JP7072735B1 - Adhesive composition and adhesive tape - Google Patents

Abstract

Natural rubber to provide a rubber-based adhesive composition having excellent adhesive strength, high-temperature retention, and removability to various adherends including metals, resins, and coating materials, and adhesive tapes using the same. It is a pressure-sensitive adhesive composition containing a cross-linking agent, a pressure-sensitive adhesive and a cross-linking adjusting agent, and the minimum temperature of the loss tangent after curing of the pressure-sensitive adhesive composition is 78.7 ° C. or higher and the minimum value is 0.20 or lower. Using an adhesive composition characterized in that the maximum temperature of the loss tangent is 25.0 ° C. or lower and the maximum value is 1.15 or less, the pressure-sensitive adhesive layer 12 is applied to at least one surface of the sheet-shaped substrate 11. The formed adhesive tape.

Description

The present invention relates to an adhesive composition using natural rubber as a main component, which has a high degree of cross-linking and excellent cohesiveness and self-adhesive surface adhesiveness, and various adherends including metals, resins and coating materials. The present invention relates to an adhesive composition having excellent adhesive strength, high temperature retention and removability.
Further, the present invention uses the above-mentioned adhesive composition, has a strong fixing force required in the manufacturing / assembling stage and the transportation stage of an article, and when re-peeled, the adherend is less contaminated and is easily peeled off. Regarding adhesive tape suitable for.

Adhesive tape on articles for the purpose of masking, reinforcement, protection, identification during manufacturing and assembly, damage prevention during transportation after manufacturing, and packaging assistance in industrial products such as information equipment, office equipment, home appliances, and interiors. Is directly pasted and peeled off after achieving the purpose. Therefore, such an adhesive tape for temporary fixing has excellent fixing force to the adherend (adhesive force, high temperature retention) and contamination of the adherend when peeled (also referred to as re-peeling). Performance that contradicts the small amount (removability) is required.
Further, in order to make it easier to peel off the tape and further improve the re-peelability, it is required that the end of the tape can be held in a folded state toward the glue surface side as a handle when the tape is re-peeled (self-adhesive surface adhesiveness). ..

Examples of the adhesive suitable for the temporary fixing adhesive tape used for such a purpose include acrylic and rubber adhesives from the viewpoint of performance and price.

Patent Document 1 describes a pressure-sensitive adhesive layer obtained by curing an isoprene-based rubber and a pressure-sensitive adhesive with a curing agent in the presence of a zirconium compound. In Patent Document 2, an undercoating agent layer composed of a rubber component made of natural rubber polymerized with methyl methacrylate, an isocyanate compound and an aminoethylated acrylic resin is provided between the rubber-based pressure-sensitive adhesive layer and the base material. Is described. Patent Document 3 describes pressure-sensitive adhesive sheets provided with a layer made of a solid-type pressure-sensitive adhesive composition obtained by adding a pressure-sensitive adhesive to a rubbery polymer and cross-linking it with an isocyanate-based cross-linking agent.

Japanese Unexamined Patent Publication No. 2014-034582 Japanese Unexamined Patent Publication No. 2014-240484 Japanese Unexamined Patent Publication No. 2001-181596

In Patent Document 1, it is said that the cohesive force of the pressure-sensitive adhesive is enhanced by using an organic zirconium compound as a zirconium compound and curing with an isocyanate-based curing agent as a curing agent. Since the fraction is low (17 to 30%) and the measurement conditions are lenient, it is expected that the high temperature holding power and the adhesive residue property as intended by the present invention are inferior.

In Patent Document 2, as a preferred embodiment, the pressure-sensitive adhesive layer includes an elastomer containing 50 to 80 parts by weight of natural rubber and 20 to 45 parts by weight of isoprene rubber having a peroxide in the molecule, and 50 to 100 parts by weight of a tackifier resin. And, it contains 0.1 to 15 parts by weight of the cross-linking agent, and when combined with the above-mentioned specific undercoating agent layer, it has a strong adhesive force, and adhesive residue on the adherend when the tape is peeled off, etc. It is said that the contamination of rubber is significantly suppressed. In addition, by adding liquid isoprene rubber having peroxide in the molecule, sulfur and peroxide normally used for natural rubber cross-linking (vulcanization) are not used, curing at 120 ° C or higher is not required, and storage at room temperature and humidity is not required. It is said that cross-linking in the environment will be possible. Further, although it is described that an epoxy resin, an isocyanate resin or the like is used as the cross-linking agent, it is preferably an epoxy resin (paragraph 0023). In the examples, although the isocyanate compound is used for the undercoat layer, the cross-linking agent of the pressure-sensitive adhesive layer is epoxy-based, and the pressure-sensitive adhesive layer is not only pure natural rubber but also a liquid having a peroxide in the molecule. Cross-linked using isoprene rubber. Since the pass / fail of the gel fraction is set as low as 20% and the pass / fail of the holding force measurement conditions is also low, it cannot be said that the holding force is sufficient as the object of the present invention.

