JPH0364385A - Repeelable pressure-sensitive adhesive sheet - Google Patents

Abstract

PURPOSE:To make it possible to repeat adhesion to and peeling from an adherend by coating a release sheet with an emulsion type two-pack crosslinking pressure-sensitive adhesive contg. starch particles and drying it. CONSTITUTION:100 pts.wt. acrylate copolymer obtd. by emulsion-polymerizing 0.1-20wt.% (hereinbelow described as %) ethylenically unsatd. carboxylic acid monomer (e.g. acrylic acid), 50-90% 4-18C alkyl (meth)acrylate monomer [e.g. butyl (meth)acrylate] and 10-50% other monomer copolymerizable therewith [e.g. (meth)acrylic acid] in the presence of an emulsifier, a chain transfer agent and a polymn. initiator in an aq. medium and 0.05-10 pts.wt. polyepoxide compd. type crosslinking agent (e.g. polyethylene glycol diglycidyl ether) are compounded to obtain an emulsion type two-pack crosslinking pressure-sensitive adhesive, with which 40-80% starch particles are compounded to obtain a pressure- sensitive adhesive. Then, a release sheet is coated with this adhesive in a thickness of 5-50g/cm<2>. After it is dried, a surface base material is laminated thereon and, if necessary, it is irradiated with an ionizing radiation of 0.5-5 Mrad.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to metal plates such as stainless steel plates, aluminum plates, and steel plates, painted metal plates, ABS plates, acrylic plates,
A removable adhesive sheet that can be attached to non-metallic plates such as PvC plates and glass plates, as well as paper yarn adherends such as high-quality paper and cardboard, and that can be easily peeled off even after a long period of time, and its production. It is about the method.

[Prior Art] Adhesive sheets are used as labels, sticker patches, etc. in a very wide range of fields such as commercial, office, and household uses.

The general structure of this pressure-sensitive adhesive sheet is a sandwich of pressure-sensitive adhesive between a surface base material and a release sheet.

The surface substrate used is paper, synthetic paper, film, metal foil, etc., and the release sheet is glassine paper, clay coated paper, polylaminated paper, etc. coated with a release agent such as silicone, chemical compound, or fluorine compound. used. Further, as the adhesive, various types of adhesives such as rubber-based, acrylic-based, vinyl ether-based, silicone-based emulsions, and solvent or solvent-free adhesives are used.

These adhesive sheets are of the permanent adhesive type, which remain stuck to the adherend and used permanently after being applied to the product, etc., and others are peeled off and discarded after achieving the purpose of display due to the relationship with the product, etc. There is also a removable type.

Among the above-mentioned adhesive sheets, removable adhesive sheets that are currently in practical use mainly use carboxyl group- and/or hydroxyl group-containing acrylic copolymers as adhesives, and add polyepoxide compounds as crosslinking agents to this. A two-component crosslinking type adhesive has been used in which a carboxyl group and/or a hydroxyl group and an epoxy group are mixed and subjected to a crosslinking reaction.

Such removable adhesive sheets have the disadvantage that if the adhesive sheet is peeled off after a long period of time after being adhered to a Gi type adherend, the surface substrate may be destroyed or the adhesive may remain on the adherend. be.

Recently, a type in which adhesive microspheres are directly applied to the surface substrate, and a type in which elastic microspheres are added to the adhesive described in Japanese Utility Model Application Publication No. 168146/1983, are used to coat the surface of the elastic microspheres with an adhesive layer on the surface substrate. 2. Description of the Related Art A type of adhesive sheet configured to cover various adherends is attracting attention as a removable adhesive sheet that can be repeatedly attached and peeled off from various adherends. However, with such adhesive sheets, if the adhesive is applied by transfer method, sufficient anchoring force and adhesion force cannot be obtained between the surface substrate and the adhesive, so it is not possible to apply the adhesive directly to the surface substrate. It is manufactured by engineering. In production by this direct coating method, if the surface base material is thermal paper or special paper such as cast-coated paper, there are problems such as unnecessary color development and reduced gloss during coating and drying. For this reason, the surface base materials currently in practical use are limited to high-quality paper.

[Problem to be solved by the invention]

An object of the present invention is to provide a removable adhesive sheet that can obtain sufficient anchoring force and adhesion between the surface base material and the adhesive, and can be repeatedly attached and peeled off from various adherends. It is something to do.

[Means to solve the problem]

The present invention provides a pressure-sensitive adhesive sheet in which an emulsion-based two-component cross-linked pressure-sensitive adhesive is coated on a release sheet, dried, and then laminated with a surface base material. This is a removable pressure-sensitive adhesive sheet characterized by containing ~80% by weight.

