25 minutes) for 1 minute.
C) and immediately after cooling, the thermal peel strength was measured.
Table 4 shows the results of these peeling tests. Example 9
Table 4 also shows the results of evaluating the delamination cleanliness (adhesive residue and residue) in the same manner as described above.

Example 12 Example 9 was repeated except that the composition of the adhesive layer (adhesive composition) was changed as described below.
The adhesive sheet of this example was obtained in the same manner as in Example 1. Composition of Adhesive Layer Crystalline polyurethane: “U845” manufactured by Dainichi Seika (synthesized from starting materials containing adipic ester polyol and aliphatic diisocyanate). The polyurethane had a number average molecular weight of 61,000 and a weight average molecular weight of 120,000. Adhesive polymer: PSA2 described above. Crystalline polyurethane: adhesive polymer = 20: 80 (mass ratio of non-volatile components) The same crosslinking agent as in Example 1 was used in the same amount. Table 4 shows the results of the peel test and the evaluation of the peel cleanliness in the same manner as in Example 9.

[0094]

[Table 4]

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09J 201/02 C09J 201/02 (72) Inventor Hidetoshi Abe 5500 Wakagi Oji, Higashine-shi, Yamagata Pref. Intra-company F-term (reference) 4J004 AA05 AA08 AA10 AA14 CA04 CA05 CA06 CB03 CC02 EA06 FA05 FA08 4J034 BA03 CA02 CA04 CB03 CB07 CC03 DA01 DB03 DB07 DF01 DF02 DF12 DG06 HA01 HA07 HC03 HC06 HC08 HC12 HC22 HC32 HC35 HC73 HC46 KC17 KD02 KE02 RA08 4J040 CA072 CA082 DF002 EF002 EF111 EF121 EF131 EF281 EF331 EK032 JA02 JA12 JB09 KA26 LA01 LA02 LA06 MA10 MB03 MB05 NA19 NA20 PA30 PA33

Claims (6)

[Claims] 1. An adhesive composition comprising a crystalline polymer and a sticky polymer, wherein the sticky polymer is cross-linked, and the crystalline polymer is a polyurethane having a crystalline polyol unit in a molecule. An adhesive composition, characterized in that: 2. The adhesive composition according to claim 1, wherein the crystalline polyol unit is formed from polycaprolactone. 3. The adhesive composition according to claim 1, wherein the adhesive polymer is compatible with the polyurethane at a temperature higher than the melting point of the crystalline polyol unit. 4. The adhesive polymer according to claim 1, wherein (a)
The adhesive composition according to claim 1 or 3, wherein the adhesive composition is a polymer having a hydroxyl group, (b) a phenyl group, and (c) a crosslinking functional group capable of reacting with a crosslinking agent. 5. A polyurethane composition used for producing the adhesive composition according to claim 1, comprising a polyurethane obtained by polymerizing a starting material consisting essentially of polycaprolactone and diisocyanate. A polyurethane composition, characterized by comprising: 6. An adhesive sheet comprising a substrate and an adhesive layer comprising the adhesive composition according to claim 1 fixedly disposed on at least one surface of the substrate.