WO2022208814A1

WO2022208814A1 - Pressure-sensitive adhesive composition and pressure-sensitive adhesive tape

Info

Publication number: WO2022208814A1
Application number: PCT/JP2021/014048
Authority: WO
Inventors: 靖史土屋; 菖子岡村
Original assignee: 株式会社寺岡製作所
Priority date: 2021-03-31
Filing date: 2021-03-31
Publication date: 2022-10-06
Also published as: CN116348565B; KR102624251B1; TW202305078A; JP7072735B1; JPWO2022208814A1; TWI814280B; CN116348565A; KR20230054488A

Abstract

The purpose of the present invention is to provide: a rubber-based pressure-sensitive adhesive composition having excellent adhesive force, high-temperature holding properties, and removability in application to various adherends including metals, resins, and coating materials; and a pressure-sensitive adhesive tape obtained using the pressure-sensitive adhesive composition. This pressure-sensitive adhesive composition comprises natural rubber, a crosslinking agent, a tackifier, and a crosslinking regulator, and is characterized by coming, through curing, to have loss tangent values which have a minimal value of 0.20 or less at a minimal-value temperature of 78.7°C or higher and a maximal value of 1.15 or less at a maximal-value temperature of 25.0°C or lower. The pressure-sensitive adhesive composition is used to form a pressure-sensitive adhesive layer 12 on at least one surface of a sheet-shaped substrate 11 to obtain the pressure-sensitive adhesive tape.

Description

Adhesive composition and adhesive tape

The present invention relates to an adhesive composition using natural rubber as a main component, which has a high degree of cross-linking, excellent cohesiveness and self-adhesive surface adhesiveness, and can be used for various adherends such as metals, resins, and coating materials. It relates to an adhesive composition having excellent adhesive strength, high temperature retention, and removability against.
In addition, the present invention uses the above-mentioned adhesive composition, has a strong fixing force required in the manufacturing / assembly stage and transportation stage of the article, has little contamination of the adherend when re-peeled, and is easy to peel temporarily fixed. relating to adhesive tapes suitable for

Adhesive tapes are used for masking, reinforcing, protecting, and identifying industrial products such as information equipment, office equipment, home appliances, and interiors during manufacturing and assembly, as well as for preventing damage during transportation after manufacturing and as a packing aid. is directly attached and is torn off after the purpose is achieved. Therefore, such an adhesive tape for temporary fixing has excellent fixing power (adhesive strength, high temperature retention) to the adherend and does not stain the adherend when peeled (also called re-peeling). A contradictory performance is required with less (removability).
In addition, in order to make it easier to remove the tape and further improve removability, it is required that the end of the tape can be held in a state where it is folded back to the adhesive side as a handle when removing the tape (self-adhesive surface adhesiveness). .

Adhesives suitable for temporary fixing adhesive tapes used for this 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 tackifier with a curing agent in the presence of a zirconium compound. In Patent Document 2, an undercoat layer made of a composition containing a rubber component made of natural rubber obtained by polymerizing methyl methacrylate, an isocyanate compound, and an aminoethylated acrylic resin is provided between a rubber-based pressure-sensitive adhesive layer and a substrate. is described. Patent Document 3 describes pressure-sensitive adhesive sheets provided with a layer comprising a solid-type pressure-sensitive adhesive composition obtained by adding a tackifier to a rubbery polymer and cross-linking with an isocyanate-based cross-linking agent.

JP 2014-034582 A JP 2014-240484 A Japanese Patent Application Laid-Open No. 2001-181596

In Patent Document 1, the use of an organic zirconium compound as the zirconium compound and the curing with an isocyanate-based curing agent as the curing agent are said to increase the cohesive force of the pressure-sensitive adhesive. Since the fraction is low (17 to 30%) and the measurement conditions are moderate, it is expected that the high-temperature holding power and adhesive residue property, which are the objectives of the present invention, will be inferior.

In Patent Document 2, as a preferred embodiment, the adhesive layer comprises 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 tackifying resin. and 0.1 to 15 parts by weight of a cross-linking agent, and when combined with the above-mentioned specific undercoat layer, it has a strong adhesive force and leaves adhesive residue on the adherend when the tape is peeled off. contamination is significantly suppressed. In addition, the addition of liquid isoprene rubber containing peroxides in the molecule eliminates the use of sulfur and peroxides, which are commonly used in natural rubber cross-linking (vulcanization). It is said that the cross-linking in the environment becomes possible. Further, although it is described that an epoxy resin, an isocyanate resin, or the like is used as a cross-linking agent, the epoxy resin is preferably used (paragraph 0023). In the examples, although an isocyanate compound is used in the undercoat layer, the cross-linking agent for the adhesive layer is an epoxy system, and the adhesive layer is not only pure natural rubber but also a liquid rubber having a peroxide in the molecule. It is crosslinked using isoprene rubber. The pass/fail of the gel fraction is set as low as 20%, and the pass/fail of the retention force measurement conditions is also low.

