JPH09316407A - Rereleasable pressure-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject sheet having little increase in time-dependent adhesive force to a material to be adhered and capable of easily rereleasing and useful as surface-protecting films by adding a specific amount of a specific phosphoric acid ester-based surfactant. SOLUTION: This adhesive sheet has a pressure-sensitive adhesive layer on a base material and the pressure-sensitive adhesive layer comprises (A) 100 pts.wt. of a copolymer of a monomer mixture comprising (i) 50-99.9wt.% of an acrylate monomer of CH2 =CR1 COOR2 (R1 is H or methyl; R2 is a 2-4C alkyl), 5-0.1wt.% of a carboxyl group-containing monomer and (iii) 45-0wt.% of a monomer capable of being copolymerized with the components (i) and (ii) and (B) 0.1-3 pts.wt. of a phosphoric acid ester-based surfactant consisting of a phosphoric acid ester or its salt expressed by formulas I and II [(n) and (m) are each an added mole number of ethylene oxide; R3 and R4 are each an alkylaryl]. The adhesive tape is made to have <=500g/20mm width as rereleasing force and >=40% degree of residual adhesive force to the surface of the adhered material after rereleasing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-like or tape-like removable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer provided on a substrate.

[0002]

2. Description of the Related Art Conventionally, re-peelable pressure-sensitive adhesive sheets have been widely used for surface protection films, masking tapes for painting, adhesive memos and the like. For example, surface protective films are used for the transportation, storage, and storage of metal and plastic products.
The surface of these products is temporarily protected in order to prevent scratches, contamination, corrosion, etc. during processing, and they are re-peeled from the product surface after reaching the purpose of transportation, storage, processing, etc. .

[0003] For this reason, the surface protective film does not adhere to the adherend during transport, storage and processing of metal products and plastic products, and does not peel off. It is required to be able to do it. However, in the pressure-sensitive adhesive sheets, the wetting of the pressure-sensitive adhesive proceeds due to a change with time after the application, and the adhesive strength tends to increase. As a result, the surface protective film is difficult to peel off again from the adherend, it takes a long time to peel off, and the adhesive of the pressure-sensitive adhesive may remain.

In order to suppress such a change with time, it has been practiced to add a surfactant to the pressure-sensitive adhesive. For example, JP-B-51-20053 and JP-A-60-
In Japanese Patent No. 67579, in a surface protective film, a masking tape, or the like, a phosphate ester-based surfactant having a polyoxyethylene group or the like is added to a pressure-sensitive adhesive in order to impart light peeling property. Proposed.

[0005]

However, even if it is possible to impart light releasability to the surface protective film by adding a phosphoric acid ester-based surfactant, the adherend such as a metal plate is re-peeled after the surface protective film is repeeled. It is easy to contaminate the surface of the adherend, and this contamination cannot be visually confirmed.However, when the paint is applied to the surface of the adherend after re-peeling, the paint may be repelled or peeled off, or the surface of the adherend is made of different materials. When a pressure-sensitive adhesive tape was attached for the purpose of adhering or temporarily fixing the adhesive tape, there was a problem that the adhesive tape was difficult to adhere.

In view of such circumstances, the present invention has little increase in the adhesive force with time on the surface of the adherend, can be easily peeled off again, and has a low contamination property on the surface of the adherend after the peeling off. No repelling or peeling of the coating material on the adherend surface after re-peeling, and a re-peelable pressure-sensitive adhesive sheet that can satisfactorily adhere the pressure-sensitive adhesive tape to the adherend surface after re-peeling The purpose is to provide the kind.

[0007]

To solve the above-mentioned problems, the present inventors have found that the contamination of the surface of an adherend due to the addition of a phosphoric acid ester-based surfactant is leaching of the surfactant onto the surface of the adherend. In order to reduce this pollution,
As a result of diligent studies, when an acrylic pressure-sensitive adhesive was used as a base and a specific amount of a specific phosphoric acid ester surfactant was added to the base, good removability was obtained and the surface of the adherend It is possible to obtain good low stain resistance to the surface of the adherend, prevent repellency and peeling of the paint on the surface of the adherend after re-peeling, and to adhere the pressure-sensitive adhesive tape to the surface of the adherend after re-peeling well. The inventors have completed the present invention by knowing that release type pressure-sensitive adhesive sheets can be obtained.

