JP2020076073A - Adhesive composition - Google Patents

Abstract

To provide an adhesive composition excellent in adhesiveness in a wide temperature range.SOLUTION: A main agent (B) for an adhesive agent includes a (co)polymer (A) including an alkyl (4-8 carbon atoms in an alkyl group) acrylate (a1) and a (meth)acrylate (a2) having a hydroxyl group as constituent monomers, wherein a hydroxyl group concentration of the (A) is 1.0-4.0 mol/kg and a molar ratio of a primary hydroxyl group and a secondary hydroxyl group included in the (A) [a primary hydroxyl group/a secondary hydroxyl group] is 0/100-90/10. A adhesive composition (X) includes the main agent (B) for an adhesive agent and a polyfunctional (meth)acrylate (C).SELECTED DRAWING: None

Description

  The present invention relates to an adhesive composition.

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

JP 2004-143420 A

  However, even the technique of Patent Document 1 described above was not sufficiently satisfactory in terms of tackiness in a wide temperature range. An object of the present invention is to provide a pressure-sensitive adhesive composition having excellent adhesiveness in a wide temperature range.

  The present inventors have arrived at the present invention as a result of studies to achieve the above object. That is, the present invention contains 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. The hydroxyl concentration of (A) is 1.0 to 4.0 mol / kg, and the molar ratio of the primary hydroxyl group and secondary hydroxyl group of (A) [primary hydroxyl group / secondary hydroxyl group]. ] The main ingredient (B) for pressure-sensitive adhesives which is 0 / 100-90 / 10; The pressure-sensitive adhesive composition (X) containing the main ingredient (B) for pressure-sensitive adhesives and 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 adhesive of the present invention has the following effects.
(1) Excellent in adhesiveness (adhesive strength, adhesive residue) when bonded at low temperature (5 ° C).
(2) Excellent in adhesiveness (adhesive strength, adhesive residue) when bonded at high temperature (40 ° C.).
(3) In addition to the above, deterioration of a metal (oxide) film, especially an ITO (indium tin oxide) film can be suppressed.

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

<(Meth) acrylate having hydroxyl group (a2)>
Examples of the (meth) acrylate (a2) having a hydroxyl group include, for example, (meth) acrylate (a21) having a primary hydroxyl group, (meth) acrylate (a22) having a secondary hydroxyl group, and primary other than the above (a1). Examples thereof include (meth) acrylate (a23) having a hydroxyl group and a secondary hydroxyl group.
In addition, (meth) acrylate means a methacrylate and / or an 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 the (a23) include glycerin mono (meth) acrylate.

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

<(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.
The constituent monomer may be abbreviated as a monomer.

  Examples of the constituent monomer (monomer) other than (a1) and (a2) include a monomer (a3) having a carboxyl group and another monomer (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, or acid anhydrides thereof. Mention may be made of monoalkyl esters of polybasic acids. Among these, preferred are acrylic acid, methacrylic acid, maleic anhydride and itaconic acid.
Of the above (a3), acrylic acid is preferred from the viewpoint of tackiness.

Examples of the other monomer (a4) include vinyl ester [vinyl acetate, vinyl propionate, vinyl butyrate, etc.], (meth) acrylate [methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate. , Neopentylmethacrylate, n-octylmethacrylate, nonyl (meth) acrylate, 2-ethylhexylmethacrylate, decyl (meth) acrylate, lauryl (meth) acrylate and the like].
Of the above (a4), vinyl acetate is preferable from the viewpoint of tackiness.

The (co) polymer (A) in the present invention is a known polymerization initiator (azobisisobutyronitrile) obtained by polymerizing the above-mentioned monomer by a known polymerization method (bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, etc.). , Azobisisovaleronitrile and other azo polymerization initiators; benzoyl peroxide, di-t-butyl peroxide, lauryl peroxide and other peroxide polymerization initiators).
Among the above-mentioned polymerization methods, the method of performing solution polymerization in the presence of the solvent (S) (for example, ethyl acetate) is preferable.

  The weight average molecular weight (in terms of polystyrene) of the (co) polymer (A) measured by gel permeation chromatography (GPC) is preferably 100,000 to 600,000, more preferably 150 from the viewpoint of tackiness and handling. 1,000 to 500,000, particularly preferably 200,000 to 400,000.

