JPH07278512A - Acrylic tacky agent composition - Google Patents

Abstract

PURPOSE:To obtain a composition, comprising a specific acrylic copolymer, a specified tackifying resin and a cross-linking agent, having a high bonding strength even to an adherend surface having an uneven surface such as a synthetic resin foam as well as a (non)polar adherend surface and excellent even in cohesive force. CONSTITUTION:This composition comprises (A) an acrylic copolymer composed of (i) preferably 75-95wt.% alkyl (meth)acrylate and (ii) preferably 0.05-1.0wt.% vinyl monomer, etc., having OH group and composed of 2-hydroxyethyl (meth) acrylate, a caprolactone-modified (meth)acrylate, etc., [preferab1y having 200000-1500000 weight-average molecular weight (Mw) at 2.0-4.0 ratio (Mw/Mn) of the Mw to the number-average molecular weight (Mn)], (B) a tackifying resin preferably composed of glycerol and pentaerythritol (preferably 1.5-6.0 hydroxyl group index and 4.5-6.5 softening point index) and (C) a cross-linking agent cross-linkable with the OH group such tolylene diisocyanate, hexamethylene diisocyanate or a tolylene diisocyanate adduct to trimethylolpropane.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an acrylic pressure-sensitive adhesive composition.

[0002]

2. Description of the Related Art In recent years, an acrylic adhesive has been developed as an adhesive having excellent weather resistance and solvent resistance as compared with a rubber adhesive, and has been used for various purposes. The agent has the drawback of poor adhesion at low temperatures.

As a method for solving the above-mentioned problems, an acrylic pressure-sensitive adhesive composition using an esterified product of a resin acid having a specific hydroxyl value as a tackifying resin has been reported (JP-A-3-281587). .

[0004]

However, although the above-mentioned acrylic pressure-sensitive adhesives have improved low-temperature adhesiveness, they have the adhesiveness to synthetic resin foams such as urethane foam and polyethylene foam, and cohesive strength. So it was not always satisfactory.

The present invention has been made in view of the above problems, and it is an object of the present invention to achieve high adhesion not only to polar and non-polar adherend surfaces but also to adherend surfaces having an uneven surface such as synthetic resin foam. It is intended to provide an acrylic pressure-sensitive adhesive composition having strength and excellent performance in cohesion.

[0006]

The acrylic pressure-sensitive adhesive composition of the present invention comprises an acrylic copolymer, a tackifying resin, and a crosslinking agent capable of undergoing a crosslinking reaction with a hydroxyl group.

The acrylic copolymer comprises an alkyl (meth) acrylate and a vinyl monomer having a hydroxyl group, and the alkyl group of the alkyl (meth) acrylate preferably has 2 to 14 carbon atoms, more preferably 4 to 4 carbon atoms.
It is 9.

Examples of the alkyl (meth) acrylate include ethyl acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate and t-butyl (meth). ) Acrylate, n-octyl (meth) acrylate, isooctyl acrylate, 2-ethylhexyl (meth) acrylate, isononyl acrylate, lauryl (meth) acrylate, and the like, and one or more may be used in combination.

The amount of the alkyl (meth) acrylate compounded in the acrylic copolymer is 70 to 99.
It is preferably 5% by weight, more preferably 75 to 95% by weight. 70
If it is less than 10% by weight, the cohesive force of the pressure-sensitive adhesive after compounding the tackifying resin described below becomes too high, and the pressure-sensitive adhesive force decreases. Further, if it exceeds 99.5% by weight, it becomes difficult to obtain the necessary cohesive force.

As the vinyl monomer having a hydroxyl group, 2-hydroxyethyl (meth) acrylate, 2-
Examples thereof include hydroxypropyl (meth) acrylate, 4-hydroxy (meth) butyl acrylate, caprolactone-modified (meth) acrylate, polyoxyethylene oxide-modified (meth) acrylate and the like.

The blending amount of the vinyl monomer having a hydroxyl group in the acrylic copolymer is 0.05 to 1.0.
Weight percent is preferred. If it is less than 0.05% by weight, it becomes difficult to obtain the cohesive force, and if it exceeds 1.0% by weight, the cohesive force becomes too high and it becomes difficult to obtain the adhesiveness to the uneven surface.

In addition to the above monomers, if necessary, a carboxyl group-containing vinyl monomer such as (meth) acrylic acid, itaconic acid, maleic acid (anhydrous), fumaric acid (anhydrous), (meth) acrylonitrile, N-vinyl. Vinyl monomers having a high polar group such as pyrrolidone, N-vinylcaprolactam, acryloylmorpholine, (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropylacrylamide, methyl (meth) acrylate A copolymerizable vinyl monomer such as styrene or vinyl acetate may be used in combination.

