JP2009221291A - Adhesive composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide such an adhesive composition that, as to packaging containers obtained by applying a label on containers, ordinary consumers can easily peel the labels off the packaging containers and separate the labels and the containers without conducting any special treatment, to provide a label coated with such an adhesive composition, to provide a packaging container obtained by applying such a label onto the container, and to provide a method for producing such a packaging container. <P>SOLUTION: The adhesive composition comprises (A) a water-dispersible polymer with a glass transition temperature of 40°C or lower and (B) a water-swelled crosslinked starch heat-treated with water at a temperature beginning its gelatinization or higher. The label obtained by applying the above adhesive composition is highly easily peelable. The packaging container obtained by applying the label on the container enables easily separating the label and the container, thus being highly recyclable. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a packaging container used for storing alcoholic beverages, soft drinks, seasonings and the like distributed to general consumers, for example, mainly in containers such as bottles and cans. The present invention relates to a packaging container obtained by attaching a manufactured label. More specifically, the present invention relates to a packaging container obtained by attaching a label to a container, which is required from the market in recent years, and the general consumption without any special treatment in view of the recyclability of the container. An adhesive composition that enables a person to easily peel the label from the packaging container and separate the label from the container, and easy peeling obtained by applying such an adhesive composition The present invention relates to a packaging container obtained by sticking such an easily peelable label to such containers as bottles and cans, a method for producing such a packaging container, and the like.

  Examples of packaging containers for alcoholic beverages distributed to general consumers include beer bottles. Regarding beer bottles, even if beer bottles are distributed to general consumers, and even if beer bottles are distributed in restaurants, etc., a collection system for beer bottles after use has already been established and recycled. Therefore, the label is peeled off from the beer bottle, and the beer bottle is reused.

  By the way, beer bottles are exposed to various environments when they are distributed by general consumers and restaurants. For example, beer bottles are immersed in water to cool, and after being stored in a refrigerator, they are taken out to room temperature to cause condensation. Even in such a case, the label affixed to the beer bottle must not peel from the beer bottle. Therefore, the adhesive used for a label attached to a beer bottle generally has water resistance.

In addition, beer bottles are distributed from beer factories to dealers, for example, impact and friction are applied to beer bottle labels when transported, and when a person handles the beer bottle, impact and friction are similarly applied to the label. May join. Therefore, it is also necessary to adhere the label to the beer bottle with an adhesive having an adhesive strength that can sufficiently withstand such physical peeling force that may occur on the label.
Therefore, the label is usually firmly adhered to the beer bottle, and it is generally not easy to peel off such a label from the beer bottle.

In order to peel off this tightly bonded label and reuse the beer bottle, the beer bottle is usually subjected to the following sequence of steps:
(I) the beer bottle is immersed in warm, strongly alkaline water;
(Ii) The adhesive swollen and softened by the alkali heating treatment is sprayed with water at a high pressure to remove the label from the beer bottle; and (iii) the adhesive remaining on the beer bottle is removed with a brush. Scrub with etc.

Performing a series of steps as described above for recycling beer bottles has problems in terms of cost and productivity, for example, in the following points:
(I) requires a lot of equipment,
(Ii) Occupational health and safety hazards due to use of warmed strong alkaline water,
(Iii) Consideration of equipment against corrosion is necessary, and (iv) It takes time.
Therefore, at present, the recycling of beer bottles is an extremely heavy burden for beer companies and the like.

  For beverage containers other than beer bottles that are generally distributed, the label on the packaging container must not be peeled off from the packaging container as in the case of beer bottles, even if it is immersed in water or condensation occurs. Also, the label should not be peeled off by impact or friction that can be applied during the distribution of the packaging container. Therefore, the label is generally firmly adhered to other packaging containers handled by general consumers as in the case of beer bottles.

The beer bottle is reused by the processing by the series of steps as described above. However, this is not the case for other packaging containers. Other packaging can be treated in the same way as beer bottles, but it is usually difficult for the following reasons:
(I) Other packaging containers distributed to general consumers have various shapes. Since the above-described series of steps is usually performed using mechanical equipment, the degree of freedom (correspondence) with respect to the shape is poor. Modification or change of the mechanical equipment to cope with containers of various shapes causes an increase in cost and a decrease in productivity, which is not realistic. Therefore, the above-described series of steps can be applied only to limited-shaped packaging containers (for example, beer bottles and sake sake bottles); and (ii) the above-described series of steps are immersed in strong alkaline water. There is a step of swelling and softening the adhesive. Therefore, the above-described process cannot be used unless the container is made of a material that can withstand this alkali heating treatment. In other words, there are also restrictions on the material of the container. Therefore, the above-described process is not practically usable for recycling containers other than glass containers.

  However, in recent years, other general packaging containers other than beer bottles handled by general consumers have been established due to the progress of separate collection of household waste and the establishment of a system for collecting and recycling each container for each material. However, there is an increasing demand for recyclability. Accordingly, there is an increasing need to provide a packaging container that can easily separate labels and containers even in ordinary households.

  On the other hand, food manufacturers such as beverage manufacturers and seasoning manufacturers that provide products using these packaging containers are worried that the labels may be peeled off from the packaging containers in the course of distribution. This is because the label can contain extremely important information that is legally essential, such as the labeling of the contents to be put in the packaging material and the indication of the expiration date for food.

  Therefore, for example, Patent Document 1 discloses a packaging container in which the adhesive strength of the adhesive is reduced and the label can be peeled from the packaging container by being heated to a predetermined temperature or higher or receiving light irradiation having a predetermined intensity or higher. Disclose.

  In Patent Document 1, as an adhesive whose adhesive strength is reduced when heated to a predetermined temperature or higher, a water-soluble adhesive is used as a base, and a powdery powder having a melting point of 40 to 100 ° C. such as wax, amide compound, and bisphenol is added thereto. And an adhesive prepared by mixing a hot melt adhesive having a softening temperature of 40 to 100 ° C. such as vinyl acetate, polyamide, polyester and urethane. Patent Document 1 discloses a positive photoresist adhesive such as a mixture of cresol novolac and naphthoquinone diazide based on a water-soluble adhesive as an adhesive whose adhesive strength is reduced when irradiated with light of a predetermined intensity or more. An adhesive comprising is disclosed.

  For example, Patent Document 2 discloses a peelable adhesive composition (water peelable adhesive composition and heat-release peelable adhesive composition) in which adhesive strength decreases after water absorption and a method for producing the same.