The pressure-sensitive adhesive composition of Patent Document 3 is a solid type composition that is solvent-free, is a rubbery polymer made of natural rubber, a pressure-sensitive adhesive and an isocyanate-based cross-linking agent are added, and the mixture is heated and kneaded at 80 to 120 ° C. and simultaneously cross-linked. It is a thing. By devising a heat kneading method, it is possible to realize extremely weak and moderate cross-linking even with a solid type using an isocyanate-based cross-linking agent, increase the cohesive force while maintaining the adhesive strength, and low molecular weight even with the addition of a small amount of cross-linking agent. It is said that it has become possible to disperse evenly without causing conversion. However, in Patent Document 3, an adhesive force test by peeling at 23 ° C. and a holding force test by a 2 kg load at 40 ° C. are carried out, but the characteristics at a higher temperature have not been evaluated.

Also, in the past, tapes for temporary fixing of articles using acrylic adhesives and acrylic adhesives with excellent fixing power and cohesive force have been studied, but acrylic adhesives have self-adhesive surface adhesion. The properties are insufficient, and the adhesive strength to metal and glass is high, so there is a concern that the adherend may be contaminated during re-peeling.

An object of the present invention is to provide a rubber-based pressure-sensitive adhesive composition having excellent adhesive strength, high-temperature retention, and low contamination resistance to various adherends such as metals, resins, and coating materials.

Further, the present invention uses a rubber-based adhesive, and even if it is exposed to a high temperature or high temperature and high humidity environment in the manufacturing / assembling stage or the transportation stage of an article, the adherend is less contaminated after re-peeling, and the tape is re-peeled. As a handle for the time, the end of the tape can be held folded back to the glue surface side, so it is easy to peel off, and because it has excellent adhesive strength, it is possible to temporarily fix the article even with a narrow width. It is an object of the present invention to provide an adhesive tape for fixing.

The pressure-sensitive adhesive composition according to one aspect of the present invention is a pressure-sensitive adhesive composition containing a natural rubber, a cross-linking agent, a tackifier and a cross-linking adjuster, and as the cross-linking agent, an isocyanate-based compound having a diphenylmethane diisocyanate structure is used as the natural rubber. 2.5 to 10 parts by mass with respect to 100 parts by mass, and 60 to 90 parts by mass of a petroleum-based tackifier having a softening point of 125 ° C. or higher as the binder-imparting agent with respect to 100 parts by mass of natural rubber. The minimum temperature of the loss tangent after curing of the composition is 78.7 ° C. or higher and the minimum value is 0.20 or less, and the maximum temperature of the loss tangent is 25.0 ° C. or lower and the maximum value is 1.15 or less. It is an adhesive composition characterized by being present.

Further, the pressure-sensitive adhesive tape according to another aspect of the present invention is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer made of the above-mentioned pressure-sensitive adhesive composition on at least one surface of a sheet-like base material.

According to one aspect of the present invention, a rubber-based pressure-sensitive adhesive composition having excellent adhesive strength, high-temperature retention, and removability (low stain resistance) to various adherends including metals, resins, and coating materials. Is provided.

Further, according to another aspect of the present invention, it has a strong fixing force required in the manufacturing / assembling stage and the transportation stage of an article, and when it is peeled off again, the adherend is less contaminated and is easily peeled off for temporary fixing. Adhesive tape suitable for is provided.

It is a figure which showed the structural example of the adhesive tape to which the embodiment for carrying out an invention is applied. It is a figure which showed the other structural example of the adhesive tape to which the embodiment for carrying out an invention is applied.

The pressure-sensitive adhesive composition according to an embodiment of the present invention will be described.
The pressure-sensitive adhesive composition according to the present embodiment is a pressure-sensitive adhesive composition containing natural rubber, a cross-linking agent, a pressure-sensitive adhesive and a cross-linking adjusting agent, and the minimum temperature of the loss tangent after curing of the pressure-sensitive adhesive composition is 78.7 ° C. or higher. It is characterized in that the minimum value is 0.20 or less, the maximum temperature of the loss tangent is 25.0 ° C. or less, and the maximum value is 1.15 or less.

