JPH10120019A - Wrapping material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To seal satisfactorily by adhesion even at low temperature and with low pressure, achieve excellent adhesion which resists peeling even if stress is applied and is excellent in seal maintenance, cope with various use conditions and reduce necessary kinds, by positioning a pressure-sensitive adhesive layer with a high elastic modulus on the surface side. SOLUTION: In the formation of a wrapping material in which a superimposition layer 1, pressure-sensitive adhesive layer, is firmly attached and fixed onto a support base material 2, the superimposition layer 1 consists of two layers, upper and lower, obtained by a combination of pressure-sensitive adhesive layers of different elastic moduli. In the pressure-sensitive adhesive superimposition layer 1, the pressure-sensitive adhesive layer 11 with high elastic modulus is arranged on the surface side. A difference in elastic modulus between the pressure-sensitive adhesive layer 11 situated on the surface side and the pressure-sensitive adhesive layer 12 as the lower layer is determined as necessary according to use purpose, etc. However, generally, it is preferable that the difference be 1.5 or more times, especially 1.7-10 times, and, in particular, 1.9-5 times. As the elastic modulus of the pressure-sensitive adhesive layer 12 being the lower layer, 1-10gf/mm<2> , especially 1.5-8gf/mm<2> , and particularly 2-5gf/mm<2> are general. However, without being limited to this, it is determined properly according to adhesive force and so on to a body to which it is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive tape type packaging material which can be bonded at a low pressure even at a low temperature, maintains its bonding state well even under stress, and is hardly peeled off.

[0002]

BACKGROUND OF THE INVENTION In a packaging material in which a pressure-sensitive adhesive layer is provided on a supporting base material, atmospheres such as climatic conditions are greatly changed spatially and seasonally, for example, in the operation of sealing and storing cardboard boxes. In the summer and summer, where the temperature can exceed 30 ° C and in the winter when the temperature can reach 0 ° C or less, the packaging materials become more diversified and the usage becomes more complicated. It is required to be able to cope with a wide range of usage conditions, such as a year-round type that does not need to be used properly.As a material exhibiting such new adhesive properties, a good adhesive seal that does not peel off with low pressure bonding even at low temperatures has been achieved. The development of what can be done is being attempted.

[0003] In a conventional packaging material which is set to have a high adhesive strength by a high elastic pressure-sensitive adhesive layer having an elastomer made of a block copolymer such as styrene / isoprene / styrene copolymer as a base polymer, stress concentration due to high elastic modulus and the like is caused. For low pressure bonding, the adhesive seal is easily peeled off due to the opening habit of the flap of the cardboard box, etc., and a pressure treatment with a strong pressing force is required for the bonding process, so the work becomes heavy labor and the burden on the operator is large. was there.

In view of the above, there has been proposed a structure in which a low-modulus pressure-sensitive adhesive layer is provided on a high-modulus pressure-sensitive adhesive layer based on creep compliance (Japanese Patent Publication No. 61-34).
760). However, the low pressure bonding and sealing properties at low temperatures are the same as the above-mentioned conventional products, and there is a problem that a strong pressing force is required for the bonding process. When a strong pressing force is required for the bonding process, there is also a disadvantage that the reliability in the case of performing mechanical processing such as a sealing process of a cardboard box is poor.

[0005]

SUMMARY OF THE INVENTION The present invention provides a good adhesive seal even when sealing a cardboard box or the like under a low pressure at a low temperature and at a low pressure. It is an object of the present invention to develop a packaging material capable of coping with the problem and reducing the variety.

[0006]

According to the present invention, a superposed layer comprising two pressure-sensitive adhesive layers having different elastic moduli is closely fixed on a supporting base material, and the pressure-sensitive superposed layer having a high elastic modulus in the superposed layer is provided. An object of the present invention is to provide a packaging material characterized in that the adhesive layer is located on the surface side.

[0007]

According to the above-mentioned packaging material, it is possible to achieve good adhesion and sealing at a low pressure even at a low temperature, and it is possible to achieve an adhesion treatment which is hard to be peeled off even when a stress acts and is excellent in maintaining the seal. It is possible to cope with the use conditions and to reduce the required variety. It is not clear why the above-described configuration in which the low elastic modulus layer is disposed below the high elastic modulus layer improves the adhesive properties at low temperature and low pressure.