The measurement conditions of the gel permeation chromatography (GPC) in the present invention are as follows.
Device: "HLC-8120GPC" [manufactured by Tosoh Corporation]
Column: "Guardcolumn HXL-H" (1),
"TSKgel GMHXL" (2) [all manufactured by Tosoh Corporation]
Sample solution: 0.25 wt% tetrahydrofuran solution Injection volume: 100 μl
Flow rate: 1 ml / min Measuring temperature: 40 ° C
Detector: Refractive index detector Reference substance: Standard polystyrene

  The hydroxyl group concentration of the (co) polymer (A) is 1.0 to 4.0 mol / kg, preferably 1.5 to 3.5 mol / kg, and more preferably 2.0 to 3.0. Mol / kg. If the hydroxyl group concentration is less than 1.0 mol / kg and exceeds 4.0 mol / kg, the balance of tackiness 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 and the secondary hydroxyl group possessed by (A) is 0/100 to 90/10, preferably 10/90 to 70 /. 30 and more preferably 15/85 to 50/50. If the (β) does not satisfy the above range, the balance of tackiness tends to be poor.
The (β) can be obtained, for example, from the spectrum of ¹ H-NMR (nuclear magnetic resonance) spectroscopy.
Further, the hydroxyl group concentration of the above (A) and the above (β) can be adjusted by, for example, the type and weight of the (a2) constituting the (A).

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, especially from the viewpoint of tackiness and suppression of deterioration. 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 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, based on the weight of all monomers constituting (A). % By weight.
Further, (a1) is preferably a monoacrylate, (a2) is preferably a mono (meth) acrylate, and more preferably an alkyl group having 1 to 2 (more preferably 1) hydroxyl groups. 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 agent (B) for pressure-sensitive adhesives of the present invention contains the (co) polymer (A). The base agent (B) for pressure-sensitive adhesive is suitable as a main agent for the pressure-sensitive adhesive composition (X) described below.
In addition to (A) and (C), the (B) may contain, for example, a solvent (S). 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 the polyfunctional (meth) acrylate (C) in the present invention include the following (C1) to (C3).

Bifunctional (meth) acrylate (C1) having one hydroxyl group:
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;

3- to 6-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, ditrimethylolpropane tetra (meth) acrylate;

  Among the above polyfunctional (meth) acrylates (C), from the viewpoints of tackiness and residual adhesiveness, (C2), (C3), a combination of (C2) and (C3), and more preferably (C2). ).

<Adhesive composition (X)>
The pressure-sensitive adhesive composition (X) of the present invention contains a main agent for pressure-sensitive adhesive (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), more preferably (A), based on the total weight of (A) and (C). ) Is 80 to 95% by weight, (C) is preferably 5 to 20% by weight, 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 obtained by mixing, for example, 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), but from the viewpoint of handleability, the solvent (S) is preferably 50% by weight or less, and more preferably based on the weight of (X). It is 5% by weight or less, particularly preferably 1% by weight or less.
In the pressure-sensitive adhesive composition (X) of the present invention, if necessary, a tackifier (N) [terpene resin, rosin resin, etc.], a photopolymerization initiator, as long as the effect of the present invention is not impaired. (D), a plasticizer, a filler, a pigment, an ultraviolet absorber, an antioxidant and the like can be further contained.

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

In the pressure-sensitive adhesive film of the present invention, the pressure-sensitive adhesive composition (X) is directly applied to at least a part of at least one surface of a substrate by using various coating devices, for example, heating and / or active energy rays (UV). , Electron beam, etc.) to cure.
As a preferred use form, as in the examples described later, it is a form in which after heating (hot melt), application and curing with active energy rays. That is, (X) can also be said to be an active energy ray-curable hot melt adhesive composition.

  As the base material (film), films, sheets, foams and flat yarns of various plastics [polyolefin (polyethylene and polypropylene etc.), polyurethane, polyethylene terephthalate, polyvinyl chloride, rayon and polyamide etc.] and paper (Japanese paper and crepe paper etc.) ), A metal plate, a metal foil, a woven fabric, a non-woven fabric, wood, and the like.

