JP7159764B2 - foam adhesive tape - Google Patents

Description

TECHNICAL FIELD The present invention relates to a foamed pressure-sensitive adhesive tape, and more particularly to a foamed pressure-sensitive adhesive tape that can be suitably used as a member for non-portable electronic devices.

Conventionally, in car navigation systems, monitors, and the like used in vehicles, adhesives have been used for the purpose of bonding internal housings and filling gaps between members. In recent years, however, such vehicle-mounted car navigation systems, monitors, and the like have tended to increase in size, and gaps between members have become larger, making it difficult to seal them with an adhesive. Therefore, foam adhesive tapes have been used for the purpose of filling large gaps.

Foamed adhesive tapes are required to have re-applying workability (reworkability) that allows easy re-applying work, and include an adhesive layer on one or both sides, fix the adhesive layer to the member, and fill the gap. used as
In addition, such re-bonding work is not only performed immediately after bonding work, but may be performed several days later. In addition, since the material is sometimes stored in a hot and humid environment, it can be easily reapplied even after being stored in a hot and humid environment for several days, and its adhesive strength does not change over time. is required.

Furthermore, in non-portable electronic devices such as car navigation systems, members are larger in size than in small portable electronic devices, etc., and when tapes are adhered together, misalignment of the position of adhesion may occur. For this reason, it is also required to have the property of being able to remove the tape immediately after it is attached to one surface of the members to be attached and then to correct the attachment position in the event that the tape is displaced.

As a foam adhesive tape, on both sides of a specific foam base material, an acrylic copolymer having a (meth)acrylate having 4 to 12 carbon atoms and a vinyl monomer having a carboxyl group as a monomer component, and a polymerized rosin ester adhesive A foam pressure-sensitive adhesive tape (Patent Document 1) having a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive composition containing a imparting resin, and a linear or branched alkyl group on both sides of a specific foam base material A foam having an acrylic pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing a specific acrylic polymer composed of a (meth)acrylic acid alkyl ester as an essential monomer component and a polymerized rosin ester as a tackifying resin Technologies such as an adhesive tape (Patent Document 2) are disclosed.

However, these conventional foamed pressure-sensitive adhesive tapes are excellent in re-applying workability immediately after re-applying work, and furthermore, they have not been able to achieve sufficient performance in terms of re-peelability and re-applying workability after aging or heat resistance. Currently there is none.

JP 2010-260880 A JP 2013-040329 A

An object of the present invention is to provide a foam pressure-sensitive adhesive tape that is excellent in workability for re-application and that exhibits little change in adhesive strength over time.

That is, the subject is a foam pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on one or both sides of a foam substrate, wherein the pressure-sensitive adhesive layer contains an acrylic copolymer (A) and an isocyanate compound (B). , and does not contain a tackifying resin, the acrylic copolymer (A) is a copolymer of a monomer mixture containing a hydroxyl group-containing monomer and not containing a carboxyl group-containing monomer, wherein 100% by weight of the monomer mixture , the content of hydroxyl group-containing monomer is 2-12% by weight, solved by foam adhesive tape.

According to the present invention, a foam that has both reapplication workability and performance with little change in adhesive strength over time, and that can reduce material loss and work process time more than before when using a foam adhesive tape. Adhesive tape can be provided.
In addition, since it is excellent in reattachability, it can be suitably used for non-portable electronic device members which are larger in size than portable items and tend to cause misalignment in attachment.

In the present invention, the terms adhesive sheet, adhesive tape, and adhesive film are synonymous.

The foamed pressure-sensitive adhesive tape of the present invention includes a pressure-sensitive adhesive layer on one or both sides of a foam base material, the pressure-sensitive adhesive layer contains an acrylic copolymer (A) and an isocyanate compound (B), and is tackified. The acrylic copolymer (A) containing no resin is a copolymer obtained by copolymerizing a monomer mixture containing a hydroxyl group-containing monomer and not containing a carboxyl group-containing monomer, wherein the monomer mixture is 100% by weight. Among them, the content of the hydroxyl group-containing monomer is 2 to 12% by weight.

In addition, the foamed pressure-sensitive adhesive tape of the present invention can be used for various electronic devices. Since there is little change in adhesive strength over time, it can be suitably used for members of non-portable electronic devices.

