JPH08143843A - Repeelable adhesive and its adhesive sheets - Google Patents

Abstract

PURPOSE: To obtain the subject adhesive consisting mainly of an acrylic copolymer comprising a specific monomer composition, light in peeling at a practical peeling speed, little in the increase of adhesive force with time, excellent in peeling workability, and useful for protecting surfaces, etc. CONSTITUTION: This adhesive contains as a main component the copolymer of a monomer mixture comprising 50-94wt.% of an acrylic monomer of the formula: CH2 =C(R<1> )COOR<2> (R<1> is H, methyl; R<2> is a 2-14C alkyl), (B) 35-5wt.% of an N,N-disubstituted (meth)acrylamide of the formula (R<3> is H, methyl; R<4> , R<5> are an alkyl, or both R<4> and R<5> are bound to each other to form a heterocyclic organic group containing N atoms (e.g. N,N-diethyl (meth)acrylamide), (C) 10-1wt.% of a carboxyl group-containing monomer or its anhydride, and (D) 20-0wt.% of a monomer (e.g. vinyl acetate) capable of being copolymerized with the components A-C, and has a gel content of >=70wt.%. The adhesive is preferably crosslinked with a polyvalent epoxy compound or a polyvalent isocyanate compound.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an adhesive for re-peeling which contains an acrylic copolymer as a main component, and a sheet-like or tape-like adhesive for removing the same.
It is related to adhesive sheets in the form of lumps.

[0002]

2. Description of the Related Art Removable adhesive sheets are used for surface protection, masking and the like. Conventionally, as this type of sheet, those in which an acrylic adhesive or a rubber adhesive is applied to one surface of various base materials are known.

[0003]

However, conventionally known releasable pressure-sensitive adhesive sheets are heavy in peeling at a practical peeling speed of about 5 to 50 m / min at room temperature, and their adhesive strength over time. However, there was a problem that the peeling workability was poor and the peeling workability was poor. In order to solve this problem, it is known that the cross-linking density is increased to improve the cohesive force of the pressure-sensitive adhesive so that the pressure-sensitive adhesive is weakly adhered. It is easy to occur.

In view of such circumstances, the present invention is light in peeling at a practical peeling speed, has a small increase in adhesive strength over time, is excellent in peeling workability, and can be attached. An object of the present invention is to provide a pressure-sensitive adhesive for re-peeling that does not show peeling at the end during storage and pressure-sensitive adhesive sheets in the form of sheet or tape.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned object, and as a result, identified an acrylic copolymer having a specific monomer structure as a main component and identified it. By cross-linking structure until the gel content of
The present inventors have completed the present invention by finding that an adhesive for re-peeling and an adhesive sheet thereof, which has excellent peeling workability and does not show peeling at the end during sticking and storage, can be obtained.

That is, the present invention provides the following components a to c or components thereof and d: a) General formula (1): CH ₂ ═C (R ¹ ) COOR ² (wherein R ¹ is hydrogen or a methyl group). , R ² has 2 to 14 carbon atoms
Which is an alkyl group of 50)
~ 94% by weight (Wherein R ³ is hydrogen or a methyl group, R ⁴ and R ⁵ are alkyl groups, or both are bonded to each other and are an organic group forming a heterocycle with the N atom). , N-disubstituted (meth) acrylamide 35-5 wt% c) Carboxyl group-containing monomer or its anhydride 10
1% by weight d) The main component is a copolymer of a monomer mixture consisting of 20 to 0% by weight of a monomer copolymerizable with the above ac components, and the gel content is 70% or more. An adhesive sheet characterized in that it has a characteristic re-peelable adhesive and a layer comprising this re-peelable adhesive on one side or both sides of the substrate, and is in the form of a sheet or tape. -It is related to the kind.

[0007]

The acrylic monomer as the component a in the present invention has, for example, R ² in the general formula (1) of butyl group, isobutyl group, isoamyl group, hexyl group,
Heptyl group, 2-ethylhexyl group, isooctyl group,
Examples thereof include esters of acrylic acid or methacrylic acid having an alkyl group such as an isononyl group and an isodecyl group. When the carbon number of R ² is less than 2, the wettability of the pressure-sensitive adhesive is lowered and the initial adhesiveness is deteriorated, and when the carbon number of R ² exceeds 14, the adhesive strength is deteriorated and both are not preferable.

The acrylic monomer as the component a is
50 to 94% by weight of the total amount of monomers, preferably 60 to 9
One or two or more thereof are used within the range of 0% by weight. If it is less than 50% by weight, the performance as an acrylic pressure-sensitive adhesive cannot be exhibited, and if it exceeds 94% by weight, the absolute amounts of the components b and c described later are insufficient, and the desired adhesive strength and peeling workability are required. No excellent adhesive for re-peeling can be obtained.

