JP2001288438A - Adhesive composition - Google Patents

Abstract

(57) [Problem] To provide a pressure-sensitive adhesive composition having improved adhesion to polyolefin. SOLUTION: The alkyl acrylate having an alkyl group having 2 to 8 carbon atoms is 5 to 90 parts by weight, and the carbon number is 9
5 to 90 parts by weight of an alkyl acrylate having an isoalkyl group of from 18 to 5 and 50 to 50 parts by weight of an olefin polymer having a polymerizable unsaturated double bond at a terminal. An adhesive composition characterized by the following.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive composition, and more particularly to a pressure-sensitive adhesive composition having improved adhesion to polyolefin.

[0002]

2. Description of the Related Art A pressure-sensitive adhesive composition is formed into a sheet having a specified thickness and is used for various purposes as a pressure-sensitive adhesive tape. One of the basic properties required of a pressure-sensitive adhesive composition is to adhere strongly to various adherends. The adherend includes metal, plastic, wood, concrete and the like. The plastic to which the pressure-sensitive adhesive composition is applied includes various types such as polyolefin such as polyethylene and polypropylene, polyvinyl chloride, polyester, polyurethane, epoxy resin, acrylic resin, polycarbonate resin, ABS resin and the like. Until now, polyvinyl chloride resin has been used in various applications such as automobiles and home appliances from the viewpoint of flexibility control, durability and cost. However, in recent years, it has been changed to polyolefin from the viewpoint that waste disposal is difficult.

[0003] Polyolefin is a resin having extremely low polarity because it is composed of only carbon and hydrogen. In order to provide a pressure-sensitive adhesive composition that strongly adheres to such a low-polarity resin, it is necessary to lower the polarity of the pressure-sensitive adhesive composition so as to approach a polyolefin. Acrylic copolymers that have been used as pressure-sensitive adhesive compositions have been difficult to provide pressure-sensitive adhesive compositions that can strongly adhere to polyolefins because of the inherent high polarity of acrylic copolymers. Was. The present inventor has already taken this situation into account, as shown in JP-A-11-140406,
The present invention has invented a pressure-sensitive adhesive composition which imparts flexibility by copolymerizing an alkyl acrylate having a long side chain to enhance the adhesive strength.

[0004]

However, in applications for joining polyolefins with high strength, further improvement in adhesive strength has been demanded. Therefore, an object of the present invention is to provide a pressure-sensitive adhesive composition with further improved adhesive strength.

[0005]

The present inventors have made intensive studies in view of the above-mentioned problems, and as a result, have found that a specific alkyl acrylate, a specific isoalkyl acrylate, and an olefin having a polymerizable unsaturated double bond at a terminal. By using an acrylic copolymer consisting of a specific amount of the system polymer,
Further, they have found that a pressure-sensitive adhesive composition having improved adhesive strength can be obtained, and have reached the present invention. That is, the pressure-sensitive adhesive composition of the present invention has 5 to 90 parts by weight of an alkyl acrylate having an alkyl group having 2 to 8 carbon atoms, and has 9 to 1 carbon atoms.
5 to 90 parts by weight of an alkyl acrylate having an isoalkyl group of 8 and 5 to 50 parts by weight of an olefin polymer having a polymerizable unsaturated double bond at the terminal. Features.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The pressure-sensitive adhesive composition used in the present invention comprises:
5 to 90 parts by weight of an alkyl acrylate having an alkyl group having 2 to 8 carbon atoms, 5 to 90 parts by weight of an alkyl acrylate having an isoalkyl group having 9 to 18 carbon atoms
It is composed of an acrylic copolymer copolymerized by weight with 5 to 50 parts by weight of an olefin polymer having a polymerizable unsaturated double bond at its terminal. This will be described in detail below.

The alkyl acrylate having an alkyl group having 2 to 8 carbon atoms includes, for example, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, butyl acrylate, sec-butyl acrylate, acrylic acid Examples include t-butyl, cyclohexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, and the like. These may be used alone or in combination of two or more.

