JP3194383B2 - One-part pressure-sensitive adhesive composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition, and more particularly, to a pressure-sensitive adhesive composition having excellent wettability, and particularly excellent low-temperature sticking property.

[Prior art] A pressure-sensitive adhesive made of an acrylic copolymer has a very convenient property of instantaneously adhering to a partner at a pressure of about a finger pressure, and also exhibits excellent weather resistance. It is used in various fields such as industrial adhesive tapes, labels, double-sided adhesive tapes and adhesive sheets.

Acrylic copolymers used in pressure-sensitive adhesives are:
It is usually a synthetic product such as an acrylate ester, which is a copolymer of a soft main monomer with low glass transition temperature that gives wettability and tackiness, and a small amount of a hard monomer with high glass transition temperature that gives adhesion and cohesion. is there.

Therefore, conventional pressure-sensitive adhesives made of an acrylic copolymer tend to cause a decrease in wettability when the cohesiveness is increased, and also have a disadvantage that the adhesive strength at low temperatures is weak. In the past, in the field of adhesives, a crosslinking agent has been added to improve adhesiveness, but conventionally used crosslinking agents have a low molecular weight, a high reactivity and a high curing speed. Therefore, there is a disadvantage that pot life is short and workability is inferior.

[Problems to be Solved by the Invention] The present invention improves the drawbacks of the above-described conventional technology, and has excellent wettability, tackiness, cohesiveness, and adhesiveness, particularly at low temperatures, and has a relatively long pot life. The purpose of the present invention is to provide a pressure-sensitive adhesive composition having excellent workability.

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, surprisingly, a telechelic oligomer having a weight average molecular weight of 2,000 to 30,000 as a cross-linking agent was surprisingly obtained. It has been found that the use thereof has a remarkably excellent adhesiveness at a low temperature and a relatively long pot life and excellent workability, and based on this finding, the present invention has been completed.

That is, the present invention is a copolymer of acrylic acid or methacrylic acid ester and acrylic acid, methacrylic acid or acrylamide, based on 100 parts by weight of a copolymer containing acrylic acid ester or methacrylic acid ester as a main component. A telechelic oligomer having a weight average molecular weight of at least 2,000 and at most 30,000 having at least two isocyanate groups bonded to molecular terminals as a crosslinking agent;
It is intended to provide a one-part pressure-sensitive adhesive composition characterized by containing up to 20 parts by weight.

 Hereinafter, the present invention will be described in detail.

The pressure-sensitive adhesive composition of the present invention is a copolymer of acrylic acid ester and / or methacrylic acid ester and acrylic acid, methacrylic acid, acrylamide or vinyl monomer, wherein acrylic acid ester and / or methacrylic acid ester are used. A copolymer as a main component is used.

As acrylic acid esters, methyl acrylate,
Various acrylic acid alkyl esters such as ethyl acrylate, various propyl acrylates, various butyl acrylates, various pentyl acrylates, various hexyl acrylates, various heptyl acrylates, various octyl acrylates, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl Examples include various hydroxyl group-containing acrylates such as acrylates, and two or more kinds thereof can be used in combination.

Examples of the methacrylate include methyl methacrylate, ethyl methacrylate, various propyl methacrylates, various butyl methacrylates, various pentyl methacrylates, various hexyl methacrylates, various heptyl methacrylates, various octyl methacrylates, various methacrylic acid alkyl esters, 2-hydroxyethyl methacrylate, and the like. And various hydroxyl group-containing methacrylates such as -hydroxypropyl methacrylate, and the like, and two or more kinds thereof can be used in combination.

In addition, as a vinyl monomer which can be employed as a desired monomer unit in the copolymer of the present invention, an aromatic vinyl compound such as styrene α-methylstyrene and a vinyl fatty acid compound such as vinyl acetate, vinyl propionate and vinyl butyrate are used. be able to.

The molecular weight of the acrylic acid copolymer is not particularly limited, but usually the weight average molecular weight is preferably in the range of 500,000 to 3,000,000.

In the present invention, the above acrylic copolymers can be used alone or in combination of two or more.

The telechelic oligomer used as a crosslinking agent in the present invention is an oligomer having an isocyanate group as a functional group at a molecular terminal and having at least two functional groups in one molecule. The functional group is, as described above,
At least two are required, and may be three, four, or more.

The main chain of the telechelic oligomer is a polyoxyalkylene oligomer such as polyoxyethylene oligomer or polyoxypropylene oligomer, butadiene oligomer, isoprene oligomer, butadiene-isoprene copolymerized oligomer, butadiene-pentadiene copolymerized oligomer, butadiene-acrylonitrile copolymerized. Examples thereof include oligomers, conjugated diene-based oligomers such as butadiene-styrene copolymerized oligomers, and vinyl monomer oligomers such as styrene oligomers, with polyoxyalkylene oligomers being preferred. These telechelic oligomers may be used alone or in combination of two or more.