The blending amount of the vinyl monomer in the acrylic copolymer is preferably 0.5 to 30% by weight. If less than 0.5% by weight, it becomes difficult to obtain cohesive force,
When the content is more than wt%, the cohesive force becomes too high and it becomes difficult to obtain adhesiveness to the uneven surface.

The acrylic copolymer can be obtained by adding a polymerization initiator to the vinyl monomer by a method such as solution polymerization, bulk polymerization, suspension polymerization or photopolymerization. The solution polymerization is preferable from the viewpoints that the viscosity can be adjusted and the tackifying resin can be uniformly mixed. Examples of the polymerization initiator for the solution polymerization include azoisobutyronitrile and benzoyl peroxide.

The weight average molecular weight of the acrylic copolymer is 20 to 1,500,000. More preferably 35 to 7
It is 50,000. If it is less than 200,000, it becomes difficult to obtain the necessary cohesive force, and if it exceeds 1.5 million, the viscosity becomes high and the productivity in the mixing with the tackifying resin and the coating process deteriorates.

Further, the weight average of the above acrylic copolymer
Molecular weight (M_w) And number average molecular weight (M _n) Ratio (M_w/ M
_n), That is, the molecular weight distribution is 2.0 to 4.0,
The most preferable range is 2.0 to 3.5.
If it exceeds 4.0, the balance between cohesive strength and adhesive strength becomes poor.
And it is practically difficult to produce a polymer of less than 2.0
Is.

The tackifying resin used in the present invention has a hydroxyl group index (I) of 1.5 to 6.0. The hydroxyl group index is the sum of the products of the hydroxyl value of each tackifying resin and the weight fraction of the tackifying resin (% by weight of each tackifying resin relative to the total amount of acrylic copolymer and tackifying resin). It is shown and is a parameter showing the concentration of hydroxyl groups of the tackifying resin present in the pressure-sensitive adhesive system. The hydroxyl group index (I) can be calculated by the following formula, and the hydroxyl group value can be measured according to JIS-K0070. Hydroxyl Index (I) = Σ (OHV _i × W _i ) (1) [OHV _i : hydroxyl value of i-th component, W _i : weight fraction of i-th component] When the above-mentioned hydroxyl index is less than 1.5 Has poor adhesion to the uneven surface, and if it exceeds 6.0, the necessary cohesive force cannot be obtained.

The tackifying resin used in the present invention has a softening point index (II) of 4.5 to 6.5. When the softening point index is less than 4.5, the adhesiveness to the polyolefin becomes low, and when it exceeds 6.5, the adhesiveness to the uneven surface and the adhesive strength at low temperature are lowered.

The softening point index (II) is the sum of the quotient of the weight fraction of each tackifying resin (% by weight of each tackifying resin with respect to the total amount of acrylic copolymer and tackifying resin) and the softening point. Is a value obtained by multiplying by 10000 times, and is a parameter showing the cohesive strength level of the entire pressure-sensitive adhesive. The softening point index can be represented by the following formula, and can be determined according to the formula for determining the glass transition point of a polymer mixed system, and correlates with the glass transition temperature of the entire pressure-sensitive adhesive (J.E. NIE
LSEN, translated by Shigeharu Onoki: “Mechanical properties of polymers and composites”, p. 16). Softening point index (II) = Σ (W _i / Sp _i ) × 10 ⁴ (2) [Sp _i : softening point of i-th component, W _i : weight fraction of i-th component]

The tackifying resin has a hydroxyl group, and is mainly an esterified product of a rosin compound. Examples of the rosin-based compound include a rosin monomer, a rosin dimer, a disproportionated rosin, a hydrogenated rosin and a mixture thereof, and an esterified product of the rosin-based compound is an esterified product of the rosin-based compound and a polyhydric alcohol. Can be mentioned. As the polyhydric alcohol,
Examples thereof include diethylene glycol, glycerin and pentaerythritol, and more preferred are glycerin and pentaerythritol.

In addition, C containing no hydroxyl group
Examples thereof include petroleum resins such as 5 series (aliphatic series) and C9 series (aromatic series), terpene resins, xylene resins, styrene series resins, modified phenol compounds thereof, and the above rosin compounds that are not esterified.

In the pressure-sensitive adhesive composition of the present invention, the above tackifying resins may be optionally used in combination so that the values of hydroxyl group index (I) and softening point index (II) fall within the above ranges.

The pressure-sensitive adhesive composition of the present invention uses a crosslinking agent capable of reacting with a hydroxyl group. Examples of the cross-linking agent include tolylene diisocyanate (TDI), tolidine diisocyanate (TODI), xylylene diisocyanate,
Aromatic diisocyanate compounds such as diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI), aliphatic or alicyclic diisocyanate compounds such as isophorone diisocyanate (IDI), trimethylolpropane tolylene diisocyanate trimer adduct, triphenyl Triisocyanate compounds such as methanetriisocyanate and methylenebis (4-phenylmethane) triisocyanate can be mentioned.

