JP2011190419A - Water-based removable type adhesive and adhesive tape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based removable type adhesive usable for an adhesive tape having excellent adhesiveness to a rough surface of corrugated board etc., and readily releasable from the surface of an adherend even after being allowed to stand at high temperatures and high humidities over a long period of time after application to the adherend. <P>SOLUTION: The water-based removable type adhesive includes: an acrylic resin (A); and a curing agent (B). In the water-based removable type adhesive, the stress value at 200% strain in a stress-strain curve of a dried film formed from the water-based removable type adhesive, and having a cross-sectional area of 4 mm<SP>2</SP>is 0.01-0.03 N/mm<SP>2</SP>; the strain at the maximum stress is 800-1,300%; and the maximum stress value is 0.04-0.08 N/mm<SP>2</SP>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention can be used for pressure-sensitive adhesive labels, masking tapes and sheets, surface protection films, etc., has excellent adhesiveness, and is left for a long time after being attached to various adherends (metal plate, glass, plastic plate, paper, etc.) However, the present invention relates to an aqueous re-peelable pressure-sensitive adhesive that can be easily peeled and a pressure-sensitive adhesive tape using the same.

  Conventionally, a strong adhesive type adhesive has been used for price tag labels, courier address labels, and the like so that the labels do not peel off during use. However, the adhesiveness to the adherend is excessively increased over time after the label is pasted, and therefore, adhesive residue and tearing of the paper base material occurred when peeling off later.

Therefore, a re-peelable pressure-sensitive adhesive has been conventionally proposed so that it can be easily peeled off from the adherend.
Patent Document 1 includes a crosslinkable monomer and a water-soluble azo polymerization initiator, an acrylic copolymer having an average particle size of 100 nm or less, and water resistance by blending a crosslinking agent having an aziridine group. An aqueous emulsion-type pressure-sensitive adhesive having excellent wet heat resistance and excellent removability without contaminating the adherend surface has been disclosed. However, this pressure-sensitive adhesive has an excessively high crosslinking density, and cannot provide adhesiveness to rough surfaces such as cardboard.

  Patent Document 2 discloses an emulsion type oxazoline as a crosslinking agent for an acrylic copolymer crosslinked with a high gel fraction of 70% or more using a crosslinking monomer and an anionic reactive surfactant. There has been disclosed a re-peelable water-based pressure-sensitive adhesive composition in which an increase in adhesive force with time is small by blending a system compound and excellent in stain resistance to an adherend during re-peeling. However, this pressure-sensitive adhesive has a high cohesive force and further uses a cross-linking agent, so that the cross-linking density becomes too high and, for example, the pressure-sensitive adhesiveness to rough surfaces such as cardboard cannot be obtained.

  Patent Document 3 includes a tackifier resin and an epoxy crosslinking agent as essential components for an acrylic copolymer containing a specific amount of butyl acrylate, an unsaturated carboxylic acid and a reactive surfactant. It is disclosed that an adhesive sheet with good removability can be obtained while having strong adhesive strength. However, this pressure-sensitive adhesive has a problem that the removability after aging at high temperature and high humidity deteriorates.

Japanese Patent Laid-Open No. 6-25630 JP 2004-256789 A JP 2009-24130 A

  The present invention is used for an adhesive tape that has excellent adhesion to rough surfaces such as corrugated cardboard and can be easily peeled off from the surface of the adherend even after being left for a long time at high temperature and high humidity after being attached to the adherend. An object is to provide a water-based re-peelable pressure-sensitive adhesive.

The present invention is an aqueous re-peelable pressure-sensitive adhesive containing an acrylic resin (A) and a curing agent (B),
The stress value at the time of 200% strain in the stress-strain curve of a dry film having a cross-sectional area of 4 mm ² formed from the water-based re-peelable pressure-sensitive adhesive is 0.01 to 0.03 N / mm ²
The present invention relates to a water-based re-peelable pressure-sensitive adhesive having a strain at a maximum stress of 800 to 1300% and a maximum stress value of 0.04 to 0.08 N / mm ² .

