JPS5991182A - Preparation of pressure-sensitive adhesive tape - Google Patents

Abstract

PURPOSE:To prepare a pressure-sensitive adhesive tape with high adhesive power and anchoring property, by applying a mixed solution of an acryloyl group-containing polymerizable compd. and a photosensitizer and then a pressure-sensitive adhesive to a surface-oxidized polyolefin sheet, followed by irradiation with an ionizing radiation. CONSTITUTION:The surface of a polyolefin sheet (e.g. polyethylene sheet) is oxidized by treatment with corona, flame, etc. and a mixed solution of a liquid polymerizable compd. having at least one (meth) acryloyl group in the molecule (e.g. 2-ethylhexyl acrylate) and a photosensitizer (e.g. benzoin) are applied to the treated surface, followed by application of an overcoat of a pressure-sensitive adhesive (e.g. synthetic rubber or acrylic polymer-based pressure sensitive adhesives) in a dry film thickness of about 5-50mum and drying. The sheet is then irradiated with an ionizing radiation (e.g. electron beam or gamma-ray) in a dose of about 1-5 Mrad.

Description

DETAILED DESCRIPTION OF THE INVENTION In the production of a pressure-sensitive adhesive tape or sheet having a polyolefin sheet as a support, the present invention utilizes specific reagents and radiation energy to bond a polyolefin sheet and a pressure-sensitive adhesive layer. This article relates to a method for producing pressure-sensitive adhesive tapes that can greatly improve anchoring properties and provide stable adhesive and cohesive strength. Conventionally, paper, plastic sheets, and metal have been used as supports for pressure-sensitive adhesive tapes. Various self-supporting sheets such as foil are used τ
However, polyolefin sheets such as polyethylene and polypropylene have excellent moisture resistance, chemical resistance, and electrical insulation properties, making them useful for a variety of applications such as packaging, surface preservation, and electrical insulation. It can be said that it is a support body.

However, the pressure-sensitive adhesive layer coated and dried on a polyolefin sheet has an essential drawback of poor anchoring properties, and as a means to improve this, a polyolefin sheet with surface oxidation treatment is used and a pressure-sensitive adhesive layer is used. Attempts have been made to improve anchoring properties by introducing functionality such as carboxyl groups, and efforts have been made to use catalysts from cross-linking agents used in pressure-sensitive adhesives as primers, but there are still insufficient results. The reality is that satisfactory results have not been obtained.As a result of extensive research into improving the anchoring properties of polyolefin sheets and pressure-sensitive adhesive layers, the present inventors have found that polyolefin sheets with surface oxidation treatment are supported. The inventors have discovered that anchoring properties can be significantly improved by irradiating ionizing radiation with a specific polymerizable compound present at the interface between the sheet and the pressure-sensitive adhesive layer, leading to the present invention. It is something that

That is, in the present invention, a liquid hexapolymerizable compound having at least one (meth)acryloyl group in the molecule is applied to the treated surface of a polyolefin sheet subjected to surface oxidation treatment, and a pressure-sensitive adhesive is applied thereon. The present invention relates to a method for producing pressure-sensitive adhesive tapes, which comprises irradiating ionizing radiation after coating and drying.

The polyolefin sheet used in the present invention is polyolefin, polyethylene, polypropylene, poly(1-butene), or vinyl acetate, (meth)acrylic acid, (meth)
A sheet of polymer made by copolymerizing or graft polymerizing a polymerizable monomer such as an acrylic acid alkyl ester can be used, and the surface oxidation treatment of the sheet may include corona treatment, flame treatment, chemical oxidation treatment, etc. Polymerizable compounds having at least one (meth)acryloyl group in the molecule include (meth)acrylic acid which is liquid or semi-solid at room temperature. Various derivatives are used, such as 2-ethylhexyl (meth)acrylate, 1.4
-Butylene glycol di(meth)acrylate, ■・6
- (meth)acrylic acid ester monomers such as hexagelicol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethanetetra(meth)acrylate, or epoxy ( Examples include oligomers such as meth)acrylate, urethane(meth)acrylate, and oligoester(meth)acrylate.
These may be used in combination of two or more types as required, or may be used as a solution using an appropriate solvent.

(The pressure-sensitive adhesive used in the present invention includes various commonly used solvent-based or aqueous-based natural rubber or 1-inch synthetic rubber-based pressure-sensitive adhesives, acrylic-based pressure-sensitive adhesives, etc.) According to the present invention, a crosslinking agent is added to
It is particularly useful for aqueous dispersions such as JaL, emacylin, and dispersion, which are difficult to anchor, but it can also improve anchoring for solvent-based systems.

The reason why the anchoring effect is exhibited in the present invention is not clear, but the surface of the polyolefin sheet subjected to surface oxidation treatment is more activated by irradiation with ionizing radiation, and some chemical bond is formed between it and the polymerizable compound. It is presumed that good anchoring properties are produced by the reaction of the polymerizable compound with the pressure-sensitive adhesive.