  Since 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, it is used for packaging (packaging of frozen foods, binding of vegetables, etc.), for marking. Suitable for various purposes such as automobile moldings, emblems and marks, masking (glass sealing, building curing, etc.), surface protection (painted surface protection, etc.), medical care (sticking plaster, etc.), and office work. can do. Furthermore, since the deterioration of the metal (oxide) film, particularly the ITO (indium tin oxide) film can be suppressed, the metal (oxide) film can be suitably used for protecting electronic substrates.

  Hereinafter, the present invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited thereto. 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 inlet tube was charged with 100 parts of ethyl acetate as a solvent and heated.
Next, 85 parts of n-butyl acrylate (a1-1), 12 parts of 2-hydroxypropyl acrylate (a2-3), and 2-hydroxy-1-methyl were blown into the reaction vessel under solvent reflux. <Monomer blending liquid> containing 3 parts of ethyl (meth) acrylate (a2-2) and 2,2′-azobis (2,4-dimethylvaleronitrile) [hereinafter sometimes abbreviated as V-65. ] 0.15 parts of <initiator solution 1> dissolved in 20 parts of ethyl acetate was continuously added dropwise over 5 hours using a dropping funnel to carry out radical polymerization.
After completion of the dropping, <initiator solution 2> prepared by dissolving 0.11 part of 2,2′-azobis (2,4-dimethylvaleronitrile) in 10 parts of ethyl acetate while stirring the system at the same temperature was added to the dropping funnel. It was added continuously over 1 hour. Further, after the polymerization was continued for 1 hour under the reflux of the solvent, it was heated to 130 ° C. under reduced pressure to distill off the ethyl acetate and to contain the (co) polymer (A-1) as the main agent for pressure-sensitive adhesive. (B-1) was taken out.
The weight average molecular weight (Mw) of the (co) polymer (A) was 300,000, the hydroxyl group concentration was 1.2 mol / kg, the molar ratio (β) was 20/80, and the carboxyl group concentration was 0 mol / kg. there were.

<Examples 2 to 9 and Comparative Example 1>
In Example 1, except that in accordance with Table 1, the same procedure as in Example 1 was carried out to obtain a main agent (B) for each pressure-sensitive adhesive containing each (co) polymer (A). The results are shown in Table 1.

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

<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 x width 25 mm] cut out from the adhesive film obtained above A PET film having an ITO layer [thickness: 0.18 mm, the same applies hereinafter] was laminated in a 5 kg atmosphere with one reciprocation of a 2 kg roller to obtain a laminated film.
After pasting, it is left for 1 day under the condition of 60 ° C. × 90% relative humidity, 180 ° peel strength at 25 ° C. is measured (25 mm width, pulling speed 300 mm / min), and the following criteria are used. evaluated.
<Evaluation criteria>
⊚: Greater than 9 N / 25 mm ◯: Greater than 7 N / 25 mm and 9 N / 25 mm or less Δ: Greater than 5 N / 25 mm and 7 N / 25 mm or less ×: 5 N / 25 mm or less

<2> Change in adhesive strength at low temperature After laminating the laminated films obtained in <1> above, the mixture was left standing for 14 days under the conditions of 5 ° C. × 90% relative humidity and peeled off at 180 ° at 25 ° C. The strength was measured (25 mm width, tensile speed 300 mm / min), and the difference from the peel strength in <1> was calculated by the following formula,
It evaluated by the following evaluation criteria.
Change in adhesive strength at low temperature = Peeling strength after 14 days-Peeling strength after 1 day <Evaluation criteria>
◎: Greater than 1N / 25mm, 2N / 25mm or less ○: Greater than 0.5N / 25mm, 1N / 25mm or less △: Greater than 0N / 25mm, 0.5N / 25mm or less ×: 0N / 25mm or less

<3> Low-temperature adhesive residue The surface of the PET film having the ITO layer after 14 days obtained in <2> above was visually evaluated for the presence of adhesive residue based on the following criteria.
<Evaluation criteria>
⊚: No glue residue ○: Almost no glue residue △: Slight glue residue ×: 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 <2> above was measured, the resistance change rate (%) was calculated by the following formula, and evaluated according to the following evaluation criteria. .. Note that R ₀ represents the resistance value (Ω) before the bonding.
Resistance change rate (%) = (R ₅ −R ₀ ) / R ₀ × 100
<Evaluation criteria>
◎: Change rate less than 5% ◯: Change rate 5% or more, less than 10% △: Change rate 10% or more, less than 20% ×: Change rate 20% or more

