JP2001092358A - Thermosensitive label, hot melt type adhesive for thermosensitive label, and method of peeling thermosensitive label - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosensitive label which is used for containers, such as glass bottles and plastic bottles, and is suitable for the recyclability of the bottles since the labels are peelable from the containers when the containers are put into an aqueous alkaline solution after use. SOLUTION: This thermosensitive label is formed by providing a label base material with a hot melt type adhesive containing a polymer having an acid value of >=90 mgKOH/g at 7 to 15 g/m2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive label for glass bottles and the like used for juices, beer, wine, nutritional drinks, seasonings, cosmetics and the like. The present invention relates to a heat-sensitive label suitable for recyclability of a bottle, a hot-melt adhesive used for the label, and a method of peeling a heat-sensitive label, since the label is easily peeled from the bottle when immersed in an alkaline aqueous solution after use.

[0002]

2. Description of the Related Art Glass bottles are used for juices, energy drinks,
It is used for dressing, cocktails, etc., and is roughly classified into returnable bottles (collection bottles), such as one-way bottles, beer bottles, and sake bottles, which are not collected and reused after use.

[0003] As a conventional adhesive for a label for a glass bottle or the like, a cold glue such as casein or an adhesive is used. Examples of using cold glue such as casein include a beer bottle label and a sake liquor bottle, and this labeling method is to apply cold glue to a bottle while spraying it. On the other hand, adhesive labels using adhesives are mainly used for shampoo containers, etc. After applying the adhesive to release paper (separator), remove the release paper (separator) when attaching to the adherend. There is a method of sticking on a glass bottle or plastic bottle (tack label).

[0004]

The cold glue using casein, which is used in returnable bottles (recovery bottles) such as beer bottles, sake bottles, etc., does not come off even if it is put in water. Although some may be peeled off when put inside, when cold glue glue is used, the glue tends to protrude, wrinkle, float, etc., and problems tend to occur in labeling accuracy and appearance after labeling.
In addition, it is necessary to adjust the drying of the glue, which requires skill of an operator, and it is difficult to automate the machine (reduce labor costs by unmanned operation). In addition, maintenance such as cleaning the machine after use was troublesome.

[0005] Tack labels are expensive because of the release paper (separator) attached, and thus are not often used.

[0006] A label coated with a delayed tack adhesive is known. However, the label coated with the delayed tack adhesive has a blocking property for developing tack when the temperature rises to 40 ° C. or higher during storage and transportation,
There are problems such as slipperiness, cutting ability, and appropriate post-printing suitable for high-speed labeling machines.

Further, an adhesive sheet using a heat-sensitive and water-dispersible thermoplastic resin having a hydrophilic group as a sheet-like base material is also known. Although this pressure-sensitive adhesive sheet is said to be peelable by washing with water, it has a problem in that it does not peel off when it comes into contact with water, such as during cooling, when attached to the adherend.

[0008]

The present inventors have conducted intensive studies to overcome the above-mentioned drawbacks, and as a result, have obtained an acid value of 90 mgK.
By providing a hot melt type adhesive containing a polymer of OH / g or more on a label base material in an amount of 7 to 15 g / m ² ,
The present inventors have found that the label can be peeled off with an aqueous alkali solution, and that a heat-sensitive label particularly suitable for a return bottle (recovery bottle) can be provided.

[0009]

Means for Solving the Problems The first invention has an acid value of 90.
This is a heat-sensitive label in which a hot-melt adhesive containing a polymer of not less than mgKOH / g is provided on a label substrate in an amount of 7 to 15 g / m ² .

A second invention is a heat-sensitive label comprising a hot-melt adhesive containing a polymer, tackifier and wax and having an acid value of 100 mg KOH / g or more.

A third aspect of the present invention is a heat-sensitive label containing at least one kind of tackifier having an acid value of 150 mgKOH / g or more.

A fourth invention is a heat-sensitive label, characterized in that the polymer contains an ethylene- (meth) acrylic acid copolymer.

A fifth invention is a hot melt adhesive for labels containing a polymer having an acid value of 90 mgKOH / g or more and being dispersed or dissolved in an aqueous alkaline solution.

A sixth aspect of the present invention is a method for peeling a heat-sensitive label, wherein the label to which the heat-sensitive label is adhered is peeled off with an alkaline aqueous solution.

The present invention is used for a returnable bottle (recovery bottle) label such as a beer bottle label, a sake bottle label, etc. When cooling or the like, the label does not peel off even if put in water, but is recovered after use. When washing the bottle, the method of peeling the thermosensitive label and the hot-melt adhesive used for the label and the method of peeling the heat-sensitive label, which is easily peeled by dipping in an alkaline aqueous solution or spraying, is used. is there.

