JP7295774B2 - adhesive composition - Google Patents

Description

The present invention relates to adhesive compositions.

Conventionally, natural rubber adhesives or acrylic adhesives are known as adhesives for adhesive tapes or adhesive sheets. As an acrylic adhesive, a (co)polymer having a specific alkyl (meth)acrylate as an essential structural unit has been developed (for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2004-143420

However, even with the technique of Patent Document 1, the adhesiveness in a wide temperature range was not sufficiently satisfactory. An object of the present invention is to provide a pressure-sensitive adhesive composition that exhibits excellent adhesiveness over a wide temperature range.

The present inventors arrived at the present invention as a result of conducting studies to achieve the above object. That is, the present invention contains a (co)polymer (A) containing, as constituent monomers, an alkyl (alkyl group having 4 to 8 carbon atoms) acrylate (a1) and a (meth)acrylate having a hydroxyl group (a2). Then, the hydroxyl group concentration of (A) is 1.0 to 4.0 mol / kg, and the molar ratio of the primary hydroxyl group and the secondary hydroxyl group of (A) [primary hydroxyl group / secondary hydroxyl group ] is 0/100 to 90/10; a pressure-sensitive adhesive composition (X) containing the main pressure-sensitive adhesive (B) and a polyfunctional (meth)acrylate (C) is.

The pressure-sensitive adhesive film (Y) using the pressure-sensitive adhesive composition (X) containing the main agent (B) for pressure-sensitive adhesives of the present invention exhibits the following effects.
(1) Excellent adhesiveness (adhesive strength, adhesive residue) in lamination at low temperature (5°C).
(2) Excellent adhesiveness (adhesive strength, adhesive residue) at high temperature (40°C) lamination.
(3) In addition to the above, deterioration of a metal (oxide) film, particularly an ITO (indium tin oxide) film can be suppressed.

<Alkyl (alkyl group has 4 to 8 carbon atoms) acrylate (a1)>
Examples of the alkyl (alkyl group having 4 to 8 carbon atoms) acrylate (a1) in the present invention include n-butyl acrylate, neopentyl acrylate, n-octyl acrylate and 2-ethylhexyl acrylate.
Among the above (a1), n-butyl acrylate and 2-ethylhexyl acrylate are preferred from the viewpoint of adhesiveness, n-butyl acrylate and 2-ethylhexyl acrylate are more preferred, and n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferred. is n-butyl acrylate.

<(Meth)acrylate (a2) having a hydroxyl group>
Examples of the (meth)acrylate (a2) having a hydroxyl group include (a21) having a primary hydroxyl group, (meth)acrylate (a22) having a secondary hydroxyl group, primary Examples thereof include (meth)acrylates (a23) having a hydroxyl group and a secondary hydroxyl group.
(Meth)acrylate means methacrylate and/or acrylate.

Examples of (a21) include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 2-hydroxy-1-methylethyl (meth)acrylate. be done.
Examples of (a22) include 2-hydroxypropyl (meth)acrylate and 2-hydroxybutyl (meth)acrylate.
Examples of (a23) include glycerin mono(meth)acrylate.

Among the above (a2), from the viewpoint of adhesiveness, those containing a (meth)acrylate having a secondary hydroxyl group are preferable, and (a22), (a23), (a21) and (a22) are more preferable. (a23), and (a21) and (a22) are particularly preferred.

<(Co)polymer (A)>
The (co)polymer (A) in the present invention contains the alkyl (alkyl group having 4 to 8 carbon atoms) acrylate (a1) and the hydroxyl group-containing (meth)acrylate (a2) as constituent monomers.
In addition, a constituent monomer may be abbreviated as a monomer.

Constituent monomers (monomers) other than the above (a1) and (a2) include, for example, a monomer having a carboxyl group (a3) and other monomers (a4) other than (a1) to (a3) is mentioned.

Examples of the monomer (a3) having a carboxyl group include monobasic acids such as (meth)acrylic acid and crotonic acid; polybasic acids such as maleic acid, itaconic acid and fumaric acid; Examples include monoalkyl esters of polybasic acids. Preferred among these are acrylic acid, methacrylic acid, maleic anhydride and itaconic acid.
Among the above (a3), acrylic acid is preferable from the viewpoint of adhesiveness.

Other monomers (a4) include, for example, vinyl esters [vinyl acetate, vinyl propionate, vinyl butyrate, etc.], (meth)acrylates [methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate , neopentyl methacrylate, n-octyl methacrylate, nonyl (meth)acrylate, 2-ethylhexyl methacrylate, decyl (meth)acrylate, lauryl (meth)acrylate, etc.].
Among the above (a4), vinyl acetate is preferable from the viewpoint of adhesiveness.