The peeling phenomenon of the adhesive seal is an interface phenomenon between the adherend and the packaging material. If the peeling is caused by the stress generated in the packaging material through the adherend, for example, the above-mentioned Japanese Patent Publication No. Sho 61 As taught by JP-A-34760, it is advantageous to use a pressure-sensitive adhesive layer which is easy to relieve the stress and thus has a low elastic modulus on the surface side. Until now, it has been considered that it is advantageous to provide a low-modulus pressure-sensitive adhesive layer on the surface side, which is easy to use. It is against the idea. Therefore, the mechanism of developing good adhesive seal characteristics by low-pressure treatment at a low temperature based on the configuration of the present invention cannot be explained by the conventional idea, and is currently unknown.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The packaging material of the present invention has a superposed layer composed of two upper and lower pressure-sensitive adhesive layers having different elastic moduli adhered and fixed on a supporting base material. The high pressure-sensitive adhesive layer is located on the front side. An example is shown in FIG. 1 is a superposed layer of a pressure-sensitive adhesive layer composed of a pressure-sensitive adhesive layer 11 having a high modulus of elasticity and a pressure-sensitive adhesive layer 12 having a low modulus of elasticity, 2 is a supporting substrate, and 21 is a release coat layer provided as necessary. It is.

In the present invention, the pressure-sensitive adhesive layer is formed as a superposed layer having different elastic moduli, and an appropriate pressure-sensitive adhesive can be used for forming the pressure-sensitive adhesive layer. There is no limitation. Incidentally, examples of the pressure-sensitive adhesive include various pressure-sensitive adhesives such as rubber-based, acrylic-based, silicone-based and urethane-based, vinylalkyl ether-based and polyvinyl alcohol-based, polyvinylpyrrolidone-based, polyacrylamide-based, and cellulose-based adhesives. Can be Generally, a rubber-based or acrylic pressure-sensitive adhesive is used. The pressure-sensitive adhesive layers forming the superposed layers can be of the same or different suitable combinations.

Examples of the rubber-based pressure-sensitive adhesive include natural rubber, polyisoprene rubber, styrene / isoprene / styrene block copolymer rubber, styrene / butadiene / styrene block copolymer rubber, recycled rubber and styrene.・ Butadiene rubber, polyisobutylene and NBR
And those using a rubber-based polymer as a base polymer.

In particular, styrene such as styrene / isoprene / styrene block copolymer rubber, styrene / butadiene / styrene block copolymer rubber, styrene / ethylene / butylene / styrene block copolymer rubber and styrene / butadiene copolymer rubber A pressure-sensitive adhesive having an elastomer composed of a base copolymer as a base polymer can be preferably used for forming a pressure-sensitive adhesive layer located on the surface side with respect to its high elastic modulus.

The weight average molecular weight of the base polymer is:
300,000 or more from the point of cohesion and adhesive strength
Million, particularly preferably 32-1.5 million. The molecular weight can be adjusted appropriately by controlling the mixing time of the mastication, the mastication time with a roll, and the amount of the mastication accelerator. The cohesive force of the rubber-based pressure-sensitive adhesive layer can be controlled by an appropriate crosslinking treatment such as vulcanization of turam or vulcanization of phenol resin.

On the other hand, any known acrylic pressure-sensitive adhesive can be used. Above all, from the viewpoint of pressure-sensitive adhesive properties and the like, methyl, ethyl, n-propyl and isopropyl, n-butyl and t-butyl, isobutyl and amyl, isoamyl and hexyl, heptyl Group, cyclohexyl group, 2-ethylhexyl group or octyl group,
Isooctyl group and nonyl group, isononyl group and decyl group,
1 carbon atoms such as undecyl, lauryl, tridecyl, tetradecyl, stearyl and octadecyl
It is preferable that the base polymer is an acrylic polymer using one or two or more acrylic acid alkyl esters composed of acrylic acid or methacrylic acid esters having from 18 to 18 linear or branched alkyl groups.

The acrylic polymer has a weight average molecular weight of 200,000 or more, especially 2
53 to 3,000,000, particularly preferably 300 to 2,000,000,
Improve adhesive properties by introducing functional groups and polar groups as necessary, improve cohesive strength and heat resistance by controlling the glass transition temperature of the resulting copolymer, and increase pressure-sensitive adhesive properties such as increasing the molecular weight by crosslinking. For the purpose of modification or the like, one or two or more monomer components suitable for the purpose of modification other than the above-mentioned acrylic acid-based alkyl ester may be copolymerized.