Non-portable electronic devices are used as components of electronic devices such as home TVs, desktop computers and their monitors, vehicle-mounted car navigation systems, and vehicle-mounted monitors that are not generally carried and used by people. It does not include smartphones, tablets, laptops, mobile navigation systems, mobile monitors, mobile cameras, etc. that people carry around.

《Adhesive layer》
The pressure-sensitive adhesive layer of the present invention is formed on one side or both sides of the foam substrate, and the pressure-sensitive adhesive layer contains an acrylic copolymer (A) and an isocyanate compound (B). And the adhesive layer does not contain a tackifying resin. Further, the adhesive layer is a copolymer obtained by copolymerizing a monomer mixture in which the acrylic copolymer (A) contains a hydroxyl group-containing monomer and does not contain a carboxyl group-containing monomer, and the monomer mixture 100 The content of the hydroxyl group-containing monomer is 2 to 12% by weight.

The pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive that contains the acrylic copolymer (A) and the isocyanate compound (B) and does not contain a tackifying resin.
A known method such as a roll coater method, a comma coater method, a lip coater method, a die coater method, a reverse coater method, a silk screen method, or a gravure coater method can be used for coating the adhesive. After coating, it can be dried with a hot air oven, an infrared heater, or the like.

The thickness of the adhesive layer is preferably 5-200 μm, more preferably 10-150 μm. By setting the thickness of the pressure-sensitive adhesive layer within the above range, it is possible to obtain a pressure-sensitive adhesive tape having excellent pressure-sensitive adhesive performance and heat resistance.

The adhesive strength of the adhesive layer to a stainless steel plate after 72 hours at 60° C.-90% RH is preferably 25 N/25 mm or less. When the pressure-sensitive adhesive tape is peeled off, it is possible to prevent phenomena such as the foam layer being destroyed and part of the pressure-sensitive adhesive layer remaining on the bonded member. More preferably, the adhesive strength after 72 hours at 60° C.-90% RH is 20 N/25 mm or less.

In addition, when the adhesive layer is provided on both sides of the foam base material, the adhesive strength after 24 hours at 23 ° C.-50% RH is that the adhesive strength of one adhesive layer to the stainless steel plate is the same as that of the other adhesive layer. is preferably at least twice the adhesive force to the stainless steel plate. If one side has twice or more the adhesive strength of the other side, when the adhesive tape is peeled off, the foam layer will be destroyed and part of the adhesive layer will remain on the bonded member. phenomenon can be prevented. It is preferably three times or more.
In addition, the adhesive strength after 23° C.-50% RH-24 hours is 5 N/25 mm or more and 20 N/25 mm or less for the higher adhesive strength, and 1 N/25 mm or more for the lower adhesive strength. It is preferably 10 N/25 mm or less.

<Acrylic copolymer (A)>
In the present invention, the acrylic copolymer (A) is a (meth)acrylic polymer that can be synthesized using an acrylic monomer, and contains a hydroxyl group-containing monomer and does not contain a carboxyl group-containing monomer. The content of the hydroxyl group-containing monomer is 2 to 12% by weight in 100% by weight of the monomer mixture.

[Hydroxyl Group-Containing Monomer]
Further, in the acrylic copolymer (A) of the present invention, the content of the hydroxyl group-containing monomer is 2 to 12% by weight based on 100% by weight of the monomer mixture. By using the hydroxyl group-containing monomer within this range, the cross-linking density between the acrylic copolymer and the curing agent can be controlled, and the adhesive strength necessary for re-sticking workability and the cohesive strength necessary for heat resistance can be balanced. can get. In addition, since hydroxyl groups are highly reactive with isocyanate and unreacted functional groups are less likely to remain, the adhesive strength does not increase over time, and the foamed adhesive tape is peeled off from both members when it is reapplied. It is possible to suppress the phenomenon that the From the above viewpoint, 4 to 12% by weight is more preferable.

Hydroxyl group-containing monomers include, for example, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, glycidyl (meth)acrylate, N-methylolacrylamide, hydroxypropyl (meth) Acrylate and the like may be mentioned, but among these, a hydroxyl group-containing monomer having an alkylene group having 1 to 3 carbon atoms is preferable from the viewpoint of appropriate crosslinkability with a curing agent because it can further improve the cohesive force. 2-Hydroxyethyl (meth)acrylate is more preferred. These monomers may be used alone or in combination of two or more.

