JP2017179118A - Adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive tape less in adhesive residue and lamination trace when peeled from an adherend.SOLUTION: An adhesive tape 1 has a substrate 2 and an adhesive layer 3 laminated on at least one surface of the substrate 2, the adhesive layer 3 contains a natural rubber, an epoxidated natural rubber and an isocyanate-based crosslinking agent. The adhesive layer 3 has content ratio of the natural rubber and the epoxidated natural rubber (natural rubber/epoxidated natural rubber) in a range of 99/1 to 70/30 by weight ratio.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an adhesive tape.

  As a background art, an adhesive tape having an adhesive layer containing a rubber component is known. For example, Patent Document 1 discloses an adhesive tape including an adhesive layer containing isoprene-based rubber, a curing agent, a tackifier, and a zirconium compound.

JP 2014-34582 A

By the way, an adhesive tape including an adhesive layer containing a rubber component may be used for temporarily fixing an apparatus such as an electric device. In such a case, for example, when the equipment is transported or assembled, the parts are temporarily firmly fixed with adhesive tape, and when necessary, the adhesive tape is peeled off and the parts are fixed in place. Install. The most general use example is temporary fixing of an opening / closing part and a storage box in an apparatus such as an electric device.
Thus, when using an adhesive tape for temporary fixing of an apparatus, after peeling an adhesive tape, problems, such as the adhesive residue which an adhesive remains on the surface of a to-be-adhered body, the sticking trace which the surface of an to-be-adhered body becomes cloudy, arise. There is a fear. In particular, when adhesive tape is used to fix parts of electrical equipment used in general households, the appearance of the electrical equipment deteriorates due to adhesive residue or traces after the adhesive tape has been removed, or the remaining glue is forcibly removed. There is a concern that the electrical equipment may be damaged due to this.

  This application is an invention made in order to solve such a problem, and it aims at providing the adhesive tape with few glue residue and sticking marks at the time of peeling from an adherend.

The pressure-sensitive adhesive tape to which the present invention is applied is a pressure-sensitive adhesive tape having a base material and a pressure-sensitive adhesive layer laminated on at least one surface of the base material, and the pressure-sensitive adhesive layer comprises natural rubber, epoxidized natural It contains rubber and an isocyanate-based crosslinking agent.
Here, the pressure-sensitive adhesive layer is characterized in that the content ratio of natural rubber to epoxidized natural rubber (natural rubber / epoxidized natural rubber) is in the range of 99/1 to 70/30 by weight ratio. can do.
The epoxidized natural rubber contained in the pressure-sensitive adhesive layer may have an epoxidation rate of 25 mol% or more.
Further, in the pressure-sensitive adhesive layer, the content of the isocyanate crosslinking agent is in the range of 6 to 15 parts by weight with respect to 100 parts by weight of the rubber component including natural rubber and epoxidized natural rubber. It can be.
Furthermore, the pressure-sensitive adhesive layer may be characterized by not containing a crosslinking accelerator comprising a metal catalyst.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive tape with few adhesive residue at the time of peeling from a to-be-adhered body and a sticking trace can be provided.

It is the figure which showed an example of the structure of the adhesive tape to which this Embodiment is applied.

  In order to solve the above-mentioned problems, the present inventors considered that it is necessary to improve the cohesive force of the pressure-sensitive adhesive layer without reducing the pressure-sensitive adhesive properties of the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer. In the pressure-sensitive adhesive composition, when an isocyanate-based crosslinking agent was added to natural rubber, the breaking strength / breaking elongation of the pressure-sensitive adhesive composition was improved to some extent without adding a crosslinking accelerator composed of a metal catalyst. From this, it was found that adding an isocyanate-based crosslinking agent to natural rubber in the pressure-sensitive adhesive composition has a certain effect on improving the cohesive strength of the pressure-sensitive adhesive layer.

  However, in the pressure-sensitive adhesive composition in which natural rubber is crosslinked with an isocyanate-based crosslinking agent in the absence of a crosslinking accelerator composed of a metal catalyst, the material is widely used for adherends such as electrical equipment (ABS, SUS, etc.). The cohesive force is still insufficient to suppress the adhesive residue when peeled, and it has not been possible to completely solve the above-described problems.

  In order to solve the above-mentioned problems, the present inventors have conducted a further study on a method for further improving the cohesive force of the pressure-sensitive adhesive layer without reducing the pressure-sensitive adhesive properties of the pressure-sensitive adhesive composition. It was found that by adding epoxidized natural rubber to the system to which a crosslinking agent was added, the breaking strength and breaking elongation of the pressure-sensitive adhesive composition were improved, and as a result, the amount of aggregation of the pressure-sensitive adhesive layer was improved. . And by using such an adhesive composition as an adhesive layer, it confirmed that the adhesive residue and sticking trace at the time of peeling an adhesive tape from a to-be-adhered body reduced, and came to make this invention.

Embodiments of the present invention will be described below.
FIG. 1 is a diagram illustrating an example of a configuration of an adhesive tape 1 to which the exemplary embodiment is applied. The adhesive tape 1 of this Embodiment is used for uses, such as temporary fixing of the opening-and-closing part in apparatuses, such as an electric equipment, and a storage box, for example.
As shown in FIG. 1, the adhesive tape 1 to which this Embodiment is applied has the structure where the base material 2 and the adhesive layer 3 were laminated | stacked.
In addition, although illustration is abbreviate | omitted, the adhesive tape 1 may be equipped with the anchor agent layer between the base material 2 and the adhesive layer 3 as needed. In addition, the surface of the base material 2 (the surface opposite to the surface on which the pressure-sensitive adhesive layer 3 is laminated) may be subjected to a surface treatment such as a peeling treatment. The adhesive tape 1 may be provided with a release liner on the adhesive layer 3.