Examples of the above-mentioned monomer components include acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, carboxyl group-containing monomers such as itaconic acid and maleic acid, fumaric acid and crotonic acid, or maleic anhydride and maleic anhydride. Acid anhydride monomers such as itaconic acid can be mentioned. Its usage is
From the viewpoint of the pressure-sensitive adhesive properties and the like, the amount is preferably 20 parts by weight or less, more preferably 15 parts by weight or less, per 100 parts by weight of the acrylic acid alkyl ester.

Also, 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate,
4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl)-
Hydroxyl group-containing monomers such as methyl acrylate, styrenesulfonic acid and allylsulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid and (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate and (meth) acryloyl Sulfonic acid group-containing monomers such as oxynaphthalenesulfonic acid, and phosphoric acid group-containing monomers such as 2-hydroxyethylacryloyl phosphate are also examples of the monomer component for the purpose of modification.

(N-substituted) such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane (meth) acrylamide Amide monomers, alkylaminoalkyl (meth) acrylate monomers such as aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, and t-butylaminoethyl (meth) acrylate; ) Alkoxyalkyl (meth) acrylate monomers such as methoxyethyl acrylate and ethoxyethyl (meth) acrylate, maleimide monomers such as N-cyclohexylmaleimide and N-isopropylmaleimide, N-laurylmaleimide and N-phenylmaleimide, N- Chill itaconic imide and N- ethyl itaconate imide, N- butyl itaconic imide and N- octyl itaconate imide, N-2-ethylhexyl itaconate imide or N- cyclohexyl itaconate imides, such as N- lauryl itaconic imide itaconimide monomers,
N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-
Succinimide monomers such as oxyoctamethylene succinimide are also examples of the monomer component for the purpose of modification.

In addition, vinyl acetate, vinyl propionate, N-vinylpyrrolidone, methylvinylpyrrolidone,
Vinyl monomers such as vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarboxylic acid amides, styrene, α-methylstyrene, N-vinylcaprolactam , Cyanoacrylate monomers such as acrylonitrile and methacrylonitrile, (meth)
Epoxy group-containing acrylic monomers such as glycidyl acrylate, and glycol-based acrylics such as polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate Ester monomers, acrylate monomers such as tetrahydrofurfuryl (meth) acrylate, fluorine (meth) acrylate, silicone (meth) acrylate and 2-methoxyethyl acrylate are also examples of the monomer component for the purpose of modification. The use amount of the above-mentioned monomer component for the purpose of modification is preferably 50 parts by weight or less per 100 parts by weight of the acrylic acid-based alkyl ester from the viewpoint of pressure-sensitive adhesive properties and the like.

The pressure-sensitive adhesive layer may have a crosslinked structure, if necessary, for the purpose of improving the pressure-sensitive adhesive properties by increasing the molecular weight of the base polymer or the like. The crosslinking method is not particularly limited, and any of known crosslinking methods can be employed. Incidentally, examples of the method include a method in which a polyfunctional monomer component having two or more unsaturated bonds in a molecule is copolymerized in an acrylic polymer and internally crosslinked, and a method in which the inside is exposed to radiation such as electron beams or ultraviolet rays. Examples of the method include cross-linking or external cross-linking, and a method in which a pressure-sensitive adhesive is mixed with a cross-linking agent to perform external cross-linking.

Examples of the above polyfunctional monomer component include 1,6-hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate and neopentyl. Glycol di (meth) acrylate, pentaerythritol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate and epoxy Examples include acrylate, polyester acrylate, urethane acrylate, 1,4-butyl diacrylate, 1,6-hexyl diacrylate, and the like.

The above-mentioned internal crosslinking method of the acrylic polymer requires the use of a polyfunctional monomer component. The preparation of the internally crosslinked acrylic polymer may be carried out by, for example, a radical polymerization method using a conventional thermal polymerization initiator or a photopolymerization method. It can be carried out by a radiation polymerization method using an initiator. In the case of an external cross-linking method using a cross-linking agent, radiation irradiation, or the like, a polyfunctional monomer component may be copolymerized in an acrylic polymer to improve cross-linking efficiency. One or more polyfunctional monomer components can be used. The compounding amount is 30% by weight or less of all monomer components, preferably 0.01 to 25% by weight, and particularly 0 to 25% by weight from the viewpoints of cross-linking efficiency, pressure-sensitive adhesive properties, acrylic properties such as transparency and weather resistance. .02-
10% by weight is preferred.