[Carboxyl Group-Containing Monomer]
The acrylic copolymer (A) of the present invention does not contain a carboxyl group-containing monomer. When a curing agent such as isocyanate is used for cross-linking an acrylic copolymer having a carboxyl group, unreacted functional groups tend to remain, resulting in an increase in adhesive strength over time and poor reattachment workability. In the present invention, a carboxyl group-containing monomer is an acrylic monomer or the like having a carboxyl group, such as (meth)acrylic acid, itaconic acid, maleic acid, and the like.

[Other acrylic monomers]
The acrylic copolymer (A) is obtained by copolymerizing a hydroxyl group-containing monomer and an acrylic monomer other than the carboxyl group-containing monomer.
Other acrylic monomers include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, propyl (meth)acrylate, pentyl (meth)acrylate, ( meth)hexyl acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, (Meth)acrylamide, vinyl acetate, acrylonitrile and the like can be mentioned, but they are not limited to these and may be used singly or in combination of two or more.

Among them, the other acrylic monomer is preferably butyl (meth)acrylate or isobutyl (meth)acrylate, and at least one of butyl (meth)acrylate and isobutyl (meth)acrylate in 100% by weight of the monomer mixture. is preferably 50% by weight or more. Moreover, when both butyl (meth)acrylate and isobutyl (meth)acrylate are included, the total of these is preferably 50% by weight or more.
Within the above range, the glass transition temperature (Tg) of the pressure-sensitive adhesive becomes high, making it possible to have properties such as removability and heat resistance in a well-balanced manner.
From the above viewpoint, it is more preferably 60% by weight or more.

When synthesizing, a polymerization method such as solution polymerization, emulsion polymerization, bulk polymerization, or polymerization by ultraviolet irradiation can be used. In the present invention, it is preferable to use solution polymerization, which facilitates reaction control and property control.

For the copolymerization, conventionally known polymerization initiators such as peroxide-based polymerization initiators and azobis-based polymerization initiators can be used. Polymerization initiators for organic peroxides include, for example, benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, t-butyl peroxybenzoate, t-butyl peroxyneodecanoate, t-butyl Peroxy 2-ethylhexanoate and the like, and examples of azo polymerization initiators include 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-amidinopropane) dihydrochloride, 2 , 2'-azobis [2-(5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis ( N,N'-dimethyleneisobutylamidine) and the like, and these polymerization initiators may be used alone or in combination of two or more.

The weight average molecular weight of the acrylic copolymer (A) is preferably 200,000 to 1,500,000, more preferably 400,000 to 1,000,000. By setting it to the above range, it is easy to obtain a balance between the low adhesive force necessary for re-applying workability and the cohesive force necessary for heat resistance, and when performing re-applying work, the foam double-sided tape will not come off from both members. This makes it difficult for the phenomenon of In the present invention, the weight average molecular weight is the polystyrene-equivalent weight average molecular weight obtained by GPC measurement.

<Tackifying resin>
The adhesive layer of the present invention does not contain a tackifying resin. By containing the tackifying resin, the adhesiveness to the foam substrate or the like is improved. However, when stored in a high-temperature and high-humidity environment, the tackifying resin softens and the like increases the adhesion to the adherend and increases the adhesive strength, resulting in a decrease in workability for reapplying.
The tackifying resin in the present invention includes, for example, rosin esters, polymerized rosins, hydrogenated rosins, disproportionated rosins, maleic acid-modified rosins, fumaric acid-modified rosins, rosin-based resins such as rosin phenolic resins; Terpene resins such as resins, β-pinene resins, dipentene resins, aromatic modified terpene resins, hydrogenated terpene resins, terpene phenol resins, acid modified terpene resins, styrenated terpene resins, alkylphenol resins, coumarone resins, styrene resins , petroleum-based resins or copolymers thereof.

<Isocyanate compound (B)>
The pressure-sensitive adhesive layer of the invention contains an isocyanate compound (B).
The content of the isocyanate compound (B) is preferably 0.05 to 10 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A). By adjusting the above range, it is easy to control the cross-linking density between the acrylic copolymer (A) and the curing agent, and the balance between the low adhesive strength necessary for re-sticking workability and the cohesive strength necessary for heat resistance can be obtained. This makes it difficult for the foamed adhesive tape to come off from both members when it is used as a double-sided foamed adhesive tape and reattached. From the above viewpoint, it is more preferably 0.10 to 8 parts by weight.