The alkyl acrylate having an isoalkyl group having 9 to 18 carbon atoms includes, for example,
Examples include isononyl acrylate, isomyristyl acrylate, and isostearyl acrylate. These may be used alone or in combination of two or more.

The olefin polymer having a polymerizable unsaturated double bond at the terminal is a polymer having a double bond copolymerizable with another polymerizable monomer at the terminal and a polymer structure comprising a polyolefin main skeleton. If so, there is no particular limitation. Specific examples of the polyolefin skeleton include an ethylene-butylene copolymer, an ethylene-propylene copolymer, a propylene copolymer, an ethylene copolymer, and a butylene copolymer. Commercially available ethylene-butylene copolymers include, for example, “Clayton Liquid Polymer L-1251” and “Clayton Liquid Polymer L-1253” manufactured by Clayton Polymer Japan, and “Terminal functional groups manufactured by Tonen Chemical Co., Ltd.” Type PP "
And the like.

In the acrylic copolymer, the content of the alkyl acrylate having an alkyl group having 2 to 8 carbon atoms is 5 to 90% by weight, preferably 10 to 80% by weight. The alkyl acrylate having an isoalkyl group having 9 to 18 carbon atoms is 5 to 90% by weight.
And preferably 10 to 80% by weight. Exceeding these ranges will impair the adhesion. The content of the olefin polymer having an unsaturated double bond is 5 to 50% by weight, preferably 10 to 40% by weight. If it is less than 5% by weight, the adhesiveness is reduced, and if it exceeds 50% by weight, the number of carbon atoms is 2-8.
Alkyl acrylate having an alkyl group of
It does not mix with the alkyl acrylate having an isoalkyl group having 9 to 18 carbon atoms.

Further, a polar copolymer monomer having an unsaturated double bond may be added in order to adjust the glass transition temperature and the polarity of the obtained acrylic copolymer. Examples of such a polar copolymerizable monomer include styrene-based monomers such as styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, carboxylic acid vinyl esters such as vinyl acetate, acrylic acid, methacrylic acid, and itaconic acid. Carboxylic acid having a vinyl group, such as carboxylic acid anhydride having a vinyl group; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, modified caprolactone (meth) acrylate, polyoxy Ethylene (meth) acrylate, polyoxypropylene (meth)
Examples thereof include vinyl monomers having a hydroxyl group such as acrylate, and these may be used alone or in combination of two or more.

When the amount of the copolymerizable monomer increases, the flexibility of the resulting pressure-sensitive adhesive composition decreases and the adhesion decreases, so that the amount of the copolymerizable monomer is 20% by weight based on the copolymerization component of the acrylic copolymer. The following is preferred.

Further, the acrylic copolymer may be crosslinked, if necessary, to improve heat resistance and creep characteristics. As a crosslinking method, for example, in a solution polymerization in which an acrylic copolymer is polymerized in a solvent or an emulsion polymerization in which water is polymerized in water, a polymerizable monomer having a reactive polar group is contained, and the polymerizable monomer can react with the polar group. A method of crosslinking by adding a suitable crosslinking agent is exemplified.

Examples of the crosslinking agent include isocyanate-based crosslinkers such as tolylene diisocyanate, naphthylene-1,5-diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate. Agents, epoxy glycol crosslinking agents such as ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,6-hexanediol glycidyl ether,
Aziridine-based cross-linking agents such as N, N-hexamethylene-1,6-bis (1-aziridinecarboxamide) and the like may be used, and these may be used alone or in combination of two or more.

When the acrylic copolymer is polymerized by photopolymerization, a polyfunctional (meth) acrylate compound is added as a crosslinking agent so that the acrylic copolymer can be crosslinked at the same time as the polymerization of the acrylic copolymer. Can do it.