As the cross-linking agent used in the external cross-linking method, an appropriate one can be used, and there is no particular limitation.
Any known crosslinking agent used for intermolecular crosslinking of an acrylic polymer obtained by copolymerizing a functional group-containing monomer component such as a carboxyl group, an acid anhydride group, a hydroxyl group or an epoxy group can be used. Examples thereof include polyfunctional isocyanate crosslinking agents such as tolylene diisocyanate, trimethylolpropane tolylene diisocyanate, and diphenylmethane triisocyanate, and epoxy crosslinking agents such as polyethylene glycol diglycidyl ether and diglycidyl ether and trimethylolpropane triglycidyl ether. Is raised.

Also, a melamine resin-based crosslinking agent, a metal salt-based crosslinking agent, a metal chelate-based crosslinking agent, an amino resin-based crosslinking agent, a peroxide-based crosslinking agent, and the like can be used. The amount of the cross-linking agent used depends on the degree of cross-linking efficiency and pressure-sensitive adhesive properties.
20 parts by weight or less, preferably 15 parts by weight or less, particularly preferably 0.01 to 10 parts by weight, per 00 parts by weight.

The polymerization initiator optionally used in the case of radical polymerization of the acrylic polymer described above includes:
Any appropriate one can be used, and there is no particular limitation. Incidentally, examples thereof include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate and di (2-ethoxyethyl) peroxydicarbonate, t-butyl peroxy neodecarate, t-butyl peroxybivalate, (3,
Organic peroxides such as (5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide and diacetyl peroxide.

Also, 2,2′-azobisisobutyronitrile and 2,2′-azobis (2-methylbutyronitrile),
1'-azobis (cyclohexane 1-carbonitrile)
And 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethyl-4-methoxyvaleronitrile) and dimethyl 2,2′-azobis (2
-Methylpropionate), 4,4'-azobis (4-cyanovaleric acid) and 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis [2-
An azo compound such as (2-imidazolin-2-yl) propane], potassium persulfate, ammonium persulfate, hydrogen peroxide, or the like, or a redox initiator using a reducing agent in combination therewith, may be mentioned as the polymerization initiator.

On the other hand, as the photopolymerization initiator used as needed in the case of the polymerization treatment by radiation, an appropriate one can be used, and there is no particular limitation. Incidentally, examples thereof include benzoin ether compounds such as benzoin ethyl ether, benzoin isopropyl ether, and anisoin methyl ether, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, and 4- (2- (Hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone and α-hydroxy-
Examples include acetophenone-based compounds such as α, α′-dimethylacetophenone, methoxyacetophenone, 1-hydroxycyclohexylphenylphenone, and 2-methyl-1- [4- (methylthio) -phenyl] -2-morpholinopropane-1.

Also, α-ketol compounds such as 2-methyl-2-hydroxypropiophenone, ketal compounds such as benzyldimethyl ketal, aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride, 1-phenone- 1,1-propanedione-2-
Photoactive oxime compounds such as (ο-ethoxycarbonyl) oxime, benzophenone and benzoylbenzoic acid,
Benzophenone-based compounds such as 3,3'-dimethyl-4-methoxybenzophenone are also mentioned as examples of the photopolymerization initiator.

Further, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone Examples of photopolymerization initiators include thioxanthone compounds such as thioxanone and 2,4-diisopropylthioxanthone, camphorquinone, halogenated ketones, acylphosphinoxides, and acylphosphonates.

One or two or more polymerization initiators can be used. The amount of the polymerization initiator is determined in view of preventing unreacted monomer components from remaining and preventing cohesive strength from being reduced by reducing the molecular weight of the produced polymer. 0.01 to 10 parts by weight, preferably 0.02 to 5 parts by weight, particularly preferably 0.05 to 3 parts by weight, per 100 parts by weight of all monomer components.

In the case of the polymerization method using radiation, the photopolymerization initiator may be compounded in two or more portions, and the monomer may be prepolymerized or a mixture of the monomer component and the photopolymerization initiator may be added to the fumed silica. A thixotropic agent such as above is added to form a coatable syrup having a viscosity of about 500 to 5000 centipoise, which is applied to a separator or a support base material, and irradiated again with radiation to obtain a desired pressure-sensitive adhesive layer state. It can also be.