Further, the present invention provides a monomer mixture in which the acrylic resin (A) contains at least 2-ethylhexyl acrylate (A-1) and butyl acrylate (A-2) in a total amount of 90.0 to 99.9% by weight. Copolymerized using a peroxide and a reducing agent as a polymerization initiator in the presence of a non-reactive surfactant,
The weight ratio of (A-1) / (A-2) is 55 / 45-25 / 75,
The curing agent (B) is an epoxy compound, and further contains a polyol (C), and relates to the aqueous re-peelable pressure-sensitive adhesive according to the invention described above.

  The present invention also relates to an aqueous re-peelable pressure-sensitive adhesive characterized in that the ethyl acetate extraction residue of a dry film formed from the water-based re-peelable pressure-sensitive adhesive of the invention is 45 to 75% by weight.

  The present invention also relates to the water-based re-peelable pressure-sensitive adhesive according to the invention, wherein the dry film formed from the acrylic resin (A) has a weight average molecular weight of 25 to 450,000 for the elution of tetrahydrofuran.

  Moreover, this invention relates to the adhesive tape containing the adhesive layer formed from the water-system re-peeling type adhesive of the said invention.

  According to the present invention, it is excellent in adhesiveness to rough surfaces such as corrugated cardboard and used for an adhesive tape that can be easily peeled off from the adherend surface even after being left for a long time at high temperature and high humidity after being attached to the adherend. It was possible to provide a water-based re-peelable pressure sensitive adhesive.

The inventor of the present application controls the initial stress value in the stress-strain curve and the maximum stress value in the subsequent strain (elongation) within a predetermined range, so that the adhesiveness to the rough surface and the high temperature and high humidity after aging It was found that re-peelability can be compatible.
That is, the present invention relates to an aqueous re-peelable pressure-sensitive adhesive containing an acrylic resin (A) and a curing agent (B), and a dry film having a cross-sectional area of 4 mm ² formed from the aqueous re-peelable pressure-sensitive adhesive. It is important that the stress value at the time of 200% strain, which is the initial stress value in the stress-strain curve, is 0.01 to 0.03 N / mm ² . Here, when the stress value is less than 0.01 N / mm ² , the adhesive sheet may fall off or float during or after the high temperature and high humidity. If it exceeds 0.03 N / mm ² , the paper may be torn when a paper base material is used for the pressure-sensitive adhesive sheet.

  In the present invention, the stress-strain curve is a curve showing the relationship between the stress applied to the pressure-sensitive adhesive layer and the amount of deformation (strain) caused by the stress. It is assumed that there is a correlation between the stress-strain curve of the adhesive and the removability.

  Here, in the present invention, the adhesive strength refers to a value measured by a tensile tester or the like after the adhesive tape has been applied to the adherend, and the adhesiveness refers to the adhesion of the adhesive tape after the adhesive tape has been applied to the adherend. It means adhesion to the body.

In the present invention, it is further necessary that the pressure-sensitive adhesive layer is appropriately distorted (elongated) and the stress value corresponding to the distortion is within an appropriate range. That is, it is important that the strain at the maximum stress per cross-sectional area of 4 mm ² is in the range of 800 to 1300% and the maximum stress value is in the range of 0.04 to 0.08 N / mm ² . On the other hand, if the numerical range is not satisfied, the removability may be insufficient.

In the present invention, the relationship between stress and strain is measured by the following method.
1. A pressure-sensitive adhesive is coated on the release sheet so that the dry thickness of the pressure-sensitive adhesive layer is 0.05 mm, and dried at 100 ° C. for 3 minutes. Further, three 0.05 mm coated products are prepared in the same operation. Then, a total of four coated products are bonded so that bubbles do not enter, and a 0.2 mm thick adhesive coated product is created. When bubbles are mixed, it can be degassed by autoclaving.
2. A test sample is cut into a size of width 20 mm, length 24 mm, thickness 0.2 mm.
3. A test sample is fixed to a tensile tester (EZ TEST, manufactured by Shimadzu Corporation), and stress [N / mm ² ] and strain [%] are obtained by pulling at 300 mm / min. Measurement atmosphere is temperature; 23 degreeC, humidity; 55% RH.
4). The stress [N / mm ² ] is the strength per cross-sectional area of the sample, and can be obtained from the measured tensile strength [N], sample thickness [mm], and sample width [mm].
5. Create a graph with the stress [N / mm ² ] obtained in 3 above as the y-axis and the strain [%] as the x-axis. From the graph, the stress value at the time of 200% strain, the strain at the maximum stress, and the maximum stress value The numerical value of each parameter such as maximum distortion is obtained.

