JPH09125019A - Tacky sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a tacky sheet, capable of manifesting a high interlaminar adhesive strength, readily peelable after temporary tacking without any residual paste, excellent in weather and oil resistances and useful for surface protection of a steel sheet, etc., by melt coating a substrate layer with a tacky agent layer comprising a specific block copolymer. SOLUTION: This tacky sheet is obtained by melt coating (A) a substrate layer with (B) a block copolymer of the formula (A-B-A)n [A is a vinylic polymer block formed of, e.g. a monomer having vinyl group and >=20 deg.C glass transition temperature of a homopolymer thereof, especially styrene or methyl methacrylate; B is a (co)polymer block containing a 1-12C alkyl (meth)acrylate, having, e.g. <=0 deg.C glass transition temperature and prepared by, as necessary, copolymerizing a polar monomer such as acrylic acid] or the formula (A-B)n .

Description

Detailed Description of the Invention

[0001]

The present invention relates to a pressure-sensitive adhesive sheet,
More specifically, it relates to an adhesive sheet suitable for an adhesive label.

[0002]

2. Description of the Related Art Conventionally, all pressure-sensitive adhesive sheets are manufactured by providing a pressure-sensitive adhesive layer on a substrate sheet via a primer layer or directly. As a method of providing a pressure-sensitive adhesive layer on the substrate, after applying a solution of the pressure-sensitive adhesive dissolved in a solvent,
A solution coating method in which a solvent is heated and dried to remove the solvent, and an emulsion coating method in which an emulsion-type pressure-sensitive adhesive is used, such as a method of producing a pressure-sensitive adhesive by an emulsion polymerization method, are widely adopted. In the former case, there is a demand for desolvation due to the influence of the organic solvent on the environment, and in the latter case, there is a problem in that the drying speed has a facility limit and wastewater treatment and drying energy are large. A so-called hot melt coating method, in which a pressure-sensitive adhesive is melted by heating and coated on a substrate, as disclosed in Japanese Patent Laid-Open No. 6-41501, has been adopted.

In Japanese Patent Laid-Open No. 6-41501 mentioned above, 1
A steam container in which an acrylic resin solution containing 5 to 85% by weight of a volatile component is heated to a temperature above the boiling point of the volatile component in a heating tube, the temperature of the wall surface is maintained at 50 to 200 ° C., and the internal pressure is maintained at 200 Torr or less. A step of ejecting the acrylic resin and a volatile component into the inside, and a step of transferring the acrylic resin staying at the bottom of the vapor container to a hot melt coater without cooling and applying it on a sheet-like material A method for producing a sheet-like material coated with an acrylic hot-melt pressure-sensitive adhesive having a is disclosed.

Further, Japanese Patent Publication No. 51-48773 discloses that
A base material layer selected from polyethylene and polypropylene, an ethylene-ethyl acrylate-based copolymer intermediate layer,
Also disclosed is a method for producing a pressure-sensitive adhesive sheet in which an acrylic acid ester-based copolymer pressure-sensitive adhesive layer is extruded by a melt coextrusion method, and these layers are integrally laminated and adhered while in a molten state.

However, the pressure-sensitive adhesive layer disclosed in JP-A-6-41501 and JP-B-51-48773 is composed of a general (meth) acrylic acid ester-based copolymer, Medium, adhesive tapes obtained by hot-melt coating or coextrusion molding of random copolymers, after temporarily adhering to the adherend, remarkably accelerate adhesion at room temperature or after heating, making it difficult to re-peel and become a surface protective adhesive sheet. It has a problem that it cannot be used for typical re-peeling applications.

Further, in JP-A-61-1103975, 100 parts by weight of ABA (where A is a styrene polymer block and B is a copolymer block of ethylene and butylene) is used. An adhesive film for surface protection is disclosed in which an adhesive layer made of a composition containing 0 to 80 parts by weight of a tackifying resin is formed on a polyolefin resin film. However, all of the pressure-sensitive adhesive layers disclosed in JP-A-61-1103975 are inferior in weather resistance and oil resistance, and cannot be used for applications exposed to the outdoors or applications exposed to oil. It has a problem.