<5> Adhesive strength at high temperature Using an adhesive film test piece [vertical 100 mm × horizontal 25 mm] cut out from the adhesive film obtained above, based on JIS Z0237-2000 “Adhesive tape, adhesive sheet test method” The PET film having the ITO layer was attached in one atmosphere with a 2 kg roller in an atmosphere of 40 ° C.
After pasting, it is left for 1 day under the condition of 60 ° C. × 90% relative humidity, 180 ° peel strength at 25 ° C. is measured (25 mm width, pulling speed 300 mm / min), and the following criteria are used. evaluated.
<Evaluation criteria>
⊚: Greater than 9 N / 25 mm ◯: Greater than 7 N / 25 mm and 9 N / 25 mm or less Δ: Greater than 5 N / 25 mm and 7 N / 25 mm or less ×: 5 N / 25 mm or less

<6> Change in adhesive strength at high temperature After laminating the laminated films obtained in <5> above, the mixture was left standing for 14 days under the conditions of 60 ° C x 90% relative humidity and peeled off at 180 ° at 25 ° C. The strength was measured (25 mm width, tensile speed 300 mm / min), and the difference from the peel strength at <5> was calculated by the following formula,
It evaluated by the following evaluation criteria.
Change in adhesive strength at low temperature = Peeling strength after 14 days-Peeling strength after 1 day <Evaluation criteria>
◎: Greater than 1N / 25mm, 2N / 25mm or less ○: Greater than 0.5N / 25mm, 1N / 25mm or less △: Greater than 0N / 25mm, 0.5N / 25mm or less ×: 0N / 25mm or less

<7> High-temperature non-stick residue 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 non-stick residue according to the following criteria.
<Evaluation criteria>
⊚: No glue residue ○: Almost no glue residue △: Slight glue residue ×: 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 <6> above was measured, the resistance change rate (%) was calculated by the following formula, and evaluated according to the following evaluation criteria. .. Note that R ₀ represents the resistance value (Ω) before the bonding.
Resistance change rate (%) = (R ₄₀ −R ₀ ) / R ₀ × 100
<Evaluation criteria>
◎: Change rate less than 5% ◯: Change rate 5% or more, less than 10% △: Change rate 10% or more, less than 20% ×: Change rate 20% or more

The components used in Table 2 are as follows.
Polyfunctional (meth) acrylate (C-1): Dipentaerythritol pentaacrylate Polyfunctional (meth) acrylate (C-2): Pentaerythritol tetraacrylate Polyfunctional (meth) acrylate (C-3): Pentaerythritol triacrylate Functional (meth) acrylate (C-4): Glycerin dimethacrylate photopolymerization initiator (D-1): BASF, Irgacure 184, 1-hydroxycyclohexyl phenyl ketone

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

  Since 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, it is used for packaging (packaging of frozen foods, binding of vegetables, etc.), for marking. Suitable for various purposes such as automobile moldings, emblems and marks, masking (glass sealing, building curing, etc.), surface protection (painted surface protection, etc.), medical care (sticking plaster, etc.), and office work. can do. Furthermore, it is extremely useful because it can suppress the deterioration of a metal (oxide) film, especially an ITO (indium tin oxide) film, and can be suitably used for protecting electronic substrates.

Claims (5)

  An alkyl (alkyl group having 4 to 8 carbon atoms) acrylate (a1) and a hydroxyl group-containing (meth) acrylate (a2) as a constituent monomer (co) polymer (A). The hydroxyl group concentration of A) is 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. The base agent (B) for pressure-sensitive adhesive, which is 90/10.   The base agent for pressure-sensitive adhesives according to claim 1, wherein the carboxyl group concentration of the (co) polymer (A) is 0 to 0.35 mol / kg.   A pressure-sensitive adhesive composition (X) comprising the main agent (B) for pressure-sensitive adhesive according to claim 1 or 2, and a polyfunctional (meth) acrylate (C).   The pressure-sensitive adhesive composition according to claim 3, 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 claim 3 or 4.