JP5889660B2 - Adhesive tape for sealing food containers - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive tape for sealing food containers, which is excellent in sealing properties, easy opening properties, and removability, and has high safety.

  In recent years, in the distribution process of foods such as prepared dishes, pickles, vegetables, fruits, fresh fish, meat, chicken eggs, and confectionery, these foods are placed in plastic containers and sealed with adhesive tape. ing.

When sealing a container using an adhesive tape, as shown in FIG. 1, the adhesive tape is usually folded and attached to a portion where the container main body and the lid overlap each other at the peripheral edge of the container. For this reason, there existed a problem that an adhesion area would become small easily and an adhesive tape peeled during use.
In particular, this problem is likely to occur when the main body and the lid are integrated as in an egg container, and the container to be bent is sealed or when the food is stored together with the container at a low temperature after sealing.

In order to solve this problem, if an adhesive tape with strong adhesive strength is used, the adhesive tape may be torn when the sealed container is opened, or adhesive residue may be generated in the container after the adhesive tape is peeled off. there were.
Therefore, the adhesive tape for sealing food containers is required to be excellent in easy-openability and removability in addition to being excellent in sealing properties.

  As an adhesive tape having such properties, Patent Document 1 discloses a pressure-sensitive adhesive tape for food container sealing having an adhesive layer containing a rubber-based adhesive on one side of a base material through an undercoat layer containing a diene rubber. Is described.

However, pressure-sensitive adhesive tapes using rubber-based pressure-sensitive adhesives usually use a harmful organic solvent such as toluene when forming the pressure-sensitive adhesive layer, so that these organic solvents may remain in the pressure-sensitive adhesive layer. .
Therefore, from the viewpoint of safety, there has been a demand for an adhesive tape for sealing food containers that can be easily manufactured without using a harmful organic solvent such as toluene.

JP 2006-104290 A

  The present invention has been made in view of such circumstances, and provides an adhesive tape for sealing food containers, which is excellent in sealing properties, easy opening properties, and removability, and has high safety. Objective.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have an acrylic system having a repeating unit derived from n-butyl acrylate, a repeating unit derived from a hydroxyl group-containing monomer, and a repeating unit derived from a carboxyl group-containing monomer. To find out that an adhesive tape having an adhesive layer formed using an acrylic adhesive containing a copolymer, a rosin ester compound, and a polyisocyanate compound has the desired performance, and to complete the present invention. It came.

Thus, according to the present invention, the following (1) to (6) food container sealing pressure-sensitive adhesive tapes are provided.
(1) A food container sealing pressure-sensitive adhesive tape having a base material layer and a pressure-sensitive adhesive layer, wherein the pressure-sensitive adhesive layer is at least a repeating unit derived from n-butyl acrylate, a repeating unit derived from a hydroxyl group-containing monomer, And an acrylic copolymer having a repeating unit derived from a carboxyl group-containing monomer, a rosin ester compound, and an acrylic pressure-sensitive adhesive containing a polyisocyanate compound. Adhesive tape.
(2) The pressure-sensitive adhesive tape for sealing food containers according to (1), wherein the base material layer is made of a polyester film having a thickness of 10 to 40 μm.
(3) The pressure-sensitive adhesive tape for sealing food containers according to (1) or (2), wherein the rosin ester compound has a softening point of 90 to 140 ° C. and a hydroxyl value of 20 to 80 mg KOH / g.
(4) The acrylic copolymer according to any one of (1) to (3), wherein the content of repeating units derived from n-butyl acrylate is 80 to 99% by mass in all repeating units. Adhesive tape for sealing food containers.
(5) The pressure-sensitive adhesive tape for sealing food containers according to (1) to (4), wherein the pressure-sensitive adhesive layer has a gel fraction of 50 to 70%.
(6) The adhesive tape for sealing a food container according to (1) to (5), wherein the food container is a plastic container.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesive tape for food container sealing excellent in sealing property, easy-opening property, and removability, and high safety | security is provided.

It is an expanded sectional view of the peripheral part (overlap part of a container main body and a lid | cover) of the container sealed with the adhesive tape. It is a perspective view of a food container (a food container in which a main body and a lid are integrated) before sealing. It is a perspective view of the food container sealed with the adhesive tape. It is a perspective view of the food container sealed with the adhesive tape.

