JP6703875B2 - Adhesive tape - Google Patents

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, there are cases where an adhesive tape provided with an adhesive layer containing a rubber component is used for temporarily fixing a device such as an electric device. In such a case, for example, when transporting or assembling the device, temporarily fix the parts firmly with adhesive tape, and when necessary, peel off the adhesive tape to fix the parts in proper positions or Install. The most general use example is temporary fixing of an opening/closing part or a storage box in a device such as an electric device.
When the adhesive tape is used for temporarily fixing the device in this way, after the adhesive tape is peeled off, problems such as adhesive residue remaining on the surface of the adherend and sticking marks on the surface of the adherend may occur. There is a risk. In particular, when using adhesive tape to fix parts of electrical equipment used in general households, the appearance of electrical equipment deteriorates due to adhesive residue or sticking marks after peeling the adhesive tape, or the remaining adhesive is forcibly removed. There is a concern that this may damage the electrical equipment.

The present application is an invention made in order to solve such a problem, and an object thereof is to provide an adhesive tape having less adhesive residue and sticking traces when peeled 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, wherein the pressure-sensitive adhesive layer is made of natural rubber or epoxidized natural. look-containing rubber and an isocyanate crosslinking agent, the natural rubber and the content ratio of the epoxidized natural rubber (a natural rubber / epoxidized natural rubber), by weight ratio, of 99.5 / 0.5 to 70/30 It is characterized in that it is within the range and does not include a crosslinking promoter comprising a metal catalyst .
Here, the pressure-sensitive adhesive layer is characterized in that the content ratio of natural rubber and 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.
Furthermore, the pressure-sensitive adhesive layer is characterized in that the content of the isocyanate cross-linking agent is in the range of 6 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of a rubber component containing natural rubber and epoxidized natural rubber. it can be.

ADVANTAGE OF THE INVENTION According to this invention, the adhesive tape which has few adhesive residue and a sticking trace when peeled from an adherend 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 problems, the present inventors considered that it is necessary to improve the cohesive force of the pressure-sensitive adhesive layer without lowering the pressure-sensitive adhesive properties of the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer. When an isocyanate-based crosslinking agent was added to natural rubber in the pressure-sensitive adhesive composition, the breaking strength and the breaking elongation of the pressure-sensitive adhesive composition were improved to some extent without adding a crosslinking accelerator composed of a metal catalyst. From this, it was found that the addition of the isocyanate crosslinking agent to the natural rubber in the pressure-sensitive adhesive composition has a certain effect on the improvement of the cohesive force of the pressure-sensitive adhesive layer.

However, in a pressure-sensitive adhesive composition obtained by crosslinking natural rubber with an isocyanate cross-linking agent in the absence of a cross-linking accelerator composed of a metal catalyst, a material (ABS, SUS, etc.) that is widely used for adherends such as electric devices is used. The cohesive force is still insufficient to suppress the adhesive residue when peeled off, and the above-mentioned problems could not be completely solved.

In order to solve the above problems, the present inventors have further diligently studied a method of further improving the cohesive force of the pressure-sensitive adhesive layer without lowering the pressure-sensitive adhesive properties of the pressure-sensitive adhesive composition. By further adding epoxidized natural rubber to the system to which a cross-linking agent has been added, it has been found that the breaking strength and breaking elongation of the pressure-sensitive adhesive composition are improved, and as a result, the aggregation amount of the pressure-sensitive adhesive layer is improved. .. Then, it was confirmed that by using such a pressure-sensitive adhesive composition as a pressure-sensitive adhesive layer, adhesive residue and sticking traces when the pressure-sensitive adhesive tape was peeled from the adherend were reduced, and the present invention was accomplished.

Hereinafter, embodiments of the present invention will be described.
FIG. 1 is a diagram showing an example of the configuration of an adhesive tape 1 to which this embodiment is applied. The pressure-sensitive adhesive tape 1 of the present embodiment is used, for example, for temporary fixing of an opening/closing part in a device such as an electric device or a storage box.
As shown in FIG. 1, an adhesive tape 1 to which this embodiment is applied has a structure in which a base material 2 and an adhesive layer 3 are laminated.
Although illustration is omitted, the adhesive tape 1 may include an anchor agent layer between the base material 2 and the adhesive layer 3 if necessary. Further, 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 peeling treatment. The adhesive tape 1 may have a release liner provided on the adhesive layer 3.