Examples of the polyfunctional (meth) acrylate compound include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and 1,9-nonanediol di (meth) acrylate. Acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, glycerin methacrylate acrylate, pentaerythritol tri (meth) ) Acrylate, trimethylolpropane trimethacrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy (meth) acrylate, polyester (meth) acrylate, urethane (Meth) acrylate and the like. These may be used alone, or two or more may be used in combination.

When the amount of the crosslinking agent is small, the cohesive strength of the pressure-sensitive adhesive composition is reduced, resulting in poor heat resistance and creep characteristics. When the amount is large, the flexibility is impaired and the adhesion is reduced.
Therefore, it is preferably 0.01 to 5 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the acrylic copolymer component.
02 to 3 parts by weight.

A tackifier is added to the acrylic copolymer of the present invention in order to improve the adhesion. As the tackifier, for example, rosin-based resin, modified rosin-based resin, terpene-based resin, terpene phenol-based resin,
C ₅ and C ₉ petroleum resins, such as chroman resins, and their hydrogenated products, and the like. These may be used alone or in combination of two or more.

The amount of the tackifier is from 5 to 50 parts by weight, preferably from 10 to 40 parts by weight, based on 100 parts by weight of the acrylic copolymer. If the addition amount is less than 5 parts by weight, the improvement in adhesion is small, and if it exceeds 50 parts by weight, the flexibility of the pressure-sensitive adhesive composition is reduced, and the adhesion is reduced. When the above tackifier is added to the photopolymerizable composition and polymerized, a decrease in the polymerization rate or a decrease in the molecular weight may occur.In such a case, a chain transfer agent or a crosslinkable monomer may be used. The amount is preferably adjusted appropriately, and examples of the tackifier having a low polymerization inhibitory property include a hydrogenated terpene resin, a hydrogenated rosin resin, a disproportionated rosin resin, an alicyclic saturated hydrocarbon resin, and the like.

Various additives may be added to the acrylic copolymer of the present invention, if necessary. Examples of the additive include a plasticizer, a softener, an inorganic filler (such as calcium carbonate, talc, aluminum, and silica), an organic filler, a pigment, and a dye. Further, as a filler, the volume of the pressure-sensitive adhesive composition may be increased by adding hollow fine particles having an average particle diameter of 5 to 200 μm, or by performing polymerization in a state where a gas is mixed with a copolymerization component before polymerization with stirring. Good.

The acrylic copolymer of the present invention can be obtained by a conventionally known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, and pearl polymerization. When performing solution polymerization, a thermal polymerization initiator such as azobisisobutylnitrile and benzoyl peroxide is used in the presence of a solvent such as ethyl acetate or toluene. In the case of bulk polymerization, photopolymerization using ultraviolet (UV) is preferred because a uniform polymer is easily obtained, and a photopolymerization initiator is used for photopolymerization.

Examples of the photopolymerization initiator include, for example, 4-
(2-Hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone [trade name: Darocure-295]
9, manufactured by Merck Co.]; α-hydroxy-
α, α'-dimethyl-acetophenone [trade name: Darocure 1173, manufactured by Merck], methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone [trade name: Irgacure 651, manufactured by Ciba Geigy],
Acetophenones such as 2-hydroxy-2-cyclohexyl acetophenone [trade name: Irgacure 184, manufactured by Ciba Geigy]; ketals such as benzyl dimethyl ketal; Can be

The addition amount of the photopolymerization initiator is 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the acrylic copolymer component.
When the addition amount of the photoinitiator is less than 0.01 part by weight, the polymerization addition rate decreases, and only a polymer having a strong monomer odor is obtained.
If the amount exceeds 5 parts by weight, the amount of generated radicals increases, the molecular weight decreases, and the necessary cohesive strength may not be obtained.