The (co)polymer (A) in the present invention is prepared by converting the monomers into a known polymerization initiator (azobisisobutyronitrile) by a known polymerization method (bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc.). , azo-based polymerization initiators such as azobisisovaleronitrile; peroxide-based polymerization initiators such as benzoyl peroxide, di-t-butyl peroxide, lauryl peroxide, etc.).
Among the above polymerization methods, a method of solution polymerization in the presence of a solvent (S) (eg, ethyl acetate) is preferable.

The weight average molecular weight (polystyrene equivalent) of the (co)polymer (A) by gel permeation chromatography (GPC) is preferably 100,000 to 600,000, more preferably 150, from the viewpoint of adhesiveness and handling. ,000 to 500,000, particularly preferably 200,000 to 400,000.

Measurement conditions for gel permeation chromatography (GPC) in the present invention are as follows.
Apparatus: "HLC-8120GPC" [manufactured by Tosoh Corporation]
Column: "Guard column HXL-H" (1 piece),
“TSKgel GMHXL” (2 bottles) [both manufactured by Tosoh Corporation]
Sample solution: 0.25% by weight tetrahydrofuran solution Solution injection volume: 100 μl
Flow rate: 1 ml/min Measurement temperature: 40°C
Detection device: refractive index detector Reference material: standard polystyrene

The (co)polymer (A) has a hydroxyl group concentration of 1.0 to 4.0 mol/kg, preferably 1.5 to 3.5 mol/kg, more preferably 2.0 to 3.0. mol/kg. If the hydroxyl group concentration is less than 1.0 mol/kg or more than 4.0 mol/kg, the balance of adhesion is poor. The hydroxyl group concentration can be calculated, for example, by measuring the hydroxyl value (KOHmg/g) according to JIS K0070.

Further, the molar ratio [primary hydroxyl group/secondary hydroxyl group] (β) of the primary hydroxyl group to the secondary hydroxyl group possessed by (A) is 0/100 to 90/10, preferably 10/90 to 70/ 30, more preferably 15/85 to 50/50. If the (β) does not satisfy the above range, the adhesion tends to be poorly balanced.
The (β) can be determined, for example, from the spectrum of ¹ H-NMR (nuclear magnetic resonance) spectroscopy.
Further, the concentration of hydroxyl groups in (A) and (β) can be adjusted by, for example, the type and weight of (a2) constituting (A).

Further, the carboxyl group concentration of the (co)polymer (A) is preferably 0 to 0.35 mol/kg, more preferably 0 to 0.17 mol/kg, from the viewpoint of adhesiveness and suppression of deterioration, especially It is preferably 0.01 to 0.09 mol/kg.
The carboxyl group concentration can be calculated, for example, by measuring the acid value (KOHmg/g) according to JIS K0070.
The carboxyl group concentration can be adjusted, for example, by adjusting the weight of (a3) among the constituent monomers of (A).

The total weight of (a1) and (a2) is preferably 70 to 100% by weight, more preferably 80 to 98% by weight, and particularly preferably 85 to 95% by weight, based on the weight of all monomers constituting (A). % by weight.
In addition, (a1) is preferably monoacrylate, (a2) is preferably mono(meth)acrylate, more preferably alkyl (alkyl group is a mono(meth)acrylate having 2 to 5 carbon atoms, more preferably 3 to 4 carbon atoms.

<Main agent for adhesive (B)>
The main ingredient (B) for pressure-sensitive adhesives of the present invention contains the (co)polymer (A). The main agent for pressure-sensitive adhesive (B) is suitable as a main agent for the pressure-sensitive adhesive composition (X) described below.
(B) may contain, for example, a solvent (S) in addition to (A) and (C). The weight of the solvent (S) is preferably 30% by weight or less, more preferably 2% by weight or less, based on the weight of (B).

<Polyfunctional (meth)acrylate (C)>
Examples of polyfunctional (meth)acrylates (C) in the present invention include the following (C1) to (C3).

Bifunctional (meth)acrylate having one hydroxyl group (C1):
For example, glycerin di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolethane di(meth)acrylate;

3- to 5-functional (meth)acrylate (C2) having one hydroxyl group:
For example, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, sorbitol penta(meth)acrylate, ditrimethylolpropane tri(meth)acrylate;

Tri- to hexa-functional (meth)acrylate (C3) having no hydroxyl group:
For example, glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, sorbitol hexa(meth)acrylate ) acrylates, ditrimethylolpropane tetra(meth)acrylate;

Among the polyfunctional (meth)acrylates (C), from the viewpoint of adhesiveness and adhesive residue, preferred are (C2), (C3), combination of (C2) and (C3), more preferred is (C2 ).

