JP2000178515A - Adherent sheet and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an adherent label to easily detach without leaving paste only when heating treatment is carried out under a specified condition by setting an acrylic adhesive layer reactive with a crosslinking agent on the surface base comprising a film having a specified thermal shrinkage. SOLUTION: This adherent sheet is obtained by applying an acrylic adhesive reactive with a crosslinking agent comprising an acrylic resin and a crosslinking agent and by applying the adhesive having the supporting strength (at 70 deg.C) of 2 hr or more obtained by optionally adding additives such as a tackifier, an ultraviolet absorbent, a crosslinking agent, a pigment, an antioxidant and the like with the adhesive strength (JIS-Z-0237) of 150-700 N/m, on the surface of a film wherein the surface base has not less than 40% of a thermal shrinkage in at least one direction at 70-120 deg.C, preferably at 70-100 deg.C, and not more than 20% of the thermal shrinkage in both direction at not more than 65 deg.C, so that the adhesive is 3-50 g/m2, followed by drying the applied film. The adhesive sheets is stuck on a plastic or glass vessel, heated at not less than 70 deg.C, preferably at 70-120 deg.C, and then collected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pressure-sensitive adhesive sheet,
The present invention relates to an adhesive sheet suitable as an adhesive label to be attached to a container such as a plastic container and a glass container.

[0002]

2. Description of the Related Art In order to collect and recycle containers such as plastic containers, it is necessary to peel off a label attached to the container. For this reason, conventionally, an adhesive label using a water-soluble or alkali-soluble adhesive is used for the adhesive layer, and water, hot water, an alkaline solution, or the like is used as a cleaning liquid in the recycling process, or water, hot water or alkali is used. A method has been adopted in which the adhesive force is reduced in a solution to peel off.

[0003] In such a method, when the surface substrate is paper, there is a gap between the paper and the container, and water penetrates into the paper layer, so that the separation is easy. Since it adheres tightly to the plastic container and the base material does not permeate water, water, warm water or an alkaline aqueous solution permeates the pressure-sensitive adhesive layer, and it takes a long time to peel off, resulting in poor work efficiency. For this reason, for example, it has been proposed that the label be quickly peeled off by partially providing an adhesive layer for immediate infiltration between the label base material and the surface of the container (Japanese Utility Model Laid-Open No. 2-107179). ing.

However, in the case of a water-soluble pressure-sensitive adhesive label, when the label surface is wet with water or the like, the label is easily displaced or easily peeled off from a container. Particularly, a beverage bottle is sometimes cooled in a refrigerator or ice water. It is not suitable for the pressure-sensitive adhesive label for bottles. Further, as a method for peeling the label in this way, a method of immersion in a solution is employed, but a large amount of water is consumed in these methods, and a neutralization treatment is performed when an alkaline aqueous solution is used. However, there are drawbacks such as the necessity of disposal after the purification treatment, which has an adverse effect on the environment and high costs for collecting plastic containers.

On the other hand, there has been proposed a label using a plastic tic film having a large heat shrinkability and capable of easily peeling off the label by heating (Japanese Utility Model Application Laid-Open No. 63-63).
No. 138584, Japanese Utility Model Laid-Open No. 5-22337). However, the adhesive label may be turned up or peeled off at a temperature lower than the heat treatment conditions at the time of recovery, before being recovered by heat treatment. An adhesive label that has been rolled up or peeled off
It adheres to a container, a collection case, or the like, and causes poor workability at the time of collection, or causes deterioration of a plastic container depending on heat treatment conditions. Alternatively, the base material may shrink when the adhesive is processed into a plastic film that shrinks by heat. In addition, depending on the type of adhesive provided on the back of the plastic film, only the plastic film shrinks, the adhesive remains in the container,
That is, the adhesive residue phenomenon may occur.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks and has no problem in ordinary handling.
An object of the present invention is to provide a pressure-sensitive adhesive sheet characterized in that a pressure-sensitive adhesive label can be easily peeled off only by heat treatment under specific conditions without leaving adhesive.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that it can be achieved only by combining a specific film and a specific adhesive.