The present inventor diligently studied a coating method of an acrylic pressure-sensitive adhesive, and the acrylic pressure-sensitive adhesive changes various adhesive properties depending on the coating method, but when a specific acrylic pressure-sensitive adhesive is melt-coated. Only while maintaining the required adhesive strength,
The inventors have found that they exhibit excellent removability, and have completed the present invention.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above facts, and an object of the present invention is to enable easy peeling without adhesive residue after temporary attachment to an adherend and weather resistance. An object is to provide a pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer having excellent properties and oil resistance.

[0009]

The present invention according to claim 1 is characterized in that the base material layer has a general formula (A-B-A) _n or a general formula (A-B) _n [wherein A is a vinyl-based compound]. Polymer block, B
Is a polymer or copolymer block containing a (meth) acrylic acid ester having an alkyl group having 1 to 12 carbon atoms as a constituent unit, and n is an integer of 1 to 10]. The gist of the present invention is a pressure-sensitive adhesive sheet characterized in that an agent layer is melt-coated.

The present invention according to claim 2 is characterized in that the pressure-sensitive adhesive sheet according to claim 1 is used for surface protection.

A primer layer may be provided on the base material layer if necessary, but the means for melt-coating the base material layer with the primer layer and the pressure-sensitive adhesive layer is not particularly limited. For example, a method in which the above three layers are coextruded using a multi-layer extruder, a method in which a hot melt coater is used to apply a pressure-sensitive adhesive in a molten state onto a base material provided with a primer layer, and a pressure-sensitive adhesive layer is provided. Etc.

The substrate sheet constituting the above-mentioned substrate layer is not particularly limited, but for example, polyolefin-based such as low density polyethylene, medium density polyethylene, high density polyethylene, linear low density polyethylene, polypropylene and the like. Examples thereof include a thermoplastic resin film and a polyester resin film such as polyethylene terephthalate. However, a resin film that is modified with a highly polar monomer such as acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, acrylamide, β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, etc., and the surface of which is too active is blocked during winding. It is not preferable because it may cause The base material layer may be composed of a single resin, but may be a film in which two or more types of polyolefin-based thermoplastic resins are mixed.
Also, these films may be used as a single layer, but
It may be used as a composite film in which one or more films are laminated. The thickness of the base material layer is appropriately set depending on the use of the product pressure-sensitive adhesive sheet, but is generally 10 to 80 μm.
The degree is generalized.

The primer layer is not particularly limited, but when the pressure-sensitive adhesive sheet is manufactured by a coextrusion molding method, the primer may be a low density polyethylene, a medium density polyethylene, a high density polyethylene or a linear shape. Low density polyethylene, ethylene-α olefin copolymer,
Propylene-α olefin copolymer, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-methyl methacrylate copolymer, ethylene-n-butyl acrylate copolymer, polypropylene (homopolymer, random copolymer, block Copolymer) and the like, but among them, a polyolefin thermoplastic resin in which a polar group-containing comonomer is copolymerized or grafted, for example, a terpolymer in which ethylene-ethyl acrylate and maleic anhydride are copolymerized is preferable. Used for. In the case of the coextrusion molding method, the thickness of the primer layer is preferably about 3 to 20 μm.

When the pressure sensitive adhesive sheet is produced by the hot melt coating method, a primer layer may be provided as described above, but the surface of the base material layer coated with the pressure sensitive adhesive is subjected to surface activation such as corona discharge treatment. By adopting such a method, the anchoring force between the base material layer and the pressure-sensitive adhesive layer can be improved.

The above-mentioned adhesive has the general formula (A-B-A) _n or (A-B) _n [wherein A is a vinyl polymer block and B is an alkyl group having 1 to 12 carbon atoms]. A polymer or copolymer block containing (meth) acrylic acid ester as a constituent unit, n is an integer of 1 to 10],
Includes linear or star block polymers or copolymers. However, regarding the star shape, the A block may be inside and the B block may be inside. The vinyl compound forming the A block is preferably a homopolymer having a vinyl group having a Tg ≧ 20 ° C., for example, styrene, methyl methacrylate, α-methyl styrene, o-methyl styrene, p-methyl styrene. , Ethyl methacrylate, acrylonitrile, vinyl acetate and the like can be mentioned, but styrene or methyl methacrylate is preferably used.

