JP2014095052A - Water dispersion type adhesive composition, manufacturing method of repeelable adhesive sheet, and repeelable adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water dispersion type adhesive composition having excellent adhesive force, capable of suppressing increase of the adhesive force with time, capable of manufacturing a repeelable adhesive sheet having excellent repeelability, and capable of corresponding to high speed application, and to provide a manufacturing method of the repeelable adhesive sheet and the repeelable adhesive sheet.SOLUTION: A water dispersion type adhesive composition contains an emulsion of a (meth)acrylic acid ester copolymer containing the specified quantity of a constitutional unit derived from (meth)acrylic acid alkylester having an alkyl group having 4 to 12 carbon atoms and a constitutional unit derived from a carboxyl group-containing unsaturated monomer [A], an emulsion of a (meth)acrylic acid ester copolymer containing the specified quantity of a constitutional unit derived from (meth)acrylic acid alkylester having an alkyl group having 8 to 18 carbon atoms and the constitutional unit derived from the carboxyl group-containing unsaturated monomer [B] and a crosslinking agent [C], and has a gel fraction of 63 to 95 mass% when an adhesive agent layer formed from the composition is dissolved in THF.

Description

  The present invention relates to a water-dispersed pressure-sensitive adhesive composition, a method for producing a releasable pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition, and a re-peelable pressure-sensitive adhesive sheet obtained by the production method.

Conventionally, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer such as a pressure-sensitive adhesive label, a masking tape or sheet, and a surface protective film is often peeled off from the adherend after a certain period of time has elapsed after being attached to the adherend. At this time, part of the pressure-sensitive adhesive layer often remains on the adherend. Further, when the adherend is paper, the adherend or the base material of the adhesive sheet is often torn. In particular, when the adherend is coated paper such as art paper or cast coated paper, the surface of the coated paper is smooth, so the adhesive layer adheres to the coated paper surface and destroys the surface layer of the coated paper. It often happens.
A cross-linking agent is added as a pressure-sensitive adhesive to form a pressure-sensitive adhesive layer so that the pressure-sensitive adhesive sheet can be easily peeled off from the adherend without causing the above-mentioned problems. Many re-peelable pressure-sensitive adhesives have been proposed. In particular, re-peeling pressure-sensitive adhesives have been widely studied from the viewpoint of environmental hygiene in recent years and are strongly oriented toward water-based pressure-sensitive adhesives that do not use a solvent.

  For example, Patent Document 1 discloses an aqueous pressure-sensitive adhesive in which a polyglycidyl compound is blended with an aqueous copolymer emulsion having a specific monomer composition, molecular weight, glass transition temperature, and particle size.

  Patent Document 2 discloses an acrylic emulsion-type pressure-sensitive adhesive in which one or more crosslinking agents selected from a polyfunctional aziridine compound and a polyfunctional carbodiimide compound are added to a specific acrylic emulsion-type pressure-sensitive adhesive.

In Patent Document 3, a specific amount of a water-soluble crosslinking agent containing an oxazoline group is blended with a specific acrylic emulsion-type pressure-sensitive adhesive, the solvent-soluble content is 40% by mass or less, and the elastic modulus is 2 to 2. A re-peeling type pressure sensitive adhesive having a re-peeling force of 500 g / 20 mm or less at 50 kg / cm ² is disclosed.

  In Patent Document 4, a specific acrylic emulsion-type pressure-sensitive adhesive has a carbodiimide group-containing crosslinking agent, and the ratio of the carbodiimide group to the carboxyl group contained in the acrylic emulsion-type pressure-sensitive adhesive (carbodiimide group / carboxyl group). A water-dispersible pressure-sensitive adhesive for re-peeling having a re-peelability of 500 g / 20 mm width or less is disclosed.

  Patent Document 5 discloses a pressure-sensitive adhesive containing (meth) acrylic acid alkyl ester as a main component, acrylic acid and methacrylic acid as functional monomers, and further blended with a water-soluble crosslinking agent and an oil-soluble crosslinking agent. .

  Patent Document 6 contains (meth) acrylic acid alkyl ester units having 4 to 12 carbon atoms in the alkyl group as main components and 0.1 to 2.0% by mass of carboxyl group-containing unsaturated monomer units ( Emulsion [A] of a meth) acrylic acid ester copolymer, an emulsion [B] of an alkali-soluble or alkali-swellable (meth) acrylic acid copolymer containing a carboxyl group-containing unsaturated monomer unit, and a crosslinking agent [C] A re-peelable pressure-sensitive adhesive sheet using a water-dispersed pressure-sensitive adhesive composition containing as an essential component has been proposed.

Japanese Patent Publication No.5-075034 JP 7-278233 A Japanese Patent Laid-Open No. 10-114887 JP 2001-131512 A JP 2001-152118 A JP 2009-073920 A

  By the way, in recent years, the releasable pressure-sensitive adhesive sheet not only has high adhesive strength when affixed to an adherend, but also suppresses an increase in adhesive strength even after a long time, and can be easily peeled off. There is also a need for removability.

In consideration of the productivity of the pressure-sensitive adhesive sheet, a pressure-sensitive adhesive composition capable of high-speed coating at a coating speed of 150 m / min or more is required. However, the general acrylic emulsion-type pressure-sensitive adhesive composition increases the shear stress applied to the pressure-sensitive adhesive when the coating speed on the substrate is increased. Therefore, in order to enable high-speed application, it is necessary to reduce the viscosity of the pressure-sensitive adhesive composition. However, when it is applied onto a substrate at high speed using a coating solution with reduced viscosity, streaks, repellency, or squeeze are generated. There is a problem that the surface state of the formed coating film becomes poor.
Further, even in an acrylic emulsion-type pressure-sensitive adhesive composition that can be applied at high speed, if an adhesive sheet using the pressure-sensitive adhesive composition is attached to an adherend and then peeled off, the adhesive composition is applied to the adherend. When the part adheres or the adherend may be contaminated, there is a problem that the adhesive strength increases with time and the removability decreases.

The pressure-sensitive adhesive composition and the pressure-sensitive adhesive sheet disclosed in Patent Documents 1 to 6 did not satisfy all the required performances described above.
The present invention has excellent adhesive strength, can suppress an increase in adhesive strength over time, can produce a removable adhesive sheet having excellent removability, and has a surface state even when applied at high speed. To provide a water-dispersed pressure-sensitive adhesive composition capable of forming a good coating film, a method for producing a releasable pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition, and a releasable pressure-sensitive adhesive sheet obtained by the production method With the goal.

  The present inventors are a pressure-sensitive adhesive composition comprising an emulsion of two (meth) acrylic acid ester copolymers containing a predetermined amount of a structural unit derived from a carboxykyl-containing unsaturated monomer, and a crosslinking agent, The water-dispersed pressure-sensitive adhesive composition having a gel fraction of 63 to 95% by mass when the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is dissolved in tetrahydrofuran (THF) can solve the above problems. The present invention was completed.