  The food container sealing pressure-sensitive adhesive tape of the present invention (hereinafter sometimes abbreviated as “the pressure-sensitive adhesive tape of the present invention”) is a food container sealing pressure-sensitive adhesive tape having a base material layer and an adhesive layer, An acrylic copolymer having at least a repeating unit derived from n-butyl acrylate, a repeating unit derived from a hydroxyl group-containing monomer, and a repeating unit derived from a carboxyl group-containing monomer, a rosin ester compound, and And an acrylic pressure-sensitive adhesive containing a polyisocyanate compound.

(Base material layer)
The base material layer of the pressure-sensitive adhesive tape of the present invention is not particularly limited as long as it can support the pressure-sensitive adhesive layer and has sufficient flexibility and strength, and a known resin film can be used.

  Examples of the material of the resin film include polyolefin resins such as polyethylene resin and polypropylene resin; polyester resins such as polyethylene terephthalate resin and polyethylene naphthalate resin; polyvinyl chloride resin; polycarbonate resin; Among these, a polyester resin is preferable because a film excellent in balance between flexibility and strength can be easily obtained.

  The resin film may have a surface subjected to primer treatment or corona treatment. By performing these treatments, the adhesion with an adjacent layer can be improved.

  The thickness of the base material layer is usually 10 to 40 μm, preferably 15 to 35 μm. When the thickness is within this range, an adhesive tape excellent in workability such as sticking and peeling can be easily obtained.

(Adhesive layer)
The pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present invention comprises at least an acrylic copolymer having a repeating unit derived from n-butyl acrylate, a repeating unit derived from a hydroxyl group-containing monomer, and a repeating unit derived from a carboxyl group-containing monomer. , A rosin ester compound, and an acrylic pressure-sensitive adhesive containing a polyisocyanate compound.

  The acrylic copolymer used in the present invention is a copolymer having a repeating unit derived from n-butyl acrylate, a repeating unit derived from a hydroxyl group-containing monomer, and a repeating unit derived from a carboxyl group-containing monomer. The copolymer may be a random copolymer or a block copolymer.

  The acrylic copolymer has a repeating unit derived from n-butyl acrylate. Since the acrylic copolymer has a repeating unit derived from n-butyl acrylate, an adhesive layer having excellent adhesiveness is formed even at low temperatures, and thus an adhesive tape having excellent sealing properties can be easily obtained. .

  The content of the repeating unit derived from n-butyl acrylate in the acrylic copolymer is usually 80 to 99% by mass, preferably 80 to 94% by mass, and more preferably 80 to 90% in all repeating units. % By mass. When the content of the repeating unit derived from n-butyl acrylate is within this range, an adhesive layer having excellent adhesiveness is formed even at low temperatures, and thus an adhesive tape having excellent sealing properties can be easily obtained.

  The acrylic copolymer has a repeating unit derived from a hydroxyl group-containing monomer. Since the acrylic copolymer has a repeating unit derived from a hydroxyl group-containing monomer, it reacts with the polyisocyanate compound to form a crosslinked structure in the pressure-sensitive adhesive layer. Can get to.

The hydroxyl group-containing monomer is not particularly limited as long as it can react with the polyisocyanate compound to form a crosslinked structure.
Carbon number of a hydroxyl-containing monomer is 3-15 normally, Preferably it is 3-10.

Examples of the hydroxyl group-containing monomer include hydroxyl group-containing (meth) acrylic acid ester compounds such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; 2-hydroxyethyl And hydroxyl group-containing alkyl vinyl ether compounds such as vinyl ether, 4-hydroxybutyl vinyl ether, 6-hydroxyhexyl vinyl ether, and 8-hydroxyoctyl vinyl ether; and hydroxyl group-containing (meth) acrylamide compounds such as N-methylol (meth) acrylamide;
Among these, since it is easy to form a crosslinked structure, a hydroxyl group-containing (meth) acrylic acid ester compound is preferable, and 2-hydroxyethyl (meth) acrylate is more preferable.
In the present specification, “(meth) acryl” means “acryl or methacryl”.
A hydroxyl-containing monomer can be used individually by 1 type or in combination of 2 or more types.