The polymer or copolymer forming the B block preferably has Tg ≦ 0 ° C., for example,
The copolymer which has a (meth) acrylic acid ester as a main component is mentioned. Examples of the (meth) acrylic acid ester include ethyl acrylate, n-butyl acrylate, iso-butyl acrylate, ter-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, lauryl acrylate, n-octyl methacrylate, 2- Ethylhexyl methacrylate, lauryl methacrylate, etc. can be mentioned.
Species or two or more species are used.

The B block polymer or copolymer is
In order to balance the tackiness and adhesive strength, if necessary,
Polar monomers such as acrylic acid, methacrylic acid, maleic anhydride, itaconic acid, acrylamide, β-hydroxyethyl acrylate and β-hydroxyethyl methacrylate may be copolymerized.

The method for adjusting the above-mentioned pressure-sensitive adhesive is not particularly limited, but, for example, first, a monomer constituting the B block and a radical initiator containing a bifunctional or more functional peroxide group in one molecule are heated. Polymerize the B block by heating at level 1 and then add the monomers that make up the A block. Temperature level 2 (higher than temperature level 1)
(AB) _n type block copolymer is prepared by heating and reacting with. As another method, first, a monomer constituting the B block is mixed with N, N-diethyldithiocarbamate, and after purging the inside of the reaction vessel with nitrogen,
The B block is polymerized by UV irradiation with an ultraviolet (UV) lamp. Next, the monomer that constitutes the A block is added,
Further UV irradiation to polymerize the A block, (A-B-A)
_{An n-} type block copolymer is prepared. In addition, a polymerization method using a polymerization initiator such as an azo compound initiator and a redox initiator may be used.

If necessary, a tackifying resin, a filler, an antioxidant, an ultraviolet absorber, a crosslinking agent such as a carboxylic acid metal salt may be added to the above-mentioned pressure-sensitive adhesive.

Examples of the tackifying resin include C ₅
System and C ₉ series (hydrogenated) petroleum resin, (hydrogenated) rosin resin,
(Hydrogenated) rosin ester resin, (hydrogenated) terpene resin,
(Hydrogenated) terpene phenolic resin, (hydrogenated) coumarone
Examples thereof include indene resin, disproportionated rosin resin, disproportionated rosin ester resin, polymerized rosin resin, and polymerized rosin ester resin. The tackifier resins may be used alone or in combination of two or more.

The thickness of the pressure-sensitive adhesive layer is appropriately set depending on the use of the product pressure-sensitive adhesive sheet, but is generally 3 to 30 μm.
m is generally used.

In the method for producing a pressure-sensitive adhesive sheet of the present invention, the above-mentioned pressure-sensitive adhesive layer is melt-coated on the substrate layer, but the melt-coating method is not particularly limited. As a method of melt coating, for example, when the pressure-sensitive adhesive layer is integrally manufactured with a base material layer and, if necessary, a co-extrusion molding method together with a primer layer, the base material layer, the pressure-sensitive adhesive layer and the primer are used. Each layer is plasticized by a separate extruder and coextruded by a hot-melt method using a multi-layer extrusion die such as an inflation method or a T-die method,
A pressure-sensitive adhesive sheet in which a base material layer / a primer layer / a pressure-sensitive adhesive layer are laminated in this order can be easily manufactured.

When manufacturing by the hot melt coating method, a primer layer is formed on one surface of the base material layer in advance by an appropriate method, and the primer layer is melt-coated with a hot melt coater to obtain an adhesive property. The sheet can be easily manufactured.

Further, the laminate of the base material layer / primer layer / adhesive layer formed by the above-mentioned melt coating is further irradiated with an appropriate amount of electron beam or the like to obtain the degree of crosslinking of the adhesive layer and the inter-layers. You may improve the anchoring power.