The telechelic oligomer used in the present invention needs to have a weight average molecular weight of 2,000 to 30,000, preferably 2,000 to 10,000, and particularly preferably 2,000 to 5,000. When the weight average molecular weight is less than 2,000, the adhesive strength at low temperatures is poor, and the curing speed is high, so that the pot life is short and workability is poor. On the other hand, when the weight average molecular weight exceeds 30,000, there is a disadvantage that the curing speed becomes too slow.

The composition ratio of the acrylic copolymer and the telechelic oligomer is such that the telechelic oligomer is usually in the range of 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the acrylic copolymer. Part within the range.
If the amount of the telechelic oligomer is less than 0.1 part by weight, the holding power may be poor, and if it exceeds 20 parts by weight, the resin may be excessively cured, the wettability may be poor, and the adhesive strength may be poor.

The pressure-sensitive adhesive composition of the present invention is usually used as a one-pack type pressure-sensitive adhesive composed of a main agent composed of the acrylic copolymer and a crosslinking agent component. Good.

Examples of the crosslinking accelerator include amino compounds such as triethylamine and tetramethylbutanediamine;
Tin, dimethyltin dichloride, trimethyltin hydroxide, di-n-butyltin dilaurate, dibutyltin diacetate, dibutyltin sulfide, ferric chloride, iron acetyl acetate, cobalt naphthenate, bismuth nitrate, lead oleate, antimony trichloride, etc. And the like.

The addition ratio of these crosslinking accelerators is usually in the range of 1 to 50 parts by weight based on 100 parts by weight of the telechelic oligomer as the crosslinking agent.

The pressure-sensitive adhesive composition of the present invention may contain a tackifying resin or other crosslinking agent, and may contain various additives such as a plasticizer, a softener, a filler, a pigment, a dye, and the like. You may not.

[Examples] Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Various tests in the examples were performed according to the following measurement methods.

<Ball tack> This was performed according to JIS Z-0237 (ball rolling method).

<Loop tack> A clean test plate (SUS304) is fixed horizontally to the lower chuck, and a test piece (25 mm wide, 250 mm long, with free portions 25 mm at both ends)
With the adhesive side facing out, align both ends of the test piece, sandwich the aligned part between the upper chucks, set the distance between the upper chuck and the test plate to 210 mm, and set the test pieces at a speed of 300 ± 30 mm / min. Was reduced by 150 mm, and after 15 seconds, the force (g / 25 mm) when peeling off at the same speed was measured.

<Adhesive force> The test was performed according to JIS Z-0237 (180 degree peeling method).
However, it was peeled off after being left for 24 hours after the pressure bonding.

<Holding force> This was performed according to JIS Z-0237. However, the measurement temperature is 40 ° C
I made it.

Example 1 90 g of n-butyl acrylate, 10 g of acrylic acid, 0.05 g of benzoyl peroxide and 150 g of ethyl acetate were put into a 500 mL four-necked flask equipped with a reflux condenser, a nitrogen inlet tube, a thermometer, and a stirring blade. After stirring for 30 minutes at room temperature under a nitrogen stream,
The temperature was raised to 70 ° C., and the reaction was performed for 8 to 9 hours. The resulting polymer solution was clear and had a concentration of 40% by weight. To 100 parts by weight of a 35% by weight ethyl acetate solution containing an acrylic copolymer, 2 parts by weight of a trifunctional isocyanate-based telechelic oligomer having a weight average molecular weight of 3500 and having a structure of the following formula [I] was added, A pressure-sensitive adhesive composition was obtained.

Place this pressure sensitive adhesive composition on a polyester film for 25
g / m2 to form a pressure-sensitive adhesive composition.
The adhesive film was tested for ball tack, loop tack at room temperature and low temperature, and holding force test. The results are shown in Table 1.

Comparative Example 1 In Example 1, instead of the trifunctional isocyanate-based telechelic oligomer, a trifunctional isocyanate-based telechelic oligomer having a weight average molecular weight of 656 and having a structure of the following formula [II] [Coronate: Nippon Polyurethane ( Co., Ltd.] was prepared in the same manner as in Example 1 except that 0.75 parts by weight was used, and the same test was performed. The results are shown in Table 1.