<Loss tangent>
The loss tangent (loss elastic modulus (G ") / storage elastic modulus (G') = loss tangent (tan δ)) means the degree of contribution of the loss elastic modulus (viscosity) to the storage elastic modulus (elasticity).
When the minimum temperature of the loss tangent after curing of the present adhesive composition is 78.7 ° C. or higher, the minimum value of the degree of contribution of the loss elastic modulus (viscosity) is small, and the cured product made of the present adhesive composition is predetermined. It is shown that the temperature having the hardness is high, that is, the pressure-sensitive adhesive layer made of the present pressure-sensitive adhesive composition maintains an appropriate hardness even at a relatively high temperature. If the minimum temperature of the loss tangent is less than 78.7 ° C, the holding power at high temperature is inferior.
Further, the minimum value of the loss tangent after curing of the present pressure-sensitive adhesive composition is 0.20 or less, which indicates that the cured product (adhesive layer) of the present pressure-sensitive adhesive composition is difficult to become excessively soft and difficult to flow. ..

Further, the maximum temperature of the loss tangent indicates the glass transition temperature, and the maximum temperature of the loss tangent of the present adhesive composition is 25.0 ° C. or less because the glass transition temperature of the cured product of the present adhesive composition is low and the temperature is low. But it shows that it keeps moderate flexibility.
Further, the maximum value of the loss tangent indicates the peeling resistance, and the maximum value of the loss tangent of the cured product of the present adhesive composition is 1.15 or less, the peeling resistance when used as the pressure-sensitive adhesive layer is small, and the present adhesive composition. Indicates that the adhesive tape made of an object is easy to peel off.

Each component will be described.
<Natural rubber>
Natural rubber is obtained by coagulating and drying natural rubber latex, which is the sap of rubber trees, and is a substance containing cis-1,4-polyisoprene as a main component.
As for the structure of the natural rubber molecule, one end of the cis-1,4-isoprene unit is composed of a protein end, a phosphate lipid is bound to the other end, and a long-chain fatty acid is further attached to this phosphate lipid end. It is said to be a combined structure.
In addition, natural rubber contains 3 to 4% by mass of non-rubber components such as proteins and lipids.
Therefore, the natural rubber can be easily crosslinked and cured by a crosslinking agent described later. Since the pressure-sensitive adhesive composition according to the present invention is crosslinked and cured, the crosslinked body is also referred to as a cured product.

Examples of the classification of natural rubber used include Standard Marysian Rubber (SMR), Standard Indian Rubber (SIR), Ribbed Smoked Sheet (RSS) 1 to 6, and Pale Crepe 1-3.

Further, in general, unkneaded natural rubber has a very high molecular weight, and if the molecular weight of the natural rubber is too high, the plasticity is high and the adhesive composition lacks flexibility, and appropriate adhesive properties may be obtained. It may not be possible.
Therefore, it is necessary to mechanically knead the natural rubber with a pressure kneader, a Banbury mixer, an open roll, etc. in advance to appropriately reduce the molecular weight of the natural rubber to adjust the plasticity and use it for compounding.

In particular, the plasticity of the natural rubber used in the pressure-sensitive adhesive composition of the present invention is preferably Mooney viscosity ML _{1 + 4} (100 ° C.), preferably 10 to 85, and more preferably 20 to 35. If the degree of plasticity is too low or too high, it may not be possible to obtain an adhesive composition and an adhesive tape that have both excellent adhesive strength and high cohesive strength required for temporary fixing of articles.

<Crosslinking agent>
As a method for cross-linking natural rubber, a method of performing a vulcanization treatment using a vulcanizing agent and a method of cross-linking by a reaction between functional groups are known.
In the vulcanization method, sulfur-based, thiuram-based, quinoid-based and other vulcanizing agents act on the unsaturated bonds contained in the molecular main chain of natural rubber to directly crosslink the polymers. A dense and strong crosslink with a large cohesive force can be realized.

However, since it is a direct and strong cross-linking mechanism, the tackiness sharply decreases as the degree of vulcanization increases, and the adhesive strength also significantly decreases. In addition, sulfur is known as a component that may cause metal corrosion, and is not preferable for temporary fixing applications that are directly attached to various adherends such as metals, resins, and coating materials.

On the other hand, in the cross-linking method based on the reaction between functional groups, about 3 to 4% by mass is mixed with functional groups such as hydroxyl groups and carboxyl groups that may be introduced into the molecular side chain in the process of manufacturing natural rubber, and natural rubber. A polyfunctional compound having a functional group that reacts with a functional group of a non-rubber component such as a protein or a lipid is added, and cross-linking is performed by a reaction between the functional groups.