[Adhesive layer]
The pressure-sensitive adhesive layer 3 of the present embodiment contains natural rubber, epoxidized natural rubber and a crosslinking agent. Further, the pressure-sensitive adhesive layer 3 may further contain additives such as a tackifier, an antiaging agent, and a colorant, if 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, and polyisobutylene rubber, or a thermoplastic elastomer.
In addition, the pressure-sensitive adhesive layer 3 of the present embodiment is a release treatment agent from the viewpoint of environmental compatibility such as REACH regulation, and the surface of the substrate 2 (the surface opposite to the surface on which the pressure-sensitive adhesive layer 3 is laminated). From the viewpoint of the side reaction (contamination of the adherend) due to the contact between the adhesive layer 3 and the crosslinking accelerator, it is preferable that the crosslinking accelerator does not include a metal catalyst.

Although the details will be described later, in the pressure-sensitive adhesive tape 1 of the present embodiment, the pressure-sensitive adhesive layer 3 contains epoxidized natural rubber in addition to natural rubber as a rubber component, so that the natural rubber first crosslinks with the isocyanate crosslinking agent. Upon reaction, an appropriate crosslinked structure (three-dimensional network structure having a long distance between crosslinking points) is formed. Further, the epoxidized natural rubber also 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 by combining both of these effects.
Thereby, for example, the cohesive force of the pressure-sensitive adhesive layer 3 is increased as compared with the case where the pressure-sensitive adhesive layer 3 does not contain epoxidized natural rubber as a rubber component. Then, for example, when the adhesive tape 1 is peeled off after the adhesive tape 1 is attached to the adherend, the adhesive residue on the adherend can be reduced.

In particular, when the pressure-sensitive adhesive layer 3 does not contain a crosslinking accelerator composed of a metal catalyst, the cohesive force of the epoxidized natural rubber is remarkably improved. That is, when the pressure-sensitive adhesive layer 3 does not contain a crosslinking accelerator composed of a metal catalyst, unless the pressure-sensitive adhesive layer 3 contains epoxidized natural rubber as a rubber component, its cohesive force is often insufficient. When the pressure-sensitive adhesive layer 3 contains epoxidized natural rubber as a rubber component, its cohesive force is sufficient for using the pressure-sensitive adhesive tape 1 for the purpose of the present invention even if it does not contain a crosslinking accelerator composed of a metal catalyst. It can be anything.
In the present 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. The phenomenon that the agent remains.

(Natural rubber)
Natural rubber is a substance whose main component is 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 near 300,000 and around 2,000,000. In addition, 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 a protein end (an amino group which is a functional group having active hydrogen in one molecule). And an amino acid having a carboxyl group polymerized at a low molecular weight level: a short-chain polypeptide), a phospholipid is bound to the other end (stop end), and a long-chain fatty acid is further attached to this phospholipid end. It is said to have an ester-bonded structure. Furthermore, it is said that functional groups having active hydrogen, such as hydroxyl groups and carboxyl groups, may be introduced into the molecular chain of natural rubber in the process of producing natural rubber, although in small amounts.
Although the details are not clear, any of these functional groups having active hydrogen reacts with the isocyanate group of the isocyanate-based crosslinking agent or the epoxy group of the epoxidized natural rubber to form an appropriate crosslinked structure, as described above. It is possible to

By the way, a natural rubber is 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 cis-1,4-isoprene unit bound to a phospholipid (stop terminal) as a basic skeleton. That is, the protein ends (start ends) of a plurality of natural rubber molecules interact with and bind to the protein contained as a non-rubber component, and the other phospholipid end (stop end) of natural rubber is It is considered that the phospholipid terminals of a plurality of natural rubbers have a branched structure in which the phospholipid terminals interact with each other in a domain shape to be bonded. Since cis-polyisoprene of natural rubber is hydrophobic and non-rubber components such as proteins and lipids are hydrophilic, a phase separation structure composed of cis-polyisoprene and non-rubber components is formed in natural rubber. It is considered to have been done.
It is presumed that a part of the natural rubber having these branched structures further forms an appropriate crosslinked structure by the above-mentioned isocyanate crosslinking agent.

The natural rubber is not particularly limited, and examples thereof include TSR (Technically Specified Rubber) such as SMR (Standard Malaysian Rubber), SIR (Standard Indonesian Rubber), and STR (Standard Thai Rubber), and high-purity natural rubber (HPNR: High- Purity Natural Rubber) etc. are used.

