JP2012207204A - Water-based removable pressure-sensitive adhesive and removable pressure-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based removable pressure-sensitive adhesive constitutable of a pressure-sensitive adhesive sheet which has good anchoring properties with respect to synthetic paper or synthetic resin films such as plastic films, has high adhesive force to an adherend such as stainless steel, olefin and corrugated board, and causes no floating nor peeling after the tape is once stuck, and is easily removable even after the tape is stuck for a long period of time in a high temperature environment (with lapse of time at high temperature).SOLUTION: The water-based removable pressure-sensitive adhesive comprises an acrylic polymer (A) having a glass transition temperature of -65°C to -45°C, a tackiness-imparting resin (B), a carbodiimide group-containing compound (C) and a polyol (D). The acrylic polymer (A) is the copolymer of monomers including at least a carboxy group-containing monomer (a-1) by 0.8 to 7 wt.% and a monomer (a-2) having a glass transition temperature of 100 to 110°C. The tackiness-imparting resin (B) has a softening point of 120 to 180°C.

Description

  The present invention relates to an aqueous re-peelable pressure-sensitive adhesive and a pressure-sensitive adhesive sheet.

  The pressure-sensitive adhesive sheet is used in various applications. One of the applications is a re-peelable pressure-sensitive adhesive sheet. The re-peelable pressure-sensitive adhesive sheet is required to have a performance that can be easily peeled even after a predetermined time has elapsed after being stuck to an adherend (hereinafter referred to as re-peelability).

  By the way, when manufacturing a label based on paper, in order to reduce the cost as much as possible, it is common to use a water-based pressure-sensitive adhesive that is less expensive than a solvent-type pressure-sensitive adhesive. The re-peelable pressure-sensitive adhesive sheet using paper as a base material ensures adhesion to the paper base material by impregnating the base material with an aqueous pressure-sensitive adhesive during coating.

  On the other hand, from the viewpoint of improving merchantability such as good appearance after label printing, use of a synthetic resin film substrate such as synthetic paper or plastic film made of a material such as olefin as the substrate is performed. . However, since the water-based pressure-sensitive adhesive does not impregnate a synthetic resin film substrate such as synthetic paper, the adhesive (hereinafter also referred to as anchoring property) of the pressure-sensitive adhesive to the synthetic resin film substrate is insufficient. For this reason, for example, after a synthetic paper label using an aqueous pressure-sensitive adhesive is attached to the adherend, the adhesive remains on the adherend when it is peeled off. In general, the re-peelable pressure-sensitive adhesive sheet is cut into sheets and used as a label. However, stainless steel with high polarity, olefinic adherend with low polarity and difficult adhesion, and a lot of irregularities on the surface Regardless of the type of adherend, such as so-called rough corrugated cardboard adherends, the label sticks without sticking during sticking, but the adhesive strength of the label changes little over time, so when peeling the label A function of easily peeling off without any adhesive residue was required.

  Therefore, a strong adhesion type re-peelable pressure-sensitive adhesive that has good adhesion to a synthetic resin film substrate and can be easily peeled off from an adherend has been disclosed (see Patent Document 1).

JP 2008-266415 A

  However, since the pressure-sensitive adhesive sheet of Patent Document 1 uses a hydroxyl group-containing monomer for polymer synthesis and further uses an epoxy cross-linking agent, the anchoring property is low with respect to synthetic paper and plastic films. Further, since the adhesive force to a polar adherend such as stainless steel is too high, there is a problem that the removability varies depending on the adherend, such as the cardboard being broken when the label is peeled off from the cardboard.

  The present invention is a pressure-sensitive adhesive sheet that has good anchoring properties on synthetic resin films such as synthetic paper and plastic film, and has high adhesive strength to adherends such as slurries, olefins, and cardboard, and floats and peels off after application. The purpose of the present invention is to provide an aqueous re-peelable pressure-sensitive adhesive that can constitute a pressure-sensitive adhesive sheet that can be easily re-peeled after aging, particularly after being applied for a long time in a high-temperature atmosphere (also called after high-temperature aging). . The term “time elapsed” means that time has elapsed after the pressure-sensitive adhesive sheet is attached to the adherend.

  The present invention essentially comprises an acrylic polymer (A) synthesized with a low glass transition temperature, a tackifier resin (B), a carbodiimide group-containing compound (C) as a crosslinking agent, and a polyol (D). It is an aqueous re-peeling type adhesive. For the synthesis of the acrylic polymer (A), the carboxyl group-containing monomer (a-1) is 0.8 to 7% by weight and the monomer (a-2) having a glass transition temperature of 100 to 110 ° C. is 5 to 15% by weight. Is used. The softening point of the tackifying resin is 120 ° C to 180 ° C.

