JP3411065B2 - Acrylic pressure-sensitive adhesive composition and double-sided tape - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic pressure-sensitive adhesive composition and a double-sided tape using the pressure-sensitive adhesive composition. In particular, the present invention relates to an acrylic pressure-sensitive adhesive composition having excellent peel resistance and a double-sided tape using the pressure-sensitive adhesive composition.

[0002]

2. Description of the Related Art In recent years, pressure-sensitive adhesive (hereinafter referred to as "adhesive") compositions have been used for a wider range of applications, and the properties required therefor have tended to become more sophisticated. An acrylic pressure-sensitive adhesive has been developed as a pressure-sensitive adhesive having high cohesive strength and excellent in weather resistance and solvent resistance, and is used for various purposes.

An acrylic copolymer has a tackiness by itself and can be used as an adhesive without adding a tackifying resin. However, it is not suitable for an adherend having a low polarity surface such as polyethylene or polypropylene. However, it was difficult to exhibit good adhesive properties by itself. In particular, if the copolymerization amount of the carboxyl group-containing monomer in the acrylic copolymer is increased for the purpose of improving the adhesive property to a polar surface of a metal plate or the like, the adhesive force to polyethylene or polypropylene is practically unacceptable. It is recognized that it will be lowered. Therefore, the tackifying resin is usually added in the same manner as in other pressure-sensitive adhesives to improve the low-polar adhesion force.

[0004]

However, the pressure-sensitive adhesive obtained by adding the tackifying resin to the acrylic copolymer as described above has an adhesive strength itself with respect to a low-polar adherend at room temperature. However, it was not satisfactory in terms of peeling resistance, that is, the characteristic of not peeling even when a minute stress was applied for a long time.

In the solvent-type acrylic pressure-sensitive adhesive, the polymer therein generally has a weight average molecular weight of about 200,000 to 1,000,000 (polystyrene conversion by gel permeation chromatography method (GPC method St conversion)). However, when produced by the most commonly used radical polymerization method, a polydispersity index (Mw / Mn) of about 5 or more is used as an index showing the spread of the molecular weight distribution. There is. However, such adhesives have a large decrease in storage elastic modulus and loss elastic modulus at high temperature, and flow of the adhesive causes the adhesive properties to be unsatisfactory.

An object of the present invention is to solve the above-mentioned conventional problems and to provide an acrylic pressure-sensitive adhesive composition excellent in various adhesive properties to an adherend having a low polarity surface, particularly peeling resistance, and the adhesive composition. It is to provide a double-sided tape using a product.

[0007]

In order to solve the above-mentioned conventional problems, the present inventor has made earnest studies on tackifying resins to be blended in an acrylic copolymer, and as a result, the acrylic copolymer The inventors have found that the conventional problems described above can be solved by using a tackifying resin that is said to have poor compatibility with a polymer, and have completed the present invention.

[0008]

That is, the acrylic pressure-sensitive adhesive composition according to the first aspect of the present invention uses (meth) acrylic as a main component an alkyl (meth) acrylate having an alkyl group having 2 to 18 carbon atoms. In the system copolymer (A),
An acrylic pressure-sensitive adhesive composition containing a tackifying resin (B), which is a (meth) acrylic copolymer (A).
Has a polydispersity (Mw / Mn) of 4 or less, and the tackifying resin (B) has a rosin having a softening point of 80 to 130 ° C. or its derivative (c) and a rosin having a softening point of 140 to 200 ° C. or It is composed of a combination of the derivative (d), and the compounding amount of the pressure-sensitive adhesive imparting resin (B) is 5 to 40 parts by weight with respect to 100 parts by weight of the (meth) acrylic copolymer, and the resin (c) and The compounding ratio with the resin (d) is 2.5 ≦ ((d)
It is characterized in that x100) / ((c) + (d)) ≦ 75 (wt%).

[0010] double-sided tape of the present invention, acrylic according to claim 1 to or formed on both surfaces of the pressure-sensitive adhesive layer base layer comprising an acrylic pressure-sensitive adhesive composition according or claim 1 It can be obtained by forming a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive composition of the type as a pressure-sensitive adhesive layer of a so-called non-support type double-sided tape having no substrate layer.

The structure of the present invention will be described in more detail below. The (meth) acrylic copolymer used in the present invention uses a (meth) acrylic acid alkyl ester (A) having an alkyl group having 2 to 18 carbon atoms as a main component, that is, the ester (A) alone. Alternatively, it can be obtained by polymerization or copolymerization in combination with a monomer copolymerizable therewith. As the polymerization method, known methods such as bulk polymerization, solution polymerization, dispersion polymerization and emulsion polymerization may be used. The polymerization can be initiated by a thermal polymerization initiator such as benzoyl peroxide, lauroyl peroxide, azoisobutyronitrile, a photopolymerization initiator such as benzoin, benzoin methyl ether or benzophenone and ultraviolet irradiation, or by electron beam irradiation. The method can be selected arbitrarily. The weight average molecular weight of the obtained (meth) acrylic copolymer is preferably 200,000 or more.