That is, the present invention provides the following [1] to [9].
[1] Containing a structural unit (a1) derived from a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms as a main component and 0.1 structural unit (a2) derived from a carboxyl group-containing unsaturated monomer Main component of (meth) acrylic acid ester copolymer emulsion [A] containing ~ 2.0% by mass, and (meth) acrylic acid alkyl ester-derived structural unit (b1) having an alkyl group having 8 to 18 carbon atoms And a (meth) acrylate copolymer emulsion [B] containing 25 to 50% by mass of a structural unit (b2) derived from a carboxyl group-containing unsaturated monomer, and a water-dispersed adhesive containing a crosslinking agent [C] The gel fraction when the pressure-sensitive adhesive layer formed from the water-dispersed pressure-sensitive adhesive composition is dissolved in tetrahydrofuran is 63 to 95% by mass There, water-dispersed PSA composition.
[2] The water-dispersed pressure-sensitive adhesive composition according to [1], wherein the water-dispersed pressure-sensitive adhesive composition has a viscosity at 25 ° C. of 500 mPa · s or less.
[3] The water-dispersed pressure-sensitive adhesive composition according to the above [1] or [2], wherein the emulsion [A] and [B] have an average particle size of 100 to 900 nm.
[4] The above (1) to [3], wherein the (meth) acrylic acid alkyl ester having an alkyl group having 8 to 18 carbon atoms constituting the structural unit (b1) is 2-ethylhexyl (meth) acrylate. The water-dispersed pressure-sensitive adhesive composition according to any one of the above.
[5] The water dispersion according to any one of the above [1] to [4], wherein the emulsion [B] of the (meth) acrylic acid ester copolymer further contains a structural unit (b3) derived from a polyfunctional monomer. Type pressure-sensitive adhesive composition.
[6] The crosslinker [C] is a polyglycidyl compound having two or more glycidyl groups in the molecule, an oxazoline-based compound having two or more oxazoline groups in the molecule, and two or more carbodiimide groups in the molecule. The water-dispersed pressure-sensitive adhesive composition according to any one of the above [1] to [5], which is one or more selected from the group consisting of carbodiimide-based compounds.
[7] The weight average molecular weight (Mw) of the tetrahydrofuran-soluble component of the pressure-sensitive adhesive layer formed from the water-dispersed pressure-sensitive adhesive composition is 20,000 to 250,000, and the molecular weight distribution (Mw / Mn) (Mn Is a water-dispersed pressure-sensitive adhesive composition according to any one of the above [1] to [6], wherein the number average molecular weight is 2.0 to 5.0.
[8] The water-dispersed pressure-sensitive adhesive composition according to any one of the above [1] to [7] is applied at a coating speed of 150 m / min or more to form a coating film, and the coating film is dried. The manufacturing method of a releasable adhesive sheet including the process of forming an agent layer.
[9] A releasable pressure-sensitive adhesive sheet obtained by the method for producing a releasable pressure-sensitive adhesive sheet according to [8].

  The water-dispersible pressure-sensitive adhesive composition of the present invention can form a coating film having a good surface state even when applied at high speed, and the releasable pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition has excellent adhesive strength. And can suppress an increase in adhesive strength over time and has excellent removability.

It is sectional drawing of this adhesive sheet which shows an example of a structure of the releasable adhesive sheet of this invention.

  In the following description, for example, “(meth) acrylic acid” is used as a term indicating both “acrylic acid” and “methacrylic acid”, and the same applies to other similar terms.

(Water-dispersed pressure-sensitive adhesive composition)
The water-dispersed pressure-sensitive adhesive composition of the present invention (hereinafter also simply referred to as “pressure-sensitive adhesive composition”) is an emulsion of a (meth) acrylate copolymer (hereinafter also referred to as “copolymer (A)”). [A], (meth) acrylic acid ester copolymer (hereinafter also referred to as “copolymer (B)”) emulsion [B], and cross-linking agent [C].
Moreover, the water dispersion-type adhesive composition of this invention may contain other additives other than said [A]-[C] component as needed.

The content (solid content ratio) of the [B] component in the pressure-sensitive adhesive composition is preferably 0.6 to 20 parts by mass, more preferably 0.7 to 100 parts by mass of the solid content of the [A] component. -15 mass parts, More preferably, it is 0.8-10 mass parts, More preferably, it is 0.9-5 mass parts.
If the content of the component [B] is 0.6 parts by mass or more, it becomes easy to adjust the gel fraction of the obtained pressure-sensitive adhesive layer to a predetermined value or more, and removability using the pressure-sensitive adhesive composition. An increase in adhesive strength with time of the pressure-sensitive adhesive sheet can be suppressed and re-peelability can be improved. Moreover, if content of [B] component is 20 mass% or less, the coating liquid containing the adhesive composition of this invention which has moderate viscosity, without the carboxyl group in an adhesive composition becoming excessive. Can be obtained.

  The content (solid content ratio) of the [C] component in the pressure-sensitive adhesive composition is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 100 parts by mass of the solid content of the [A] component. -6 mass parts, More preferably, it is 0.2-3 mass parts.

<Emulsion of (meth) acrylic ester copolymer [A]>
The component [A] is an emulsion of a (meth) acrylic acid ester copolymer (copolymer (A)).
The copolymer (A) contains a structural unit (a1) derived from a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms (hereinafter also referred to as “monomer (a1)”) as a main component. And 0.1 to 2.0% by mass of a structural unit (a2) derived from a carboxyl group-containing unsaturated monomer (hereinafter also referred to as “monomer (a2)”).
The copolymer (A) is a structural unit derived from the polyfunctional monomer (a3) (a3) as necessary, in addition to the structural units (a1) and (a2), as long as the effects of the present invention are not impaired. ), A structural unit (a4) derived from an unsaturated monomer (a4) other than the monomers (a1) and (a2), or a structural unit derived from a monomer other than these.

  The emulsion [A] of the copolymer (A) is obtained by mixing the monomers (a1) and (a2), the monomers (a3) and (a4) used as necessary, and other monomers. It is obtained by emulsion polymerization of a monomer mixture.

[Structural unit (a1)]
The structural unit (a1) in the copolymer (A) is a main component in the copolymer (A) from the viewpoint of improving the initial adhesive strength, and the content of the structural unit (a1) It is the most abundant component among all the structural units contained in A).
The content of the structural unit (a1) in the copolymer (A) is preferably 50 to 99.9% by mass, more preferably 65 to 99.6% by mass, still more preferably 75 to 99.3% by mass, More preferably, it is 85-99.0 mass%. If content of a structural unit (a1) is 50 mass% or more, initial stage adhesive force can be made favorable. Moreover, if the said content is 99.9 mass% or less, content of the structural unit (a2) derived from a monomer (a2) can be ensured, cohesion force is improved, and re-peelability with time is improved. Can be good.

The monomer (a1) constituting the structural unit (a1) is a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms.
When the alkyl group has less than 4 carbon atoms or more than 12 carbon atoms, the homopolymer has a high glass transition temperature, and the resulting (meth) acrylic acid ester copolymer has a poor tack. Absent.
Although the carbon number of the alkyl group is 4 to 12, from the above viewpoint, it is preferably 5 to 10, more preferably 6 to 9, and further preferably 6 to 8.

Examples of the monomer (a1) include butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, and nonyl (meth). ) Acrylate, decyl (meth) acrylate, and the like.
These monomers (a1) may be used alone or in combination of two or more.
Among these, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate are preferable from the viewpoint of improving initial adhesive strength, and butyl (meth) ) Acrylate or 2-ethylhexyl (meth) acrylate is more preferable, and 2-ethylhexyl (meth) acrylate is still more preferable.

[Structural unit (a2)]
The copolymer (A) used in the present invention contains the structural unit (a2) derived from the carboxyl group-containing unsaturated monomer (a2), thereby improving the cohesive force due to the crosslinking reaction with the crosslinking agent [C] described later. , Removability can be improved.

The content of the structural unit (a2) in the copolymer (A) is 0 from the viewpoint of improving the stability over time of the obtained releasable pressure-sensitive adhesive sheet and from the viewpoint of improving the balance between removability and adhesive strength. 0.1 to 2.0% by mass, preferably 0.3 to 1.7% by mass, more preferably 0.5 to 1.5% by mass, and still more preferably 0.7 to 1.2% by mass. .
When the content of the structural unit (a2) is less than 0.1% by mass, the crosslinking agent [C] and the crosslinking bond are not sufficiently formed, and it is difficult to improve the cohesive force. As a result, the re-peelability decreases. Moreover, when the said content exceeds 2 mass%, the viscosity of the adhesive composition obtained will become high and it will become difficult to respond | correspond to high-speed application | coating.