Since the pressure-sensitive adhesive sheet of the present invention is constructed as described above, after it is temporarily adhered to an adherend, a remarkable increase in adhesion
In particular, the adhesion does not accelerate with heating, and when peeled from the adherend, it can be easily peeled without damaging the adherend, and no adhesive residue is left on the adherend. Further, in the method of forming each of the base material layer / primer layer / adhesive layer by the co-extrusion method, since an extra man-hour is not required to form the primer layer, it contributes to cost reduction,
In addition, it exhibits strong interlayer adhesion strength. Furthermore, the pressure-sensitive adhesive sheet of the present invention comprises a base material layer made of a polyolefin-based thermoplastic resin which is not modified with a highly polar monomer,
When the pressure-sensitive adhesive sheet rolled into a roll is used, it is extremely easy to unwind and develop. Further, the pressure-sensitive adhesive sheet of the present invention is also excellent in oil resistance and weather resistance, so for surface protection, in particular, the pressure-sensitive adhesive sheet is applied to the surface of an adherend such as surface-treated steel plate, stainless steel plate, synthetic resin plate, etc. It can be suitably provided for applications such as surface protection where mechanical processing such as bending, drawing, and cutting is performed as it is attached.

[0026]

Embodiments of the present invention will be described below. (Example 1) General formula (A-B-A) _n prepared by the UV polymerization method [A is a methyl methacrylate polymer block, B is a copolymer block of ethyl acrylate and acrylic acid, A content Is 30% by weight, the acrylic acid content in the B block is 1% by weight,
Flow tester at ℃ (Shimadzu Corporation, trade name: CF
T-500) has an acrylic block copolymer having a viscosity of 220,000 cps] as a pressure-sensitive adhesive layer (shown in Table 1) as low-density polyethylene (Mitsui Petrochemical Co., Ltd., trade name: Mirason 12). As a base material layer, ethylene / ethyl acrylate / maleic anhydride terpolymer (manufactured by Sumitomo Chemical Co., Ltd., trade name: Bondine Tx803
0, ethyl acrylate and maleic anhydride comonomer content 15% by weight) are used as the primer layer, and the mold temperature is set by the T-die method so that a laminate of base material layer / primer layer / adhesive layer is formed. By co-extruding at 180 ° C., the substrate layer thickness is 50 μm, the primer layer thickness is 7
A pressure-sensitive adhesive sheet having a thickness of 5 μm and a pressure-sensitive adhesive layer having a thickness of 5 μm was produced.

Example 2 The content of A in the pressure-sensitive adhesive layer was 20.
A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that the acrylic block copolymer (shown in Table 1) having a weight% and a viscosity at 180 ° C. of 200,000 cps was used.

(Example 3) A polyethylene terephthalate film (manufactured by Teijin Ltd., trade name: Tetron Film SC) having a thickness of 38 μm, which was subjected to corona discharge treatment on one side, was used as a base material layer.
On the corona discharge treated surface of the base material layer, the hot melt coater (YURIRO) using the acrylic block copolymer of the general formula (ABA) _n used in Example 1 as an adhesive layer
A hot melt coating was performed at a mold temperature of 180 ° C. by LLMACHINE) to prepare an adhesive sheet.

Comparative Example 1 An acrylic random copolymer (shown in Table 1) consisting of 30% by weight of methyl methacrylate, 69% by weight of ethyl acrylate and 1% by weight of acrylic acid was used as an adhesive. Example 1
In the same manner as above, co-extrusion was carried out by the T-die method to produce an adhesive sheet.

Comparative Example 2 A pressure-sensitive adhesive sheet was prepared by the hot melt coating method in the same manner as in Example 3 except that the acrylic random copolymer used in Comparative Example 1 was used.

In order to evaluate the pressure-sensitive adhesive sheets obtained in the above Examples and Comparative Examples, the initial pressure-sensitive adhesive force and the time-dependent pressure-sensitive adhesive force-1
(23 ° C x 14 days), adhesive strength over time-2 (40 ° C x 14 days
Day) and the amount of glue remaining at each measurement, measured by the following method,
evaluated. The measurement and evaluation results are shown in Table 1.

