JP2021169594A - Aqueous pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and method for producing aqueous pressure-sensitive adhesive - Google Patents

Abstract

To provide an aqueous pressure-sensitive adhesive which has high adhesive force to various adherends, good adhesiveness to curved surfaces, high cohesive force under high temperature environment, and high adhesive force under low temperature environment and a method for producing the same, and a pressure-sensitive adhesive sheet using the same.SOLUTION: An aqueous pressure-sensitive adhesive contains first acrylic emulsion (AEL) containing a first acrylic copolymer (APL) having relatively low Tg, and second acrylic emulsion (AEH) containing a second acrylic copolymer (APH) having relatively high Tg and a tackifier resin. The first acrylic copolymer (APL) has Tg of -70 to -40°C, and the second acrylic copolymer (APH) has Tg of 60-120°C. The tackifier resin is a rosin-based resin having a softening point of 130°C or higher.SELECTED DRAWING: Figure 1

Description

The present invention relates to a water-based pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and a method for producing a water-based pressure-sensitive adhesive.

In recent years, in consideration of safety and health and the environment, pressure-sensitive adhesives are shifting from solvent-based adhesives to water-based adhesives. However, since dispersed particles are fused to each other to form a dry film in the drying step after coating, the water-based pressure-sensitive adhesive is a film obtained after coating and drying (compared to the solvent-based pressure-sensitive adhesive). The pressure-sensitive adhesive layer) tends to lack precision. Therefore, the pressure-sensitive adhesive sheet using the water-based pressure-sensitive adhesive is more curved than the pressure-sensitive adhesive sheet using the solvent-based pressure-sensitive adhesive. Tends to be inferior in sex.

"Curved surface stickability" is a term indicating suitability for sticking a pressure-sensitive adhesive sheet on an adherend having a curved surface. Unlike the case of pasting on a flat surface, when pasting on a curved surface, stress is generated on the base material of the pressure-sensitive adhesive sheet to restore the curved surface state to the flat state. This stress acts so that the pressure-sensitive adhesive sheet naturally peels off from the adherend. Therefore, if the adhesive strength of the adhesive layer is not sufficient, the pressure-sensitive adhesive sheet will naturally peel off from the adherend after a certain period of time has passed after the pressure-sensitive adhesive sheet is attached to the adherend. There is a fear.
Further, even though the adhesive force of the pressure-sensitive adhesive is sufficiently high, if the cohesive force of the pressure-sensitive adhesive is too low, the substrate cannot overcome the stress of returning to a flat state and breaks inside the adhesive layer. May occur, so-called "cohesive failure". When cohesive failure occurs, the pressure-sensitive adhesive sheet is peeled off from the adherend with the pressure-sensitive adhesive adhered to both the adherend side and the base material side of the pressure-sensitive adhesive sheet.
Therefore, in order to improve the adhesiveness of the curved surface, it is necessary that the two physical properties of the pressure-sensitive adhesive, that is, the adhesive force and the cohesive force, are suitable.

With the expansion of applications of water-based pressure-sensitive adhesives, water-based pressure-sensitive adhesives have good curved surface stickability and high cohesive force even in high-temperature environments, and are at room temperature and below 0 ° C. Even in a low temperature environment, it is required to have high adhesive strength to a wide range of adherends including low-polarity adherends such as polyolefin resins such as polyethylene.
If the cohesive force in a high temperature environment is high, it is possible to suppress poor adhesion such as positional deviation between the adherend and the pressure-sensitive adhesive sheet in a high temperature environment. Maintaining a good adhesive state between the adherend and the pressure-sensitive adhesive sheet in a high-temperature environment is also called "high-temperature holding force".

Patent Document 1 describes a low Tg polymer emulsion (A) having a glass transition temperature (Tg) of less than −40 ° C. and a high Tg polymer emulsion (B) having a glass transition temperature (Tg) of −40 ° C. to 0 ° C. An emulsion-type pressure-sensitive adhesive composition containing the cross-linking agent (C) and the pressure-sensitive adhesive resin (D) is disclosed (claim 1).

Patent Document 2 describes an aqueous dispersion type pressure-sensitive adhesive composition using an aqueous dispersion type acrylic copolymer (polymer L) having a glass transition temperature (Tg) in the range of −70 ° C. to −50 ° C. as a base polymer. An adhesive containing 0.5 to 15 parts by mass of an aqueous dispersion type acrylic copolymer (polymer H) having a Tg in the range of 30 to 120 ° C. with respect to 100 parts by mass of the polymer L on a solid content basis. The agent composition is disclosed (claim 1).
The pressure-sensitive adhesive composition preferably further contains 10 to 40 parts by mass of a tack-imparting resin with respect to 100 parts by mass of the polymer L on a solid content basis (Claim 7).

Patent Document 3 describes an oil-soluble component composed of an ethylenically unsaturated monomer (A) containing (meth) acrylic acid alkyl ester as a main component and a tackifier (B) in an aqueous medium using an emulsifying agent. In the presence of a resin emulsion obtained by polymerizing an emulsified solution emulsified so that the average particle size of the oil-soluble component is 1.0 μm or less, ethylene containing (meth) acrylic acid alkyl ester as a main component is further present. An emulsion-type pressure-sensitive adhesive composition obtained by polymerizing a sex-unsaturated monomer (E) is disclosed (claim 1).

In Patent Document 4,
An emulsion-type pressure-sensitive adhesive composition containing 51 to 90% by mass of a low Tg acrylic pressure-sensitive adhesive emulsion (A) as a main component and 10 to 49% by mass of a high Tg copolymer emulsion (B) as a sub-component. ,
The low Tg acrylic pressure-sensitive adhesive emulsion (A) has a glass transition temperature (Tg) of −70 to −50 ° C.
The high Tg copolymer emulsion (B) was emulsified and polymerized by allowing 20 to 200 parts by mass of a tackifier resin to be present in 100 parts by mass of a monomer mixture containing a (meth) acrylic acid alkyl ester-based monomer. An emulsion-type pressure-sensitive adhesive composition, which is an emulsion of a copolymer and has a glass transition temperature (Tg) of the copolymer of -30 to 30 ° C., is disclosed (claim 1).
The codes of the respective components described in Patent Documents 1 to 4 are the codes described in these documents and have nothing to do with the codes used for each component of the present invention.

Japanese Unexamined Patent Publication No. 2006-124691 JP-A-2010-95609 Japanese Unexamined Patent Publication No. 2003-96420 Japanese Patent No. 6183821

However, in the prior art described in Patent Documents 1 to 4, good curved surface stickability, high adhesive force to various adherends, high cohesive force in a high temperature environment (high temperature holding power), and high in a low temperature environment. It is difficult to achieve all the adhesive strength. In particular, curved surface stickability and low-temperature adhesiveness are contradictory characteristics, and it is difficult to achieve both.

An object of the present invention is a water-based pressure-sensitive type having high adhesive force to various adherends, good curved surface sticking property, high cohesive force (high temperature holding force) in a high temperature environment, and high adhesive force in a low temperature environment. An adhesive, a method for producing the same, and a pressure-sensitive adhesive sheet using the adhesive.

The water-based pressure-sensitive adhesive of the present invention
A first acrylic emulsion (AEL) containing a first acrylic copolymer (APL) having a relatively low glass transition temperature (Tg),
A water-based pressure-sensitive adhesive containing a second acrylic copolymer (APH) having a relatively high glass transition temperature (Tg) and a second acrylic emulsion (AEH) containing a tackifier resin.
The glass transition temperature of the first acrylic copolymer (APL) is −70 to −40 ° C.
The glass transition temperature (Tg) of the second acrylic copolymer (APH) is 60 to 120 ° C.
The tackifier resin is a water-based pressure-sensitive adhesive which is a rosin-based resin having a softening point of 130 ° C. or higher.

The method for producing a water-based pressure-sensitive adhesive of the present invention is
A first acrylic emulsion (AEL) containing a first acrylic copolymer (APL) having a relatively low glass transition temperature (Tg),
A method for producing an aqueous pressure-sensitive adhesive containing a second acrylic copolymer (APH) having a relatively high glass transition temperature (Tg) and a second acrylic emulsion (AEH) containing a tackifier resin. There,
A first acrylic emulsion (AEL) containing a first acrylic copolymer (APL) having a glass transition temperature of −70 to −40 ° C. by emulsion polymerization of a plurality of types of ethylenically unsaturated monomers. (1) and
In the presence of an emulsifier and a tackifier resin which is a rosin-based resin having a softening point of 130 ° C. or higher, a plurality of types of ethylenically unsaturated monomers are emulsion-polymerized to have a glass transition temperature (Tg) of 60 to 120. A step (2) of producing a second acrylic emulsion (AEH) containing a second acrylic copolymer (APH) at ° C.
It has a step (3) of mixing a first acrylic emulsion (AEL) and a second acrylic emulsion (AEH).

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer made of a dried product of the above-mentioned water-based pressure-sensitive adhesive of the present invention.