The acrylic resin (A) used for the aqueous re-peeling adhesive of the present invention will be described.
The acrylic resin (A) is obtained by emulsion polymerization of an ethylenically unsaturated monomer mixture containing a carboxyl group-containing ethylenically unsaturated monomer and other ethylenically unsaturated monomers.

As an ethylenically unsaturated monomer, specifically, for example,
Acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, acrylate-2-ethylhexyl;
Methacrylate esters such as ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate;
Various unsaturated group-containing carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, 2-methacryloylpropionic acid;
Aromatic monomers such as styrene, α-methylstyrene, benzyl methacrylate;
Vinyl esters such as vinyl acetate and vinyl propionate;
Heterocyclic vinyl compounds such as vinylpyrrolidone;
Α-olefins such as ethylene and propylene;
Dienes such as butadiene;
Glycidyl group-containing monomers such as glycidyl methacrylate and allyl glycidyl ether;
Hydroxyl group-containing monomers such as 2-hydroxyethyl methacrylate;
Amino group-containing monomers such as dimethylaminoethyl methacrylate;
Carboxylic acid amide group-containing monomers such as acrylamide;
Unsaturated bond-containing silane compounds such as dimethylvinylmethoxysilane;
Cyano group-containing monomers such as acrylonitrile;
Polyfunctional vinyl monomers such as divinylbenzene;
And so on.

In the present invention, it is preferable to use 2-ethylhexyl acrylate (A-1) and butyl acrylate (A-2) in combination as the other ethylenically unsaturated monomers. The use ratio is preferably 90.0 to 99.9% by weight in 100% by weight of all monomers.
Furthermore, the weight ratio of (A-1) / (A-2) is preferably 55/45 to 25/75. When butyl acrylate (A-2) is less than 45% by weight, the substrate may be broken during re-peeling when used as an adhesive tape for a paper substrate. On the other hand, when it exceeds 75% by weight, there is a possibility that adhesive residue may be generated on the adherend.

  The glass transition temperature of the acrylic resin (A) of the present invention is preferably −70 to −10 ° C., more preferably −65 to −50 ° C. When the glass transition temperature is higher than −10 ° C., the anchoring property to the paper substrate and the adhesiveness to the adherend are likely to be insufficient. On the other hand, if the glass transition temperature of the acrylic resin (A) is lower than -70 ° C, the removability may be deteriorated in a high temperature atmosphere. In the present invention, the anchoring property means the adhesiveness of the pressure-sensitive adhesive layer to the substrate.

The glass transition temperature (Tg) of the acrylic resin (A) in the present invention is theoretically derived from the following formula [I].
1 / Tg = [(W1 / Tg1) + (W2 / Tg2) +... (Wn / Tgn)] / 100 [I]
However,
W1: wt% of monomer 1, Tg1: glass transition temperature (° K) of a homopolymer that can be formed from monomer 1 alone,
W2: wt% of monomer 2, Tg2: glass transition temperature (° K) of homopolymer that can be formed from monomer 2 alone,
Wn:% by weight of monomer n, Tgn: glass transition temperature (° K) of a homopolymer that can be formed only from monomer n,
(W1 + W2 + ... + Wn = 100)
When using an ethylenically unsaturated monomer having an ethylenically unsaturated group as a surfactant when polymerizing the ethylenically unsaturated monomer in an aqueous medium, In calculating the Tg of the copolymer, a surfactant having an ethylenically unsaturated group is not included in the monomer.
And the following numerical value was used for the glass transition temperature of the monomer used by this invention. Acrylic acid (106 ° C), methacrylic acid (186 ° C), methyl methacrylate (105 ° C), methyl acrylate (8 ° C), ethyl acrylate (-22 ° C), butyl acrylate (-52 ° C), acrylic acid They are 2-ethylhexyl (-70 degreeC), styrene (100 degreeC), and 2-hydroxyethyl methacrylate (55 degreeC).

  The surfactant used for the emulsion polymerization may be an anionic surfactant alone or in combination with a nonionic surfactant. The amount used is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of all monomers. If it exceeds 10 parts by weight, the removability after high temperature and high humidity tends to decrease. On the other hand, when the amount is less than 0.1 part by weight, the polymerization stability may be lowered.