  The content of the repeating unit derived from the hydroxyl group-containing monomer in the acrylic copolymer is usually 0.05 to 1.0% by mass, preferably 0.1 to 0.8% by mass in all repeating units. %. When the amount of repeating units derived from the hydroxyl group-containing monomer is within this range, a pressure-sensitive adhesive layer having sufficient initial adhesive strength and cohesiveness is formed. An excellent adhesive tape can be easily obtained.

  The acrylic copolymer has a repeating unit derived from a carboxyl group-containing monomer. Since the acrylic copolymer has a repeating unit derived from a carboxyl group-containing monomer, the copolymer has excellent affinity with other adhesive components and adherends having a hydrophilic group, and Thus, a crosslinked structure can be formed. As a result, since a uniform pressure-sensitive adhesive layer is formed with an excellent balance between initial adhesive strength and cohesiveness, an adhesive tape excellent in sealing properties, easy-openability, and removability can be easily obtained.

The carboxyl group-containing monomer is not particularly limited as long as it contains a carboxyl group and can form a copolymer having the above characteristics.
Carbon number of a carboxyl group-containing monomer is 3-15 normally, Preferably it is 3-10.
Examples of the carboxyl group-containing monomer include acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like.
Among these, acrylic acid and methacrylic acid are preferable, and acrylic acid is more preferable because a copolymer having the above characteristics is easily obtained.
A carboxyl group-containing monomer can be used individually by 1 type or in combination of 2 or more types.

  The content of the repeating unit derived from the carboxyl group-containing monomer in the acrylic copolymer is usually 0.5 to 10% by mass, preferably 1 to 5% by mass in all repeating units. When the amount of the repeating unit derived from the carboxyl group-containing monomer is within this range, a pressure-sensitive adhesive layer having sufficient initial adhesive strength and cohesiveness is formed, so that sealing, easy-openability, and removability are possible. Can be easily obtained.

  The acrylic copolymer is a repeating unit derived from an alkyl ester having 1 to 12 carbon atoms of (meth) acrylic acid (however, a repeating unit derived from n-butyl acrylate is excluded. Similarly, in the following description, “ The “n-butyl acrylate” may further include “(meth) acrylic acid alkyl ester having 1 to 12 carbon atoms”. By including this repeating unit in the acrylic copolymer, it becomes easy to control the adhesive property of the adhesive.

  Examples of the alkyl ester having 1 to 12 carbon atoms of (meth) acrylic acid include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl methacrylate, and isobutyl (meth). Examples include acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and isononyl (meth) acrylate.

  Among these, alkyl esters of 4 to 8 carbon atoms (excluding n-butyl acrylate) of (meth) acrylic acid are preferable, and n-butyl methacrylate, isobutyl (meth) acrylate, and t-butyl (meth) acrylate. , Isooctyl (meth) acrylate, and n-octyl (meth) acrylate are more preferable, and isobutyl methacrylate is more preferable.

  The C1-C12 alkyl ester of (meth) acrylic acid can be used individually by 1 type or in combination of 2 or more types.

  When the acrylic copolymer has a repeating unit derived from an alkyl ester having 1 to 12 carbon atoms of (meth) acrylic acid, the alkyl having 1 to 12 carbon atoms of (meth) acrylic acid in the acrylic copolymer The content of the ester-derived repeating unit is preferably 5 to 19% by mass, and more preferably 5 to 15% by mass in all repeating units. Since the repeating unit amount derived from an alkyl ester having 1 to 12 carbon atoms of (meth) acrylic acid is within this range, the initial adhesiveness of the pressure-sensitive adhesive layer can be enhanced without impairing the cohesiveness. It is possible to easily obtain a pressure-sensitive adhesive tape having excellent properties, easy opening, and removability.

The acrylic polymer may have a repeating unit derived from another monomer.
Other monomers include vinyl esters such as vinyl acetate and vinyl propionate; nitrile compounds such as acrylonitrile and methacrylonitrile; aromatic vinyl compounds such as styrene and vinylpyridine.