That is, according to the present invention, in the removable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on a substrate, the above-mentioned pressure-sensitive adhesive layer has the following components a to c; formula _{(1); CH 2 = CR} 1 COOR 2 ... (1) ( wherein, R ₁ represents a hydrogen or a methyl group, R ₂ is 2 carbon atoms
Acrylate monomer represented by 14 alkyl group) 50 to 99.9% by weight b) Carboxyl group-containing monomer 5 to 0.1% by weight c) Copolymerizable with the above-mentioned components a and b A copolymer of a monomer mixture comprising 45 to 0% by weight of a monomer, and the copolymer 10.
D) General formulas (2a) and (2b) with respect to 0 part by weight; (In the formula, n and m are the number of moles of ethylene oxide added, R
₃ , R ₄ is an alkylaryl group) and 0.1 to 3 parts by weight of a phosphoric acid ester-based surfactant consisting of a phosphoric acid ester or a salt thereof, and a removability of 500 g. The present invention relates to a re-peelable pressure-sensitive adhesive sheet having a width of / 20 mm or less and a residual adhesive force rate of 40% or more on the surface of an adherend after re-peeling.

In the present specification, the re-peeling force means that a re-peeling type pressure-sensitive adhesive sheet having a width of 20 mm and a length of 100 mm is pressure-bonded onto the adherend by reciprocating a 2 Kg roller once. , 23 ℃
After leaving it for 20 minutes at a tensile speed of 30 m / min (23
It was peeled by 180 degrees in an atmosphere of 65 ° C. and 65% RH, and the force required at this time was measured.

In the present specification, the residual adhesive strength on the surface of the adherend after re-peeling is an index of the low contamination property on the surface of the adherend, and is the feeling on the surface of the cleaned adherend. The initial adhesive strength (A) of the pressure-sensitive adhesive tape and the re-peelable pressure-sensitive adhesive sheet are attached to the surface of the cleaned adherend, and the re-peelable pressure-sensitive adhesive sheet is re-peeled. The adhesive force (B) of the pressure-sensitive adhesive tape to the surface of the adherend after peeling is measured, and the value is calculated as (B / A) × 100 (%).

The above initial adhesive strength (A) is obtained by applying a pressure-sensitive adhesive tape having a width of 20 mm [Nitto Denko Co., Ltd. No. 31B] is crimped by a method of reciprocating a 2 kg roller once, left at 23 ° C. for 20 minutes, and then peeled 180 degrees at a pulling speed of 300 mm / min (23 ° C., 65% RH atmosphere). It is a measurement of the force required for. The adhesive strength (B) after re-peeling was determined by applying re-peelable pressure-sensitive adhesive sheets to the surface of the cleaned adherend and re-peeling after storing at 40 ° C for 7 days. , The above-mentioned initial adhesive force (A) to the surface of the adherend after the re-peel
The force required for 180 ° peeling of the pressure-sensitive adhesive tape was measured in the same manner as in (1).

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The removable pressure-sensitive adhesive sheets of the present invention include plastic films such as polyethylene film, polypropylene film and polyester film, metal foil, porous materials such as paper and non-woven fabric, and the like. Usually uses a base material of 10 to 300 μm, and a pressure-sensitive adhesive layer is provided on this base material to form a sheet or tape, and the pressure-sensitive adhesive layer is acrylic. It is characterized in that it contains a copolymer of the type as a main component and contains a specific phosphoric acid ester type surfactant therein.

