JPH059449A - Rereleasable self-adhesive composition - Google Patents

Abstract

PURPOSE:To provide a highly adhesive rereleasable self-adhesive which can stick to any adherends and has such rereleasability that, after it is applied and exposed to high-temperature and high humidity conditions, it can be released without being left on the surface of the adherend. CONSTITUTION:A rereleasable self-adhesive composition comprising an acryl copolymer prepared by polymerizing 0.01-50wt.% (meth)acrylic acid/alkylene oxide adduct with 0.01-30wt.% (meth)acrylamide monomer and 20-99.8wt.% (meth)acrylic ester other than the above and optionally other polymerizable monomers, wherein at least 50wt.% of the above (meth)acrylamide monomer is added to the reaction system after at least 70wt.% of the total of the other monomers is polymerized.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a re-peelable pressure-sensitive adhesive sheet used for labels / sheets, tapes, building materials, packaging materials, electronics, metal plates, glass plates, synthetic resin plates, laminated steel plates and the like. More specifically, the present invention relates to a pressure-sensitive adhesive composition used for a removable pressure-sensitive adhesive sheet having a function of preventing scratches on the surface of an adherend and a function of preventing dust from adhering.

[0002]

2. Description of the Related Art Conventionally, as a component of a removable pressure-sensitive adhesive, an elastic material such as natural rubber or synthetic rubber or an acrylic resin is blended with a plasticizer, a tackifying resin or a silicone compound to improve the adhesive strength over time. It is known that the rise is suppressed and the removability is facilitated.

However, in the method of adding the above-mentioned additive, the release characteristics are likely to vary, and the compatibility of the (meth) acrylic copolymer, which is the base polymer of the pressure-sensitive adhesive, with the compounding agent is not always good. However, when the adhesive sheet is adhered to the adherend and stored under high temperature and high humidity and then peeled off, a part of the adhesive transfers to the surface of the adherend and has a drawback of contaminating the adherend. Was there.

In order to improve the above-mentioned drawbacks, copolymers obtained by copolymerizing various silicone monomers, copolymers containing silicone macromonomers, and copolymers grafted with polysiloxane resin are used. Removable pressure-sensitive adhesives have been reported, but their compatibility with (meth) acrylic copolymers is not yet good, and none of them have sufficient performance as a removable pressure-sensitive adhesive. Furthermore, these re-peelable pressure-sensitive adhesives treated with silicone have a remarkably low adhesive strength level and a low tackiness (tack), so that they are not generally versatile and are limited in their intended use.

[0005]

DISCLOSURE OF THE INVENTION The present invention overcomes the drawbacks of these conventional acrylic removable pressure-sensitive adhesives and can be attached to any adherend. Provided is a highly adhesive re-peelable pressure-sensitive adhesive having re-peelability capable of being easily peeled off without being left on the surface of an adherend even after peeling after being exposed to It is a thing.

[0006]

According to the present invention, 0.01 to 50% by weight of an alkylene oxide adduct of (meth) acrylic acid and 0.01 to 30 of a (meth) acrylamide monomer are used.
An acrylic copolymer obtained by polymerizing 20% by weight and (meth) acrylic acid ester other than the above, and optionally 20 to 99.8% by weight of another polymerizable monomer, wherein the (meth)
At least 50% by weight of the acrylamide monomer is
It is a removable pressure-sensitive adhesive composition that is added after at least 70% by weight of the total of other monomers is polymerized.

In the present invention, the (meth) acrylic acid alkylene oxide adduct is obtained by adding 1 to 100 mol% of ethylene oxide or propylene oxide to acrylic acid or methacrylic acid,
The following are commercially available products.

Nissan Bremmer PE-250 [Polyethylene glycol (meth) acrylate type (manufactured by NOF CORPORATION) (polyethylene oxide addition mole number 5 to 7)] Nissan Bremmer PP-1000 (Polypropylene glycol (meth) acrylate type manufactured by NOF CORPORATION) (Polypropylene oxide addition mole number 5-6)] Light acrylate MTG-A [Kyoeisha Yushi Co., Ltd. methoxy polyethylene glycol (meth) acrylate type (polyethylene oxide addition mole number 5-6)] NK ester M-90G [Shin Nakamura Chemical Co., Ltd. Methoxy polyethylene glycol (meth) acrylate type (polyethylene oxide addition mole number 9 to 10)] Light acrylate DPM-A [Kyoeisha Yushi Co., Ltd. methoxy polypropylene glycol (meth) acrylate type (po Moles of propylene oxide added 2-3] Aronix M-120 [manufactured by Toagosei Co., Ltd. Special polyethylene glycol (meth) acrylate type (polyethylene oxide addition mol number of 2)

The (meth) acrylic acid alkylene oxide adduct is added in an amount of 0.01 to 30% by weight of the acrylic copolymer. The (meth) acrylic acid alkylene oxide adduct has a function as a cross-linking point of the (meth) acrylamide-based monomer in the acrylic copolymer, and contributes to improvement of the cohesive force of the pressure-sensitive adhesive. Therefore, the lower limit of the above numerical value is
Limited by the cohesive strength of the adhesive, the upper limit of the above value,
Limited by adhesive strength.

