JPH09316424A - Polyurethane resin adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject adhesive comprising a polyurethane resin having metal sulfonate salt groups in the molecule, high in initial adhesivity and excellent in the heat resistance, cold resistance and long period storage stability of the adhesivity and useful for tapes, etc. SOLUTION: This polyurethane adhesive comprises a polyurethane resin obtained by reacting (A) an active hydrogen compound containing a polyol having one or more 1-10C hydrocarbon group side chains with (B) an organic polyisocyanate. The polyurethane resin preferably has metal sulfonate salt groups in the molecule in an amount of 0.001-1.0mmol/g in the molecule. The resin is preferably crosslinked with a polyisocyanate curing agent. The polyol in the component A preferably comprises a polyesterdiol which is obtained by reacting a dicarboxylic acid or its derivative with a diol having one or more 1-10C hydrocarbon group side chains and which has the metal sulfonate salt groups.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an adhesive tape,
The present invention relates to a pressure-sensitive adhesive used for various pressure-sensitive adhesive products such as labels and sheets, and particularly to a polyurethane resin pressure-sensitive adhesive having excellent heat resistance and cold resistance.

[0002]

2. Description of the Related Art When a polyurethane resin is used as a pressure-sensitive adhesive, it has excellent flexibility and processability, but generally has a strong cohesive force, so the initial pressure-sensitive adhesive force is low and the pressure-sensitive adhesive properties deteriorate with temperature changes. Or, there was a problem with the adhesive properties such as unstable adhesive properties under long-term storage. Therefore, it has been difficult to spread the polyurethane resin on the adhesive layer of a tape, label, sheet or the like having adhesive on both sides or one side. In order to eliminate such drawbacks, for example, it is known that a small amount of polyisocyanate is mixed with a polyol to form a low-molecular weight polymer. It was difficult to obtain stable performances such as variation in adhesive properties due to the influence of, and low mechanical density of the resin at high temperature due to low cross-linking density and easy peeling from the adherend. Further, in order to improve these, a polyisocyanate curing agent is used in combination with the polyurethane resin to cure it, and the heat resistance is increased. However, in this case, there is a problem that the adhesive physical properties are deteriorated. In order to improve this point, it is also known to positively generate a urea bond by contacting with water before reacting a hydroxyl group with an isocyanate group, but this method results in excessive formation of a urea bond. However, the pressure-sensitive adhesive properties cannot be balanced, and the initial adhesive strength tends to decrease.

Generally, polyurethane resin adhesives include, as tackifiers, alkylphenol resins, terpenephenol resins, xyleneformaldehyde resins, rosins,
Those having a polar group such as —CH ₂ OH, —OH, and —COOH group such as hydrogenated rosin are used together. When such a tackifier is used, the polar group in the molecule is a curing agent. React with the isocyanate group of, especially when using a phenolic resin such as an alkylphenol resin and a terpene phenol resin, a phenolic hydroxyl group in the molecule is bonded to the isocyanate group of the curing agent to form a phenol type blocked isocyanate, and then Since it is gradually dissociated into isocyanate groups, the structure and physical properties of the pressure-sensitive adhesive layer are changed, and the performance of the pressure-sensitive adhesive layer is deteriorated over time.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned drawbacks and has a high initial adhesive strength, is capable of stably holding the adhesive strength for a long period of time, and is excellent in heat resistance and cold resistance of the adhesive strength. Another object of the present invention is to provide a polyurethane resin adhesive.

[0005]

Means for Solving the Problems As a result of intensive studies made by the present inventors for the purpose of solving these problems,
The present invention has been completed. That is, the present invention has a carbon number of 1
In the pressure-sensitive adhesive comprising a polyurethane resin obtained by reacting an active hydrogen compound containing a polyol having 10 to 10 hydrocarbon group side chains with an organic polyisocyanate, the polyurethane resin is a metal sulfonate metal in the molecule. 0.001-1.0 mmol / base / polymer
The above-mentioned pressure-sensitive adhesive is a polyurethane resin having g.