The acrylic copolymer can be produced by a known polymerization method using a monomer mixture such as n-butyl acrylate, a hydroxyl group-containing monomer, and a carboxyl group-containing monomer.
The polymerization method is not particularly limited, and examples thereof include bulk polymerization, solution polymerization, dispersion polymerization, and emulsion polymerization. There are no particular limitations on the method for initiating these polymerization reactions, and a method using a thermal polymerization initiator such as benzoyl peroxide, lauroyl peroxide or azoisobutyroylnitrile; photopolymerization initiation of benzoin, benzoin methyl ether, benzophenone, or the like. And a method of using an agent, ultraviolet irradiation, electron beam irradiation, and the like.

The weight average molecular weight of the acrylic copolymer is preferably 200,000 to 1,500,000, and more preferably 600,000 to 1,000,000. When the weight average molecular weight is 200,000 or more, a pressure-sensitive adhesive layer having sufficient cohesiveness is formed. Moreover, the adhesive which is excellent in workability | operativity, such as coating, can be obtained because a weight average molecular weight is 1,500,000 or less.
The weight average molecular weight is a value in terms of polystyrene measured by gel permeation chromatography (GPC) method.

  The rosin ester compound used in the present invention is not particularly limited as long as it is an ester compound of a rosin compound such as natural rosins and processed rosins and an alcohol and can function as a tackifier resin.

Examples of the natural rosins include gum rosin, tall oil rosin, and wood rosin, and examples of the processed rosins include those obtained by subjecting natural rosins to treatments such as polymerization, modification, and disproportionation. .
Examples of the alcohol include methanol, ethanol, isopropyl alcohol, isoamyl alcohol, n-hexyl alcohol, n-octyl alcohol, 2-ethylhexyl alcohol, decyl alcohol, lauryl alcohol and other monohydric alcohols; ethylene glycol, diethylene glycol, propylene glycol, neo And dihydric alcohols such as pentyl glycol and cyclohexanedimethanol; trihydric alcohols such as glycerin, trimethylolethane and trimethylolpropane; and tetrahydric alcohols such as pentaerythritol and diglycerin;

  The esterification reaction can be performed by a known method such as a method of heating a rosin compound and an alcohol in the presence of a catalyst. Examples of the catalyst include acid catalysts such as acetic acid and p-toluenesulfonic acid; alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; alkaline earth metal water such as calcium hydroxide and magnesium hydroxide. Oxides; metal oxides such as calcium oxide, magnesium oxide, zinc oxide, lead oxide, and tin oxide;

The rosin ester compound has a softening point of usually 90 to 140 ° C, preferably 95 to 130 ° C. By using a material having a softening point of 90 ° C. or higher, an adhesive tape having excellent sealing properties can be easily obtained. In addition, those having a softening point of 140 ° C. or less are excellent in compatibility with the acrylic copolymer, and by using this, an adhesive tape having excellent low-temperature adhesiveness can be easily obtained.
The softening point is a value measured by the ring and ball method according to JIS K5601-2-2.

The rosin ester compound preferably has a hydroxyl group. Since the rosin ester compound has a hydroxyl group, it reacts with the isocyanate group of the polyisocyanate compound described later to form a cross-linked structure, or a carboxyl group in the acrylic copolymer forms a hydrogen bond. An adhesive layer is formed.
The rosin ester compound has a hydroxyl value of usually 20 to 80 mgKOH / g, preferably 25 to 60 mgKOH / g. By using the one having a hydroxyl value of 20 mgKOH / g or more, an adhesive tape excellent in sealing property can be easily obtained. Moreover, the adhesive tape which is excellent in low temperature adhesiveness can be obtained easily by using a hydroxyl value of 80 mgKOH / g or less.
The hydroxyl value is a value measured by a neutralization titration method described in JIS K0070: 1992.

  The rosin ester compounds can be used singly or in combination of two or more.

  Content of the rosin ester compound in an acrylic adhesive is 10 mass parts or more normally with respect to 100 mass parts of resin solid content of an acrylic adhesive, Preferably, it is 10-30 mass parts. When the rosin ester compound is 10 parts by mass or more, a pressure-sensitive adhesive tape excellent in sealing properties can be easily obtained. Moreover, the adhesive tape which is excellent in adhesiveness can be obtained more easily because a rosin ester compound is 30 mass parts or less.