To show a specific method for implementing the present invention, first, a polyolefin sheet whose surface has been oxidized is prepared, and the polymerizable compound liquid is applied to the treated surface to a thickness of 0.5 to 5 μm after drying.
After applying a pressure-sensitive adhesive on top of it to a dry thickness of 5 to 50 μm, it is coated with ionizing radiation such as electron beams, γ-rays, χ-rays, β-rays, etc. 1~5M
By irradiating with rad, a pressure-sensitive adhesive sheet with very good anchoring properties between the polyolefin sheet and the pressure-sensitive adhesive layer and having stable adhesive force and cohesive force can be obtained.Hereinafter, the present invention will be explained in detail with reference to examples. However, it is not limited to these examples 〇 In the following, parts mean parts by weight, and the adhesive strength and anchoring force tests were measured using the following methods. be.

[Adhesive strength]

The prepared pressure-sensitive adhesive tape sample was cut to a width of 2Q mm, pasted on a degreased SNS, 304 stainless steel plate, left for 30 minutes, and then peeled off at 180 degrees. Adhesive strength (peeling speed: 300ff15), 20°C x 65% R , H, ).

[Anchoring power]

The adhesive surfaces of the produced pressure-sensitive adhesive tape samples were rapidly attached and separated, and a case where the adhesive layer did not peel off from the support sheet was evaluated as good.

Production Example 1 "Production of pressure-sensitive adhesive CI)" 80 parts of 2-ethylhexyl acrylate,
20 parts of methyl methacrylate, 5 parts of acrylic acid, 5 parts of polyoxyethylenealkylphenol 1-methyl, and 160 parts of ion-exchanged water were charged and heated while stirring under a nitrogen stream, and when the reaction system reached about 60°C. Then, 0.3 part of ammonium persulfate was added as a polymerization initiator to start the polymerization, and the polymerization reaction was carried out for about 3 hours.
The reaction system was heated to 50°C and aged for about 1 hour to obtain an emulgitane composition containing a copolymer. An emulsion-type pressure-sensitive adhesive having a viscosity of about 5 poise (at 20° C.) was prepared by dropping an approximately 3% ammonia aqueous solution into the emulsion composition while stirring.

Production Example 2 "Production of pressure-sensitive adhesive (fl)" Into a reaction vessel similar to GLV Preparation Example R, 75 parts of butyl acrylate, 25 parts of vinyl acetate, 3 parts of methacrylic acid, 0.2 part of benzoyl peroxide, and 100 parts of ethyl acetate was charged and a polymerization reaction was carried out at about 65° C. for 4 hours to produce a solvent-type pressure-sensitive adhesive containing a copolymer.

Example 1 One portion of trimethylolpropane triacrylate was applied to the treated surface of a 60 μm thick corona-treated polyethylene sheet.
The pressure-sensitive adhesive (J) obtained in Production Example 1 was applied on top of it to a thickness of 20 μm, and then heated and dried at 90°C for 3 minutes. An original tape was obtained.

Next, the adhesive surface of the original tape was irradiated with 2 Mrad of electron beams generated by a curtain beam type electron beam irradiation device with a maximum acceleration voltage of 165 KV at an oxygen concentration of 1000 pl; 1 m or less to form a pressure-sensitive adhesive tape. A sample was prepared.

Example 2 A 30% solution of tetramethylolmethanetetraacrylate in ethyl acetate was applied to the treated surface of a 60 μm thick corona-treated polypropylene sheet to a thickness of 4 μm,
The pressure-sensitive adhesive (II) obtained in Production Example 2 was applied thereon to a dry thickness of 20 μm, and dried at 100° C. for 3 minutes to obtain an original tape.

Next, an electron beam generated by the same electron beam irradiation device as in Example 1 was applied to the adhesive surface of the original tape at 3 Mra.
Comparative Example 1 The pressure-sensitive adhesive CI) of Production Example 1 was applied to the corona-treated surface of the same polyethylene sheet as in Example 1 to a thickness of 20 mm after drying.
μm, heat-dried at 90°C for 3 minutes, and then irradiated with an electron beam under the same conditions as Example 1 to create a tape sample.0 Comparative Example 2 A polyethylene sheet similar to Example 1 was coated. Trimethylolpropane triarylate was applied to the corona-treated surface to a thickness of 1 μm, and irradiated with an electron beam under the same conditions as in Example 1. Next, the pressure-sensitive adhesive (I) of Production Example 1 was applied to the coated irradiated surface so that the thickness after drying was 20 μm, and the tape sample was prepared by heating and drying at 90° C. for 3 minutes. Table 1 shows the results of testing the adhesive strength and anchoring strength of the pressure-sensitive adhesive tape samples of Examples 1 and 2 and Comparative Examples 1 and 2.

Chapter 1 Table patent applicant Nitto Electric Industry Co., Ltd. Representative Sanbe Hijikata

Claims (1)

[Claims] A liquid polymerizable compound having at least one (meth)acryloyl group in the molecule is applied to the treated surface of the polyolefin sheet, which has undergone surface oxidation treatment, and then a pressure-sensitive adhesive is applied thereto. After drying, the ionizable Method for producing pressure-sensitive adhesive tapes characterized by irradiation with radiation =