[Effect]

In the present invention, the emulsion-based two-component crosslinking adhesive applied to the release sheet includes monomers containing ethylenically unsaturated carboxylic acid, C, alkyl ester monomers of (meth)acrylic acid, etc. The target is an acrylic acid ester copolymer whose constituent monomers are other monomers that can be copolymerized with this monomer, and a crosslinking agent and starch granules are blended therein.

Examples of the ethylenically unsaturated carboxylic acid-containing monomer constituting the acrylic ester copolymer used in the present invention include acrylic acid, methacrylic acid, crotonic acid,
Examples include maleic acid, fumaric acid, monoalkyl maleic acid, monoalkyl itaconic acid, monoalkyl fumaric acid, and the like.

The proportion of these ethylenically unsaturated carboxylic acid-containing monomers in the copolymer needs to be in the range of 0.1 to 20% by weight. Incidentally, if it is less than 0.1% by weight, crosslinking properties will be insufficient, and if it exceeds 20% by weight, the stability of adhesive performance over time will decrease.

On the other hand, (meth)acrylic acid constituting the acrylic acid ester copolymer used in the present invention has 04 to .

Examples of alkyl ester monomers include butyl (meth)acrylate, hexyl (meth)acrylate, and (meth)acrylate.
Examples include octyl acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate.

04 of these (meth)acrylic acids in the copolymer
The proportion of ~Il+alkyl ester monomer is copolymerized in the range of 50 to 90% by weight of the total monomers, taking into account the glass transition temperature of the adhesive.

In the present invention, C4 of these (meth)acrylic acids
Among the +l 11 alkyl ester monomers, butyl acrylate, 2-ethylhexyl acrylate, and the like are particularly preferably used in terms of copolymerizability, glass transition temperature, and the like.

In addition, other monomers that can be copolymerized with the above-mentioned monomers constituting the acrylic ester copolymer used in the present invention include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, (meth)propyl acrylate, vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, (meth)acrylonitrile, styrene, ethylene, cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylate Acrylic acid-
2-hydroxypropyl, 3-chloro-2-hydroxypropyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, (
Dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, diethylene glycol (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate,
Triethylene glycol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate , di(meth)acrylic acid (poly)propylene glycol, di(meth)acrylic acid-1,
3-butylene glycol, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, divinylbenzene, 1,4-butanediol di(meth)acrylate, di(meth)acrylic acid-1 , 6-hexanediol, glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide,
N-butoxymethyl(meth)acrylamide, N.

Examples include N'-methylenebis(meth)acrylamide and the like.

The proportion of these other copolymerizable monomers in the copolymer is adjusted within the range of 10 to 50% by weight of the total monomers.

In the present invention, among these other copolymerizable monomers, methyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid-
2-hydroxypropyl, 3-chloro-2-hydroxypropyl (meth)acrylate, (meth)acrylonitrile, (meth)acrylamide, and the like are preferably used in terms of crosslinkability, glass transition temperature, adhesive performance, and the like.

The acrylic ester copolymer of the present invention is produced by emulsion polymerization of each monomer as described above in an aqueous system in the presence of an emulsifier, a chain transfer agent, a polymerization initiator, and the like.

The pressure-sensitive adhesive of the present invention is a two-component crosslinking type adhesive in which a polyepoxide compound-based crosslinking agent is blended with the above-mentioned acrylic ester copolymer.

The polyepoxide compound crosslinking agent used in the present invention contains two or more epoxy groups, such as polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether,
Neopentyl glycol diglycidyl ether, 1.6
-hexanesiol diglycidyl ether, dibromoneopentyl glycol diglycidyl ether, diglycidyl phthalate, glycerol polyglycidyl ether,
Trimethylolpropane polyglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, N,N-diglycidylaniline, N,N-diglycidyltoluidine, m-N,N-diglycidylaminophenyl Glycidyl ether, p-N, N-diglycidyl aminophenyl glycidyl ether, triglycidyl isocyanurate, N, N, N', N'-tetraglycidylethylenediamine, N, N, N'N'-tetraglycidyldiaminodiphenylmethane, N ,N,N'
, N'-tetraglycidyl-m-xylylenediamine, N,N,N',N'N'-pentaglycidyldiethylenetriamine, and the like.