Further, ethylene glycol diglycidyl ether, triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diglycidylamine, N, N, N ', N'- Epoxy compounds such as tetraglycidyl m-xylenediamine and 1,3-bis (N, N′-diglycidylaminomethyl) cyclohexane may be mentioned.

Further, alkoxysilane compounds such as trimethoxysilane, triethoxysilane and tributoxysilane can be mentioned.

The amount of the crosslinking agent added is preferably 0.02 to 2 parts by weight with respect to 100 parts by weight of the acrylic polymer.

Additives such as plasticizers, softeners, fillers, pigments and dyes may be added to the pressure-sensitive adhesive composition of the present invention, if necessary.

A pressure-sensitive adhesive tape is obtained by applying the pressure-sensitive adhesive composition of the present invention to one or both sides of a substrate to form a pressure-sensitive adhesive layer. As the substrate, paper, nonwoven fabric, synthetic resin film such as polyester resin and polyolefin resin, synthetic resin foam such as polyolefin resin, polyurethane resin, polychloroprene resin and acrylic resin can be used. Further, a so-called non-support type double-sided pressure-sensitive adhesive tape having no substrate layer can be obtained by molding only the pressure-sensitive adhesive itself into a sheet.

[0029]

The acrylic pressure-sensitive adhesive composition of the present invention comprises a combination of an acrylic copolymer having a specific composition with a limited molecular weight and molecular weight distribution, and a tackifying resin having a hydroxyl group index and a softening index in a limited range. Thus, the adhesive strength at room temperature and the adhesiveness to non-polarity such as polyolefin can be secured, and the adhesiveness to the uneven surface is also excellent. further,
Since it has a high cohesive force, it is also excellent in high-temperature holding power.

[0030]

EXAMPLES Examples of the present invention will be described below.
In the following, "parts" means "parts by weight". (Preparation of Acrylic Copolymers 1 to 8) According to the blending composition shown in Table 1, isononyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, ethyl acrylate, ethyl acrylate, 2-hydroxyethyl. Methacrylate, 2-hydroxyethyl acrylate, acrylic acid,
N-vinylcaprolactam, vinyl acetate and lauryl mercaptan were charged together with 80 parts of ethyl acetate in a five-necked flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas inlet, and dissolved by stirring to homogeneity. After forming the mixture, it was purged with nitrogen gas for about 30 minutes to remove oxygen present in the monomer solution.

Then, the air in the flask was replaced with nitrogen gas, the temperature was raised with stirring, and the temperature was maintained at 70 ° C. to prepare a solution prepared by dissolving 0.03 part of benzoyl peroxide in 1 part of ethyl acetate. After dropping with a dropping funnel, a polymerization reaction was performed at the same temperature for 10 hours to obtain a solution of a hydroxyl group-containing acrylic copolymer.

(Measurement of Molecular Weight of Acrylic Copolymer) The weight average molecular weight and the number average molecular weight of the acrylic copolymer solution obtained with each of the above-mentioned composition were measured. The above molecular weight is determined by gel permeation chromatography.
Standard polystyrene was used as a reference, tetrahydrofuran was used as an eluent, and detection was performed using a refraction system. The results are also shown in Table 1.

[0033]

[Table 1]

(Preparation of Acrylic Adhesive Composition) Table 2,
According to the blending composition (1 to 16) shown in 3, the acrylic polymers A to G and various tackifying resins were uniformly mixed while being diluted with toluene to obtain a 45% by weight solution of the pressure sensitive adhesive composition.

The details of each component in Tables 2 and 3 are as follows. In the following, "OHV" means hydroxyl value and "S
“P” represents the softening point (absolute temperature). Tackifying resin 1: esterified product of hydrogenated rosin with pentaerythritol,
Arakawa Chemical Industry Co., Ltd., trade name "Ester gum HP" (OH
V = 56.0, Sp = 368).

Tackifying resin 2: Esterified product of disproportionated rosin by glycerin ester, manufactured by Arakawa Chemical Co., Ltd., trade name "Super Ester A100" (OHV = 10.
1, Sp = 373).

Tackifying resin 3: C9 petroleum resin, manufactured by Mitsubishi Oil Co., Ltd., trade name "Oligotech 1400" (OHV =
0, Sp = 393).

Tackifying resin 4: C5 petroleum resin, manufactured by Mitsui Petrochemical Co., Ltd., trade name "FTR6100" (OHV = 0,
Sp = 373).

Tackifying resin 5: Disproportionated rosin esterified with a mixture of glycerin and pentaerythritol: Arakawa Chemical Co., Ltd., trade name "Super Ester A115" (OHV = 20.8, Sp = 38).
8).