The acrylic copolymer used in the present invention is
a) the following general formula _{(1); CH 2 = CR} 1 COOR 2 ... (1) ( wherein, R ₁ represents a hydrogen or a methyl group, R ₂ is 2 carbon atoms
14) which is an alkyl group of 14) as a main monomer, and b) a carboxyl group-containing monomer and, if necessary, c) the above a and b components can be copolymerized. It can be obtained by using a monomer mixture containing various monomers and copolymerizing them by a known method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization and the like.

In the acrylate monomer of the component a, the alkyl group [R ₂ in the general formula (1)] is an ethyl group, a propyl group,
Butyl group, isobutyl group, isoamyl group, hexyl group,
Heptyl group, 2-ethylhexyl group, isooctyl group,
It is an alkyl ester of acrylic acid or methacrylic acid having an isononyl group or an isodecyl group. These acrylate monomers account for 50 to 99.9 of the total monomers.
It is used in an amount of 67% by weight, preferably 67 to 89.5% by weight. If the content is less than 50% by weight, the initial adhesion is lowered, which is not preferable.

The carboxyl group-containing monomer as the component b is for improving the adhesiveness of the pressure-sensitive adhesive layer to the substrate and improving the initial adhesiveness to the adherend. For example, acrylic. Acids, methacrylic acid, itaconic acid, maleic acid, crotonic acid and the like can be mentioned. These carboxyl group-containing monomers are used in a proportion of 0.1 to 5% by weight, preferably 0.5 to 3% by weight, based on the whole monomers. If the amount is less than 0.1% by weight, problems such as a decrease in adhesion to the substrate tend to occur. If the amount is more than 5% by weight, inconveniences such as an increase in the adhesive force with time tend to occur.

Examples of the monomer of the component c include cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate and acetic acid. vinyl,
Styrene, glycidyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylic acid 2
-Hydroxypropyl, methyl (meth) acrylate, N
-(Meth) acryloylmorpholine, N- (meth) acryloylpyrrolidone, N, N-dimethyl (meth) acrylamide, N-vinyl-2-pyrrolidone and the like. These monomers are used in a proportion of 45% by weight or less, preferably 30% by weight or less, based on the total amount of the monomers. If it is more than 45% by weight, the initial adhesiveness tends to be lowered.

The phosphoric acid ester type surfactant in the present invention has the following general formula (2a) or (2b) as the d component: (In the formula, n and m are the number of moles of ethylene oxide added, R
₃ , R ₄ is an alkylaryl group),
Phosphoric acid ester having a polyoxyethylene alkylaryl ether group in the molecule, or its sodium salt,
Salts such as potassium salt, barium salt, and triethanolamine salt are used. Both the monoester of the general formula (2a) and the diester of the general formula (2b) have a number of moles of ethylene oxide added (n in the formula) from the viewpoints of removability and residual adhesiveness of the adherend surface after the removment. , M) is preferably 1 to 30, more preferably 3 to 20.

Examples of such phosphoric acid ester type surfactants include mono (or di) polyoxyethylene nonylphenyl ether ester, mono (or di) polyoxyethylene octylphenyl ether ester, etc. Is mentioned. The monoester represented by the general formula (2a) and the diester represented by the general formula (2b) may be used alone or as a mixture of both.

Such a phosphate ester surfactant of the component d is 0.1 to 3 parts by weight, preferably 0.3 to 2 parts by weight, based on 100 parts by weight of the acrylic copolymer. Used in proportion. If it is less than 0.1 parts by weight, the adhesive strength will increase with time and removability will be poor, and if it exceeds 3 parts by weight, the surface of the adherend will be contaminated and the appearance will be deteriorated. The residual adhesive force on the surface of the adherend after re-peeling tends to be gradually decreased, which is not preferable.