Examples of the isocyanate compound (B) include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, and triphenylmethane. Polyisocyanate compounds such as triisocyanate and polymethylene polyphenyl isocyanate, adducts and burets of these isocyanate compounds and polyol compounds such as trimethylolpropane, and isocyanurates, further these isocyanate compounds and known polyether polyols and polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols and the like, and the preferred isocyanate compound is the adduct of tolylene diisocyanate trimethylolpropane.

In addition, aziridine compounds other than isocyanate compounds, metal chelate compounds, epoxy compounds, and the like can be used as long as they do not impair the performance required in the present invention.

As the metal chelate compound, for example, a metal complex compound can be used. Metals include nickel, aluminum, chromium, iron, titanium, zinc, cobalt, manganese, copper, tin, zirconium and the like. Examples of metal chelate compounds include ferric trisacetylacetonate, aluminum trisacetylacetonate, aluminum monoacetylacetonate bis(ethylacetoacetate), and aluminum tris(ethylacetoacetate). Aluminum trisacetylacetonate is more preferred.

Examples of aziridine compounds include N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane, 4'-bis(1-aziridinecarboxamide), trimethylolpropane-tri-β-(2-methylaziridine) propionate and the like.

Examples of epoxy compounds include bisphenol A, epichlorohydrin type epoxy resins, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, trimethylolpropane tri glycidyl ether, diglycidylaniline, diamineglycidylamine, N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N'-diamineglycidylaminomethyl)cyclohexane; be done.

These curing agents may be used alone or in combination of two or more.

<Other additives>
The adhesive of the present invention includes fillers, pigments, dyes, diluents, anti-aging agents, polymerization inhibitors, ultraviolet absorbers, ultraviolet stabilizers, coupling agents, etc., which are blended in known adhesives as necessary. , various additives may be included, and two or more kinds may be used. Moreover, the amount of the additive to be added is not particularly limited as long as it is an amount that provides the required physical properties.

<<Foam base material>>
Examples of foam substrates include foams such as polyolefin foams, urethane foams, and EPDM (ethylene-propylene-diene rubber) foams. From the viewpoint of properties, it is preferable that the foam is a polyolefin foam that is resistant to heat deterioration.

In addition, the foam base material of the present invention preferably has a density of 300 kg/m ³ or more in JISK7112 A method for measuring the density and specific gravity of plastic-non-foamed plastics. When the density of the foam is within the above range, it is possible to prevent a phenomenon in which part of the adhesive tape remains on the bonded member due to destruction of the foam layer during re-pasting. From the above viewpoint, it is more preferable that the density is 500 kg/m ³ or more.

In addition, it is preferable that the foam base material of the present invention is subjected to adhesion-facilitating treatment such as plasma treatment or corona treatment. Adhesion of the adhesive to the foam base material is improved by applying an easy-adhesion treatment such as plasma treatment or corona treatment to prevent peeling between the foam layer and the adhesive layer. can be done.

The release liner for producing the pressure-sensitive adhesive sheet has a release layer formed by applying a release agent to a substrate such as paper, plastic film, synthetic paper, or the like. Release agents include, for example, silicones, alkyd resins, melamine resins, fluorine resins, acrylic resins, and the like. The thickness of the release liner is not particularly limited, but is about 10 to 200 μm.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. In the examples, "parts" means "parts by weight" and "%" means "% by weight". In order to be consistent with the invention according to claim 1, Examples 7, 8, 11 and 12 described later shall be read as Reference Examples 1 to 4, and Examples 13 to 19 shall be read as Reference Examples 5 to 10.

The method for measuring the weight average molecular weight of the copolymer is shown below.
<Method for measuring weight average molecular weight>
The weight average molecular weight of the copolymer is a polystyrene-equivalent value determined by GPC measurement.
GPC measurement conditions are as follows.
Apparatus: SHIMADZU Prominence (manufactured by Shimadzu Corporation) Column: TOSOH TSK-GEL GMHXL (manufactured by Tosoh Corporation) was used. Solvent: tetrahydrofuran, flow rate: 0.5 ml/min, temperature: 40°C, sample concentration: 0.1% by weight, sample injection volume: 100 µl

[Foam base material]
・Foam base material 1: Polyolefin foam base material "Density: 700 kg/m ³ ", "Thickness: 200 µm", "Easy adhesion treatment completed"
・Foam base material 2: Polyolefin foam base material "Density: 500 kg/m ³ ", "Thickness: 200 µm", "Easy adhesion treatment completed"
・Foam base material 3: Polyolefin foam base material "Density: 300 kg/m ³ ""Thickness: 200 µm""Easy adhesion treatment completed"
・Foam base material 4: Polyolefin foam base material "Density: 150 kg/m ³ ", "Thickness: 200 µm", "Easy adhesion treatment completed"
・Foam base material 5: Polyolefin foam base material "Density: 700 kg/m ³ ""Thickness: 200 µ""No easy adhesion treatment"
In addition, the density of the foam base material is the value measured by the JISK7112A water substitution method.