Initial Adhesion Strength: According to JIS Z 0237 (adhesive tape / adhesive sheet test method), a test piece aged one day after production was tested at a temperature of 23 ° C. with a pressure roller of 2 kg to obtain a stainless steel test plate. The tape was attached to the surface and peeled off by 180 ° at a pulling speed of 300 mm / min to measure the adhesive strength as the initial adhesive strength. After the above peeling test, the presence or absence of adhesive residue of the pressure-sensitive adhesive layer on the surface of the stainless steel plate was evaluated in two stages of ◯: no adhesive residue and ×: adhesive residue present. A lot of comments were added.

Adhesion with time -1 (23 ° C x 14 days): J
According to IS Z 0237, the test piece aged 1 day after production was tested at 23 ° C. × 14 days, and the
The 0 ° peeling adhesion was measured as the initial adhesion. After the above peeling test, the presence or absence of adhesive residue of the pressure-sensitive adhesive layer on the surface of the stainless steel plate was evaluated in two stages of ◯: no adhesive residue and ×: adhesive residue present. A lot of comments were added.

Adhesion with time-2 (40 ° C. × 14 days): J
According to IS Z 0237, in the same manner as in the previous section, the test piece aged 1 day after production was tested at 40 ° C. × 18 days after a lapse of 18 days.
The 0 ° peeling adhesion was measured as the initial adhesion. After the above peeling test, the presence or absence of adhesive residue of the pressure-sensitive adhesive layer on the surface of the stainless steel plate was evaluated in two stages of ◯: no adhesive residue and ×: adhesive residue present. A lot of comments were added.

[0035]

[Table 1]

As is clear from Table 1, the adhesive sheets of the examples were not peeled off from the adherend even after being attached to the adherend and after heating for a long time, no remarkable progress of adhesion occurred. Sometimes there is no adhesive residue on the adherend. In contrast,
In each pressure-sensitive adhesive sheet of the comparative example, the monomer composition of the acrylic copolymer of the pressure-sensitive adhesive layer is the same as that of the example, and is only the difference between the random copolymer and the block copolymer. However, significant adhesion progress occurs over time and heating. In the coating method using an organic solvent solution of the acrylic copolymer, adhesion progress has been conventionally observed. Therefore, as described above, the structural difference of the acrylic copolymer constituting the pressure-sensitive adhesive and the melt coating of the coating method are used. It is presumed that the effect of the present invention can be achieved only by the combination of

[0037]

EFFECT OF THE INVENTION Since the pressure-sensitive adhesive sheet of the present invention is constructed as described above, after it is temporarily adhered to an adherend, significant adhesion progress, especially adhesion progress over heating, does not occur, and When peeling, without damaging the adherend,
It can be easily peeled off, and no adhesive residue is left on the adherend.
Further, in the method of forming each of the base material layer / primer layer / adhesive layer by the co-extrusion method, an extra man-hour is not required to form the primer layer, which contributes to cost reduction and is robust. The interlayer adhesion strength is shown. Further, the pressure-sensitive adhesive sheet of the present invention, when the base material layer is a polyolefin-based thermoplastic resin which has not been modified with a highly polar monomer, the pressure-sensitive adhesive sheet wound in a roll shape can be unrolled and developed at the time of use. It's extremely easy. Further, the pressure-sensitive adhesive sheet of the present invention is also excellent in oil resistance and weather resistance, so for surface protection, in particular, the pressure-sensitive adhesive sheet is applied to the surface of an adherend such as surface-treated steel plate, stainless steel plate, synthetic resin plate, etc. It can be suitably provided for applications such as surface protection where mechanical processing such as bending, drawing, and cutting is performed as it is attached.

Claims (2)

[Claims] 1. A base material layer comprising a general formula (A-B-A) _n or a general formula (A-B) _n [wherein A is a vinyl-based polymer block and B is a C1-C12). A pressure-sensitive adhesive layer made of a block copolymer represented by a polymer or a copolymer block containing (meth) acrylic acid ester having an alkyl group as a constitutional unit, and n is an integer of 1 to 10 is melt-coated. Adhesive sheet characterized by being. 2. The pressure-sensitive adhesive sheet according to claim 1, which is used for surface protection.