The adhesive composition of Patent Document 3 is a solvent-free solid type composition obtained by adding a tackifier and an isocyanate-based cross-linking agent to a rubbery polymer made of natural rubber, heating and kneading at 80 to 120 ° C. and simultaneously cross-linking. It is a thing. By devising a heat-kneading method, even a solid type using an isocyanate-based cross-linking agent can achieve moderately weak cross-linking, increasing cohesion while maintaining adhesive strength. It is said that it became possible to disperse evenly without causing liquefaction. However, in Patent Document 3, an adhesive force test by peeling at 23° C. and a holding force test by a load of 2 kg at 40° C. are conducted, but properties at higher temperatures are not evaluated.

Also, in the past, a tape for temporary fixing of articles using an acrylic adhesive, which has excellent fixing power and cohesive strength, has been studied, but acrylic adhesive has self-adhesive surface adhesion. In addition, the adhesion to metals and glass is high, and there is concern about contamination of adherends during re-peeling.

The purpose of the present invention is to provide a rubber-based adhesive composition that has excellent adhesive strength, high-temperature retention, and low staining properties for various adherends including metals, resins, and coating materials.

In addition, the present invention uses a rubber-based adhesive, and even if it is exposed to a high temperature or a hot and humid environment in the manufacturing / assembly stage or transportation stage of the article, the adherend after re-peeling is less contaminated, and the tape is re-peelable. It is easy to peel off because the end of the tape can be folded back to the adhesive side as a handle, and it has excellent adhesive strength, so it can be used to temporarily fix items even with a narrow width. An object of the present invention is to provide a fixing adhesive tape.

A pressure-sensitive adhesive composition according to one aspect of the present invention is a pressure-sensitive adhesive composition containing natural rubber, a cross-linking agent, a tackifier, and a cross-linking modifier, and the minimum temperature of the loss tangent after curing of the pressure-sensitive adhesive composition is 78.7. C. or higher, the minimum value is 0.20 or less, and the maximum temperature of the loss tangent is 25.0.degree. C. or less and the maximum value is 1.15 or less.

A 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 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 contamination) to various adherends including metals, resins, and coating materials. is provided.

Further, according to another aspect of the present invention, a temporary fixing adhesive that has a strong fixing force required in the manufacturing / assembling stage and the transportation stage of an article, has less contamination of the adherend when removed again, and is easy to peel off. Adhesive tape suitable for

It is the figure which showed one structural example of the adhesive tape to which the form for implementing invention is applied. It is the figure which showed the other structural example of the adhesive tape with which the form for implementing invention is applied.

An adhesive composition according to one 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 tackifier, and a cross-linking modifier. The minimum value is 0.20 or less, and the maximum temperature of the loss tangent is 25.0° C. or less and the maximum value is 1.15 or less.

<Loss tangent>
Loss tangent (loss modulus (G″)/storage modulus (G′)=loss tangent (tan δ)) means the degree of contribution of loss modulus (viscosity) to storage modulus (elasticity).
When the minimum temperature of the loss tangent after curing of the adhesive composition is 78.7 ° C. or higher, the minimum value of the degree of contribution to the loss elastic modulus (viscosity) is small, and the cured product made of the adhesive composition is a predetermined In other words, the pressure-sensitive adhesive layer made of the present pressure-sensitive adhesive composition maintains appropriate hardness even at relatively high temperatures. If the minimum loss tangent temperature is less than 78.7° C., the holding power at high temperatures is poor.
In addition, the fact that the minimum value of the loss tangent after curing of the adhesive composition is 0.20 or less indicates that the cured product (adhesive layer) of the adhesive composition is unlikely to become excessively soft and difficult to flow. .

Furthermore, the maximum temperature of the loss tangent indicates the glass transition temperature, and the fact that the maximum temperature of the loss tangent of the present adhesive composition is 25.0 ° C. or less means that the cured product of the present adhesive composition has a low glass transition temperature and a low temperature. However, it shows that moderate flexibility is maintained.
In addition, the maximum value of the loss tangent indicates the peel resistance, and the maximum value of the loss tangent of the cured product of the adhesive composition is 1.15 or less, so that the peel resistance when used as an adhesive layer is small. It shows that the adhesive tape using the object is easy to peel off.