The monomer (a2) is a monomer having a carboxyl group in one molecule and having a carbon-carbon unsaturated bond, and examples thereof include ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid; Examples thereof include ethylenically unsaturated dicarboxylic acids such as acid, itaconic acid, maleic acid and citraconic acid; 2-carboxylethyl (meth) acrylate and the like.
These monomers (a2) can be used alone or in combination of two or more.
Among these, from the viewpoint of versatility, ethylenically unsaturated monocarboxylic acid is preferable, (meth) acrylic acid is more preferable, and when the fact that the carboxyl group plays a role as a cross-linking point is the cross-linking point. Acrylic acid is more preferable from the viewpoint that the carboxyl group is easily oriented in the emulsion particle surface layer.

[Structural unit (a3)]
The copolymer (A) may further contain a structural unit (a3) derived from the polyfunctional monomer (a3) as an internal crosslinking agent for the purpose of improving the cohesive strength of the pressure-sensitive adhesive composition. .
Examples of the monomer (a3) include (poly) ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, methylenebisacrylamide, and divinylbenzene. It is done.
These monomers (a3) may be used alone or in combination of two or more.

  Content of a structural unit (a3) in a copolymer (A) becomes like this. Preferably it is 0-2 mass%, More preferably, it is 0-1.5 mass%. If content of a structural unit (a3) is 2 mass% or less, the phenomenon in which adhesiveness with a base material and removability will fall can be prevented.

[Structural unit (a4)]
The copolymer (A) may be copolymerized with the monomer (a1) and may contain a structural unit (a4) derived from an unsaturated monomer (a4) other than the monomers (a1) and (a2). Good.

  As unsaturated monomer (a4) other than monomer (a1), for example, (meth) acryl having an alkyl group having 1 to 3 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, etc. Acid alkyl ester; (meth) acrylic acid alkyl ester having an alkyl group having 13 to 18 carbon atoms such as tridecyl (meth) acrylate and stearyl (meth) acrylate.

  Examples of the unsaturated monomer (a4) other than the monomer (a2) include hydroxyl group-containing monomers such as hydroxyalkyl (meth) acrylate and glycerin di (meth) acrylate; (meth) acrylamide, N, N-dimethyl (meta) ) Amide group-containing monomers such as acrylamide; Epoxy group-containing monomers such as glycidyl (meth) acrylate; Cyano group-containing monomers such as (meth) acrylonitrile; Imide group-containing monomers such as cyclohexylmaleimide and isopropylmaleimide; (Meth) acryloylmorpholine, Monomers having a nitrogen atom-containing ring such as N-vinylpyrrolidone; vinyl group-containing monomers such as vinyl acetate and styrene; dimethyl maleate, di-n-butyl maleate, di-2-ethylhexyl maleate, di-n maleate − Corruptible, dimethyl fumarate, di -n- butyl fumarate, di-2-ethylhexyl, maleic acid or fumaric acid esters such as fumarate -n- octyl.

  The content of the structural unit (a4) in the copolymer (A) is preferably 40% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, and still more preferably 1% by mass or less. is there. If content of a structural unit (a4) is 40 mass% or less, the phenomenon in which adhesiveness with a base material falls can be prevented.

<Emulsion of (meth) acrylate copolymer [B]>
The component [B] is an emulsion of a (meth) acrylic acid ester copolymer (copolymer (B)).
The copolymer (B) contains a structural unit (b1) derived from a (meth) acrylic acid alkyl ester having an alkyl group having 8 to 18 carbon atoms (hereinafter also referred to as “monomer (b1)”) as a main component. The structural unit (b2) derived from a carboxyl group-containing unsaturated monomer (hereinafter also referred to as “monomer (b2)”) is contained in an amount of 25 to 50% by mass.
The copolymer (B) is an unsaturated monomer other than the monomers (b1) and (b2) as necessary, in addition to the structural units (b1) and (b2), as long as the effects of the present invention are not impaired. The structural unit (b3) derived from (b3), the structural unit (b4) derived from the polyfunctional monomer (b4) may be included, or the structural unit derived from a monomer other than these may be included.

As for the emulsion [B] of the copolymer (B), as in the case of the component [A], the monomers (b1) and (b2), the monomers (b3) and (b4) used as necessary, and others It is obtained by emulsion polymerization of a monomer mixture obtained by mixing these monomers.
The copolymer (B) is preferably an alkali non-swellable (non-soluble) copolymer that does not swell or dissolve in the presence of an alkali from the viewpoint of preventing a significant increase in viscosity of the pressure-sensitive adhesive composition. .

[Structural unit (b1)]
The structural unit (b1) in the copolymer (B) serves as a main component in the copolymer (B) from the viewpoint of making it an alkali non-swellable (non-soluble) copolymer, and the structural unit (b1). It is necessary to increase the content of at most among all the structural units contained in the copolymer (B).
Content of the structural unit (b1) in a copolymer (B) becomes like this. Preferably it is 50-75 mass%, More preferably, it is 53-72 mass%, More preferably, it is 56-70 mass%, More preferably, it is 60- 67% by mass. If the content of the structural unit (b1) is 50% by mass or more, the resulting copolymer can be made alkali non-swellable (non-soluble), which is preferable. Moreover, if the said content is 75 mass% or less, content of the structural unit (b2) derived from a monomer (b2) can be ensured, the raise of the adhesive force with time of an adhesive composition will be suppressed, and it will re- Peelability can be improved.

The monomer (b1) constituting the structural unit (b1) has an alkyl group having 8 to 18 carbon atoms from the viewpoint of obtaining a pressure-sensitive adhesive composition that can suppress an increase in the viscosity of the pressure-sensitive adhesive composition and can be applied to high-speed application. It is a (meth) acrylic acid alkyl ester.
Although the carbon number of the alkyl group is 8 to 18, from the above viewpoint, it is preferably 8 to 14, more preferably 8 to 12, and still more preferably 8 to 10.

Examples of the monomer (b1) include 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and the like. .
These monomers (b1) may be used alone or in combination of two or more.
Among these, the viscosity of the pressure-sensitive adhesive composition is in an appropriate range, the viewpoint of obtaining a pressure-sensitive adhesive composition that can be applied to high-speed coating, and the pressure-sensitive adhesive composition obtained is significantly thickened by dissolution or swelling. (Meth) acrylate having a solubility in water of 0.1 or less is preferable, and 2-ethylhexyl (meth) acrylate is more preferable.

[Structural unit (b2)]
The copolymer (B) used in the present invention contains the structural unit (b2) derived from the carboxyl group-containing unsaturated monomer (b2), thereby improving the cohesive force due to the crosslinking reaction with the crosslinking agent [C] described later. , Removability can be improved.

Content of the structural unit (b2) in a copolymer (B) is 25-50 mass%, Preferably it is 28-47 mass%, More preferably, it is 30-44 mass%, More preferably, it is 32-40 mass. %.
When the content of the structural unit (b2) is less than 25% by mass, a sufficient crosslinking bond is not formed with the crosslinking agent [C], and it becomes difficult to improve the cohesive force. As a result, the adhesive strength with time increases, which causes a decrease in removability. Moreover, when the said content exceeds 50 mass%, the viscosity of the adhesive composition obtained will become high and it will become difficult to respond | correspond to high-speed application | coating.

The monomer (b2) is a monomer having a carboxyl group in one molecule and having a carbon-carbon unsaturated bond, and the same monomer as the above-mentioned monomer (a2) can be used.
Specific examples of the monomer (b2) include ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid and citraconic acid; 2-carboxyl ethyl (meth) acrylate etc. are mentioned.
These monomers (b2) can be used alone or in combination of two or more.
Among these, from the viewpoint of versatility, ethylenically unsaturated monocarboxylic acid is preferable, (meth) acrylic acid is more preferable, it is easy to orient inside the emulsion particles, and from the viewpoint of preventing an increase in viscosity due to alkali swelling (dissolution). More preferred is methacrylic acid.

[Structural unit (b3)]
In the copolymer (B), polyfunctionality is used as an internal cross-linking agent for the purpose of preventing thickening of the resulting pressure-sensitive adhesive composition, suppressing an increase in adhesive strength over time, and improving removability. It is preferable to contain the structural unit (b3) derived from the monomer (b3).