In the present invention, in order to provide a pressure sensitive adhesive layer containing an acrylic copolymer and the above-mentioned phosphoric acid ester-based surfactant on a substrate, the above-mentioned copolymer is synthesized by the above-mentioned polymerization method. At the time of or after its synthesis, the above-mentioned phosphoric acid ester-based surfactant is added, a crosslinking agent is blended if necessary, and a known arbitrary component such as a filler such as an inorganic powder or a metal powder, a pigment or a colorant is blended. Then, the pressure-sensitive adhesive is prepared, and the pressure-sensitive adhesive may be directly applied on the substrate and dried, or applied on a release liner and dried, and then transferred onto the substrate. The thickness of the pressure sensitive adhesive layer is usually 1 to 100 μm.

The re-peelable pressure-sensitive adhesive sheet of the present invention thus produced has a proper initial adhesive force to various adherends, while the re-peelable force is 500 g / 20 mm width or less. , Preferably less than 400g / 20mm width (usually 1g / 2
0 mm width), and the residual adhesive force on the surface of the adherend after re-peeling is 40% or more, preferably 60% or more, more preferably 65% or more (usually up to 80%).

The above-mentioned appropriate initial adhesive strength means, for example,
When the adherend is a stainless steel plate and the pulling speed is 300 mm / min, the 180-degree peel adhesive strength is about 50 to 500 g / 20 mm width, and by having such an initial adhesive strength, By adhering to the surface of the adherend, the adherend can be temporarily and favorably protected. On the other hand, after having achieved this protection purpose, it can be easily repeeled from the surface of the adherend by having the above-mentioned repeeling force.

Moreover, the surface of the adherend after re-peeling is hardly contaminated as shown in the above-mentioned residual adhesive strength, and it is not possible to visually observe any contamination. When the paint is applied to the adherend surface of, there is no risk of cissing or peeling off of this paint,
When a pressure-sensitive adhesive tape is attached to the surface of the adherend for the purpose of adhering different materials or temporarily fixing it, the adhesive tape
There is no risk of problems when the adhesive is difficult to bond.

The initial adhesive force, the re-peeling force, and the residual ratio of the adhesive force after the re-peeling are obtained by combining the acrylic copolymer with the above specific phosphate ester surfactant. In that case, by appropriately selecting the monomer composition and molecular weight of the copolymer, the kind and amount of the cross-linking agent, and the like, the elastic modulus and the solvent-insoluble content of the copolymer may be appropriately determined. Therefore, it can be easily set.

In the present invention, the reason why the addition of the specific phosphoric acid ester-based surfactant gives good results in addition to removability and low contamination on the surface of the adherend after removability is as follows.
Not always clear. It is estimated that the above surfactants have a polyoxyethylene alkylaryl ether group in the molecule, so the amount of leaching and migration to the surface of the adherend is the minimum necessary to obtain removability. On the other hand, in such a slightly leached state, compared to other phosphate ester type surfactants having an aliphatic group such as polyoxyethylene alkyl ether group in the molecule, it is difficult to paint or pressure-sensitive adhesive. This is probably because the effect on tape adhesion is much lower.

[0026]

Next, an embodiment of the present invention will be described in more detail. Hereinafter, “parts” means “parts by weight”.

Example 1 In a reaction vessel equipped with a cooling pipe, a nitrogen introducing pipe, a thermometer and a stirrer, 68 parts of butyl acrylate, 30 parts of butyl methacrylate, 2 parts of acrylic acid, and 2 as a polymerization initiator.
0.1 parts of 2'-azobis (2-amidinopropane) dihydrochloride, 0.3 parts of polyoxyethylene nonylphenyl ether as an emulsifier, 0.3 parts of ammonium polyoxyethylene nonylphenyl ether sulfate and 100 parts of water Then, the emulsion was subjected to emulsion polymerization, and the pH was adjusted to 8 with 10% by weight aqueous ammonia to obtain a polymer emulsion.

This polymer emulsion was mixed with 4 parts of hexamethylol-melamine and 0.5 part of monopolyoxyethylene nonylphenyl ether phosphate per 100 parts of its solid content to prepare a pressure-sensitive adhesive.
This is applied on one side of a base material made of low-density polyethylene film having a thickness of 60 μm so that the thickness after drying becomes 5 μm, and dried at 80 ° C. for 5 minutes, and then the re-peelable pressure-sensitive adhesive tape is applied.
Was prepared.