[Adhesive layer]
The pressure-sensitive adhesive layer 3 of the present embodiment includes natural rubber, epoxidized natural rubber, and a crosslinking agent. The pressure-sensitive adhesive layer 3 may further contain additives such as a tackifier, an anti-aging agent, and a colorant as necessary. Further, the pressure-sensitive adhesive layer 3 may contain a rubber component other than natural rubber and epoxidized natural rubber, for example, synthetic rubber such as butyl rubber, butadiene rubber, isoprene rubber, polyisobutylene rubber, or a thermoplastic elastomer.
Note that the pressure-sensitive adhesive layer 3 of the present embodiment includes a release treatment agent on the surface of the base material 2 (the surface opposite to the surface on which the pressure-sensitive adhesive layer 3 is laminated) from the viewpoint of environmental compatibility such as REACH regulations. From the viewpoint of the influence of a side reaction (contamination to the adherend) caused by the contact between the adhesive layer 3 and the crosslinking accelerator in the pressure-sensitive adhesive layer 3, it is preferable that a crosslinking accelerator composed of a metal catalyst is not included.

Although details will be described later, in the pressure-sensitive adhesive tape 1 of the present embodiment, the pressure-sensitive adhesive layer 3 includes epoxidized natural rubber in addition to natural rubber as a rubber component. By reacting, an appropriate cross-linked structure (three-dimensional network structure having a long distance between cross-linking points) is formed. Further, the epoxidized natural rubber serves as an auxiliary crosslinking point or pseudo-crosslinking point. It is presumed that the cohesive force of the pressure-sensitive adhesive layer 3 is improved due to the combination of both effects.
Thereby, compared with the case where the adhesive layer 3 does not contain epoxidized natural rubber as a rubber component, for example, the cohesive force of the adhesive layer 3 increases. And the adhesive residue with respect to a to-be-adhered body at the time of peeling the adhesive tape 1 after affixing the adhesive tape 1 to a to-be-adhered body can be reduced, for example.

In particular, when the pressure-sensitive adhesive layer 3 does not contain a crosslinking accelerator made of a metal catalyst, the improvement in cohesion due to the epoxidized natural rubber becomes significant. That is, when the pressure-sensitive adhesive layer 3 does not contain a crosslinking accelerator made of a metal catalyst, the cohesive force often becomes insufficient if the pressure-sensitive adhesive layer 3 does not contain epoxidized natural rubber as a rubber component. When the pressure-sensitive adhesive layer 3 contains epoxidized natural rubber as a rubber component, its cohesive force is sufficient to use the pressure-sensitive adhesive tape 1 for the application of the present invention, even if it does not contain a crosslinking accelerator composed of a metal catalyst. Can be.
In this embodiment, “adhesive residue” means an adhesive that forms the adhesive layer 3 on the surface of the adherend when the adhesive tape 1 is peeled off after the adhesive tape 1 is attached to the adherend. A phenomenon in which the agent remains.

(Natural rubber)
Natural rubber is a substance mainly composed of cis-1,4-polyisoprene contained in the sap of a rubber tree, and is produced by addition polymerization in vivo. Natural rubber has a molecular weight distribution with peaks around 300,000 and 2 million. Natural rubber contains 3% to 4% of non-rubber components such as proteins and lipids. It is presumed that the protein has an N-terminal (amino group) and a C-terminal (carboxyl group).
Natural rubber molecules have many unclear parts regarding the terminal structure, but one end (starting end) of the cis-1,4-isoprene unit is an amino group that is a protein end (functional group having active hydrogen in one molecule). And a carboxyl group-containing amino acid polymerized at a low molecular weight level: a short-chain polypeptide), and a phospholipid is bonded to the other end (stop end), and a long-chain fatty acid is further added to the phospholipid end. It is said to be an ester-linked structure. Furthermore, it is said that, in the process of producing natural rubber, a small amount of functional groups having active hydrogen such as hydroxyl groups and carboxyl groups may be introduced into the molecular chain of natural rubber.
Although details are not clear, as described above, any of these functional groups having active hydrogen reacts with an isocyanate group of an isocyanate-based crosslinking agent or an epoxy group of an epoxidized natural rubber to form an appropriate crosslinked structure. Is possible.

By the way, natural rubber is composed of a dimethylallyl group bonded to a functional group (starting end) that interacts with a protein, two trans-1,4-isoprene units, and about 5,000 cis-1,4-isoprene units. And a branched polymer having a cis-1,4-isoprene unit bonded to a phospholipid (stopping terminal) as a basic skeleton. That is, protein ends (starting ends) of a plurality of natural rubber molecules interact and bind around a protein contained as a non-rubber component, and the other phospholipid end (stopping end) of natural rubber is It is considered that the phospholipid ends of a plurality of natural rubbers have a branched structure in which the domains interact with each other in a domain shape. Since natural rubber cis-polyisoprene is hydrophobic and non-rubber components such as proteins and lipids are hydrophilic, a phase separation structure composed of cis-polyisoprene and a non-rubber component is formed in natural rubber. It is thought that.
It is presumed that a part of these natural rubbers having a branched structure further forms an appropriate crosslinked structure with the isocyanate-based crosslinking agent.

  The natural rubber is not particularly limited. For example, TMR (Technically Specified Rubber) such as SMR (Standard Malaysian Rubber), SIR (Standard Indonesian Rubber), STR (Standard Thai Rubber), and high purity natural rubber (HPNR: High- Purity Natural Rubber) is used.