Patent Document 2 discloses a hot-melt adhesive, a solvent-based adhesive, a photocurable adhesive, a one-component thermosetting adhesive, and a two-component thermosetting adhesive as such a peelable adhesive composition. Water absorption of starch-based resin, polyacrylic acid-based resin, polyvinyl alcohol-based resin, polyacrylamide-based resin, and polyoxymethylene-based resin with respect to 100 parts by weight of the base adhesive such as the adhesive and pressure-sensitive adhesive (adhesive) A peelable adhesive composition containing 1 to 200 parts by weight of a crosslinkable polymer is disclosed.
Patent Document 2 further discloses an adhesive containing thermally expandable particles enclosing a surfactant, a heat-foamable gas or a liquid.

  For example, Patent Document 3 is formed from an adhesive containing a polymer having a first-order melt transition occurring over a temperature range narrower than 15 ° C. and a pressure-sensitive adhesive, and the polymer is 40 to 70 parts by weight of docosyl acrylate. And 30 to 50 parts by weight of stearyl acrylate, 1 to 5 parts by weight of acrylic acid and 5 to 15 parts by weight of dodecyl mercaptan, the polymer being contained in the adhesive composition in an amount of 1 to 50% by weight. An easily peelable label for a packaging container is disclosed.

  In addition, as such an adhesive, a polymer having a specific melting point or primary transition temperature (first melting transition) is partially miscible in the adhesive so that phase separation crystallization is possible. Used in pressure adhesive.

  However, the method of reducing the adhesive strength of the label by light irradiation or heat disclosed in Patent Document 1 always requires a light irradiation device or a heating device when peeling. Therefore, in order for a general consumer to carry out at home, such a heating device and a light irradiation device are necessary, and these devices are expensive, lack practicality and versatility, and are unrealistic. In particular, light irradiation requires light to reach the adhesive layer, and applicable packaging containers are limited to those in which labels and containers themselves can transmit light. In addition, the method of reducing the adhesive force by heating is susceptible to the degree of adhesive force depending on the degree of heating, and the label itself may be broken depending on the strength of the label itself, and the applicability to various labels is low.

  Moreover, although the method of reducing adhesive force by immersion in water which patent document 2 discloses can be used in a general household, there exists a problem that adhesive force is influenced by the immersion time and water temperature in water. Furthermore, when the label itself absorbs water, such as when the label is made of paper, the strength of the label itself is reduced, so that it is difficult to peel the label from the container. Moreover, when time to immerse in water requires a long time, it lacks simplicity. Furthermore, as explained in the case of beer bottles, when a packaging container is soaked in water or when condensation occurs in the packaging container, the adhesive force may change, peeling of the label, etc., and reliability when the packaging container circulates. There is a problem.

  Furthermore, in any method in which the adhesive strength is reduced by performing treatments such as light irradiation, heating, and water immersion, the adhesive layer is softened by each treatment to reduce the adhesive strength. Often causes cohesive failure. Therefore, the adhesive tends to remain in the container, and the adhesive can be mixed as an impurity when the container is recycled. Therefore, there is a problem that it is necessary to treat the residual adhesive with a brush or the like.

  Conventionally, many adhesives containing water-soluble polymers such as starch, polyvinyl alcohol, and casein have been suitably used for applications that do not require easy peelability. When these adhesives are stored at low temperatures (for example, about 5 ° C) in winter, the viscosity of the adhesives tends to become extremely unstable, and the adhesive is applied to the label and the continuous production of stable packaging containers is performed. There is a problem of causing trouble. When the adhesive composition having easy peelability disclosed in Patent Documents 1 to 3 contains these water-soluble polymers, similarly, the viscosity of the adhesive becomes unstable when stored at a low temperature. It can easily cause similar problems. Furthermore, many adhesives whose adhesive strength is reduced by heat and light require management and attention to heat and light even during storage of the adhesive.

  Therefore, in order to produce a stable packaging container throughout the year using these adhesives, there is a problem that a great deal of management and attention regarding temperature, heat, light, etc. are required.

JP-A-4-35083 International Publication No. WO2002 / 055626 Pamphlet Japanese Patent No. 3717584

  The present invention has been made to solve the above problems, and the purpose of the packaging container obtained by sticking a label on the container is not subjected to any special treatment by a general consumer. An adhesive composition that enables easy separation of the label from the packaging container and separation of the label from the container, an easily peelable label obtained by applying such an adhesive composition, It is providing the packaging container obtained by sticking such an easily peelable label to containers, such as a bottle and a can, and the manufacturing method of such a packaging container.

  Such a packaging container is highly versatile, and the adhesive composition has a stable adhesive force even if condensation or the like may occur in the process of circulation of the packaging container. It is preferable that it can be maintained. Furthermore, when the label is peeled from the packaging container, the adhesive stays on the label side, and not much remains on the container side. Therefore, it is preferable that the container is excellent in recyclability, such as excellent cleaning properties of the container thereafter. Moreover, since it is excellent also in the storage stability at the time of storage, such as low temperature, it is preferable that a packaging container can be manufactured and provided stably.

  As a result of intensive investigations, the present inventors have mixed a water-dispersible polymer with controlled hardness and specific starch to improve mechanical suitability (or coating workability) and have appropriate adhesive strength. However, it was found that an adhesive composition excellent in easy peelability and storage stability could be obtained, and the present invention was completed.

That is, the adhesive composition of the present invention is
(A) a water dispersible polymer having a glass transition temperature of 40 ° C. or lower;
(B) a water-swelled crosslinked starch heat-treated with water at a temperature equal to or higher than the gelatinization start temperature,
Comprising.
This adhesive composition can be suitably produced on a packaging container by applying it to a label and applying it to a container. Therefore, a packaging container has an adhesive bond layer formed using the adhesive composition concerning this invention between a label and a container.

In this specification, the glass transition temperature (Tg) is a thermal flow rate differential scanning calorimeter for a resin film having a thickness of about 0.5 mm obtained by drying a water-dispersible polymer at 20 ° C. for 1 week. (DSC-50 type (trade name) manufactured by Shimadzu Corporation) is used to increase the temperature at a rate of 5 ° C./min to obtain a DSC curve, and the temperature at the inflection point of the DSC curve is taken as the measured value.
The gelatinization start temperature is a temperature at which solid starch starts to change into a paste. The gelatinization start temperature is measured with a plastogram or a microscope.
The water swelling state is a state in which starch is not dissolved uniformly in water but sucks water.