  In the present invention, it is preferable to use a non-reactive surfactant, that is, a non-reactive surfactant having no radically polymerizable functional group. When the reactive surfactant is used, the anchoring property to the paper base material is deteriorated and the removability may be lowered.

Among the surfactants used in the present invention, as the non-reactive surfactant, dodecylbenzene sulfonate, lauryl sulfate, alkyl diphenyl ether sulfonate, dialkyl sulfosuccinate, polyoxyethylene alkyl phenyl ether sulfate, Anionic surfactants such as polyoxyethylene polycyclic phenyl ether sulfate and polyoxyethylene alkyl ether sulfate;
Polyoxyethylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether and polyoxyethylene octylphenyl ether;
Polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether;
Polyoxypolycyclic phenyl ethers such as polyoxyethylene distyrenated phenyl ether;
Nonionic surfactants such as polyoxyethylene sorbitan fatty acid esters are listed.

In the present invention, the polymerization initiator used for the synthesis of the acrylic resin (A) is preferably a radical polymerization initiator. As the radical polymerization initiator, an azo compound, a peroxide, or the like can be used. Among these, peroxides are preferable, but it is particularly preferable to use a combination of peroxides and reducing agents (hereinafter also referred to as redox initiators). By using a redox initiator, it is estimated that the acrylic resin (A) has few branches and a linear molecular structure, but this linear molecular structure provides both removability and adhesion to a rough surface. I guess it can be achieved at a higher level.
Examples of the peroxide include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate, azobisisobutyronitrile and its hydrochloride, and 2,2-azobis (2-amidinopropane) dihydrochloride. Azo initiators such as 4,4-azobis (4-cyanovaleric acid), hydrogen peroxide, tertiary butyl hydroperoxide and the like.
Examples of the reducing agent include sodium pyrosulfite and L-ascorbic acid.
As combinations of redox initiators, for example, a combination of peroxide and ascorbic acid (a combination of hydrogen peroxide solution and ascorbic acid), a combination of peroxide and iron (II) salt (hydrogen peroxide solution) And a combination of persulfate and sodium bisulfite, and the like. In the present invention, a combination of ammonium persulfate and sodium pyrosulfite is preferable from the viewpoint of removability.

  The amount of the polymerization initiator used is preferably 0.3 to 1 part by weight, more preferably 0.4 to 0.8 part by weight, based on 100 parts by weight of all monomers. That is, when the amount is more than 1 part by weight, the re-peelability after aging at high temperature and high humidity may be insufficient. Moreover, there exists a possibility that superposition | polymerization stability may fall that it is less than 0.3 weight part.

  In the present invention, the reaction temperature during emulsion polymerization is preferably 80 ° C. or lower, more preferably 70 ° C. or lower. If it exceeds 80 ° C., the acrylic resin (A) tends to branch and the removability may be reduced. Moreover, it is preferable to perform reaction temperature at normal temperature or more.

In the present invention, a chain transfer agent may be used for adjusting the molecular weight of the acrylic resin (A).
As the chain transfer agent, for example, a compound having a thiol group or a hydroxyl group is generally known. Examples of the compound having a thiol group include mercaptans such as lauryl mercaptan, 2-mercaptoethyl alcohol, dodecyl mercaptan, mercaptosuccinic acid, and alkyl mercaptopropionates such as n-butyl mercaptopropionate and octyl mercaptopropionate, Examples include mercaptopropionate alkoxyalkyl such as methoxybutyl mercaptopropionate. Moreover, alcohols, such as methyl alcohol, n-propyl alcohol, isopropyl alcohol (IPA), t-butyl alcohol, benzyl alcohol, are mention | raise | lifted. Among these, it is preferable to use alcohols such as isopropyl alcohol from the viewpoint of the odor of the adhesive and the aggregates.

  The amount of the chain transfer agent used is preferably from 0.01 to 0.1 parts by weight, more preferably from 0.03 to 0.07 parts by weight, based on 100 parts by weight of the total monomers. That is, if it exceeds 0.1 parts by weight, the removability after aging at high temperature and high humidity may be reduced. When the amount is less than 0.01 parts by weight, the expected effect may not be obtained.