In the present invention, a polyurethane resin obtained by reacting an active hydrogen compound containing a polyol having one or more hydrocarbon group side chains having 1 to 10 carbon atoms with an organic polyisocyanate is a polyisocyanate curing agent. In the pressure-sensitive adhesive obtained by crosslinking, the polyurethane resin contains a metal sulfonate group in the molecule in an amount of 0.001 per polymer.
The above-mentioned pressure-sensitive adhesive is a polyurethane-based resin having ˜1.0 mmol / g.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION First, in the pressure-sensitive adhesive of the present invention,
The active hydrogen compound used for producing the polyurethane resin will be described. This active hydrogen compound is a polyol having a main chain hydrocarbon group in which two or more hydroxyl groups are directly bonded, preferably an alkylene group, and a hydrocarbon group having 1 to 10 carbon atoms as side chains, preferably one or more alkyl groups. Is contained as the whole or a part of it, but it is preferable to consist of only this polyol. As such a polyol,
1,2-propanediol, 1,2-butanediol,
1,3-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 2-ethyl-
1,3-hexanediol, 3-methyl-1,5-pentanediol, 2-methyl-4,4-dimethylhexanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-methyl -1,5-heptanediol, 2
-Methyl-1,8-octanediol and other diols themselves or, preferably, these diols or mixtures of these diols with other diols, adipic acid, sebacic acid, 3-methyl-1,4- A polyester diol obtained by reacting a dicarboxylic acid such as adipic acid, phenylsuccinic acid, 2,2-dimethylsuccinic acid, and allylmalonic acid, its ester, a derivative such as an acid anhydride, or δ-valerolactone, or particularly preferably In place of or as a part of these dicarboxylic acids or their derivatives, 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, 2-sodium sulfoterephthalic acid, 2-potassium sulfoterephthalic acid, 5-sodium. Sulfobis (β-hydroxylethyl) isophthalate, 5-sodium The polyester diol containing a metal sulfonate group obtained by using sulfodimethylisophthalate or the like can be exemplified. The diol or polyester diol containing no metal sulfonate group is preferably used as a mixture with the above metal sulfonate group-containing polyester diol.

The polyol having at least one hydrocarbon group side chain having 1 to 10 carbon atoms used in the present invention preferably has a number average molecular weight of 500 to 5,000. If the number average molecular weight is less than 500, the urethane bond concentration will be high and the solubility in a solvent will decrease, which is not preferable. On the other hand, when the number average molecular weight exceeds 5,000, the urethane bond concentration decreases, which is not preferable because the toughness and heat resistance of the polyurethane resin decrease.

As a part of the active hydrogen compound, polyester polyols, polyether polyols, polycarbonate polyols, etc. other than the above polyester diols can be used if necessary, and these contain a sulfonate metal base in the molecule. It may be one.
Examples of the polyester polyol other than the polyester diol include dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, azelaic acid, dimer acid, terephthalic acid, isophthalic acid, hexahydroterephthalic acid, and hexahydroisophthalic acid, and these acids. Ester or acid anhydride with ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,9-nonane Diol, diethylene glycol, dimer acid diol, trimethylolpropane, glycerin, hexanetriol, quadrol or a polyol such as bisphenol A ethylene oxide or propylene oxide adduct, or hexamethylene diamine, Cyclohexylene diamine, isophorone diamine, monoethanolamine, diamines such isopropanol triamine, obtained by dehydration condensation reaction of triamine or amino alcohol alone, or a mixture thereof,
Examples thereof include polyester polyols and polyester amide polyols. Further, polyester polyols such as lactone-based polyester polyols obtained by ring-opening polymerization of cyclic ester (lactone) monomers such as ε-caprolactone and alkyl-substituted ε-caprolactone can be mentioned. Examples of the polyether polyol include, for example, polyethylene glycol obtained by ring-opening polymerization of ethylene oxide, propylene oxide, tetrahydrofuran and the like,
Examples thereof include polypropylene glycol, polytetramethylene ether glycol, and polyether glycol obtained by copolymerizing these. Examples of the polycarbonate polyol include those obtained by dealcoholation reaction of polyhydric alcohol with diethylene carbonate, dimethyl carbonate, diethyl carbonate, diphenyl carbonate and the like. Examples of the polyhydric alcohol include ethylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and 1,8-octane. Examples thereof include diol, 1,9-nonanediol, diethylene glycol and the like. Carbon number 1
The amount of these polyols that can be used in combination with the polyol having one or more hydrocarbon-based side chains of 10 to 10 retains properties such as heat resistance of adhesive strength, cold resistance, and long-term storage stability, which are features of the present invention. The content of the active hydrogen compound is limited to less than 50% by weight, and particularly preferably less than 30% by weight, though it depends on the properties of the polyol.