  The polyisocyanate compound used in the present invention is not particularly limited as long as it has two or more isocyanate groups capable of reacting with a hydroxyl group or a carboxyl group to form a crosslinked structure in the pressure-sensitive adhesive layer.

Examples of polyisocyanate compounds include aromatic diisocyanate compounds such as tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), and diphenylmethane diisocyanate; aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate (HMDI) and isophorone diisocyanate (IPDI). Compound; Tolylene diisocyanate trimer adduct of trimethylolpropane; Triisocyanate compound such as triphenylmethane triisocyanate and methylenebis (4-phenylmethane) triisocyanate;
A polyisocyanate compound can be used individually by 1 type or in combination of 2 or more types.

By adjusting the content of the polyisocyanate compound, the amount of crosslinking formed in the pressure-sensitive adhesive layer can be adjusted.
The content of the polyisocyanate compound in the acrylic pressure-sensitive adhesive is usually 0.1 to 10 parts by weight, preferably 0.2 to 5 parts by weight with respect to 100 parts by weight of the resin solid content of the acrylic pressure-sensitive adhesive. is there. Since the pressure-sensitive adhesive layer having sufficient initial adhesive strength and cohesiveness is formed when the content of the polyisocyanate compound is within the above range, a pressure-sensitive adhesive tape excellent in sealing property, easy-opening property, and removability is obtained. Can be easily obtained.

The acrylic pressure-sensitive adhesive may contain other tackifying resins and crosslinking agents as long as the effects of the present invention are not impaired.
Other tackifying resins include petroleum resins such as C5 (aliphatic) resins and C9 (aromatic) resins; α-pinene, β-pinene polymer, diterpene polymer, α-pinene-phenol Terpene compounds such as polymers or derivatives thereof; xylene resins or modified products thereof; and the like.

  Examples of other crosslinking agents include epoxy-based crosslinking agents such as ethylene glycol glycidyl ether and 1,6-hexanediol glycidyl ether; tris-2,4,6- (1-aziridinyl) -1,3,5-triazine, tris [1- (2-methyl) aziridinyl] phosphinoxide and other aziridine-based crosslinking agents; aluminum chelates, titanium chelates and other chelate-based crosslinking agents, and the like.

  The acrylic pressure-sensitive adhesive can contain known additives. Known additives include light stabilizers, antioxidants, softeners, anti-aging agents, fillers, colorants, and the like.

The acrylic pressure-sensitive adhesive can be prepared by dissolving or dispersing the acrylic copolymer, rosin ester compound, isocyanate compound, and, if necessary, an additive in an appropriate solvent.
Examples of the solvent used for the preparation include ester solvents such as ethyl acetate; ketone solvents such as acetone; ether solvents such as diethyl ether; Among these, an ester solvent is preferable and ethyl acetate is more preferable because a tape having sufficient safety for sealing a food container can be obtained even when the solvent remains in the pressure-sensitive adhesive layer. In addition, it is preferable not to use a solvent having a relatively high toxicity to the human body, such as toluene.

As will be described later, the pressure-sensitive adhesive layer can be obtained by applying an acrylic pressure-sensitive adhesive and drying it.
Although the thickness in particular of an adhesive layer is not restrict | limited, Usually, 5-100 micrometers, Preferably, it is 10-60 micrometers.

The pressure-sensitive adhesive layer has a moderately crosslinked structure. The degree of formation of the crosslinked structure can be determined by measuring the gel fraction. The gel fraction can be determined by the method described in the examples.
The gel fraction of the pressure-sensitive adhesive tape of the present invention is preferably 50 to 70%. The pressure-sensitive adhesive tape having a gel fraction within this range has excellent sealing properties, easy opening properties, and removability.

(Food container sealing tape)
The adhesive tape of this invention has the said base material layer and an adhesive layer. In addition to these layers, the pressure-sensitive adhesive tape of the present invention may have other layers.
In the pressure-sensitive adhesive tape of the present invention, the base material layer and the pressure-sensitive adhesive layer may be adjacent to each other, and a printing layer or the like may be present between these layers.