The N, N-disubstituted (meth) acrylamide as the component b in the present invention includes R in the general formula (2).
Acyclic (meth) in which both ⁴ and R ⁵ are alkyl groups
It contains acrylamide and cyclic (meth) acrylamide in which R ⁴ and R ⁵ are bound to form a heterocycle with N atom, and either one of them is selected depending on the purpose of use of the adhesive for re-peeling. Or both are used.

Acyclic (meth) acrylamides include N, N-diethyl (meth) acrylamide, N, N
-Dimethyl (meth) acrylamide etc. are mentioned.
Further, as the cyclic (meth) acrylamide, N-
(Meth) acryloylmorpholine, N- (meth) acryloylpyrrolidone, N- (meth) acryloylpiperidine, N- (meth) acryloylpyrrolidine, N- (meth) acryloyl-4-piperidone and the like can be mentioned.

The N, N-disubstituted (meth) acrylamide as the component b is 35 to 5% by weight, preferably 30 to 8% by weight, more preferably 25 to 5% by weight based on the total amount of the monomers.
In the range of 10% by weight, one kind or two or more kinds thereof are used. If it exceeds 35% by weight, the wettability of the pressure-sensitive adhesive will be lowered, and the adhesive force will be lowered.

The carboxyl group-containing monomer or its anhydride as the component c in the present invention is, for example,
Acrylic acid, itaconic acid, maleic acid, crotonic acid and the like, phthalic anhydride and the like, depending on the intended use,
One kind or two or more kinds thereof are appropriately selected and used. The amount used is 10 to 1% by weight of the total amount of monomers, preferably 9 to
The amount is preferably 1.5% by weight, more preferably 8 to 2% by weight. If it exceeds 10% by weight, the tackiness will be poor, and if it is less than 1% by weight, the cohesive force will be insufficient, and in any case, it will be difficult to develop good adhesive properties.

The monomer as the component d in the present invention is
It may be any one that can be copolymerized with the above-mentioned monomers a to c, and examples thereof include vinyl acetate, styrene, glycidyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and (meth) acrylic acid. Methyl, N-vinyl-2
-Pyrrolidone and the like. If necessary, the monomer of the component d may be used alone or in combination of 20% by weight or less, preferably 15% by weight or less based on the total amount of the monomer. If it exceeds 20% by weight, the adhesive property as an acrylic pressure-sensitive adhesive is unlikely to be exhibited.

The acrylic copolymer of the present invention has the above-mentioned a
~ C three components or a monomer mixture consisting of this and the d component, by a conventional method, by copolymerization by a method such as a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization method,
Obtainable.

The re-peelable pressure-sensitive adhesive of the present invention comprises the above acrylic copolymer as a main component and is cross-linked to a gel content of 70% or more, preferably about 75 to 95%. When the gel content is less than 70%, the peeling at a practical peeling speed is heavy, and the adhesiveness with time increases greatly, so that the peeling workability is poor, and it is fatal as an adhesive for re-peeling. There is a problem that adhesive residue is left on the adherend after peeling.

The above-mentioned gel content means the initial weight (G ₀ ) and the insoluble content weight (G _t ) of the adhesive after extraction in acetone at 50 ° C. for 4 hours using a Soxhlet extractor. , [G _t / G ₀ ] × 100 (%).

The cross-linking structure of the pressure-sensitive adhesive may be carried out by a technique such as electron beam irradiation or thermal cross-linking, but preferably, a cross-linking agent is used together with a functional group such as a carboxyl group contained in the copolymer. It is preferable that the so-called cross-linking reaction between functional groups is carried out. Particularly suitable crosslinking agents for this purpose include polyfunctional epoxy compounds and polyfunctional isocyanate compounds.

The polyfunctional epoxy compound has two or more epoxy groups in the molecule, and is sorbitol tetraglycidyl ether, trimethylolpropane glycidyl ether, tetraglycidyl-1,3-bis. Aminomethylcyclohexane, tetraglycidyl metaxylene diamine, triglycidyl-p-aminophenol and the like are available. Polyfunctional isocyanate compounds have two or more isocyanate groups in the molecule, and include diphenylmethane diisocyanate, tolylene diisocyanate, and hexamethylene diisocyanate. is there.

These cross-linking agents may be used alone or in combination of two or more, depending on the composition and molecular weight of the acrylic copolymer, in such a proportion that the gel content of the pressure-sensitive adhesive falls within the above range. At that time, in order to accelerate the reaction, a crosslinking catalyst such as dibutyltin laurate usually used for pressure-sensitive adhesives may be added.

The re-peelable pressure-sensitive adhesive of the present invention may contain a tackifier such as a phenol resin, a coumarone indene resin, or a rosin resin, in addition to the above components. Further, other known additives such as a colorant, a filler and an antiaging agent may be appropriately contained. The gel content of the pressure-sensitive adhesive may be set within the above range for the pressure-sensitive adhesive as a whole including these additives.