<Adhesive composition (X)>
The pressure-sensitive adhesive composition (X) of the present invention comprises a main agent for pressure-sensitive adhesives (B) containing the (co)polymer (A), and a polyfunctional (meth)acrylate (C). .
The (X) is preferably 75 to 97% by weight of (A) and 3 to 25% by weight of (C) based on the total weight of (A) and (C), more preferably (A ) is 80 to 95% by weight, and (C) is preferably 5 to 20% by weight, and particularly preferably (A) is 85 to 93% by weight and (C) is 7 to 15% by weight.

The pressure-sensitive adhesive composition (X) of the present invention is prepared by, for example, mixing a main agent for pressure-sensitive adhesive (B) containing a (co)polymer (A) and a polyfunctional (meth)acrylate (C). can be manufactured.
The (X) may be in the form of a solution of the solvent (S). From the viewpoint of handling, the solvent (S) is preferably 50% by weight or less based on the weight of (X), more preferably 5% by weight or less, particularly preferably 1% by weight or less.
In addition, the pressure-sensitive adhesive composition (X) of the present invention may optionally contain a tackifier (N) [terpene resin, rosin resin, etc.], a photopolymerization initiator, as long as the effects of the present invention are not impaired. (D), plasticizers, fillers, pigments, ultraviolet absorbers, antioxidants and the like can be further contained.

<Adhesive film (Y)>
The adhesive film (Y) of the present invention is an adhesive film having a cured layer of the adhesive composition (X). The thickness of the cured layer is preferably 10-200 μm, more preferably 20-100 μm.

The pressure-sensitive adhesive film of the present invention can be produced by directly applying the pressure-sensitive adhesive composition (X) to at least part of at least one side of a substrate using various coating devices, for example, by heating and/or active energy rays (UV , electron beam, etc.).
A preferred mode of use is a mode in which the composition is heated (hot-melted), applied, and cured with an active energy ray, as will be described later in Examples. That is, (X) can also be said to be an active energy ray-curable hot-melt pressure-sensitive adhesive composition.

Substrates (films) include films, sheets, foams and flat yarns of various plastics [polyolefin (polyethylene, polypropylene, etc.), polyurethane, polyethylene terephthalate, polyvinyl chloride, rayon, polyamide, etc.] and paper (Japanese paper, crepe paper, etc.). ), metal plates, metal foils, woven fabrics, non-woven fabrics, and wood.

The pressure-sensitive adhesive composition (X) containing the main agent (B) for pressure-sensitive adhesives of the present invention has excellent adhesiveness in a wide temperature range. (automobile moldings, emblems, marks, etc.), masking (glass sealing, architectural curing, etc.), surface protection (painted surface protection, etc.), medical use (adhesive plasters, etc.), office use, etc. can do. Furthermore, since deterioration of a metal (oxide) film, particularly an ITO (indium tin oxide) film can be suppressed, it can be suitably used for protecting electronic substrates.

EXAMPLES The present invention will be further described below with reference to Examples and Comparative Examples, but the present invention is not limited to these. Hereinafter, unless otherwise specified, % means % by weight, and part means part by weight.

<Example 1>
A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a nitrogen gas introduction tube was charged with 100 parts of ethyl acetate as a solvent and heated.
Next, while blowing nitrogen into the reaction vessel under reflux of the solvent, 85 parts of n-butyl acrylate (a1-1), 12 parts of 2-hydroxypropyl acrylate (a2-3), and 2-hydroxy-1-methyl <Monomer mixture> containing 3 parts of ethyl (meth)acrylate (a2-2) and 2,2′-azobis(2,4-dimethylvaleronitrile) [hereinafter sometimes abbreviated as V-65 ] was dissolved in 20 parts of ethyl acetate <initiator solution 1> was continuously added dropwise over 5 hours using a dropping funnel to carry out radical polymerization.
After the completion of dropping, <initiator solution 2> prepared by dissolving 0.11 parts of 2,2′-azobis(2,4-dimethylvaleronitrile) in 10 parts of ethyl acetate was added to the dropping funnel while stirring the system at the same temperature. was added continuously over 1 hour. Furthermore, after continuing the polymerization for 1 hour under reflux of the solvent, the mixture is heated to 130° C. under reduced pressure to distill off the ethyl acetate, and the main agent for pressure-sensitive adhesives containing the (co)polymer (A-1) is obtained. (B-1) was taken out.
The (co)polymer (A) has a weight average molecular weight (Mw) of 300,000, a hydroxyl group concentration of 1.2 mol/kg, a molar ratio (β) of 20/80, and a carboxyl group concentration of 0 mol/kg. there were.