  Examples of the aqueous medium used in the present invention include water, and a hydrophilic organic solvent can also be used as needed within a range that does not impair the objects and effects of the present invention.

  The obtained acrylic resin (A) is preferably used after being neutralized with a base compound. As the basic compound, ammonia, and as the amines, monoethylamine, dimethylethanolamine, methylpropanolamine and the like are used. These may be used alone or in combination of two or more.

  In this invention, 150-1000 nm or more is preferable and, as for the average particle diameter of acrylic resin (A), 200-800 nm is more preferable. If the average particle size is less than 150 nm, the viscosity of the emulsion becomes too high, and the applicability of the pressure-sensitive adhesive is lowered, and a good pressure-sensitive adhesive tape may not be obtained. On the other hand, when it exceeds 800 nm, the water resistance of the pressure-sensitive adhesive is lowered, and the adhesive strength to the adherend may be lowered. In addition, this average particle diameter was calculated | required using the dynamic light scattering method (Microtrac NPA150 NPA150).

  In this invention, it is preferable that the weight average molecular weight which shows the maximum value of the gel permeation chromatogram of the tetrahydrofuran soluble part of the dry film formed from acrylic resin (A) is 200,000-600,000, 25 More preferably, it is 10,000 to 450,000. If it is less than 250,000, adhesive residue may occur after re-peeling after aging at high temperature and high humidity. On the other hand, when it exceeds 600,000, the anchoring property to the paper substrate and the adhesiveness to each adherend are likely to be insufficient.

The molecular weight measurement method in the present invention is as follows.
That is, the acrylic resin (A) was applied to a polyethylene terephthalate (PET) film so that the dry film thickness was about 20 g / m ² and dried at 25 ° C. for 24 hours. Soak at 25 ° C. for 1 day. Then, after filtering THF with a filter, GPC measurement is performed.
The measurement conditions for GPC are as follows.
Apparatus: Shodex GPC System-21 [manufactured by Showa Denko KK]
Column: A total of three Shodex KF-602.5 and two Shodex KF-606M (manufactured by Showa Denko KK) are connected and used.
Solvent: Tetrahydrofuran Flow rate: 0.5 ml / min
Temperature: 40 ° C
Sample concentration: 0.1 wt%
Sample injection volume: 50 μl

  In this invention, it is preferable that the ethyl acetate extraction residue of the dry film formed from the water-system re-peelable pressure-sensitive adhesive is 45 to 75% by weight. If it is less than 45% by weight, the removability after aging at high temperature and high humidity may be inferior. On the other hand, when it exceeds 75% by weight, the anchoring property to the paper substrate and the adhesiveness to each adherend may be insufficient.

The method for measuring the ethyl acetate extraction residue in the present invention is as follows.
That is, the aqueous re-peelable pressure-sensitive adhesive is applied to a polyethylene terephthalate (PET) film so that the dry film thickness is about 200 μm, and then dried at 25 ° C. for 24 hours. The pressure-sensitive adhesive sheet is cut into a size of 5 cm × 5 cm, and the weight of the pressure-sensitive adhesive layer laminated on the test piece is measured (the weight is defined as G1). The specimen is left in 50 ml of ethyl acetate at 23 ° C. for 1 day. Subsequently, the residue obtained by filtering the test piece and the toluene solution with a filter cloth was dried at 105 ° C. for 1 hour, the weight after drying of the pressure-sensitive adhesive layer laminated on the test piece, and the weight after drying of the residue obtained by filtering the solution. Is measured (the combined weight is G2). Then, it is calculated by (G2 / G1) × 100.

  It is important that the aqueous re-peeling adhesive of the present invention does not contain a tackifying resin. It is because it becomes difficult to make adhesive force and removability compatible by including tackifying resin.

Next, the curing agent (B) used in the present invention is not particularly limited as long as it crosslinks with a carboxyl group. For example, an oxazoline compound, a carbodiimide compound, an epoxy compound, an aziridine compound, an isocyanate compound , Melamine compounds, metal compounds such as metal complexes, amine compounds, and the like. Among them, epoxy compounds are particularly preferable because they are particularly excellent in removability after aging at high temperature and high humidity.
The addition amount of the curing agent is preferably such that the ethyl acetate extraction residue of the dry film formed from the aqueous re-peelable pressure-sensitive adhesive is 45 to 75% by weight.