In forming the pressure-sensitive adhesive layer, if necessary, for example, natural or synthetic resins, tackifiers, plasticizers, softeners, glass fibers and glass beads, metal powders, calcium carbonate, clay and other materials Various additives that may be used in the pressure-sensitive adhesive, such as a filler composed of an inorganic powder and the like, a pigment, a colorant, an antioxidant, and the like, can be blended. Incidentally, the tackifier is useful for improving the adhesive strength. As the tackifier, an appropriate one may be used, and any of known materials may be used.

Examples of the tackifier include α-pinene and β
A terpene resin such as a pinene polymer, a diterpene polymer or an α-pinene-phenol copolymer, a petroleum resin such as an aliphatic petroleum resin or an aromatic petroleum resin, or an aliphatic / aromatic copolymer petroleum resin; And rosin-based resins, coumarone-indene-based resins, phenol-based resins, xylene-based resins, and alkyd-based resins.

The softening point is 60 ° C. or more, especially 70 to 170 ° C., particularly 80 to 150 ° C. in terms of pressure-sensitive adhesive properties at high temperatures.
In general, the tackifier may be preferably used. However, in order to maintain the adhesive strength at room temperature or improve the adhesive strength at a low temperature, a tackifier having a softening point of less than 60 ° C. may be used. The amount of the tackifier used is 5 to 200 parts by weight, especially 50 to 150 parts by weight, in the case of a rubber-based pressure-sensitive adhesive layer, per 100 parts by weight of the base polymer from the viewpoint of the balance between tack, adhesion and cohesion. In the case of an acrylic pressure-sensitive adhesive layer, the amount is preferably 100 parts by weight or less, particularly preferably 50 parts by weight or less, and in the latter case, it may not be added.

For the purpose of maintaining the adhesive strength at room temperature or improving the low-temperature adhesive strength, the use of a plasticizer or a softener is also useful. Any appropriate plasticizer or softener may be used, and any of known plasticizers and softeners may be used. In particular, a high-boiling substance having less volatilization in terms of storage stability and the like is preferably used.

Examples of plasticizers and softeners include dimethyl phthalate and diethyl phthalate, dibutyl phthalate and diheptyl phthalate, di-2-ethylhexyl phthalate and diisononyl phthalate, diisodecyl phthalate and dibutylbenzyl phthalate, Phthalic acid-based compounds such as dioctyl phthalate and butylphthalylbutyl glycolate; trimellitic acid-based compounds such as tributyl trimellitate, tri-2-ethylhexyl trimellitate, tri-n-octyl trimellitate and triisodecyl trimellitate , Polybutene, chlorinated paraffin, and polyisobutylene.

Also, dibutyl fumarate, dibutyl maleate, di-2-ethylhexyl maleate and diisobutyl adipate, diisononyl adipate and diisodecyl adipate, dibutoxyethyl adipate and dibutyl sebacate, and di-2-ethylhexyl sebacate Aliphatic dibasic acid ester-based compounds such as triethyl phosphate and triphenyl phosphate, tricresyl phosphate and trixylenyl phosphate, and cresyl phenyl phosphate; and diisodecyl-4,5-epoxytetrahydrophthalate Examples of plasticizers or softeners include epoxy compounds such as the above, low molecular weight compounds such as terpene resin, petroleum resin, and rosin acid resin, butyl oleate, and mineral oil.

The pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive in the form of a solution with an organic solvent, a dispersion or emulsion with water, or a mixture of monomer components, etc. onto a supporting substrate, followed by heat drying or radiation. It can be formed by an appropriate method according to the related art, such as a method of performing an irradiation treatment, or a method of transferring a pressure-sensitive adhesive layer formed on a separator onto a supporting substrate. Therefore, the superposed layer of the pressure-sensitive adhesive layer can also be formed by an appropriate method such as a multi-coating method or a transfer superposition method. From the viewpoint of the adhesion between the layers and the like, it is preferable to use a superposition method in a wet state by a recoating method or the like.

In the above case, when the coating layer of the pressure-sensitive adhesive is subjected to polymerization treatment by irradiation with radiation, for example, an air-blocking state such as a replacement atmosphere with an inert gas such as nitrogen gas or a covering state with a light-transmitting film is used. Is preferred from the viewpoint of the desired pressure-sensitive adhesive property. In the case of ultraviolet irradiation, electromagnetic radiation having a wavelength range of 180 to 460 nm is preferable from the viewpoint of processing efficiency and the like. Examples of the source include a mercury arc, a carbon arc, a (low, medium, high pressure) mercury lamp and a metal halide lamp. May be used. The irradiation amount can be appropriately determined according to the polymerization conditions and the like, but is usually about 400 to 3000 mj / cm ² .