Example 2 65 g of N-butyl acrylate, 28 g of 2-hydroxyethyl acrylate, 5 g of vinyl acetate, 4 g of acrylate, 0.05 g of benzoyl peroxide and 150 g of ethyl acetate were refluxed with a cooler, a nitrogen inlet tube, a thermometer, and stirred. The mixture was charged into a 500 mL four-necked flask equipped with blades, and an acrylic copolymer was produced in the same manner as in Example 1. The weight average molecular weight of the obtained acrylic copolymer was 800,000. To 100 parts by weight of a 35% by weight ethyl acetate solution containing the acrylic copolymer, 6 parts by weight of a trifunctional isocyanate-based telechelic oligomer having a weight average molecular weight of 3,500 and having a structure of the following formula [III] is added. A pressure-sensitive adhesive composition was obtained. Next, an adhesive film was prepared in the same manner as in Example 1, and the same test was performed. The results are shown in Table 1.

Comparative Example 2 In Example 2, instead of the trifunctional isocyanate-based telechelic oligomer, a trifunctional isocyanate-based telechelic oligomer having a weight average molecular weight of 656 used in Comparative Example 1 [Coronate L: manufactured by Nippon Polyurethane Co., Ltd.] 2
An adhesive film was prepared in the same manner as in Example 2 except that parts by weight were used, and the same test was performed. The results are shown in Table 1.

Comparative Example 3 The weight average molecular weight was 2 with respect to 100 parts by weight of a 35% by weight ethyl acetate solution containing the acrylic copolymer produced in Example 1.
0.5 parts by weight of a bifunctional epoxy-based telechelic oligomer having a structure of [IV] and 0.5 parts by weight of an amine accelerator (imidazole) was added to obtain a pressure-sensitive adhesive composition. Next, an adhesive film was prepared in the same manner as in Example 1, and the same test was performed. The results are shown in Table 1.

Comparative Example 4 In Comparative Example 3, instead of the bifunctional epoxy-based telechelic oligomer, a tetrafunctional epoxy-based telechelic oligomer having a weight average molecular weight of 366 and having a structure of the following formula [V] [Tetrad X: Mitsubishi Gas Chemical Co., Ltd. A film was prepared in the same manner as in Comparative Example 3 except that 0.03 parts by weight was used, and the same test was performed. These results are
It is shown in the table.

[Effect of the Invention] The pressure-sensitive adhesive composition of the present invention has a weight average molecular weight of 2,000.
By including a telechelic oligomer of not less than 30,000 or less as a cross-linking agent, the wettability is excellent, and the cohesive force of the pressure-sensitive adhesive is not reduced, and the bonding performance is improved, especially at low temperatures. Is remarkably excellent. Further, since the curing time is relatively long, the pot life is long and the workability is excellent.

Therefore, it can be said that the present invention has extremely high practical value. The pressure-sensitive adhesive composition of the present invention is an industrial pressure-sensitive adhesive tape,
It can be used in a wide range of fields such as medical adhesive tapes, adhesives, free albums, adhesive sheets and labels.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Takanori Saito 5-14-42 Nishikicho, Warabi-shi, Saitama Lintec Co., Ltd. (56) References JP-A-62-50373 (JP, A) JP-A-56-62865 (JP, A) JP-A-54-108833 (JP, A) JP-A-2-60983 (JP, A) JP-A-59-81324 (JP, A) JP-A-1-178567 (JP, A) JP-A-63-118379 (JP, A) JP-A-62-220512 (JP, A) JP-A-2-32181 (JP, A) JP-A-56-5535 (JP, A) JP-A-58-127914 (JP) JP, A) JP-A-2-178380 (JP, A) JP-A-62-218463 (JP, A) JP-A-62-201983 (JP, A) JP-A-50-23432 (JP, A) Hei 2-99578 (JP, A) JP-A-49-22436 (JP, A) JP-A-63-165418 (JP, A) JP-A-63-165 420 (JP, A) JP-A-2-272013 (JP, A) JP-A-59-179679 (JP, A) JP-A-1-502436 (JP, A) Polyurethane resin handbook (1987: Nikkan Kogyo Shimbun) (Edited by Keiji Iwata) pp. 90-110 (58) Fields investigated (Int. Cl. ⁷ , DB name) C09J 1/00-201/10 C08G 18/00-18/87 C08F 8/00-8 / 50

Claims (1)

(57) [Claims] 1. A copolymer of an acrylic acid ester or a methacrylic acid ester with acrylic acid, methacrylic acid or acrylamide, based on 100 parts by weight of a copolymer mainly composed of an acrylic acid ester or a methacrylic acid ester Having a weight average molecular weight of at least 2 having at least two isocyanate groups bonded to molecular terminals as a crosslinking agent;
A one-part pressure-sensitive adhesive composition comprising 0.1 to 20 parts by weight of a telechelic oligomer having a molecular weight of 30,000 or less.