The present invention is directed to a pressure-sensitive adhesive sheet having a surface substrate and a pressure-sensitive adhesive layer, wherein the surface substrate has a heat shrinkage of at least one direction at 70 to 120 ° C. in at least one direction of 40% or more and 65 ° C. or less in both directions. A film having a shrinkage of 20% or less,
In addition, the pressure-sensitive adhesive sheet is characterized in that the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is a cross-linking agent reactive acrylic pressure-sensitive adhesive.

When the pressure-sensitive adhesive layer is applied to the surface of the container in accordance with JIS Z
It is preferable that the adhesive force according to 0237 is 150 to 700 N / m. Further, it is preferable to use an adhesive having a holding power at 70 ° C. of 2 hours or more. Preferably, the surface substrate is a polyester film. It is preferable that the container is made of polyethylene terephthalate (PET), which has a relatively high heat-resistant temperature and is hardly deteriorated.

Further, after a cross-linking agent-reactive acrylic pressure-sensitive adhesive is applied to the surface of the release agent layer of the release sheet and dried, the surface of the pressure-sensitive adhesive layer is cooled to 70 to 70 ° C.
A method for producing a pressure-sensitive adhesive sheet, comprising laminating films having a heat shrinkage in at least one direction at 120 ° C. of 40% or more and a heat shrinkage in both directions at 65 ° C. or less of 20% or less. It is more preferable that the films are laminated in a state where the surface of the pressure-sensitive adhesive layer is 65 ° C. or lower.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION According to the present invention, the surface
Heat shrinkage in at least one direction at 0 ° C. is 40% or more;
The pressure-sensitive adhesive sheet is a film having a heat shrinkage of not more than 20% in both directions at 5 ° C. or less, and the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is a cross-linking reaction type acrylic pressure-sensitive adhesive. For example, it is affixed as a label to a plastic container or a glass container,
When collecting containers and the like, 70 ° C. or higher, preferably 70 to
By performing the heat treatment at 120 ° C., more preferably 70 to 100 ° C., the adhesive label can be easily peeled off without leaving adhesive.

The surface substrate used in the present invention is 70 to 12
A film having a heat shrinkage in at least one direction at 0 ° C., preferably 70 to 100 ° C. of at least 40% and a heat shrinkage in both directions at 65 ° C. or less of 20% or less is used. By the way, when the heat shrinkage in both directions at 70 to 120 ° C. is less than 40%, the label is difficult to peel off easily and is not suitable for recycling. If at least one of the thermal shrinkage ratios at 65 ° C. or lower exceeds 20%, the heat is turned up or peeled off by the heat other than in the recovery step. In addition, 120 ° C
The heat shrinkage ratio under the condition exceeding 12 is not particularly limited.
If the temperature exceeds 0 ° C., the cohesive force of the pressure-sensitive adhesive of the pressure-sensitive adhesive sheet may be too low, and the adhesive may remain in the container, the plastic container may be deteriorated, or the heat capacity may be high and the economical efficiency may be deteriorated. In the recovery step, it is preferable to heat at 70 to 120C, preferably 70 to 100C. The heat shrinkage of the film referred to in the present invention is determined by setting a film having a length of 100 mm × 100 mm in the vertical direction × horizontal direction with a hot air circulation dryer so that the film surface temperature becomes each temperature, and Take the value in the higher direction among the shrinkage ratios.

The film having such a heat shrinkage may be selected from films of polyester type, polyolefin type, polyvinyl chloride (PVC) type and the like. It is preferable to use a polyester film (for example, polyethylene terephthalate) which does not easily shrink.

In the present invention, a cross-linking agent-reactive acrylic pressure-sensitive adhesive (two-component cross-linking pressure-sensitive adhesive) is used as the pressure-sensitive adhesive. In the case of other pressure-sensitive adhesives, peeling of the pressure-sensitive adhesive label due to heating is insufficient, and adhesive residue easily occurs in the container at the time of peeling. The cross-linking agent-reactive acrylic pressure-sensitive adhesive contains an acrylic resin and a cross-linking agent, and is optionally blended with additives such as tackifiers, ultraviolet absorbers, cross-linking agents, pigments, plasticizers, anti-aging agents, etc. You.