(Epoxidized natural rubber)
In the epoxidized natural rubber, a part of the double bond of the natural rubber described above is substituted with an epoxy group.
As the epoxidized natural rubber, a commercially available epoxidized natural rubber may be used, or the above-described natural rubber may be epoxidized. The method for epoxidizing natural rubber is not particularly limited, and examples thereof include a chlorohydrin method, a direct oxidation method, a hydrogen peroxide method, an alkyl hydroperoxide method, and a peracid method. Examples of the peracid method include a method in which natural rubber is reacted with an organic peracid such as peracetic acid or performic acid.

The epoxidation rate of the epoxidized natural rubber used for the pressure-sensitive adhesive layer 3 of the present embodiment is preferably 25 mol% or more. The higher the epoxidation rate of the epoxidized natural rubber, the more preferable it is at least 25 mol%. Since the epoxy group of the epoxidized natural rubber is present in the molecular skeleton, the reactivity is slightly inferior to the epoxy group having a high degree of freedom existing at the end of the molecular chain. Therefore, the amount of epoxy groups in the epoxidized natural rubber is increased, and the opportunity for contacting with any functional group having active hydrogen contained in the natural rubber is increased as much as possible to facilitate the auxiliary crosslinking reaction. It is preferable to keep it.
In addition, the maximum value of the epoxidation rate of the generally available epoxidized natural rubber is about 50 mol%.

Here, the epoxidation rate of the epoxidized natural rubber means a ratio (mol%) of the number of epoxidized double bonds to the total number of double bonds in the natural rubber before being epoxidized. The epoxidation rate of the epoxidized natural rubber can be determined from, for example, measurement data obtained by dissolving the epoxidized natural rubber in deuterated chloroform and analyzing its nuclear magnetic resonance (NMR). That is, the area intensity A of the signal of the methine proton derived from natural rubber and the area intensity B of the signal of the proton derived from the epoxy group can be obtained and can be obtained by the following formula (1).
Epoxidation rate (%) = B / (A + B) × 100 (1)

  By the way, it is said that the epoxidized natural rubber increases the glass transition temperature by about 1 ° C. every time the epoxidation rate increases by 1 mol%. If the glass transition temperature of natural rubber is about -70 ° C, the glass transition temperatures of epoxidized natural rubber having an epoxidation rate of 25 mol% and 50 mol% are about -45 ° C and about -20 ° C, respectively. Therefore, the larger the epoxidation rate and addition amount of the epoxidized natural rubber, the higher the glass transition temperature of the pressure-sensitive adhesive layer 3, and the pressure-sensitive adhesive layer 3 tends to become harder.

  In the present embodiment, by setting the epoxidation rate of the epoxidized natural rubber to 25 mol% or more, the pressure-sensitive adhesive layer 3 can have any epoxy group contained in the epoxidized natural rubber and active hydrogen contained in the natural rubber. Since the probability of contact with such a functional group increases, the above-described auxiliary crosslinking reaction easily proceeds. Thereby, compared with the case where the epoxidation rate of an epoxidized natural rubber is less than 25 mol%, the cohesion force of the adhesive layer 3 increases. And the adhesive residue with respect to a to-be-adhered body at the time of peeling the adhesive tape 1 after affixing the adhesive tape 1 to a to-be-adhered body can be reduced, for example.

  The ratio of the natural rubber and the epoxidized natural rubber contained in the pressure-sensitive adhesive layer 3 is preferably in the range of natural rubber / epoxidized natural rubber = 99/1 to 70/30 in weight ratio. By setting the ratio of natural rubber and epoxidized natural rubber within this range, the probability that the epoxy group of the epoxidized natural rubber and any functional group having active hydrogen contained in the natural rubber will be increased, It is possible to facilitate the auxiliary crosslinking reaction of the pressure-sensitive adhesive layer 3.

Here, the compatibility between the hydrophobic natural rubber and the highly polar epoxidized natural rubber is not so good. For this reason, when these are mixed within the above range, the sea-island in which the epoxidized natural rubber is dispersed in the matrix phase (sea) of natural rubber as a phase (island) composed of substantially spherical particles of micron size. It is thought to form a structure. Therefore, it is speculated that the auxiliary crosslinking reaction related to the epoxy group of the epoxidized natural rubber described above mainly occurs at the interface of the sea-island structure.
Further, as described above, the natural rubber has a phase separation structure composed of a hydrophobic cis-polyisoprene and a hydrophilic non-rubber component. For this reason, the epoxidized natural rubber may form a single phase (island) or a pseudo phase (island) that is compatible with or close to the hydrophilic non-rubber component in the natural rubber.

Furthermore, as described above, epoxidized natural rubber has a higher glass transition temperature than natural rubber. Therefore, when natural rubber and epoxidized natural rubber are mixed, a relatively soft natural rubber phase is obtained. A slightly harder phase of epoxidized natural rubber will be dispersed with some covalent bonds at the phase interface. And the epoxidized natural rubber phase (island) or the pseudo phase (island) in which the epoxidized natural rubber and the non-rubber component of natural rubber are close to each other plays a role as a kind of reinforcing filler in natural rubber. However, it may be functioning as a stopper for suppressing breakage of the polymer. It is speculated that this effect also contributes to the improvement of the cohesive force of the pressure-sensitive adhesive layer 3.
Even if there is almost no covalent bond formed by cross-linking at the sea-island structure interface between natural rubber and epoxidized natural rubber, the phase of epoxidized natural rubber (island) or epoxidized natural rubber and natural rubber The pseudo phase (island) in close proximity to the non-rubber component is a slightly harder phase and has some interaction with the terminal structure portion of the natural rubber or the functional group of the molecular chain. Therefore, the phase of the epoxidized natural rubber (island) or the pseudo phase (island) in which the epoxidized natural rubber and the non-rubber component of the natural rubber are close to each other is a role of reinforcing filler or pseudo-crosslinking. It is presumed to have a point role.