Tackifying resin 6: Esterified product of disproportionated rosin with pentaerythritol, manufactured by Arakawa Chemical Industry Co., Ltd.
Product name “Super Ester A125” (OHV = 10.
4, Sp = 398).

Tackifying resin 7: A mixture of rosin monomer and polymerized rosin, manufactured by Arakawa Chemical Industry Co., Ltd., trade name "Silva Tac 140" (OHV = 0, Sp = 413).

Tackifying resin 8: A mixture of a rosin monomer and a polymerized rosin, which is esterified with a mixture of pentaerythritol and glycerin, manufactured by Arakawa Chemical Industry Co., Ltd. under the trade name "Pencel D160" (OHV = 41.
0, Sp = 433).

Further, the hydroxyl group index and the softening index of each pressure-sensitive adhesive composition according to the above blending composition (1-16) are shown in Tables 2 and 3.
It was shown to.

[0044]

[Table 2]

[0045]

[Table 3]

(Preparation of Adhesive Tape) The above composition (1 to
To the solution of each adhesive composition of 16), 2.4 parts of ethyl acetate solution of trimethylolpropane tolylene diisocyanate adduct (trade name "Coronate L55E, manufactured by Nippon Polyurethane Industry Co., Ltd., solid content 55% by weight) is added. After uniformly mixing (based on 100 parts of the acrylic polymer) and coating and drying on a release sheet, a laminate having a pressure-sensitive adhesive layer having a thickness of 65 μm was obtained. After the transfer coating was carried out by laminating on both sides of the m ² non-woven fabric, it was cured at 40 ° C. for 3 days to obtain a double-sided adhesive tape.

(Evaluation method of adhesive tape) (Evaluation of SP adhesive strength)
According to Z0237, it is stuck on a SUS304 plate with a width of 20 mm, left at 23 ° C. for 20 minutes, and then rotated in a 180 ° direction.
The peel strength was measured under the conditions of a pulling speed of 300 min / min.

(Evaluation of Adhesive Strength of Polypropylene) The above double-sided adhesive tape was attached to a polypropylene plate with a width of 20 mm, left at 23 ° C. for 20 minutes, and then 180 ° C. at room temperature.
The peel strength was measured under the conditions of the degree direction and the pulling speed of 300 min / min.

(Evaluation of Holding Power) The double-sided adhesive tape (2
S) on both sides of the product (cut to a size of 0 x 20 mm)
US304 plates were laminated to form a laminate and left at 23 ° C. for 20 minutes. The above-mentioned laminated body was left at a temperature of 80 ° C. for 20 minutes, a load of 1 kg was applied in the displacement direction, and the displacement length (or drop time) after 1 hour was measured.

(Adhesiveness on uneven surface) One side of the double-sided pressure-sensitive adhesive tape was backed with a 38 μm polyester film to prepare a single-sided pressure-sensitive adhesive tape sample having a width of 20 mm. Width 25 mm, length 120 mm, thickness 10 m
The surface of the urethane foam sheet with a density of 0.05 g / cm ³ cut into m was attached and pressure-bonded (until the urethane foam was compressed to 1/2 thickness) with a 500 g roller in an atmosphere of 5 ° C. 5 The peeling force from the concavo-convex surface was measured under the conditions of a temperature of 180 ° C. and a pulling speed of 300 min / min in an atmosphere of 180 ° C. The evaluation results are shown in Tables 4 and 5.

[0051]

[Table 4]

[0052]

[Table 5]

[0053]

EFFECTS OF THE INVENTION The pressure-sensitive adhesive composition of the present invention is prepared by combining an acrylic copolymer having a specific molecular weight and a molecular weight distribution with a rosin derivative having a specific hydroxyl group concentration and a specific softening point to obtain a polar composition. It has a high adhesive force not only on a high adherend surface but also on a low-polarity adherend surface. Furthermore, the cohesive force at high temperature and the comparatively high adhesiveness to uneven surfaces such as resin foams provide the above-mentioned properties in a well-balanced manner.
Therefore, the pressure-sensitive adhesive composition of the present invention can be suitably used for pressure-sensitive adhesive tapes and double-sided pressure-sensitive adhesive tapes for various applications.

Claims (1)

[Claims] 1. An acrylic pressure-sensitive adhesive composition comprising an acrylic copolymer comprising an alkyl (meth) acrylate and a vinyl monomer having a hydroxyl group, a tackifier resin, and a crosslinking agent capable of undergoing a crosslinking reaction with the hydroxyl group, wherein the acrylic copolymer The weight average molecular weight of the polymer is 20 to 15
In 00000, and a ratio of weight average molecular weight (M _w) and number average molecular weight _{(M n) (M w /} M n) is 2.0 to 4.0,
The acrylic pressure-sensitive adhesive composition, wherein the tackifying resin has a hydroxyl group index (I) of 1.5 to 6.0 and a softening point index (II) of 4.5 to 6.5.