  Examples of the oxazoline compound include addition-polymerizable 2-oxazoline (for example, 2-isopropenyl-2-oxazoline) having a substituent having an unsaturated carbon-carbon bond at the 2-position carbon position and other unsaturated monomer. And a copolymer with the body.

  Examples of the carbodiimide compound include those containing at least two carbodiimide groups.

  Examples of the epoxy compound include bisphenol A / epichlorohydrin type epoxy resin, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl. Ether, resorcinol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol di Glycidyl ether, propylene glycol diglyme Dil ether, polypropylene glycol diglycidyl ether, diglycidyl aniline, diglycidyl amine, N, N, N ′, N′-tetraglycidyl m-xylenediamine, 1,3-bis (N, N′-diglycidylaminomethyl) And cyclohexane.

The aqueous re-peelable pressure-sensitive adhesive of the present invention preferably contains a polyol (C). This is preferable because the anchoring property to the base material is improved and the removability is improved.
As the polyol (C), at least one selected from polyhydric alcohols can be used. In particular, among polyhydric alcohols, polyhydric alcohols that are liquid at normal temperature, polyoxyalkylenes, glycol ethers of polyoxyalkylenes, polyoxyalkylene adducts of alkylamines, and the like are preferably used. Specifically, ethylene glycol, polyalkylene glycol having a number average molecular weight of 2000 or less, glycerin, polyglycerin (for example, diglycerin, hexaglycerin, hexaglycerin, decaglycerin), glycerin ethylene oxide adduct, glycerin propylene oxide adduct, tri Examples include methylolpropane propylene oxide adduct, sorbitol propylene oxide adduct, ethylenediamine propylene oxide adduct, ethylene oxide / propylene oxide / ethylene oxide block, alkylamine ethylene oxide adduct, etc., and at least one selected from these groups More than seeds can be used. More preferred are ethylene glycol, polyethylene glycol having a number average molecular weight of 2000 or less, glycerin, and polyglycerin.

  The amount of the polyol (C) used is preferably 0.2 to 10 parts by weight with respect to 100 parts by weight of the acrylic resin (A). When the amount used is less than 0.2 parts by weight, the used effect cannot be obtained, and when it exceeds 10 parts by weight, the removability may be lowered due to a decrease in cohesive force.

  The water-based re-peelable pressure-sensitive adhesive of the present invention includes various additives such as a general aqueous pressure-sensitive adhesive, such as an antifoaming agent, a wetting agent, a coloring pigment, a thickening agent, a plasticizer, an antioxidant, and an ultraviolet ray as necessary. Absorbers, preservatives and the like can be blended.

The adhesive tape of the present invention will be described. The pressure-sensitive adhesive tape of the present invention includes a pressure-sensitive adhesive layer formed from the aqueous re-peelable pressure-sensitive adhesive. In the present invention, the pressure-sensitive adhesive tape is also referred to as a pressure-sensitive adhesive sheet, and a product obtained by separating these is also referred to as a pressure-sensitive adhesive label.
The adhesive tape is a transfer coating method in which a water-based re-peelable adhesive is applied to a release sheet, dried, and then bonded to the base material, and the adhesive is directly applied to the base material first, and then dried and attached to the release sheet. It can be manufactured by a direct coating method or the like.

  The substrate is preferably paper, synthetic paper, plastic film or the like, and may be subjected to so-called anchor treatment. Further, it is preferable to use a release sheet obtained by subjecting paper or a plastic film to a release treatment such as silicone.

  The method for applying the aqueous pressure-sensitive adhesive composition is not particularly limited, and a conventionally known coating apparatus such as a roll coater such as a comma coater, a blade coater, or a gravure coater, a slot die coater, a lip coater, or a curtain coater is used. be able to.

  0.1-200 micrometers is preferable and, as for the thickness of the adhesive layer of an adhesive tape, 1-100 micrometers is more preferable. If it is out of the above numerical range, there is a possibility that both adhesive strength and removability cannot be achieved.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited only to a following example. The following “parts” and “%” are values based on parts by weight and “% by weight”, respectively.