  According to the present invention having the above-described structure, good anchoring properties for a synthetic resin film can be obtained by using an acrylic polymer having a low glass transition temperature and a cross-linking reaction between a carboxyl group of the acrylic polymer and a carbodiimide group-containing compound. In addition, removability can be obtained regardless of the adherend. In addition, the use of a monomer having a glass transition temperature of 100 ° C. of the homopolymer is excellent in removability even after high temperature aging, and a high adhesive force is obtained by using a tackifying resin having a softening point of 120 ° C. to 180 ° C. Obtainable.

  Furthermore, the pressure-sensitive adhesive layer is plasticized due to the presence of the polyol, and adhesion to the base material (throwing property) is improved. Good re-peelability can be obtained even after a lapse of time when re-peeling becomes difficult due to excessive progress of adhesion to the body, particularly after a high temperature.

  With the aqueous re-peelable pressure-sensitive adhesive of the present invention, the anchoring property to the synthetic resin film is good, and it has a high adhesive force to adherends having different polarities or surface states such as slureless, olefin and corrugated cardboard. A pressure-sensitive adhesive sheet that was not lifted off or peeled off and could be easily re-peeled over time could be constructed.

  The acrylic polymer (A) includes a carboxyl group-containing monomer (a-1) and a monomer (a-2) (hereinafter referred to as monomer (a-) having a homopolymer glass transition temperature (hereinafter also referred to as Tg) of 100 to 110 ° C. 2)) and a copolymer obtained by copolymerizing other monomers. The polymerization method is preferably emulsion polymerization. Emulsion polymerization can balance agglomeration force, adhesive strength, and tack. Moreover, it is important that the acrylic polymer (A) has a glass transition temperature of −65 ° C. to −45 ° C. By setting this temperature, the anchoring property for the synthetic resin film can be improved. Here, the glass transition temperature of the monomer (a-2) is the glass transition temperature of the homopolymer.

The carboxyl group-containing monomer (a-1) serves as a cross-linking point with the carbodiimide group-containing compound (C) and is also important from the viewpoint of polymerization stability during emulsion polymerization. Specifically, for example, acrylic acid (Tg 106 ° C), methacrylic acid (Tg 186 ° C), itaconic acid (Tg
100 ° C.), maleic acid (Tg 130 ° C.) and the like. Of these, acrylic acid is preferred. In addition, Tg described in the monomer is a glass transition temperature of the homopolymer.

  The amount of the carboxyl group-containing monomer (a-1) used is preferably 0.8 to 7% by weight, more preferably 2.5 to 5.5% by weight, based on all monomers. Here, when the carboxyl group-containing monomer (a-1) is less than 0.8% by weight, there is a risk of adhesive residue on the adherend during re-peeling. On the other hand, if it exceeds 7% by weight, wetting to stainless steel with high polarity proceeds, and re-peelability may deteriorate after high temperature aging.

The monomer (a-2) having a glass transition temperature of 100 to 110 ° C. of the homopolymer specifically includes aromatic monomers such as styrene (Tg 100 ° C.) and phenyl methacrylate (Tg 105 ° C.);
Ethyl methacrylate (Tg 105 ° C.), t-butyl methacrylate (Tg 107 ° C.),
Methacrylic esters such as
And acrylonitrile (Tg 105 ° C.). Among these, methyl methacrylate is preferable from the viewpoint of copolymerization.
In the present invention, a monomer containing a carboxyl group is not included in the monomer (a-2) even if its glass transition temperature is 100 to 110 ° C.

  The amount of the monomer (a-2) used is preferably 5 to 15% by weight, more preferably 7 to 11% by weight, based on all monomers. By using a specific amount of the monomer (a-2) having a specific glass transition temperature, the anchoring property of the pressure-sensitive adhesive with respect to the synthetic resin film substrate can be further improved. Here, when the amount used is less than 5% by weight, re-peelability after high temperature aging may be deteriorated. On the other hand, if it exceeds 15% by weight, wetting to stainless steel with high polarity proceeds, and the removability may be lowered.