  (B) Water-swelled crosslinked starch heat treated with water at a temperature equal to or higher than the gelatinization start temperature (hereinafter also referred to as “(B) water-swelled crosslinked starch”) is phosphoric acid treatment, epoxy treatment or adipic acid It is preferably a crosslinked starch crosslinked by treatment.

  In addition, (B) the water-swelled crosslinked starch preferably has a water absorption ratio of 5 or less before the water-swelled state.

  Moreover, it is preferable that the said adhesive composition contains the hydrophobized starch of the water swelling or aqueous solution state further heat-processed with water at the temperature more than gelatinization start temperature.

  The above-mentioned (A) water-dispersible polymer having a glass transition temperature of 40 ° C. or lower (hereinafter referred to as “(A) water-dispersible polymer”) is preferably a rubber latex.

  The above-mentioned (A) water-dispersible polymer is more preferably styrene butadiene rubber (SBR) latex.

  Moreover, the above-mentioned (A) water-dispersible polymer may be an acrylic resin emulsion.

The adhesive composition according to the present invention is:
(A) a water dispersible polymer having a glass transition temperature of 40 ° C. or lower;
(B) a water-swelled crosslinked starch heat-treated with water at a temperature equal to or higher than the gelatinization start temperature,
Since it contains, it is excellent in mechanical suitability, has an appropriate adhesive strength, is excellent in easy peelability, and is excellent in storage stability.
And the packaging container in which the label was stuck using such an adhesive composition is excellent in recyclability.

The adhesive composition is further excellent in pH stability when (B) the water-swelled crosslinked starch is a crosslinked starch crosslinked by phosphoric acid treatment or epoxy treatment.
The adhesive composition (A) is more flexible and has a lower tack when the water-dispersible polymer is rubber latex.
When the glass transition temperature (Tg) of the rubber latex is −70 ° C. to + 40 ° C., the adhesive composition becomes more flexible and has a lower tack.

When the rubber latex is a styrene butadiene rubber (SBR) latex, the adhesive composition has low polarity and is excellent in releasability from a container such as glass.
When the adhesive composition (A) is a water-dispersible polymer that is an acrylic resin emulsion, the film is more easily hardened and has excellent peelability due to hardness.
When the Tg of the acrylic resin emulsion is −40 ° C. to + 30 ° C., the adhesive composition has a more appropriate film hardness and is more excellent in peelability.

  The present invention has excellent effects as described above, and the reason thereof is considered as follows, but the present invention is not limited at all by these reasons.

  The packaging container of the present invention has an adhesive layer between the label and the container, and the adhesive layer contains (A) a water-dispersible polymer and (B) a crosslinked starch in a water-swelled state. It is manufactured using the adhesive composition. While water is present in the adhesive layer, (B) water-swelled crosslinked starch which is a highly polar component in the adhesive layer with respect to the surface of the label or container which is a highly polar material However, it is considered that it acts effectively and gives excellent adhesiveness to the adhesive layer by giving good adhesion to the label or the container.

  At the same time, (B) the water-swelled crosslinked starch dominates the fluidity of the adhesive composition according to the present invention. Therefore, when the packaging container according to the present invention is produced, the crosslinked starch is The specific coating suitability suitable for the machine in which the adhesive composition is used can be imparted to the adhesive composition.

  In addition, (B) the water-swelled crosslinked starch in the adhesive composition is usually obtained by heating the crosslinked starch to a temperature equal to or higher than the gelatinization start temperature of the crosslinked starch in the presence of water. can get. In addition, before performing such heat processing, this crosslinked starch has a powdery form. By this heat treatment, the cross-linked starch does not dissolve uniformly in water at the molecular level, but becomes a form that swells by absorbing moisture. In general, water-based adhesives containing starch dissolved in water and many water-based adhesives containing water-soluble polymers cause an increase in the viscosity of the entire adhesive, which is thought to be caused by the formation of hydrogen bonds at low temperatures. It is known that it tends to be in a non-fluid state called "." On the other hand, in the adhesive composition according to the present invention, the cross-linked starch has a swollen form that absorbs moisture as described above and does not dissolve uniformly in water. It is hard to produce and it is hard to be in a state without fluidity. Moreover, since the adhesive composition according to the present invention does not substantially react or change due to light or heat, it is excellent in viscosity stability during long-term storage or storage temperature.

  Thereafter, when a packaging container having an adhesive layer formed using the adhesive composition according to the present invention is cured between the label and the container, moisture gradually diffuses or volatilizes from the adhesive layer, and finally Dissipate. In the process of moisture dissipation, the water dispersible polymer (A) contained in the adhesive composition forms a continuous phase. On the other hand, (B) the water-swelled crosslinked starch imparts excellent adhesiveness to the adhesive layer by having good adhesion to the label or packaging container at the initial stage of adhesion, and water dissipates. In the process, the water does not swell and changes to extremely hard polymer particles. Therefore, the crosslinked starch forms a particulate dispersed phase, that is, a domain-like discontinuous phase, in the continuous phase formed of the above-mentioned (A) water-dispersible polymer in the adhesive layer.

  During the process of moisture dissipation, the volume of the adhesive layer shrinks with the dissipation of moisture at the interface between the label or container and the adhesive layer, so that stress (ie, strain) is generated inside the adhesive layer. At the same time, as described above, the (A) water-dispersible polymer, which is a low polarity component contained in the adhesive composition according to the present invention, forms a continuous phase. Chemical affinity is impaired at the interface between the container and the adhesive layer where the penetration of components and the physical anchoring effect are small. Thus, the distortion due to internal stress generated inside the adhesive layer and the loss of chemical affinity give the effect of reducing the adhesiveness of the adhesive layer. Furthermore, (B) the cross-linked starch in a water-swelled state, which has become extremely hard polymer particles in the adhesive layer due to the dissipation of water, is finally in the adhesive layer in the same manner as the filler (or filler) component. It becomes a foreign matter and physically gives the adhesive layer a peelability. Therefore, by using the adhesive composition according to the present invention, the final adhesion to the label or the container, particularly to the container, can be controlled relatively freely by the composition of the adhesive composition.

  Furthermore, by using the adhesive composition according to the present invention, finally, (A) the water-dispersible polymer forms a low-polarity continuous phase after the dissipation of moisture, and the adhesive layer has a polarity as a whole. Lower. Therefore, the adhesive layer formed by the adhesive composition according to the present invention is difficult to absorb a large amount of highly polar water, and the adhesive layer is difficult to soften due to moisture, and thus has excellent water resistance and moisture resistance. . Therefore, the packaging container according to the present invention can also have water resistance such that the adhesive force of the adhesive layer hardly changes due to condensation that occurs in the packaging container after processing after refrigerated storage. Furthermore, since these (A) water-dispersible polymers form a film simultaneously with the fusion of the polymer particles, they are excellent in initial adhesive force in the label adhering process as compared with an adhesive mainly composed of a normal water-soluble polymer. .