<Acrylic copolymer (A)>
(Acrylic copolymer solution (A-1))
20.0 parts by weight of butyl acrylate, 17.5 parts by weight of isobutyl acrylate, and 9.5 parts by weight of methyl acrylate were placed in a four-necked flask equipped with a stirrer, thermometer, reflux condenser, dropping device, and nitrogen inlet tube under a nitrogen atmosphere. 3.0 parts by weight of 2-hydroxyethyl acrylate, ethyl acetate as a solvent, and appropriate amounts of azobisisobutyronitrile as an initiator. Separately, 20.0 parts by weight of butyl acrylate, 17.5 parts by weight of isobutyl acrylate, 9.5 parts by weight of methyl acrylate, 3.0 parts by weight of 2-hydroxyethyl acrylate, ethyl acetate as a solvent, and azo as an initiator are added to a dropping tube. An appropriate amount of bisisobutyronitrile was charged. Then, the flask was gradually heated, and after confirming the start of the reaction, the solution was added dropwise from the dropping tube over 1 hour. Further, the reaction was continued at an internal temperature of about 80°C for 8 hours. After completion of the reaction, the acrylic copolymer solution (A-1) having a nonvolatile content of 40.0%, a viscosity of 5200 mPa s, and a weight average molecular weight of 580000 was prepared by diluting with ethyl acetate and toluene while cooling. Obtained.

(Acrylic copolymer solution (A-2 to 7, AC-1, 2))
Acrylic copolymer solutions (A-2 to 7, AC -1, 2) were obtained.

Abbreviations in Table 1 are as follows. In addition, the numerical value in a table|surface is content (weight part) of solid content conversion.
(Hydroxyl group-containing monomer)
HEA: 2-hydroxyethyl acrylate 2HEMA: 2-hydroxyethyl methacrylate (carboxyl group-containing monomer)
AA: acrylic acid (other monomers)
BA: butyl acrylate IBA: isobutyl acrylate 2EHA: 2 ethylhexyl acrylate MA: methyl acrylate

<Adhesive>
(Adhesive X-1)
As an isocyanate curing agent, an isocyanate compound (tolylene diisocyanate trimethylolpropane adduct) (nonvolatile content of 37.5% by weight) is added to 100 parts by weight of the nonvolatile content of the acrylic copolymer (A-1) of Synthesis Example 1. Ethyl acetate solution) was mixed with 0.15 parts by weight in terms of non-volatile content and an appropriate amount of ethyl acetate as a solvent, and the mixture was stirred with a disper to obtain Adhesive X-1.

(Adhesive X-2 to 8, 11 to 16, 18, XC-1 to 4, 11 to 14)
As shown in Tables 2 and 3, adhesive X- 2-8, 11-16, 18, XC-1-4, 11-14 were obtained.

Abbreviations in the table are as follows. Moreover, the compounding amount is the added amount (parts by weight) in terms of the non-volatile content per 100 parts of the non-volatile content of the acrylic copolymer.
[Tackifying resin]
Pencel D-125 (manufactured by Arakawa Chemical Co., Ltd., rosin ester resin, softening point 125°C)
YS Polyster T115: (manufactured by Yasuhara Chemical Co., terpene phenol resin, softening point 115°C)
[Isocyanate compound]
Tolylene diisocyanate trimethylolpropane adduct 37.5% by weight ethyl acetate solution converted to non-volatile matter

[Example 1]
(Foam double-sided adhesive tape)
The pressure-sensitive adhesive X-1 was applied to a release liner having a thickness of 25 μm so that the thickness after drying was 30 μm, dried at 100° C. for 2 minutes, and then applied to substrate 1 (commercially available polyolefin foam substrate ( Density of 700 kg/m ³ , thickness of 200 µm, easy adhesion treatment)).
Separately, the adhesive X-11 was applied to a release liner having a thickness of 50 μm so that the thickness after drying was 20 μm, dried at 100° C. for 2 minutes, and then the adhesive of the base material 1 was attached. The foam double-sided pressure-sensitive adhesive tape of Example 1 was obtained by laminating it to the non-exposed surface and allowing to stand at 23° C.-50% RH for 1 week.