The temperature of the aqueous alkaline solution is peeled off even at room temperature, but it takes a long time to peel off, so that it is preferable that the temperature be high. Specifically, 50 ° C to 100 ° C, preferably 60 ° C
C. to 100C. If the concentration of the alkaline aqueous solution is too low, the peeling time is prolonged or the peeling is not performed. In addition, even if it is too high, the hot melt adhesive does not disperse or dissolve in the alkaline aqueous solution. Preferred concentration is 0.05% by weight (wt)
Not less than 10 wt%, more preferably 0.1 w
It is at least t% and at most 5 wt%. Alkaline aqueous solutions mainly include hydroxides of alkali metals and alkaline earth metals,
There is an aqueous ammonium solution and the like.

The base material of the heat-sensitive label for a glass bottle or the like used in the present invention is a plastic film such as paper, synthetic paper, vapor-deposited paper, PET (polyethylene terephthalate), PP (polypropylene), vinyl chloride, PE (polyethylene), and cellophane. Or sheets and their composite papers, etc., but in consideration of water resistance, paper, synthetic paper,
Evaporated paper is preferred. When using a base material (paper, synthetic paper, or vapor-deposited paper) on which the active ingredient of the hot-melt adhesive is easily permeated, such as paper, synthetic paper, or vapor-deposited paper, the coated surface of the hot-melt adhesive is used. It is preferable to use a barrier layer. Examples of the barrier layer include a polymer such as polyvinyl alcohol and starch, and a polymer such as styrene-acrylate copolymer.

The hot-melt adhesive of the present invention is obtained by melting a composition comprising 100% solids, mainly a thermoplastic resin, by heating to be in a liquid state, and contains substantially no solvent or the like.

The role of the polymer used in the hot-melt adhesive of the present invention is to improve the flexibility of the hot-melt adhesive and to impart cohesive strength, and thermoplastic polymers are generally used. A hot-melt adhesive containing no polymer has high rigidity and is hard and brittle. The polymer according to the present invention has an acid value of 90.
The polymer is at least mgKOH / g, preferably at least 95 mgKOH / g, more preferably at least 98 mgKOH / g. Typical polymers having an acid value of 90 mgKOH / g or more include ethylene- (meth) acrylic acid copolymer,
(Meth) acrylic acid- (meth) acrylic acid ester copolymer, α-olefin-maleic anhydride copolymer, styrene- (meth) acrylic acid copolymer, etc. Considering the flexibility of the melt, an ethylene- (meth) acrylic acid copolymer is preferred.

When a polymer having an acid value of less than 90 mgKOH / g is used, the releasability in an alkaline aqueous solution is poor. That is, in the case of a polymer having an acid value of less than 90 mgKOH / g, there is a possibility that a so-called adhesive residue may be left on the label base material or the adherend by the hot-melt type adhesive when peeled off with an aqueous alkali solution.

The role of the wax used in the hot-melt adhesive of the present invention is to lower the melt viscosity of the hot-melt adhesive to improve workability, prevent blocking, adjust the open time, and improve heat resistance. is there. If wax is not used for the hot-melt type adhesive, the viscosity is high and the workability is deteriorated, and stringing during application may occur. Representative waxes include carnauba wax, candelilla wax, montan wax, fatty acids, fatty acid glycerides, polyethylene wax, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, polypropylene wax, oxidized waxes thereof, and ethylene-acrylic acid copolymer. Polymer wax and ethylene-methacrylic acid copolymer wax are exemplified. In consideration of the alkali releasability, montan wax and ethylene-acrylic acid copolymer wax are preferred.

The role of the tackifier used in the hot-melt adhesive of the present invention is to improve the adhesive strength and to improve the wettability and workability of the hot-melt adhesive. If a tackifier is not used for the hot-melt adhesive, the adhesive strength may decrease. Typical tackifiers include rosin, rosin derivatives (hydrogenated rosin, disproportionated rosin, polymerized rosin, modified rosin acrylic acid, modified rosin fumaric acid, modified rosin maleic acid, and their rosin esters (alcohol, glycerin, pentaerythritol) Terpene resin (α-pinene, β-pinene), terpene phenol resin, aromatic modified terpene resin, hydrogenated terpene resin, aliphatic petroleum resin, aromatic petroleum resin, copolymer Petroleum resin, alicyclic petroleum resin, cumarone-indene resin, styrene resin, phenol resin and the like. Considering the alkali dispersibility, the acid value of the tackifier is 15
The tackifier is preferably rosin or a rosin derivative, for example, raw rosin, (meth) acrylic acid-modified rosin, (anhydrous) maleic acid-modified rosin, fumaric acid-modified rosin, hydrogenated rosin, or the like. Polymerized rosin and the like. Considering the blocking property of the thermal label, the softening point of the tackifier is 75 ° C.
Or more, preferably 85 ° C or more, more preferably 100 ° C or more.
° C or higher.