The other monomer (a-3) is a monomer other than the carboxyl group-containing monomer (a-1) and the monomer (a-2). Specifically, acrylic acid such as methyl acrylate (Tg 8 ° C.), ethyl acrylate (Tg −22 ° C.), butyl acrylate (Tg −52 ° C.), acrylic acid-2-ethylhexyl (Tg −70 ° C.), etc. Esters;
Methacrylic acid esters such as ethyl methacrylate (Tg 65 ° C.), butyl methacrylate (Tg 20 ° C.), 2-ethylhexyl methacrylate (Tg −10 ° C.), cyclohexyl methacrylate (Tg 66 ° C.);
aromatic monomers such as α-methylstyrene (Tg 168 ° C.) and benzyl methacrylate (Tg 54 ° C.);
Vinyl esters such as vinyl acetate (Tg 29 ° C.);
Heterocyclic vinyl compounds such as vinylpyrrolidone (Tg 180 ° C.);
Glycidyl group-containing monomers such as glycidyl methacrylate (Tg 41 ° C.);
Hydroxyl group-containing monomers such as 2-hydroxyethyl methacrylate (Tg 55 ° C.);
Amino group-containing monomers such as dimethylaminoethyl methacrylate (Tg 18 ° C.);
Carboxylic acid amide group-containing monomers such as acrylamide (Tg 153 ° C.);
And polyfunctional vinyl monomers such as diallyl phthalate (Tg 90 ° C.). Among these, 2-ethylhexyl acrylate is preferable because Tg can be lowered.

  Although the usage-amount of another monomer (a-3) should just be other than the total amount of the carboxyl group-containing monomer (a-1) and monomer (a-2) in 100 weight% of all the monomers, it is 78-94. 2% by weight is preferred.

  The glass transition temperature of the acrylic polymer (A) is preferably −65 to −45 ° C., more preferably −60 to −50 ° C. By being within the range of −65 to −45 ° C., anchoring properties for the synthetic resin film can be obtained. Here, when the glass transition temperature is higher than −45 ° C., the anchoring property and the adhesive force to the synthetic resin film may be insufficient. On the other hand, when it is lower than −65 ° C., the removability after high temperature aging may be insufficient.

  In the present invention, the glass transition temperature of the acrylic polymer (A) is theoretically derived by the following formula [1].

Formula [1]
1 / Tg = [(W1 / Tg1) + (W2 / Tg2) +... (Wn / Tgn)] / 100
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)

  In the present invention, the glass transition temperature of the homopolymer was according to “Kyozo Kitaoka,“ Introduction to Synthetic Resins for Paints ”, published by Kobunshi Publishing, May 25, 1974”.

  In the emulsion polymerization of the monomer, a surfactant having an ethylenically unsaturated group may be used, but in the present invention, the surfactant is not included in the calculation of the glass transition temperature. To do.

  In the emulsion polymerization, it is preferable to use a surfactant. The surfactant is preferably an anionic surfactant from the viewpoint of the stability of the emulsion, but a nonionic surfactant can also be used in combination depending on the required physical properties.

  The surfactant includes a so-called reactive surfactant having an ethylenically unsaturated group and a non-reactive surfactant not having the ethylenically unsaturated group. In the present invention, a non-reactive surfactant is preferable. When a reactive surfactant is used, there is a risk that the adhesive property of the pressure-sensitive adhesive to the synthetic resin film substrate and the re-peelability may be reduced.

  0.1-10 weight part is preferable with respect to 100 weight part of all the monomers, and, as for the usage-amount of surfactant, 0.5-5 weight part is more preferable. When the amount used is less than 0.1 part by weight, the polymerization stability may be lowered and the polymer synthesis may not be possible. On the other hand, if it exceeds 10 parts by weight, re-peelability after high temperature aging may be lowered. Even when a reactive surfactant is used in combination, it is preferably kept at 1 part by weight or less.

  Among the surfactants, non-reactive surfactants include dodecylbenzene sulfonate, lauryl sulfate, alkyl diphenyl ether sulfonate, dialkyl sulfosuccinate, polyoxyethylene alkylphenyl ether sulfate, polyoxyethylene polycyclic Anionic surfactants such as phenyl ether sulfate and polyoxyethylene alkyl ether sulfate; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonylphenyl ether and polyoxyethylene octylphenyl ether; polyoxyethylene lauryl ether, poly Polyoxyethylene alkyl ethers such as oxyethylene stearyl ether and polyoxyethylene oleyl ether; polyoxyethylene distyrenated phenyl ether and other polyoxyethylene alkyl ethers Carboxymethyl polycyclic phenyl ethers, polyoxyethylene sorbitan fatty acid esters such as nonionic surface active agents, and the like.

  In the present invention, the anionic non-reactive surfactant is preferably a polyoxyethylene lauryl ether type in terms of anchoring properties.

  In the present invention, the anionic reactive surfactant is not particularly limited, but an allyloxymethyl alkyl ether type is preferable.

  The reactive surfactant is preferably a compound in which a radical polymerizable functional group such as an ethylenically unsaturated group is added to the non-reactive surfactant as described above.