The proportion of these crosslinking agents in the adhesive layer is 0.05 to 1 part by weight based on 100 parts by weight of the acrylic ester copolymer.
It is adjusted within a range of 0 parts by weight. This blending ratio is 0.05
If the amount is less than 10 parts by weight, the crosslinking property and removability will be insufficient, and if it exceeds 10 parts by weight, the adhesive performance will be extremely poor and it will be impractical.

Next, the starch granules to be added to the adhesive layer, which is the most characteristic feature of the present invention, include corn starch, potato starch, wheat starch, kubioka starch, sago starch, etc. In the present invention, any of these starch granules can be used. Moyo (, two or more types may be used together.

Furthermore, in order to exhibit the effects of the present invention, it is necessary to add starch in a granular layer.

The proportion of starch granules in the adhesive layer is adjusted within the range of 40 to 80% by weight of the solid content of the adhesive layer. If the blending ratio is less than 40% by weight, the adhesive strength will be too high and sufficient removability will not be obtained for adherends such as paper. On the other hand, if it exceeds 80% by weight, the adhesive force will be extremely reduced before the crosslinking reaction, and sufficient anchoring force and adhesion force to the substrate will not be obtained during transfer to the surface substrate.

At present, it is not clear why a pressure-sensitive adhesive sheet with excellent removability is obtained when starch granules are added and mixed in a range of 40 to 80% by weight of the solid content of the pressure-sensitive adhesive layer, but When viewed under magnification with a microscope, the present inventors can observe many porous richnesses.The inventors found that the generation of these porous richnesses reduces the contact area between the adhesive and the adherend, which leads to re-peelability. I think that it may give rise to aptitude.

Examples of the surface base material used in the present invention include paper, synthetic paper,
Film, metal foil, etc. can be used.

The release sheet can be made of high-density base paper such as glassine paper, clay-coated paper, or polylaminated paper made by laminating polyethylene, etc. on high-quality kraft paper, and a solvent-based fluororesin or silicone resin of 0.05% by dry weight. ~3g/
A release agent layer is used which is coated with a coating of about 100 ml and coated with a release agent layer by heat curing, ionizing radiation curing, etc.

The adhesive used in the method of the present invention is usually adjusted to a viscosity of about 3,000 to 8,000 centivoise by adjusting the molecular weight of the acrylic ester, diluting with water, or thickening, and then applied to the release sheet. However, as the coating device, for example, a roll coater, knife coater, bar coater, slot die coater, etc. are used. The amount of adhesive applied to the release sheet is 5 to 50 g/dry weight.
It is desirable to adjust within the range of 5g/r.
If it is less than f, the adhesive force of the pressure-sensitive adhesive layer of the obtained pressure-sensitive adhesive sheet will not be sufficient, and if it exceeds 50 g/rrl, it will cause the pressure-sensitive adhesive sheet to protrude when placed or cause cohesive failure during peeling.

According to the present invention, by providing a pigment-containing undercoat layer between the surface base material and the adhesive layer, the adhesive remains on the adherend even after repeated attachment and peeling. Therefore, the above configuration is one of the preferred embodiments.

The reason why such an effect can be obtained by providing an undercoat layer containing a pigment is not necessarily clear, but when a pigment is included in the undercoat layer, an anchoring effect is exerted between it and the adhesive layer. It is thought that this may be the case.

As the pigment to be contained in the undercoat layer, ordinary inorganic or organic pigments can be used. Specifically, for example, oxides of various metals such as magnesium, calcium, zinc, barium, titanium, aluminum, antimony, and lead, water, etc. Examples thereof include oxides, sulfides, carbonates, sulfates, or silicate compounds, and solid polymer fine powders such as polystyrene, polyethylene, and polyvinyl chloride. Among them, kaolin, talc, silica,
When inorganic pigments such as gypsum, pallite powder, alumina white, gloss white, satin white, titanium oxide, calcium carbonate, acid clay, activated clay, etc. are used, ionic interaction with the adhesive layer is added, making it more effective. The anchoring effect is exerted.

The amount of pigment contained in the undercoat layer is desirably 90% by weight or less, more preferably 80% by weight or less of the total solid content constituting the undercoat layer. Incidentally, if it exceeds 90% by weight, there is a risk that the bonding force between the undercoat layer and the surface substrate will be insufficient and the pigment will fall off.

A binder is used in the undercoat layer as a material for fixing pigments to each other or to the undercoat layer and the surface substrate. Examples of such binders include casein, dextrin, starch, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, Polyvinyl alcohol, styrene-butadiene copolymer, methyl methacrylate-butadiene copolymer,
Natural or synthetic resin binders such as ethylene/vinyl chloride copolymer, ethylene/vinylidene chloride copolymer, acrylic acid ester copolymer, ethylene/vinyl acetate copolymer, etc. are used in the form of an aqueous solution or dispersion. . In addition to pigments, various auxiliary agents such as antifoaming agents and dispersants may be added to the undercoat layer as long as the properties thereof are not impaired, depending on the purpose.