<Examples 2 to 9, Comparative Example 1>
In Example 1, each main agent (B) for pressure-sensitive adhesive containing each (co)polymer (A) was obtained in the same manner as in Example 1 except that Table 1 was followed. Table 1 shows the results.

<Examples 11 to 27, Comparative Examples 11 to 12>
According to the formulation composition (parts) in Table 2, each formulation component was blended for 3 minutes in a Henschel mixer, and then melt-kneaded in a vented twin-screw extruder at 150 ° C., 100 rpm, and a residence time of 3 minutes. , to obtain each adhesive composition (X).
Each pressure-sensitive adhesive composition (X) thus obtained was melted at 150°C, and a slot coater was applied to the surface of a 25 µm polyester film ["Lumirror" type T, PET manufactured by Toray Industries, Inc.] at an environmental temperature of 23°C. The coating is applied at a coating amount of 30 g/m ² , and the coating film is cured using a UV irradiation device [Ushio Inc., “UVC-02516S1AA01”], light source: metal halide lamp, 1000 mJ / cm ² , Each adhesive film (Y) having a cured layer with a thickness of 30 μm was obtained.
Each pressure-sensitive adhesive film obtained was evaluated by the method described below. Table 2 shows the results.

<1> Adhesive strength at low temperature Based on JIS Z0237-2000 “Adhesive tape, adhesive sheet test method” using an adhesive film test piece [vertical 100 mm × horizontal 25 mm] cut from the adhesive film obtained above, the adhesive film and A PET film [0.18 mm in thickness, the same applies hereinafter] having an ITO layer was pasted together by one reciprocation of a 2 kg roller in an atmosphere of 5° C. to obtain a laminated film.
After lamination, it was left for 1 day under the conditions of 60°C and 90% RH, and the 180° peeling strength at 25°C was measured (25 mm width, tensile speed 300 mm/min) and measured according to the following criteria. evaluated.
<Evaluation Criteria>
◎: greater than 9N / 25mm ○: greater than 7N / 25mm, 9N / 25mm or less △: greater than 5N / 25mm, 7N / 25mm or less ×: 5N / 25mm or less

<2> Adhesive strength change at low temperature After laminating the laminated film obtained in <1> above, leave it for 14 days under the conditions of 5 ° C. and relative humidity of 90% RH, and peel it off at 180 ° at 25 ° C. The strength is measured (25 mm width, tensile speed 300 mm / min), and the difference from the peel strength in <1> is calculated by the following formula,
Evaluation was made according to the following evaluation criteria.
Change in adhesive strength at low temperature = Peel strength after 14 days - Peel strength after 1 day <Evaluation criteria>
◎: greater than 1 N / 25 mm, 2 N / 25 mm or less ○: greater than 0.5 N / 25 mm, 1 N / 25 mm or less △: greater than 0 N / 25 mm, 0.5 N / 25 mm or less ×: 0 N / 25 mm or less

<3> Remaining adhesive at low temperature The surface of the PET film having the ITO layer after 14 days obtained in <2> above was visually evaluated for the presence or absence of residual adhesive according to the following criteria.
<Evaluation Criteria>
◎: No glue residue ○: Almost no glue residue △: Slight glue residue ×: There is glue residue

<4> ITO layer deterioration test 1
The resistance value (R ₅ ) of the PET film having the ITO layer after peeling obtained in the above <2> was measured, the resistance change rate (%) was calculated by the following formula, and evaluated according to the following evaluation criteria. . Note that R ₀ indicates the resistance value (Ω) before bonding.
Rate of change in resistance value (%) = (R ₅ -R ₀ )/R ₀ ×100
<Evaluation Criteria>
◎: Less than 5% change rate ○: 5% or more, less than 10% change rate △: 10% or more, less than 20% change rate ×: 20% or more change rate

<5> Adhesive strength at high temperature Based on JIS Z0237-2000 “Adhesive tape, adhesive sheet test method” using an adhesive film test piece [vertical 100 mm × horizontal 25 mm] cut from the adhesive film obtained above, the adhesive film and A PET film having an ITO layer was pasted together by one reciprocation of a 2 kg roller in an atmosphere of 40°C.
After lamination, it was left for 1 day under the conditions of 60°C and 90% RH, and the 180° peeling strength at 25°C was measured (25 mm width, tensile speed 300 mm/min) and measured according to the following criteria. evaluated.
<Evaluation Criteria>
◎: greater than 9N / 25mm ○: greater than 7N / 25mm, 9N / 25mm or less △: greater than 5N / 25mm, 7N / 25mm or less ×: 5N / 25mm or less