The (meth) acrylamide type monomer of the present invention includes the following. N-methylol acrylamide, N-methylol methacrylamide, acrylamide, methacrylamide, butoxymethyl acrylamide and the like. The (meth) acrylamide-based monomer is contained in an amount of 0.01 to 30% by weight of the (meth) acrylic copolymer, preferably 1 to 20% by weight, and one or more types are included. The lower limit of the amount introduced is limited by the function of removability, and the upper limit of the amount introduced is limited by the adhesion to the supporting substrate, the adhesion to the adherend, or the stability of the pressure-sensitive adhesive over time.

In the present invention, the (meth) acrylic acid ester other than those described above has 1 to 14 carbon atoms, preferably 4 to 1 carbon atoms.
There are (meth) acrylic acid alkyl esters with two alkyl groups. For example, the following compounds can be illustrated. Acrylic esters of linear or branched aliphatic alcohols such as methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate and the corresponding methacrylic acid Acid ester etc.

Other monomer components used in the acrylic copolymer of the present invention are carboxyl group, hydroxyl group, methylol group, amino group, glycidyl group,
There are polar group-containing monomers having a phosphoric acid group, a sulfonic acid group, an ethyleneimine group, an isocyanate group and the like. The following compounds are specific examples. Acrylic acid, methacrylic acid, maleic anhydride, maleic acid, maleic acid monoester, itaconic acid, crotonic acid, (meth) acrylic acid 2
-Hydroxypropyl, 2-hydroxyethyl (meth) acrylate, N-methylaminoethyl acrylate, N
-Tributylaminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate, vinylpyrrolidone, glycidyl acrylate, glycidyl methacrylate, mono- (2-hydroxyethyl-α -Chloroacrylate) acid phosphate, vinyl isocyanate and the like. The functional group-containing monomer is 0.01 to 25% by weight of the acrylic copolymer.
It is preferably contained.

The acrylic copolymer of the present invention may contain the following monomers in addition to the above monomer components.
Vinyl ester, vinyl pyridine, vinyl acetate, vinyl propionate, styrene, acrylonitrile, methacrylonitrile, butadiene, chloroprene, etc.

The acrylic copolymer of the present invention is solution-polymerized,
It can be produced by bulk polymerization or the like. As the polymerization initiator, benzoyl peroxide, lauryl peroxide, peroxides such as cumene peroxide,
There are azo compounds such as azobisisobutyronitrile.

The organic solvent used when the acrylic copolymer of the present invention is produced by solution polymerization includes n-pentane, toluene, benzene, n-hexane, dioxane,
Methyl ethyl ketone, methyl isobutyl ketone, methyl acetate, ethyl acetate, butyl acetate and the like, and alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol and butyl alcohol may be mixed.

The acrylic copolymer of the present invention is (meth)
At least 50% by weight of the acrylamide monomer,
It is characterized in that other monomers are added and polymerized after polymerizing at least 70% by weight of the total amount. Examples of such a polymerization method include multi-stage polymerization including two-stage polymerization in which the blending amount of the (meth) acrylamide-based monomer in the continuous drop polymerization is relatively increased in the latter half of the reaction, and 50% by weight of the (meth) acrylamide-based monomer. There is a polymerization method or the like in which a conversion rate of 80% to 95% of another monomer is added at the end of the reaction. If the blending ratio of (meth) acrylamide-based monomer is always constant during polymerization, the cohesive force of the adhesive will be insufficient, and it will be unsatisfactory in terms of the stain resistance to the adherend, which is required for the removable adhesive. Becomes

The pressure-sensitive adhesive composition of the present invention contains an isocyanate compound, a melamine resin, an epoxy resin, an aziridinyl compound, a metal chelate compound, etc. in order to enhance cohesive force due to intermolecular cross-linking and achieve high adhesiveness. You may mix | blend a crosslinking agent. The pressure-sensitive adhesive composition of the present invention may also contain other additives commonly used in pressure-sensitive adhesives.