  In the present invention, the polymerization initiator used for emulsion polymerization is preferably a radical polymerization initiator. The radical polymerization initiator is preferably a peroxide, but more preferably a combination of a peroxide and a reducing agent (hereinafter also referred to as a redox initiator). By using a redox initiator, it is assumed that the acrylic polymer (A) has few branches and has a linear molecular structure, but this linear molecular structure allows re-peelability and adhesion to a rough surface. It is speculated that the balance 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. If the amount used is less than 0.3 parts by weight, the polymerization stability may be lowered. On the other hand, when it is more than 1 part by weight, the removability after high temperature aging may be insufficient.

  In the present invention, the polymerization temperature is preferably 80 ° C. or lower, and more preferably 70 ° C. or lower. If it exceeds 80 ° C., the acrylic polymer (A) tends to branch and the removability may be reduced. The polymerization temperature is preferably carried out at room temperature or higher.

  In the present invention, a chain transfer agent may be used to adjust the molecular weight of the acrylic polymer (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, it is preferable to use alcohols, such as methyl alcohol, n-propyl alcohol, isopropyl alcohol (IPA), t-butyl alcohol, and benzyl alcohol.

  The amount of 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 the amount used is less than 0.01 parts by weight, the desired effect may not be obtained. On the other hand, if it exceeds 0.1 parts by weight, the removability after high temperature aging may be lowered.

  In the present invention, the emulsion polymerization is preferably carried out using water as a solvent, but a hydrophilic organic solvent can also be used as long as the object and effects of the present invention are not impaired.

  In the present invention, the acrylic polymer (A) is preferably used after being neutralized with a basic compound. Specific examples include ammonia and amines such as monoethylamine, dimethylethanolamine, and methylpropanolamine. These may be used alone or in combination of two or more.

  In the present invention, the average particle size of the acrylic polymer (A) is preferably 150 to 1000 nm, and more preferably 200 to 800 nm. When the average particle diameter is less than 150 nm, the viscosity is too high, and the applicability of the pressure-sensitive adhesive may be reduced. On the other hand, when it exceeds 1000 nm, the water resistance of the pressure-sensitive adhesive is decreased, and the adhesive strength to the adherend may be decreased. In addition, in this invention, an average particle diameter is the numerical value calculated | required using the dynamic light scattering method (Microtrac NPA150 by Microtrac).

  The tackifier resin (B) is used to increase the adhesive strength of the adhesive tape. The tackifier resin (B) can be roughly classified into a natural resin system and a synthetic resin system. The natural resin system is preferably a rosin resin (including rosin, rosin ester, rosin phenol, and colorless rosin derivative) and a terpene resin (including terpene, aromatic modified terpene, terpene phenol and the like). As the synthetic resin system, petroleum resin system (C5 system, C9 system, C5 / C9 system, aliphatic system, etc.) and others (including phenol resin, xylene resin, ketone resin, etc.) are preferable. Of these, rosin resin, terpene resin and petroleum resin are preferable, and rosin resin is more preferable. When the rosin resin is used, tack, removability, and adhesive stability over time can be further improved. The tackifying resin (B) is preferably a water dispersion type.

  5-15 weight part is preferable with respect to 100 weight part of acrylic polymers (A), and, as for the usage-amount of tackifying resin (B), 7-10 weight part is more preferable. Normally, when a tackifier resin is blended with the pressure-sensitive adhesive, the adhesive strength becomes excessive and re-peelability cannot be obtained, but in the present invention, good re-peelability is obtained due to the combined effect of the acrylic polymer (A) and the carbodiimide group-containing compound. Is obtained. Here, when the usage-amount of tackifying resin is less than 5 weight part, there exists a possibility that a desired effect may not be acquired. On the other hand, when the amount exceeds 15 parts by weight, the adhesive strength is significantly increased after high temperature aging, which may adversely affect the removability.

  The tackifying resin (B) preferably has a softening point of 120 to 180 ° C. When the softening point is less than 120 ° C., the desired adhesive strength tends to be difficult to obtain. On the other hand, tackifying resins exceeding 180 ° C. are not preferred because they are difficult to obtain in the market and the anchoring property tends to deteriorate.

  The carbodiimide group-containing compound (C) is a crosslinking agent and is important for the removability of the adhesive tape. Here, the carbodiimide group-containing compound (C) preferably contains two or more carbodiimide groups. Commercially available products include, for example, “Carbodilite V-02”, “Carbodilite V-02-L2”, “Carbodilite V-04”, “Carbodilite V-06” manufactured by Nisshinbo Co., Ltd., and “Carbodilite E-01”, Examples include “Carbodilite E-02” and “Carbodilite E-04” emulsion types.

  The amount of the carbodiimide group-containing compound (C) used is preferably 0.5 to 3.5 parts by weight with respect to 100 parts by weight of the acrylic polymer (A). Moreover, even if it is outside the said range, what is necessary is just to use so that the gel fraction by ethyl acetate extraction of an aqueous re-peeling type adhesive may be 45 to 75 weight%.