BEST MODE FOR CARRYING OUT THE INVENTION

  The adhesive composition according to the present invention comprises (A) a water dispersible polymer having a glass transition temperature (Tg) of + 40 ° C. or less ((A) a water dispersible polymer) and (B) a temperature equal to or higher than the gelatinization start temperature. Contains water-swelled crosslinked starch ((B) water-swelled crosslinked starch) heat-treated with water.

The (A) water-dispersible polymer is a film formed by fusing particles at room temperature, and is particularly limited as long as the adhesive composition according to the present invention can be obtained. Absent.
(A) As a water-dispersible polymer, generally, for example, flexibility can be imparted to an adhesive layer formed from an adhesive composition, and (A) a water-dispersible polymer. A rubber latex having high cohesive strength is preferred.

Examples of such rubber latex include natural rubber, nitrile rubber, chloroprene rubber, styrene butadiene rubber (SBR), and aqueous dispersions of these (meth) acrylic modified products. Among these, it is particularly preferable to use SBR latex having a low polarity.
The Tg of the rubber latex is preferably −70 ° C. to 40 ° C., more preferably −50 ° C. to 30 ° C., and particularly preferably −40 ° C. to 20 ° C.

In addition, (A) an acrylic resin that can control the polarity and cohesion relatively freely by combining various monomers, although not as much as the styrene butadiene copolymer latex in terms of polarity and cohesion as a water-dispersible polymer. System emulsions can be used.
These acrylic resin emulsions can be obtained by combining and polymerizing various monomers having a polymerizable double bond such as general acrylic ester monomers, methacrylic ester monomers, and styrene monomers. There is no particular limitation.

As a monomer having such a polymerizable double bond, for example,
Formula (I) CH ₂ = CR ¹ COOR ²
(Wherein R ¹ is hydrogen or a methyl group, R ² is an alkyl group having 1 to 18 carbon atoms), and R ² is a methyl group, an ethyl group, a propyl group, a butyl group, an isobutyl group, or an isoamyl group. (Meth) acrylic acid alkyl esters such as hexyl group, heptyl group, 2-ethylhexyl group, isooctyl group, isononyl group, isodecyl group, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, (Meth) acrylates such as t-butylcyclohexyl (meth) acrylate, vinyl esters such as vinyl acetate, vinyl versatic acid, vinyl propionate, vinyl pivalate, glycidyl (meth) acrylate, 2- (meth) acrylic acid 2- Hydroxyethyl, 2-hydroxypropyl (meth) acrylate, etc. Hydroxyl group-containing monomers, N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidone, N-vinyl-2-pyrrolidone, acrylamide, methacrylamide, N, N-dimethyl (meth) acrylamide, diacetone acrylamide, etc. Amide group-containing monomers, styrene, styrene derivatives, dienes such as ethylene, acrylonitrile, butadiene, and hexadiene, and as an internal crosslinking agent, methylene bisacrylamide, 1,6-hexanediol di (meth) acrylate, trimethylol Examples include polyfunctional acrylic monomers such as propane tri (meth) acrylate and monomers having two or more unsaturated double bonds per molecule such as diallyl phthalate, divinyl benzene, and triallyl cyanurate. it can.
These monomers can be used alone or in combination.

  However, when the Tg of the produced polymer is extremely low, the adhesiveness of the adhesive composition used in the present invention is too strong due to this polymer component, and the easy peelability tends to decrease. The Tg of the polymer of the emulsion is preferably -50 ° C to 40 ° C, particularly preferably -40 ° C to 20 ° C, and most preferably -30 ° C to 10 ° C.

  An acrylic resin emulsion can be used as the (A) water-dispersible polymer according to the present invention. These acrylic resin emulsions include polymerizable monomers such as general acrylic ester monomers, methacrylic ester monomers, styrene monomers, vinyl acetate monomers such as vinyl acetate, allyl group-containing monomers, and ethylene monomers. It can be obtained by combining various monomers having a double bond and allowing the polymer to exist in an aqueous dispersion in an aqueous medium by a known polymerization method.

Moreover, rubber latex can be used as (A) water-dispersible polymer. Examples of these rubber latexes include natural rubber, nitrile rubber, chloroprene rubber, styrene butadiene rubber, and aqueous dispersions of these (meth) acrylic modified products.
As such (A) water-dispersible polymer, for example, commercially available products include Yodosol AD199 and AD205 (trade name) manufactured by NSC Japan, and Nipol 1571C (trade name) manufactured by Nippon Zeon Co., Ltd. be able to.

  Among these, it is particularly preferable to use SBR latex having a low polarity. Examples of commercially available SBR latex include L7430 and DL620 (trade name) manufactured by Asahi Kasei Corporation, and LX426 (trade name) manufactured by ZEON Corporation.

  (B) The crosslinked starch in a water-swelled state is obtained by heating the crosslinked starch in the presence of water at a temperature equal to or higher than the gelatinization start temperature of the crosslinked starch, and the adhesive according to the present invention There is no particular limitation as long as the composition can be obtained. By performing the above heat treatment, the crosslinked starch becomes (B) a crosslinked starch in a water-swelled state, and the obtained (B) crosslinked starch in a water-swelled state is not uniformly dissolved in water at the molecular level, A swollen form that absorbs a large amount of water. In addition, (B) the water-swelled crosslinked starch is more preferably one that can become extremely hard polymer particles along with the dissipation of water after adhesion.

  (B) In order to prevent (B) water-swollen crosslinked starch from being uniformly dissolved in water at the molecular level by heat treatment applied to obtain a water-swollen crosslinked starch, (B) water The swollen crosslinked starch is subjected to a crosslinking treatment. The crosslinking treatment is not particularly limited as long as the (B) water-swelled crosslinked starch swells with water but does not dissolve in water. For example, phosphoric acid treatment, epoxy treatment or Adipic acid treatment is preferred, phosphoric acid treatment or epoxy treatment is more preferred, and phosphoric acid treatment is most preferred.