The pressure-sensitive adhesive sheets of the present invention are provided with a layer composed of such a pressure-sensitive adhesive for re-peeling on one or both sides of a base material to a desired thickness to form a sheet or tape. It has a shape such as a shape. To provide on the substrate, a solution or dispersion of the re-peeling adhesive is directly applied on the substrate and dried,
Alternatively, the release film may be applied, dried, and then transferred onto a base material. The above-mentioned crosslinking reaction can be carried out during the steps of coating and drying or during the subsequent aging.

As the base material, olefin resin, polyester resin, vinyl chloride resin, vinyl acetate resin,
Various materials such as a plastic film such as a polyimide resin, a non-woven fabric such as a crepe paper and a Japanese paper, and a foamed film are used. These base materials may be used alone or in combination of two or more kinds, and may be those having one surface or both surfaces subjected to surface treatment such as corona treatment.

[0023]

EFFECTS OF THE INVENTION According to the present invention, for various uses for re-peeling such as surface protection and masking, the peeling is light at a practical peeling speed, and the increase in the adhesive strength with time is small, It is possible to provide a pressure-sensitive adhesive for re-peeling and an adhesive sheet thereof, which has excellent workability for peeling and does not show peeling at the terminal during storage by pasting.

[0024]

Next, an embodiment of the present invention will be described in more detail. In the following, "parts" means "parts by weight".

Example 1 80 parts of 2-ethylhexyl acrylate and N- were placed in a reaction vessel equipped with a cooling tube, a nitrogen introducing tube, a thermometer and a stirrer.
20 parts of acryloylmorpholine, 3 parts of acrylic acid, 0.15 parts of 2,2′-azobisisobutyronitrile as a polymerization initiator, 100 parts of ethyl acetate were added, and the mixture was added at 12 ° C. at 12 ° C.
Polymerization was carried out for a period of time to obtain a polymer solution.

This polymer solution was added with 10 parts of polymer solids.
To 0 part, 4 parts of tetraglycidyl-1,3-bisaminomethylcyclohexane was added and mixed, and then coated on a polyethylene film having a thickness of 60 μm and dried to give a thickness of 5 μm. An adhesive tape having a layer of adhesive for peeling was prepared. Separately from this, the sample was coated on a release film and dried to prepare a sample for measuring the gel content, which was used to measure the gel content of the removable pressure-sensitive adhesive by the method described in detail in the text.

Example 2 The polymer solution obtained in Example 1 was mixed with 100 parts of polymer solids.
To 5 parts, add 5 parts tolylene diisocyanate,
After mixing, in the same manner as in Example 1, an adhesive tape having a layer of the removable adhesive having a thickness of 5 μm was produced. In addition, a sample for gel content measurement was prepared in the same manner as in Example 1, and the gel content of the removable pressure-sensitive adhesive was measured using this sample.

Example 3 A polymer solution was obtained in the same manner as in Example 1 except that the monomer composition was changed to 80 parts of n-butyl acrylate, 20 parts of N-isopropylacrylamide and 3 parts of acrylic acid. It was To this polymer solution, 1 part of tetraglycidyl-1,3-bisaminomethylcyclohexane was added to 100 parts of polymer solid content and mixed, and then, in the same manner as in Example 1, the thickness was 5 μm. An adhesive tape having a layer of adhesive for peeling was prepared. In addition, a sample for gel content measurement was prepared in the same manner as in Example 1, and the gel content of the removable pressure-sensitive adhesive was measured using this sample.

Comparative Example 1 Monomer composition was 20 parts ethyl acrylate, n acrylic acid
A polymer solution was obtained in the same manner as in Example 1 except that 80 parts of butyl and 5 parts of acrylic acid were used. To this polymer solution, tetraglycidyl-1,3-bisaminomethylcyclohexane 6 was added to 100 parts of the polymer solid content.
After adding and mixing the parts, a pressure-sensitive adhesive tape having a layer of the pressure-sensitive adhesive for repeeling and having a thickness of 5 μm was prepared in the same manner as in Example 1. In addition, a sample for gel content measurement was prepared in the same manner as in Example 1, and the gel content of the removable pressure-sensitive adhesive was measured using this sample.

Comparative Example 2 Polymer solid content of 100 was added to the polymer solution obtained in Comparative Example 1.
To 7 parts, add 7 parts tolylene diisocyanate,
After mixing, in the same manner as in Example 1, an adhesive tape having a layer of the removable adhesive having a thickness of 5 μm was produced. In addition, a sample for gel content measurement was prepared in the same manner as in Example 1, and the gel content of the removable pressure-sensitive adhesive was measured using this sample.

