JP2000230161A - Adhesive composition and adhesive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acrylic adhesive composition having both good adhesivity to polyolefins and good punching processing suitability, and to obtain an adhesive film. SOLUTION: This acrylic adhesive composition comprises an adhesivity- imparting resin and an acrylic copolymer which consists mainly of a 2-14C (meth)alkyl acrylate and a polar group-containing vinyl monomer. Therein, the maximum stress and the maximum strain are 3-7 kgf/cm2 and 2,000-3,200%, respectively, in a stress-strain curve measured in conditions comprising a temperature of 23 deg.C, a relative humidity of 65% and a pulling rate of 300 mm/min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an acrylic pressure-sensitive adhesive composition and a pressure-sensitive adhesive film (including pressure-sensitive adhesive tapes) having high peel resistance. Specifically, the pressure-sensitive adhesive composition has a stress-
It has a specific maximum stress and a maximum strain in the strain curve, and is excellent in peeling resistance, punching workability, and removability.

[0002]

2. Description of the Related Art Acrylic pressure-sensitive adhesive compositions have excellent adhesive properties such as adhesive strength and cohesive strength and aging resistance properties such as heat resistance and weather resistance, and are widely used. JP-A-10-204399 discloses a pressure-sensitive adhesive composition having excellent adhesive properties from room temperature to high temperature, and particularly having high peeling resistance to low-polarity adherends such as polyolefins. When the stress is 2 to 6 gf / m
m ² , stress at 1000% strain is 10 to 60 gf / mm ²
An acrylic pressure-sensitive adhesive composition characterized by the following is reported. However, in the acrylic pressure-sensitive adhesive composition containing the acrylic copolymer, a cross-linking agent and a tackifying resin, although the high-temperature properties and the pressure-sensitive adhesive properties to polyolefin are improved, these properties and pressure-sensitive adhesive tapes and pressure-sensitive adhesive films are improved. The suitability for punching when punching with a blade die or the like was not always compatible. For example, when processing a conventional pressure-sensitive adhesive tape having good peel resistance, it was necessary to process the tape by cooling or heating the tape.

[0003]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide an acrylic pressure-sensitive adhesive composition and a pressure-sensitive adhesive which have both good adhesion to polyolefin and suitability for punching. An object of the present invention is to provide a tape and an adhesive film. A further challenge is important for label applications,
An object of the present invention is to provide a pressure-sensitive adhesive composition which can be peeled without sticking after application, that is, provided with removability.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a pressure-sensitive adhesive composition containing a specific acrylic copolymer and a tackifying resin and having a maximum stress and a maximum strain value in a specific range. The present inventors have found that the above-mentioned object can be achieved by an adhesive tape and an adhesive film using the same, and have completed the present invention.

[0005] That is, the first structure of the present invention has 2 to 2 carbon atoms.
An acrylic pressure-sensitive adhesive composition containing an acrylic copolymer containing a (meth) alkyl acrylate and a polar group-containing vinyl monomer as essential components, and a tackifying resin, at a temperature of 23 ° C. and a relative humidity of 65%. Tension speed 300
In the stress-strain curve measured under the condition of mm / min,
A maximum stress of ^{3kgf / cm 2 ~7kgf / cm 2} , and the maximum strain is an acrylic pressure-sensitive adhesive composition characterized by from 2,000% ～3200%.

Further, according to the constitution of the present invention, the above-mentioned acrylic copolymer comprises 50% by weight or more of n-butyl acrylate as a (meth) alkyl acrylate having 2 to 14 carbon atoms and acrylic acid as a polar group-containing vinyl monomer. To 0.
5 to 2.5% by weight of a copolymer obtained by copolymerizing 100 parts by weight of the copolymer, 3 to 15 parts by weight of a polymerized rosin pentaerythritol ester and 3 to 15 parts by weight of a disproportionated rosin ester as a tackifying resin. An adhesive composition containing 18 parts by weight and having a gel fraction of 30 to 50%. Further, a second configuration of the present invention is a pressure-sensitive adhesive tape or pressure-sensitive adhesive film characterized in that the above-mentioned pressure-sensitive adhesive composition is applied to at least one surface of a substrate layer.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the stress-strain curve of an acrylic pressure-sensitive adhesive composition is, specifically, formed by forming the acrylic pressure-sensitive adhesive composition into a film, laminating the same, and forming a film having a thickness of 40 mm.
Create a test piece of 0 μm × width 10 mm × length 60 mm,
At the center, a marker line with a marker line distance of 20 mm is attached, one end of which is fixed, and in an atmosphere of a temperature of 23 ° C. and a relative humidity of 65%,
The other end is measured by pulling with a tensile tester such as TENSILON (manufactured by A & D) at a pulling speed of 300 mm / min.