As the acrylic resin, for example, ethyl acrylate (EA), butyl acrylate (BA), 2-ethylhexyl acrylate (2-
EHA), vinyl acetate (VAc), acrylonitrile (AN), styrene (St), methyl methacrylate (MMA), butyl methacrylate (BM) as comonomer
A), methyl acrylate (MA), methacrylic acid (MAA), acrylic acid (A
A), from itaconic acid (IA), hydroxypropyl methacrylate (HPMA), dimethylaminoethyl methacrylate (DM), acrylamide (AM), methylol acrylamide (N-MAN), glycidyl methacrylate (GMA), maleic anhydride, etc. The main component (preferably 80% by weight or more) of the resulting copolymer is a polyisocyanate;
A crosslinked acrylic pressure-sensitive adhesive reacted with a melamine resin, a urea resin, an epoxy resin, a metal chelate or the like is preferable. Further, among the above crosslinking agents, a polyisocyanate-based crosslinking agent having good reactivity with an acid or an acid anhydride group, a hydroxyl group, an amide group and the like and having an appropriate reaction progress is particularly preferred.

Among the above-mentioned pressure-sensitive adhesives, J
Adhesive strength according to IS Z 0237 is 150 to 700 N /
m is preferable. By the way, if the adhesive force to the surface of the container is less than 150 N / m, the adhesive label is easily peeled off from the container before the step of peeling and recovering the adhesive label by heat treatment, which is not preferable.
/ M is not preferable because the adhesive label may not be easily peeled off from the container or the adhesive may remain when the adhesive label is peeled and collected by heat treatment.

Further, among the pressure-sensitive adhesives, it is preferable that the holding power at 70 ° C. is 2 hours or more. Here, the holding force means a 40 μm OPP film (made by Oji Paper, PU-
112), a predetermined amount of an adhesive is applied to one surface, the adhesive surface is applied on a stainless steel plate, and the adhesive label is applied so that the area becomes 25 mm × 25 mm. It is obtained by measuring the time until the pressure-sensitive adhesive label falls when a load of 1 kg weight is applied in an atmosphere of ° C. In this measurement, it is preferable that the holding force at 70 ° C. does not drop for 2 hours or more. By the way, the heat treatment is applied to the plastic container to which the pressure-sensitive adhesive label using the pressure-sensitive adhesive that falls in less than 2 hours is applied, and the pressure-sensitive adhesive may remain in the container when the pressure-sensitive adhesive label is peeled off, which is not preferable. . If the time exceeds 48 hours, the cohesive force of the pressure-sensitive adhesive is too high and the adhesive may remain without following the shrinkage of the film. Therefore, the holding force is preferably 2 to 48 hours.

The amount of the pressure-sensitive adhesive layer to be applied is selected appropriately according to the thickness of the surface substrate to be used.
Preferably of about to 50 g / m ^2, more preferably that of 5 to 30 g / m ^2. By the way, the application amount is 3
If it is less than g / m ^2, the adhesive strength when sticking the pressure-sensitive adhesive sheet to the container may be reduced, and if it exceeds 50 g / m ² , the anchoring property of the pressure-sensitive adhesive becomes poor, and the pressure-sensitive adhesive becomes Problems may occur, such as oozing out or glue residue on the container. Note that the adhesive may be partially applied so as to be more easily peeled off.

As the coating method, a known method can be adopted and is not particularly limited. For example, a comma coating method, a reverse coating method, a gravure coating method, a reverse gravure method, a kiss coating method, a knife coating method, a bar coating method Method, a die coating method, a curtain coating method, and a transfer method of transferring a product coated on a process paper by these methods.

Since the heat-shrinkable film is used for the surface substrate of the pressure-sensitive adhesive sheet of the present invention, it is not preferable to perform pressure-sensitive adhesive processing at a high temperature, and it is necessary to control the drying temperature and the like.
In particular, a method of applying an adhesive to a release sheet, drying it, and then bonding a surface substrate, or applying an adhesive to process paper, drying it, bonding it to the surface substrate, and then peeling off the process paper The method of forming the pressure-sensitive adhesive layer is preferable because the influence of heat is small and the processing is easy. Further, it is particularly preferable that the pressure-sensitive adhesive layer is laminated in a state where the temperature of the surface of the pressure-sensitive adhesive layer at the time of bonding the surface base material is lower than 70 ° C. Particularly preferred is a method in which a pressure-sensitive adhesive is applied to a release sheet for formation.