If necessary, a chain extender may be used as a part of the active hydrogen compound, which may contain a metal sulfonate group in the molecule.
The chain extender is generally a compound having a molecular weight of 300 or less and having two or more active hydrogen groups in the molecule. In particular,
Ethylene glycol, 1,3-propylene glycol,
1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,8-octanediol, 1,9-nonanediol, diethylene glycol,
Dimer acid diol, trimethylolpropane, glycerin, hexanetriol, quadrol or polyol such as bisphenol A ethylene oxide or propylene oxide adduct, or hexamethylenediamine, xylenediamine, isophoronediamine, methylenebis (orthochloroaniline), monoethanol. Examples thereof include diamines such as amines and amino alcohols, and water and urea can also be used. Any of these compounds may be used alone or as a mixture of two or more thereof.

The total number of moles of the chain extender used is not more than the total number of moles of the active hydrogen compound other than the chain extender, especially 1
/ 2 or less is preferable. If the total number of moles of the chain extender exceeds the total number of moles of active hydrogen compounds other than the chain extender, the amount of urethane bonds with strong cohesive force will increase, and tough mechanical strength will be obtained, but the adhesive strength will increase. Will decrease.

As the organic polyisocyanate used in the present invention, all those which can be generally used for the production of polyurethane resin can be used.
Aromatic diisocyanates such as 4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate, or tetramethylene diisocyanate , Hexamethylene diisocyanate, aliphatic diisocyanates such as lysine diisocyanate, or alicyclic diisocyanates such as isophorone diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and organic diisocyanates such as a mixture thereof. Although preferred, a modified polyisocyanate obtained by urethane-forming, uretdione-forming, or carbodiimidating a part of these can also be used.

The NCO / OH molar ratio between the active hydrogen compound and the organic polyisocyanate is preferably 0.5 / 1.00 to 1.00 / 1.00 in order to avoid gelation in the reaction. Usually, polybutylene adipate (polyol), polyhexamethylene adipate (polyol), which is used as a polyol component of a binder in the adhesive field,
Polyester polyols such as polycaprolactone polyols have melting points above room temperature, and polyurethane resins using them have crystallinity due to folding of the methylene chain of the raw material polyester polyol, although there are differences depending on the chemical structure. When these polyurethane resins are used as adhesives, the crystallinity is strong and the adhesive properties are reduced due to crystal shrinkage when left in a low temperature environment, resulting in peeling from the adherend and the adhesive properties due to crystalline melting at high temperatures. There may be troubles such as. However, since the pressure-sensitive adhesive of the present invention is composed of a specific amount of a metal-sulfonate-containing polyurethane resin using a polyol having one or more hydrocarbon group side chains having 1 to 10 carbon atoms, it has almost no crystallinity. It does not show heat resistance and cold resistance of the adhesive strength, and an adhesive with excellent stability of the adhesive strength after long-term storage is obtained.Furthermore, the solubility in a solvent is good, and the solution has a low viscosity. , The amount of solvent used can be reduced, and the drying process time can be shortened and rationalized. As the non-crystalline polyurethane resin, there have been diethylene adipate-based, polypropylene adipate-based polyurethane resins, etc., but all of them have poor heat resistance and their adhesive strength is reduced in an environment involving temperature change, especially at high temperature. Therefore, it cannot be practically used as an adhesive. The polyurethane resin in the present invention has a metal sulfonate group of 0.001 to 1.0 per polymer.
Contains mmol / g. If the metal sulfonate group per polymer is less than 0.001 mmol / g, not only the adhesive strength will decrease with temperature change, but also stable adhesive properties cannot be obtained under long-term storage. Further, the metal sulfonate group per polymer is 1.0 mmol /
If it exceeds g, the polyurethane resin will lack solvent solubility. A preferred sulfonate group is the alkali metal base of sulfonic acid. Examples of the alkali metal include Li, Na and Ka.