In the stress-strain curve of the acrylic pressure-sensitive adhesive composition measured under such conditions, the maximum stress is 3 k
If it is less than gf / cm ² , the cohesive force is low, and sufficient resistance to peeling at a low speed cannot be obtained.
^If it exceeds ² , the pressure-sensitive adhesive composition is too hard to cut during punching. Here, the maximum stress means the maximum value of the stress shown until the test piece breaks.

When the maximum strain is less than 2000%, the fluidity is low, the deformation energy obtained by deformation is low, and sufficient peeling resistance cannot be obtained.
%, The fluidity becomes too high, and the pressure-sensitive adhesive composition re-adheres after punching. Here, the maximum strain means the strain when the test piece breaks.

An acrylic pressure-sensitive adhesive composition having such performance can be obtained by appropriately selecting an acrylic copolymer, a crosslinking agent and a tackifying resin.

The main component of the acrylic copolymer used in the present invention is (meth) alkyl acrylate, a polar group-containing monomer for imparting cohesive force to the (meth) alkyl acrylate, and other copolymerizable monomers. A polymer obtained by adding a monomer is used, and is obtained by polymerizing the polymer by a known radical polymerization method such as solution polymerization, emulsion polymerization, or bulk polymerization.

As the (meth) alkyl acrylate as a main component, a (meth) alkyl acrylate having an alkyl group having 2 to 14, preferably 4 to 9 carbon atoms is used. When the number of carbon atoms of the alkyl group is out of the above range, the properties of the pressure-sensitive adhesive composition deteriorate.

Examples of such (meth) alkyl acrylates include ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-octyl acrylate, isooctyl acrylate, Monomers such as -ethylhexyl acrylate, isononyl acrylate, octyl acrylate, and lauryl acrylate. These monomers may be used alone or in combination of two or more.

In particular, n-butyl acrylate is preferable as the (meth) alkyl acrylate in consideration of the balance between the adhesive strength and the cohesive strength of the obtained pressure-sensitive adhesive composition, and 50% by weight in the acrylic copolymer. % Is preferable.

Examples of the copolymerizable polar group-containing vinyl monomer include styrene, vinyl acetate, acrylonitrile, N
-Vinylpyrrolidone, N-vinylcaprolactam, acrylamide, dimethylaminoethylacrylamide, acrylic acid, itaconic acid, carboxypropyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, and the like can be used.

Particularly, the amount of acrylic acid used is preferably 0.5 to 2.5 parts based on 100 parts of the acrylic copolymer.
If it is less than 0.5 part, the adhesive strength is not sufficient, and if it exceeds 2.5 parts, the removability such as adhesive residue on the adherend decreases.

The weight average molecular weight of the acrylic copolymer is as follows:
200,000 to 1.5 million is preferred. If it is too small, the cohesive strength required for the pressure-sensitive adhesive composition cannot be obtained, and if it is too large, the viscosity will increase and the productivity in the coating process will deteriorate. More preferably 40
10,000 to 1 million.

The crosslinking agent used in the present invention is a known polyfunctional compound used for crosslinking the acrylic copolymer to increase the cohesive strength and heat resistance of the pressure-sensitive adhesive composition.

Examples of such polyfunctional compounds include isocyanate compounds such as tolylene diisocyanate and hexamethylene diisoanate, melamine compounds such as methylated trimethylol melamine and butylated hexamethylol melamine, diglycidyl aniline, and glycerin diglycidyl. An epoxy compound such as ether is used.

These crosslinking agents may be used alone.
More than one species may be used in combination. These crosslinking agents are preferably added so that the gel fraction of the pressure-sensitive adhesive composition after crosslinking becomes 30 to 50% by weight. If the gel fraction is less than 30%, the cohesive strength is low, and sufficient peeling resistance, holding power and removability cannot be obtained. Conversely, if the gel fraction exceeds 50%, the deformation energy of the pressure-sensitive adhesive composition , And sufficient peeling resistance cannot be obtained. Here, the gel fraction is obtained by immersing the crosslinked PSA composition in toluene and measuring the weight of the insoluble content remaining after standing for 24 hours after drying, and is expressed as a percentage of the original weight.