(Epoxidized natural rubber)
The epoxidized natural rubber is one in which a part of the double bond of the above-mentioned natural rubber is substituted with an epoxy group.
As the epoxidized natural rubber, commercially available epoxidized natural rubber may be used, or the above-mentioned natural rubber may be epoxidized and used. The method for epoxidizing natural rubber is not particularly limited, and examples thereof include a chlorhydrin method, a direct oxidation method, a hydrogen peroxide method, an alkylhydroperoxide method, and a peracid method. Examples of the peracid method include a method of reacting natural rubber with an organic peracid such as peracetic acid or formic 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 is, the more preferable it is. Since the epoxy group of the epoxidized natural rubber exists in the molecular skeleton, it is slightly inferior in reactivity to the epoxy group having a high degree of freedom at the end of the molecular chain. Therefore, the amount of epoxy groups in the epoxidized natural rubber is increased, and the chance of contact 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 that
In addition, the maximum value of the epoxidation rate of epoxidized natural rubber that is generally available is about 50 mol %.

Here, the epoxidation rate of epoxidized natural rubber means the 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 obtained, for example, from the measurement data obtained by dissolving the epoxidized natural rubber in deuterated chloroform and measuring its nuclear magnetic resonance (NMR) spectroscopy. 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 glass transition temperature of epoxidized natural rubber rises by about 1° C. every time the epoxidation rate increases by 1 mol %. When the glass transition temperature of the natural rubber is about -70°C, the glass transition temperatures of the epoxidized natural rubber having the epoxidation rates of 25 mol% and 50 mol% are about -45°C and about -20°C, respectively. Therefore, the larger the epoxidation rate and the added amount of the epoxidized natural rubber, the higher the glass transition temperature of the pressure-sensitive adhesive layer 3, and the harder the pressure-sensitive adhesive layer 3 tends to be.

In the present embodiment, the epoxidation rate of the epoxidized natural rubber is 25 mol% or more, so that the adhesive layer 3 has an epoxy group contained in the epoxidized natural rubber and an active hydrogen contained in the natural rubber. Since the probability of contact with the functional group increases, the above-mentioned auxiliary crosslinking reaction easily proceeds. As a result, the cohesive force of the pressure-sensitive adhesive layer 3 is increased as compared with the case where the epoxidized rate of the epoxidized natural rubber is less than 25 mol %. Then, for example, when the adhesive tape 1 is peeled off after the adhesive tape 1 is attached to the adherend, the adhesive residue on the adherend can be reduced.

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 by weight ratio. By setting the ratio of the natural rubber and the 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 high, 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 very good. Therefore, if 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) consisting of approximately spherical particles of micron size. It is considered to form a structure. Therefore, it is speculated that the above-mentioned auxiliary crosslinking reaction involving the epoxy group of the epoxidized natural rubber mainly occurs at the interface of this sea-island structure.
Further, as described above, the natural rubber has a phase-separated structure composed of the hydrophobic cis-polyisoprene and the 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 of the natural rubber.

Furthermore, as described above, since the epoxidized natural rubber has a higher glass transition temperature than the natural rubber, when the natural rubber and the epoxidized natural rubber are mixed, the phase of the relatively soft natural rubber becomes: The slightly harder epoxidized natural rubber phase becomes dispersed with some covalent bonds at the phase interface. Then, the phase (island) of the epoxidized natural rubber 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 plays a role as a kind of reinforcing filler in the natural rubber. However, it may also function as a stopper that suppresses the breakage of the polymer. It is presumed that this effect also contributes to the improvement of the cohesive force of the pressure-sensitive adhesive layer 3.
Even if it is assumed that a covalent bond due to cross-linking is hardly formed at the interface of the sea-island structure between the natural rubber and the epoxidized natural rubber, the phase (island) of the epoxidized natural rubber or the epoxidized natural rubber and the natural rubber The pseudo phase (island) close to the non-rubber component is a rather hard 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 (island) of the epoxidized natural rubber 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, even if it is pseudo, plays the role of the reinforcing filler or the pseudo crosslinking. It is assumed to have the role of dots.

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 promoting the crosslinking by the epoxy group, and therefore the crosslinking may vary depending on the lot of the natural rubber. is there. In this case, since the cohesive force of the pressure-sensitive adhesive layer 3 decreases, 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 adhesive residue may be left on the adherend.
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 promoting 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 rises, so that the ball tack of the pressure-sensitive adhesive layer 3 may decrease.