On the other hand, when the content ratio of the epoxidized natural rubber in the rubber component of the pressure-sensitive adhesive layer 3 is less than 1%, there is almost no effect of proceeding the cross-linking by the epoxy group, so that there is a possibility that the cross-linking varies depending on the lot of natural rubber. is there. In this case, since the cohesive force of the pressure-sensitive adhesive layer 3 is reduced, for example, when the pressure-sensitive adhesive tape 1 is peeled off after the pressure-sensitive adhesive tape 1 is attached to the adherend, there is a possibility that an adhesive residue may be generated on the adherend.
Further, when the content ratio of the epoxidized natural rubber in the rubber component of the pressure-sensitive adhesive layer 3 exceeds 30%, the effect of proceeding crosslinking in the pressure-sensitive adhesive layer 3 is saturated, and no further effect can be obtained. Further, when the content ratio of the epoxidized natural rubber exceeds 30%, the glass transition temperature of the pressure-sensitive adhesive layer 3 increases, so that the ball tack of the pressure-sensitive adhesive layer 3 may be lowered.

(Isocyanate-based crosslinking agent)
In the pressure-sensitive adhesive layer 3 of the present embodiment, any functional group of amino group, hydroxyl group and carboxyl group having active hydrogen contained in the natural rubber described above, or the epoxy group of the epoxidized natural rubber has these functional groups. From the viewpoint of causing a crosslinking reaction between the hydroxyl group formed when the ring is opened by the reaction with an isocyanate group and an isocyanate group, an isocyanate-based crosslinking agent composed of an isocyanate compound is used as a crosslinking agent.

  Although it does not specifically limit as an isocyanate compound, It is preferable to use the polyfunctional isocyanate compound containing an at least 2 isocyanate group in a molecule | numerator. Examples of the polyfunctional isocyanate compound include tolylene diisocyanate, diphenylmethane diisocyanate, water-added diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, and the like, or polyisocyanates obtained by reaction of these diisocyanates with triols, for example, Adducts of tolylene diisocyanate and trimethylol propane, adducts of hexamethylene diisocyanate and trimethylol propane, or trimers of tolylene diisocyanate derived from these diisocyanates, trimers of hexamethylene diisocyanate, biuret-modified hexa Methylene diisocyanate, carbodiimide modified diphenylmethane diisocyanate Over doors and the like.

In the present embodiment, it is preferable to use an adduct type polyisocyanate among the above-mentioned isocyanate compounds.
By using an adduct-type polyisocyanate as the isocyanate-based cross-linking agent, the pressure-sensitive adhesive layer 3 is more advanced in cross-linking of natural rubber and epoxidized natural rubber than when, for example, isocyanurate-type polyisocyanate is used. It becomes possible. Thereby, the cohesive force of the pressure-sensitive adhesive layer 3 is increased, and for example, the adhesive residue when the pressure-sensitive adhesive tape 1 is peeled off after the pressure-sensitive adhesive tape 1 is attached to the adherend can be reduced.

Moreover, in this Embodiment, it is preferable to use the polyfunctional isocyanate type crosslinking agent containing the polyisocyanate compound obtained by reaction of diisocyanate and triol among the above-mentioned isocyanate compounds.
By using such an isocyanate-based crosslinking agent, when the above-described isoprene-based rubber is crosslinked, it can be crosslinked in a network. As a result, the cohesive force of the pressure-sensitive adhesive layer 3 can be further increased, and the adhesive residue on the adherend can be reduced when the adhesive tape is attached to the adherend and then peeled off. become.

As an isocyanate type crosslinking agent, 1 type may be used independently among said isocyanate compounds, and it may be used in combination of 2 or more type.
In addition, as an isocyanate type crosslinking agent containing the above-mentioned isocyanate compound, Tosoh Corporation coronate L (brand name), Tosoh Corporation coronate HL (brand name), etc. can be used, for example.

In the pressure-sensitive adhesive layer 3 of the present embodiment, the content of the isocyanate crosslinking agent relative to the rubber component (natural rubber, epoxidized natural rubber) is 6 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the rubber component. A range is preferable.
When the content of the isocyanate-based crosslinking agent relative to 100 parts by weight of the rubber component is less than 6 parts by weight, when any functional group having active hydrogen contained in the natural rubber or the epoxy group of the epoxidized natural rubber is opened The reaction between the formed hydroxyl group and the isocyanate crosslinking agent does not proceed sufficiently. In this case, the cohesive force of the pressure-sensitive adhesive layer 3 becomes insufficient, and when the pressure-sensitive adhesive tape 1 is peeled off after the pressure-sensitive adhesive tape 1 is attached to the adherend, an adhesive residue on the adherend may occur.
On the other hand, when the content of the isocyanate-based crosslinking agent with respect to 100 parts by weight of the rubber component exceeds 15 parts by weight, the initial adhesive force of the pressure-sensitive adhesive layer 3 may be reduced. Further, when the content of the isocyanate crosslinking agent with respect to 100 parts by weight of the rubber component exceeds 15 parts by weight, the adhesion between the unreacted isocyanate crosslinking agent and the adherend when the adhesive tape 1 is attached to the adherend. When the force improves with time and, as a result, the adhesive tape 1 is peeled off, an adhesive residue on the adherend may occur.

  In the pressure-sensitive adhesive layer 3 of the present embodiment, as a crosslinking agent, in addition to the above-mentioned isocyanate crosslinking agent, other than an epoxy crosslinking agent, a metal chelate crosslinking agent, an amine crosslinking agent, a melamine crosslinking agent, and the like. The crosslinking agent may be included.

(Tackifier)
As the tackifier, those having good compatibility with natural rubber are used. Specifically, rosin ester resin, hydrogenated rosin ester resin, aliphatic (C5) petroleum resin, alicyclic petroleum resin, aromatic (C9) petroleum resin, aliphatic aromatic copolymer (C5C9) petroleum resin, hydrogenated petroleum resin, terpene resin, hydrogenated terpene resin, terpene phenol resin, alkylphenol resin, carboxylic acid resin, etc. can be used, but are not limited to these. It is not a thing.