  In the present invention, other crosslinking agents may be used in combination as the crosslinking agent. For example, an oxazoline compound, an epoxy compound, an aziridine compound, an isocyanate compound, a melamine compound, a metal compound such as a metal complex, an amine compound, and the like can be given. These crosslinking agents are preferably 1 part by weight or less from the viewpoint of physical property balance.

  The aqueous re-peelable pressure-sensitive adhesive of the present invention contains a polyol (D). Thereby, the anchoring property to a synthetic resin film base material improves more, and re-peelability can also be improved more. The polyol (D) is preferably a polyhydric alcohol. In particular, among polyhydric alcohols, specifically, polyhydric alcohols that are liquid at room temperature, such as glycols, polyoxyalkylenes, polyoxyalkylene glycol ethers, and alkylamine polyoxyalkylenes It is preferable to use an adduct or the like. For example, ethylene glycol, propylene glycol, dipropylene 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 addition Products, trimethylolpropane propylene oxide adduct, sorbitol propylene oxide adduct, ethylenediamine propylene oxide adduct, ethylene oxide / propylene oxide / ethylene oxide block, alkylamine ethylene oxide adduct and the like. Among these, diols such as ethylene glycol, propylene glycol, dipropylene glycol, and polyethylene glycol having a number average molecular weight of 2000 or less are preferable.

  The amount of the polyol (D) used is preferably 0.2 to 10 parts by weight with respect to 100 parts by weight of the acrylic polymer (A). If the amount used is less than 0.2 parts by weight, the desired effect may not be obtained. On the other hand, if it exceeds 10 parts by weight, the cohesive force may be reduced and the removability may be reduced.

  The aqueous re-peelable pressure-sensitive adhesive of the present invention includes various additives used in general water-based pressure-sensitive adhesives such as an antifoaming agent, a wetting agent, a color pigment, a thickener, a plasticizer, an oxidation agent, if necessary. An inhibitor, an ultraviolet absorber, a preservative, etc. can be blended.

  In the present invention, the gel fraction after crosslinking of the aqueous re-peelable pressure-sensitive adhesive is preferably 45 to 75% by weight, and more preferably 55 to 70% by weight. When the gel fraction is less than 45% by weight, the removability after high temperature aging may be deteriorated. On the other hand, if it exceeds 75% by weight, it may be difficult to balance the anchoring property to the synthetic resin film and the adhesiveness to each adherend.

In the present invention, the method for measuring the gel fraction is as follows. That is, the aqueous re-peelable pressure-sensitive adhesive is coated on a polyethylene terephthalate (PET) film so that the dry film thickness is about 200 μm, and then dried at 23 ° C. for 7 days. Next, the weight of the 200 mesh wire mesh is measured (the weight is M). The pressure-sensitive adhesive sheet is cut into a size of 5 cm × 5 cm, and the weight of the test piece bonded to the 200 mesh wire net is measured (the weight is A).
The specimen is left in 50 ml of ethyl acetate at 50 ° C. for 1 day. Then, after taking out and drying at 100 degreeC for 20 minutes, a weight is measured (the weight is set to T).
Subsequently, a polyethylene terephthalate (PET) film is taken out from the test piece, the pressure-sensitive adhesive layer is removed using ethyl acetate, and the weight of the PET film is measured (the weight is defined as K).
Then, (TMK) × 100 / (AMK) [unit: wt%] is calculated.

  The re-peelable pressure-sensitive adhesive sheet of the present invention will be described. The re-peelable pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer formed from an aqueous re-peelable pressure-sensitive adhesive. In the present invention, the pressure-sensitive adhesive sheet is also referred to as a pressure-sensitive adhesive film or a pressure-sensitive adhesive tape, and a product obtained by separating these is also referred to as a pressure-sensitive adhesive label.

  The re-peelable pressure-sensitive adhesive sheet is a transfer coating method in which an aqueous re-peelable pressure-sensitive adhesive is applied to the release sheet and dried, and then bonded to the base material. First, the adhesive is directly applied to the base material and then peeled off after drying. It can be manufactured by a direct coating method or the like that is bonded to a sheet.

  In the present invention, a known synthetic resin film, high-quality paper, coated paper, impregnated paper or the like, or synthetic paper having a cavity inside, a nonwoven fabric, or the like can be used as the substrate. Among these, a synthetic resin film is preferable. The synthetic resin film may be unstretched, or may be stretched in a uniaxial direction or a biaxial direction such as longitudinal or lateral.