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

The isocyanate compound is not particularly limited, but it is preferable to use a polyfunctional isocyanate compound containing at least two isocyanate groups in the molecule. As the polyfunctional isocyanate compound, for example, tolylene diisocyanate, diphenylmethane diisocyanate, water-added diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, or the like, or polyisocyanate obtained by the reaction of these diisocyanates and triol, for example, , An adduct of tolylene diisocyanate and trimethylol propane, an adduct of hexamethylene diisocyanate and trimethylol propane, or a trimer of tolylene diisocyanate derived from these diisocyanates, a trimer of hexamethylene diisocyanate, biuret modified hexa Examples thereof include methylene diisocyanate and carbodiimide-modified diphenylmethane diisocyanate.

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, in the pressure-sensitive adhesive layer 3, the cross-linking of the natural rubber and the epoxidized natural rubber is further promoted as compared with the case where, for example, an isocyanurate-type polyisocyanate is used. It becomes possible. As a result, the cohesive force of the pressure-sensitive adhesive layer 3 increases and, for example, when the pressure-sensitive adhesive tape 1 is peeled off after the pressure-sensitive adhesive tape 1 is attached to the adherend, it is possible to reduce adhesive residue on the adherend.

Further, in the present embodiment, it is preferable to use a polyfunctional isocyanate cross-linking agent containing a polyisocyanate compound obtained by the reaction of diisocyanate and triol among the above-mentioned isocyanate compounds.
By using such an isocyanate crosslinking agent, it becomes possible to crosslink the above-mentioned isoprene rubber in a mesh shape. As a result, the cohesive force of the pressure-sensitive adhesive layer 3 can be further increased, and when the adhesive tape is attached to the adherend and then peeled off, the adhesive residue on the adherend can be further reduced. become.

As the isocyanate-based crosslinking agent, one of the above-mentioned isocyanate compounds may be used alone, or two or more thereof may be used in combination.
As the isocyanate cross-linking agent containing the above-mentioned isocyanate compound, for example, Coronate L (trade name) manufactured by Tosoh Corporation or Coronate HL (trade name) manufactured by Tosoh Corporation can be used.

In the pressure-sensitive adhesive layer 3 of the present embodiment, the content of the isocyanate crosslinking agent with respect to the rubber component (natural rubber, epoxidized natural rubber) is 6 parts by weight or more and 15 parts by weight or less based on 100 parts by weight of the rubber component. It is preferably in the range.
When the content of the isocyanate crosslinking agent is less than 6 parts by weight based on 100 parts by weight of the rubber component, when any functional group having active hydrogen contained in the natural rubber or the epoxy group of the epoxidized natural rubber is ring-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, adhesive residue on the adherend may occur.
On the other hand, when the content of the isocyanate cross-linking agent with respect to 100 parts by weight of the rubber component exceeds 15 parts by weight, the initial adhesive strength of the 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 The force improves with time, and as a result, when the adhesive tape 1 is peeled off, adhesive residue on the adherend may occur.

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

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

(Anti-aging agent)
The antiaging agent is added as needed for the purpose of suppressing deterioration of the pressure-sensitive adhesive layer 3. The anti-aging agent is not particularly limited, but, for example, phenol-based, amine-based, benzimidazole-based anti-aging agents and the like can be used.

Examples of the phenol-based antiaging 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-t-butyl-3-methylphenol), 4,4-butylidenebis-(3-methyl-6-t-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)propionate]methane, 2-t -Butyl-6-(3-t-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenyl acrylate, n-octadecyl-3-(4-hydroxy-3,5-di-t-butylphenyl) Examples include propionate.

Examples of amine-based antiaging agents 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-toluenesulfonylamide)diphenylamine, N-(3-methacryloyloxy-2-hydroxypropyl )-N-phenyl-p-phenylenediamine and the like.
Furthermore, examples of the benzimidazole antiaging agent include 2-mercaptobenzimidazole and 2-mercaptomethylbenzimidazole.
The antioxidant is not particularly limited to these.

(Colorant)
The colorant is added as necessary for the purpose of coloring the pressure-sensitive adhesive layer 3.
The colorant is not particularly limited, and any colorant can be used. For example, diarylide colorant, condensed azo colorant, quinacridone colorant, vat colorant, isoindolinone colorant, phthalocyanine colorant, aniline colorant, titanium oxide, nickel titanium, yellow iron oxide, Rouge, ultramarine blue, cobalt blue, chromium oxide, iron black, yellow lead, chrome orange, molybdenum red, cadmium colorant, carbon black, etc., preferably titanium oxide or copper phthalocyanine as a phthalocyanine colorant, nickel. Phthalocyanine, cobalt phthalocyanine or the like can be used.