The cross-linked starch raw material starch used in the present invention is preferably as narrow as possible with a narrow particle size distribution and an appropriate average particle size.
The cross-linked starch used in the present invention is preferably a cross-linked starch obtained by cross-linking the raw material starch with any cross-linking agent such as epichlorohydrin, phosphorus oxychloride, metaphosphate, and adipic anhydride, and epichlorohydrin or metaphosphoric acid. A cross-linked starch cross-linked with a salt (for example, sodium trimetaphosphate) is more preferable.
(B) As a commercial item of the crosslinked starch for obtaining the crosslinked starch of a water swelling state, PB5000 and PB2000 (brand name) by Nissho Chemical Co., Ltd. etc. can be illustrated, for example.

  The adhesive composition according to the present invention comprises (A) a water-dispersible polymer and (B) a water-swelled crosslinked starch, (A) water-dispersible polymer / (B) a water-swelled crosslinked starch (weight ratio). = 95/5 to 30/70, preferably 90/10 to 40/60, more preferably 80/20 to 60/40. Here, the weight ratio refers to the ratio of each solid content.

The adhesive composition according to the present invention further comprises (C) a hydrophobized starch in a water swollen or aqueous solution state (hereinafter referred to as “(C) water swollen or aqueous solution state) heat-treated with water at a temperature equal to or higher than the gelatinization start temperature. Hydrophobized starch ”).
(C) Hydrophobized starch in a water swollen or aqueous solution state is obtained by heating hydrophobized starch in the presence of water at a temperature equal to or higher than the gelatinization start temperature of the hydrophobized starch. There is no particular limitation as long as the adhesive composition according to the invention can be obtained.

  (C) As the hydrophobized starch in a water-swelled or aqueous solution state, those having a high hydrophobic group modification amount are preferred, and those having a metal cross-linked structure are particularly preferred.

  Examples of such (C) hydrophobized starch in water swelling or aqueous solution include octenyl succinate esterified starch. (C) As a commercially available product of hydrophobized starch for obtaining hydrophobized starch in a water swollen or aqueous solution state, for example, Dry FLO PC (trade name) manufactured by NSC Japan, Flashgen manufactured by Nissho Chemical Co., Ltd., Examples of the milky white and milky white W (trade name) can be given.

  The adhesive composition according to the present invention includes (C) a water-swelled or aqueous-hydrophobized starch, (A) a water-dispersible polymer, (B) a water-swelled crosslinked starch, and (C) a water-swelled or aqueous solution. 1 to 80 parts by weight, or 5 to 30 parts by weight, based on the total (100 parts by weight) of the hydrophobized starch. The adhesive composition according to the present invention includes (C) water-swelled or hydrophobized starch in an aqueous solution state, so as to extremely increase the polarity of the system without increasing the adhesion to a container such as a glass bottle, Since the viscosity can be controlled appropriately, the mechanical suitability can be further improved. Here, a weight part means each solid content.

  The adhesive composition of the present invention can further contain other additives. Such an additive is generally used with respect to the adhesive composition and is not particularly limited as long as it can be used in the adhesive composition of the present invention. Examples of such additives include casein; various cellulose derivatives such as methyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose; polyvinyl alcohol, isobutylene maleic anhydride copolymer resin, styrene maleic anhydride copolymer resin, polyoxyethylene, polyethylene glycol, and the like. Various water-soluble polymers; various rosin-based, terpene phenol-based and petroleum resin-based tackifier resins; zirconium compound and zinc oxide metal cross-linking agents; antifoaming agents, preservatives, pH adjusters, metal chelating agents, etc. be able to.

  The components of the adhesive composition used in the present invention as described above can be appropriately selected and changed depending on the type of each material such as a label and a container constituting the packaging container.

As described above, the adhesive composition according to the present invention includes (A) a water-dispersible polymer and (B) a crosslinked starch in a water-swelled state. Since both (A) the water-dispersible polymer and (B) the water-swelled crosslinked starch usually contain an aqueous medium, the adhesive composition according to the present invention usually also contains an aqueous medium, which is aqueous (or aqueous). It is an adhesive composition.
In the present specification, “aqueous” means a state in which polymer particles are present in an aqueous medium, preferably a state in which they are dispersed (even if a water-soluble polymer that partially dissolves in water is included). Good) and therefore includes both polymer particles and an aqueous medium. “Aqueous medium” mainly refers to so-called water such as distilled water, ion-exchanged water, and pure water, but appropriately includes water-soluble organic solvents such as glycerin, propylene glycol, acetone, and lower alcohols. In addition, in the present specification, “solid content of the adhesive composition” means “evaporation residue” obtained by evaporating an aqueous medium from an adhesive composition at 105 ° C. for 3 hours, as described in Examples below. Thus containing no aqueous medium.

  The solid content concentration of the adhesive composition according to the present invention is not particularly limited as long as the adhesive composition and the adhesive layer having the intended properties of the present invention can be obtained. It is preferably 80 to 5% by weight, more preferably 60 to 10% by weight, and particularly preferably 50 to 30% by weight.

  The “label” used in the packaging container of the present invention is generally referred to as “label”, and the adhesive composition according to the present invention is applied to dissipate moisture from the label. If there is, there is no particular limitation. Examples of such labels include those made of materials such as paper, synthetic resin film, aluminum, and composite films obtained by laminating them, and those that can adhere to a container and dissipate moisture. can do. Some information is usually displayed on one or both sides of these labels.

Moreover, the container used in order to manufacture the packaging container of this invention will not be restrict | limited especially if the packaging container which concerns on this invention can be obtained. Such containers may be, for example, bottles, bottles, cans, bags, etc. made of glass, synthetic resin such as PET and polypropylene, and metal, and various resin coatings may be applied to their surfaces. Examples thereof include those obtained by attaching a shrink film made of PET, those subjected to a printing process, and the like.
These containers are generally distributed and are not particularly limited as long as the packaging container according to the present invention can be obtained. If the surface of the container has a large roughness, the adhesion of the adhesive layer to the container surface will increase due to the anchoring effect of the adhesive layer after the label and container are bonded, and the easy peelability of the label will be impaired. Therefore, the surface of the container is preferably smooth.

The adhesive composition described above is applied to the label to form an adhesive layer on the label. The method and apparatus for applying (or coating) the adhesive composition to the label are generally adhesives such as spray coating, nozzle coating, dip coating, roll coating, gravure coating, rolling coating, brush coating, etc. Any application method and applicator used to apply the composition to the label can be used. Such a coating method and a coating apparatus can be appropriately selected in consideration of the viscosity and viscosity of the adhesive composition according to the present invention, and the coating can be applied to the label with the adhesive composition according to the present invention. As long as it is a method and a coating apparatus, it can be used without particular limitation.
In the field of manufacturing packaging containers for beverages and seasonings, a packaging container manufacturing line including a vertical or horizontal roll coating apparatus generally called a labeler is used. Since the adhesive composition according to the present invention has particularly high applicability to these vertical or horizontal roll coating apparatuses, it is particularly preferable to use these coating apparatuses.