The number average molecular weight of the polyurethane resin used in the pressure-sensitive adhesive of the present invention is preferably 5,000 or more. If the number average molecular weight is less than 5,000, the number average molecular weight is too small unless a polyisocyanate curing agent is used in combination, resulting in poor film forming performance. Generally, when the polyurethane resin used for the pressure-sensitive adhesive has a high molecular weight, the solution viscosity of the polyurethane resin solution becomes high and the handling property becomes poor. In order to improve the durability and heat resistance of the polyurethane resin, a high molecular weight is desirable, and it is generally contrary to the handling property. However, the polyurethane resin in the present invention has a high molecular weight,
It is a low viscosity solution with good solubility in solvents.

For producing the polyurethane resin in the present invention, a usual method such as a bulk polymerization (solid reaction) method of reacting in a molten state, a solution polymerization method, or the like can be used. As the solvent used in the solution polymerization method, specifically,
Ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, ether solvents such as dioxane and tetrahydrofuran, glycol ether solvents such as cellosolve and carbitol, glycol acetate such as cellosolve acetate. Ether solvent, dimethylacetamide,
Examples thereof include amide solvents such as dimethylformamide, aromatic hydrocarbon solvents such as toluene and xylene, alcohol solvents such as methanol, ethanol and isopropanol, and mixed solvents thereof.

When producing the polyurethane resin in the present invention, a catalyst, an additive and the like can be used if necessary. Examples of the catalyst include triethylamine,
Examples thereof include nitrogen-containing compounds such as triethylenediamine, and organic metal compounds such as dibutyltin dilaurate, tin octylate and tin stearate. Examples of the additives include ultraviolet absorbers such as substituted benzotriazoles, antioxidants such as phenol derivatives, and hydrolysis inhibitors.

When a polyisocyanate curing agent is used in combination with the above polyurethane resin, a cross-linking bond is formed, and a pressure-sensitive adhesive having excellent heat resistance and durability can be obtained.
As the polyisocyanate used as the curing agent, the above-mentioned organic polyisocyanates can also be used, but polyol adducts of isocyanates obtained by the reaction of these with a bifunctional or higher functional polyol are preferable, and also polymeric polyisocyanates and isocyanurates. Modified products and carbodiimide modified products are also preferable. Specifically, Nippon Polyurethane Industry's Coronate L, Coronate 3041, Coronate 2030, Coronate 203
1, Coronate HL, Coronate HX, Millionate M
TL, Millionate MR, etc. are mentioned. The amount used is 4 with respect to 100 parts by weight of the polyurethane resin.
It is preferably 0 parts by weight or less (both in terms of solid content).

The polyurethane resin in the pressure-sensitive adhesive of the present invention may contain other resins and additives in addition to the above components. For example, an alkylphenol resin, a terpene phenol resin, a xylene formaldehyde resin, a rosin, a hydrogenated rosin or the like having a polar group such as —CH ₂ OH, —OH and —COOH groups can be used together.

Further, the polyurethane resin in the present invention can also be used as a binder for magnetic recording media, a binder for film laminating, an ink binder, a surface treatment agent for plastics, other adhesives and coating agents.

[0020]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not construed as being limited to the examples. Parts in the following Synthesis Examples, Examples, and Comparative Examples,%
In principle, indicates parts by weight and% by weight, respectively.