According to the present invention, a water-based pressure-sensitive type having high adhesive force to various adherends, good curved surface sticking property, high cohesive force (high temperature holding force) in a high temperature environment, and high adhesive force in a low temperature environment. An adhesive, a method for producing the same, and a pressure-sensitive adhesive sheet using the same can be provided.
The pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer formed by using the water-based pressure-sensitive adhesive of the present invention can be placed between the adherend and the pressure-sensitive adhesive sheet even in a high temperature environment after being attached to the adherend. Poor adhesion such as misalignment can be suppressed. This pressure-sensitive adhesive sheet can have good adhesive force even for an adherend having a curved surface shape and a low-polarity adherend such as a polyolefin resin which is generally difficult to adhere. This pressure-sensitive adhesive sheet can have good adhesive force even in a low temperature environment even for a low-polarity adherend such as a polyolefin resin, which is generally difficult to adhere.

It is a micrograph of the pressure-sensitive adhesive layer obtained in Example 1. It is a scanning probe micrograph of the pressure-sensitive adhesive layer obtained in Comparative Example 2.

The details of the present invention will be described below.
In the present specification, unless otherwise specified, the "monomer" is an ethylenically unsaturated monomer and is a general term for radically polymerizable vinyl group-containing compounds including a (meth) acrylic acid alkyl ester monomer. Is. In the present specification, unless otherwise specified, the glass transition temperature (Tg) of the acrylic copolymer is a theory theoretically obtained by the FOX formula based on the Tg of the homopolymer of each raw material monomer. The value. For Tg of the homopolymer, well-known values described in various handbooks and publicly known documents can be used.

[Aqueous pressure-sensitive adhesive]
The water-based pressure-sensitive adhesive of the present invention contains two types of acrylic emulsions. Specifically, the glass transition temperature (Tg) is relatively different from that of the first acrylic emulsion (AEL) containing the first acrylic copolymer (APL) having a relatively low glass transition temperature (Tg). It contains a second acrylic emulsion (AEH) containing a high second acrylic copolymer (APH) and a tackifier resin (TF).

The water-based pressure-sensitive adhesive of the present invention has a phase-separated structure and can contain a phase-separated domain containing a second acrylic copolymer (APH) and a tackifier resin (TF).
In general, acrylic copolymers having a low Tg tend to be relatively soft, have high adhesive strength at low temperatures, and have high adhesive strength to low-polarity adherends such as polyolefin resins, and have low cohesive strength. In general, an acrylic copolymer having a high Tg tends to be relatively hard, has a low adhesive force particularly at a low temperature, and has a high cohesive force. By simply adding a tackifier resin to these two types of acrylic emulsions, a relatively large number of them are used to improve the adhesive force to low-polarity adherends such as polyolefin resins and the adhesiveness to curved surfaces. Adhesive-imparting resin is required. In this case, the flexibility of the pressure-sensitive adhesive is impaired, and the low-temperature adhesive force tends to decrease.
In the water-based pressure-sensitive adhesive of the present invention, the pressure-sensitive adhesive resin (TF) is formed by forming a phase-separated domain containing a second acrylic copolymer (APH) having a relatively high Tg and a pressure-sensitive adhesive resin (TF). Even if the amount of the second acrylic copolymer (APH) added is small, the hardness and low adhesive strength of the second acrylic copolymer (APH) can be effectively alleviated.

The presence or absence of phase separation or the phase separation state can be confirmed by observing a scanning probe microscope of a pressure-sensitive adhesive layer made of a water-based pressure-sensitive adhesive or a dried product of the water-based pressure-sensitive adhesive.
The presence or absence of phase separation or the phase separation state can also be evaluated using the haze value of the pressure-sensitive adhesive layer made of the dried product of the water-based pressure-sensitive adhesive of the present invention as an index. The haze value of the laminate obtained by applying and drying a water-based pressure-sensitive adhesive on a 50 μm-thick polyethylene terephthalate (PET) film under ^{the condition of a dry mass of 25 g / m 2 is preferably 5.0 to 10.} It is 0, more preferably 6.0 to 8.0. If the haze value of the laminate is 5.0 or more, phase separation is clearly seen in the pressure-sensitive adhesive layer, and if it exceeds 10.0, phase separation is clearly seen in the pressure-sensitive adhesive layer, but the pressure-sensitive type. The flexibility of the adhesive layer tends to decrease, which is not preferable. When the haze value of the laminated body is 6.0 to 10.0, the balance between the phase separation and the flexibility of the pressure-sensitive adhesive layer is good.
Adhesive to the second acrylic copolymer (APH), which has a high Tg and is relatively hard, in the matrix phase (sea phase) containing the first acrylic copolymer (APL), which has a low Tg and is relatively soft. By forming a plurality of phase-separated domains (island phases) including the imparting resin (TF), low-temperature adhesive strength, curved surface adhesiveness, adhesive strength to low-polarity adherends such as polyolefin resins, and high temperature environment The balance of cohesive force (high temperature holding force) is good.

The water-based pressure-sensitive adhesive of the present invention contains the above two types of acrylic emulsions, so that it has high adhesive force to various adherends, good curved surface adhesiveness, and high cohesive force (high temperature holding power) in a high temperature environment. ) And high adhesive strength in a low temperature environment.
The pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer formed by using the water-based pressure-sensitive adhesive of the present invention can be placed between the adherend and the pressure-sensitive adhesive sheet even in a high temperature environment after being attached to the adherend. Poor adhesion such as misalignment can be suppressed. This pressure-sensitive adhesive sheet can have good adhesive force even for an adherend having a curved surface shape and a low-polarity adherend such as a polyolefin resin which is generally difficult to adhere. This pressure-sensitive adhesive sheet can have good adhesive force even in a low temperature environment even for a low-polarity adherend such as a polyolefin resin, which is generally difficult to adhere.

The "high temperature environment" is a temperature environment higher than normal temperature (20 to 25 ° C.), for example, a temperature environment of 60 to 90 ° C.
The "low temperature environment" is a temperature environment lower than normal temperature (20 to 25 ° C.), for example, a temperature environment of 25 to 5 ° C.

The softening point of the tackifier resin (TF) is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, particularly preferably 130 ° C. or higher, and most preferably 150 ° C. or higher.
The higher the softening point of the tackifier resin (TF), the more preferably 130 ° C. or higher, so that the cohesive force of the adhesive containing the adhesive can be effectively increased, and various adherends can be used with a smaller amount. It can have a high adhesive force against, good curved surface sticking property, a high cohesive force (high temperature holding force) in a high temperature environment, and a high adhesive force in a low temperature environment.

The weight average molecular weight (Mw) of the tackifier resin (TF) is not particularly limited, and is preferably 1700 to 4500, more preferably 2800 to 4000. If the Mw of the tackifier resin (TF) is within the above range, the cohesive force of the adhesive containing the adhesive can be effectively increased, and with a smaller amount of use, the adhesive force to various adherends is high and good. It can have a smooth curved surface sticking property, a high cohesive force (high temperature holding power) in a high temperature environment, and a high adhesive force in a low temperature environment.
In the present specification, unless otherwise specified, "weight average molecular weight (Mw)" is a polystyrene-equivalent weight average molecular weight determined by a gel permeation chromatography (GPC) method.

As described above, in the water-based pressure-sensitive adhesive of the present invention, the amount of the tackifier resin (TF) used can be small. Since the amount of the tackifier resin (TF) used may be small, it is preferable from the viewpoints of reducing the cost of raw materials, high cohesive force (high temperature holding power) in a high temperature environment, low temperature adhesive force, and low yellowing of the pressure-sensitive adhesive. ..
In the conventional general acrylic water-based pressure-sensitive adhesive, the content of the tackifier resin is more than 6 parts by mass with respect to 100 parts by mass of the total amount of the acrylic copolymer.
In the water-based pressure-sensitive adhesive of the present invention, for example, the tackifier resin (TF) is applied to 100 parts by mass of the total amount of the first acrylic copolymer (APL) and the second acrylic copolymer (APH). ) Can be 1.0 part by mass or more and less than 5.5 parts by mass. The content of the tackifier resin (TF) is preferably 5.0 parts by mass or less, more preferably 4.5 parts by mass or less, and particularly preferably 4.0 parts by mass or less. The content of the tackifier resin (TF) is preferably 1.5 parts by mass or more.

In the water-based pressure-sensitive adhesive of the present invention, the first acrylic copolymer weight is relative to 100 parts by mass of the total amount of the first acrylic copolymer (APL) and the second acrylic copolymer (APH). The content of the coalescence (APL) is preferably 80 to 95 parts by mass, and the content of the second acrylic copolymer (APH) is preferably 20 to 5 parts by mass.
When the content of the first acrylic copolymer (APL) is within the above range, the adhesive strength to a low-polarity adherend such as a polyolefin resin and the low-temperature adhesiveness are excellent. When the content of the second acrylic copolymer (APH) is within the above range, it is possible to achieve both curved surface stickability and high cohesive force (high temperature holding force) in a high temperature environment.
The content of the first acrylic copolymer (APL) is 87 to 87 to 100 parts by mass of the total amount of the first acrylic copolymer (APL) and the second acrylic copolymer (APH). It is more preferably 92 parts by mass and the content of the second acrylic copolymer (APH) is 13 to 8 parts by mass.