Each component will be explained.
<Natural rubber>
Natural rubber is obtained by coagulating and drying natural rubber latex, which is the sap of rubber trees, and is a substance composed mainly of cis-1,4-polyisoprene.
As for the structure of a natural rubber molecule, one end of a 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 the phosphate lipid end. It is said to be a bonded structure.
In addition, natural rubber contains 3 to 4% by mass of non-rubber components such as proteins and lipids.
Therefore, natural rubber can be easily crosslinked and cured with a crosslinking agent, which will be described later. In addition, since the adhesive composition according to the present invention is crosslinked and cured, the crosslinked product is also referred to as a cured product.

Classifications of the natural rubber used include, for example, Standard Malaysian Rubber (SMR), Standard Indonesian Rubber (SIR), Ribbed Smoked Sheet (RSS) Nos. 1-6, and Pale Crepe Nos. 1-3.

In general, unmasticated natural rubber has a very high molecular weight. If the molecular weight of the natural rubber is too high, the plasticity of the natural rubber is high and the pressure-sensitive adhesive composition lacks flexibility, making it difficult to obtain appropriate pressure-sensitive adhesive properties. may not be possible.
Therefore, it is necessary to mechanically masticate natural rubber in advance using a pressure kneader, a Banbury mixer, an open roll, or the like, to moderately reduce the molecular weight of the natural rubber and adjust the plasticity, and use it for compounding.

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

<Crosslinking agent>
Known methods for cross-linking natural rubber include a vulcanization treatment method using a vulcanizing agent and a cross-linking method by reaction between functional groups.
In the vulcanization method, a sulfur-based, thiuram-based, or quinoid-based vulcanizing agent acts on the unsaturated bonds contained in the molecular main chain of natural rubber, and the reaction mechanism is such that the polymers are directly crosslinked. Dense and strong cross-linking with a large cohesive force can be realized.

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

On the other hand, in the cross-linking method by reaction between functional groups, functional groups such as hydroxyl groups and carboxyl groups that may be introduced into the molecular side chains during the production process of natural rubber and 3 to 4% by mass are mixed into natural rubber. Functional groups of non-rubber components such as proteins and lipids and polyfunctional compounds having functional groups reactive therewith are added to perform cross-linking by 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, etc. can be used as the cross-linking agent.

In addition, the non-sulfur cross-linking agent, which is not a vulcanizing agent, does not contain sulfur, which is a concern for metal corrosion. more preferred.

The present inventors have found that if natural rubber can be flexibly and densely crosslinked, it will have excellent adhesive strength required for temporary fixing of articles, high cohesive strength, and excellent high temperature retention and removability. We thought we could provide a rubber-based adhesive. In order to achieve this purpose, based on the above common technical knowledge, a cross-linking agent characterized by being non-sulfur and capable of high cross-linking was examined by trial and error. .

As a result, the present inventors have found that by using a cross-linking agent containing an isocyanate-based compound as a main component, among the cross-linking agents described above, a pressure-sensitive adhesive composition having excellent adhesive strength required for temporarily fixing natural rubber to an article can be obtained. It was discovered that the material can be flexibly and densely crosslinked.

Furthermore, among the isocyanate compounds, 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, excellent adhesion to various adherends We discovered that it is possible to provide a rubber-based pressure-sensitive adhesive that has strength, high-temperature retention, and removability.

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

The cross-linking agent can be used by adding 1 to 15 parts by mass, preferably 2.5 to 10 parts by mass, per 100 parts by mass of natural rubber. Each characteristic of the loss tangent described above can be satisfied by using the amount within this range.

<Tackifier>
In the adhesive composition of the present embodiment, a tackifying resin having good compatibility with natural rubber can be used as a tackifier, particularly a group consisting of petroleum-based resins, terpene resins, rosin resins, and other resins having a softening point of 125 ° C. or higher. At least one more selected resin can be used. In particular, petroleum-based resins (saturated aliphatic hydrocarbon resins) having a softening point of 125° C. or higher are preferred. Such a tackifier can be used by adding 50 to 100 parts by weight, preferably 60 to 90 parts by weight, to 100 parts by weight of natural rubber.
To obtain 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 when a tackifying resin having a softening point lower than 125°C is used as a tackifier. may not be possible.
Moreover, when the amount of the tackifier added is too large or too small, it may not be possible to obtain the adhesive composition and the adhesive tape having the above physical properties.