The coating amount of the adhesive composition to the label, in general, is preferably from 3~40g / ^{m 2,} more preferably from ^{5~20g / m 2, 7~15g / m} 2 It is particularly preferred that The amount applied to the label of the adhesive composition can be appropriately changed using the above-described coating apparatus.
Here, the application amount of the adhesive composition means the amount of the adhesive composition itself containing water.

The adhesive composition according to the present invention is applied to a label, and the thickness of the adhesive layer formed by dissipating moisture is preferably 1 to 35 μm, more preferably 3 to 20 μm. It is especially preferable that it is ˜15 μm.
The adhesive layer according to the present invention preferably has the thickness of the above-mentioned adhesive layer. In this case, the crosslinked starch in the water-swelled state (B) according to the present invention is extremely hard while moisture is dissipated after bonding. It is considered that it becomes polymer particles and becomes a particulate dispersed phase in the adhesive layer and can form a discontinuous phase in a domain shape. (B) When the particle diameter of the particulate dispersed phase formed from the crosslinked starch in the water-swelled state is close to the thickness of the entire adhesive layer, or is appropriately larger than the thickness of the entire adhesive layer, it is more effective in the adhesive layer. It is thought that it becomes a foreign material and exhibits a physical peeling effect. Accordingly, (B) the diameter of the particles formed from the water-swelled crosslinked starch is preferably 1 to 30 μm, more preferably 3 to 20 μm, and particularly preferably 5 to 15 μm.

When the coating amount of the adhesive composition applied to the label is more than 40 g / m ² , (B) the adhesive formed from the adhesive composition based on the diameter of the particles formed from the water-swelled crosslinked starch It is believed that the layer thickness increases and the delamination effect by the particles can be weakened. On the contrary, when the coating amount of the adhesive composition is less than 3 g / m ² , the thickness of the entire adhesive layer is smaller than the diameter of the particles formed from (B) the water-swelled crosslinked starch, It is considered that the peeling effect by the particles can be strong. In addition, moisture drying or drying due to permeation is too early, which may impede the bonding process practically.

  In the adhesive composition according to the present invention, in addition to controlling the coating amount of such an adhesive composition, (i) (B) the diameter of the particles formed from the water-swelled crosslinked starch is controlled. (Ii) controlling the abundance ratio (weight ratio) of (A) the water-dispersible polymer and (B) the water-swelled crosslinked starch, (iii) controlling the phase structure of the adhesive layer, and (Iv) The adhesive force of the adhesive layer is controlled by controlling the polarity of the adhesive layer.

  As described above, the adhesive composition is applied to one side of the label to form an adhesive layer, and the label is applied to the container until the moisture in the adhesive layer is dissipated, and then the moisture is removed from the adhesive layer. Is dissipated to obtain the packaging container according to the present invention.

  Since the adhesive force between the label of the packaging container according to the present invention thus produced and the container can be controlled by the composition of the adhesive composition as described above, the intended use of the packaging container Depending on the type, packaging containers can be manufactured.

  Therefore, in the distribution process until the contents of the packaging container are consumed, such as during storage and transportation of the packaging container, the label of the packaging container is not dropped off from the packaging container and partially peeled off. First, after the contents of the packaging container are consumed, the packaging container is not subjected to any special treatment, and can be easily packaged by hand, such as a brush or a spatula, which can be easily obtained at home. The container can be separated by peeling the label from the container.

  In addition, the packaging container which concerns on this invention can also perform the process which peels a label from a container using the above-mentioned existing installation which recycles a beer bottle etc. In that case, since no pretreatment is required to peel off the label, no cleaning agent is required, and since the label can be peeled off more easily than in the past, it can be processed in a short time.

The main aspects of the present invention are described below.
1.
(A) a water dispersible polymer having a glass transition temperature of 40 ° C. or lower;
(B) a water-swelled crosslinked starch heat-treated with water at a temperature equal to or higher than the gelatinization start temperature,
Contains an adhesive composition.
2.
(B) The adhesive composition according to 1 above, wherein the water-swelled crosslinked starch is a crosslinked starch crosslinked by phosphoric acid treatment or epoxy treatment.
3.
(A) The adhesive composition according to the above 1 or 2, wherein the water-dispersible polymer is rubber latex.
4).
4. The adhesive composition according to 3 above, wherein the rubber latex has a glass transition temperature (Tg) of −70 ° C. to + 40 ° C.
5.
4. The adhesive composition according to 3 above, wherein the rubber latex is a styrene butadiene rubber (SBR) latex.
6).
(A) The adhesive composition according to 1 or 2 above, wherein the water-dispersible polymer is an acrylic resin emulsion.
7).
7. The adhesive composition according to 6 above, wherein the acrylic resin emulsion has a Tg of −40 ° C. to + 30 ° C.
8).
8. Adhesive composition in any one of said 1-7 used in order to manufacture a packaging container.
9.
The label obtained by apply | coating the adhesive composition in any one of said 1-8.
10.
10. The label according to 9 above, wherein the coating amount of the adhesive composition is 3 to 40 g / m ² .
11.
The packaging container in which the label of said 9-10 is affixed.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples without departing from the gist thereof.

Example 1
After adding 315 g of distilled water at 20 ° C. to a 1 liter flask, 85 g of a cross-linked starch (product name PB5000: gelatinization start temperature 61 ° C., phosphoric acid cross-linking) manufactured by Nissaku Chemical Co., Ltd. was dispersed while stirring. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled as it was, and when the internal temperature reached 50 ° C., 600 g of a styrene / butadiene latex (product name L7430: glass transition temperature Tg = −9 ° C.) manufactured by Asahi Kasei Co., Ltd. was gradually added. Added and mixed uniformly. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 35,000 mPa · s / 30 ° C., a pH of 8.5, and an evaporation residue of 39.8%.