Examples of the (meth) acrylic acid alkyl ester as the main component include ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, sec- Butyl (meth) acrylate, t-butyl (meth) acrylate, n-octyl (meth) acrylate, iso-octyl (meth) acrylate, 2
-Ethylhexyl (meth) acrylate, nonyl (meth) acrylate, dodecyl (meth) acrylate, etc. are used alone or in combination of two or more. When the carbon number of the alkyl group is out of the range of 2 to 18, the characteristics as the pressure-sensitive adhesive are impaired, which is not preferable.

Examples of the monomer copolymerizable with the main component include unsaturated acids such as (meth) acrylic acid, itaconic acid, 2- (meth) acrylic acid propane sulfonic acid and (meth) acryloxyethyl phosphate, and 2 Examples thereof include polar monomers such as hydroxyl group-containing monomers such as -hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. These polar monomers are effective as a component that enhances the cohesive force of the pressure-sensitive adhesive.

In addition to the polar monomers described above, it is also possible to use a monomer which imparts a polymer having a high glass transition point such as methyl (meth) acrylate, styrene, vinyl acetate, (meth) acrylonitrile and (meth) acrylamide.

The weight average molecular weight (Mw) and number average molecular weight (M) of the (meth) acrylic copolymer (A) used in the present invention.
n), that is, the polydispersity (Mw / Mn) is 4 or less. This suppresses the decrease in storage elastic modulus and loss elastic modulus at high temperature, prevents the flow of the adhesive at high temperature, and improves the peel resistance.

Rosin or its derivatives (a), (c) and (d) used as a tackifying resin in the present invention.
Of these, the derivatives include partially disproportionated or disproportionated rosins, hydrogenated rosins, maleic acid-modified rosins, polymerized rosins, formaldehyde-modified rosins, and the like, as well as these metal salts and other diethylene glycol, glycerin, pentaerythritol, etc. Esters are included.

The resin softening point of the rosin or its derivative (c) used in the invention of claim 1 is 80 to 130 ° C., and the resin softening point of the rosin or its derivative (d) is 14 ° C.
It is 0 to 200 ° C.

[0018]

[0019]

[0020]

According to the acrylic pressure-sensitive adhesive composition of the invention described in claim 1 , (meth) acrylic copolymer (A) 100
5 parts by weight of tackifying resin (B) in terms of solid content
-40 parts by weight are blended. If the compounding amount is less than 5 parts by weight, the effect of improving the peel strength becomes insufficient, and 40
If the amount is more than parts by weight, the cohesive force and the tack are reduced, which is not preferable.

According to the first aspect of the invention, the softening point is 80.
The compounding ratio of rosin or its derivative (c) having a softening point of 140 to 200 ° C. to rosin or its derivative (c) of −130 ° C. is 2.5 ≦ ((d) × 100) /
It is blended so that ((c) + (d)) ≦ 75 (wt%). If this blending ratio is less than 2.5% by weight, the peeling resistance to the low-polarity adherend is not improved, and also 75% by weight.
If it exceeds, the pressure-sensitive adhesive becomes too hard, and a sufficient initial adhesive force cannot be obtained, which is not preferable in any case.

The pressure-sensitive adhesive composition of the present invention has the above (meth)
In addition to containing the acrylic copolymer (A) and the tackifying resin (B) as essential components, a crosslinking agent can be usually added to improve cohesive strength. Examples of the cross-linking agent include conventionally known ones, for example, an isocyanate cross-linking agent, a melamine cross-linking agent, an epoxy cross-linking agent, and a peroxide cross-linking agent.

In the pressure-sensitive adhesive composition of the present invention, various conventionally known additives such as a plasticizer and a softening agent may be added, if necessary.
You may make it contain a filler, a pigment, a dye, etc. The pressure-sensitive adhesive tape may have a pressure-sensitive adhesive layer on one side, or may have a so-called double-sided tape shape having a pressure-sensitive adhesive layer on both sides of the base material. The base material is paper, non-woven fabric, plastic film made of polyester resin or polyolefin resin, polyolefin resin,
A plastic foam made of polyurethane resin, polychloroprene resin, acrylic resin or the like is used.
Further, it may be a so-called non-support type adhesive tape having no base material layer.