[Example 1]
Put 23.4 parts of ion-exchanged water into a 2 L four-necked flask equipped with a reflux condenser, stirrer, thermometer, nitrogen inlet tube, and raw material inlet, and maintain the internal temperature while stirring while introducing nitrogen. Warmed to 70 ° C. As monomers, 33 parts of 2-ethylhexyl acrylate (hereinafter abbreviated as “2-EHA”), 66 parts of butyl acrylate (hereinafter abbreviated as “BA”), 1 part of acrylic acid (hereinafter abbreviated as “AA”) A mixture of 2.0 parts of PELEX OT-P (an anionic non-reactive surfactant manufactured by Kao Corporation) and 20.8 parts of ion-exchanged water as a surfactant was emulsified with a homomixer, and a monomer emulsion Was made.
In the above reaction vessel, 5% of the obtained monomer emulsion was added, and at the same time, 0.4 part of 5% aqueous solution of ammonium persulfate (hereinafter abbreviated as “APS”) and 2% sodium pyrosulfite (hereinafter referred to as “polysulfite”). Emulsion polymerization was started by adding 0.5 part of an aqueous solution (abbreviated as “SMBS”).
Three minutes after adding 5% APS aqueous solution and 2% SMBS aqueous solution to the reaction vessel, the monomer emulsion, 3.6 parts of 5% APS aqueous solution and 4.5 parts of 2% SMBS aqueous solution were simultaneously added over 5 hours. It was dripped. During this period, the inside of the reaction vessel was kept at a preferable upper limit of 70 ° C.
After completion of the dropwise addition, the mixture was kept at 70 ° C. for 3 hours and aged. Thereafter, cooling was started, and the mixture was cooled to 30 ° C. and neutralized by adding aqueous ammonia to obtain an acrylic resin emulsion having a nonvolatile content concentration of 55.0%, pH 7.0, and a viscosity of 250 mPa · s.
In addition, the glass transition temperature calculated | required from a monomer (henceforth "theoretical Tg") was -57 degreeC. The weight average molecular weight which shows the maximum value of the gel permeation chromatogram of the tetrahydrofuran soluble part of a polymer was 410,000.

Preservative: 0.03 part, wetting agent: 0.5 part, antifoaming agent 1.0 part, and propylene glycol 1.8 parts as polyol with respect to 100 parts of the obtained acrylic resin emulsion. A composition prepared using a thickener with a homomixer so as to have a viscosity of 3000 mPa · s (BL type viscometer, measured at 25 ° C. with # 4 rotor / 60 rpm) was obtained.
Furthermore, 0.5 parts by weight of an epoxy crosslinking agent (manufactured by Nagase ChemteX Corp., trade name “Denacol EX-614B”) is added to 100 parts by weight of the acrylic resin content in the composition. A peelable adhesive was obtained.

[Example 2]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the amounts of 2EHA and BA used were changed to 2EHA 49.5 parts and BA 49.5 parts.

[Example 3]
A water-based re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the amounts of 2EHA and BA used were changed to 2EHA 33.0 parts and BA 66.0 parts.

[Example 4]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that propylene glycol was increased to 5.4 parts.

[Example 5]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that propylene glycol was increased to 9.0 parts.

[Example 6]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that propylene glycol was changed to dipropylene glycol.

[Example 7]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that propylene glycol was changed to ethylene glycol.

[Comparative Example 1]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the amounts of 2EHA and BA were changed to 2EHA 15.0 parts and BA 84.0 parts.

[Comparative Example 2]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the amounts of 2EHA and BA used were changed to 2EHA 84.0 parts and BA 15.0 parts.

[Comparative Example 3]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the polymerization initiator was changed to 6.0 g of 5% APS aqueous solution, added to the reaction vessel at once, and the reaction was carried out while maintaining the reaction temperature at 80 ° C.

[Comparative Example 4]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that 3 parts of isopropyl alcohol was added as a chain transfer agent during synthesis.

[Comparative Example 5]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the surfactant was changed to the reactive surfactant Aqualon KH-10 (Daiichi Kogyo Seiyaku).

  The pressure-sensitive adhesives obtained in Examples and Comparative Examples were applied on a release sheet with an applicator so as to have a dry film thickness of 20 μm, and dried in a drying oven at 100 ° C. for 3 minutes to form a pressure-sensitive adhesive layer. Subsequently, a quality paper was bonded to the pressure-sensitive adhesive layer provided on the release sheet to prepare a pressure-sensitive adhesive tape.