Comparative Example 3 Polymer solid content of 100 was added to the polymer solution obtained in Example 1.
To 2 parts, add 2 parts tolylene diisocyanate,
After mixing, in the same manner as in Example 1, a pressure-sensitive adhesive tape having a layer of the pressure-sensitive adhesive for peeling having a thickness of 5 μm was produced. Further, a sample for gel content measurement was prepared in the same manner as in Example 1, and the gel content of the removable pressure-sensitive adhesive was measured using this sample.

With respect to each adhesive tape having the layer of the adhesive for removability produced in the above Examples 1 to 3 and Comparative Examples 1 to 3, the following steps were taken, and after the initial storage and after storage by aging by heating, The peeling force was examined, and the workability of peeling after storage over time and the peeling of terminals were examined. The results are shown in Table 1 below together with the gel content of the pressure-sensitive adhesive for repeelability measured in each Example and Comparative Example.
(Examples 1 to 3) and Table 2 (Comparative Examples 1 to 3).

<Peeling force> Each adhesive tape was cut into 20
A test piece having a size of 100 mm × 100 mm was prepared, and the test piece was pressure-bonded to a stainless steel plate and an acrylic resin plate as adherends by a method of reciprocating a 2 Kg roller once and left for 20 minutes. Peeling speed was 0.
The 180 ° peel force was measured under the conditions of 3 m / min and 30 m / min, and the initial peel force shown in the column “A” in the table was used.

A test piece crimped in the same manner as described above was replaced with 50
After storing for 2 days and 7 days in an atmosphere of ° C, the 180 ° peel force was measured in the same manner as above. These measured values were taken as the peeling strength after daily storage due to accelerated heating shown in the columns of "B" (after storage for 2 days) and "C" (after storage for 7 days) in the table.

<Peeling Workability> A test piece pressed onto an adherend as in the case of measuring the peeling force was stored for 7 days in an atmosphere of 50 ° C., and then a practical peeling speed of 30 m.
Peeling was actually performed by hand under the condition of / min, and the quality of the peelability at that time was evaluated according to the following criteria. ◯: Easy peeling with a light force Δ: Peeling is possible, but peeling workability is very poor because a strong force is required ×: Breaking of the base material occurs during peeling, and peeling is impossible

<Terminal Peeling> As in the case of measuring the peeling force, a test piece crimped to an adherend was stored in an atmosphere of 50 ° C. for 7 days, and then the occurrence of floating from the end was visually observed. . The results were evaluated according to the following criteria. ○: No floating was observed. △: Some floating was observed from the end. ×: Large streak or floating was observed from the end.

[0037]

[Table 1]

[0038]

[Table 2]

From the results shown in Tables 1 and 2 above, the pressure-sensitive adhesive tapes having the layers of the pressure-sensitive adhesive for removability of Examples 1 to 3 of the present invention were the same as those of Comparative Examples 1 to 3. Compared to 30m /
Peeling at a practical peeling speed is light, and the increase in adhesive strength over time is small, making it excellent in peeling workability.
Moreover, no peeling of the terminal was observed during the pasting and storage, and it can be seen that it has a very suitable performance for re-peeling.

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[Procedure amendment]

[Submission date] June 7, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

The above gel content is about 500 mg.
An adhesive was prepared as a sample, which was extracted in acetone at 50 ° C. for 4 hours using a Soxhlet extractor,
Alternatively, after soaking in toluene at room temperature for 2 days, 13
After drying at 0 ° C. for 1 hour, from the initial weight (G ₀ ) and the insoluble content weight (G _t ) of the adhesive, [G _t / G ₀ ] × 100 (%)
Is the calculated value.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C09J 133: 02) (72) Inventor Masahiko Ando 1-2 1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Electric Works Co., Ltd.

Claims (3)

[Claims] 1. The following components a to c or components thereof and d; a) General formula (1): CH ₂ ═C (R ¹ ) COOR ² (wherein R ¹ is hydrogen or a methyl group, and R ² is Carbon number 2-14
Which is an alkyl group of 50)
~ 94% by weight (Wherein R ³ is hydrogen or a methyl group, R ⁴ and R ⁵ are alkyl groups, or both are bonded to each other and are an organic group forming a heterocycle with the N atom). , N-disubstituted (meth) acrylamide 35-5 wt% c) Carboxyl group-containing monomer or its anhydride 10
1% by weight d) Mainly composed of a copolymer of a monomer mixture consisting of 20 to 0% by weight of a monomer copolymerizable with the above ac components, and having a gel content of 70% or more Adhesive for re-peeling. 2. The removable pressure-sensitive adhesive according to claim 1, which is crosslinked with a polyfunctional epoxy compound or a polyfunctional isocyanate compound. 3. A pressure-sensitive adhesive sheet having a layer comprising the re-peeling pressure-sensitive adhesive according to claim 1 or 2 on one side or both sides of a base material.