The tackifying resin used in the present invention is preferably
Like olefins (polyethylene, polypropylene, etc.)
Adhesion to non-polar adherends with high peel resistance
Used in the stress-strain curve.
And the maximum stress is 3kgf / cm ^Two~ 7kgf / cm^Twoso,
And the maximum distortion satisfies 2000% to 3200%
Rosin or rosin ester
Rosin-based resins such as compounds; diterpene polymers and α-pine
Terpene resins such as phenol-phenol copolymers; aliphatic resins
Petroleum resins such as (C5) and aromatic (C9);
Styrene resin, phenol resin, xylene resin, etc.
No. Preferably polymerized rosin pentaerythritol
Luster.

The amount of the tackifier resin having such properties is preferably 3 to 1 with respect to 100 parts by weight of the acrylic copolymer and rosin pentaerythritol ester.
5 parts by weight and 3 to 18 parts by weight of the disproportionated rosin ester are preferred.

When the amount of the polymerized rosin pentaerythritol ester is less than 3 parts by weight, sufficient peeling resistance cannot be obtained. On the contrary, when the amount of the polymerized rosin pentaerythritol ester exceeds 15 parts by weight, the workability and removability are reduced. Since the polymer rosin pentaerythritol ester alone has insufficient tackiness, a disproportionated rosin ester is added. When the disproportionated rosin ester is less than 3 parts by weight, sufficient tackiness cannot be obtained. Conversely, when the disproportionated rosin ester exceeds 18 parts by weight, the tackiness is reduced.

Further, the acrylic pressure-sensitive adhesive composition of the present invention comprises:
Known additives such as plasticizers, softeners, fillers, and pigments may be added as needed within a range that satisfies the maximum stress and strain specified in the present invention.

Such an acrylic pressure-sensitive adhesive composition is applied to at least one surface of a substrate layer and used as a pressure-sensitive adhesive tape or film. As the base material, a nonwoven fabric, a synthetic resin film such as polyester or polyolefin, or a synthetic resin foam such as polyolefin, polyurethane, or acrylic resin is used. Further, the acrylic pressure-sensitive adhesive composition itself can be formed on a release sheet to form a double-sided pressure-sensitive adhesive tape without a substrate.

[0026]

EXAMPLES Examples of the present invention and comparative examples will be described below in more detail.

[Synthesis of Acrylic Copolymer] In accordance with the composition shown in Table 1, n-butyl acrylate, 2-butyl acrylate was added to a reaction vessel equipped with a stirrer, a dry distillation cooler, a thermometer, a dropping funnel and a nitrogen gas inlet. Ethylhexyl acrylate, vinyl acetate, acrylic acid, β-hydroxyethyl acrylate and 0.2 part of 2,2′-azobisisobutyronitrile as a polymerization initiator were dissolved in 100 parts of ethyl acetate, and the solution was dissolved at 80 ° C.
For 8 hours to synthesize acrylic copolymers A, B, C and D.

[Preparation of acrylic pressure-sensitive adhesive composition] According to the composition shown in Table 2, the above acrylic copolymer A,
The tackifier resin was added to B, C, and D, and diluted and mixed with toluene to prepare a pressure-sensitive adhesive composition solution having a solid content of 45%. Here, superester A1 is used as the disproportionated rosin ester.
00 (manufactured by Arakawa Chemical Co., Ltd.), and as a polymerized rosin pentaerythritol ester, Pencel D135 (manufactured by Arakawa Chemical Co., Ltd.)
Was used.

[Preparation of Tape] To 100 parts of this pressure-sensitive adhesive composition solution was added an isocyanate-based crosslinking agent (NC40).
Was added as shown in Table 2, and the mixture was stirred for 15 minutes, coated on a synthetic paper having a thickness of 80 μm so that the pressure-sensitive adhesive thickness after drying was 20 μm, and dried at 80 ° C. for 3 minutes. A 75 μm-thick polyester film that had been subjected to a release treatment was laminated on the obtained adhesive film. Thereafter, the mixture was aged at 40 ° C. for 2 days to obtain an adhesive film.

[0030]

[Table 1]

[0031]

[Table 2]

The obtained pressure-sensitive adhesive films were tested by the following methods, and the evaluation results are shown in Tables 3 and 4.

<Punching property> The obtained pressure-sensitive adhesive film was formed into a roll sample having a width of 200 mm, and was subjected to a half-cut processing of 1,000 shots by a punching machine. The debris removability of the obtained label was observed. ◎: Debris can be removed without any problem.