(Anti-aging agent)
The anti-aging agent is added as necessary for the purpose of suppressing deterioration of the pressure-sensitive adhesive layer 3. Although it does not specifically limit as an anti-aging agent, For example, anti-aging agents, such as a phenol type, an amine type, and a benzimidazole type, can be used.

  Examples of the phenol-based anti-aging agent include 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, styrenated phenol, and 2,5-diphenol. -T-butylhydroquinone, 2,5-di-t-amylhydroquinone, 2,2-methylenebis (4-methyl-6-t-butylphenol), 2,2-methylenebis (4-ethyl-6-t-butylphenol) 4,4-thiobis (6-tert-butyl-3-methylphenol), 4,4-butylidenebis- (3-methyl-6-tert-butylphenol), 1,3,5-trimethyl-2,4,6 -Tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propiyl Nate] methane, 2-t-butyl-6- (3-t-butyl-5-methyl-2-hydroxybenzyl) -4-methylphenyl acrylate, n-octadecyl-3- (4-hydroxy-3,5- And di-t-butylphenyl) propionate.

Examples of the amine-based antiaging agent include poly (2,2,4-trimethyl-1,2-dihydroquinoline), 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline, Phenyl-α-naphthylamine, alkylated diphenylamine, octylated diphenylamine, 4,4-bis (α, α-dimethylbenzyl) diphenylamine, N, N-di-β-naphthyl-p-phenylenediamine, N-phenyl-N- Isopropyl-p-phenylenediamine, N-phenyl-N- (1,3-dimethylbutyl) -p-phenylenediamine, p- (p-toluenesulfonylamido) diphenylamine, N- (3-methacryloyloxy-2-hydroxypropyl ) -N-phenyl-p-phenylenediamine and the like.
Furthermore, examples of the benzimidazole-based antiaging agent include 2-mercaptobenzimidazole and 2-mercaptomethylbenzimidazole.
The anti-aging agent is not particularly limited to these.

(Coloring agent)
The colorant is added as necessary for the purpose of coloring the pressure-sensitive adhesive layer 3.
Any colorant can be used without any particular limitation. For example, diarylide colorants, condensed azo colorants, quinacridone colorants, vat colorants, isoindolinone colorants, phthalocyanine colorants, aniline colorants, titanium oxide, nickel titanium, yellow iron oxide, There are petals, ultramarine, cobalt blue, chromium oxide, iron black, yellow lead, chrome orange, molybdenum red, cadmium colorants, carbon black, etc., preferably copper phthalocyanine, nickel as titanium oxide or phthalocyanine colorants Phthalocyanine, cobalt phthalocyanine, and the like can be used.

(solvent)
The pressure-sensitive adhesive layer 3 of the present embodiment is usually formed from a pressure-sensitive adhesive composition prepared by dissolving natural rubber, epoxidized natural rubber, isocyanate-based crosslinking agent or the like in a solvent.
Examples of the solvent used for adjusting the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer 3 include toluene, benzene, tetrahydrofuran, ethyl acetate, butyl acetate, methyl ethyl ketone, acetone, and mixed solvents thereof.

[Base material]
The base material 2 used for the adhesive tape 1 of this Embodiment is not specifically limited, For example, plastic, metal, paper, cloth, etc. can be used. Among these, it is preferable to use a plastic substrate made of polyethylene terephthalate, polypropylene, or the like.

  The surface of the substrate 2 (the surface opposite to the surface on which the pressure-sensitive adhesive layer 3 is laminated) may be subjected to a surface treatment such as a peelability improving treatment. Known treatment agents used on the surface of the substrate 2 include silicone resins, long-chain alkyl vinyl monomer polymers, fluorinated alkyl vinyl monomer polymers, polyvinyl alcohol carbamate, and the like. Among these, it is preferable to use a silicone resin because it has excellent characteristics for improving the peeling performance on the surface of the substrate 2.

[Production method of adhesive tape]
Then, the manufacturing method of the adhesive tape 1 of this Embodiment is demonstrated.
When the pressure-sensitive adhesive tape 1 is manufactured, first, natural rubber, epoxidized natural rubber, a tackifier and, if necessary, an anti-aging agent are mixed in a solvent such as toluene, and then mixed into this mixed solution. An isocyanate-based crosslinking agent is added to produce a pressure-sensitive adhesive composition.
Subsequently, the pressure-sensitive adhesive composition is applied to one surface of the substrate 2 using a coater or the like so that the thickness of the pressure-sensitive adhesive layer 3 after drying is uniform. Then, the adhesive tape 1 with which the adhesive layer 3 was laminated | stacked on the base material 2 is obtained by drying and hardening the apply | coated adhesive composition at predetermined temperature.
As described above, surface treatment may be performed on the substrate 2, or an anchor agent layer may be formed between the substrate 2 and the pressure-sensitive adhesive layer 3.

[How to use adhesive tape]
The pressure-sensitive adhesive tape 1 of the present embodiment is used as a pressure-sensitive adhesive tape for temporary fixing used for temporarily fixing an apparatus such as an electric device or a storage box, for example. For example, when transporting or assembling an electric device such as a refrigerator or a washing machine, the component is attached and fixed to the main body of the electric device with the adhesive tape 1. Then, when the transportation or assembly of the electric equipment is completed and the fixing becomes unnecessary, the attached adhesive tape 1 is peeled off from the electric equipment and its components.