<Crosslinking modifier>
In the adhesive composition of the present embodiment, the degree of crosslinking (degree of gelation) of the composition is adjusted by using a crosslinking regulator. This is used for the purpose of realizing a moderately flexible and dense cross-linking reaction within a range in which both excellent adhesive strength of the adhesive composition and high cohesive strength and high-temperature holding power can be achieved. In particular, in the present invention, a compound that inhibits to some extent the reaction between the isocyanate compound as the cross-linking agent and the hydroxyl groups of natural rubber is used as the cross-linking modifier.

In the 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, etc., as a cross-linking modifier. Additional compounds can be used.
Specific examples of the hindered phenol compounds include pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2'-thiodiethylbis[3-( 3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 3-(4′-hydroxy-3′,5′-di-tert-butylphenyl)propionate-n-octadecyl, N,N′ -(hexane-1,6-diyl)bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanamide], octyl-3,5-di-tert-butyl-4-hydroxy- hydrocincinic acid, 2,4,6-tris(3′,5′-di-tert-butyl-4′-hydroxybenzyl)mesitylene, 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-triazin-2-yl]amino]-2,6-di-tert-butylphenol and the like.

Further, specific examples of phosphorus-based compounds include tris(2,4-di-tert-butylphenyl) phosphite. Specific examples of metal compounds 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 benzotriazole compounds include 4-methyl-2-(2H-benzotriazol-2-yl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1 -methyl-1-phenylethyl)phenol, 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol, 2,2′-methylenebis[ 6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol], benzotriazolyldodecyl P-cresol. Specific examples of triazine compounds include 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-(hexyloxy)phenol. Specific examples of hindered amine compounds 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 succinate 1-(2hydroxyethyl)-4 -hydroxy-2,2,6,6-tetramethyl-4-piperidine polycondensate, 2-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]-2-butyl Bis[1,2,2,6,6-pentamethyl-4-piperidinyl]propanedioate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1-methyl 10-sebacate (1,2,2,6,6-pentamethyl-4-piperidyl) and the like. Among them, a preferred cross-linking regulator is at least one compound selected from the group consisting of hindered phenolic compounds.

The amount of the cross-linking modifier is not particularly set, but if the amount of the cross-linking modifier added is too large, the natural rubber cannot be cross-linked flexibly and densely, and the adhesive strength and adhesive strength required for temporary fixing of articles cannot be obtained. In some cases, it may not be possible to obtain a PSA composition and PSA tape that achieve both high cohesive strength 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 parts by mass or more and 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 adhesive composition may contain inorganic fillers, organic fillers such as resins, softeners, plasticizers, surfactants, coupling agents, colorants, One or more of preservatives, heat stabilizers, light stabilizers, etc. may be further added.
As used herein, the term "adhesive composition" means both a mixture of components before cross-linking and a composition after cross-linking. , in which case "adhesive composition" means the composition after cross-linking. In addition, the state of dissolving or dispersing in a solvent to form an adhesive layer, and the dried product obtained by removing the solvent may also be referred to as the "adhesive 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 comprising the pressure-sensitive adhesive composition is formed on at least one surface of a sheet-like base material. For example, as shown in FIG. 1, a single-sided adhesive tape having an adhesive layer 12 made of the adhesive composition on one side of a substrate 11, or an adhesive provided on both sides of a substrate 21 as shown in FIG. It is a double-sided tape using the above adhesive composition for at least one of the layer 22 and the adhesive layer 23, or both.

The pressure-sensitive adhesive layer 12 in FIG. 1 and the pressure-sensitive adhesive layers 22 and/or 23 in FIG. , a die coater or the like, or co-extrusion of the 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 modifier, and other additives in a solvent such as toluene. Coat one side or both sides of the base material 21 using a coater or the like so that the thickness of the adhesive layer after drying is uniform, and then dry and cure the coated adhesive composition at a predetermined temperature. formed by

The thickness of the 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. Any thickness may be used, but the thickness is usually about 10 to 70 μm, preferably 25 to 50 μm.

In addition, the surface (surface 11A) of the sheet-like base material 11 in FIG. can improve the adhesion of the pressure-sensitive adhesive layer 12 to the substrate 11 . In addition, by providing a release layer on the surface 11B opposite to the surface 11A of the sheet-like base material 11 in FIG. While preventing the adhesive composition from adhering to the surface 11B of the base material 11, it is possible to maintain ease of unwinding (pulling out).