The viscosity of the hot melt type adhesive at 140 ° C. is preferably 10 cps to 1,000,000 cps, and more preferably 50 cps to 500,000 cps. If the viscosity of the hot melt type adhesive is less than 10 cps or more than 1,000,000 cps, it is difficult to apply.

In the present invention, in order to prevent thermal degradation and thermal decomposition, high molecular weight hindered polyhydric phenols, triazine derivatives, high molecular weight hindered phenols, dialkyl
Phenol sulfide, 2,2'-methylene-bis-
(4-methyl-6-tert-butylphenol, 4,4 ′
Methylene-bis- (2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol,
2,2'-methylene-bis- (4-methyl-6-tert-
Butylphenol), 2,5-di-tert-butylhydroquinone, 2,2,4-trimethyl-1,2-dihydroquinoline, a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline, 6- Ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, nickel dibutyl dithiocarbamate, 1-oxy-3-methyl-4-isopropylbenzene, 4,4'-butylidenebis- (3-
An antioxidant such as methyl-6-tert-butylphenol or 2-mercaptobenzimidazole may be added.

As a method for applying the hot melt type adhesive to the label substrate, there are a roll coater method using a direct roll, a gravure roll, etc., an extrusion coater method, a slit orifice coater method, and the like. There is no problem with the construction method, and the solvent may be removed by dissolving in a solvent and coating, and then heating and drying.

The coating amount of the hot melt type adhesive is 7-1.
5 g / m ² . The coating amount on the label substrate is 7 g / m ²
If it is less than the above range, it will not adhere to a glass bottle, a plastic bottle, or the like, or even if it adheres, it will not have water resistance or dew condensation resistance. If it exceeds 15 g / m ² , the hot-melt type adhesive adheres to the label cutter in the thermal labeler, so that a phenomenon occurs in which the thermal label is jammed on the blade of the cutter (jamming). In particular, since the hot melt adhesive having the acid value of the present invention easily adheres to the label cutter, it is practically important to control the coating amount. Further, it is not preferable that the coating amount is large because it is not economical or blocks easily.

The glass bottle as one of the adherends may be a transparent bottle, a brown bottle, or a color bottle of blue, red, or green. The surface of the glass bottle can be cold-coated, hot-coated, polyethylene (P
E) There is no problem even with resin coating such as coating. The heat-sensitive label of the present invention can be applied to glass products other than glass bottles, metal products such as metal containers, and other materials.

It is desirable that the hot melt adhesive used for the heat-sensitive label has an acid value of 100 mgKOH / g or more, preferably 150 mgKOH / g or more. When the acid value is less than 100 mgKOH / g, the label and the glass do not adhere, the adhesive does not have water resistance, or the alkaline aqueous solution does not disperse or dissolve. If the softening point of the hot-melt adhesive used for the heat-sensitive label is less than 50 ° C., the blocking property is poor, and the heat-sensitive label cannot be used due to blocking when the heat-sensitive label is stacked or stored in a roll. If the temperature exceeds 120 ° C, it will not adhere to the glass bottle when using a high-speed thermal labeler (a machine that heats the adhesive layer of the thermal label to develop adhesive properties and sticks it to various objects). , Peels off quickly or easily by hand.

In the above invention, one or more kinds of polymers, tackifiers and waxes may be used. Silicone or the like may be added to prevent blocking in addition to the polymer, tackifier and wax. However, when silicone is used, adhesiveness and water resistance may be deteriorated.

The hot melt adhesive according to the present invention usually has a composition ratio of 10 to 70 parts by weight of a polymer, 10 to 70 parts by weight of a tackifier, and 1 to 70 parts by weight of a wax. The hot melt adhesive of the present invention contains at least a polymer having an acid value of 90 mgKOH / g or more as a polymer. Although a polymer having an acid value of less than 90 mg KOH / g may be used in combination, the polymer as a whole has an acid value of 90 mg KO
H / g or more is sufficient.

The hot melt type adhesive according to the present invention comprises:
Dispersing or dissolving in an aqueous alkali solution means that when the aqueous alkali solution is applied to an adherend to which a label coated with a hot-melt adhesive has been applied, the label peels off, and in particular, the label substrate It means that it is peeled off without leaving adhesive or adherent on the adherend. In addition, since the label can be easily recycled, it is desirable that the hot melt adhesive is dispersed or dissolved in an aqueous alkaline solution and peeled off.