(First acrylic emulsion (AEL))
The first acrylic emulsion (AEL) contains a first acrylic copolymer (APL) having a relatively low glass transition temperature (Tg). The Tg of the first acrylic copolymer (APL) is −70 to −40 ° C. This emulsion is the main component of the water-based pressure-sensitive adhesive of the present invention and contributes to the development of basic adhesive performance. The first acrylic emulsion (AEL) can be used alone or in combination of two or more.

The first acrylic emulsion (AEL) can be produced by a known emulsion polymerization method, and in the presence of an emulsifier, an ethylenically unsaturated monomer mixture (AML) containing a plurality of kinds of ethylenically unsaturated monomers can be prepared. Obtained by emulsion polymerization.
A plurality of types of ethylenically unsaturated monomers as raw materials are selected so that the Tg of the first acrylic copolymer (APL) is in the range of −70 to −40 ° C., and the polymerization conditions are determined. If the Tg of the first acrylic copolymer (APL) is less than −70 ° C., the adhesive strength to the adherend, particularly to a low-polarity adherend such as a polyolefin resin, and the adhesiveness to a curved surface become insufficient. There is a fear. If Tg exceeds −40 ° C., the tack feeling may be lowered and the adhesive strength (particularly low temperature adhesive strength) may be lowered. Tg is more preferably −65 to −50 ° C., particularly preferably −60 to −45 ° C.

<Ethylene unsaturated monomer mixture (AML)>
The first acrylic emulsion (AEL) is an emulsion polymer of an ethylenically unsaturated monomer mixture (AML).
The ethylenically unsaturated monomeric mixture (AML) comprises one or more (meth) acrylic acid alkyl esters, which are esters of linear or branched alcohols with (meth) acrylic acid, and optionally. It can contain one or more other monomers.

Examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, and n-octyl (meth) acrylate. Examples thereof include 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, myristyl (meth) acrylate, and stearyl acrylate. These can be used alone or in combination of two or more.
Above all, it is preferable to use a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 14 carbon atoms in order to improve the tackiness and the adhesive strength of the water-based pressure-sensitive adhesive.
The ethylenically unsaturated monomer mixture (AML) preferably contains butyl acrylate (BA), and more preferably contains butyl acrylate (BA) and 2-ethylhexyl acrylate (2-EHA).
The content of the (meth) acrylic acid alkyl ester in the ethylenically unsaturated monomer mixture (AML) is preferably 40.0 to 99.5% by mass, preferably 40.0 to 98.0% by mass, and more. It is preferably 90 to 99% by mass. In particular, when the content of butyl acrylate is 40 to 98% by mass, it is preferable because good curved surface stickability and good adhesive strength can be achieved at the same time.

Other monomers include an ethylenically unsaturated monomer having a carboxy group, an ethylenically unsaturated monomer having a hydroxyl group, an ethylenically unsaturated monomer having an amide bond, and a styrene-based unsaturated monomer. , And vinyl compounds and the like.

Examples of the ethylenically unsaturated monomer having a carboxy group include (meth) acrylic acid, carboxyethyl (meth) acrylic acid, maleic acid, fumaric acid, and itaconic acid. These can be used alone or in combination of two or more. Of these, (meth) acrylic acid is preferable from the viewpoint of emulsion stability.
The content of the ethylenically unsaturated monomer having a carboxy group in the ethylenically unsaturated monomer mixture (AEL) is preferably 0.5 to 2.0% by mass. When the content is within this range, the generation of agglomerates during synthesis is suppressed, and an emulsion with good handling after neutralization can be easily obtained.
One or more single amounts having an acid group in an ethylenically unsaturated monomer mixture (AML) from the viewpoint of suppressing deterioration over time when a pressure-sensitive adhesive sheet is attached to an adherend such as paper. The total amount of the body is preferably 1.0% by mass or less.

Examples of the ethylenically unsaturated monomer having a hydroxyl group include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate. These can be used alone or in combination of two or more.
When the ethylenically unsaturated monomer mixture (AML) contains an ethylenically unsaturated monomer having a hydroxyl group, the ethylenically unsaturated monomer having a hydroxyl group in the ethylenically unsaturated monomer mixture (AML) The content is preferably 2 to 10% by mass, more preferably 3% by mass or more and less than 6% by mass. In this case, the adhesiveness of the curved surface can be further improved.

Examples of the ethylenically unsaturated monomer having an amide bond include (meth) acrylamide and diacetone (meth) acrylamide. These can be used alone or in combination of two or more.

Examples of the styrene-based unsaturated monomer include styrene; nuclear alkyl-substituted styrenes such as 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-ethylstyrene, and 4-tert-butylstyrene; α-. Examples thereof include methyl styrene and α-alkyl substituted styrene such as 4-methyl-α-methyl styrene. These can be used alone or in combination of two or more.

Other ethylenically unsaturated monomers other than the above can be used as long as the effects of the present invention are not impaired. Examples of other ethylenically unsaturated monomers include methoxyethyl (meth) acrylate, acetoacetoxyethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and N, N-diethylaminoethyl (meth). Acrylate, vinylpyrrolidone, vinylpyridine, vinyl acetate, vinyl propionate, styrene, (meth) acrylonitrile, butadiene, chloroprene and the like can be mentioned. These can be used alone or in combination of two or more.

<Emulsifier>
As the emulsifier used for the synthesis of the first acrylic emulsion (AEL), a known reactive or non-reactive emulsifier can be used. One type or two or more types of emulsifiers can be used.

Examples of reactive emulsifiers are as follows.
Examples of anionic emulsifiers include nonylphenyl skeleton anionic emulsifiers (ADEKA's "ADEKA RIA SOLP SE-10N", Daiichi Kogyo Seiyaku Co., Ltd. "Aqualon HS-10, HS-20", etc.) and long-chain alkyl skeletons. Anionic emulsifiers (Aquaron KH-05, KH-10 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., ADEKA "Adecaria Soap SR-10N", etc.), anionic emulsifiers with phosphoric acid ester skeleton (manufactured by Nippon Kayaku Co., Ltd.) "KAYARAD" etc.) can be exemplified.
Examples of the nonionic emulsifier include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, sorbitan higher fatty acid esters, glycerin higher fatty acid esters and the like. These nonionic emulsifiers have an unsaturated double bond at the terminal or intermediate portion of the molecule and can be copolymerized with a monomer. Commercially available nonionic emulsifiers include "ADEKA Adecaria Soap NE-10" manufactured by ADEKA, "Aqualon RN-10, RN-20, RN-50" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., and "Antox NA" manufactured by Nippon Emulsifier Co., Ltd. -16 ”and the like can be exemplified.

Examples of non-reactive emulsifiers are as follows.
Examples of anionic emulsifiers include higher fatty acid salts such as sodium stearate; alkylaryl sulfonates such as sodium dodecylbenzene sulfonate; alkyl sulfate esters such as sodium lauryl sulfate; polyoxyethylene polyoxyethylene such as sodium lauryl ether sulfate. Alkyl ether sulfate ester salts; Examples thereof include polyoxyethylene alkylaryl ether sulfate ester salts such as polyoxyethylene nonylphenyl ether sulfate sodium.
Nonionic emulsifiers include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene nonylphenyl ether; sorbitan higher fatty acid esters such as sorbitan monostearate; oleic acid. Examples thereof include glycerin higher fatty acid esters such as monoglyceride.

<Polymerization initiator>
Examples of the polymerization initiator used for the synthesis of the first acrylic emulsion (AEL) include persulfates such as potassium persulfate and ammonium persulfate; azobis-based cationic salts; and water-soluble thermal decomposition type polymerizations such as hydroxyl group addition substances. Catalyst: A redox-based polymerization catalyst can be used.
Examples of the redox-based polymerization catalyst include a combination of an organic peroxide such as t-butyl hydroperoxide, benzoyl peroxide, and cumene hydroperoxide and a reducing agent such as longalite and / or sodium metabisulfite; Combinations of peroxides such as potassium sulfate and ammonium persulfate with longalite and / or sodium thiosulfate; combinations of hydrogen peroxide solution and ascorbic acid and the like can be mentioned.

<Chain transfer agent>
For the synthesis of the first acrylic emulsion (AEL), mercaptans, thioglycols, and β-mercaptopropions are used to control the molecular weight and / or molecular weight distribution of the first acrylic copolymer (APL). A chain transfer agent such as a thiol-based compound such as an acid can be used. The amount used is preferably 0.01 to 1.0 parts by mass with respect to 100 parts by mass of the ethylenically unsaturated monomer mixture (AEL).