As the lamps used for light irradiation in photopolymerization, those having an emission distribution at a light wavelength of 400 nm or less are used. Examples thereof include low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, Lamps, black light lamps, microwave excited mercury lamps, metal halide lamps and the like are used. Among them, the chemical lamp efficiently emits light in the active wavelength region of the initiator, and because the composition other than the initiator absorbs less light, light is transmitted to the inside to produce a product with a thick film. It is preferable to do. The light irradiation intensity on the photopolymerizable composition by the lamp is a factor that affects the degree of polymerization of the obtained polymer, and is appropriately controlled for each performance of the target product.
When a conventional cleavage-type initiator having an acetophenone group is blended, the range is within a wavelength range effective for photodecomposition of the initiator (depending on the initiator, usually 365 nm to 420 n
m of light are used. ) Is 0.1-100 mW
/ Cm ² is preferred.

The pressure-sensitive adhesive composition according to the present invention may be used as a pressure-sensitive adhesive as it is, or may be used in the form of a pressure-sensitive adhesive tape. When the pressure-sensitive adhesive tape is used, the pressure-sensitive adhesive tape may be in the form of a double-sided pressure-sensitive adhesive tape having no substrate, or may be a pressure-sensitive adhesive tape with a substrate in which a pressure-sensitive adhesive layer is formed on one or both surfaces of the substrate.

[0026]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the examples.
In addition, the evaluation method of the adhesive sheet in an Example and a comparative example is as follows.

(1) 90 ° peel adhesion test Under an atmosphere of 23 ° C., an adhesive sheet sandwiched between PET films is cut into a width of 20 mm × a length of 100 mm.
Under a 3 ° C. atmosphere, one of the PET films was peeled off to expose the pressure-sensitive adhesive sheet, and was bonded to a polypropylene plate (manufactured by Nippon Test Panel) having a width of 25 mm and a length of 150 mm.
The pressure-sensitive adhesive sheet was attached from the exposed pressure-sensitive adhesive sheet surface side so as to be 0 mm. Next, the other P of the pressure-sensitive adhesive sheet
The ET film was peeled off, a polyester film having a pressure of 25 μm was adhered to the exposed adhesive sheet surface as a backing material, and the backing material was pressed back and forth with a 2 kg roller from the back side of the backing material at 23 ° C. After standing for 24 hours, a tensile tester was used in an atmosphere at 23 ° C. for 3 hours.
The 90-degree peel adhesion was measured at a pulling speed of 00 mm / min. The measurement was also performed using a stainless steel plate (SUS304, manufactured by Nippon Test Panel) instead of the polypropylene plate.

(2) Shear Adhesion Test The adhesive tape was cut into a piece having a width of 20 mm × 20 mm, and was cut at 23 ° C.
Under an atmosphere, the center portions of two polypropylene plates (manufactured by Nippon Test Panel Co., Ltd.) having a width of 25 mm and a length of 100 mm were adhered to each other via an adhesive sheet from which PET films on both sides were peeled off, and pressed at a load of 5 kg for 15 minutes. Twenty-four hours later, the sheet was pulled in the shear direction at a pull rate of 50 mm / min, and the shear adhesive strength was measured. The measurement was also performed using a stainless steel plate (SUS304, manufactured by Nippon Test Panel) instead of the polypropylene plate.

Example 1 2-Ethylhexyl acrylate (60 parts by weight), isostearyl acrylate (20 parts by weight), an olefin copolymer having a polymerizable unsaturated double bond at a terminal (trade name: HPV)
(ML-1253, manufactured by Clayton Polymer Japan)
15 parts by weight, acrylic acid 5 parts by weight, hexanediol diacrylate 0.1 part by weight, polymerization initiator (trade name: Irgacure 651, manufactured by Ciba Geigy) 0.1 part by weight,
After stirring 20 parts by weight of a tackifier (alicyclic saturated hydrocarbon resin, trade name: Alcon P-100, manufactured by Arakawa Chemical Co., Ltd.) in a separable flask until uniform, the mixture is dissolved by bubbling with nitrogen gas. Oxygen was removed to prepare a polymerizable monomer solution.