Example 2 68 parts of butyl acrylate, 30 parts of butyl methacrylate, 2 parts of acrylic acid, and 2 as a polymerization initiator were placed in a reaction vessel equipped with a cooling pipe, a nitrogen introducing pipe, a thermometer and a stirrer.
0.2 part of 2'-azobis (2-amidinopropane) dihydrochloride, 1 part of polyoxyethylene nonylphenyl ether ammonium sulfate as an emulsifier and 10 parts of water
0 parts was added, emulsion polymerization was performed, and the pH was adjusted to 8 with 10% by weight aqueous ammonia to obtain a polymer emulsion.

A pressure-sensitive adhesive was prepared by mixing 4 parts of hexamethylol-melamine and 0.5 part of dipolyoxyethylene nonylphenyl ether phosphate per 100 parts of the solid content of the polymer emulsion. . Using this pressure sensitive adhesive, in the same manner as in Example 1 below,
A releasable pressure-sensitive adhesive tape was prepared.

Example 3 59.5 parts of butyl acrylate, 40 parts of butyl methacrylate, 0.5 part of acrylic acid, and polymerization start were placed in a reaction vessel equipped with a cooling pipe, a nitrogen introducing pipe, a thermometer and a stirrer. 0.2 parts of potassium persulfate as an agent, 0.5 part of polyoxyethylene nonylphenyl ether as an emulsifier, 0.3 part of sodium dodecylbenzenesulfonate and 100 parts of water are added, and emulsion polymerization is performed to obtain 10 parts by weight. The pH was adjusted to 8 with% ammonia water to obtain a polymer emulsion.

A pressure-sensitive adhesive was prepared by mixing 1 part of hexamethylol-melamine and 2.0 parts of monopolyoxyethylene nonylphenyl ether phosphate per 100 parts of the solid content of the polymer emulsion.
Using this pressure-sensitive adhesive, a releasable pressure-sensitive adhesive tape was manufactured in the same manner as in Example 1 below.

Comparative Example 1 The same procedure as in Example 1 was repeated except that 0.3 part of monopolyoxyethylene stearyl etherate was used in place of 0.5 part of monopolyoxyethylene nonylphenyl ester ester. Then, a releasable pressure-sensitive adhesive tape was produced.

Comparative Example 2 A re-peelable pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that the addition amount of monopolyoxyethylene nonylphenyl ether phosphate was changed to 4 parts.

Comparative Example 3 A re-peelable pressure-sensitive adhesive tape was produced in the same manner as in Example 1 except that 0.5 part of monopolyoxyethylene nonylphenyl ether phosphate was not added.

For each of the above-mentioned removable pressure-sensitive adhesive tapes of Examples 1 to 3 and Comparative Examples 1 to 3, the repeeling force and the surface of the adherend after repeeling were measured by the method described in detail in the text. And the residual adhesive strength of The adherend is SUS304BA.
The surface of the adherend to be used for the measurement of the residual adhesive strength was cleaned with a toluene washing method. Next, for each of the above-mentioned re-peelable pressure-sensitive adhesive tapes, the initial adhesive force and the stain resistance of the adherend surface after re-peel were examined by the following measuring methods. The results of these tests are as shown in Table 1 below.

<Measurement of initial adhesive strength> Width 20 mm, length 10
Removable pressure-sensitive adhesive tape of 0 mm is attached to the adherend (SUS30
4BA) and crimp a 2kg roller back and forth once,
After leaving it at 23 ° C for 20 minutes, peel it 180 degrees at a pulling speed of 300 mm / min (at 23 ° C, 65% RH atmosphere),
The force required at this time was defined as the initial adhesive force.