The pressure-sensitive adhesive tape of the present invention may have a release sheet that protects the pressure-sensitive adhesive layer.
As the release sheet, a paper base such as high-quality paper, clay-coated paper, glassine paper; laminated paper obtained by laminating a polyolefin resin film such as polyethylene resin or polypropylene resin on these paper bases; cellulose or starch on the paper base; A known substrate such as a release substrate subjected to sealing treatment such as polyvinyl alcohol or acrylic-styrene resin; a film substrate such as polyethylene, polypropylene, or polyester; can be used.
The thickness of the release sheet is not particularly limited and may be appropriately selected.

The pressure-sensitive adhesive tape of the present invention may have a back surface treatment layer on the back surface (the surface opposite to the pressure-sensitive adhesive layer) of the base material layer. When the food container is sealed using the pressure-sensitive adhesive tape wound up in a roll shape, the pressure-sensitive adhesive tape having the back treatment layer can be easily pulled out from the roll even if it does not have a release sheet.
When the adhesive tape of this invention has a back surface treatment layer, you may have a printing layer between the base material layer and the back surface treatment layer.

  The width | variety in particular of the adhesive tape of this invention is not restrict | limited, Usually, 5-100 mm, Preferably, it is 10-50 mm.

The method for producing the pressure-sensitive adhesive tape of the present invention is not particularly limited. For example, on one side of the resin film for the base material layer, the acrylic pressure-sensitive adhesive is applied, the obtained coating film is dried, and if necessary, a release sheet is bonded to produce a pressure-sensitive adhesive sheet. The pressure-sensitive adhesive tape of the present invention can be obtained by cutting to a predetermined width.
Moreover, a pressure sensitive adhesive sheet is prepared by preparing a separate release sheet, applying the acrylic pressure-sensitive adhesive to the surface of the release agent layer of the release sheet, drying the obtained coating film, and laminating this with a resin film for the base material layer. May be manufactured and cut.

  The method for applying the acrylic pressure-sensitive adhesive is not particularly limited. For example, a method using a known coating apparatus such as an air knife coater, blade coater, bar coater, gravure coater, roll coater, roll knife coater, curtain coater, die coater, knife coater, screen coater, Meyer bar coater, kiss coater, etc. Can be mentioned.

The pressure-sensitive adhesive tape of the present invention has a pressure-sensitive adhesive layer formed using an acrylic pressure-sensitive adhesive containing at least the acrylic copolymer, rosin ester compound, and polyisocyanate compound.
For this reason, the pressure-sensitive adhesive tape of the present invention has a sufficient pressure-sensitive adhesive force even if the sticking area is small, and the pressure-sensitive adhesive force hardly decreases even at low temperatures. Moreover, when peeling an adhesive tape from a to-be-adhered body, it can peel easily and the problem of an adhesive residue does not arise.
Furthermore, since the adhesive tape of the present invention does not require the use of a solvent such as toluene when forming the adhesive layer, it is highly safe.
As described above, the pressure-sensitive adhesive tape of the present invention is excellent in sealing property, easy-opening property, and removability, and is highly safe, and thus is suitably used as a pressure-sensitive adhesive tape for food container sealing.

The adhesive tape of the present invention is not particularly limited to the material of the food container, and is used when sealing a known food container such as a paper container or a plastic container. Especially, since the characteristic of the adhesive tape of this invention is easy to be exhibited, it is preferably used when sealing plastic containers, such as a polyethylene terephthalate and a polystyrene.
In particular, since the excellent sealing property of the pressure-sensitive adhesive tape of the present invention is easily exhibited, the pressure-sensitive adhesive tape of the present invention is a container in which the main body and the lid are integrated like an egg pack (the original opened even after sealing). It is preferably used when sealing a container that always returns to a state) or when sealing a container that is stored at a low temperature (for example, −5 to 15 ° C.) after sealing.

When a food container is sealed using the adhesive tape of the present invention, the adhesive tape is usually folded and attached to the peripheral edge of the container (the part where the container body and the lid overlap).
For example, when a food container composed of a lid a and a container body b as shown in FIG. 2 is sealed, an adhesive tape may be applied so as to cover all of one side of the container peripheral portion as shown in FIG. However, as shown in FIG. 4, an adhesive tape may be attached to a part of one side of the peripheral edge of the container (adhesive tape 5).