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

<Sheet-like base material>
The type of the sheet-shaped substrate is not particularly limited, and any sheet-shaped substrate such as commonly used known films, foams, woven fabrics, knitted fabrics, and non-woven materials such as paper may be used.
Among them, resin-made film substrates are preferable, and resin materials such as polyethylene (PE), polypropylene (PP), oriented polypropylene (OPP), polyester, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyethylene naphthalate (PEN ), polyphenylene sulfide, ethylene-vinyl acetate copolymer (EVA), and blends thereof. A film made of such a synthetic resin is excellent in mechanical strength and does not cause contamination of adherends, and is preferable as an adhesive tape for temporary fixing used in the manufacturing/assembling stage and transportation stage of articles.

Furthermore, the thickness of the sheet-like base material can be appropriately selected and used within a range in which the strength required for the adhesive tape can be maintained. is more preferred. Especially in the case of polyethylene terephthalate (PET) film in that thickness range, it has excellent mechanical strength, exerts high fixing force, does not cause contamination of adherends, and can be used in the manufacturing / assembly stage and transportation stage of articles. It is more preferable as an adhesive tape for temporary fixing.

<Undercoat>
There are no particular limitations on the undercoat agent used in the undercoat layer, and any agent may be used as long as it exhibits its effect. In particular, if it has a functional group that can react with the functional group of the compound contained in the pressure-sensitive adhesive layer, the undercoat layer will also react during the cross-linking to form the pressure-sensitive adhesive layer, resulting in adhesion to the substrate. can increase power. The coating weight or basis weight of the undercoat layer after drying is generally 0.2 to 2 g/m ² , preferably 0.4 to 1.2 g/m ² .

<Release agent>
When the adhesive layer 12 is formed on one surface 11A of the base material 11 as shown in FIG. 1 and wound into a roll, the adhesive layer comes into contact with the other surface 11B of the base material. . It is preferable to form a release layer on the surface 11B in order to improve the pullability from the roll. The release agent used in the release layer is not particularly limited, and any agent may be used as long as it exhibits its effect. For example, silicone resins, long-chain alkylvinyl monomer polymers, fluorinated alkylvinyl monomer polymers, polyvinyl alcohol carbamate, and the like are known. Among these, the silicone resin is excellent in the property of improving the release performance of the base material surface. The adhesion amount or basis weight of the release layer after drying is generally 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 pressure-sensitive adhesive tape as shown in FIG. 2, it is preferable in terms of handleability to laminate a release sheet on the outer surface of the pressure-sensitive adhesive layer in a peelable manner. Moreover, in the case of winding in a roll shape, the adhesive layer 22 and the adhesive layer 23 can be wound with a release sheet sandwiched therebetween. Since the release sheet does not require much high strength, a sheet having one or both sides subjected to the release treatment as described above can be used.

EXAMPLES 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.
Moreover, in the following description, "parts" means "parts by mass".

Materials used in Examples and Comparative Examples are as follows. The physical property values of each material are manufacturer's catalog values.
Base material: PET film (thickness 38 μm)
Natural rubber: Pale crepe (grades with different Mooney viscosities listed in the table are used)
Crosslinker:
A. Trade name “Millionate MR-200”,
Polymeric MDI made by Tosoh
B trade name "Coronate L-45E",
Modified polyisocyanate C, trade name “E-5C” manufactured by Tosoh, Epoxy cross-linking agent D, trade name “Vulkacit Thiuram/C” manufactured by Soken Chemical, LANXESS Corporation,
Thiuram vulcanizing agent (tetramethylthiuram disulfide)
Tackifier:
A Trade name “Pencel D-135”, manufactured by Arakawa Chemical Industries, 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°C ± 5°C
C Product name "Arcon P-100", manufactured by Arakawa Chemical Industries, Ltd.
Petroleum resin, softening point 100°C ± 5°C
Crosslinking modifier: trade name "Irganox 1010", manufactured by BASF Japan,
(Hindered phenol compound)

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

The obtained pressure-sensitive adhesive tape was evaluated as follows.
(loss tangent)
Using each adhesive composition, an adhesive layer (thickness: 2 mm) for measurement was produced.
Then, the pressure-sensitive adhesive layer was punched into a piece having a diameter of 10 mm, and the piece was fixed by sandwiching it between parallel plates to obtain a measurement sample.
For this measurement sample, using a dynamic viscoelasticity measuring device, dynamic viscoelasticity measurement was performed under the following conditions to create a temperature dependence graph of loss elastic modulus (G″) and storage elastic modulus (G′). A minimum temperature, a minimum value, a maximum temperature, and a maximum value were obtained from Modulus (G″)/storage modulus (G′)=loss tangent (tan δ). In addition, as an evaluation, the minimum side (minimum temperature of 78.7 ° C. or higher and the minimum value of 0.20 or less) and the maximum side (maximum temperature of 25 ° C. or less and the maximum value of 1.15 or less) satisfy the specified range. "Y" for the case, and "N" for the case not satisfied.