(solvent)
The pressure-sensitive adhesive layer 3 of the present embodiment is usually formed of a pressure-sensitive adhesive composition prepared by dissolving natural rubber, epoxidized natural rubber, an isocyanate cross-linking agent and the like in a solvent.
Examples of the solvent used for preparing 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 a mixed solvent thereof.

[Base material]
The base material 2 used for the adhesive tape 1 of the present embodiment is not particularly limited, and for example, a base material made of plastic, metal, paper, cloth or the like can be used. Among these, it is preferable to use a plastic base material made of polyethylene terephthalate, polypropylene or the like.

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 peelability improving treatment. As a treating agent used on the surface of the base material 2, a silicone resin, a long-chain alkyl vinyl monomer polymer, a fluoroalkyl vinyl monomer polymer, polyvinyl alcohol carbamate, etc. are known. Among these, it is preferable to use a silicone resin because it has excellent properties for improving the peeling performance of 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.
In producing the pressure-sensitive adhesive tape 1, first, a solvent such as toluene is mixed with additives such as natural rubber, epoxidized natural rubber, a tackifier and, if necessary, an antiaging agent, and then this mixed solution is added. An isocyanate cross-linking agent is added to prepare a pressure-sensitive adhesive composition.
Then, the pressure-sensitive adhesive composition is applied to one surface of the base material 2 using a coater or the like so that the thickness of the pressure-sensitive adhesive layer 3 after drying becomes uniform. Then, the applied pressure-sensitive adhesive composition is dried and cured at a predetermined temperature to obtain the pressure-sensitive adhesive tape 1 in which the pressure-sensitive adhesive layer 3 is laminated on the base material 2.
In addition, as described above, the surface treatment may be performed on the base material 2, or the anchor agent layer may be formed between the base material 2 and the 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 which is used for temporarily fixing devices such as electric devices and storage boxes. For example, when transporting or assembling an electric device such as a refrigerator or a washing machine, parts are attached and fixed to the main body of the electric device with the adhesive tape 1. Then, when transportation or assembly of the electric device is completed and fixing is no longer necessary, the attached adhesive tape 1 is peeled off from the electric device or parts thereof.

Here, as described above, the pressure-sensitive adhesive layer 3 of the present embodiment contains the natural rubber, the epoxidized natural rubber, and the isocyanate cross-linking 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 adhered to the adherend.
More specifically, since 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 the natural rubber or the epoxidized natural rubber is added. The hydroxyl group formed when the epoxy group is ring-opened undergoes a cross-linking reaction with the isocyanate cross-linking agent to form an appropriate cross-linking structure (three-dimensional network structure having a long distance between cross-linking points). Furthermore, the epoxidized natural rubber acts as an auxiliary or pseudo-crosslinking point. It is presumed that the cohesive force of the pressure-sensitive adhesive layer 3 is improved by combining these two effects.
Thereby, for example, the cohesive force of the pressure-sensitive adhesive layer 3 is increased as compared with the case where the pressure-sensitive adhesive layer 3 does not contain epoxidized natural rubber as a rubber component. Then, for example, when the adhesive tape 1 is peeled off after the adhesive tape 1 is attached to the adherend, the adhesive residue on the adherend can be reduced.

By the way, in an adhesive tape for temporary fixing used for temporary fixing of devices such as electric devices and storage boxes, in order to reduce adhesive residue on the adherend after peeling from the adherend, cross-linking of the adhesive layer is performed. It is necessary to proceed to 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 promoting a crosslinking reaction between the natural rubber or the like and the crosslinking agent in the adhesive layer.
However, when a cross-linking 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, In some cases, a sticking mark (not an adhesive residue but visually observable cloudiness on the adherend surface) may remain on the adherend. In particular, when a crosslinking accelerator composed of a metal catalyst is added to the pressure-sensitive adhesive layer and a release agent composed of a silicone resin is applied to the surface of the substrate (the surface opposite to the pressure-sensitive adhesive layer), the adherend The sticking marks are likely to remain. This is because the release agent on the surface of the base material reacts with the metal catalyst contained in the pressure-sensitive adhesive layer when the pressure-sensitive adhesive tape is wound, and the generated by-product partially transfers to the pressure-sensitive adhesive layer 3. It is presumed to be derived.