Here, as described above, the pressure-sensitive adhesive layer 3 of the present embodiment includes natural rubber, epoxidized natural rubber, and an isocyanate-based crosslinking agent. By adopting such a configuration, the adhesive tape 1 of the present embodiment reduces adhesive residue on the adherend after being peeled off after being attached to the adherend.
More specifically, when the pressure-sensitive adhesive layer 3 contains natural rubber and epoxidized natural rubber as rubber components, first, any functional group having active hydrogen contained in natural rubber, or epoxidized natural rubber The hydroxyl group formed when the epoxy group is ring-opened reacts with the isocyanate-based crosslinking agent to form an appropriate crosslinked structure (three-dimensional network structure having a long distance between crosslinking points). Furthermore, the epoxidized natural rubber serves as an auxiliary crosslinking point or pseudo-crosslinking point. It is presumed that the cohesive force of the pressure-sensitive adhesive layer 3 is improved due to the combination of both effects.
Thereby, compared with the case where the adhesive layer 3 does not contain epoxidized natural rubber as a rubber component, for example, the cohesive force of the adhesive layer 3 increases. And the adhesive residue with respect to a to-be-adhered body at the time of peeling the adhesive tape 1 after affixing the adhesive tape 1 to a to-be-adhered body can be reduced, for example.

By the way, in the adhesive tape for temporary fixing used for temporarily fixing devices such as electric devices and storage boxes, in order to reduce adhesive residue on the adherend after peeling from the adherend, the adhesive layer is cross-linked. It is necessary to advance and increase the cohesive force. In such an adhesive tape, a crosslinking accelerator composed of a metal catalyst such as a zirconium catalyst or a tin catalyst may be added for the purpose of advancing a crosslinking reaction between the natural rubber and the crosslinking agent in the adhesive layer.
However, when a crosslinking accelerator composed of a metal catalyst such as a zirconium catalyst or a tin catalyst is used for the pressure-sensitive adhesive layer, depending on the type of the metal catalyst, when the pressure-sensitive adhesive tape is attached to the adherend and then peeled off, There may be a case where an adherence mark (a cloud of the adherend surface that can be visually confirmed but not a residue) remains on the adherend. In particular, when a crosslinking accelerator made of a metal catalyst is added to the pressure-sensitive adhesive layer, when a release agent made of a silicone resin is applied to the surface of the substrate (the surface opposite to the pressure-sensitive adhesive layer), Sticking marks are likely to remain. This is because the release agent on the substrate surface reacts with the metal catalyst contained in the pressure-sensitive adhesive layer in a state where the pressure-sensitive adhesive tape is wound, and the generated by-product is partially transferred to the pressure-sensitive adhesive layer 3. Presumed to be derived.

  On the other hand, in this Embodiment, since the crosslinking accelerator which consists of a metal catalyst is not used for the adhesive layer 3, when sticking the adhesive tape 1 on an adherend and peeling off, it adheres to an adherend. The occurrence of sticking marks can be suppressed. In addition, as described above, the pressure-sensitive adhesive layer 3 contains natural rubber and epoxidized natural rubber as rubber components, and also contains an isocyanate-based cross-linking agent as a cross-linking agent. Even if it is a case where is not used, bridge | crosslinking of the adhesive layer 3 can be advanced moderately and the cohesion force of the adhesive layer 3 can be raised. For this reason, even when not using the crosslinking accelerator which consists of a metal catalyst in the adhesive layer 3, after adhering the adhesive tape 1 to an adherend, with respect to the adherend when peeling the adhesive tape 1 The adhesive residue can be reduced.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited to the following examples.

(Examples 1-10, Comparative Examples 1-3)
1. Adjustment of pressure-sensitive adhesive composition A pressure-sensitive adhesive composition was prepared according to the formulation shown in Tables 1 and 2 (unit: parts by weight / solid content) described later.
First, natural rubber “Thick pale Crap No. 1” (trade name; manufactured by Nomura Trading Co., Ltd.), epoxidized natural rubber “ENR-50” (trade name, epoxidation rate 50 mol%; manufactured by MUANG MAI GUTHURIE), adhesive The imparting agent “Arcon P-125” (trade name; manufactured by Arakawa Chemical Industries) and the anti-aging agent “Irganox 1010” (trade name; manufactured by BASF) were dissolved in a solvent (toluene) and stirred for 12 hours. Thereafter, an isocyanate-based crosslinking agent “Coronate L-55E” (trade name; manufactured by Tosoh Corporation) and a solvent (ethyl acetate) were added to this mixed solution and stirred for 20 minutes to obtain an adhesive composition. In Examples 8 and 9, “ENR-25” (trade name, epoxidation rate: 25 mol%; manufactured by MUANG MAI GUTHURIE) was used as the epoxidized natural rubber instead of “ENR-50”.
In Comparative Example 1, no epoxidized natural rubber is used in the pressure-sensitive adhesive composition. Moreover, in the comparative example 2, the isocyanate type crosslinking agent is not used for the adhesive composition. Furthermore, in Comparative Example 3, epoxidized natural rubber is not used in the pressure-sensitive adhesive composition, and dibutyltin dilaurate is added as a crosslinking accelerator.

2. Adjustment of pressure-sensitive adhesive tape Subsequently, the pressure-sensitive adhesive composition adjusted by the above production method was applied to the substrate 2 to adjust the pressure-sensitive adhesive tape 1.
Specifically, after forming an anchoring agent layer on the surface of the substrate 2 (polypropylene film; manufactured by Nihon Matai Co., Ltd.), the pressure-sensitive adhesive composition was applied. Further, the surface of the substrate 2 opposite to the surface coated with the pressure-sensitive adhesive composition was subjected to a peeling treatment with a silicone resin. Then, the base material 2 which applied the adhesive composition and gave the peeling process was wound around the paper tube.
Thereafter, aging was performed at 40 ° C. for 120 hours to obtain a pressure-sensitive adhesive tape 1 in which the pressure-sensitive adhesive layer 3 was laminated on the substrate 2. In the pressure-sensitive adhesive tape 1, the thickness of the base material 2 was about 60 μm, and the thickness of the pressure-sensitive adhesive layer 3 was about 30 μm.