The pressure-sensitive adhesive composition of the present invention comprises polyester,
5 to 30μ on film substrates such as polypropylene and vinyl chloride or paper substrates such as high quality paper, art paper and coated paper
m is applied. The obtained pressure-sensitive adhesive sheet is used as a pressure-sensitive adhesive for labels / seals, tapes, building materials, packaging materials, and electronics, and especially a surface protective material or masking material that prevents scratches during the processing or transportation of articles. Can be used as

[0019]

EXAMPLES The present invention will be described below with reference to examples. In the examples, “part” means “part by weight” and “%” means “% by weight”.

Example 1 3L4 equipped with a stirrer, thermometer, cooler and dropping funnel
The following monomer was charged in a neck flask, 2-ethylhexyl acrylate 84 parts Vinyl acetate 1 part Bremmer PE-250 (Nippon Yushi Co., Ltd.) 5 parts Azobisisobutyronitrile 0.1 part Ethyl acetate 150 parts Temperature rising with stirring Then, a polymerization reaction was carried out, and 10 parts of acrylic amide was added at the time of the polymerization rate of 90% to obtain a (meth) acrylic polymer. To a solution containing 100 parts of the obtained (meth) acrylic copolymer was added 2 parts of a diisocyanate compound (manufactured by Nippon Polyurethane Company, trade name: Coronate L) to obtain a pressure-sensitive adhesive composition.

Example 2 Solution polymerization was carried out in the same manner as in Example 1 except that the following monomer formulation was used. 2-Ethylhexyl acrylate 57 parts n-Butyl acrylate 15 parts 2-Hydroxyethyl acrylate 1 part Acrylic acid 2 parts Vinyl acetate 10 parts NK ester M-90G (manufactured by Shin-Nakamura Chemical Co.) 8 parts Benzoyl peroxide 1 part Acetic acid Ethyl 220 parts While stirring the monomer, the temperature is raised to carry out a polymerization reaction,
When the polymerization rate was 85%, N-methylolacrylamide 7
Parts were added to obtain a (meth) acrylic polymer. To a solution containing 100 parts of the obtained (meth) acrylic copolymer,
Aziridine compound (Mutual Yakuhin Co., Ltd., trade name: TAZ
M) 0.2 part was blended to obtain a pressure-sensitive adhesive composition.

Example 3 Solution polymerization was carried out with the following monomer formulation changed. 2-Ethylhexyl acrylate 40.5 parts Acrylic acid 2 parts Light acrylate MTG-A (Kyoeisha Yushi Co., Ltd.) 5 parts Glycidyl methacrylate 0.5 parts Methyl acrylate 40 parts Azobisisobutyronitrile 0.2 parts Ethyl acetate Charge 150 parts to a flask, raise the temperature with stirring, and when the temperature reaches 80 ° C., add the above monomer dropwise over 2 hours. At the same time, 12 parts of methacrylamide was added in 6 batches every 1 hour from the start of the reaction to obtain a (meth) acrylic copolymer. A solution containing 100 parts of the obtained (meth) acrylic copolymer was mixed with 0.3 part of an aziridine compound (trade name: TAZO, manufactured by Mutual Chemical Co., Ltd.) to obtain a pressure-sensitive adhesive composition.

Example 4 Solution polymerization was carried out in the same manner as in Example 3 except that the following monomer formulation was used. 2-Ethylhexyl acrylate 68 parts Ethyl acrylate 10 parts Aronix M-120 (manufactured by Toagosei Co., Ltd.) 10 parts 2-Hydroxyethyl acrylate 1 part Itaconic acid 1 part N-Butoxymethylacrylic amide 10 parts Ethyl acetate 160 parts Obtained To a solution containing 100 parts of the obtained (meth) acrylic copolymer, 0.5 part of a diisocyanate compound (Takeda Pharmaceutical Co., Ltd., trade name: Takenate) was added to obtain a pressure-sensitive adhesive composition.

COMPARATIVE EXAMPLE 1 A diisocyanate compound (manufactured by Nippon Polyurethane Co., Ltd.) was added to a solution containing 100 parts of an acrylic copolymer which was subjected to a copolymerization reaction at the same time with other monomers without adding acrylic amide afterwards. Product name: Coronate L)
Two parts were blended to obtain an adhesive composition.

COMPARATIVE EXAMPLE 2 In the monomer formulation of Example 2, a solution containing 100 parts of (meth) acrylic copolymer copolymerized with the remaining monomers excluding the polymerizable alkylene oxide compound was added to the solution containing the aziridine compound ( Mutual medicinal product, product name: TA
ZM) 0.2 part was mix | blended and the adhesive composition was obtained.

Comparative Example 3 In the monomer formulation of Example 3, a solution containing 100 parts of a (meth) acrylic copolymer copolymerized with the remaining monomers except the methacrylamide and the polymerizable alkylene oxide compound was added to a silicone. Macromer (Toagosei Kagaku KK, trade name: HK-20) 7 parts, and aziridine compound (Mutual Yakuhin Co., trade name: TAZO) 0.
3 parts were blended to obtain an adhesive composition.