On the other hand, in the present embodiment, since the adhesive layer 3 does not use a crosslinking accelerator composed of a metal catalyst, when the adhesive tape 1 is attached to an adherend and then peeled off, the adherend is not adhered to the adherend. It is possible to suppress the occurrence of sticking marks. In addition, as described above, the pressure-sensitive adhesive layer 3 contains the natural rubber and the epoxidized natural rubber as the rubber component and the isocyanate cross-linking agent as the cross-linking agent. Even when not using, the crosslinking of the pressure-sensitive adhesive layer 3 can be appropriately advanced, and the cohesive force of the pressure-sensitive adhesive layer 3 can be increased. For this reason, even when the crosslinking accelerator composed of a metal catalyst is not used in the pressure-sensitive adhesive layer 3, the pressure-sensitive adhesive tape 1 is attached to the adherend and then the pressure-sensitive adhesive tape 1 is peeled off from the adherend. Adhesive residue can be reduced.

Next, the present invention will be described more specifically using examples and comparative examples. The present invention is not limited to the examples below.

(Examples 1-10, Comparative Examples 1-3)
1. Preparation of pressure-sensitive adhesive composition A pressure-sensitive adhesive composition was prepared according to the formulations (unit: parts by weight/solid content conversion) shown in Table 1 and Table 2 described later.
First, natural rubber "Thick pale Crape No. 1" (trade name; Nomura Trading Co., Ltd.), epoxidized natural rubber "ENR-50" (trade name, epoxidation rate 50 mol%; MUANG MAI GUTHURIE Co., Ltd.), adhesive The imparting agent "Alcon P-125" (trade name; manufactured by Arakawa Chemical Industry Co., Ltd.) and the antioxidant "Irganox 1010" (trade name; manufactured by BASF Corporation) were dissolved in a solvent (toluene) and stirred for 12 hours. Then, an isocyanate cross-linking 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 a pressure-sensitive adhesive composition. Further, in Examples 8 and 9, as the epoxidized natural rubber, "ENR-25" (trade name, epoxidation rate: 25 mol%; manufactured by MUANG MAI GUTHURIE) was used instead of "ENR-50".
In Comparative Example 1, no epoxidized natural rubber is used in the pressure-sensitive adhesive composition. Further, in Comparative Example 2, no isocyanate cross-linking agent was used in the pressure-sensitive adhesive composition. Further, in Comparative Example 3, epoxidized natural rubber was not used in the pressure-sensitive adhesive composition, and dibutyltin dilaurate was added as a crosslinking accelerator.

2. Preparation of Adhesive Tape Subsequently, the adhesive composition prepared by the above-mentioned production method was applied to the base material 2 to prepare the adhesive tape 1.
Specifically, after forming an anchor agent layer on the surface of the substrate 2 (polypropylene film; manufactured by Nippon Matai Co., Ltd.), the adhesive composition was applied. Further, the surface of the base material 2 opposite to the surface coated with the pressure-sensitive adhesive composition was subjected to a peeling treatment with a silicone resin. Subsequently, the base material 2 coated with the pressure-sensitive adhesive composition and subjected to the peeling treatment was wound up on a paper tube.
Then, 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 base material 2. In the adhesive tape 1, the thickness of the base material 2 was about 60 μm, and the thickness of the adhesive layer 3 was about 30 μm.

3. Evaluation Method Next, the evaluation method of the adhesive tape 1 will be described.
(1) Measurement of Ball Tack The ball tack of the pressure-sensitive adhesive tape 1 was measured according to the inclined ball tack method described in JIS Z 0237 (2009).
Specifically, the adhesive tape 1 is fixed to an inclined plate having an inclination angle of 30° so that the adhesive layer 3 is on the upper surface, and the length of the runway is 100 mm. The ball was rolled by the method described in JIS Z 0237 (2009). At this time, a ball having a diameter of 2/32 inch to 1 inch was used. Then, among the balls that stopped on the surface of the pressure-sensitive adhesive layer 3 when the balls rolled, the value of the maximum diameter ball number was specified, and the evaluation results are shown in Tables 1 and 2. The ball number can be obtained by multiplying the diameter of the ball by 32 times. That is, one having a diameter of 1 inch is called a ball number 32, and one having a diameter of 2/32 inch is called a ball number 2. The larger the ball number, the stronger the tack force (initial adhesive force) of the 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 attached to a stainless steel plate (SUS304) having a surface finish BA, and the amount of deviation (mm) was measured when the adhesive tape 1 was held for 24 hours with a predetermined weight attached. In addition, when the adhesive tape 1 was peeled off from the stainless steel plate before 24 hours had elapsed and dropped, the elapsed time (minutes) from the start of measurement until the adhesive tape 1 dropped was measured.
When the adhesive tape 1 is used for temporary fixing of an electric device or the like, the amount of deviation of the adhesive tape 1 in the holding power test is preferably 25 mm or less.