(Method for Producing First Acrylic Emulsion (AEL))
The first acrylic emulsion (AEL) containing the first acrylic copolymer (APL) having a glass transition temperature (Tg) of −70 to −40 ° C. contains a plurality of types of ethylenically unsaturated monomers. It is obtained by emulsion polymerization of an ethylenically unsaturated monomer mixture (AML) containing the mixture (step (1)).
In emulsion polymerization, a mixture of a plurality of types of ethylenically unsaturated monomers is polymerized in an aqueous medium using an emulsifier and a polymerization initiator.

First, a plurality of types of ethylenically unsaturated monomers are mixed to obtain a uniform monomer mixed solution (ethylene unsaturated monomer mixture (AML)). If necessary, water and a part or all of the emulsifier may be added to this mixed solution and mixed to obtain an emulsion.
The above mixed solution (ethylene unsaturated monomer mixture (AML)) or an emulsion containing the above mixed solution is used as a raw material solution for polymerization, and polymerization is carried out in the presence of a polymerization initiator. At this time, the whole amount of the raw material liquid may be charged into the reaction vessel to start the polymerization, or a part of the raw material liquid may be charged into the reaction vessel to start the polymerization, and then the remaining raw material liquid may be charged once or multiple times. It may be added separately, or a part of the raw material liquid may be charged in a reaction vessel to start polymerization and then the remaining raw material liquid may be continuously added dropwise, or a part or all of the water and, if necessary, may be added in advance. A part or all of the emulsifier may be charged in the reaction vessel, and the whole amount of the raw material liquid may be continuously added dropwise.
When a monomer mixed solution (ethylenically unsaturated monomer mixture (AML)) is used as the raw material liquid, it is preferable to charge the reaction vessel in advance with the entire amount of the emulsifier and a part or the whole amount of water.

The entire amount of the polymerization initiator may be charged in the reaction vessel in advance, the entire amount may be added after the temperature is raised, or a part of the polymerization initiator may be charged in the reaction vessel and the rest may be charged once after the polymerization is started. Alternatively, it may be added in a plurality of times, a part thereof may be charged in a reaction vessel and the polymerization may be started, and then the rest may be continuously added dropwise, or the entire amount may be continuously added dropwise.
When the polymerization initiator is added separately or continuously added dropwise, the polymerization initiator may be added separately or continuously added dropwise into the reaction vessel, or may be added separately or continuously added dropwise in a state of being mixed with the raw material solution. .. After adding the polymerization initiator by the above method, the polymerization initiator may be additionally added once or twice or more for the purpose of increasing the reaction rate.

At the time of polymerization, a pH buffer may be used to adjust the pH.
When a monomer having a carboxy group is used, a part or all of the carboxy group contained in the obtained copolymer is used as a base such as ammonia, an organic amine, potassium hydroxide, sodium citrate, and sodium hydroxide. It may be neutralized with a sex compound.

(Second acrylic emulsion (AEH))
The second acrylic emulsion (AEH) is an emulsion containing a second acrylic copolymer (APH) having a relatively high glass transition temperature (Tg). The Tg of the second acrylic copolymer (APH) is 60 to 120 ° C. The second acrylic emulsion (AEH) can be used alone or in combination of two or more.
The second acrylic copolymer (APH) is an ethylenically unsaturated monomer mixture (AMH) containing a plurality of kinds of ethylenically unsaturated monomers in the presence of an emulsifier and a tackifier resin (TF). Obtained by emulsion polymerization.
The amount of the tackifier resin (TF) used with respect to 100 parts by mass of the ethylenically unsaturated monomer mixture (AMH) is not particularly limited, and is preferably 10 to 60 parts by mass.

A plurality of types of ethylenically unsaturated monomers as raw materials are selected so that the Tg of the second acrylic copolymer (APH) is 60 to 120 ° C., and the polymerization conditions are determined. When the Tg of the second acrylic copolymer (APH) is in the above range, it is possible to achieve both good adhesive strength / curved surface stickability and good holding power. Tg is more preferably 80 to 115 ° C, particularly preferably 90 to 110 ° C.

<Ethylene unsaturated monomer mixture (AMH)>
The second acrylic emulsion (AEH) is an emulsion polymer of an ethylenically unsaturated monomer mixture (AMH).
The ethylenically unsaturated monomeric mixture (AMH) comprises one or more (meth) acrylic acid alkyl esters, which are esters of linear or branched alcohols with (meth) acrylic acid, and optionally. It can contain one or more other monomers. Examples of the (meth) acrylic acid alkyl ester and other monomers are similar to the ethylenically unsaturated monomer mixture (AML).

The content of the (meth) acrylic acid alkyl ester in the ethylenically unsaturated monomer mixture (AMH) is preferably 80.0 to 99.5% by mass, preferably 90.0 to 99.0% by mass. It is preferably 97.0 to 98.5% by mass.
The ethylenically unsaturated monomer mixture (AMH) preferably contains methyl methacrylate (MMA), more preferably methyl methacrylate (MMA) and acrylic acid (AA).
When the content of methyl methacrylate (MMA) in the ethylenically unsaturated monomer mixture (AMH) is 80% by mass or more, the tackifier resin (TF) is dissolved and the pressure-sensitive adhesive sheet has a curved surface stickability. It is preferable because it facilitates improvement and improvement of cohesive force (high temperature holding force) in a high temperature environment.

When the ethylenically unsaturated monomer mixture (AMH) contains an ethylenically unsaturated monomer having a carboxy group, it is ethylenically having a carboxy group in 100% by mass of the ethylenically unsaturated monomer mixture (AMH). The content of the unsaturated monomer is preferably 0.5 to 5.0% by mass, more preferably 1.0 to 3.0% by mass. When the amount used is within this range, the generation of agglomerates during synthesis is suppressed, and an emulsion with good handling after neutralization can be easily obtained.

<Adhesive-imparting resin (TF)>
As the tackifier resin (TF), a resin that dissolves or disperses in an ethylenically unsaturated monomer mixture (AMH) can be used. Examples of the tackifier resin (TF) include rosin-based resin, terpene-based resin, kumaron inden resin, phenol resin, xylene resin, aliphatic hydrocarbon resin, and aromatic hydrocarbon resin.
Among them, a rosin-based resin, a terpene-based resin, and an aromatic hydrocarbon resin are preferable, a rosin-based resin is more preferable, and a polymerized rosin ester resin is particularly preferable, from the viewpoint of improving the adhesiveness to a curved surface. Examples of the rosin-based resin include natural rosin, rosin ester, hydrogenated rosin, hydrogenated rosin ester, polymerized rosin, polymerized rosin ester, disproportionated rosin, and disproportionated rosin ester. Examples of the terpene resin include α-pinene resin, β-pinene resin, terpene phenol resin and the like. Examples of the aromatic hydrocarbon resin include copolymers of styrene and α-methylstyrene. One type or two or more types of tackifier resin (TF) can be used.

From the viewpoint of adhesive strength and curved surface stickability, the tackifier resin (TF) preferably has a softening point of 100 ° C. or higher, more preferably 120 ° C. or higher, and particularly preferably 130 ° C. or higher. , 150 ° C. or higher is most preferable.
Examples of the commercially available tackifier resin (TF) include Pencel D-125 (manufactured by Arakawa Chemical Industries, Ltd.), which is a polymerized rosin ester having a softening point of 125 ° C., and Pencel D-160 (manufactured by Arakawa Chemical Industries, Ltd.), which is a polymerized rosin ester having a softening point of 160 ° C. Arakawa Chemical Industry Co., Ltd.), PINEREZ2410 (manufactured by LAWSTER), a rosin ester with a softening point of 100 ° C., YS resin PX1150 (manufactured by Yasuhara Chemical Co., Ltd.), a terpene resin with a softening point of 115 ° C., and a terpene phenol resin with a softening point of 160 ° C. YS Polystar T160 (manufactured by Yasuhara Chemical Co., Ltd.) and the like.
The tackifier resin (TF) may be synthesized and used by a known method (see Production Examples 21 to 25 in the section [Example] below).

From the viewpoint of adhesive strength and curved surface stickability, the tackifier resin (TF) is preferably a rosin-based resin having a softening point of 130 ° C. or higher, and particularly preferably a polymerized rosin ester resin having a softening point of 130 ° C. or higher.

The absolute value of the temperature difference (Td) represented by the following formula (1) (the temperature difference between the glass transition temperature (Tg) of the second acrylic copolymer (APH) and the softening point of the tackifier resin (TF)). ) Is preferably 100 ° C. or lower, more preferably 80 ° C. or lower. When this temperature difference is 100 ° C. or less, it is possible to effectively achieve both good curved surface stickability, high adhesive strength, and holding power.
Either the Tg of the second acrylic copolymer (APH) or the softening point of the tackifier resin (TF) may be higher. The softening point of the tackifier resin (TF) is preferably higher than the Tg of the second acrylic copolymer (APH), in which case good curved surface stickability, high adhesive strength and holding power are more effective. Can be compatible with.