Comparative Example 4 In the monomer formulation of Example 4, a copolymerization reaction was carried out with the remaining monomers excluding N-butoxymethylacrylamide and the polymerizable alkylene oxide compound (meth).
To a solution containing 100 parts of acrylic copolymer, polyether silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KF61
8) 7 parts and 0.5 parts of a diisocyanate compound (Takeda Pharmaceutical Co., Ltd., trade name: Takenate) were blended to obtain an adhesive composition.

The pressure-sensitive adhesive solution obtained in each example was applied to a surface corona-treated polyester film having a thickness of 25 μm and a commercial cast-coated paper and heat-dried to form a pressure-sensitive adhesive layer having a thickness of 23 to 27 μm. An adhesive sheet having the above was obtained.
The performance test of this pressure-sensitive adhesive sheet is shown in Table 1 (polyester film) and Table 2 (cast coated paper).

[0029]

[Table 1]

[0030]

[Table 2]

The test items are as follows. Initial adhesive strength: Adhesive sheet on a 0.4 mm thick stainless steel plate (SUS304 / No. 1200 polished) at 23 ° C-65%
Stick with RH, roll-tighten according to JIS, and immediately peel strength (180 degree peel,
A pulling speed of 300 mm / min) was measured.

Permanent adhesive strength: According to the initial adhesive strength test, adhered in the same manner as above, and after 24 hours, peel strength (180 degree peel, tensile speed 30 with a Shopper type peel tester).
0 mm / min) was measured.

Adhesion strength with heating: According to the initial adhesion test, the pressure-sensitive adhesive sheet was adhered to a stainless steel plate, left at 70 ° C. for 7 days, and cooled under the condition of 23 ° C.-65% RH.
The peel strength was measured.

Adhesion (tack): Measured by the J.Dow type rolling ball method under the condition of 23 ° C.-65% RH.

Removability of actual sticking: After sticking an adhesive sheet to a stainless steel plate, 23 ° C.-65% RH, 40 ° C.-80% R
Leave at H and 70 ° C for 7 days, 23 ° C-65%
Sensory evaluation of removability (contamination property of adherend, floating phenomenon) after cooling to RH, no floating on the surface sheet, wrinkles and peeling, migration of adhesive after peeling, substrate breakage or adherend Good in terms of contamination is good. ○, wrinkles, floats, etc. are partially generated, but there is no contamination of the adherend or migration of the adhesive. △, wrinkles and floats are noticeable. The case where the adhered object was poorly contaminated was evaluated as x.

Adhesion to surface substrate: The pressure-sensitive adhesive layer applied to the pressure-sensitive adhesive sheet was scratched with a spatula, and the portion was rubbed to perform a mother-child sensory evaluation. The case where the adhesive was not peeled from the surface substrate was evaluated as ◯, the case where the adhesive was slightly peeled but remained on the surface substrate was evaluated as Δ, and the case where the adhesive was completely peeled from the surface substrate was evaluated as x. .

[0037]

EFFECT OF THE INVENTION In the removable pressure-sensitive adhesive of the present invention, an amide group is introduced by the polymerization of the (meth) acrylamide monomer added in the latter half of the polymerization reaction, and the amide group is incorporated into the main chain skeleton by the condensation reaction and the crosslinking reaction. As a result, the contamination of the adherend can be reduced, and the cohesive force can be improved accordingly, resulting in a high adhesive force.

Therefore, the re-peelable pressure-sensitive adhesive of the present invention has an excellent balance between adhesion to a support, adhesion to an adherend and re-peelability. Furthermore, the pressure-sensitive adhesive sheet using the re-peelable pressure-sensitive adhesive of the present invention, after being attached to an adherend, for a long time,
Even if the adhesive is stored under high temperature and high humidity and peeled off, the adhesive does not migrate and contaminate the surface of the adherend.

Claims (2)

[Claims] 1. A (meth) acrylic acid alkylene oxide adduct of 0.01 to 50% by weight, a (meth) acrylamide-based monomer of 0.01 to 30% by weight, and a (meth) acrylic acid ester other than the above and optionally other An acrylic copolymer obtained by polymerizing 20 to 99.8% by weight of a polymerizable monomer, wherein at least 50% by weight of the (meth) acrylamide-based monomer is obtained by polymerizing at least 70% by weight of the total of other monomers, A removable pressure-sensitive adhesive composition that is added. 2. The removable pressure-sensitive adhesive composition according to claim 1, wherein at least one selected from an isocyanate compound, a melamine resin, an epoxy resin, an aziridinyl compound and a metal chelate compound is blended as a crosslinking agent.