In this method, it is known that a cross-linking agent containing, for example, an isocyanate-based compound, an epoxy-based compound, an oxazoline-based compound, an aziridine-based compound, a butylated melamine compound, or the like can be used as the cross-linking agent.

In addition, non-sulfur cross-linking agents that are not vulcanizers do not contain sulfur, which may cause metal corrosion, so they can be used as temporary fixings to be directly attached to various adherends such as metals, resins, and coating materials. More preferred.

If the natural rubber can be crosslinked flexibly and densely, the present inventors have excellent adhesive strength required for temporary fixing of an article, high cohesive strength, and excellent high temperature retention and removability. We thought that we could provide a rubber-based adhesive. Then, in order to achieve this purpose, based on the above-mentioned common general technical knowledge, a trial and error study was conducted on a cross-linking agent characterized by being non-sulfur and capable of viaduct. ..

As a result, the present inventors have a pressure-sensitive adhesive composition having excellent adhesive strength required for temporary fixing of natural rubber by using a cross-linking agent containing an isocyanate-based compound as a main component among the above-mentioned cross-linking agents. It was discovered that it can be cross-linked flexibly and densely as an object.

Furthermore, by using a cross-linking agent containing at least one compound selected from those containing a diphenylmethane diisocyanate structure (polymeric MDI) as a main component among the isocyanate compounds, excellent adhesion to various adherends is achieved. We have discovered that we can provide rubber-based adhesives that have strength, high-temperature retention, and removability.

That is, the cross-linking agent used in the pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet of the present invention contains an isocyanate compound as a main component, and in particular, at least one selected from those containing a diphenylmethane diisocyanate structure as a main component. Those containing the above compounds can be preferably used.

The cross-linking agent can be used by adding 1 to 15 parts by mass, preferably 2.5 to 10 parts by mass, with respect to 100 parts by mass of natural rubber. By using it in the relevant amount range, each characteristic of the loss tangent can be satisfied.

<Adhesive enhancer>
In the pressure-sensitive adhesive composition of the present embodiment, a pressure-sensitive adhesive resin having good compatibility with natural rubber can be used as the pressure-sensitive adhesive, and in particular, a group consisting of a petroleum-based resin having a softening point of 125 ° C. or higher, a terpene resin, a rosin resin, and other resins. At least one more selected resin can be used. In particular, a petroleum-based resin (saturated aliphatic hydrocarbon resin) having a softening point of 125 ° C. or higher is preferable. Such a tackifier can be used by adding 50 to 100 parts by mass, preferably 60 to 90 parts by mass, with respect to 100 parts by mass of natural rubber.
When a tackifier resin having a softening point lower than 125 ° C. is used as a tackifier, a pressure-sensitive adhesive composition and a pressure-sensitive adhesive tape having excellent adhesive strength, high-temperature retention, and removability required for temporary fixing of articles can be obtained. It may not be possible.
Further, even if the amount of the pressure-sensitive adhesive added is too large or too small, it may not be possible to obtain the pressure-sensitive adhesive composition and the pressure-sensitive adhesive tape having the above physical characteristics.

<Crosslink adjuster>
In the pressure-sensitive adhesive composition of the present embodiment, the degree of crosslinking (gelling degree) of the composition is adjusted by using a crosslinking adjusting agent. This is used for the purpose of realizing a moderately flexible and dense cross-linking reaction within a range in which excellent adhesive force of the adhesive composition and high cohesive force / high temperature holding force can be achieved at the same time. In particular, in the present invention, a compound that inhibits the reaction between the isocyanate compound as a cross-linking agent and the hydroxyl group of natural rubber to some extent is used as the cross-linking regulator.

In the pressure-sensitive adhesive composition of the present embodiment, at least one selected from the group consisting of hindered phenol-based compounds, phosphorus-based compounds, metal-based compounds, benzotriazole-based compounds, triazine-based compounds, hindered amine-based compounds and the like as the cross-linking modifier. Can be used with the addition of seed compounds.
Specific examples of the hindered phenolic compound include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and 2,2'-thiodiethylbis [3-(. 3,5-Di-tert-butyl-4-hydroxyphenyl) propionate], 3- (4'-hydroxy-3', 5'-di-tert-butylphenyl) propionic acid-n-octadecyl, N, N' -(Hexin-1,6-diyl) bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanamide], octyl-3,5-di-tert-butyl-4-hydroxy- Hydromethic acid, 2,4,6-tris (3', 5'-di-tert-butyl-4'-hydroxybenzyl) mecitylene, 2,4-bis (octylthiomethyl) -6-methylphenol, bis [ 3- (3-tert-Butyl-4-hydroxy-5-methylphenyl) propionic acid] [ethylenebis (oxyethylene)], 1,6-hexanediolbis [3- (3,5-di-tert-butyl) -4-Hydroxyphenyl) propionate], 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5-triazine-2,4,6 (1H, 3H) , 5H) -trione, 4-[[4,6-bis (octylthio) -1,3,5-triazine-2-yl] amino] -2,6-di-tert-butylphenol and the like.