As the monomer (b3), the same monomer (a3) can be used.
Specific monomers (b3) include, for example, (poly) ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, methylenebisacrylamide, divinylbenzene Etc.
These monomers (b3) may be used alone or in combination of two or more.
Among these, 1,6-hexanediol di (meth) acrylate and trimethylolpropane tri (meth) acrylate are preferable from the above viewpoint.

  Content of a structural unit (b3) in a copolymer (B) becomes like this. Preferably it is 0.1-5.0 mass%, More preferably, it is 0.5-4.0 mass%, More preferably, it is 1.0- 3.0% by mass. If content of a structural unit (b3) is 0.1 mass% or more, the raise of the adhesive force with time can be suppressed effectively and re-peelability can be improved. Moreover, if the said content is 5.0 mass% or less, the phenomenon in which adhesiveness with a base material and re-peelability fall can be prevented.

[Structural unit (b4)]
The copolymer (B) may be copolymerized with the monomer (b1) and may contain a structural unit (b4) derived from an unsaturated monomer (b4) other than the monomers (b1) and (b2). Good.
As unsaturated monomer (b4) other than monomer (b1), (meth) acrylic acid alkyl ester having an alkyl group having 1 to 7 carbon atoms, (meth) acrylic acid alkyl ester having an alkyl group having 19 or more carbon atoms, etc. Is mentioned.
Examples of the unsaturated monomer (b4) other than the monomer (b2) include the monomers exemplified as the monomer (a4) described above.

  The content of the structural unit (b4) in the copolymer (B) is preferably 25% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, and still more preferably 1% by mass or less. is there. If content of a structural unit (b4) is 25 mass% or less, the phenomenon in which adhesiveness with a base material falls can be prevented.

<Method for Producing Emulsions of Copolymers [A] and [B]>
The emulsion of the (meth) acrylic acid ester copolymer of the above [A] component and [B] component is the above-mentioned monomer (a1) to (a4), monomer (b1) to (b4), and other It can be produced by adding an emulsifier and a polymerization initiator to a mixture of monomers (hereinafter, also referred to as “monomer mixture”) and emulsion polymerization.

The emulsifier used is preferably an anionic emulsifier or a nonionic emulsifier, more preferably an anionic emulsifier, from the viewpoint of improving the stability of the emulsion and improving the mechanical stability of the pressure-sensitive adhesive composition.
Examples of the anionic emulsifier include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, and the like.
Examples of nonionic emulsifiers include polyoxyethylene alkyl ether and polyoxyethylene alkylphenyl ether.
A radical polymerizable reactive emulsifier into which a propenyl group, an acryloyl group or the like is introduced can also be used.
These emulsifiers may be used alone or in combination of two or more.

The amount of the emulsifier added is preferably 0.5 to 12 parts by mass, more preferably 0.8 to 8 parts by mass, and still more preferably 1 to 6 parts by mass with respect to 100 parts by mass of the monomer mixture. If the amount of the emulsifier added is 0.5 parts by mass or more, the emulsion polymerization can proceed stably. On the other hand, if it is 12 parts by mass or less, it is possible to prevent adverse effects such as deterioration of substrate adhesion, water whitening resistance, and removability due to remaining unreacted emulsifier.
The emulsifier may be added directly to a solution obtained by adding water to the monomer mixture, may be added in advance to the polymerization vessel, or may be used in combination.

The polymerization initiator to be used is not particularly limited and may be either water-soluble or oil-soluble.
Specific examples of the polymerization initiator include azo compounds such as 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 2,2′-azobis (2-amidinopropane) dihydrochloride, and persulfuric acid. Examples thereof include persulfates such as potassium, sodium persulfate and ammonium persulfate, peroxides such as benzoyl peroxide, t-butyl hydroperoxide and hydrogen peroxide. Moreover, you may use the redox initiator which consists of a combination of a persulfate and sodium hydrogensulfite, a combination of a peracid and sodium ascorbate, or the like.
These polymerization initiators may be used alone or in combination of two or more.
Among these, a persulfate or a redox initiator is preferable from the viewpoint of excellent polymerization stability.

  The addition amount of the polymerization initiator is preferably 0.01 to 6 parts by mass, more preferably 0.03 to 4 parts by mass, further preferably 100 parts by mass with respect to 100 parts by mass of the monomer mixture from the viewpoint of increasing the polymerization rate. 0.1 to 2 parts by mass.

The polymerization initiator may be added in advance to the polymerization vessel, may be added immediately before the start of polymerization, or may be added in a plurality of times after the start of polymerization. Moreover, you may add in advance in a monomer mixture, and after adding the emulsion liquid which consists of this monomer mixture, you may add to the said emulsion liquid.
In the addition, the polymerization initiator may be separately dissolved in a solvent or a monomer mixture and added, or the dissolved polymerization initiator may be further emulsified and added.

Moreover, you may add a chain transfer agent and a pH buffer further at the time of emulsion polymerization.
Examples of the chain transfer agent include lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, and 2,3-dimercapto-1-propanol.
The pH buffering agent is not particularly limited as long as it is a compound having a pH buffering action. For example, sodium bicarbonate, potassium bicarbonate, monosodium phosphate, monopotassium phosphate, disodium phosphate, trisodium phosphate, Examples include sodium acetate, ammonium acetate, sodium formate, and ammonium formate.

In the case of emulsion polymerization, the water used is preferably ion-exchanged water.
The amount of water used is preferably 30 to 400 parts by weight, more preferably 35 to 200 parts by weight, and still more preferably 40 to 150 parts by weight with respect to 100 parts by weight of the monomer mixture. If the usage-amount of water is 30 mass parts or more, the viscosity of the emulsion of the copolymer obtained can be made into an appropriate range. Further, the polymerization stability of the obtained copolymer is also improved. On the other hand, if it is 400 parts by mass or less, the solid content concentration of the emulsion of the copolymer to be obtained can be in an appropriate range, and the coating film is formed on a substrate or a release sheet to form a coating film. The formability of is improved.

The emulsion of the (meth) acrylic acid ester copolymer of [A] component and [B] component allows emulsion polymerization to proceed by adding a polymerization initiator to the monomer mixture in the presence of an emulsifier. Can be synthesized.
Examples of the procedure for carrying out the emulsion polymerization include the following methods (1) to (3), and the method (2) or (3) is preferable from the viewpoint of easy control of the polymerization temperature. The method (3) is more preferred.
(1) Charge the entire amount of monomer mixture, emulsifier, water, etc., raise the temperature, and add or completely add the polymerization initiator dissolved in water for polymerization.
(2) After charging water, an emulsifier and a part of the monomer mixture in the reaction vessel and raising the temperature, a polymerization initiator dissolved in water is dropped or dividedly added to advance the polymerization reaction, and then the rest The whole monomer mixture is added dropwise or dividedly and polymerization is continued.
(3) A polymerization initiator dissolved in water is charged in the reaction vessel and the temperature is raised, and then the whole amount of an emulsion consisting of a monomer mixture, an emulsifier and water is added dropwise or dividedly for polymerization.

Although it does not specifically limit as polymerization conditions in the said polymerization method, It is preferable to carry out on the following conditions.
In the method (1), the temperature range is preferably 40 to 100 ° C., and the polymerization reaction is preferably performed in about 1 to 8 hours after the start of the temperature increase.
In the method (2), 1 to 50% by mass of the monomer mixture is polymerized at 40 to 90 ° C. for 0.1 to 4 hours, and then the remaining monomer mixture is dropped over about 1 to 5 hours. Alternatively, it is preferable to add in portions and then ripen at the same temperature for about 1 to 3 hours.
In the method (3), the polymerization initiator dissolved in water is preferably heated to 40 to 90 ° C., and the whole amount of the emulsion composed of the monomer mixture, the emulsifier and water is dropped over about 2 to 5 hours. Alternatively, it is preferable to add in portions. Moreover, it is preferable to age | cure | ripen for 1 to 5 hours after that at the same temperature.

