JP-7855874-B2 - Active energy ray curable hot melt adhesive composition, and adhesives and adhesive tapes using the same.

Inventors

• 峯 修平
• 浅野 鉄也

Assignees

• 三菱ケミカル株式会社

Dates

Publication Date

20260511

Application Date

20220301

Claims (7)

1. An active energy ray curable hot melt adhesive composition containing an acrylic resin (A) and a tackifier (B), The weight-average molecular weight of the acrylic resin (A) is 200,000 or more. An acrylic resin (A) obtained by polymerizing a copolymer component (a) containing an alkyl (meth)acrylate (a1) and a monomer (a2) having an ultraviolet active site, The content of the tackifier (B) is 10 to 40 parts by weight per 100 parts by weight of the acrylic resin (A). An active energy ray-curable hot-melt adhesive composition in which the tackifier (B) has a softening point of 115°C or higher .
2. The active energy ray curable hot melt adhesive composition according to claim 1, wherein the softening point of the tackifier (B) is 115 to 130°C.
3. The active energy ray-curable hot-melt adhesive composition according to claim 1 or 2, wherein the tackifier (B) is a rosin-based tackifier (B1).
4. The active energy ray-curable hot-melt adhesive composition according to any one of claims 1 to 3, wherein the copolymer component (a) of the acrylic resin (A) contains a polar group-containing ethylenically unsaturated monomer (a3).
5. Furthermore, the active energy ray-curable hot-melt adhesive composition according to any one of claims 1 to 4, further containing a crosslinking agent (C).
6. An active energy ray-curable hot-melt adhesive comprising a crosslinked active energy ray-curable hot-melt adhesive composition according to any one of claims 1 to 5.
7. An adhesive tape comprising an active energy ray-curable hot-melt adhesive as described in claim 6, formed on a substrate.

Description

This invention relates to an active energy ray-curable adhesive composition, and more particularly to an adhesive composition usable in hot-melt coated adhesive tapes, adhesive labels, and the like. Furthermore, this invention relates to an active energy ray-curable adhesive composition that, in addition to its excellent thermal stability, exhibits excellent adhesion, holding power, and curved surface adhesion to various substrates at room temperature, as well as excellent long-term heat resistance after bonding to a substrate. It also relates to adhesives and adhesive tapes using this composition. Conventionally, rubber-based adhesives and acrylic-based adhesives have been known as adhesives for adhesive tapes or adhesive sheets. As for acrylic-based adhesives, (co)polymers with specific alkyl (meth)acrylates as essential constituent units have been developed. In recent years, due to growing environmental concerns, adhesive compositions that do not use organic solvents have attracted attention. For example, Patent Documents 1 and 2 propose acrylic hot-melt adhesive compositions characterized by applying a heat-melted resin to a substrate. However, these conventional acrylic hot-melt adhesive compositions used in adhesive tapes and the like have the drawback of inferior adhesive properties such as adhesive strength and holding power. To address the above drawbacks, for example, Patent Document 3 proposes crosslinking a hot-melt coated acrylic adhesive composition by irradiation with active energy rays. Japanese Patent Application Publication No. 59-75975Japanese Unexamined Patent Publication No. 60-23469Special table 2018-501397 publication The present invention will be described in detail below. In this invention, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate. Furthermore, "acrylic resin" refers to a resin obtained by polymerizing a polymerization component containing at least one (meth)acrylate monomer. Furthermore, the term "tape" conceptually encompasses tapes, films, and sheets. The adhesive composition of the present invention contains an acrylic resin (A) and a tackifier (B). The following explains the constituent components in order. <Acrylic resin (A)> The acrylic resin (A) used in the present invention contains an alkyl (meth)acrylate (a1) and a monomer (a2) having an ultraviolet active site as copolymer components (a). [Alkyl (meth)acrylate (a1)] Examples of the alkyl (meth)acrylate (a1) mentioned above include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-propyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, and the like. Among these, n-butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are preferred in terms of adhesive strength. The alkyl (meth)acrylate (a1) preferably contains at least one monomer having a glass transition temperature of less than -60°C. Examples of monomers having a glass transition temperature of less than -60°C include 2-ethylhexyl acrylate, n-octyl acrylate, and isodecyl acrylate. The content of alkyl (meth)acrylate (a1) having a glass transition temperature of less than -60°C is 0 to 85% by weight, preferably 15 to 75% by weight, and particularly preferably 20 to 60% by weight, relative to alkyl (meth)acrylate (a1). If the content is too low, the coating properties tend to decrease, and if the content is too high, the adhesive strength after heating tends to decrease. The alkyl (meth)acrylate (a1) is typically 1 to 99% by weight, preferably 30 to 97% by weight, and particularly preferably 50 to 95% by weight, relative to copolymer component (a). If the content is too low, the glass transition temperature will rise, which tends to degrade the overall performance of the adhesive. Conversely, if the content is too high, the holding power and adhesion to curved surfaces tend to worsen. [Monomers having UV-active sites (a2)] As the monomer (a2) having the above-mentioned UV-active site, for example, a (meth)acrylic acid ester can be used, which has a site that is activated by ultraviolet light and can form crosslinks with another part of the (meth)acrylic copolymer molecule or with another acrylic copolymer molecule. Examples of UV-active sites include benzophenone structures, benzyl structures, o-benzoylbenzoic acid ester structures, thioxanthone structures, 3-ketocoumarin structures, 2-ethylanthraquinone structures, and camphaquinone structures. Each of these structures can be excited by UV irradiation, and in its excited state, it can abstract a hydrogen radical from the (meth)acrylic copolymer molecule. In this way, radicals are generated on the (meth)acrylic copolymer. Various reactions are triggered in the system, such as the formation of crosslinked stru