Specific examples of the phosphorus compound include tris phosphite (2,4-di-tert-butylphenyl). Specific examples of the metal compound include 3- (3,5-di-tert-butyl-4-hydroxyphenyl) -N'-[3- (3,5-di-tert-butyl-4-hydroxy). Phenyl) propanoyl] propane hydrazide. Specific examples of the benzotriazole compound include 4-methyl-2- (2H-benzotriazole-2-yl) phenol and 2- (2H-benzotriazole-2-yl) -4,6-bis (1). -Methyl-1-phenylethyl) phenol, 2- (5-chloro-2H-benzotriazole-2-yl) -6- (1,1-dimethylethyl) -4-methylphenol, 2,2'-methylenebis [ 6- (2H-benzotriazole-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol], benzotriazolyldodecyl P-cresol can be mentioned. Specific examples of the triazine compound include 2- (4,6-diphenyl-1,3,5-triazine-2-yl) -5- (hexyloxy) phenol. Specific examples of the hindered amine compound include poly [[6-[(1,1,3,3-tetramethylbutyl) amino] -S-triazine-2,4-diyl]-[(2,2). 6,6-Tetramethyl-4-piperidyl) imino] -hexamethylene-[(2,2,6,6-tetramethyl-4-piperidyl) imino], dimethyl 1- (2-hydroxyethyl) succinate-4 -Hydroxy-2,2,6,6-tetramethyl-4-piperidin polycondensate, 2-[[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] -2-butyl Bis propanediate [1,2,2,6,6-pentamethyl-4-piperidinyl], bis sebacate (1,2,2,6,6-pentamethyl-4-piperidyl), 1-methyl sebacate 10- (1,2,2,6,6-pentamethyl-4-piperidyl) and the like. Among them, the preferred cross-linking modifier is at least one compound selected from the group consisting of hindered phenolic compounds.

The amount of the cross-linking adjuster is not particularly set, but if the amount of the cross-linking adjuster added is too large, the natural rubber cannot be crosslinked flexibly and densely, and the excellent adhesive strength required for temporary fixing of articles can be achieved. It may not be possible to obtain an adhesive composition or adhesive tape that has both high cohesiveness and high temperature retention. On the other hand, if the amount is too small, the effect of adding the cross-linking modifier may not be sufficiently exhibited. It is preferably 1.0 part by mass or more, 5.0 parts by mass or less, more preferably 2.0 parts by mass or more and 4.0 parts by mass or less with respect to 100 parts by mass of natural rubber.

<Other additives>
Further, the pressure-sensitive adhesive composition includes, if necessary, an inorganic filler, an organic filler such as a resin, a softener, a plasticizer, a surfactant, a coupling agent, a colorant, and the like, as long as the physical properties are not impaired. One or more of a preservative, a heat stabilizer, a light stabilizer and the like may be further added.
As used herein, the term "adhesive composition" means both a mixture of components before crosslinking and a composition after crosslinking, and the "adhesive layer" in the following adhesive tapes comprises this adhesive composition. , In that case, "adhesive composition" means the composition after cross-linking. In addition, a dried product in which the solvent is dissolved and dispersed in order to form the pressure-sensitive adhesive layer, and the solvent is removed may also be referred to as a "sticky composition".

[Adhesive tape]
Further, the pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape in which a pressure-sensitive adhesive layer made of the above-mentioned pressure-sensitive adhesive composition is formed on at least one surface of a sheet-shaped base material. For example, as shown in FIG. 1, a single-sided adhesive tape having an adhesive layer 12 made of the above-mentioned adhesive composition on one side of the base material 11, or an adhesive provided on both sides of the base material 21 as shown in FIG. It is a double-sided tape using the above-mentioned pressure-sensitive adhesive composition for at least one or both of the layer 22 and the pressure-sensitive adhesive layer 23.