  The synthetic resin film is not particularly limited. Polyolefin resin such as polyethylene resin and polypropylene resin, polyester resin such as polybutylene terephthalate resin and polyethylene terephthalate resin, acetate resin, acrylonitrile / butadiene / styrene (ABS) resin, polystyrene resin And synthetic resin films such as vinyl chloride resin, polyimide resin and polyamide resin, and those obtained by depositing metal such as aluminum on these films. Among these, polyolefin resins such as polypropylene resin and polyester resins such as polyethylene terephthalate resin are preferable.

  Although the thickness of a base material does not have a restriction | limiting in particular, Usually, it is the range of 10-200 micrometers, Preferably it is 25-150 micrometers from the surface of the ease of handling. The substrate may be colored or colorless and transparent. Moreover, you may give printing, printing, etc. to the surface or back surface of a base material.

  As a coating method, for example, a roll coater such as a comma coater, a blade coater or a gravure coater, a coating apparatus such as a slot die coater, a lip coater or a curtain coater can be used. As for the thickness of an adhesive layer, 0.1-200 micrometers is preferable.

  The re-peelable pressure-sensitive adhesive sheet of the present invention can be widely used for industrial and household purposes such as delivery label labels and slip labels.

  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]
46 parts of ion exchange water was placed in a 2 L four-necked flask equipped with a reflux condenser, a stirrer, a thermometer, a nitrogen inlet tube, and a raw material inlet, and the internal temperature was maintained at 70 ° C. while stirring while introducing nitrogen. Warmed to.

Separately, as monomers, 89 parts of 2-ethylhexyl acrylate (hereinafter abbreviated as “2EHA”), 7 parts of methyl methacrylate (hereinafter abbreviated as “MMA”), 4 parts of acrylic acid (hereinafter abbreviated as “AA”), interface A monomer emulsion was prepared by emulsifying a mixture of Haitenol LA-10 (anionic non-reactive surfactant manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and 27 parts of ion-exchanged water as an activator with a homomixer. Produced.
5% of the obtained monomer emulsion was added to the flask, and at the same time, an aqueous solution of ammonium persulfate (hereinafter abbreviated as “APS”) having a concentration of 5% as a polymerization initiator. Emulsion polymerization was initiated by adding 8 parts and 1 part of a 2% strength sodium pyrosulfite (hereinafter abbreviated as “SMBS”) aqueous solution.
Three minutes after adding the 5% APS aqueous solution and the 2% SMBS aqueous solution to the flask, the monomer emulsion, 7.2 parts of the 5% APS aqueous solution and 9 parts of the 2% SMBS aqueous solution were added dropwise simultaneously over 5 hours. . During this time, the inside of the flask was kept at 70 ° C.
After completion of dropping, the reaction was continued at 70 ° C. for 3 hours. Thereafter, cooling was started, and the mixture was cooled to 30 ° C. and neutralized by adding aqueous ammonia to obtain an acrylic polymer emulsion having a nonvolatile content of 55.0%, pH 7.0, and a viscosity of 250 mPa · s.
The glass transition temperature calculated from the monomer composition (hereinafter referred to as “theoretical Tg” or “calculated Tg”) was −59.1 ° C.

  Preservative: 0.3 part, wetting agent: 0.7 part, antifoaming agent: 1.0 part, and a pro as polyol for 100 parts of the acrylic polymer emulsion obtained in terms of non-volatile content. Pyrene glycol 2 parts, tackifier resin: Superester E-788NT [Arakawa Chemical's water-dispersed rosin tackifier (softening point 160 ° C., nonvolatile content 50%)] 9 parts by nonvolatile conversion Then, a composition prepared 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.

  Further, a carbodiimide-based crosslinking agent (manufactured by Nisshinbo Chemical Co., Ltd., trade name “Carbodilite V-04” non-volatile content 40%) is 1 in terms of non-volatile content with respect to 100 parts by weight of the acrylic polymer content in the composition. .5 parts by weight was added to obtain an aqueous re-peelable pressure-sensitive adhesive.

[Example 2]
Except having changed the usage-amount of MMA to 14 parts and the usage-amount of 2EHA to 82 parts, it carried out similarly to Example 1 and obtained the water-based releasable adhesive.

[Example 3]
Except having changed MMA into styrene (St), it carried out similarly to Example 1 and obtained the water-based re-peeling adhesive.

[Example 4]
Except that MMA was changed to tertiary butyl methacrylate (t-BMA), the same procedure as in Example 1 was performed to obtain an aqueous re-peelable pressure-sensitive adhesive.

[Example 5]
Except having changed MMA into acrylonitrile (AN), it carried out similarly to Example 1 and obtained the aqueous re-peeling type adhesive.