<Measurement of contamination of adherend> As an appearance test,
After the measurement of the initial adhesive strength, the presence or absence of contamination on the surface of the adherend was visually observed, and when no contamination was observed, it was evaluated as ◯, and when it was observed, it was evaluated as x. In addition, as a coating test, a removable pressure-sensitive adhesive tape is attached to an adherend (SUS304BA), stored at 40 ° C. for 7 days, and then peeled. A paint ["Spray for automobile repair S-130 black" manufactured by Nippon Paint Co., Ltd.] is applied to the surface of the adherend after peeling, and 1
Dry for 30 minutes at 50 ° C. After cooling, 100 scratches were cut with a cutter knife at intervals of 1 mm in length and width, and pressure-sensitive adhesive tape [No. manufactured by Nitto Denko Corporation. 29] was attached and peeled off, and the peeled 1 mm ² squares were measured and evaluated by the 10-point method.

Incidentally, the above-mentioned 10-point method means that in 100 squares, Like to evaluate.

[0040]

As is clear from Table 1 above, the re-peelable pressure-sensitive adhesive tapes of Examples 1 to 3 of the present invention have a re-peelability of 330 g / 20 mm width or less and after re-peel. The tape has a residual adhesive force of 65% or more on the surface of the adherend, and each of these tapes has a suitable initial adhesive force and has a low contamination property of the adherend, so that the adherence after re-peel The body surface, of course, has a good appearance, and does not cause cissing or peeling of the paint in the coating test, and as can be seen from the value of the adhesive force residual ratio, the surface of the adherend after re-peeling The pressure-sensitive adhesive tape can be attached well.

On the other hand, the removable pressure-sensitive adhesive tape of Comparative Example 3 containing no phosphate ester type surfactant was
The repeeling force is too large, and repeeling becomes difficult. Further, in the re-peelable pressure-sensitive adhesive tape of Comparative Example 1 using a phosphoric acid ester-based surfactant different from the present invention, the residual adhesive strength after re-peel was too low, and It can be seen that even though the appearance is good, the coating test is significantly inferior and the pressure-sensitive adhesive tape cannot be applied well. Further, even in the case of using the phosphate ester-based surfactant of the present invention, in Comparative Example 2 in which the amount of the surfactant used is excessive, the residual adhesive strength of the adherend surface after re-peeling and the tendency of deterioration of characteristics in the coating test are shown. In addition to the appearance of stains, the appearance of the adherend is significantly deteriorated.

[0043]

As described above, according to the present invention, an acrylic pressure-sensitive adhesive is used as a base, and a specific amount of a phosphoric acid ester-based surfactant is added thereto in a specific amount. The adhesive strength of the product has little increase with time and can be easily re-peeled, and when the paint is applied to the adherend after re-peeling, the paint does not repel or peel off, and the adhesion after re-peeling Removable type useful as a surface protection film, masking tape for painting, adhesive memo, etc. that can develop good adhesion even if a pressure-sensitive adhesive tape is attached to the body for the purpose of adhesion or temporary fixing. Pressure sensitive adhesive sheets can be provided.

Claims (1)

[Claims] 1. In a removable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on a substrate, the pressure-sensitive adhesive layer comprises the following components a to c; _{); CH 2 = CR 1 COOR} 2 ... (1) ( wherein, R ₁ represents a hydrogen or a methyl group, R ₂ is 2 carbon atoms
Acrylate monomer represented by 14 alkyl group) 50 to 99.9% by weight b) Carboxyl group-containing monomer 5 to 0.1% by weight c) Copolymerizable with the above-mentioned components a and b A copolymer of a monomer mixture comprising 45 to 0% by weight of a monomer, and the copolymer 10.
D) General formulas (2a) and (2b) with respect to 0 part by weight; (In the formula, n and m are the number of moles of ethylene oxide added, R
₃ , R ₄ is an alkylaryl group) and 0.1 to 3 parts by weight of a phosphoric acid ester-based surfactant consisting of a phosphoric acid ester or a salt thereof, and a removability of 500 g. A re-peelable pressure-sensitive adhesive sheet having a width of / 20 mm or less and having a residual adhesion rate of 40% or more on the surface of the adherend after re-peeling.