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

Details of the compounds used in Examples and Comparative Examples are shown below.
(1) Monomer n-BA: n-butyl acrylate i-BMA: isobutyl methacrylate AA: acrylic acid 2-HEA: 2-hydroxyethyl acrylate 2-EHA: 2-ethylhexyl acrylate

(2) Rosin ester compound Rosin ester compound 1: Pentaerythritol esterified product of polymerized rosin (Arakawa Chemical Industries, Pencel D-125, softening point 125 ° C., hydroxyl value 31 mgKOH / g)
Rosin ester compound 2: Pentaerythritol esterified product of hydrogenated rosin (Arakawa Chemical Industries, Pine Crystal KE-359, softening point 100 ° C., hydroxyl value 42.5 mgKOH / g)
Rosin ester compound 3: Special rosin ester (Arakawa Chemical Industries, super ester A-125, softening point 125 ° C., hydroxyl value 15 mg KOH / g)
Rosin ester compound 4: Hydrogenated rosin ester (Arakawa Chemical Industries, Pine Crystal KE-311, softening point 95 ° C., hydroxyl value <10 mg KOH / g)

(3) Polyisocyanate compound Polyisocyanate compound 1 :: Trimethylolpropane-modified tolylene diisocyanate (manufactured by Nippon Polyurethane Co., Ltd., Coronate L, molecular weight 657, solid content concentration 75% by mass)
Polyisocyanate compound 2: Trimethylolpropane-modified xylylene diisocyanate (Mitsui Chemical Polyurethanes, Takenate D110N, molecular weight 698, solid concentration 75% by mass)

[Example 1]
In a reaction apparatus equipped with a thermometer, a stirrer, a reflux cooling tank, and a nitrogen gas introduction tank, n-BA 87.5 parts by mass, i-BMA 10 parts by mass, AA 2.0 parts by mass, 2-HEA 0.5 A mass part, 80 parts by mass of ethyl acetate, and 0.03 part by mass of benzoyl peroxide were charged, and a copolymerization reaction was performed at 70 ° C. in a nitrogen gas atmosphere. A weight average molecular weight (Mw) 830,000, a molecular weight distribution (Mw / A solution containing acrylic copolymer 1 of (Mn) 3.8 was obtained.

  In a solution containing the obtained acrylic copolymer 1, 5 parts by mass of rosin ester compound 1, 7.5 parts by mass of rosin ester compound 2, 0.8 parts by mass with respect to 100 parts by mass of the resin solid content. The polyisocyanate compound 1 was uniformly added while diluting with ethyl acetate to obtain 40% by mass of an acrylic pressure-sensitive adhesive 1.

  A Meyer bar is used on one side of a polyester film (Toray Industries, Lumirror S-15, 25 μm thick) with a long-chain alkyl resin release agent (manufactured by Nippon Shokubai Co., Ltd., RP-20) so that the dry thickness is 2 μm. The resulting coating film was dried to produce a base layer resin film.

  Next, the acrylic pressure-sensitive adhesive 1 is applied to the surface opposite to the surface on which the base layer resin film has been peeled off using a Meyer bar so that the dry thickness is 15 μm. The pressure-sensitive adhesive sheet 1 was obtained by drying the coated film. The pressure-sensitive adhesive sheet 1 was cut to a width of 15 mm to obtain a pressure-sensitive adhesive tape 1 for testing.

[Examples 2 to 11, Comparative Examples 1 to 3]
Using the acrylic copolymer, rosin ester compound, and polyisocyanate compound shown in Table 1, adhesive tapes 2 to 14 were produced in the same manner as in Example 1.

Using the pressure-sensitive adhesive tapes 1 to 14 (or pressure-sensitive adhesive sheets 1 to 14) obtained in Examples and Comparative Examples, the following measurements and tests were performed.
(1) Gel fraction About 500 mg of the pressure-sensitive adhesive layer was peeled off from each of the pressure-sensitive adhesive sheets 1 to 14, and the peeled pressure-sensitive adhesive was wrapped in a 300-mesh Teflon (registered trademark) net and weighed (weighed at this time) Let the value be M1). Next, the net was immersed in ethyl acetate for 72 hours, dried at 120 ° C. for 3 hours, and weighed (the measured value at this time is M2).
The gel fraction was calculated from the following formula using M1 and M2.