  In the above polymerization method, from the viewpoint of polymerization stability, the monomer mixture is prepared by dissolving an emulsifier (or a part of the emulsifier) in the monomer mixture or by using an O / W type emulsion in advance. It is preferable to be in a state.

To the copolymer emulsion obtained by the above polymerization method, an aqueous alkaline solution such as aqueous ammonia, various water-soluble amines, an aqueous sodium hydroxide solution, an aqueous potassium hydroxide solution, and the like is further added to give a pH of 5-9, preferably a pH of 6-6. You may adjust to 8.5.
For the copolymer [A] emulsion, it is preferable to adjust the pH to the above range by adding the alkaline aqueous solution.
On the other hand, the copolymer [B] emulsion has a pH of 2 to 5 without adding the alkaline aqueous solution from the viewpoint of preventing swelling before mixing with the copolymer [A] emulsion. It is preferable to adjust to.
The alkaline aqueous solution can be added during the polymerization or after the completion of the polymerization. From the viewpoint of the polymerization stability and the viscosity stability over time of the resulting emulsion, it is partially or fully cooled after cooling to room temperature in the aging stage during the polymerization. Is preferably added.

  Suitable ranges of the physical property values of the copolymers [A] and [B] obtained as described above are as follows. In addition, each following physical-property value means the value measured by the method as described in an Example.

The solid content concentration of the copolymer [A] emulsion is preferably 10 to 80% by mass, more preferably 25 to 70% by mass, and still more preferably 45 to 65% by mass.
The solid content concentration of the copolymer [B] emulsion is preferably 10 to 80% by mass, more preferably 15 to 60% by mass, and still more preferably 20 to 40% by mass.

The viscosity of the copolymer [A] emulsion at 25 ° C. is preferably 30 to 400 mPa · s, more preferably 50 to 300 mPa · s, and still more preferably 75 to 200 mPa · s.
The viscosity of the copolymer [B] emulsion at 25 ° C. is preferably 1 to 100 mPa · s, more preferably 3 to 50 mPa · s, and still more preferably 5 to 20 mPa · s.

The average particle size of the copolymer [A] emulsion is preferably 100 to 900 nm, more preferably 200 to 600 nm, and still more preferably 300 to 500 nm.
The average particle size of the copolymer [B] emulsion is preferably 100 to 900 nm, more preferably 150 to 500 nm, and still more preferably 200 to 350 nm.

<Crosslinking agent [C]>
The crosslinking agent [C] contained in the pressure-sensitive adhesive composition of the present invention is a carboxyl of water-dispersed (meth) acrylic acid ester copolymer [A] and water-dispersed (meth) acrylic acid ester copolymer [B]. A compound that crosslinks with a group.
Examples of the crosslinking agent [C] include an epoxy compound, an oxazoline compound, a carbodiimide compound, an aziridine compound, a polyisocyanate compound, a melamine compound, a metal complex compound, an amine compound, adipic acid dihydrazide, and sebacic acid dihydrazide. Hydrazine derivatives and the like.
These crosslinking agents may be used alone or in combination of two or more.

  Among the above crosslinking agents [C], adhesion between the substrate and the pressure-sensitive adhesive layer, removability from the adherend, the effect of suppressing the increase in adhesive strength with time after being attached to the adherend, and stain resistance From the viewpoint of improvement, any one or more of an epoxy compound, an oxazoline compound, and a carbodiimide compound is preferable, and an epoxy compound is more preferable.

The epoxy compound is preferably a compound having two or more epoxy groups or glycidyl groups in the molecule.
As such an epoxy compound, for example, bisphenol A / epichlorohydrin type epoxy resin, sorbitol polyglycidyl ether (commercially available products are trade names “Denacol EX-611”, “Denacol EX-” manufactured by Nagase ChemteX Corporation, for example. 612 "," Denacol EX-614 "," Denacol EX-614B "," Denacol EX-622 ", etc.), polyglycerol polyglycidyl ether (commercially available product names" Denacol EX-512 "manufactured by Nagase ChemteX Corporation) ”,“ Denacol EX-521 ”, etc.), pentaerythritol polyglycidyl ether (commercially available products such as“ Denacol EX-411 ”manufactured by Nagase ChemteX Corporation), diglycerol polyglycidyl ether (as commercial products) Is an illustration Trade name “Denacol EX-421” manufactured by Nagase ChemteX Corporation), glycerol polyglycidyl ether (commercially available products, for example, trade names “Denacol EX-313”, “Denacol EX-314” manufactured by Nagase ChemteX Corporation) Etc.), trimethylolpropane polyglycidyl ether (commercially available products such as “Denacol EX-321” manufactured by Nagase ChemteX Corp.), neopentyl glycol diglycidyl ether (commercially available products such as Nagase Chemex, Inc., trade name “Denacol EX-212”, etc.), 1,6-hexanediol diglycidyl ether (commercially available product, trade name “Denacol EX-212”, etc., manufactured by Nagase ChemteX) Ethylene glycol diglycidyl ether (as a commercial product, For example, trade names “Denacol EX-810” and “Denacol EX-811” manufactured by Nagase ChemteX Corporation), diethylene glycol diglycidyl ether (commercially available products include, for example, trade names “Denacol EX-” manufactured by Nagase ChemteX Corporation). 850 "," Denacol EX-851 ", etc.), polyethylene glycol diglycidyl ether (commercially available products include, for example, trade names" Denacol EX-821 "," Denacol EX-830 "," Denacol EX "manufactured by Nagase ChemteX Corporation). -832 "," Denacol EX-841 "," Denacol EX-861 ", etc.), propylene glycol diglycidyl ether (as commercial products, for example, trade name" Denacol EX-911 "manufactured by Nagase ChemteX Corporation), Polypropylene glycol diglycidyl ether (As commercial products, for example, trade names “Denacol EX-941”, “Denacol EX-920”, “Denacol EX-931”, etc., manufactured by Nagase ChemteX Corporation), diglycidylaniline, N, N, N ′, N'-tetraglycidyl-m-xylenediamine, 1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane and the like can be mentioned.
Among these, an aqueous type crosslinking agent is preferable, and glycerol polyglycidyl ether is more preferable.

As the oxazoline-based compound, a compound having two or more oxazoline groups in the molecule is preferable.
Examples of such an oxazoline compound include addition-polymerizable 2-oxazoline (for example, 2-isopropenyl-2-oxazoline) having a substituent having an unsaturated carbon-carbon bond at the 2-position carbon position, and other non-polymerizable compounds. Examples thereof include a copolymer with a saturated monomer.
Examples of the copolymer include “Epocross WS-500”, “Epocross WS-700”, “Epocross K-2010E”, “Epocross K-2020E”, “Epocross K-2030E” (all trade names, Japan Catalyst Co., Ltd.).

As the carbodiimide compound, a compound having two or more carbodiimide groups in the molecule is preferable.
Examples of such carbodiimide compounds include “Carbodilite V-02”, “Carbodilite V-02-L2”, “Carbodilite V-04”, “Carbodilite V-06”, “Carbodilite E-01”, “Carbodilite E”. -02 "," Carbodilite E-04 "(both trade names, manufactured by Nisshinbo Co., Ltd.), etc.

<Other additives>
The water-dispersed pressure-sensitive adhesive composition of the present invention may contain other additives as long as the effects of the present invention are not impaired.
Other additives include, for example, (polymerization) rosin resins, (polymerization) rosin ester resins, terpene resins, terpene phenol resins and other tackifying resins, adipic acid diesters, fumaric acid diesters, sebacic acid Plasticizers such as diesters, dialkyl ester succinates, silicone surfactants, fluorosurfactants, acetylenic diol surfactants, wetting agents, softeners, fillers, pigments, dyes, anti-aging Agents, thickeners, antifoaming agents, preservatives and the like.