[Production of Polyester Diol] Synthetic Examples 1 to 8 In a reactor equipped with a thermometer, a stirrer and a partial reflux condenser, 2 parts of dimethyl 5-sodium sulfoisophthalate,
2-butyl-2-ethyl-1,3-propanediol 7
After adding 24 parts, a transesterification reaction was carried out at 140 to 220 ° C. for 5 hours. Then add 266 parts of adipic acid and add 20
After reacting at 0 to 220 ° C for 10 hours, the reaction system is depressurized to 20 mmHg over 3 hours, and further 5 to 20 mmH.
Polycondensation reaction was carried out at 210 ° C. for 2 hours. The obtained polyester diol (A) had an average number of hydroxyl groups per molecule of 2.0, a hydroxyl value of 224, and a number average molecular weight of 500.

By the same manufacturing method, polyester diols (B) to (H) composed of the dicarboxylic acid component and the diol component shown in Tables 1 and 2 were obtained.

[0023]

[Table 1]

[0024]

[Table 2]

[Production of Polyurethane Resin] Synthesis Examples 9 to 16 In a reaction vessel equipped with a thermometer, a stirrer, and a cooling tube, MEK was made to be 70% of solid content based on polyester diol shown in Tables 1 and 2. In addition, 0.02% of dibutyltin dilaurate as a urethanization catalyst was added to the solid content and mixed at 40 ° C., then organic diisocyanate was added and reacted at 80 ° C. The reaction generated heat and the internal temperature became about 80 ° C., and the viscosity also increased with time. MEK was added at appropriate times and the mixture was diluted and kept at 80 ° C. for reaction for 7 hours to obtain a uniform transparent liquid. Final solid content is 40
%Met. These polyurethane resin solutions (I)
The constituent raw materials of (VIII), their ratios, and characteristic values are summarized in Tables 3 and 4. NCO / OH in the table indicates the molar ratio of the hydroxyl group of the polyester diol and the isocyanate group of the organic diisocyanate. The number average molecular weight of the polyurethane resin was determined by gel permeation chromatography using a polystyrene calibration curve.

[0026]

[Table 3]

[0027]

[Table 4]

[Evaluation] Examples 1 to 9, Comparative Examples 1 to 8 (1) 100 parts of the polyurethane resin solution (I) and 10 parts of polyisocyanate (Coronate L; manufactured by Nippon Polyurethane Industry Co., Ltd.) (each in terms of solid content) were added. After uniformly mixing, the mixture was defoamed and coated on a PET film (thickness 0.1 mm) using a knife coater so that the dry film thickness was 100 μm. Then, after curing and drying at 60 ° C. for 30 minutes and further at 120 ° C. for 60 minutes, the surface of the coating film was covered with a release paper to obtain a sample of Example 1 for evaluation of adhesive properties. (2) The polyurethane resin solution (II) was dried on a PET film (thickness 0.1 mm) using a knife coater to give a dry film thickness of 1
It was applied so as to have a thickness of 00 μ. Then, after curing and drying at 60 ° C. for 30 minutes and further at 120 ° C. for 60 minutes, the surface of the coating film was covered with a release paper to obtain a sample of Example 2 for evaluation of adhesive properties. (3) 100 parts of polyurethane resin solution (VII) and 40 parts of terpene phenol resin (each calculated as solid content) were uniformly mixed and then defoamed to obtain a PET film (thickness 0.1 m).
m) was coated on the m) using a knife coater so that the dry film thickness was 100 μm. Then 120 at 60 ° C for another 30 minutes
After curing and drying at 60 ° C. for 60 minutes, the surface of the coating film was covered with a release paper to obtain a sample of Comparative Example 5 for evaluation of adhesive physical properties. (4) 100 parts of polyurethane resin solution (VII), 40 parts of terpene phenol resin, and 10 parts of polyisocyanate (Coronate L; manufactured by Nippon Polyurethane Industry Co., Ltd.) (each calculated as solid content) are uniformly mixed and then defoamed to obtain a PET film. (Thickness 0.1 mm) Dry film thickness 1 using knife coater
It was applied so as to have a thickness of 00 μ. Then, after curing and drying at 60 ° C. for 30 minutes and further at 120 ° C. for 60 minutes, the surface of the coating film was covered with release paper to obtain a sample of Comparative Example 6 for evaluation of adhesive physical properties. Similarly, each sample for evaluation of adhesive properties was obtained using the polyurethane resin solutions shown in Tables 5 to 8. The adhesive property of the polyurethane resin adhesive (sample) thus obtained was measured and evaluated as follows. Tables 5 to 8 show the constituent raw materials of the polyurethane resin pressure-sensitive adhesive and the measurement and evaluation results of the pressure-sensitive adhesive properties. (A) Long-term storability of adhesive strength The initial adhesive strength of each of the above samples and each sample at -10 ° C and 25
After storing for 3 weeks or 3 months under each condition of 95 ° C RH at 95 ° C or 95% RH at 50 ° C, return to room temperature, peel off the release paper, and measure the adhesive strength (aging) of the coating film surface with a Probutac tester. did. The results of these measurements are shown as the ratio of the time-dependent adhesive force to the initial adhesive force, that is, the adhesive force decrease rate, according to the following evaluation criteria. Evaluation criteria ◎: Adhesive force decrease rate 5% or less ○: Adhesive force decrease rate 5 to 10% △: Adhesive force decrease rate 10 to 20% ×: Adhesive force decrease rate 20% or more (b) Cold resistance of adhesive force, heat resistance The release paper of each of the above samples was peeled off, attached to the side surface of a vinyl chloride pipe having a diameter of 20 cm, and stored for 3 months at -10 ° C or 50 ° C, and then the appearance was visually observed. Evaluation criteria ○: No change in appearance Δ: Partial peeling ×: All peeling