Example 2
After adding 315 g of distilled water at 20 ° C. to a 1 liter flask, 85 g of a cross-linked starch (product name PB5000: gelatinization start temperature 61 ° C., phosphoric acid cross-linking) manufactured by Nissaku Chemical Co., Ltd. was dispersed while stirring. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled as it was, and when the internal temperature reached 50 ° C., 600 g of styrene-butadiene latex (product name Lx426: glass transition temperature Tg = −39 ° C.) manufactured by Zeon Corporation was gradually added. And uniformly mixed. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 43,000 mPa · s / 30 ° C., a pH of 8.6, and an evaporation residue of 35.7%.

Example 3
After adding 215 g of distilled water at 20 ° C. to a 1 liter flask, 85 g of a cross-linked starch (product name PB5000: gelatinization start temperature 61 ° C., phosphoric acid cross-linking) manufactured by Nissaku Chemical Co., Ltd. was dispersed with stirring. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled while continuing stirring, and when the internal temperature reached 50 ° C., 600 g of a styrene / butadiene latex (product name DL620: glass transition temperature Tg = + 11 ° C.) manufactured by Asahi Kasei Co., Ltd. was gradually added. And mixed uniformly. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 11000 mPa · s / 30 ° C., a pH of 6.2, and an evaporation residue of 39.4%.

Example 4
After adding 315 g of distilled water at 20 ° C. to a 1 liter flask, 85 g of a cross-linked starch (product name PB5000: gelatinization start temperature 61 ° C., phosphoric acid cross-linking) manufactured by Nissaku Chemical Co., Ltd. was dispersed while stirring. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled while continuing stirring, and when the internal temperature reached 50 ° C., 550 g of an acrylic resin emulsion (product name Yodosol AD199: glass transition temperature Tg = −14 ° C.) manufactured by Nippon SC Co., Ltd. Slowly added and mixed uniformly. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 39,000 mPa · s / 30 ° C., a pH of 8.6, and an evaporation residue of 42.0%.

Example 5
After adding 315 g of distilled water at 20 ° C. to a 1 liter flask, 85 g of a cross-linked starch (product name PB5000: gelatinization start temperature 61 ° C., phosphoric acid cross-linking) manufactured by Nissaku Chemical Co., Ltd. was dispersed while stirring. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled while continuing stirring, and when the internal temperature reached 50 ° C., 600 g of acrylic resin emulsion (product name Yodosol AD205: glass transition temperature Tg = −39 ° C.) manufactured by NSC Ltd. was added. Slowly added and mixed uniformly. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 20,000 mPa · s / 30 ° C., a pH of 7.8, and an evaporation residue of 38.0%.

Example 6
After adding 200 g of distilled water at 20 ° C. to a 1 liter flask, 85 g of a cross-linked starch (product name PB5000: gelatinization start temperature 61 ° C., phosphoric acid cross-linking) manufactured by Nissho Chemical Co., Ltd. was dispersed with stirring. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled while continuing stirring, and when the internal temperature reached 75 ° C., 650 g of acrylonitrile-butadiene latex (product name Nipol 1571C: glass transition temperature Tg = −10 ° C.) manufactured by Nippon Zeon Co., Ltd. Slowly added and mixed uniformly. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 11500 mPa · s / 30 ° C., a pH of 8.2, and an evaporation residue of 39.4%.

Example 7
After charging 315 g of distilled water at 20 ° C. into a 1 liter flask, 85 g of a cross-linked starch (product name PB2000: gelatinization start temperature 63 ° C., phosphoric acid cross-linking) manufactured by Nissaku Chemical Co., Ltd. was dispersed while stirring. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled as it was, and when the internal temperature reached 50 ° C., 600 g of a styrene / butadiene latex (product name L7430: glass transition temperature Tg = −9 ° C.) manufactured by Asahi Kasei Co., Ltd. was gradually added. Added and mixed uniformly. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 79000 mPa · s / 30 ° C., a pH of 8.4, and an evaporation residue of 38.9%.

Example 8
After adding 315 g of distilled water at 20 ° C. to a 1 liter flask, 85 g of a cross-linked starch (product name Leotac: gelatinization start temperature 64 ° C., glycidyl ether cross-linked) manufactured by Nichi Star Chemical Co., Ltd. was dispersed with stirring. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled as it was, and when the internal temperature reached 50 ° C., 600 g of a styrene / butadiene latex (product name L7430: glass transition temperature Tg = −9 ° C.) manufactured by Asahi Kasei Co., Ltd. was gradually added. Added and mixed uniformly. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 86000 mPa · s / 30 ° C., a pH of 8.5, and an evaporation residue of 38.5%.

Example 9
After adding 240 g of distilled water at 20 ° C. to a 1 liter flask, 60 g of a cross-linked starch (product name PB5000: gelatinization start temperature 61 ° C., phosphoric acid cross-linking) manufactured by Nissho Chemical Co., Ltd. 20 g of hydrophobized starch (product name Milk Whey W) manufactured by company was mixed and dispersed. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled as it was, and when the internal temperature reached 50 ° C., 600 g of a styrene / butadiene latex (product name L7430: glass transition temperature Tg = −9 ° C.) manufactured by Asahi Kasei Co., Ltd. was gradually added. Added and mixed uniformly. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 24,000 mPa · s / 30 ° C., a pH of 8.2, and an evaporation residue of 41.1%.

Comparative Example 1
After adding 315 g of distilled water at 20 ° C. to a 1 liter flask, 85 g of a cross-linked starch (product name PB5000: gelatinization start temperature 61 ° C., phosphoric acid cross-linking) manufactured by Nissaku Chemical Co., Ltd. was dispersed while stirring. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled while continuing stirring, and when the internal temperature reached 50 ° C., 600 g of a styrene-butadiene latex (product name L7708: glass transition temperature Tg = + 49 ° C.) manufactured by Asahi Kasei Co., Ltd. was gradually added. And mixed uniformly. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 13,000 mPa · s / 30 ° C., a pH of 8.7, and an evaporation residue of 38.7%.

Comparative Example 2
After adding 315 g of distilled water at 20 ° C. to a 1 liter flask, 85 g of a cross-linked starch (product name PB5000: gelatinization start temperature 61 ° C., phosphoric acid cross-linking) manufactured by Nissaku Chemical Co., Ltd. was dispersed while stirring. While continuing stirring, the temperature was raised using a water bath until the internal temperature reached 85 ° C., and stirring was continued for 3 hours to obtain a water-swelled pasty starch. This was further cooled as it was, and when the internal temperature reached 50 ° C., 650 g of an acrylic resin emulsion (product name Yodosol AD184: glass transition temperature Tg = + 57 ° C.) manufactured by Nippon SC Co., Ltd. was gradually added. And uniformly mixed. This was further cooled to room temperature to prepare a milky white adhesive composition having a viscosity of 14,000 mPa · s / 30 ° C., a pH of 8.0, and an evaporation residue of 35.9%.