For the pressure-sensitive adhesive layer 12 in FIG. 1 and the pressure-sensitive adhesive layer 22 and / or 23 in FIG. 2, a coating liquid in which the pressure-sensitive adhesive composition is dissolved or dispersed in an appropriate solvent is applied to a sheet-shaped base material 11 or 12 as a roll coater. , It can be formed by coating with a die coater or the like, or by co-extruding the pressure-sensitive adhesive composition with these substrates without using a solvent. Preferably, a coating liquid is prepared by mixing and dissolving a natural rubber, a cross-linking agent, a tackifier, a cross-linking adjuster, and other additives in a solvent such as toluene, and the coating liquid is applied to one side of the base material 11 or the like. Apply to one or both sides of the base material 21 using a coater or the like so that the thickness of the adhesive layer after drying becomes uniform, and then dry and cure the coated adhesive composition at a predetermined temperature. Formed by.

The thickness of the pressure-sensitive adhesive layer after drying and curing is not particularly limited, and exhibits excellent adhesive strength, self-adhesive surface adhesiveness, cohesive strength, and high-temperature retention required for temporary fixing of articles. Anything may be used, but it is usually about 10 to 70 μm, preferably 25 to 50 μm.

Further, the surface (surface 11A) of the sheet-shaped base material 11 facing the pressure-sensitive adhesive layer 12 in FIG. 1 is subjected to surface treatment such as corona discharge treatment, an undercoat layer, or both, if necessary. The adhesiveness of the pressure-sensitive adhesive layer 12 to the base material 11 can be improved by performing the above. Further, when the adhesive tape of this embodiment is wound in a roll shape by providing a release layer as necessary on the surface 11B on the opposite side of the surface 11A of the sheet-shaped base material 11 in FIG. It is possible to prevent the adhesive composition from adhering to the surface 11B of the base material 11 and maintain the ease of rewinding (pulling out).

Further, both sides (21A and 21B) of the sheet-shaped base material 21 in FIG. 2, or one of the surfaces thereof may be subjected to surface treatment such as corona discharge treatment, an undercoat layer may be provided, or both may be performed. By doing so, the adhesion between the pressure-sensitive adhesive layer 22 or the pressure-sensitive adhesive layer 23 and the base material 21 can be improved.

<Sheet-like base material>
The type of the sheet-shaped base material is not particularly limited, and any known sheet-shaped base material such as a commonly used film, foam, woven fabric, knitted fabric, or non-woven material such as paper may be used.
Of these, a resin film base material is preferable, and the resin materials are polyethylene (PE), polypropylene (PP), stretched polypropylene (OPP), polyester, polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polyethylene naphthalate (PEN). ), Polyphenylene sulfide, ethylene-vinyl acetate copolymer (EVA) and the like, and blends thereof. A film made of such a synthetic resin has excellent mechanical strength, does not contaminate the adherend, and is preferable as an adhesive tape for temporary fixing used in the manufacturing / assembling stage and the transportation stage of an article.

Further, the thickness of the sheet-shaped base material can be appropriately selected and used within a range in which the strength required for the adhesive tape can be maintained, but the thickness is preferably 10 to 300 μm, more preferably 10 to 100 μm, and 12 to 75 μm. Is even more preferable. Especially in the case of polyethylene terephthalate (PET) film in the thickness range, it has excellent mechanical strength, exhibits high fixing force, does not cause contamination of adherends, and is used in the manufacturing / assembling stage and transportation stage of articles. It is more preferable as an adhesive tape for temporary fixing.

<Undercoat>
The undercoat agent used for the undercoat layer is not particularly limited, and may be any as long as it exerts its effect. In particular, if the compound has a functional group capable of reacting with the functional group of the compound contained in the pressure-sensitive adhesive layer, the reaction proceeds to the undercoat layer at the time of cross-linking when forming the pressure-sensitive adhesive layer, and the adhesive adheres to the substrate. You can increase your power. The adhesion amount or basis weight of the undercoat layer after drying is usually 0.2 to 2 g / m ² , preferably 0.4 to 1.2 g / m ² .

<Release release agent>
When the pressure-sensitive adhesive layer 12 is formed on one surface 11A of the base material 11 and wound in a roll shape as shown in FIG. 1, the pressure-sensitive adhesive layer comes into contact with the other side surface 11B of the base material 11. .. It is preferable to form the release layer on the surface 11B in order to improve the pullability from the roll. The release treatment agent used for this release layer is not particularly limited, and any release treatment agent may be used as long as it exerts its effect. For example, silicone resins, long-chain alkyl vinyl monomer polymers, fluoroalkyl vinyl monomer polymers, polyvinyl alcohol carbamate and the like are known. Of these, silicone resin has excellent properties of improving the peeling performance of the surface of the base material. The adhered amount or basis weight of the release layer after drying is usually 0.2 to 2 g / m ² , preferably 0.4 to 1.2 g / m ² .