<6> Adhesive strength change at high temperature After laminating the laminated film obtained in <5> above, leave it for 14 days under the conditions of 60 ° C. and 90% relative humidity RH, and peel it off at 180 ° at 25 ° C. The strength is measured (25 mm width, tensile speed 300 mm / min), and the difference from the peel strength in <5> is calculated by the following formula,
Evaluation was made according to the following evaluation criteria.
Change in adhesive strength at low temperature = Peel strength after 14 days - Peel strength after 1 day <Evaluation criteria>
◎: greater than 1 N / 25 mm, 2 N / 25 mm or less ○: greater than 0.5 N / 25 mm, 1 N / 25 mm or less △: greater than 0 N / 25 mm, 0.5 N / 25 mm or less ×: 0 N / 25 mm or less

<7> Remaining adhesive at high temperature The surface of the PET film having the ITO layer after 14 days obtained in <6> above was visually evaluated for the presence or absence of residual adhesive according to the following criteria.
<Evaluation Criteria>
◎: No glue residue ○: Almost no glue residue △: Slight glue residue ×: There is glue residue

<8> ITO layer deterioration test 2
The resistance value (R ₄₀ ) of the PET film having the ITO layer after peeling obtained in the above <6> was measured, the resistance change rate (%) was calculated by the following formula, and evaluated according to the following evaluation criteria. . Note that R ₀ indicates the resistance value (Ω) before bonding.
Rate of change in resistance value (%) = (R ₄₀ - R ₀ )/R ₀ ×100
<Evaluation Criteria>
◎: Less than 5% change rate ○: 5% or more, less than 10% change rate △: 10% or more, less than 20% change rate ×: 20% or more change rate

In addition, each compounding component used in Table 2 is as follows.
Multifunctional (meth)acrylate (C-1): Dipentaerythritol pentaacrylate Multifunctional (meth)acrylate (C-2): Pentaerythritol tetraacrylate Multifunctional (meth)acrylate (C-3): Pentaerythritol triacrylate Functional (meth) acrylate (C-4): glycerin dimethacrylate photoinitiator (D-1): manufactured by BASF, Irgacure 184, 1-hydroxycyclohexyl phenyl ketone

From the results in Tables 1 and 2, the pressure-sensitive adhesive composition (X) containing the main agent (B) for a pressure-sensitive adhesive of the present invention showed higher adhesiveness at low temperature (5°C) bonding and high temperature ( 40° C.) It can be seen that the adhesion in bonding is excellent, and deterioration of a metal (oxide) film, particularly an ITO (indium tin oxide) film can be suppressed.

The pressure-sensitive adhesive composition (X) containing the main agent (B) for pressure-sensitive adhesives of the present invention has excellent adhesiveness in a wide temperature range. (automobile moldings, emblems, marks, etc.), masking (glass sealing, architectural curing, etc.), surface protection (painted surface protection, etc.), medical use (adhesive plasters, etc.), office use, etc. can do. Furthermore, since deterioration of a metal (oxide) film, particularly an ITO (indium tin oxide) film can be suppressed, it can be suitably used for protection of electronic substrates, which is extremely useful.

Claims (4)

A (co)polymer (A) containing an alkyl (alkyl group having 4 to 8 carbon atoms) acrylate (a1) and a (meth)acrylate (a2) having a hydroxyl group as constituent monomers, A) has a hydroxyl group concentration of 1.0 to 4.0 mol/kg, and the molar ratio [primary hydroxyl group/secondary hydroxyl group] between the primary hydroxyl group and the secondary hydroxyl group of (A) is 0/100 to It contains a main agent for pressure-sensitive adhesive (B) which is 90/10 and a polyfunctional (meth)acrylate (C), and the polyfunctional (meth)acrylate (C) is a bifunctional ( meth) acrylate (C1), tri- to penta-functional (meth) acrylate (C2) having one hydroxyl group, or combination of (C2) and tri- to hexa-functional (meth) acrylate (C3) having no hydroxyl group Adhesive composition (X). 2. The adhesive composition according to claim 1, wherein the (co)polymer (A) has a carboxyl group concentration of 0 to 0.35 mol/kg. 3. The adhesive composition according to claim 1, wherein (A) is 75 to 97% by weight and (C) is 3 to 25% by weight, based on the total weight of (A) and (C). An adhesive film (Y) having a cured layer of the adhesive composition (X) according to any one of claims 1 to 3 .