[0025]

( Operation ) In the invention described in claim 1 , the rosin or its derivative (c) having a softening point of 80 to 130 ° C. and the softening point of 140 to
A predetermined amount of the tackifying resin (B) is blended with rosin or its derivative (d) at 200 ° C. Conventionally, it has been preferred superior tackifying resin compatibility with the (meth) acrylic copolymer, according to claim 1
In the invention described in, the rosin or its derivative having a high softening point, which has been considered to have poor compatibility with the (meth) acrylic copolymer (A) due to the high molecular weight of the resin itself ( d) is used in combination with rosin or its derivative (c) having an appropriate softening point. Even in the case of this pressure-sensitive adhesive composition, the resin-compatible component and the resin-incompatible component coexist in the pressure-sensitive adhesive, and since the stress relaxation is actively promoted, the pressure-sensitive adhesive property, especially the peeling resistance is dramatically improved. Improve to.

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

<Measurement of Physical Properties> (1) SP Adhesiveness According to JIS Z1528, a tape was adhered to a SUS304 plate with a width of 20 mm, left at 23 ° C. for 20 minutes, and then the 180 ° peel strength was measured. Pulling speed is 3
It was set to 00 mm / min. (2) Adhesive strength of polypropylene (PP) A tape is attached to a PP plate with a width of 20 mm, and the tape is kept at 23 ° C. for 2 hours.
After leaving for 0 minutes, the 180 ° peel strength was measured. The pulling speed was 300 mm / min. (3) Holding power (80 ° C.) At room temperature, a tape was attached to a SUS304 plate in a size of 20 × 20 mm, left at 23 ° C. for 20 minutes, then left in an 80 ° C. system for 20 minutes, and a load of 1 kg was applied. The deviation (or drop time) after 1 hour was measured. (4) Polypropylene (PP) 90 ° constant load peeling retention force (60 ° C.) At room temperature, a tape is attached to a PP plate with a width of 20 mm,
After leaving it at 23 ° C. for 20 minutes, it was left in a 60 ° C. system for 20 minutes, and a load of 80 g was applied to peel it in the direction of 90 °, and the peeling length per unit time was measured.

[0044]

[0045]

[0046]

EXAMPLES The invention described in claim 1 will be described in detail with reference to Examples and Comparative Examples. In addition, Examples 1 to 8 and
Comparative Examples 1 to 6 and Table 1 are omitted numbers. Example 9 (1) Polymerization of acrylic copolymer 97 parts by weight of n-butyl acrylate, 3 parts by weight of acrylic acid, lauryl mercaptan 0.05 as a chain transfer agent
Parts by weight, and 80 parts by weight of ethyl acetate as a solvent were charged into a five-necked flask equipped with a stirrer, a reflux condenser, a thermometer, a dropping funnel and a nitrogen gas inlet so that the total amount was 1 kg, and dissolved by stirring. Then, it is 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, the temperature was maintained at 70 ° C., and 0.03 parts by weight of benzoyl peroxide as a thermal polymerization initiator was added to 3 cc of ethyl acetate. Dissolve in, and add dropwise with a dropping funnel. The reaction started, and the reaction was carried out at the same temperature for 10 hours to obtain an acrylic copolymer solution. (2) Measurement of molecular weight of acrylic copolymer The weight average molecular weight (Mw) and number average molecular weight (Mn) of the acrylic copolymer were measured by GPC method St conversion. The molecular weight measuring method by GPC method St conversion is as follows. By gel permeation chromatography, standard polystyrene was used as a reference, tetrahydrofuran was used as an eluent, and detection was performed using a refractometer. (3) Production of acrylic adhesive tape To 100 parts by weight of solid content of the acrylic copolymer solution,
Example 9: 0.05 part by weight of N, N'-hexamethylene-1,6-bis (1-aziridinecarboxamide) (HDU) as a cross-linking agent and a predetermined amount of the tackifying resin shown in Table 2 were blended. The adhesive composition of was prepared.

The tackifying resins used in Table 2 are as follows. 1: Arakawa Chemical Co., Ltd .; special rosin ester (softening point 108
~ 120 ° C) 2: manufactured by Rika Hercules Co., Ltd .; hydrogenated rosin ester (softening point 93 to 101 ° C) 3: Arakawa Chemical Co .; rosin modified phenolic resin (softening point 180 ° C) 4: Arakawa Chemical Co., Ltd .; polymerized rosin ester (Softening point 153
C.) The pressure-sensitive adhesive composition obtained as described above was coated on each of two release papers so that the thickness after drying was 75 μm, and then dried at a temperature of 110 ° C. for 5 minutes. Then, the pressure-sensitive adhesive composition on the release paper was laminated with a nonwoven fabric as an intermediate layer and pressure-bonded with a roll to obtain a nonwoven fabric-based double-sided tape.

Example 10 As shown in Table 2, a non-woven fabric-based double-sided tape was obtained in the same manner as in Example 9 except that the type of tackifying resin blended was different.