In the present invention, when forming a packaging material in which the above-mentioned superposed layers of the pressure-sensitive adhesive layers are tightly fixed on a supporting base material, the upper and lower two layers composed of a combination of the pressure-sensitive adhesive layers having different elastic moduli are superposed. In the superposed pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer having a high elastic modulus is disposed on the surface side, that is, on the side to be adhered to the adherend. This makes it possible to provide pressure-sensitive adhesive properties that are difficult to peel off even in an adhesive treatment under low pressure at a low temperature.

In the above, the difference in elastic modulus between the pressure-sensitive adhesive layer located on the surface side and the pressure-sensitive adhesive layer therebelow can be appropriately determined according to the purpose of use and the like. 1.5 times or more, especially 1.7 to 10
It is preferable to have an elastic modulus difference of 1.9 to 5 times. The elastic modulus of the lower pressure-sensitive adhesive layer is 1 to 10 gf /
mm ^2, especially 1.5~8gf / mm ^2, particularly 2~5gf / mm ² is generally determined appropriately depending on the adhesion to the adherend is not limited thereto. The modulus of elasticity of the pressure-sensitive adhesive layer is based on stress at 100% tensile elongation at an average temperature in a temperature range of use such as room temperature (23 ° C.).

The thickness of the superimposed pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and the like, and is not particularly limited. The thickness can be more than 1 mm, but is generally 500 μm or less, and especially 3 to 300 μm. , Particularly 5 to 200 μm. In this case, the thickness of the pressure-sensitive adhesive layer located on the front surface side is 0.05 to 10 times the thickness of the lower pressure-sensitive adhesive layer, especially from the viewpoint of the good pressure-sensitive adhesive properties. 0.07 to 2 times, especially 0.1.
It is preferable to make it 1 to 0.5 times.

The supporting substrate for tightly fixing the superposed pressure-sensitive adhesive layer includes, for example, a porous substrate made of paper, cloth or nonwoven fabric, a plastic film or sheet, a foam, a metal, etc., depending on the purpose of packaging. Appropriate foils or thin foils such as laminates thereof can be used. For materials, for example, kraft paper and Japanese paper, cotton and soup, rayon and vinylon, polyester and polyamide, OPP and polyvinyl chloride, polyurethane and acrylic resins, polyolefins such as cellophane and polyethylene, natural rubber and synthetic rubber, aluminum and stainless steel, etc. Can be used.

The support base material may be subjected to a known surface treatment such as a coating treatment with a primer or the like, a corona discharge treatment or a plasma treatment for the purpose of improving the adhesion to the pressure-sensitive adhesive layer. Further, on the back surface of the supporting base material, if necessary, a release coat layer made of an appropriate release agent such as a silicone-based or long-chain alkyl-based release agent may be provided to obtain a wound-type packaging material that can be easily unwound. .

The packaging material according to the present invention can be used for various purposes according to the related art, if necessary, in the form of a narrow tape or the like. Especially for flaps and envelopes on cardboard boxes,
Alternatively, it can be preferably used for applications in which stress is generated in a packaging material and a phenomenon such as peeling may occur, such as binding or fixing various articles.

[0046]

【Example】

REFERENCE EXAMPLE 1 A 40 wt% toluene solution of natural rubber having a weight average molecular weight of 500,000 obtained by masticating with a roll was mixed with an aliphatic / aromatic copolymer having a softening point of 95 ° C. per 100 parts (parts by weight, the same applies hereinafter) of natural rubber. 90 parts of polymerized petroleum resin, 15 parts of terpene softener, 5 parts of terpene phenol resin having a softening point of 140 ° C., trimethylolpropane hexamethylene diisocyanate adduct 4
And 2 parts of a phenolic anti-aging agent, and the obtained pressure-sensitive adhesive was coated on kraft paper and dried at 100 ° C. for 3 minutes to obtain a 25 μm thick, 4.1 gf / mm ² elastic modulus. A pressure-sensitive adhesive layer was formed.

The elastic modulus was determined by preparing a sample having a cross-sectional area of 2 mm ² and a length of 30 mm, stretching the sample in a room at 23 ° C. with a chuck interval of 10 mm and a tensile speed of 50 mm / min. (The same applies hereinafter).