Comparative Example 3
After adding 315 g of distilled water at 20 ° C. to a 1 liter flask, 85 g of a cross-linked starch (product name PB5000: gelatinization start temperature 61 ° C., phosphoric acid cross-linking) manufactured by Nissaku Chemical Co., Ltd. was dispersed while stirring. Further, 600 g of styrene / butadiene latex (product name L7430: glass transition temperature Tg = −9 ° C.) manufactured by Asahi Kasei Co., Ltd. was gradually added and uniformly mixed, and the viscosity was 180 mPa · s / 30 ° C., pH 8.3. A milky white adhesive composition having an evaporation residue of 38.4% was prepared.

Comparative Example 4
After charging 315 g of distilled water at 20 ° C. into a 1 liter flask, 85 g of uncrosslinked starch (product name potato starch: gelatinization start temperature 60 ° C., uncrosslinked) made by Okhotsk Abashiri Agricultural Cooperative was dispersed with stirring. . Further, 600 g of a styrene / butadiene latex (product name L7430: glass transition temperature Tg = −9 ° C.) manufactured by Asahi Kasei Co., Ltd. was gradually added and uniformly mixed, with a viscosity of 29000 mPa · s / 30 ° C., pH 8.1. A milky white adhesive composition having an evaporation residue of 37.6% was prepared.

About the adhesive composition of Examples 1-9 and Comparative Examples 1-4, it tested about various performances. The operation and evaluation of the test are shown below.
Viscosity Each adhesive composition was immersed in a 30 ° C. warm bath, and after confirming that the content reached 30 ° C., the viscosity of the adhesive composition at 20 rpm was measured using a BH viscometer.
pH
The pH of each adhesive composition was measured using a pH meter.
Evaporation residue About 1 g of each adhesive composition was placed on an aluminum dish, precisely weighed, placed in a 105 ° C. incubator and dried for 3 hours. After precisely weighing the weight of the adhesive composition after drying, the evaporation residue N.I. V. Was calculated.

Evaporation residue N.E. V. (%)
= {Adhesive composition weight after drying (g) / Adhesive weight before drying (g)} × 100

Mechanical Suitability Each adhesive composition was coated on high-quality paper using a small simple roll coating tester (manufactured by MEC Co., Ltd.). At this time, there was no dripping of the adhesive composition from the roll and the coating amount of the adhesive composition could be controlled to 10 to 30 g / m ² ◯, dripping occurred, or the coating amount was 10 to 30 g / m ^2. Those that could not be controlled to m ² were evaluated as x. ○ is a pass and × is a failure.

Easy peelability Each adhesive composition was applied to a surface of a high quality paper cut to a width of 25 mm and a length of 15 cm with a bar coater so that the coating amount was 10 to ²⁰ g / m ² . It crimped | bonded to the glass bottle bottle (Toyo Glass FTB600HC) by hand. These were cured for 7 days in a high-temperature room at 23 ° C. and 60% RH. These test pieces were measured for tensile strength when peeled in the direction of about 90 ° at a tensile speed of 50 mm / min using a tensile tester, and judged based on the following criteria.

Judgment criteria: A: peel strength is 1-5 N / 25 mm, and there is no paper breakage
○, peel strength is 1-5N / 25mm,
Paper breakage is less than 30% of the bonding area
Δ, peel strength is greater than 5N / 25mm,
Paper breakage is less than 30% of the bonding area
X indicates that the paper breakage is greater than 30% of the adhesion area
XX indicates that the peel strength is smaller than <1 N / 25 mm. ◎, ○, Δ are acceptable, and XX, xx are unacceptable.
Note that the peel strength of 1 to 5 N / 25 mm described in this criterion is that the label is easily separated from the packaging container without any special treatment, and the label and the container are separated. This is an appropriate peel strength.

Low temperature storage stability Each adhesive was sealed in a glass bottle and left in a constant temperature room at 5 ° C. for 3 months. After 3 months, the viscosity of each adhesive composition was measured at 30 ° C. in the same manner as described above for viscosity measurement. The ratio to the viscosity measured in the same manner immediately after the preparation (hereinafter referred to as “thickening rate%”) was calculated using the following formula. A sample having a viscosity increase rate of 150% or less was evaluated as ○, and a sample having a viscosity increase rate of 150% or more was evaluated as ×. Moreover, it was set as xx that the viscosity increase rate is 150% or less, and 2 or more layers separation | separation is recognized by the external appearance in an adhesive agent.

Thickening rate (%)
= {Viscosity after 3 months (mPa · s) / viscosity immediately after preparation (mPa · s)} × 100
○ is acceptable, and x and xx are unacceptable.

As shown in Table 1, the adhesive composition according to the present invention has an excellent balance of mechanical suitability, easy peelability and low-temperature storage stability, and is suitable as an adhesive composition to be applied to a label attached to a glass bottle. is there.
The adhesive compositions of Comparative Examples 1 and 2 have remarkably low peelability. This is considered due to the fact that the glass transition temperature of the water-dispersed polymer contained in the adhesive composition is higher than 40 ° C.
In the adhesive composition of Comparative Example 3, all evaluation items such as mechanical suitability, easy peelability, and low-temperature storage stability are unacceptable. Although the comparative example 3 uses the crosslinked starch (PB5000: gelatinization start temperature 61 degreeC) contained in the adhesive agent of Examples 1-6, since this crosslinked starch was mix | blended without heat processing, its performance is low. It is thought that an adhesive composition was obtained.
Since the adhesive composition of Comparative Example 4 contains not cross-linked starch but non-cross-linked starch, it is considered that the easily peelable and low-temperature storage stability are poor.

  Thus, (A) the water-swelled crosslinked starch heat-treated with water at a temperature equal to or higher than the gelatinization start temperature, and (B) an aqueous dispersion polymer having a glass transition temperature of 40 ° C. or lower. Has improved mechanical suitability, easy peelability, and low-temperature storage stability, and has been shown to be suitable as an adhesive composition used for attaching labels to containers.

Claims (3)

(A) a water dispersible polymer having a glass transition temperature of 40 ° C. or lower;
(B) a water-swelled crosslinked starch heat-treated with water at a temperature equal to or higher than the gelatinization start temperature,
Contains an adhesive composition.   A label obtained by applying the adhesive composition according to claim 1.   A packaging container to which the label according to claim 2 is attached.