[Evaluation of the physical properties]
<Stress-strain curve>
Test samples were prepared and evaluated by the above method.

<Permanent adhesive strength>
The obtained adhesive tape was cut into 25 mm × 100 mm in an environment of 23 ° C. and 50% RH to prepare a test piece. The test pieces were attached to a SUS board (SUS304) and cardboard (K liner manufactured by Oji Paperboard Co., Ltd.) to obtain test samples. Based on JIS Z0237, the test sample was measured for adhesive strength 24 hours after application at a pulling speed of 300 mm / min by a 180 ° peeling method.

<Adhesive strength after heat and humidity>
The obtained adhesive tape was cut into 25 mm × 100 mm in an environment of 23 ° C. and 50% RH to prepare a test piece. Test specimens were attached to a stainless steel plate (SUS304) and cardboard (K liner), respectively, to obtain test samples. The test sample was allowed to stand in a 23 ° C., 50% RH environment for 1 day, then left in a 40 ° C., 80% RH environment for 7 days, then returned to a 23 ° C., 50% RH environment, and allowed to stand for 2 hours. After that. The test sample was measured for adhesive strength at a pulling speed of 300 mm / min by 180 ° peeling method based on JIS Z0237.

<Curved surface paste>
The obtained adhesive tape was cut into 25 mm × 100 mm in an environment of 23 ° C. and 50% RH to prepare a test piece. The test piece was attached to a paper tube of cardboard having a diameter of 80 mmφ. Then, after standing for 3 days in an environment of 23 ° C. and 50% RH, leaving it for 3 days in an environment of 40 ° C. and 80% RH, returning to an environment of 23 ° C. and 50% RH, and then allowing to stand for 2 hours The piece was peeled off and the state was evaluated.
○: Peeling length is less than 3 mm Δ: Peeling length is 3 to 10 mm
X: Peeling length is larger than 10 mm

<Removability>
After the evaluation of the curved surface sticking property test, the test piece was peeled off by hand, and the peeled state was observed.
○: No adhesive remains on the adherend.
* CL: The adherend is contaminated or clouded. * PF: The substrate is broken.
XCF: There is cohesive failure of the pressure-sensitive adhesive layer.
The above evaluation results are shown in the table.

  In Table 1, the usage amount of the surfactant and the polymerization initiator is the usage amount based on 100 parts by weight of the total monomers. Moreover, the usage-amount of a polyol and a hardening | curing agent is a usage-amount with respect to 100 weight part of acrylic resins.

From the result of Table 1, since the stress-strain curve was outside the predetermined numerical range, the comparative example could not achieve both adhesiveness and removability.
On the other hand, in the examples, the stress-strain curve was in a predetermined numerical range, and therefore, the adhesiveness to the rough surface and the re-peelability after aging at high temperature and high humidity were compatible.

Claims (5)

An aqueous re-peelable pressure-sensitive adhesive containing an acrylic resin (A) and a curing agent (B),
The stress value at the time of 200% strain in the stress-strain curve of the dry film having a cross-sectional area of 4 mm ² formed from the aqueous re-peelable pressure-sensitive adhesive is 0.01 to 0.03 N / mm ² ,
A water-based re-peelable pressure-sensitive adhesive having a strain at a maximum stress of 800 to 1300% and a maximum stress value of 0.04 to 0.08 N / mm ² . A non-reactive surfactant is a monomer mixture in which the acrylic resin (A) contains a total of 90.0 to 99.9% by weight of at least 2-ethylhexyl acrylate (A-1) and butyl acrylate (A-2). In the presence of a polymerization initiator using a peroxide and a reducing agent, and the weight ratio of (A-1) / (A-2) is 55/45 to 25/75. Yes,
The aqueous re-peelable pressure-sensitive adhesive according to claim 1, wherein the curing agent (B) is an epoxy compound and further contains a polyol (C). A water-based re-peelable pressure-sensitive adhesive, wherein the ethyl acetate extraction residue of a dry film formed from the water-based re-peelable pressure-sensitive adhesive according to claim 1 is 45 to 75% by weight. The water-based re-peelable pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the dry film formed from the acrylic resin (A) has a weight average molecular weight of 25 to 450,000 for elution of tetrahydrofuran. An adhesive tape comprising an adhesive layer formed from the aqueous re-peelable adhesive according to claim 1.