3. Evaluation method Subsequently, the evaluation method of the adhesive tape 1 is demonstrated.
(1) Measurement of ball tack The ball tack of the pressure-sensitive adhesive tape 1 was measured according to the tilting ball tack method described in JIS Z 0237 (2009).
Specifically, the high carbon chromium bearing steel is fixed to an inclined plate with an inclination angle of 30 ° so that the adhesive layer 1 is on the upper surface and the length of the runway is 100 mm. Were rolled by the method described in JIS Z 0237 (2009). At this time, balls having a diameter of 2/32 inch to 1 inch were used. Of the balls that stop on the surface of the pressure-sensitive adhesive layer 3 when the balls are rolled, the value of the ball number with the largest diameter is specified, and the evaluation results are shown in Tables 1 and 2. The ball number can be obtained by multiplying the ball diameter by 32 times. That is, a ball having a diameter of 1 inch is called a ball number 32, and a ball having a diameter of 2/32 is called a ball number 2. The larger the ball number, the stronger the tack force (initial adhesive force) of the pressure-sensitive adhesive layer 3.

(2) Measurement of holding force The holding force of the adhesive tape 1 was measured based on the holding force test described in JIS Z 0237 (2009).
Specifically, the adhesive tape 1 was affixed to a stainless steel plate (SUS304) with a surface finish BA, and the amount of deviation (mm) when held for 24 hours with a predetermined weight attached was measured. Moreover, when the adhesive tape 1 peeled off from the stainless steel plate and dropped before 24 hours passed, the elapsed time (minutes) from the start of measurement until the adhesive tape 1 dropped was measured.
In addition, when using the adhesive tape 1 for temporary fixation of an electric equipment etc., it is preferable that the deviation | shift amount of the adhesive tape 1 in a holding power test is 25 mm or less.

(3) Measurement of adhesive strength The adhesive strength of the adhesive tape 1 was measured based on the adhesive strength test described in JIS Z 0237 (2009).
Specifically, adhesive tape 1 is attached to each of a stainless steel plate (SUS304), a glass plate, an ABS plate (acrylonitrile, butadiene (Butadiene), styrene (Styrene) copolymer synthetic resin) of surface finish BA. The sheet was pressed by a total of 2 reciprocations at a speed of 10 mm / s with a roller having a mass of 2000 g. Thereafter, the film was peeled off in 180 ° direction at a speed of 300 mm / min within 1 minute, and the adhesive force was measured.
The pressure-sensitive adhesive tape 1 to be used was 19 mm or 25 mm wide, and the measurement result of the adhesive strength was converted to 10 mm width (unit: N / 10 mm).

(4) Adhesive residue test The adhesive residue test is a test for evaluating the residue of an adhesive or the like on the adherend after the adhesive tape 1 is attached to and peeled off from the adherend.
After affixing the adhesive tape 1 to an ABS molded product (adhered body), the adhesive tape 1 was reciprocated once with a roller having a mass of 2000 g. After storing this at 60 ° C. for 2 days and further at 23 ° C. for 2 days, the adhesive tape 1 was peeled off by 90 ° at a stretch by hand.
The phenomenon in which the adhesive constituting the adhesive layer 3 of the adhesive tape 1 remains on the surface of the adherend in the part where the adhesive tape 1 is adhered to the adherend is called “adhesive residue”. It was evaluated by.
Evaluation of the adhesive residue test was performed according to the following criteria.
A: The adhesive residue cannot be confirmed visually or by palpation.
B: Residue of the adhesive is generated in less than 5% of the sticking area.
C: Residue of the adhesive occurs at 5% or more of the pasting area.

(5) Edge glue residue test The edge glue residue test is a test for evaluating the residue of the adhesive or the like on the adherend at the peeling start portion after the adhesive tape 1 is attached to the adherend and peeled off. .
After affixing the adhesive tape 1 to an ABS molded product (adhered body), the adhesive tape 1 was reciprocated once with a roller having a mass of 2000 g. After storing this at 60 ° C. for 2 days and further at 23 ° C. for 2 days, the adhesive tape 1 was peeled off by 90 ° at a stretch by hand.
The phenomenon that the adhesive constituting the adhesive layer 3 of the adhesive tape 1 remains on the surface of the adherend at the part where the adhesive tape 1 starts to be peeled out of the part of the adherend to which the adhesive tape 1 has been applied. This was called “edge glue residue” and was evaluated by visual inspection and palpation.
The evaluation of the edge adhesive residue test was performed according to the following criteria.
A: The adhesive residue cannot be confirmed visually or by palpation.
B: Although the adhesive residue cannot be confirmed visually, it can be slightly confirmed by palpation.
C: The adhesive residue can be confirmed visually and by palpation.

(6) Sticking mark test The sticking mark test is a test for evaluating the presence or absence of the sticking mark of the adhesive tape 1 on the adherend after the adhesive tape 1 is attached to the adherend and peeled off. Here, the sticking trace of the pressure-sensitive adhesive tape 1 refers to cloudiness of the adherend surface that can be visually observed, although it is not the above-mentioned adhesive residue.
The adhesive tape 1 was affixed on the glass plate, and was reciprocated once by a roller having a mass of 200 g to be pressure-bonded. Subsequently, it was left for 168 hours in a constant temperature bath at a temperature of 55 ° C. and a relative humidity of 95%, and then taken out. And the adhesive tape 1 was peeled from the to-be-adhered body at 0 degreeC, and the surface of the to-be-adhered body was observed.
The sticking mark test was evaluated according to the following criteria.
A: Nothing is observed on the part of the adherend where the adhesive tape 1 is attached.
C: The cloudy part is observed on the part of the adherend where the adhesive tape 1 is applied.