<Release sheet>
In the case of the double-sided adhesive tape as shown in FIG. 2, it is preferable to laminate the release sheet on the outer surface of the adhesive layer in a removable manner from the viewpoint of handleability. Further, when winding in a roll shape, the release sheet can be wound so as to be sandwiched between the pressure-sensitive adhesive layer 22 and the pressure-sensitive adhesive layer 23. Since the release sheet does not require much high strength, a sheet-like material having one or both sides subjected to the above-mentioned release treatment can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.
Further, in the following description, "part" means "part by mass".

The materials used in the examples and comparative examples are as follows. The physical property values of each material are the values in the manufacturer's catalog.
Base material: PET film (thickness 38 μm)
Natural rubber: pale crepe
(Use different grades of Mooney viscosity listed in the table)
Crosslinker:
A Product name "Millionate MR-200",
Made by Tosoh, Polymeric MDI
B Product name "Coronate L-45E",
Tosoh, Modified Polyisocyanate C Product Name "E-5C", Soken Chemical, Epoxy Crosslinker D Product Name "Vulkacit Thiuram / C", LANXESS Co., Ltd.
Thiram-based vulcanizer (tetramethylthiuram disulfide)
Adhesive:
A Product name "Pencel D-135", manufactured by Arakawa Chemical Industry Co., Ltd.
Polymerized rosin ester, softening point 130-140 ° C
B Product name "Arcon P-140", manufactured by Arakawa Chemical Industries, Ltd.
Petroleum resin, softening point 140 ℃ ± 5 ℃
C Product name "Arcon P-100", manufactured by Arakawa Chemical Industry,
Petroleum-based resin, softening point 100 ° C ± 5 ° C
Crosslink adjuster: Product name "Irganox 1010", manufactured by BASF Japan,
(Hindered phenolic compound)

(Examples 1 to 8, Reference Example 1, Comparative Examples 1 to 12)
Adhesive compositions were prepared at the blending ratios shown in Table 1 (Table 1-1 and Table 1-2), dissolved in toluene and mixed to prepare a coating liquid. Mass ratio of undercoating agent (polymethylmethacrylate grafted natural rubber (manufactured by Malaysia Rubber Research Institute, trade name "MG30") and cyclized rubber (brand name "ALPEX CK-450" manufactured by UCB Japan) on one surface of the base material A solid content 5% by mass toluene solution mixed at a ratio of 3: 1) is applied to form an undercoat layer with a basis weight of 0.8 ± 0.4 g / m ² , and then the prepared coating liquid is dried as an adhesive. An adhesive tape having a single-sided pressure-sensitive adhesive layer as shown in FIG. 1 was produced by applying the layer so that the thickness was 32 μm, drying and cross-linking at 110 ° C.

The following evaluation was performed on the obtained adhesive tape.
(Loss tangent)
Each pressure-sensitive adhesive composition was used to prepare a pressure-sensitive adhesive layer (thickness: 2 mm) for measurement.
Then, the pressure-sensitive adhesive layer was punched to a diameter of 10 mm and fixed by sandwiching it with a parallel plate, which was used as a measurement sample.
For this measurement sample, dynamic viscoelasticity measurement was performed under the following conditions using a dynamic viscoelasticity measuring device, and temperature-dependent graphs of loss elastic modulus (G ") and storage elastic modulus (G') were created to create loss elasticity. From the rate (G ") / storage elastic modulus (G') = loss tangent (tan δ), the minimum temperature, the minimum value, the maximum temperature, and the maximum value were obtained. In addition, as an evaluation, the minimum side (minimum temperature is 78.7 ° C. or higher and minimum value is 0.20 or less) and the maximum side (maximum temperature is 25 ° C. or lower and maximum value is 1.15 or less) satisfy the specified range. The case was set as "Y", and the case where the case was not satisfied was set as "N".

Equipment: Made by TA Instruments, trade name "ARESRDA-III"
Frequency: 10.0Hz
Temperature: -60 to 200 ° C
Temperature rise temperature: 10 ° C / min Strain: 0.1%

(Adhesive force)
Adhesive strength was measured using a test method compliant with JIS Z 0237: 2000.
As the adherend, PS (polypropylene), PP (polypropylene), PC (polycarbonate), rough surface PC (one side matted, manufactured by Takiron Sea Eye Co., Ltd., trade name "PCSP K6600"), glass, SUS plate (#) SUS304 plate polished with 280 water-resistant polishing paper until the surface becomes uniform), Al plate, acrylic coated plate (SPCC-SB acrylic coated plate manufactured by Nippon Steel Co., Ltd. (paint: "New Acrozze Crogloss" manufactured by Dainippon Paint Co., Ltd.) Yes ")) was used.