<Physical properties of water-dispersed pressure-sensitive adhesive composition>
The water-dispersed pressure-sensitive adhesive composition of the present invention is obtained by mixing the above-mentioned components [A] to [C] and other additives contained as necessary.
Hereinafter, suitable ranges of the physical property values of the water-dispersed pressure-sensitive adhesive composition of the present invention are as follows. In addition, the following physical-property values mean the value measured by the method as described in an Example.

The gel fraction when the pressure-sensitive adhesive layer formed from the water-dispersed pressure-sensitive adhesive composition of the present invention is dissolved in tetrahydrofuran (THF) is 63 to 95% by mass, preferably 65 to 90% by mass. Preferably it is 67-85 mass%, More preferably, it is 70-80 mass%, More preferably, it is 71-77 mass%.
When the gel fraction is less than 63% by mass, the pressure-sensitive adhesive layer formed from the obtained pressure-sensitive adhesive composition has insufficient cohesive force, so that the adhesive strength with time increases and the removability tends to be inferior. In addition, the pressure-sensitive adhesive layer protrudes, and secondary workability such as cutting and punching of the pressure-sensitive adhesive sheet is poor. On the other hand, when the gel fraction exceeds 95% by mass, the pressure-sensitive adhesive sheet using the obtained pressure-sensitive adhesive composition has poor adhesion to an adherend having a relatively rough surface such as corrugated cardboard. Tend to be inferior.

The viscosity at 25 ° C. of the water-dispersed pressure-sensitive adhesive composition of the present invention is preferably 500 mPa · s or less, more preferably 100 to 500 mPa · s, more preferably 130 to 400 mPa · s, from the viewpoint of corresponding to high-speed coating. More preferably, it is 160-350 mPa * s, More preferably, it is 180-320 mPa * s.
If the viscosity is 500 mPa · s or less, high-speed coating can be supported. Further, if the viscosity is 100 mPa · s or less, the coating film may be repelled.

The weight average molecular weight (Mw) of the tetrahydrofuran-soluble component (hereinafter also referred to as “THF-soluble component”) of the pressure-sensitive adhesive layer formed from the water-dispersed pressure-sensitive adhesive composition of the present invention is preferably 20,000 to 250,000. More preferably, it is 100,000-220,000, More preferably, it is 120,000-200,000. If Mw of the said THF soluble component is 20,000 or more, the initial stage adhesive force of the adhesive composition obtained can be made favorable. Moreover, if Mw of the said THF soluble component is 250,000 or less, the deformation | transformation by external pressure can be suppressed.
The molecular weight distribution (Mw / Mn) (where Mn is the number average molecular weight) of the THF-soluble component is preferably 2.0 to 5.0, more preferably 2.3 to 4.3, and still more preferably. It is 2.5 to 4.0, more preferably 2.7 to 3.8. If the value of the molecular weight distribution of the THF-soluble component is 2.0 or more, the initial adhesive strength of the obtained adhesive composition can be improved. Moreover, if the value of the molecular weight distribution of the THF-soluble component is 5.0 or less, an increase in adhesive strength over time can be suppressed, and re-peelability can be improved.

[Removable adhesive sheet]
The re-peelable pressure-sensitive adhesive sheet of the present invention (hereinafter also simply referred to as “pressure-sensitive adhesive sheet”) has a pressure-sensitive adhesive layer comprising the above-mentioned water-dispersed pressure-sensitive adhesive composition of the present invention, and the pressure-sensitive adhesive layer is used as a base material. The pressure-sensitive adhesive sheet provided on the top is preferable.
The thickness of the pressure-sensitive adhesive layer after drying the pressure-sensitive adhesive sheet is preferably 5 to 100 μm, more preferably 10 to 60 μm, and still more preferably 15 to 40 μm. When the thickness of the pressure-sensitive adhesive layer is 5 μm or more, sufficient pressure-sensitive adhesive performance is obtained, and when it is 100 μm or less, the pressure-sensitive adhesive layer can be prevented from protruding.

Although the structure of the adhesive sheet of this invention is not specifically limited, For example, the adhesive sheet of the aspect of FIG. 1 is mentioned. FIG. 1 is a cross-sectional view of a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive composition of the present invention is provided on a substrate.
As a specific configuration of the pressure-sensitive adhesive sheet of the present invention, as shown in FIG. 1A, a pressure-sensitive adhesive sheet with a base material in which a pressure-sensitive adhesive layer 11 is provided on one surface of a base material 12, or FIG. As in b), a pressure-sensitive adhesive sheet 1b in which a release sheet 13 is further provided on the pressure-sensitive adhesive layer 11 is exemplified.

  The base material of the pressure-sensitive adhesive sheet is not particularly limited, for example, polyester such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyimide, polyetherimide, polyaramid, polyetherketone, polyetheretherketone, polyphenylenesulfide, Poly (4-methylpentene-1) polyethylene, polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyurethane, ethylene-vinyl acetate copolymer, ionomer resin, ethylene (meth) Acrylic acid copolymer, polystyrene, polycarbonate, fluororesin, low density polyethylene, linear low density polyethylene, triacetyl cellulose resin film, etc. Paper sheets such as synthetic paper, metal deposits, high quality paper, coated paper, glassine paper, etc., and laminates obtained by laminating thermoplastic resins such as polyethylene on these paper base materials For example, paper.

  Although the thickness of a base material is suitably selected by the kind of base material to be used, Preferably it is 5-300 micrometers, More preferably, it is 10-120 micrometers.

The release sheet 13 shown in FIG. 1B is obtained by applying a release agent to one or both sides of the release sheet substrate.
Examples of the base material for the release sheet include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene, polypropylene, polybutene, polybutadiene, polymethylpentene, polyvinyl chloride, vinyl chloride copolymer, polyurethane, ethylene- Vinyl acetate copolymer, ionomer resin, ethylene (meth) acrylic acid copolymer, polystyrene, polycarbonate, fluororesin, low density polyethylene, linear low density polyethylene, triacetyl cellulose resin film, fine paper, coated paper And paper base materials such as glassine paper, and laminated paper obtained by laminating a thermoplastic resin such as polyethylene on these paper base materials.

  Examples of the release agent to be used include silicone resins, olefin resins, long chain alkyl resins, alkyd resins, fluorine resins, rubber elastomers such as isoprene resins and butadiene resins.

  Although there is no restriction | limiting in particular in the thickness of a peeling sheet, Preferably it is 5-300 micrometers, More preferably, it is 10-200 micrometers. In addition, when using a polyethylene terephthalate-type film as a base material for peeling sheets, it is preferably 10-100 micrometers.

[Method for producing re-peelable pressure-sensitive adhesive sheet]
The water-dispersed pressure-sensitive adhesive composition of the present invention has excellent applicability even in high-speed application at an application speed of 150 m / min or more. Therefore, even if the water-dispersed pressure-sensitive adhesive composition of the present invention is applied on the base material or release sheet at a high speed, the occurrence of repellency can be suppressed and the surface state of the formed coating layer can be improved.
The method for producing a re-peelable pressure-sensitive adhesive sheet of the present invention comprises applying the water-dispersed pressure-sensitive adhesive composition of the present invention at a coating speed of 150 m / min or more to form a coating film, drying the coating film, Forming a layer.

In the manufacturing method of this invention, it is preferable to apply | coat an adhesive composition on a base material or a peeling sheet, and to form a coating film.
For example, as a method for producing the pressure-sensitive adhesive sheet 1a shown in FIG. 1 (a), a method for producing the pressure-sensitive adhesive layer 11 by applying the pressure-sensitive adhesive composition of the present invention on the substrate 12, After the pressure-sensitive adhesive composition of the present invention was applied on the release sheet to form the pressure-sensitive adhesive layer 11, the pressure-sensitive adhesive layer 11 and the base material 12 were bonded together, and once shown in FIG. Examples include a method of producing the pressure-sensitive adhesive sheet 1b after removing the release sheet.
Moreover, as a manufacturing method of the adhesive sheet 1b shown by (b) of FIG. 1, the adhesive composition of this invention is apply | coated on the base material 12, the adhesive layer 11 is formed, and also the adhesive layer 11 A method of manufacturing by laminating the release sheet 13 on the top, or after applying the pressure-sensitive adhesive composition of the present invention on the release sheet 13 to form the pressure-sensitive adhesive layer 11, the pressure-sensitive adhesive layer 11 and the substrate 12 are then combined. For example, a method of manufacturing by bonding.