(2) Adhesive strength test Each of the adhesive tapes 1 to 14 was attached to an amorphous polyethylene terephthalate sheet by reciprocating a 2 kg roller once at 23 ° C. Immediately thereafter, the adhesive tapes 1 to 14 were peeled off at a peeling angle of 180 ° and a peeling speed of 300 mm / min, and the adhesive strength (N / 15 mm) at this time was measured.

(3) Sealing property evaluation Adhesive tapes 1 to 14 each having a length of 250 mm were attached to all of the sides of the amorphous polyethylene terephthalate egg pack to seal the egg pack, and this was left at 72C for 72 hours. Then, the presence or absence of peeling or lifting of the adhesive tapes 1 to 14 was visually examined, and sealing properties were evaluated according to the following criteria.
○: There is no floating.
Δ: There is some floating.
X: There is a float on the entire surface.

(4) Evaluation of removability (presence or absence of adhesive residue on plastic food containers)
Adhesive tapes 1 to 14 having a length of 250 mm were respectively attached to an amorphous polyethylene terephthalate egg pack and allowed to stand at 5 ° C., 23 ° C., and 40 ° C. for 72 hours. Thereafter, the adhesive tape was peeled off from the egg pack, and the presence or absence of adhesive residue on the egg pack was visually examined, and the removability was evaluated according to the following criteria.
○: There is no adhesive residue.
(Triangle | delta): There exists a glue residue in part.
X: There is adhesive residue on the entire surface.

Table 1 shows the following.
The adhesive tapes 1-11 of Examples 1-11 have moderate adhesive force, and are excellent in sealing performance and removability. In particular, the pressure-sensitive adhesive tapes 1 to 6 of Examples 1 to 6 using preferred acrylic copolymers and rosin ester compounds have further excellent performance.
On the other hand, in the pressure-sensitive adhesive tape 12 of Comparative Example 1 using an acrylic copolymer having no repeating unit derived from a hydroxyl group-containing monomer, the gel fraction of the pressure-sensitive adhesive layer is extremely small, and the adhesive residue is recognized on the entire surface. It was.
Further, the pressure-sensitive adhesive tape 13 of Comparative Example 2 using an acrylic copolymer having no repeating unit derived from a carboxyl group-containing monomer also has a small gel fraction of the pressure-sensitive adhesive layer, and adhesive residue is recognized on the entire surface. It was.
Moreover, the adhesive tape 14 of the comparative example 3 using the acrylic copolymer which does not have a repeating unit derived from n-butyl acrylate is too hard to peel off because the adhesive force is too large.

DESCRIPTION OF SYMBOLS 1 ...... End 2 of a lid ... End 3 of a container main body ...... Adhesive tape 4 ... Adhesive tape 5 stuck on all sides of a container ... One side of a container Adhesive tape affixed to a part of the lid b ... the container body

Claims (4)

A food container sealing pressure-sensitive adhesive tape having a base material layer and a pressure-sensitive adhesive layer,
The pressure-sensitive adhesive layer has at least a repeating unit derived from n-butyl acrylate, a repeating unit derived from a hydroxyl group-containing monomer, and a repeating unit derived from a carboxyl group-containing monomer, and a softening point of 95. -130 ° C, a rosin ester compound having a hydroxyl value of 20-80 mgKOH / g, and an acrylic pressure-sensitive adhesive containing a polyisocyanate compound,
The acrylic copolymer has a content of repeating units derived from n-butyl acrylate of 80 to 90% by mass in all repeating units,
The adhesive tape for food container sealing , wherein the content of the rosin ester compound is 10 to 30 parts by mass with respect to 100 parts by mass of the resin solid content of the acrylic adhesive. The adhesive tape for food container sealing of Claim 1 whose said base material layer consists of a polyester film with a thickness of 10-40 micrometers.   The pressure-sensitive adhesive tape for food container sealing according to claim 1 or 2, wherein the pressure-sensitive adhesive layer has a gel fraction of 50 to 70%.   The adhesive tape for food container sealing in any one of Claims 1-3 whose said food container is a plastic container.

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