<Peeling Resistance> 20 mm width × 10 at 23 ° C.
An adhesive film having a length of 0 mm is adhered to a polypropylene plate, pressed back and forth with a 2 kg roller eight times, and left at 40 ° C. for 1 hour. Next, it is left at 23 ° C. for 15 minutes, and a load of 100 g is applied to one end of the adhesive film to be peeled in a 90 ° direction. And the time until 50 mm peeling was measured. ◎: Does not drop for more than 1000 minutes ○: Does not drop for more than 500 minutes ×: Drops within 500 minutes

<Stress-Strain Curve of Pressure-Sensitive Adhesive Composition> The pressure-sensitive adhesive composition after crosslinking is laminated to a thickness of about 400 μm and cut into a length of 60 mm and a width of 10 mm. Grasp both ends and fix them to Tensilon at a spacing of 20 mm.
The sample was pulled at a rate of mm / min, and the maximum stress and the maximum strain were measured until the pressure-sensitive adhesive composition was broken.

<Gel Fraction> The pressure-sensitive adhesive composition after cross-linking was immersed in toluene, and the weight of the insoluble portion remaining after standing for 24 hours was measured and expressed as a percentage of the original weight.

<Removability> 25 mm width × 10 at 23 ° C.
An adhesive film having a length of 0 mm is attached to a polypropylene plate and a stainless plate, and left for 30 minutes. The adhesive film is peeled at a rate of 5 mm / min in the 180-degree direction, and the adhesive residue on the adherend is observed. ◎: No glue residue ○: Some glue residue ×: Full glue residue

<PP adhesive strength> 25 mm width x 1 at 23 ° C
A pressure-sensitive adhesive film having a length of 00 mm is attached to a polypropylene plate, pressed once with a 2 kg roller, and left for 30 minutes. 300mm / m in 180 degree direction
Peel in and measure the adhesion.

<Stainless steel holding power> 25 mm at 23 ° C.
An adhesive film with a width of 100 mm and a length of 2 mm
It is stuck so as to have an area of 5 mm x 25 mm, and after one reciprocating pressure with a 2 kg roller, it is left for 30 minutes. A 1 kg load was applied to the adhesive film in an atmosphere of 70 ° C., and the time until the tape dropped was measured. When it did not fall for more than 24 hours, it was described as "24 <".

[0040]

[Table 3]

[0041]

[Table 4]

[0042]

According to the pressure-sensitive adhesive composition and the pressure-sensitive adhesive film of the present invention, since the pressure-sensitive adhesive composition has a specific maximum stress and a specific maximum strain, peeling resistance and punching suitability can both be achieved.
Further, since the pressure-sensitive adhesive composition of this formulation is a specific composition,
It can be peeled off without sticking after application and does not impair the appearance.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4J004 AA04 AA07 AA10 AA12 AA15 AB01 BA02 CA04 CA06 CB01 CB04 CC02 DB03 EA05 4J040 BA202 DF041 DF051 EC032 EC122 EF181 GA05 GA07 GA13 GA14 GA15 GA17 GA22 HC16 HC25 JA16 JB09 LA06

Claims (3)

[Claims] 1. An acrylic pressure-sensitive adhesive composition comprising a (meth) alkyl acrylate having 2 to 14 carbon atoms and a polar group-containing vinyl monomer as essential components, and a tackifier resin. In a stress-strain curve measured at a temperature of 23 ° C., a relative humidity of 65%, and a tensile speed of 300 mm / min, the maximum stress is 3 kgf / cm ² to
7 kgf / cm ² and maximum strain of 2000% to 32
An acrylic pressure-sensitive adhesive composition characterized in that the content is 00%. 2. The acrylic copolymer contains 50% by weight or more of n-butyl acrylate as a (meth) alkyl acrylate having 2 to 14 carbon atoms, and 0.5 part by weight of acrylic acid as a polar group-containing vinyl monomer. A copolymer obtained by copolymerizing 2.5% by weight of the copolymer, 100 parts by weight of the copolymer, 3 to 15 parts by weight of a polymerized rosin pentaerythritol ester and a disproportionated rosin ester 3 as a tackifying resin.
The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition contains -18 to 18 parts by weight, and has a gel fraction of 30 to 50%. 3. A pressure-sensitive adhesive film, wherein the pressure-sensitive adhesive composition according to claim 1 or 2 is applied on at least one surface of a substrate layer.