  In the production method of the present invention, the coating speed of the pressure-sensitive adhesive composition is 150 m / min or more, but the viewpoint of improving the productivity of the pressure-sensitive adhesive sheet and the generation of repellency are suppressed, and the surface state of the formed coating layer is good. From the viewpoint of, it is preferably 200 to 500 m / min, more preferably 250 to 500 m / min, and still more preferably 300 to 500 m / min.

  As a method for applying the pressure-sensitive adhesive composition of the present invention on a substrate or a release sheet, a known method can be used, for example, a gravure coating method, a bar coating method, a spray coating method, a roll coating method, a die coating method. , Knife coating method, air knife coating method, lip coating method, curtain coating method and the like.

  The drying conditions of the formed coating film depend on the drying ability of the coating machine, but are preferably dried by heating at a temperature of about 80 ° C. to 150 ° C. for about 3 seconds to 1 minute. Through this drying step, the pressure-sensitive adhesive layer can be formed.

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to the following examples.
Moreover, each physical property of the emulsion obtained by the following synthesis examples, the water dispersion-type adhesive composition obtained by the Example and the comparative example, and a releasable adhesive sheet was measured and evaluated based on the method shown below.

(1) Solid content concentration of emulsion and water-dispersed pressure-sensitive adhesive composition According to JIS K-6833, the emulsion or water-dispersed pressure-sensitive adhesive composition was dried at 107 ° C. for 3 hours, and then the residue was weighed. The solid content concentration was calculated from the equation.
Solid content concentration (% by mass) = (Mass of residue) / (Mass of emulsion before drying or water-dispersed pressure-sensitive adhesive composition) × 100

(2) Viscosity According to JIS K-6833, a BM type viscometer (manufactured by Tokyo Keiki Co., Ltd.) was used in an environment of 25 ° C. Using two rotors, the viscosity of the emulsion or water-dispersed pressure-sensitive adhesive composition was measured at 60 rpm.

(3) Average particle diameter of emulsion Value obtained by measuring the volume-based median diameter at 25 ° C. using a dynamic light scattering particle size distribution measuring device (manufactured by Horiba, Ltd., product name “LB-550”). Was used (unit: nm).

(3) Gel fraction of the pressure-sensitive adhesive layer About 500 mg of the pressure-sensitive adhesive layer is taken out from the obtained pressure-sensitive adhesive sheet for measuring the gel fraction, the accurate mass of the pressure-sensitive adhesive layer is measured in advance, and the pressure-sensitive adhesive layer before immersion The mass of was determined. Next, the pressure-sensitive adhesive layer was wrapped in stainless steel (SUS) mesh # 300 to prepare a test sample.
Then, the test sample was immersed in 100 mL of tetrahydrofuran for 72 hours in an environment of 23 ° C. and 50% RH (relative humidity), then the test sample was taken out, dried at 120 ° C. for 3 hours, and the mass of the test sample was measured. The mass of the pressure-sensitive adhesive layer after immersion was determined. The gel fraction of the pressure-sensitive adhesive layer was calculated from the following formula.
Gel fraction (mass%) = (mass of adhesive layer after immersion) / (mass of adhesive layer before immersion) × 100
("Mass of pressure-sensitive adhesive layer after immersion" is calculated from "(mass of test sample after immersion)-(mass of SUS mesh)".)

(4) Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of tetrahydrofuran soluble component
When the pressure-sensitive adhesive layer was taken out from the releasable pressure-sensitive adhesive sheet obtained by the measurement in (3) above and immersed in 100 mL of tetrahydrofuran for 72 hours, a gel permeation chromatograph apparatus (Tosoh Corporation) Product, product name “CCP8000”) under the following conditions, and values measured in terms of standard polystyrene were used.
(Measurement condition)
・ Column: “TSK guard column HXL-H” “TSK gel GMHXL (× 2)” “TSK gel G2000HXL” (both manufactured by Tosoh Corporation)
-Column temperature: 40 ° C
・ Developing solvent: Tetrahydrofuran ・ Flow rate: 1.0 mL / min

(5) Initial adhesive strength, time-dependent adhesive strength Measured according to JIS Z-0237 180 ° peel adhesive strength measurement.
Specifically, the adhesive sheet for re-peeling is cut to a width of 25 mm, and affixed to a stainless steel (SUS) plate, polystyrene (PS) plate, and K liner paper, respectively, and a 2 kg roller is placed on the attached adhesive sheet for re-peeling. 1 reciprocating.
The initial adhesive force was measured by peeling off the re-peeling adhesive sheet at a peeling speed of 300 mm / min immediately after pressure bonding with the roller.
In addition, the adhesive strength with time is pressure-bonded with the above roller, left at 23 ° C. and 50% RH (relative humidity) for 24 hours, and then peeled off the re-peeling adhesive sheet at a peeling speed of 300 mm / min. It was measured.

(6) Re-peelability The re-peelable pressure-sensitive adhesive sheet was cut to a width of 25 mm, adhered to a stainless steel (SUS) plate, a polystyrene (PS) plate, and K liner paper, and left in an environment of 40 ° C. for 7 days. Thereafter, the temperature was returned to 23 ° C. and 50% RH (relative humidity), and peeled by hand in the direction of 120 ° at a speed of 10 m / min, and the peeled state was visually evaluated according to the following criteria.
A: It can be peeled cleanly without glue residue or paper tearing.
B: There is a slight tearing of the paper at the edge, but there is no practical problem.
C: There are some glue residue and paper breakage.
D: There are adhesive residue and paper tears on the entire surface.

(7) Surface state of coating film The water-dispersed pressure-sensitive adhesive composition prepared in Examples and Comparative Examples was prepared by using a release sheet (trade name “SP-8K Ao” manufactured by Lintec Co., Ltd., glassine paper released by silicone resin). Using a lip coater, the peel-treated surface was coated so that the thickness of the pressure-sensitive adhesive layer after drying was 20 μm at a coating speed of 300 m / min. It was evaluated by.
A: There are no streaks, repellency, and blemishes, and the surface state is smooth and good.
F: Any of muscle, cistern and chijimi is seen, and the surface state is inferior.

Synthesis Examples 1 to 3 ([A] component)
As a anionic emulsifier, polyoxyethylene alkyl ether sodium sulfate salt (trade name “Latemul E-118B, manufactured by Kao Corporation) 4) parts by mass and 56 parts by mass of ion-exchanged water were added, mixed and emulsified to prepare an emulsion.
Next, 28 parts by mass of ion-exchanged water is added to a reactor equipped with a thermometer, a stirrer, a dripping device, a reflux condenser, and a nitrogen introduction tube, and nitrogen is enclosed to raise the temperature in the reactor to 80 ° C. While maintaining the temperature at 80 ° C., 2 parts by mass of a 10% by weight ammonium persulfate aqueous solution was added as a polymerization initiator, and immediately thereafter, the prepared emulsion was continuously added dropwise over 4 hours to emulsify. Polymerized. In parallel, 4 parts by mass of an aqueous ammonium persulfate solution having a concentration of 5% by mass was dropped.
After completion of the dropwise addition, the mixture was aged at 80 ° C. for 4 hours, then cooled to room temperature (25 ° C.), neutralized by adding ammonia water, and then further added with ion-exchanged water to obtain a solid content concentration of 56.5% by mass. A solution of acrylic acid ester copolymer emulsions (A-1) to (A-3) having a viscosity of 120 mPa · s and a pH of 8.0 was obtained.