Equation (1):
[Temperature difference (Td) (° C.)] = | [Tg (° C.) of the second acrylic copolymer (APH)]-[Softening point (° C.) of the tackifier resin (TF)] |

(Method for Producing Second Acrylic Emulsion (APH))
The second acrylic emulsion (APH) containing the second acrylic copolymer (APH) having a glass transition temperature (Tg) of 60 to 120 ° C. is in the presence of an emulsifier and a tackifier resin (TF). It is obtained by emulsion polymerization of an ethylenically unsaturated monomer mixture (AMH) containing a plurality of types of ethylenically unsaturated monomers (step (2)).
The amount of the tackifier resin (TF) used is not particularly limited, and is preferably 10 to 60 parts by mass with respect to 100 parts by mass of the ethylenically unsaturated monomer mixture (AMH). The lower limit is more preferably 20 parts by mass, and particularly preferably 30 parts by mass. The upper limit is more preferably 50 parts by mass. When the amount used is within this range, it is possible to achieve both good adhesive strength / curved surface stickability and holding power, and it is possible to suppress the generation of agglomerates during emulsion synthesis.

Step (2) is
The step (2-a) of dissolving the tackifier resin (TF) in the ethylenically unsaturated monomer mixture (AMH), and
The step (2-b) of forcibly emulsifying the obtained mixed solution in the presence of an emulsifier and water to obtain an emulsion,
It is preferable to include a step (2-c) of emulsion polymerization of the obtained emulsion.

The step (2) including the steps (2-a) to (2-c) uses an organic solvent for suppressing the generation of agglomerates during polymerization and for dissolving the tackifier resin (TF) during polymerization. It is preferable in that it does not have to be done.
When a monomer having a carboxy group is used, in step (2), if necessary, a part or all of the carboxy group contained in the copolymer obtained in step (2-c) is added to ammonia. The step (2-d) of neutralizing with a basic compound such as an organic amine, potassium hydroxide, sodium citrate, and sodium hydroxide can be included.

Examples of emulsifiers, polymerization initiators, and chain transfer agents suitable for use in emulsion polymerization are similar to those of the first acrylic emulsion (AEL).

The emulsion obtained in step (2-b) contains a plurality of ethylenically unsaturated monomers, a tackifier resin (TF), a surfactant, and water. The average particle size of the oil-soluble component contained in this emulsion is not particularly limited, and is preferably 0.3 to 2.0 μm from the viewpoint of suppressing the formation of agglomerates during emulsion synthesis and the stability of the emulsion on standing. , More preferably 0.4 to 1.5 μm, and particularly preferably 0.5 to 1.2 μm. If the average particle size of the oil-soluble component is less than 0.3 μm, the viscosity of the emulsion becomes too high, and the energy and time required for forced emulsification increase, which may reduce productivity. If the average particle size of the oil-soluble component exceeds 2.0 μm, agglomerates may be generated during emulsion synthesis.
In the present specification, unless otherwise specified, the "average particle size of the oil-soluble component of the emulsion" is the cumulative volume average diameter when the oil droplet diameter in water is measured by a dynamic light scattering method, for example. It is an average particle size value (median diameter D50) measured by the Microtrac UPA particle size distribution meter manufactured by Nikkiso Co., Ltd.

As the emulsifying machine used for forced emulsification, known emulsifying machines such as a rotary continuous emulsifying machine, a colloid mill type emulsifying machine, a high pressure homogenizer type emulsifying machine, and an ultrasonic treatment type emulsifying machine can be used. Among them, the rotor / stator type high-speed rotary continuous emulsifier, which is one of the rotary continuous emulsifiers, makes it easy to obtain an emulsion having a suitable average particle size of oil-soluble components, is easy to maintain, and per unit time. It is preferable because the amount of processing is large.

As the emulsion polymerization method performed in the step (2-c), the same method as the emulsion polymerization of the first acrylic emulsion (AEL) can be used. In step (2-b), by adjusting the average particle size (median size) of the oil-soluble component contained in the emulsion of the monomer mixture and the tackifier resin (TF), the performance of the water-based adhesive can be improved. An excellent emulsion can be obtained.

The amount of the emulsifier used in the production of the second acrylic emulsion (AEH) (the amount used here is the amount of the active ingredient) is tack-imparted with the ethylenically unsaturated monomer mixture (AMH). It is preferably 1.0 to 4.0 parts by mass, and more preferably 1.5 to 3.5 parts by mass with respect to 100 parts by mass of the total of the resin (TF). When the amount of the emulsifier used is 1.0 part by mass or more, the generation of agglomerates during emulsion production can be suppressed, and when it is 4.0 parts by mass or less, the curved surface stickability of the pressure-sensitive adhesive sheet can be applied. Is better.

(Manufacturing method of water-based pressure-sensitive adhesive)
The manufacturing method of the water-based pressure-sensitive adhesive is
The above step (1) and
The above step (2) and
It has a step (3) of mixing the first acrylic emulsion (AEL) obtained in the step (1) and the second acrylic emulsion (AEH) obtained in the step (2).
Various additives may be added before, during, or after mixing the first acrylic emulsion (AEL) and the second acrylic emulsion (AEH). Examples of additives include leveling agents, defoaming agents, viscosity modifiers, preservatives, tackifiers for adjusting adhesive strength, plasticizers, fillers, colorants, silane coupling agents and the like.
Examples of the post-added tackifier include rosin-based resin, phenol resin, polyterpene, acetylene resin, petroleum-based hydrocarbon resin, ethylene-vinyl acetate copolymer, synthetic rubber, and natural rubber.

Any cross-linking agent may be blended in order to cross-link between the dispersed particles of the copolymer.
For example, when a monomer having a hydroxyl group is used as the raw material monomer of the first acrylic emulsion (AEL) or the second acrylic emulsion (AEH), the cross-linking agent is an isocyanate compound; titanium, zirconium, or the like. An alkoxide compound or the like can be used.
When a monomer having a carbonyl group is used as the raw material monomer of the first acrylic emulsion (AEL) or the second acrylic emulsion (AEH), amines, hydrazide compounds and the like should be used as the cross-linking agent. Can be done.
When a monomer having a carboxy group is used as the raw material monomer of the first acrylic emulsion (AEL) or the second acrylic emulsion (AEH), the carbodiimide compound; epoxy compound; aziridine compound; A metal compound such as zinc oxide can be used.

[Pressure-sensitive adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer made of a dried product of the above-mentioned water-based pressure-sensitive adhesive of the present invention. The pressure-sensitive adhesive layer can be formed by applying the water-based pressure-sensitive adhesive of the present invention onto a base material or a release liner and drying it.

Examples of the base material include polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, polyester resins such as polyethylene terephthalate, vinyl acetate resins, polyimide resins, fluororesins, and polyvinyl chloride resins. , And a resin film made of a resin material such as cellophane; a rubber sheet made of natural rubber and butyl rubber; a foam sheet made by foaming polyurethane, polychloroprene rubber, polyethylene, etc .; paper such as kraft paper, crepe paper, and Japanese paper. Cloths such as cotton cloth and sufu cloth; non-woven fabrics such as cellulose-based non-woven fabrics, polyester non-woven fabrics, and vinylon non-woven fabrics; metal foils such as aluminum foil and copper foil; composite materials thereof and the like.
One side or both sides of such a sheet-shaped base material may be subjected to surface treatment such as application of a primer and corona discharge treatment. The thickness of the base material can be appropriately selected depending on the intended use and the like, and is generally 10 to 500 μm, typically 10 to 200 μm.

As the release liner (also referred to as a release sheet or separator), a known one can be used, and one in which at least one surface of the base material is treated with a release agent such as a fluororesin or a silicone resin is preferable. As the base material, for example, a paper / resin composite material obtained by laminating a resin film such as polyethylene on paper such as glassin paper, kraft paper, and clay-coated paper, or coating a resin such as polyvinyl alcohol and acrylic polymer. Is preferable.

As the coating device, various known coating devices such as a comma coater, a reverse coater, a slot die coater, a lip coater, a gravure chamber coater, and a curtain coater can be used.
The drying temperature is not particularly limited, and is preferably 80 to 120 ° C. If the drying temperature is less than 80 ° C., the drying is slow and it takes a long time to dry. Drying at a temperature higher than 120 ° C. may cause thermal deterioration of the base material or the release liner, which is not preferable.

As described above, according to the present invention, high adhesive force to various adherends, good curved surface adhesiveness, high cohesive force (high temperature holding force) in a high temperature environment, and high adhesive force in a low temperature environment. It is possible to provide an aqueous pressure-sensitive adhesive having the above, a method for producing the same, and a pressure-sensitive adhesive sheet using the same.
The pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer formed by using the water-based pressure-sensitive adhesive of the present invention can be placed between the adherend and the pressure-sensitive adhesive sheet even in a high temperature environment after being attached to the adherend. Poor adhesion such as misalignment can be suppressed. This pressure-sensitive adhesive sheet can have good adhesive force even for an adherend having a curved surface shape and a low-polarity adherend such as a polyolefin resin which is generally difficult to adhere. This pressure-sensitive adhesive sheet can have good adhesive force even in a low temperature environment even for a low-polarity adherend such as a polyolefin resin, which is generally difficult to adhere.