Since the adhesive strength of the adhesive composition in the present embodiment is preferably 2.0 N / 10 mm or more and 8 N / 10 mm or less, for example, the case where the adhesive strength in this range is shown for all the adherends is referred to as " "A", one adherend is out of range, but the one that can maintain this range for other adherends is "B", and one that is out of this range for two or more adherends. Was evaluated as "C".

(High temperature holding power)
At a measurement temperature of 120 ° C., a weight with a load of 500 g was vertically applied to the end of the test piece having a length of 25 mm and a width of 10 mm attached to the SUS plate in the length direction, and the time until the weight fell was evaluated. .. The fall time of 120 minutes or more was determined as "A", the fall time of 60 minutes or more and less than 120 minutes was determined as "B", and the fall time of less than 60 minutes was determined as "C".

(Substrate contamination)
Adhesive tape was attached to each adherend used for measuring the adhesive strength, and after leaving it in a 65 ° C.85% RH atmosphere for 7 days or more, it was left in a 5 ° C atmosphere for 2 hours or more to cool it, and then it was cooled in a 5 ° C atmosphere. The adhesive tape was manually peeled off from the adherend, and the presence or absence of adhesive residue and contamination in the adherend was visually inspected.
"A" when there is no adhesive residue or tape trace / contamination, "B" when there is almost no adhesive residue or tape trace / contamination, and when there is obvious adhesive residue / tape trace / contamination. Was determined to be "C".

(Self-adhesive surface adhesive)
An adhesive tape was attached to the adherend, and the end portion was bent 5 mm toward the adhesive surface side and left in an atmosphere of 65 ° C. and 85% RH for 1 day or more, and then the length of peeling of the bent end portion was visually measured.

(Comprehensive evaluation)
In all evaluations, rank A is included, rank B is 2 or less as "A", rank A is included, rank B is 3 or 4 as "B", rank A is included, and rank B is 5. The case including "C" and rank D was evaluated as "D".

<Evaluation results>
As shown in Tables 1-1 and 1-2, in the examples, the compositions satisfying the loss tangent specified in the present invention were obtained, but in the comparative example, one or both of the minimum side and the maximum side were satisfied. It was not a composition to be used.
Further, as shown in Table 2-1, the adhesive tapes of Examples 1 to 9 were excellent in all of the adhesive strength, the high temperature holding power, the adherend contamination property, and the self-adhesive surface adhesiveness.

On the other hand, in Comparative Examples 1, 2, 7 to 12, as shown in Table 2-2, the adhesive strength was excellent, but the high temperature holding power was inferior. Comparative Examples 3 and 4 were excellent in high temperature holding power, but inferior in adhesive power. Comparative Examples 5 and 6 were inferior in both adhesive strength and high temperature holding power. In addition, all of the comparative examples included the case where the adherend was ranked D in terms of contamination, and the versatility was low.

The adhesive tape of the present invention is a highly versatile adhesive tape as an adhesive tape for temporary fixing, because it has excellent adhesive strength to various adherends (articles) and exhibits low contamination.

11, 21 Base material 12, 22, 23 Adhesive layer

Claims (6)

A pressure-sensitive adhesive composition containing natural rubber, a cross-linking agent, a tackifier , and a cross-linking adjuster. A petroleum-based tackifier having a softening point of 125 ° C. or higher is contained in an amount of 60 to 90 parts by mass with respect to 100 parts by mass of natural rubber as the binder-imparting agent. A pressure-sensitive adhesive composition having a minimum value of 0.20 or less at 78.7 ° C. or higher, and a maximum temperature of 25.0 ° C. or lower and a maximum value of 1.15 or less at the loss tangent. The pressure-sensitive adhesive composition according to claim 1, wherein the natural rubber has a Mooney viscosity ML _{1 + 4} (100 ° C.) of 20 to 85. The pressure-sensitive adhesive composition according to claim 2, wherein the natural rubber has a Mooney viscosity ML _{1 + 4} (100 ° C.) of 20 to 35. Any of claims 1 to 3 , wherein the cross-linking modifier is at least one compound selected from a hindered phenol-based compound, a phosphorus-based compound, a metal-based compound, a benzotriazole-based compound, a triazine-based compound, and a hindered amine-based compound. The adhesive composition according to item 1. The pressure-sensitive adhesive composition according to any one of claims 1 to 4 , wherein the cross-linking adjusting agent is contained in an amount of 1 to 5 parts by mass with respect to 100 parts by mass of the natural rubber. An adhesive tape having an adhesive layer composed of the adhesive composition according to any one of claims 1 to 5 on at least one surface of a sheet-shaped substrate.

Images