Example 11 A monomer composition was set to n-butyl acrylate / 2-ethylhexyl acrylate / acrylic acid = 79/18/3, and as shown in Table 2, except that the type of tackifying resin blended was different, A non-woven fabric-based double-sided tape was obtained in the same manner as in Example 9.

Example 12 As shown in Table 2, a non-woven fabric-based double-sided tape was obtained in the same manner as in Example 11 except that the type of tackifying resin blended was different.

Example 13 As shown in Table 2, a nonwoven fabric-based double-sided tape was obtained in the same manner as in Example 9 except that the type of tackifying resin to be mixed was different.

Example 14 As shown in Table 2, a nonwoven fabric-based double-sided tape was obtained in the same manner as in Example 11 except that the type of tackifying resin blended was different.

Comparative Example 7 As shown in Table 2, a non-woven fabric substrate double-sided tape was obtained in the same manner as in Example 9 except that the tackifying resin was not added.

Comparative Example 8 As shown in Table 2, a non-woven fabric substrate double-sided tape was obtained in the same manner as in Example 11 except that the tackifying resin was not added.

Comparative Example 9 As shown in Table 2, a nonwoven fabric-based double-sided tape was obtained in the same manner as in Example 9 except that the type of tackifying resin to be mixed was different.

Comparative Example 10 As shown in Table 2, a nonwoven fabric-based double-sided tape was obtained in the same manner as in Example 11 except that the type of tackifying resin blended was different.

Comparative Example 11 As shown in Table 2, a nonwoven fabric-based double-sided tape was obtained in the same manner as in Example 9 except that the type of tackifying resin to be mixed was different.

Comparative Example 12 As shown in Table 2, a nonwoven fabric-based double-sided tape was obtained in the same manner as in Example 11 except that the type of tackifying resin to be mixed was different.

Comparative Example 13 Without using lauryl mercaptan as a chain transfer agent,
A total of 1 kg of 97 parts by weight of n-butyl acrylate, 3 parts by weight of acrylic acid, and 100 parts by weight of ethyl acetate as a solvent were charged in a five-necked flask, and the reaction was started at 70 ° C. as in Example 9. After the reaction at this temperature for 3 hours, the temperature of the reaction system was raised to the boiling point (about 85 ° C.), and the reaction was performed under reflux for 7 hours to obtain an acrylic copolymer.
A non-woven fabric-based double-sided tape was obtained in the same manner.

Comparative Example 14 Without using lauryl mercaptan as a chain transfer agent,
97 parts by weight of n-butyl acrylate, 18 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid, and 150 parts by weight of ethyl acetate as a solvent were charged into a five-necked flask in a total amount of 1 kg, and the acrylic system was used in the same manner as in Comparative Example 13. A nonwoven fabric-based double-sided tape was obtained in the same manner as in Example 11 except that the copolymer was obtained.

SP adhesive strength, PP adhesive strength, holding power, and P
P constant load peeling retention force is based on the above-mentioned physical property measurement method.
It was measured.

[0063]

[Table 2]

As is clear from Table 2, the pressure-sensitive adhesive compositions of Examples 9 to 14 according to the invention described in claim 1 show high pressure-sensitive adhesive force not only in SP pressure-sensitive adhesive force but also in PP pressure-sensitive adhesive force. , Shows excellent adhesive properties to adherends having a low polarity surface and excellent peeling resistance.

[0065]

Similarly, the invention according to claim 1 shows excellent adhesion properties to various adherends including those having a low polarity surface such as polyethylene and polypropylene, and excellent peeling resistance.

The double-sided tape of the present invention, by using the above-mentioned acrylic pressure-sensitive adhesive composition, has excellent adhesive properties to an adherend having a low polarity and excellent peeling resistance.

Claims (2)

(57) [Claims] 1. A tackifying resin (B) is blended with a (meth) acrylic copolymer (A) containing a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 18 carbon atoms as a main component. A polydispersity (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the (meth) acrylic copolymer (A) is 4 or less. The tackifying resin (B) has a softening point of 80.
To 130 ° C. rosin or its derivative (c) and a softening point 140 to 200 ° C. rosin or its derivative (d) in combination, and the blending amount of the tackifying resin (B) is
5 to 40 parts by weight based on 100 parts by weight of the (meth) acrylic copolymer (A), and the resin (c) and the resin (d).
The acrylic pressure-sensitive adhesive composition, wherein the blending ratio thereof is 2.5 ≦ ((d) × 100) / ((c) + (d)) ≦ 75 (wt%). 2. The acrylic pressure-sensitive adhesive according to claim 1.
Pressure sensitive adhesive layer consisting of adhesive composition is formed on both sides of the base material layer
A double-sided tape that is characterized.