Examples and comparative examples according to the present invention will be described. Unless otherwise specified, "parts" indicates "parts by mass" and "%" indicates "% by mass". The blending amounts of components other than water and solvent are non-volatile content conversion values. "RH" indicates relative humidity.

A method for measuring the average particle size of the oil-soluble component of the emulsion, a method for calculating the glass transition temperature (Tg) of the acrylic copolymer, a method for measuring the weight average molecular weight (Mw) of the tackifier resin (TF), and a method for tackling. The method for measuring the softening point of the resin (TF) is as follows.

[Average particle size of oil-soluble components of emulsion]
As the average particle diameter of the oil-soluble component of the emulsion, the cumulative volume average diameter when the oil droplet diameter in water was measured by the dynamic light scattering method was measured. The average particle size value (median diameter D50) was determined using a Microtrack UPA particle size distribution meter manufactured by Nikkiso Co., Ltd.

[Glass transition temperature (Tg) of acrylic copolymer]
The Tg of the acrylic copolymer was theoretically calculated by the FOX formula based on the Tg of the homopolymer of each raw material monomer. The Tg of various homopolymers used in the calculation is shown below.
Copolymer of 2-ethylhexyl acrylate (2-EHA): -70 ° C,
Butyl acrylate (BA) homopolymer: -54 ° C,
Homopolymer of methyl methacrylate (MMA): 105 ° C,
Acrylic acid (AA) homopolymer: 106 ° C,
Methacrylic acid (MAA) homopolymer: 130 ° C.

[Weight average molecular weight (Mw) of adhesive-imparting resin (TF)]
The Mw of the tackifier resin (TF) was measured using GPC (gel permeation chromatography). GPC is a liquid chromatography in which a substance dissolved in a solvent is separated and quantified by the difference in its molecular size. Mw was determined by conversion using standard polystyrene. The measurement conditions are as follows.
Device name: Shimadzu, LC-GPC system "Prominence",
Column: Four "GMHXL" manufactured by Tosoh Co., Ltd. and one "HXL-H" manufactured by Tosoh Co., Ltd. are connected in series.
Solvent: tetrahydrofuran (THF),
Flow rate: 1.0 ml / min,
Column temperature: 40 ° C.

[Softening point of adhesive resin (TF)]
The softening point of the tackifier resin (TF) was measured by the ring-and-ball method in accordance with JIS K 2425.

[Production Example 11] (Production of First Acrylic Emulsion (AEL-1))
Chain transfer with 32.0 parts of 2-ethylhexyl acrylate (2-EHA), 64.0 parts of butyl acrylate (BA), 3.1 parts of methyl methacrylate (MMA), and 0.9 parts of acrylic acid (AA). 0.09 part of octyl thioglycolate as an agent, 1.2 parts of Aqualon KH-10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an anionic emulsifier dissolved in 4.8 parts of ion-exchanged water, and ion-exchanged water 13 .5 parts were stirred and mixed to obtain an emulsion. This was placed in a dropping funnel.
31.5 parts of ion-exchanged water was charged into a four-necked flask equipped with a stirrer, a cooling tube, a thermometer, and the above-mentioned dropping funnel, the air inside the flask was replaced with nitrogen gas, and the internal temperature was adjusted to 82 while stirring. The temperature was raised to ° C., and 2.1 parts of a 3% potassium persulfate aqueous solution was added. After 10 minutes, the emulsion was started to be dropped from the dropping funnel, and in parallel with this, 6.3 parts of a 3% potassium persulfate aqueous solution was dropped from another dropping funnel over 5 hours.
While maintaining the internal temperature at 76 ° C., the mixture was aged for 2 hours with further stirring, cooled, neutralized with aqueous ammonia, and the first acrylic copolymer (APL-1) having a solid content of 62%. An emulsion (first acrylic emulsion (AEL-1)) was obtained. The Tg of the first acrylic copolymer (APL-1) was −51.5 ° C. Table 1 shows the monomer composition and Tg of the first acrylic copolymer (APL-1).

[Production Examples 12 and 13] (Production of First Acrylic Emulsion (AEL-2), (AEL-3))
An emulsion of the first acrylic copolymer (APL) having a solid content of 62% (first acrylic emulsion (AEL)) was prepared in the same manner as in Production Example 11 except that the monomer composition was changed. Obtained. Table 1 shows the main raw material compositions and Tg of the first acrylic copolymer (APL). In each production example in Table 1, the conditions not shown in the table were set as common conditions.

[Manufacturing Example 21] (Manufacturing of Adhesive-Applying Resin (TF-1))
(Manufacturing of adhesive resin (TF-1))
<Polymerization reaction process>
1000 parts of gumrosin, 1000 parts of xylene, and 50 parts of zinc chloride as a polymerization catalyst were charged into a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a decompression device, and a polymerization reaction was carried out at 140 ° C. for 7 hours. The xylene solution of the reaction product was washed with warm water, and then 10 parts of concentrated hydrochloric acid and 700 parts of warm water were added for washing. Further, after washing with 500 parts of warm water twice, xylene was distilled off under the conditions of a liquid temperature of less than 200 ° C. and a reduced pressure of 1300 Pa. Further, a decomposition product of gum rosin and an unreacted rosin were distilled off under the conditions of a liquid temperature of 200 to 275 ° C. and a reduced pressure of 400 Pa to obtain a polymerized rosin (R-1).

<Esterification reaction process>
A reaction device equipped with a thermometer, a stirrer, a nitrogen introduction tube, and a decompression device was charged with 500 parts of polymerized rosin (R-1) and 60 parts of pentaerythritol, reacted at 250 ° C. for 2 hours under a nitrogen stream, and further. The esterification reaction was carried out at 270 ° C. for 10 hours to obtain a tackifier resin (TF-1) (polymerized rosin ester). The obtained tackifier resin had a softening point of 158 ° C. and an Mw of 3200. Table 2 shows the raw material composition of the esterification reaction, the softening point of the tackifier resin (TF), and Mw.

[Production Examples 22 to 25] (Production of Adhesive Resins (TF-2) to (TF-5))
Adhesive-imparting resins (TF-2) to (TF-5) (both polymerized rosin esters) were obtained in the same manner as in Production Example 21 except that the raw material composition in the esterification reaction step was changed. Table 2 shows the raw material composition of the esterification reaction, the softening point of the tackifier resin (TF), and Mw. In each production example in Table 2, the conditions not shown in the table were set as common conditions.

[Commercially available adhesive resin (TF)]
The prepared commercially available tackifier resin (TF) is as follows.
(TF-6) Yasuhara Chemical "YS Polystar T-160", terpene resin (terpene phenol resin), softening point 160 ° C,
(TF-7) "FTR-6100" manufactured by Mitsui Chemicals, aromatic hydrocarbon resin (styrene-based / aliphatic monomer copolymer), softening point 95 ° C.
Table 3 shows a list of prepared commercially available tackifying resins (TFs).

[Production Example 31] (Production of a second acrylic emulsion (AEH-1))
40 parts of the tackifier resin (TF-1) was dissolved in a mixture of 98 parts of methyl methacrylate (MMA) and 2 parts of acrylic acid (AA). To this, 14.0 parts of Newcol 707SF (aqueous solution of polyoxyethylene polycyclic phenyl ether sulfate ester salt, active ingredient 30%, manufactured by Nippon Emulsifier Co., Ltd.) and 29.7 parts of ion-exchanged water were added as anionic emulsifiers. The mixture was stirred and mixed to obtain an emulsion. Further, a Cavitron CD1010 type (manufactured by Eurotech Co., Ltd.) using a slit type unit as a rotor / stator is used for forced emulsification to emulsify an oil-soluble component having an average particle diameter (median diameter) of 0.6 μm. I got something. This was placed in a dropping funnel.

22.4 parts of deionized water was placed in a four-necked flask equipped with a stirrer, a cooling tube, a thermometer, and the above-mentioned dropping funnel, the inside of the flask was replaced with nitrogen gas, and the internal temperature was raised to 80 ° C. while stirring. The temperature was raised, and 1.1 parts of a 7.4% ammonium persulfate aqueous solution was added. After 5 minutes, the emulsion was started to be dropped from the dropping funnel, and in parallel with this, 2.7 parts of a 7.4% ammonium persulfate aqueous solution was dropped from another dropping funnel over 3 hours. While maintaining the internal temperature at 80 ° C., the mixture was aged at 76 ° C. for 4 hours with further stirring, cooled, and neutralized with aqueous ammonia to obtain a second acrylic copolymer having a solid content of 60%. An emulsion of APH-1) (second acrylic emulsion (AEH-1)) was obtained. The Tg of the second acrylic copolymer (APH-1) was 105 ° C. The main raw material compositions and Tg of the second acrylic copolymer (APH-1) are shown in Table 4-1.