[Examples 2 to 19, Comparative Examples 1 to 5]
The acrylic copolymer, the tackifying resin, the type and amount (parts by weight) of the curing agent, and the type of foam base material were changed as shown in Tables 4 to 6. Foam double-sided adhesive tapes of Examples 2-12 and Comparative Examples 1-5 were obtained in the same manner as the foam double-sided adhesive tape of Example 1.
Examples 13 to 19 of foam single-sided adhesive tapes were obtained by applying the adhesive only to one side of the foam in the same manner as described above.

<Measurement and Evaluation of Physical Properties of Foam Adhesive Tape>
The following physical properties were measured and evaluated using the resulting foamed pressure-sensitive adhesive tape. The results are shown in Tables 4-6.
The "adhesive strength ratio" in the table means that after 24 hours at 23 ° C - 50% RH, the adhesive strength of the adhesive layer with high adhesive strength is less than that of the other adhesive layer. It is a ratio of how many times the adhesive strength.
For example, in Example 1, the adhesive strength of the adhesive layer with high adhesive strength is 10.0 N/25 mm, and the adhesive strength of the other adhesive layer is 3.5 N/25 mm.
Adhesion ratio = 10.0/3.5 = 2.9
is.

(23°C-50% RH adhesive strength)
After peeling off the release liner from the non-measured surface of the resulting foam adhesive tape and attaching a PET film having a thickness of 25 μm, a sample having a width of 25 mm and a length of 100 mm was prepared. Then, in an atmosphere of 23 ° C.-50% RH, the release liner opposite to the surface where the 25 μm PET film was laminated was peeled off from the obtained sample, and the exposed adhesive layer was applied to the stainless steel plate once with a 2 kg roller. After pressing and leaving for 24 hours, the adhesive force was measured using a tensile tester under the conditions of a peeling angle of 90 degrees and a peeling speed of 0.3 m/min. A single-sided tape was measured in the same manner, except that a PET film having a thickness of 25 μm was not attached to the foam surface to which the adhesive was not applied.

(60℃-90%RH adhesive strength)
After peeling off the release liner from the non-measured surface of the resulting foam adhesive tape and attaching a PET film having a thickness of 25 μm, a sample having a width of 25 mm and a length of 100 mm was prepared. Then, in an atmosphere of 23 ° C.-50% RH, the release liner opposite to the surface where the 25 μm PET film was laminated was peeled off from the obtained sample, and the exposed adhesive layer was applied to the stainless steel plate once with a 2 kg roller. After pressing and leaving in an environment of 60° C.-90% RH for 72 hours, the adhesive strength was measured using a tensile tester under the conditions of a peeling angle of 90 degrees and a peeling speed of 0.3 m/min. A single-sided tape was measured in the same manner, except that a PET film having a thickness of 25 μm was not attached to the foam surface to which the adhesive was not applied.

(Holding force)
After peeling off the release liner from the non-measured surface of the resulting foam adhesive tape and attaching a PET film having a thickness of 25 μm, a sample having a width of 25 mm and a length of 100 mm was prepared. Next, in an atmosphere of 23° C.-50% RH, the release liner opposite to the surface to which the 25 μm PET film was laminated was peeled off from the obtained sample, and the sample was pressed back and forth with a 2 kg roll to a stainless steel plate once. It was left in an atmosphere of 23° C.-50% RH for 20 minutes. After that, attach a weight of 1 kg in an atmosphere of 80 ° C. and set it so that a force is applied in the direction of 180 degrees. was measured.
In the case of a single-sided adhesive tape, the holding power was evaluated in the same manner, except that DF715 (120 μm double-sided tape) manufactured by Toyochem Co., Ltd. was attached to the foam surface to which no adhesive was applied.