The coating liquid for the undercoat layer containing the pigment can be applied to the surface substrate using a conventional coating machine such as an air knife coater, blade coater, roll coater, bar coater, etc., and the coating amount is determined by the solid content. 2g/rrr or more,
Preferably, 5 to 10 g/M is applied. By the way, 2g
If it is less than /rrf, sufficient bonding of the adhesive to the surface substrate cannot be expected, and if it exceeds 10 g/rrf, it is not necessary from an economic standpoint.

In the method of the present invention, a pressure-sensitive adhesive sheet is manufactured by drying the pressure-sensitive adhesive coated on a release sheet with hot air and then bonding the surface base material to the surface base material. This is one of the preferred embodiments because the crosslinking reaction of the agent proceeds immediately and it is possible to obtain a pressure-sensitive adhesive sheet that can exhibit stable removability immediately after the pressure-sensitive adhesive sheet is manufactured.

As the ionizing radiation, ultraviolet rays, electron beams, gamma rays, etc. are used, and electron beams are particularly preferred in terms of transparency, energy efficiency, and ease of handling.

The dose of ionizing radiation is preferably in the range of 0.5 to 5 Mrad. Incidentally, Q: Below 5 Mrad, the effect is poor, and above 5 Mrad, when the adhesive is sandwiched between the surface base material and the release sheet and is irradiated, the release agent decomposes and the releasability decreases. This is because this will lead to further deterioration of the support.

〔Example〕

The method of the present invention will be explained in more detail with reference to Examples below, but it is of course not limited thereto. The coating amount, number of parts, mixing ratio, etc. in the layer are all expressed in terms of solid content.

Example 1 An emulsified monomer mixture containing 80% by weight of 2-ethylhexyl acrylate, 5% by weight of acrylic acid, 5% by weight of vinyl acetate, and 10% by weight of methyl methacrylate was prepared.

Next, the initiator aqueous solution was charged into a four-loaf flask equipped with a stirrer, cooler, dropping funnel, nitrogen suction pipe, and thermometer.
After raising the temperature to 70° C. while purging with nitrogen, 1/6 of the emulsified monomer mixture was added dropwise. When the reaction rate reached 90%, the remaining emulsified monomer mixture was added dropwise over 3 hours to polymerize.

After completion of the dropwise addition, the mixture was aged at 80''C for 2 hours to complete the reaction.

Polyethylene glycol diglycidyl ether (
Prepared by Nagase Chemical Industries; Product name: “Bunacol EX-830”
J) 1.5 parts by weight were added and mixed.