[0032]

The present invention will be specifically described below with reference to examples. However, the scope of the present invention is not limited at all by the following examples. <Examples 1 to 7> Adhesive preparation method According to the formulation shown in Table 1, a wax and a tackifier were used in one.
After heating and melting to 80 ° C., a predetermined amount of polymer is gradually added while stirring with a stirrer (when an antioxidant is added, it is performed simultaneously with the addition of wax and tackifier). Dissolve the polymer completely and prepare the hot melt adhesive.

In Table 1, the number of each composition is represented by weight.
%, And the unit of the coating amount is g / m^TwoIt is. How to make a heat-sensitive label Heat the obtained adhesive to 180 ° C and apply it to double-sided art paper.
Application amount 7 to 15 g / m ^TwoGravure coater
Coating to create a thermal label.

[0034] The coated article was subjected to a blocking property test. Adhesion method of thermal label to glass bottle Thermal label machine (Model HL manufactured by EDM Co., Ltd.)
Using -3), the sticking roll temperature: 140 ° C. to 150
° C, air heater set temperature: 650 ° C (glass bottle supply speed: about 60 to 80 bottles / min). The size of the label is 3cm x 6cm. The bottle used was a beer bottle at 85 ° C
What was immersed in a -3 wt% NaOH aqueous solution for 30 minutes and washed well with water was used. At the time of bonding, an empty bottle was placed in a 40 ° C. oven and heated. <Test Method> Blocking property Ten heat-sensitive labels each having a size of 4 cm × 5 cm are stacked, placed on a 5 kg weight, and placed in an oven at 40 ° C. After 24 hours, the heat-sensitive label is taken out, the heat-sensitive label is peeled off, and the blocking property is examined from the sense of resistance when peeled off.

When the sheet was peeled off and the sheet was peeled off by force, it was evaluated as x. Adhesive force The beer bottle label 30 minutes or more after the adhesion was peeled off, and the peeled state was observed.

In the case of peeling at the interface, the evaluation was x, and in the case of paper tear, the evaluation was o. Condensation resistance After placing the sample adhered to the beer bottle in a freezer at -17 ° C for 1 hour, put it in a constant temperature / humidity bath at 25 ° C and 40% humidity to dew on the surface, and when sufficient dew condensation occurs, label Was peeled off, and the label was evaluated as x when the label was peeled off at the interface, and as o when the label was broken. Alkali peelability Sample adhered to beer bottle is 85 ℃ -3wt% NaO
The label was peeled off by being immersed in an H aqueous solution for 30 minutes while rotating the bottle. When no glue was left on the bottle or label, it was evaluated as 、, and when it was not peeled off, and when glue was left on the bottle or label even after peeling, it was evaluated as x. Jamming property Thermal label machine (Model LR-, manufactured by Koyo Machine Co., Ltd.)
400KC), and a jamming test was performed. The size of the label was 6 cm × 10 cm, and the label supply speed was 350 sheets / min. When jamming occurred at the time of cutting the label, it was evaluated as x, and when there was no problem, it was evaluated as o. <Comparative Examples 1 to 4> Thermosensitive labels were prepared using the hot melt adhesives shown in Table 1 and described as Comparative Examples. The conventional one has no problem in the blocking property, but has a problem in the adhesiveness, dew-condensation, alkali peeling property and the like.

[0037]

[Table 1]

[0038]

According to the present invention, the heat-sensitive label is easily peeled from the adherend by dipping in an alkaline aqueous solution or spraying with an alkaline aqueous solution, and the adhesive is hot-melt-type bonded without leaving any adhesive on the bottle or label base material. Thermal labels can be provided in which the agent is dispersed or dissolved in an aqueous alkaline solution.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshiaki Takenaka 2-3-1-13 Kyobashi, Chuo-ku, Tokyo Inside Toyo Ink Manufacturing Co., Ltd.

Claims (6)

[Claims] A hot melt type adhesive containing a polymer having an acid value of 90 mg KOH / g or more is coated on a label substrate in an amount of 7 to 15 g /
thermal label characterized by comprising m ² provided. 2. The composition according to claim 1, which contains a polymer, a tackifier and a wax, and has an acid value of 100 mg KOH / g or more.
A heat-sensitive label using the hot-melt adhesive described in the above. 3. The tackifier has an acid value of 150 mg KO.
3. The heat-sensitive label according to claim 2, wherein the heat-sensitive label contains at least one kind of H / g or more. 4. The method according to claim 1, wherein the polymer comprises an ethylene- (meth) acrylic acid copolymer.
Thermal label according to any of the above. 5. A hot-melt adhesive for heat-sensitive labels, comprising a polymer having an acid value of 90 mg KOH / g or more and being dispersed or dissolved in an aqueous alkali solution. 6. A method for peeling a heat-sensitive label according to claim 1, wherein said heat-sensitive label is affixed to an adherend with an aqueous alkaline solution.