[0029]

[Table 5]

[0030]

[Table 6]

[0031]

[Table 7]

[0032]

[Table 8]

As is clear from the results of Tables 5 to 8, the polyurethane resin pressure-sensitive adhesives of Examples 1 to 9 having the chemical structure defined in the present invention and containing a specific amount of the metal sulfonate group have the initial adhesive strength. It has a high viscosity, is capable of holding the adhesive force for a long time, and is excellent in cold resistance and heat resistance, and is also excellent in solubility in a solvent, so that it has a low viscosity and excellent workability. On the other hand, Comparative Example 1 outside the scope of the present invention
The adhesives Nos. 8 to 8 were significantly inferior to most or any of the above-mentioned adhesive properties.

[0034]

The polyurethane resin of the present invention is
When used as an adhesive for various adhesive processed products such as adhesive tapes, labels, sheets or double-sided adhesive tapes,
High initial adhesive strength, excellent heat resistance of adhesive strength, cold resistance, long-term storage stability, etc., good solubility in solvents, and low viscosity of the resin solution, so it is easy to handle. There is. In addition, since high solidification is possible, it has a well-balanced characteristic that it is excellent in terms of safety and hygiene by streamlining the work process by shortening the drying time and reducing the amount of solvent discharged during drying.

Claims (3)

[Claims] 1. A pressure-sensitive adhesive comprising a polyurethane-based resin obtained by reacting an active hydrogen compound containing a polyol having one or more hydrocarbon group side chains having 1 to 10 carbon atoms with an organic polyisocyanate, the polyurethane-based adhesive comprising: The above-mentioned pressure-sensitive adhesive, wherein the resin is a polyurethane-based resin having 0.001 to 1.0 mmol / g of metal sulfonate group in the molecule per polymer. 2. A polyurethane resin obtained by reacting an active hydrogen compound containing a polyol having one or more hydrocarbon group side chains having 1 to 10 carbon atoms with an organic polyisocyanate is crosslinked with a polyisocyanate curing agent. The pressure-sensitive adhesive as described above, wherein the polyurethane-based resin is a polyurethane-based resin having a metal sulfonate group in the molecule of 0.001 to 1.0 mmol / g per polymer. 3. The polyol is a polyester diol obtained by reacting a diol having one or more hydrocarbon group side chains having 1 to 10 carbon atoms with a dicarboxylic acid or a derivative thereof, and the polyester diol is a sulfone. The pressure-sensitive adhesive according to claim 1, which has an acid metal base.