[Production Examples 32 to 41] (Production of Second Acrylic Emulsions (AEH-2) to (AEH-11))
An emulsion of a second acrylic copolymer (APH) having a solid content of 60% (second acrylic emulsion (AEH)) was obtained by the same method as in Production Example 31 except that the raw material composition was changed. .. The main raw material compositions and Tg of the second acrylic copolymer (APH) are shown in Tables 4-1 and 4-2. In each production example of Table 4-1 and Table 4-2, the conditions not shown in the table were set as common conditions.

(Example 1)
<Manufacturing of water-based pressure-sensitive adhesive>
The first acrylic emulsion so that the mass ratio of the first acrylic copolymer (APL-1) to the second acrylic copolymer (APH-1) is 90.6: 9.4. (AEL-1) and the second acrylic emulsion (AEH-1) were stirred and mixed. Ammonia water was added to this mixture to adjust the pH to 8.5. A defoaming agent, a leveling agent, and a preservative are added to this, and a viscosity adjusting agent is further added to adjust the viscosity to 4000 mPa · s (BL type viscometer, using # 4 rotor, measured under the condition of 60 rpm). , A water-based pressure-sensitive adhesive was obtained.

<Making a pressure-sensitive adhesive sheet>
Using a comma coater, the obtained water-based pressure-sensitive adhesive was applied onto a release paper so that the mass of the film after drying was 16 g / m ^2, and dried in a drying oven at 105 ° C. for 60 seconds. , High-quality paper (60 g / m ² ) was laminated on this, and the obtained pressure-sensitive adhesive sheet was wound up. A pressure-sensitive adhesive sheet having a width of 25 mm and a length of 100 mm was prepared and used for the evaluation described later. The length direction of the pressure-sensitive adhesive sheet was adjusted to the flow direction of the sheet at the time of manufacture.
Table 5-1 shows the main composition of the water-based pressure-sensitive adhesive and the evaluation results of the pressure-sensitive adhesive sheet. In Table 5-1 and Table 5-2, Table 6-1 and Table 6-2, the conditions not described are common conditions.

(Examples 2 to 12, Comparative Example 1, Comparative Examples 5 to 8)
In each of Examples 2 to 12, Comparative Example 1 and Comparative Examples 5 to 8, the first acrylic as shown in Table 5-1, Table 5-2, Table 6-1 and Table 6-2. A water-based pressure-sensitive adhesive and a pressure-sensitive adhesive sheet were prepared and evaluated in the same manner as in Example 1 except that the types and compounding ratios of the system emulsion (APL) and the second acrylic emulsion (APH) were changed. .. The main composition and evaluation results are shown in Tables 5-1 and 5-2, Table 6-1 and Table 6-2.

(Comparative Examples 2 to 4)
In Comparative Example 2, instead of the first acrylic emulsion (AEL-1) and the second acrylic emulsion (AEH-1), the first acrylic emulsion (AEL-1) and the following commercially available adhesive are imparted. An aqueous pressure-sensitive adhesive and a pressure-sensitive adhesive sheet were prepared and evaluated in the same manner as in Example 1 except that the aqueous dispersion of the resin was used in the compounding ratio shown in Table 6-1.
In Comparative Examples 3 and 4, instead of the first acrylic emulsion (AEL-1) and the second acrylic emulsion (AEH-1), the first acrylic emulsion (AEL-1) and the tackifier resin (AEL-1) were used. The same as in Example 1 except that the second acrylic emulsion (AEH-9) containing no TF) and the aqueous dispersion of the following tackifying resin on the market were used in the blending ratios shown in Table 6-1. A water-based pressure-sensitive adhesive and a pressure-sensitive adhesive sheet were prepared and evaluated.
Table 6-1 shows the main composition and evaluation results.

<Water dispersion of adhesive resin>
(E-865) "Super Ester E-865" manufactured by Arakawa Chemical Co., Ltd. (aqueous dispersion of polymerized rosin ester, solid content 50%, softening point 160 ° C.).
In the table, the "blending amount of the aqueous dispersion of the tackifier resin" is the blending amount of the tackifier resin with respect to 100 parts of the total amount of the first acrylic emulsion (AEL) and the second acrylic emulsion (AEH).

[Evaluation items and evaluation methods]
(Room temperature adhesive strength to polyethylene plate)
In a 23 ° C. and 50% RH environment, the release paper is peeled off from the pressure-sensitive adhesive sheet, the exposed pressure-sensitive adhesive layer is attached on a polyethylene plate, and a roll having a mass of 2 kg is reciprocated once on the pressure-sensitive adhesive sheet. And crimped. Immediately after that, the adhesive strength was measured. This adhesive force was defined as "normal temperature adhesive force". The adhesive strength was measured in accordance with JIS Z-0237 under the conditions of peeling speed: 300 mm / min and peeling angle of 180 °. The evaluation criteria are as follows.
Room temperature adhesive strength is 10N / 25mm or more. Excellent.
Room temperature adhesive strength is 8N / 25mm or more and less than 10N / 25mm. Good.
Room temperature adhesive strength is 6N / 25mm or more and less than 8N / 25mm. Practical use is possible.
Room temperature adhesive strength is less than 6N / 25mm. Not practical.

(Curved surface stickability to polyethylene round bar)
A test piece having a width of 20 mm and a length of 15 mm was cut out from a pressure-sensitive adhesive sheet having a width of 25 mm and a length of 100 mm. The length direction of the test piece was adjusted to the flow direction of the sheet at the time of manufacture. The release paper was peeled off from this test piece, and the exposed pressure-sensitive adhesive layer was attached around a polyethylene round bar having a length of 30 cm and a diameter of 10 mm, and strongly pressure-bonded with a finger. At this time, the width direction (longitudinal direction) of the test piece and the length direction of the polyethylene rod were aligned. After leaving the sample in an atmosphere of 23 ° C. for 7 days, the presence or absence of peeling of the test piece was visually observed. The evaluation criteria are as follows.
⊚: No peeling of test piece. Excellent.
〇: Both ends of the test piece are peeled off by less than 2 mm from the ends. Good.
Δ: At least one end of the test piece is peeled from the end by 2 mm or more and less than 5 mm. Practical use is possible.
X: At least one end of the test piece is peeled off by 5 mm or more from the end. Not practical.

(High temperature holding power)
After peeling the release paper from the pressure-sensitive adhesive sheet, the exposed pressure-sensitive adhesive layer was attached on a stainless plate (SUS304) as a test plate. At this time, the sticking area was set to 25 mm × 25 mm. According to the method for measuring the holding force of JIS Z 0237, a load of 1 kg was applied to the test piece under the condition of 80 ° C. and 50% RH, and the amount of misalignment (mm) of the test piece after 24 hours was measured. When the test piece fell, the time (seconds) until it completely fell was measured. The evaluation criteria are as follows. The table shows the amount of misalignment of the test piece or the time (seconds) until the test piece falls.
The amount of misalignment of the test piece is less than 1.0 mm. Excellent.
The amount of misalignment of the test piece is 1.0 mm or more and less than 5.0 mm. Good.
The amount of misalignment of the test piece is 5.0 mm or more and less than 25.0 mm. Practical use is possible.
The amount of misalignment of the test piece is 25.0 mm or more, and the test piece falls. Not practical.

(Low temperature adhesive force to polyethylene plate)
The pressure-sensitive adhesive sheet and the polyethylene plate as an adherend were left in an environment of −10 ° C. for 24 hours. Then, under the same temperature conditions, the release paper is peeled off from the pressure-sensitive adhesive sheet, the exposed pressure-sensitive adhesive layer is attached on the polyethylene plate, and a roll having a mass of 2 kg is reciprocated once on the pressure-sensitive adhesive sheet. , Crimped. Immediately after that, the adhesive strength was measured. This adhesive force is defined as "low temperature adhesive force". The adhesive strength was measured in accordance with JIS Z-0237 under the conditions of peeling speed: 300 mm / min and peeling angle of 180 °. The evaluation criteria are as follows.
Low temperature adhesive strength is 5N / 25mm or more. Excellent.
Low temperature adhesive strength is 4N / 25mm or more and less than 5N / 25mm. Good.
Low temperature adhesive strength is 2N / 25mm or more and less than 4N / 25mm. Practical use is possible.
Low temperature adhesive strength is less than 2N / 25mm, not practical.

(Haze value)
Using a comma coater, the obtained water-based pressure-sensitive adhesive was applied onto a 50 μm-thick polyethylene terephthalate (PET) film so that the weight of the film after drying was 25 g / m ^2, and dried at 105 ° C. It was dried in an oven for 60 seconds to form a pressure-sensitive adhesive layer. The haze value of the obtained laminate was measured using a HAZE meter. The evaluation criteria are as follows.
The haze value is 6.0 or more and 10.0 or less, and phase separation is remarkably observed in the pressure-sensitive adhesive layer.
The haze value is 5.0 or more and less than 6.0, and phase separation is observed in the pressure-sensitive adhesive layer.
The haze value is less than 5.0, and phase separation is not clearly seen in the pressure-sensitive adhesive layer.