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

(Adhesive force)
Adhesive strength was measured using a test method based on JIS Z 0237:2000.
As the adherend, PS (polystyrene), PP (polypropylene), PC (polycarbonate), rough PC (matted on one side, manufactured by Takiron C.I., trade name "PCSP K6600"), glass, SUS plate (# SUS304 plate polished until the surface is uniform with 280 water-resistant abrasive paper), Al plate, acrylic-coated plate (SPCC-SB acrylic-coated plate manufactured by Nippon Steel Corporation (Paint: "New Acrotze Black Glossy" manufactured by Dainippon Toryo Co., Ltd.) Yes”)) was used.

The adhesive strength of the adhesive composition in the present embodiment is preferably, for example, 2.0 N/10 mm or more and 8 N/10 mm or less. A", one adherend is out of range but other adherends can maintain this range "B", two or more adherends are out of this range was rated "C".

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

(Adherend staining property)
Attach an adhesive tape to each adherend used to measure adhesive strength, leave it in an atmosphere of 65 ° C. and 85% RH for 7 days or more, then leave it in an atmosphere of 5 ° C. for 2 hours or more to cool, and cool it in an atmosphere of 5 ° C. , the adhesive tape was manually peeled off from the adherend, and the presence or absence of adhesive residue or contamination on the adherend was visually examined.
"A" indicates no adhesive residue, tape traces, or contamination; "B" indicates almost no adhesive residue, tape traces, or contamination; was determined as "C".

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

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

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

On the other hand, in Comparative Examples 1, 2, and 7 to 12, as shown in Table 2-2, the adhesive strength was excellent, but the high temperature holding power was poor. Comparative Examples 3 and 4 were excellent in high-temperature holding power, but inferior in adhesive strength. Comparative Examples 5 and 6 were inferior in both adhesive strength and high temperature holding power. In addition, all of the comparative examples included a case where the adherend staining property was ranked D, 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, having excellent adhesive strength to various adherends (articles) and exhibiting low contamination.

11, 21

base material

12, 22, 23 adhesive layer

Claims

A pressure-sensitive adhesive composition comprising a natural rubber, a cross-linking agent, a tackifier and a cross-linking modifier, wherein the minimum temperature of the loss tangent after curing of the pressure-sensitive adhesive composition is 78.7° C. or more and the minimum value is 0.20 or less. and the maximum temperature of the loss tangent is 25.0° C. or less and the maximum value is 1.15 or less.
2. The adhesive composition according to claim 1, wherein the natural rubber has a Mooney viscosity ML 1+4 (100° C.) of 20-85.
3. The adhesive composition according to claim 2, wherein the natural rubber has a Mooney viscosity ML 1+4 (100° C.) of 20-35.
The adhesive composition according to any one of claims 1 to 3, wherein the cross-linking agent is a non-sulfur-based cross-linking agent.
The adhesive composition according to claim 4, wherein the cross-linking agent contains an isocyanate compound.
The adhesive composition according to claim 5, wherein the isocyanate compound has a diphenylmethane diisocyanate structure.
The adhesive composition according to any one of claims 1 to 6, wherein the tackifier comprises a petroleum-based resin having a softening point of 125°C or higher.
8. Any one of claims 1 to 7, wherein the cross-linking modifier is at least one compound selected from hindered phenol compounds, phosphorus compounds, metal compounds, benzotriazole compounds, triazine compounds, and hindered amine compounds. 1. The adhesive composition according to claim 1.
9. Any one of claims 1 to 8, comprising 1 to 15 parts by mass of the cross-linking agent, 50 to 100 parts by mass of the tackifier, and 1 to 5 parts by mass of the cross-linking modifier with respect to 100 parts by mass of the natural rubber. 1. The adhesive composition according to item 1.
An adhesive tape having an adhesive layer made of the adhesive composition according to any one of claims 1 to 9 on at least one surface of a sheet-like base material.