[Example 6]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that AA was increased to 5.5 parts and 2EHA was reduced to 87.5 parts.

[Example 7]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that AA was reduced to 2.5 parts and MMA was increased to 8.5 parts.

[Example 8]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that 0.5 part of the reactive surfactant Aqualon KH-10 (Daiichi Kogyo Seiyaku) was used in combination as the surfactant.

[Example 9]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that 1 part of a nonionic non-reactive surfactant Neugen SD-110 (Daiichi Kogyo Seiyaku) was used in combination as a surfactant.

[Example 10]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that only a 5% ammonium persulfate aqueous solution was used as a polymerization initiator and the temperature in the reaction vessel was changed to 85 ° C.

[Example 11]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that Superester E-788NT was reduced to 6 parts in terms of nonvolatile content.

[Example 12]
The same procedure as in Example 1 was performed except that Superester E-788NT was changed to “Hari Star SK-822E (softening point 170 ° C., nonvolatile content 50%)” [Harima Kasei water-dispersed rosin tackifier]. An aqueous re-peelable pressure-sensitive adhesive was obtained.

[Example 13]
Except that superester E-788NT was changed to “superester E-730-55 (softening point: 125 ° C., non-volatile content: 55%)”, an aqueous re-peelable adhesive was obtained in the same manner as in Example 1. .

[Example 14]
The same procedure as in Example 1 was carried out except that the amount of propylene glycol was increased to 10 parts to obtain an aqueous re-peelable pressure-sensitive adhesive.

[Example 15]
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 16]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the amount of Carbodilite V-04 was reduced to 0.5 part in terms of nonvolatile content.

[Example 17]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the amount of Carbodilite V-04 was increased to 3.4 parts in terms of nonvolatile content.

[Example 18]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that Carbodilite V-04 (water-soluble type) was changed to Carbodilite E-04 (emulsion type, nonvolatile content 40%).

[Comparative Example 1]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the amount of MMA was reduced to 3 parts and the amount of 2EHA was increased to 93 parts.

[Comparative Example 2]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that MMA was increased to 30 parts and 2EHA was reduced to 66 parts.

[Comparative Example 3]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the amount of MMA was reduced to 4 parts and the amount of 2EHA was increased to 92 parts.

[Comparative Example 4]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the amount of MMA was increased to 18 parts and the amount of 2EHA was reduced to 78 parts.

[Comparative Example 5]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that AA was reduced to 0.5 parts and MMA was increased to 10.5 parts.

[Comparative Example 6]
The amount of 2EHA was increased to 96 parts, and an aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that MMA was not used.

[Comparative Example 7]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that Superester E-788NT was not used.

[Comparative Example 8]
The same procedure as in Example 1 was performed except that Superester E-788NT was changed to “Hari Star SK-70E (softening point 75 ° C., non-volatile content 49%)” [water dispersion type rosin tackifier manufactured by Harima Chemicals]. An aqueous re-peelable pressure-sensitive adhesive was obtained.

[Comparative Example 9]
An aqueous re-peelable pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that propylene glycol was not used.

[Comparative Example 10]
A pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that Carbodilite V-04 (water-soluble type) was not used.

[Comparative Example 11]
Carbodilite V-04 (water-soluble type) was prepared in the same manner as in Example 1 except that 0.5 part of an epoxy crosslinking agent (manufactured by Nagase ChemteX Corporation, trade name “Denacol EX-614B”) was used. A re-peelable pressure-sensitive adhesive was obtained.

  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.

Next, a 80 μm-thick synthetic resin film (manufactured by YUPO (registered trademark) YUPO Corporation) was bonded to the pressure-sensitive adhesive layer provided on the release sheet to prepare a pressure-sensitive adhesive sheet.

[Evaluation of the physical properties]
<Adhesive strength>
(Initial adhesive strength)
The obtained pressure-sensitive adhesive sheet was cut into 25 mm × 100 mm under a 23 ° C., 50% RH environment to prepare a test piece. Test piece is SUS board (SUS304BA), cardboard (K liner)
, PE (polyethylene) was affixed to each test sample. The test sample was allowed to stand for 30 minutes. The test sample was measured for adhesive strength at a pulling speed of 300 mm / min by 180 ° peeling method based on JIS Z0237.

(Adhesive strength after heating)
The obtained pressure-sensitive adhesive sheet was cut into 25 mm × 100 mm under a 23 ° C., 50% RH environment to prepare a test piece. Test piece is SUS board (SUS304BA), cardboard (K liner)
, PE (polyethylene) was affixed to each test sample. The test sample was allowed to stand for 7 days in a 40 ° C. environment, then returned to a 23 ° C., 50% RH environment, and allowed to stand for 2 hours. The test sample was measured for adhesive strength at a pulling speed of 300 mm / min by 180 ° peeling method based on JIS Z0237.