(3) Measurement of Adhesive Strength The adhesive strength of the adhesive tape 1 was measured according to the adhesive strength test described in JIS Z 0237 (2009).
Specifically, the adhesive tape 1 is attached to each of a stainless steel plate (SUS304) having a surface finish BA, a glass plate, an ABS plate (Acrylonitrile, butadiene (Butadiene), and styrene (Styrene) copolymer synthetic resin). , A roller having a mass of 2000 g was reciprocated a total of 2 times at a speed of 10 mm/s for pressure bonding. After that, it was peeled off in the direction of 180° at a speed of 300 mm/min within 1 minute, and the adhesive force was measured.
The adhesive tape 1 used had a width of 19 mm or 25 mm, and the measurement result of the adhesive force was converted into a width of 10 mm (unit: N/10 mm).

(4) Adhesive residue test The adhesive residue test is a test for evaluating the residue of the adhesive or the like on the adherend after the adhesive tape 1 is attached to the adherend and peeled off.
After the pressure-sensitive adhesive tape 1 was attached to the ABS molded product (adherend), it was reciprocated once with a roller having a mass of 2000 g. After this was stored at 60° C. for 2 days and further at 23° C. for 2 days, the adhesive tape 1 was peeled off by hand in the 90° direction at once.
A phenomenon in which the pressure-sensitive adhesive that constitutes the pressure-sensitive adhesive layer 3 of the pressure-sensitive adhesive tape 1 remains on the surface of the pressure-sensitive adhesive body 1 at the portion of the adherend where the pressure-sensitive adhesive tape 1 is attached is referred to as "adhesive residue". It was evaluated by.
The evaluation of the adhesive residue test was performed according to the following criteria.
A: Residual adhesive cannot be confirmed visually and by touch.
B: Adhesive residue occurs in less than 5% of the applied area.
C: Adhesive residue occurs in 5% or more of the applied area.

(5) Edge adhesive residue test The edge adhesive 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 the pressure-sensitive adhesive tape 1 was attached to the ABS molded product (adherend), it was reciprocated once with a roller having a mass of 2000 g. After this was stored at 60° C. for 2 days and further at 23° C. for 2 days, the adhesive tape 1 was peeled off by hand in the 90° direction at once.
The phenomenon that the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 3 of the pressure-sensitive adhesive tape 1 remains on the surface of the pressure-sensitive adhesive tape 1 at the peeling start portion of the pressure-sensitive adhesive tape 1 in the portion of the adherend to which the pressure-sensitive adhesive tape 1 is attached It is called "edge glue residue" and evaluated by visual inspection and palpation.
The edge glue residue test was evaluated according to the following criteria.
A: Residual adhesive cannot be confirmed visually and by touch.
B: The adhesive residue cannot be visually confirmed, but can be slightly confirmed by palpation.
C: Residual adhesive can be confirmed visually and by touch.

(6) Sticking mark test The sticking mark test is a test for evaluating the presence or absence of a sticking mark of the adhesive tape 1 on the adherend after sticking the adhesive tape 1 on the adherend and peeling it off. Here, the sticking mark of the pressure-sensitive adhesive tape 1 means a cloudiness on the surface of the adherend which is visible, although it is not the above-mentioned adhesive residue.
The pressure-sensitive adhesive tape 1 was attached to a glass plate and reciprocated once with a roller having a mass of 200 g to perform pressure bonding. Then, it was taken out after being left for 168 hours in a thermostat having a temperature of 55° C. and a relative humidity of 95%. Then, the adhesive tape 1 was peeled from the adherend at 0° C., and the surface of the adherend was observed.
The evaluation of the sticking trace test was performed according to the following criteria.
A: Nothing is observed in the portion of the adherend to which the adhesive tape 1 is attached.
C: After being fogged, the part of the adherend to which the adhesive tape 1 is attached is observed.