(Re-sticking workability 1)
After peeling off the release liner from the non-measured surface of the resulting foam adhesive tape and attaching a PET film having a thickness of 25 μm, a sample having a width of 25 mm and a length of 100 mm was prepared. Then, in an atmosphere of 23 ° C.-50% RH, the release liner opposite to the surface where the 25 μm PET film was laminated was peeled off from the obtained sample, and the exposed adhesive layer was applied to the stainless steel plate once with a 2 kg roller. After crimping and leaving for 72 hours in an environment of 60°C-90% RH, peel off from the stainless steel plate using a tensile tester under the conditions of a peeling angle of 90 degrees and a peeling speed of 0.3 m/min, and apply the adhesive to the stainless steel plate. It was visually confirmed whether or not there was any adhesion (reattachability 1-(1)). In addition, it was confirmed whether or not the foam base material was broken (reattachability 1-(2)). A single-sided tape was measured in the same manner, except that a PET film having a thickness of 25 μm was not attached to the foam surface to which the adhesive was not applied.

(Restickability 1-(1))
◯: Adhesion of the adhesive did not occur. (Good)
Δ: Adhesion of adhesive slightly occurred. (Practical range)
x: Adhesion of adhesive occurred. (Not practical)

(Restickability 1-(2))
◯: No breakage of the foam base material occurred. (Good)
Δ: Destruction of the foam substrate slightly occurred. (Practical range)
x: Destruction of the foam base material occurred. (Not practical)

(Re-sticking workability 2)
The foamed double-sided pressure-sensitive adhesive tape thus obtained was prepared in a size of 25 mm in width and 100 mm in length as a sample. Then, in an atmosphere of 23 ° C.-50% RH, the release liner with the higher adhesive strength of the obtained sample was peeled off, a stainless steel plate was attached to the exposed adhesive layer, and the other lower adhesive strength was peeled off. Peel off the liner, attach the acrylic plate, press it back and forth with a 2 kg roller, leave it for 72 hours in an environment of 60℃-90%, peel off the acrylic plate, and the adhesive tape comes off from both the stainless steel plate and the acrylic plate. Check if the issue occurs.

○: Phenomenon of peeling from both did not occur (good)
Δ: A slight peeling phenomenon occurred from both sides. (Practical range)
×: A phenomenon of peeling off from both sides occurred (practical impractical)

From these results, the adhesive layer contains an acrylic copolymer (A) and an isocyanate compound (B), does not contain a tackifying resin, and the acrylic copolymer (A) contains a hydroxyl group-containing monomer. , a copolymer of a monomer mixture that does not contain a carboxyl group-containing monomer, the content of a hydroxyl group-containing monomer in 100% by weight of the monomer mixture is 2 to 12% by weight, and does not contain a tackifying resin. It was confirmed that a foamed pressure-sensitive adhesive tape having excellent re-sticking workability and little change in adhesive strength over time can be obtained.
In particular, the foamed pressure-sensitive adhesive tape of the present invention can be said to be suitable for use in cases where the adhesive tape of the present invention is larger in size than a portable item and tends to cause misalignment due to its good reattachability.

Claims (5)

A foam adhesive tape comprising an adhesive layer on both sides of a foam base material,
The pressure-sensitive adhesive layer contains an acrylic copolymer (A) and an isocyanate compound (B) and does not contain a tackifying resin,
The acrylic copolymer (A) is a copolymer of a monomer mixture containing a hydroxyl group-containing monomer and not containing a carboxyl group-containing monomer,
The content of the hydroxyl group-containing monomer in 100% by weight of the monomer mixture is 2 to 12% by weight ,
The foam base material has a density of 300 kg/m3 or more as measured by the JISK7112A water substitution method, and is subjected to an easy-adhesion treatment,
The pressure-sensitive adhesive layer has an adhesive strength to a stainless steel plate of 25 N/25 mm or less after 72 hours at 60° C.-90% RH,
A foam pressure-sensitive adhesive tape , wherein the pressure-sensitive adhesive strength of one pressure-sensitive adhesive layer to a stainless steel plate after 24 hours at 23° C.-50% RH is at least twice the pressure-sensitive adhesive strength of the other pressure-sensitive adhesive layer to a stainless steel plate . The foam adhesive tape according to claim 1, wherein the acrylic copolymer (A) has a weight average molecular weight of 200,000 to 1,500,000. 3. The foamed pressure-sensitive adhesive tape according to claim 1, wherein the acrylic copolymer (A) contains 4 to 12% by weight of the hydroxyl group-containing monomer based on 100% by weight of the monomer mixture. The foam pressure-sensitive adhesive tape according to any one of claims 1 to 3, wherein the foam base material is a polyolefin foam. The foam pressure-sensitive adhesive tape according to any one of claims 1 to 4, which is used for members of non-portable electronic devices.