<Removability>
(Mechanical peeling after heating)
The obtained pressure-sensitive adhesive sheet was cut into 25 mm × 100 mm under a 23 ° C., 50% RH environment to prepare a test piece. Test specimens were attached to SUS plates (SUS304BA), cardboard (K liner), and PE (polyethylene), respectively, to obtain test samples. The test sample was allowed to stand for 7 days in a 40 ° C. environment, then returned to a 23 ° C., 50% RH environment, and allowed to stand for 2 hours. Based on JIS Z0237, the test sample was evaluated for a peeled state at a pulling speed of 300 mm / min by a 180 ° peeling method. The evaluation criteria are as follows.
A: No pressure-sensitive adhesive remains on the adherend and there is no cloudiness.
○: Substrate is slightly clouded × AT: Adhesive layer is transferred to the entire surface of the adherend × CL: Contamination or cloudiness remains on the adherend × CF: Adhesive layer is agglomerated and broken and adhesive residue remains appear

(Sensory evaluation after heating)
The obtained pressure-sensitive adhesive sheet was cut into 50 mm × 50 mm in an environment of 23 ° C. and 50% RH to prepare a test piece. The test piece is SUS board (SUS304BA), cardboard (K liner),
Each test sample was affixed to PE (polyethylene). The test sample was allowed to stand for 7 days in a 40 ° C. environment, then returned to a 23 ° C., 50% RH environment, and allowed to stand for 2 hours. The test sample was peeled by hand in accordance with the actual use situation, and the peeled state was observed. Evaluation criteria are the same as for mechanical peeling after heating.

(Throwing property evaluation)
The pressure-sensitive adhesive layer of the obtained pressure-sensitive adhesive sheet was rubbed with a finger to evaluate the degree of peeling from the substrate.
◎: Even if the pressure-sensitive adhesive layer is rubbed strongly, it does not peel at all. ○: If the pressure-sensitive adhesive layer is rubbed strongly, it peels off faintly, but even if it is rubbed lightly, it does not peel off.
Δ: Slightly peeled off the pressure-sensitive adhesive layer X: Tables 1 and 2 show the evaluation results above that even if the pressure-sensitive adhesive layer was lightly rubbed off.

In Tables 1 and 2, the amount of emulsifier and initiator used is indicated as the amount of each active ingredient relative to 100 parts of the monomer.
Moreover, the amount of tackifier resin, polyol, and curing agent was expressed as the amount of each active ingredient relative to 100 parts of acrylic polymer (that is, the nonvolatile content of the acrylic polymer emulsion).

  From the results of Tables 1 and 2, the examples using the aqueous re-peelable pressure-sensitive adhesive of the present invention have a good anchoring property to the synthetic resin film base material and maintain a high adhesive strength to each adherend. However, good re-peeling was achieved even after high temperature aging. On the other hand, the comparative example could not solve any of the above problems.

Claims (6)

An aqueous re-peelable pressure-sensitive adhesive comprising an acrylic polymer (A) having a glass transition temperature of −65 ° C. to −45 ° C., a tackifier resin (B), a carbodiimide group-containing compound (C), and a polyol (D). There,
The acrylic polymer (A) is at least 0.8 to 7 wt% of the carboxyl group-containing monomer (a-1), and 5 to 15 wt% of the monomer (a-2) having a glass transition temperature of 100 to 110 ° C. A copolymer of monomers containing
An aqueous re-peelable pressure-sensitive adhesive, wherein the tackifying resin (B) has a softening point of 120 to 180 ° C.   The aqueous re-peelable pressure-sensitive adhesive according to claim 1, wherein the polyol (D) is a glycol.   5 to 15 parts by weight of a tackifying resin (B) and 0.5 to 3.5 parts by weight of a carbodiimide group-containing compound (C) with respect to 100 parts by weight of an acrylic polymer (A) Item 3. The aqueous re-peelable pressure-sensitive adhesive according to Item 1 or 2.   The aqueous re-peelable pressure-sensitive adhesive according to any one of claims 1 to 3, wherein the tackifying resin (B) is at least one resin selected from the group consisting of a rosin resin, a terpene resin and a petroleum resin.   The aqueous re-peelable pressure-sensitive adhesive according to any one of claims 1 to 4, wherein the dry film formed from the aqueous re-peelable pressure-sensitive adhesive has a gel fraction by extraction with ethyl acetate of 45 to 75% by weight.   A re-peelable pressure-sensitive adhesive sheet comprising a base material and a pressure-sensitive adhesive layer formed from the aqueous re-peelable pressure-sensitive adhesive according to claim 1.