(7) Shear force test The shear force test is a test for evaluating the durability of the adhesive tape 1 to a force applied in the shear direction.
Specifically, the adhesive tape 1 having a width of 25 mm is cut into a length of 150 mm, the end face 10 mm of the adhesive tape 1 is attached to a stainless steel plate (SUS304) with a surface finish BA, and the total is made at a speed of 10 mm / s with a roller having a mass of 2000 g. Crimped by reciprocating twice. Subsequently, the stainless steel plate was fixed, the adhesive tape 1 was pulled up in the 90 ° direction at a speed of 300 mm / min, and the force when the adhesive tape 1 was peeled off from the stainless steel plate was measured. The measurement result of the shear force was converted to a width of 10 mm (unit: N / 10 mm).

4). Evaluation results Subsequently, the evaluation results of each test on the adhesive tapes 1 of Examples 1 to 10 and Comparative Examples 1 to 3 are shown in Table 1 and Table 2 below.

  As shown in Tables 1 and 2, in Examples 1 to 7, 9, 10, and 12, in which the pressure-sensitive adhesive layer 3 includes natural rubber, epoxidized natural rubber, and an isocyanate-based crosslinking agent, the pressure-sensitive adhesive tape 1 is adhered. It was confirmed that none of the adhesive residue, edge adhesive residue, and sticking marks on the adherend when the pressure-sensitive adhesive tape 1 was peeled off after being attached to the substrate.

However, in Example 6, the content ratio of natural rubber to epoxidized natural rubber (natural rubber / epoxidized natural rubber) is 68/32 by weight, and the content of epoxidized natural rubber is large. And ball-tack evaluation (initial tack feeling) in comparison with Examples 1 to 5 in which the content ratio of natural rubber to epoxidized natural rubber (natural rubber / epoxidized natural rubber) is in the range of 99/1 to 70/30 Was confirmed to be slightly inferior.
Moreover, in Example 8, since content of an isocyanate type crosslinking agent is as small as 5 weight part, compared with Examples 2, 7, and 12 whose content of an isocyanate type crosslinking agent is 6-15 weight part, it is adhesion. It was confirmed that the evaluation of the edge adhesive residue on the adherend was slightly inferior when the adhesive tape 1 was peeled off after the tape 1 was attached to the adherend.
Moreover, in Example 11, since content of an isocyanate type crosslinking agent is as many as 20 weight part, compared with Examples 2, 7, and 12 whose content of an isocyanate type crosslinking agent is 6-15 weight part, it is adhesion. It was confirmed that the adhesive residue evaluation on the adherend was slightly inferior when the adhesive tape 1 was peeled off after the tape 1 was attached to the adherend.
Furthermore, in Example 13, the content ratio of natural rubber to epoxidized natural rubber (natural rubber / epoxidized natural rubber) is 99.5 / 0.5 by weight, and the amount of epoxidized natural rubber added is Compared with Examples 1-5 whose content ratio (natural rubber / epoxidized natural rubber) of natural rubber and epoxidized natural rubber is in the range of 99/1 to 70/30, the pressure-sensitive adhesive tape 1 is covered. It was confirmed that the evaluation of the edge adhesive residue on the adherend was slightly inferior when the adhesive tape 1 was peeled off after being attached to the adherend.

On the other hand, in Comparative Example 1 in which the adhesive layer 3 does not contain epoxidized natural rubber, the edge paste remains on the adherend when the adhesive tape 1 is peeled off after the adhesive tape 1 is attached to the adherend. Was observed.
Further, in Comparative Example 2 in which the pressure-sensitive adhesive layer 3 did not contain an isocyanate-based crosslinking agent, the holding power of the pressure-sensitive adhesive tape 1 was low, and the pressure-sensitive adhesive tape 1 dropped from the stainless steel plate in 866 minutes in the measurement of holding power. Furthermore, when the adhesive tape 1 was peeled off after the adhesive tape 1 was attached to the adherend, an edge glue residue was observed on the adherend.
Furthermore, in Comparative Example 3 in which the pressure-sensitive adhesive layer 3 does not contain epoxidized natural rubber and contains a crosslinking accelerator, the pressure-sensitive adhesive layer 1 is attached when the pressure-sensitive adhesive tape 1 is peeled off after being applied to the adherend. A patch was observed on the body. Further, a slight amount of adhesive residue on the adherend was observed.

DESCRIPTION OF SYMBOLS 1 ... Adhesive tape, 2 ... Base material, 3 ... Adhesive layer

Claims (5)

A pressure-sensitive adhesive tape having a base material and a pressure-sensitive adhesive layer laminated on at least one surface of the base material,
The pressure-sensitive adhesive layer comprises natural rubber, epoxidized natural rubber, and an isocyanate-based crosslinking agent.   The pressure-sensitive adhesive layer is characterized in that the content ratio of natural rubber to epoxidized natural rubber (natural rubber / epoxidized natural rubber) is in a range of 99/1 to 70/30 by weight. The adhesive tape according to 1.   The pressure-sensitive adhesive tape according to claim 1 or 2, wherein an epoxidation rate of the epoxidized natural rubber contained in the pressure-sensitive adhesive layer is 25 mol% or more.   The pressure-sensitive adhesive layer is characterized in that the content of the isocyanate-based crosslinking agent is in the range of 6 to 15 parts by weight with respect to 100 parts by weight of the rubber component including natural rubber and epoxidized natural rubber. The pressure-sensitive adhesive tape according to any one of claims 1 to 3.   The pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer does not contain a crosslinking accelerator composed of a metal catalyst.

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