[Summary of results]
In Examples 1-12,
A first acrylic emulsion (AEL) containing a first acrylic copolymer (APL) having a Tg of −70 to −40 ° C.
A second acrylic emulsion (AEH) containing a second acrylic copolymer (APH) having a Tg of 60 to 120 ° C. and a tackifier resin (TF) which is a rosin resin having a softening point of 130 ° C. or higher. And were blended to produce a water-based pressure-sensitive adhesive.
In Examples 1 to 12, a pressure-sensitive adhesive sheet was produced using the obtained water-based pressure-sensitive adhesive.

All of the pressure-sensitive adhesive sheets obtained in Examples 1 to 12 had good room temperature adhesive strength, curved surface adhesiveness, high temperature holding power, and low temperature adhesive strength. It was confirmed that all of the pressure-sensitive adhesive sheets obtained in these examples had good adhesive strength even for an adherend having a curved surface shape and a polyolefin adherend which was difficult to adhere. It was confirmed that all of the pressure-sensitive adhesive sheets obtained in these examples had good adhesive strength with respect to the polyolefin adherend, which is difficult to adhere, even at a low temperature of −10 ° C.
In the water-based pressure-sensitive adhesives of Examples 1 to 12, the tackifier resin (adhesive-imparting resin) was applied to 100 parts by mass of the total amount of the first acrylic copolymer (APL) and the second acrylic copolymer (APH). The content of TF) was 1.0 part by mass or more and less than 5.5 parts by mass. Good results were obtained even with a small amount of tackifier resin (TF).

In each of Examples 1 to 12, the haze value of the laminate obtained by applying and drying a water-based pressure-sensitive adhesive on a PET film having a thickness of 50 μm under ^{the condition of a dry mass of 25 g / m 2 is 5.0 to 5.} It was 10.0, and the phase-separated state of the pressure-sensitive adhesive layer was good. When the scanning probe microscope observation was carried out, the second acrylic phase (sea phase) containing the first acrylic copolymer (APL) having a low Tg and being relatively soft had a high Tg and was relatively hard. It was confirmed that a plurality of phase-separated domains (island phases) containing the acrylic copolymer (APH) and the tackifier resin (TF) were formed. As a representative, a scanning probe micrograph of the pressure-sensitive adhesive layer of Example 1 is shown in FIG.

The pressure-sensitive adhesive sheet obtained in Comparative Example 1 in which no tack-imparting resin was used had poor room temperature adhesive strength, curved surface adhesiveness, and low temperature adhesive strength.

The pressure-sensitive adhesive sheet obtained in Comparative Example 2 in which the first acrylic emulsion (AEL) and the aqueous dispersion of the tackifier resin were blended without using the second acrylic emulsion (AEH) was bonded at room temperature. The force and high temperature holding power were poor.
In Comparative Example 2, the haze value of the laminate obtained by applying and drying the water-based pressure-sensitive adhesive on a PET film having a thickness of 50 μm under ^{the condition of a dry mass of 25 g / m 2 was less than 5.0, and scanning was performed.} A type probe microscope observation was carried out, but the phase separation of the pressure-sensitive adhesive layer was not clearly observed. A scanning probe micrograph of the pressure-sensitive adhesive layer of Comparative Example 2 is shown in FIG.

The pressure-sensitive adhesive sheet obtained in Comparative Example 3 in which the first acrylic emulsion (AEL), the second acrylic emulsion (AEH) containing no tackifier resin, and the aqueous dispersion of the tackifier resin were blended. The normal temperature adhesive strength was poor.
In Comparative Example 3, the haze value of the laminate obtained by applying and drying the water-based pressure-sensitive adhesive on a PET film having a thickness of 50 μm under ^{the condition of a dry mass of 25 g / m 2 was less than 5.0, and scanning was performed.} A type probe microscope observation was carried out, but phase separation of the pressure-sensitive adhesive layer was not clearly observed (similar to Comparative Example 2).

In Comparative Example 4, the normal temperature adhesive strength and the curved surface adhesiveness could be improved by increasing the amount of the water dispersion of the tackifier resin added as compared with Comparative Example 3, but the high temperature holding power and the low temperature adhesive strength were poor. became.

The pressure-sensitive adhesive sheet obtained in Comparative Example 5 using the second acrylic copolymer (APH) having a Tg of less than 60 ° C. had poor curved surface stickability and high-temperature holding power.
In Comparative Example 5, the haze value of the laminate obtained by applying and drying the water-based pressure-sensitive adhesive on a PET film having a thickness of 50 μm under ^{the condition of a dry mass of 25 g / m 2 was less than 5.0, and scanning was performed.} A type probe microscope observation was carried out, but phase separation of the pressure-sensitive adhesive layer was not clearly observed (similar to Comparative Example 2).

In Comparative Example 6 using the second acrylic emulsion (AEH) containing the tackifier resin (TF) having a softening point of less than 130 ° C., the adhesive force to the polyolefin adherend was poor.

The pressure-sensitive adhesive sheets obtained in Comparative Examples 7 and 8 using the second acrylic emulsion (AEH) containing a non-rosin-based tackifier resin (TF) had poor curved surface stickability.

The present invention is not limited to the above-described embodiments and examples, and the design can be appropriately changed as long as the gist of the present invention is not deviated.

Claims (9)

A first acrylic emulsion (AEL) containing a first acrylic copolymer (APL) having a relatively low glass transition temperature, and
A water-based pressure-sensitive adhesive containing a second acrylic copolymer (APH) having a relatively high glass transition temperature and a second acrylic emulsion (AEH) containing a tackifier resin.
The glass transition temperature of the first acrylic copolymer (APL) is −70 to −40 ° C.
The glass transition temperature of the second acrylic copolymer (APH) is 60 to 120 ° C.
The tackifier resin is a water-based pressure-sensitive adhesive which is a rosin-based resin having a softening point of 130 ° C. or higher. The content of the first acrylic copolymer (APL) is 80 to 80 to 100 parts by mass of the total amount of the first acrylic copolymer (APL) and the second acrylic copolymer (APH). The water-based pressure-sensitive adhesive according to claim 1, wherein the content is 95 parts by mass and the content of the second acrylic copolymer (APH) is 20 to 5 parts by mass. The content of the tackifier resin is 1.0 part by mass or more and 5.5 parts by mass with respect to 100 parts by mass of the total amount of the first acrylic copolymer (APL) and the second acrylic copolymer (APH). The water-based pressure-sensitive adhesive according to claim 1 or 2, which is less than parts by mass. Claimed that the haze value of the laminate obtained by applying and drying the water-based pressure-sensitive adhesive on a 50 μm-thick polyethylene terephthalate film under ^{the condition of a dry mass of 25 g / m 2 is 5.0 to 10.0.} Item 3. The water-based pressure-sensitive adhesive according to any one of Items 1 to 3. The water-based pressure-sensitive adhesive according to any one of claims 1 to 4, which comprises a phase-separated domain containing a second acrylic copolymer (APH) and the tackifier resin. The second acrylic emulsion (APH) contains a plurality of ethylenically unsaturated monomers, the tackifier resin, a surfactant, and water, and the average particle size of the oil-soluble component is 0.3 to 2.0 μm. The aqueous pressure-sensitive adhesive according to any one of claims 1 to 5, which is an emulsion polymer of an emulsion. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of a dried product of the water-based pressure-sensitive adhesive according to any one of claims 1 to 6. A first acrylic emulsion (AEL) containing a first acrylic copolymer (APL) having a relatively low glass transition temperature, and
A method for producing an aqueous pressure-sensitive adhesive containing a second acrylic copolymer (APH) having a relatively high glass transition temperature and a second acrylic emulsion (AEH) containing a tackifier resin.
A first acrylic emulsion (AEL) containing a first acrylic copolymer (APL) having a glass transition temperature of −70 to −40 ° C. by emulsion polymerization of a plurality of types of ethylenically unsaturated monomers. (1) and
In the presence of an emulsifier and a tackifier resin which is a rosin-based resin having a softening point of 130 ° C. or higher, a plurality of types of ethylenically unsaturated monomers are emulsion-polymerized and the glass transition temperature is 60 to 120 ° C. The step (2) of producing a second acrylic emulsion (AEH) containing the second acrylic copolymer (APH), and
A method for producing a water-based pressure-sensitive adhesive, which comprises a step (3) of mixing a first acrylic emulsion (AEL) and a second acrylic emulsion (AEH). Step (2) is
In the step (2-a) of dissolving the tackifier resin in the plurality of types of ethylenically unsaturated monomers,
The mixed solution obtained in step (2-a) is forcibly emulsified in the presence of an emulsifier and water to obtain an emulsion having an average particle size of an oil-soluble component of 0.3 to 2.0 μm (2). −B) and
The step (2-c) of emulsion polymerization of the emulsion is included.
The method for producing a water-based pressure-sensitive adhesive according to claim 8.

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