Next, a 1 mm-thick spacer was placed on a 50 μm-thick polyethylene terephthalate (PET) film subjected to a mold release treatment, and the polymerizable monomer solution was spread on the PET film subjected to a mold release treatment.
The film was folded and coated so that the release treated surface was in contact with the polymerizable monomer solution. In this state, the PE on the coating side
UV irradiation intensity on T film is ² mW / cm ²
Adjust the lamp intensity of the chemical lamp so that
Ultraviolet irradiation was performed for 0 minutes. Then, a sheet-shaped pressure-sensitive adhesive composition (hereinafter, pressure-sensitive adhesive sheet) was obtained. The obtained pressure-sensitive adhesive sheet was subjected to a 90-degree peel adhesion test and a shear adhesion test, and the results are shown in Table 1.

Example 2 An adhesive sheet was obtained in the same manner as in Example 1 except that no tackifier was added. The obtained pressure-sensitive adhesive sheet was subjected to a 90-degree peel adhesion test and a shear adhesion test, and the results are shown in Table 1.

Comparative Example 1 A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 2 except that an olefin copolymer having a polymerizable unsaturated double bond at a terminal was not used. 9 of the obtained adhesive sheet
A 0-degree peel adhesion test and a shear adhesion test were performed, and the results are shown in Table 1.

Comparative Example 2 20 parts by weight of lauryl acrylate, 80 parts by weight of 2-ethylhexyl acrylate, 2 parts by weight of acrylic acid, 0.02 parts by weight of n-dodecanethiol, 0.05 parts by weight of hexanediol diacrylate, a polymerization initiator ( (Commercial name: Irgacure 651, Ciba Geigy) 0.1 parts by weight were stirred in a separable flask until uniform, and then dissolved oxygen was removed by bubbling with nitrogen gas to prepare a polymerizable monomer solution. . Next, an adhesive sheet was obtained in the same manner as in Example 1. The obtained pressure-sensitive adhesive sheet was subjected to a 90-degree peel adhesion test and a shear adhesion test, and the results are shown in Table 1.

[0034]

[Table 1]

[0035]

According to the pressure-sensitive adhesive composition of the present invention, an alkyl acrylate having 5 to 90 parts by weight of an alkyl acrylate having an alkyl group having 2 to 8 carbon atoms and an alkyl acrylate having an isoalkyl group having 9 to 18 carbon atoms are provided. 5 to 90 parts by weight of an ester, 5 to 50 parts by weight of an olefin polymer having a polymerizable unsaturated double bond at the terminal, so that it is composed of an acrylic copolymer having a main component, so that it is bonded to a polyolefin with high strength. It is possible to do. Therefore, it is possible to provide an adhesive product that is optimal for joining polyolefins used in various applications such as automobiles and home appliances.

Continued on the front page F term (reference) 4J011 QA03 QB01 SA01 SA51 SA84 UA06 4J027 AA08 BA07 CB10 CC04 CC05 CD09 4J040 BA202 DK012 DN032 EB022 FA182 FA231 GA01 HB19 HB41 HC14 HD21 JA02 JB07 KA16 KA25 LA06 MA11 NA05 NA10

Claims (3)

[Claims] 1. An acrylic acid alkyl ester having an alkyl group having 2 to 8 carbon atoms in an amount of 5 to 90 parts by weight and a carbon number of 9
5 to 90 parts by weight of an acrylic acid alkyl ester having an isoalkyl group of from 18 to 18, and 5 to 50 parts by weight of an olefin polymer having a polymerizable unsaturated double bond at a terminal thereof. Composition. 2. A photopolymerization initiator is added within a range of 0.01 to 5 parts by weight based on 100 parts by weight of a monomer constituting the acrylic copolymer according to claim 1, and copolymerized by a photopolymerization reaction. A pressure-sensitive adhesive composition comprising an acrylic copolymer. 3. The acrylic copolymer 10 according to claim 1,
A pressure-sensitive adhesive composition, wherein 5 to 50 parts by weight of a tackifier resin is added to 0 parts by weight.