Reference Example 2 98 parts of 2-ethylhexyl acrylate, 1 part of methyl acrylate, and 1 part of acrylonitrile were polymerized at 60 ° C. for 5 hours in 200 parts of toluene in the presence of 0.2 part of azobisisobutyronitrile. The pressure-sensitive adhesive obtained as described above is coated on kraft paper and dried at 100 ° C. for 3 minutes to obtain a thickness of 25 mm.
A pressure-sensitive adhesive layer having a thickness of μm and an elastic modulus of 3.3 gf / mm ² was formed.

Reference Example 3 90 parts of an aliphatic / aromatic copolymerized petroleum resin having a softening point of 95 ° C. and a terpene-based softener 15 were added to a toluene solution containing 100 parts of a styrene / isoprene / styrene block copolymer rubber.
And a part of a phenolic antioxidant, and the obtained pressure-sensitive adhesive is coated on a separator and dried at 100 ° C. for 1 minute to obtain a layer having a thickness of 15 μm and a modulus of 8.0 gf / mm ² . A pressure bonding layer was formed.

Example 1 The pressure-sensitive adhesive layer obtained in Reference Example 3 was transferred onto the pressure-sensitive adhesive layer obtained in Reference Example 1 via a heating laminator at 100 ° C. to obtain a packaging material.

Example 2 The pressure-sensitive adhesive layer obtained in Reference Example 3 was transferred onto the pressure-sensitive adhesive layer obtained in Reference Example 2 via a heating laminator at 100 ° C. to obtain a packaging material.

Comparative Example 1 A pressure-sensitive adhesive layer having a thickness of 40 μm was formed according to Reference Example 1 to obtain a packaging material.

Comparative Example 2 A pressure-sensitive adhesive layer having a thickness of 40 μm was formed according to Reference Example 2 to obtain a packaging material.

Comparative Example 3 A pressure-sensitive adhesive layer having a thickness of 40 μm was formed according to Reference Example 3 to obtain a packaging material.

Comparative Example 4 A 25 μm thick pressure-sensitive adhesive layer formed according to Reference Example 3 was formed on a separator 1 according to Reference Example 1.
A 5 μm pressure-sensitive adhesive layer was transferred according to Example 1 to obtain a packaging material.

Comparative Example 5 A 25 μm-thick pressure-sensitive adhesive layer formed according to Reference Example 3 was formed on a separator 1 according to Reference Example 2.
A 5 μm pressure-sensitive adhesive layer was transferred according to Example 1 to obtain a packaging material.

Evaluation Test The following characteristics were examined for the packaging materials obtained in Examples and Comparative Examples. Adhesion In accordance with JIS Z 1522, the packaging material was adhered to a stainless steel plate under the pressure condition of reciprocating a 2 kg roller once, and the adhesion was examined.

Sealability Using a packaging material having a width of 50 mm, a flap
At 50 ° C. or 0 ° C., press and seal with a load of 500 g or 100 g and leave to check the time until the flap opens. Excellent if the flap does not open for 48 hours or more, excellent if not open for less than 48 hours, especially 24 The case opened in less than the time was evaluated as inappropriate.

The above results are shown in the following table.

From the table, it can be seen that the packaging material of the present invention exhibits excellent adhesive seal with low pressure bonding even at a low temperature and can be used under a wide range of conditions.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

[Description of Signs] 1: Overlapping layer of pressure-sensitive adhesive layer 11: High-modulus pressure-sensitive adhesive layer 12: Low-modulus pressure-sensitive adhesive layer 2: Support base material 21: Release coat layer

Claims (4)

[Claims] 1. An upper and a lower member having different elastic moduli on a supporting base material.
A packaging material characterized in that a pressure-sensitive adhesive layer having a high elastic modulus is located on the surface side of a superimposed layer composed of pressure-sensitive adhesive layers of the layers, which are closely adhered and fixed. 2. The packaging material according to claim 1, wherein the pressure-sensitive adhesive layer located on the surface side is made of an elastomer made of a styrene copolymer as a base polymer. 3. The pressure-sensitive adhesive layer according to claim 1, wherein the elastic modulus of the pressure-sensitive adhesive layer located on the surface side is 1.5 or less of that of the lower layer.
Packaging material that is more than double. 4. The pressure-sensitive adhesive layer according to claim 1, wherein the thickness of the pressure-sensitive adhesive layer located on the surface side is 0.05 to less than that of the lower layer.
Packaging material that is 10 times.