(7) Shearing force test The shearing force test is a test for evaluating the durability of the adhesive tape 1 against a force applied in the shearing direction.
Specifically, the adhesive tape 1 having a width of 25 mm is cut into a length of 150 mm, the end surface 10 mm of the adhesive tape 1 is attached to a stainless steel plate (SUS304) having a surface finish BA, and a total of 2000 g of a roller is applied at a speed of 10 mm/s. It was crimped by reciprocating twice. Subsequently, the stainless steel plate was fixed, the adhesive tape 1 was pulled up in the direction of 90° at a speed of 300 mm/min, and the force when the adhesive tape 1 was peeled from the stainless steel plate was measured. The measurement result of the shearing force was converted into 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 Tables 1 and 2 below.

As shown in Table 1 and Table 2, in Examples 1 to 7, 9, 10, and 12 in which the pressure-sensitive adhesive layer 3 contains natural rubber, epoxidized natural rubber, and isocyanate cross-linking agent, the pressure-sensitive adhesive tape 1 was adhered. It was confirmed that, when the adhesive tape 1 was peeled off after being adhered to, no adhesive residue, edge adhesive residue, or sticking trace was produced on the adherend.

However, in Example 6, the content ratio of the natural rubber and the epoxidized natural rubber (natural rubber/epoxidized natural rubber) was 68/32 by weight, and the content of the epoxidized natural rubber was large. Evaluation of ball tack (initial tack feeling) as compared with Examples 1 to 5 in which the content ratio of (meth) 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.
Further, in Example 8, since the content of the isocyanate-based cross-linking agent was as small as 5 parts by weight, as compared with Examples 2, 7, and 12 in which the content of the isocyanate-based cross-linking agent was 6 to 15 parts by weight, the tackiness was increased. It was confirmed that when the adhesive tape 1 was peeled off after the tape 1 was attached to the adherend, the evaluation of the edge glue residue on the adherend was slightly inferior.
Further, in Example 11, since the content of the isocyanate-based cross-linking agent was as high as 20 parts by weight, compared with Examples 2, 7, and 12 in which the content of the isocyanate-based cross-linking agent was 6 to 15 parts by weight, the adhesion was high. It was confirmed that the adhesive residue was slightly inferior to the adherend 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 and epoxidized natural rubber (natural rubber/epoxidized natural rubber) was 99.5/0.5 by weight, and the addition amount of epoxidized natural rubber was Due to the small amount, the adhesive tape 1 was covered with the adhesive tape 1 as compared with Examples 1 to 5 in which the content ratio of natural rubber and epoxidized natural rubber (natural rubber/epoxidized natural rubber) was in the range of 99/1 to 70/30. It was confirmed that when the pressure-sensitive adhesive tape 1 was peeled off after being attached to the adherend, the evaluation of the edge glue residue on the adherend was slightly inferior.

On the other hand, in Comparative Example 1 in which the pressure-sensitive adhesive layer 3 does not contain epoxidized natural rubber, when the pressure-sensitive adhesive tape 1 is peeled off after the pressure-sensitive adhesive tape 1 is adhered to the adherend, the edge paste remains on the adherend. Was observed.
In Comparative Example 2 in which the pressure-sensitive adhesive layer 3 did not contain an isocyanate crosslinking agent, the holding force 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 measuring the holding force. 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 the epoxidized natural rubber but contains the crosslinking accelerator, when the pressure-sensitive adhesive tape 1 is peeled off after the pressure-sensitive adhesive tape 1 is attached to the adherend. Marks of sticking were observed on the body. Also, a slight amount of adhesive residue on the adherend was observed.

1... Adhesive tape, 2... Base material, 3... Adhesive layer

Claims (4)

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, a natural rubber, see contains an epoxidized natural rubber and an isocyanate crosslinking agent, the natural rubber and the content ratio of the epoxidized natural rubber (a natural rubber / epoxidized natural rubber), by weight ratio, The pressure-sensitive adhesive tape is characterized in that it is in the range of 99.5/0.5 to 70/30 and does not contain a crosslinking accelerator composed of a metal catalyst . The pressure-sensitive adhesive layer is characterized in that the content ratio of natural rubber and epoxidized natural rubber (natural rubber/epoxidized natural rubber) is in the range of 99/1 to 70/30 by weight. 1. The adhesive tape according to 1. The adhesive tape according to claim 1 or 2, wherein the epoxidized natural rubber contained in the adhesive layer has an epoxidation rate of 25 mol% or more. The pressure-sensitive adhesive layer is characterized in that the content of the isocyanate cross-linking agent is in the range of 6 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of a rubber component containing natural rubber and epoxidized natural rubber. The pressure-sensitive adhesive tape according to any one of claims 1 to 3.

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