Synthesis Examples 4 to 9 ([B] component)
As a anionic emulsifier, polyoxyethylene alkyl ether sodium sulfate salt (trade name “Latemul E-118B, manufactured by Kao Corporation) 4) parts by mass and 56 parts by mass of ion-exchanged water were added, mixed and emulsified to prepare an emulsion.
Next, 28 parts by mass of ion-exchanged water is added to a reactor equipped with a thermometer, a stirrer, a dripping device, a reflux condenser, and a nitrogen introduction tube, and nitrogen is enclosed to raise the temperature in the reactor to 80 ° C. While maintaining the temperature at 80 ° C., 2 parts by mass of a 10% by weight ammonium persulfate aqueous solution was added as a polymerization initiator, and immediately thereafter, the prepared emulsion was continuously added dropwise over 4 hours to emulsify. Polymerized.
After completion of the dropwise addition, the mixture was aged at 80 ° C. for 4 hours, and then cooled to room temperature (25 ° C.), and the acrylic acid ester copolymer emulsion (B -1) to (B-6) were obtained.

Examples 1-6, Comparative Examples 1-7
“Aerosol OT-75” as a wetting agent for each component of the types and blending amounts (solid content ratio) shown in Table 3: an anionic surfactant (containing sodium dioctyl sulfosuccinate, 75 mass% solid content) manufactured by Kao Corporation Were mixed with 0.3 part by mass (solid content ratio) to 100 parts by mass (solid content) of components [A-1] to [A-3] to prepare a water-dispersed pressure-sensitive adhesive composition.
Apply the lip coater to the release treated surface of the release sheet (trade name “SP-8K Ao” manufactured by Lintec Corporation, glassine paper peeled with silicone resin, thickness: 66 μm). It was applied at a coating speed of 300 m / min so that the thickness of the pressure-sensitive adhesive layer after drying was 20 μm, and dried to form a pressure-sensitive adhesive layer. And on the said adhesive layer, it bonded together with the quality paper (Nippon Paper Industries, brand name "New NPi quality", 64 g / m < ² >, thickness: 73 micrometers), and produced the adhesive sheet.
In addition, for gel fraction measurement, a gel fraction measurement pressure-sensitive adhesive sheet was prepared by laminating the release sheet “SP-8K Ao” instead of the high-quality paper “New NPi quality” in the production of the pressure-sensitive adhesive sheet. Each physical property test using the obtained pressure-sensitive adhesive sheet was conducted after leaving it to stand at 23 ° C. for 7 days or more.
About the prepared water-dispersed pressure-sensitive adhesive composition, viscosity, gel fraction, weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of tetrahydrofuran-soluble components, and initial pressure-sensitive adhesive force and time-dependent pressure-sensitive adhesive force of the produced pressure-sensitive adhesive sheet The removability and the surface state of the coating film were evaluated by the above-described methods and standards. The results are shown in Table 3.

In addition, the abbreviation of the component in the adhesive composition of Table 3 shows the following components.
A-1 to 3: An emulsion of an acrylate copolymer obtained in Synthesis Examples 1 to 3 described above.
B-1 to 6: An emulsion of an acrylate copolymer obtained in Synthesis Examples 4 to 9 above.
EX-313: manufactured by Nagase ChemteX Corporation, trade name “Denacol EX-313”, epoxy-based crosslinking agent (glycerol polyglycidyl ether).
V-04: manufactured by Nisshinbo Co., Ltd., trade name “Carbodilite V-04”, carbodiimide-based crosslinking agent.
WS-700: manufactured by Nippon Shokubai Co., Ltd., trade name “Epocross WS-700”, oxazoline-based crosslinking agent.

The removable pressure-sensitive adhesive sheets of Examples 1 to 6 were excellent in both initial adhesive force and time-dependent adhesive force for any of the adherends, and had good removability. Moreover, the application | coating surface at the time of apply | coating the adhesive composition prepared in Examples 1-6 did not have a stripe | line | muscle, repellency, and a chijimi, and the surface state was also favorable.
On the other hand, in Comparative Examples 1-3, since the gel fraction when dissolved in THF of the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition is low, the re-peelability of the obtained re-peelable pressure-sensitive adhesive sheet is poor. It became.
Moreover, in Comparative Examples 4-7, since the specific [A] component or [B] component is not contained, the viscosity of the obtained adhesive composition is high, and the surface state of the coating film is clearly inferior. there were. Therefore, the process was completed without evaluating items other than the viscosity and the surface state of the coating film.

The water-dispersible pressure-sensitive adhesive composition of the present invention can form a coating film having a good surface state even when applied at high speed, and the releasable pressure-sensitive adhesive sheet using the pressure-sensitive adhesive composition has excellent adhesive strength. And can suppress an increase in adhesive strength over time and has excellent removability.
Therefore, the water-dispersed pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive product such as a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer such as a pressure-sensitive adhesive label, a masking tape or sheet, or a surface protective film, which is assumed to be peeled off after long-term use. It can be applied to the production by high speed coating.

1a, 1b, 2a, 2b Removable adhesive sheet 11, 11a, 11b Adhesive layer 12 Base material 13, 13a, 13b Release sheet

Claims (9)

  A structural unit (a1) derived from a (meth) acrylic acid alkyl ester having an alkyl group having 4 to 12 carbon atoms as a main component and a structural unit (a2) derived from a carboxyl group-containing unsaturated monomer from 0.1 to 2. A (meth) acrylic acid ester copolymer emulsion [A] containing 0% by mass, containing a structural unit (b1) derived from a (meth) acrylic acid alkyl ester having an alkyl group having 8 to 18 carbon atoms as a main component and carboxyl Water-dispersed pressure-sensitive adhesive composition containing (meth) acrylate copolymer emulsion [B] containing 25 to 50% by mass of the structural unit (b2) derived from the group-containing unsaturated monomer, and a crosslinking agent [C] The gel fraction when the pressure-sensitive adhesive layer formed from the water-dispersed pressure-sensitive adhesive composition is dissolved in tetrahydrofuran is 63 to 95% by mass. Water-dispersed PSA composition.   The water-dispersed pressure-sensitive adhesive composition according to claim 1, wherein the water-dispersed pressure-sensitive adhesive composition has a viscosity at 25 ° C of 500 mPa · s or less.   The water-dispersed pressure-sensitive adhesive composition according to claim 1 or 2, wherein the emulsion [A] and [B] have an average particle diameter of 100 to 900 nm.   The water according to any one of claims 1 to 3, wherein the (meth) acrylic acid alkyl ester having an alkyl group having 8 to 18 carbon atoms constituting the structural unit (b1) is 2-ethylhexyl (meth) acrylate. Dispersive pressure-sensitive adhesive composition.   The water-dispersed pressure-sensitive adhesive composition according to any one of claims 1 to 4, wherein the emulsion [B] of the (meth) acrylic acid ester copolymer further contains a structural unit (b3) derived from a polyfunctional monomer.   The cross-linking agent [C] is a polyglycidyl compound having two or more glycidyl groups in the molecule, an oxazoline-based compound having two or more oxazoline groups in the molecule, and a carbodiimide having two or more carbodiimide groups in the molecule. The water-dispersed pressure-sensitive adhesive composition according to claim 1, which is at least one selected from the group consisting of a series compound.   The weight average molecular weight (Mw) of the tetrahydrofuran-soluble component of the pressure-sensitive adhesive layer formed from the water-dispersed pressure-sensitive adhesive composition is 20,000 to 250,000, and the molecular weight distribution (Mw / Mn) (where Mn is the number average) The water dispersion-type adhesive composition in any one of Claims 1-6 whose molecular weight is 2.0-5.0.   The process of apply | coating the water-dispersed adhesive composition in any one of Claims 1-7 at a coating speed of 150 m / min or more, forming a coating film, drying the said coating film, and forming an adhesive layer. The manufacturing method of the releasable adhesive sheet containing this.   A removable pressure-sensitive adhesive sheet obtained by the method for producing a removable pressure-sensitive adhesive sheet according to claim 8.