Wheat starch granules (Glyco nutritional food preparation; trade name [
Glyco BJ) was dispersed in water at a ratio of 50% by weight, and 60% by weight of the adhesive was added and mixed by stirring. This adhesive composition was applied to a commercially available polyethylene laminate release paper at a solid content of 25 g/rd and dried. Furthermore, on the surface of this adhesive layer, a commercially available 64 g/
rrr high quality paper was bonded together and heat treated at 40°C for 7 days to produce a removable adhesive sheet.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Example 2 A removable pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the mixing ratio of starch granules was 40% by weight based on the pressure-sensitive adhesive.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Example 3 As a surface base material, a pigment dispersion having the following composition was applied as an undercoat layer on the back side of a high-quality paper with a basis weight of 64 g/rrf to a dry weight of 5 g/rd using an air knife coater and dried. A removable pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the adhesive sheet was used.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Kaolin 60 parts Light calcium carbonate 25 parts Acrylic acid
・Butadiene ・Methyl methacrylate copolymer latex
15 parts Example 4 In Example 1, the surface substrate was subjected to electron beam irradiation treatment at an accelerating voltage of 175 kV and a dose of 3 Mrad to produce a removable pressure-sensitive adhesive sheet.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Example 5 As an acrylic emulsion type adhesive, 100 parts by weight of an acrylic ester copolymer emulsion (made by Japan Synthetic Rubber; trade name: rSX245(A)-01J) was mixed with a polyepoxide compound (made by Japan Synthetic Rubber; trade name: rs).
X291(A)-01J) A removable adhesive sheet was produced in the same manner as in Example 1, except that an adhesive containing 1 part by weight was used.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Example 6 A removable adhesive sheet was produced in the same manner as in Example 2 except that the same adhesive as in Example 5 was used.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Example 7 A removable adhesive sheet was produced in the same manner as in Example 3 except that the same adhesive as in Example 5 was used.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Example Day A removable adhesive sheet was produced in the same manner as in Example 4 except that the same adhesive as in Example 5 was used.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Comparative Example 1 Acrylic ester copolymer emulsion (prepared by Japan Synthetic Rubber; trade name r 5X245 (^)-01J)
An adhesive prepared by adding 1 part by weight of a polyepoxide compound (manufactured by Japan Synthetic Rubber; trade name rsX291(A)-01J) to 100 parts by weight was applied to commercially available polyethylene laminate release paper at a solid content of 25 g/rd. Dry. Furthermore, on the surface of this adhesive layer, commercially available Tsubo 164
A removable pressure-sensitive adhesive sheet was produced by laminating g/bo high-quality paper together and heat-treating at 40°C for 7 days.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Comparative Example 2 A removable pressure-sensitive adhesive sheet was produced in the same manner as in Example 5, except that the mixing ratio of starch granules to the pressure-sensitive adhesive was 20% by weight.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Comparative Example 3 A removable pressure-sensitive adhesive sheet was produced in the same manner as in Example 5, except that the mixing ratio of starch granules was 80% by weight based on the pressure-sensitive adhesive.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Comparative Example 4 As an acrylic emulsion type adhesive, a one-component removable adhesive (prepared by Saiden Chemical Co., Ltd.; trade name: "Cypinol 9") was used.
A removable pressure-sensitive adhesive sheet was produced in the same manner as in Example 5 except that 9EJ) was used.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Comparative Example 5 As an acrylic emulsion type adhesive, a microspherical removable adhesive (produced by Toyo Ink: trade name "Olivine BP") was used.
A removable adhesive sheet was produced in the same manner as in Comparative Example 1 except that W4960-I J'') was used, but the adhesive was not transferred to the surface substrate.

The adhesive performance of this removable adhesive sheet was as shown in Table 1.

Table 1 Note) Adhesive strength: Adhesive strength to stainless steel plates, PVC plates, and cardboard was measured according to the 180° peeling method specified in Is Z 0237.

(Unit: g/25m) Re-peelability: The adhesive sheet was cut to 25111 x 90M, and after peeling off the release paper, it was pressed against a stainless steel plate, a PVC plate, and a cardboard by moving it back and forth 10 times with a 2 kg roller. After 2 hours, the specimens were peeled off at a speed of 50 m/min.

○: No adhesive remains on the adherend.

63 Although the surface base material was somewhat destroyed, A level that poses no practical problems.

×; Adhesive completely remains on the adherend Ta.

Air adhesion property: After peeling off the release paper from the adhesive sheet, the surface of the adhesive layer was rubbed with a fingertip and the adhesive was observed to come off.

Crosslinking days: The number of days required for the crosslinking reaction to complete.

〔effect〕

The removable adhesive sheet according to the present invention has excellent removability that can obtain sufficient anchoring force and adhesion between the surface base material and the adhesive, and can be repeatedly applied and peeled off from various adherends. It is an adhesive sheet.

Claims (4)

[Claims] (1) In a pressure-sensitive adhesive sheet formed by coating a release sheet with an emulsion-based two-component cross-linked pressure-sensitive adhesive and drying it, and then laminating a surface base material, starch granules are added to the pressure-sensitive adhesive layer in an amount of 40 to 40% of the solid content of the pressure-sensitive adhesive layer. A removable adhesive sheet characterized by containing 80% by weight. (2) The adhesive contains (a) an ethylenically unsaturated carboxylic acid-containing monomer of 0.1
~20% by weight (b) 50~90% by weight of C_4_~_1_■ alkyl ester monomers of (meth)acrylic acid (c) 10% by weight of other monomers copolymerizable with these monomers
Claim (1) characterized in that it is an emulsion-based two-component cross-linking adhesive in which a polyepoxide compound-based cross-linking agent is blended with an acrylic acid ester copolymer having the above monomer composition of ~50% by weight. The removable adhesive sheet described. (3) The removable pressure-sensitive adhesive sheet according to claim 1, further comprising an undercoat layer containing a pigment between the surface base material and the pressure-sensitive adhesive layer. (4) A removable pressure-sensitive adhesive sheet according to claim (1), characterized in that an emulsion-based two-component cross-linked pressure-sensitive adhesive is coated on the release sheet, dried, laminated with a surface base material, and then irradiated with ionizing radiation. .