The release sheet and process paper are not particularly limited, but a known release sheet in which a release agent layer such as silicone is formed on paper, glassine paper, laminated paper, plastic film or the like can be used. Above all, in order to maintain the transparency and glossiness of the adhesive sheet, those having high smoothness are preferable so as not to leave a glue mark on the adhesive surface when peeling the adhesive sheet from the release sheet, for example, a release sheet laminated with polyethylene, a plastic film A release sheet using is preferably used.

The pressure-sensitive adhesive sheet of the present invention may have a structure in which a release agent layer is provided on the surface opposite to the pressure-sensitive adhesive layer without using a release sheet. In this case, it is preferable to form a release agent layer after printing, and then to form an adhesive layer. In addition,
In this case, the release agent layer is preferably formed by low-temperature processing or ultraviolet curing.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following examples, which, of course, are not intended to limit the present invention. In the Examples and Comparative Examples, “parts” and “%” indicate “parts by weight” and “% by weight” unless otherwise specified.

Example 1 (Adhesive preparation) 85 parts by weight of butyl acrylate, 10 parts by weight of butyl methacrylate, and 5 parts by weight of acrylic acid
Solution polymerization was carried out in ethyl acetate using 1 part by weight of benzoyl peroxide as an initiator to obtain a pressure-sensitive adhesive main component having a solid content of 40% by weight. A pressure-sensitive adhesive was prepared by adding 2 parts by weight of a crosslinking agent (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) to the main adhesive.

(Production of pressure-sensitive adhesive sheet)
5 μm polyester film (Toyobo Co., Ltd.
S5630, heat shrinkage at 70 ° C .: 50%, heat shrinkage at 65 ° C .: 1.2%). Release sheet laminated with polyethylene (Oji Paper Co., Ltd., fine quality OK
On the release agent layer of C), the above-mentioned pressure-sensitive adhesive was solidified at a solid content of 20 g / m ^2.
After coating and drying so as to obtain a pressure-sensitive adhesive sheet, the pressure-sensitive adhesive sheet was bonded to a surface substrate in a state where the surface temperature of the pressure-sensitive adhesive layer was lower than 70 ° C.

(Evaluation) "Holding force of pressure-sensitive adhesive"
One side of a film (manufactured by Oji Paper Co., Ltd., PU-112) is coated with an adhesive at a solid content of 20 g / m ^2, and the adhesive surface is attached to a stainless steel plate so that the adhesive sheet has an area of 25 mm × 25 mm. After sticking and reciprocating once with a 2 kg pressure roll, the time required for the pressure-sensitive adhesive sheet to fall when a load of 1 kg was applied in an atmosphere at 70 ° C. was measured, and it did not fall for 2 hours.

(Suitability for Recycling) The obtained pressure-sensitive adhesive sheet was cut into a size of 50 mm × 100 mm to form a pressure-sensitive adhesive label. Plastic container (polyethylene terephthalate (PET) container for 2.7 liters, Toyo Seikan Co., Ltd.)
) Was pressed and reciprocated one time with a 2 kg pressure roll. The container surface temperature when placed in a hot air circulation type dryer at 80 ° C. for 60 seconds was 71 ° C. When the degree of peeling of the pressure-sensitive adhesive label at this time was evaluated, the pressure-sensitive adhesive label was easily peeled off without leaving adhesive on the plastic container. The container surface temperature was 83 ° C. when placed in a hot-air circulation dryer at 100 ° C. for 60 seconds. When the degree of peeling of the pressure-sensitive adhesive label at this time was evaluated, the pressure-sensitive adhesive label was easily peeled off without leaving adhesive on the plastic container. The container was placed in a hot-air circulating drier at 70 ° C. for 60 seconds under heating conditions. As a result, the container surface temperature was 65 ° C., and it was not easy to remove the adhesive label from the container. In addition, when the heating conditions were placed in a hot air circulation type dryer at 180 ° C. for 60 seconds, the container surface temperature was 130 ° C.,
Although easily peeled from the container, a part of the adhesive remained in the plastic container and became sticky to the touch. Further, even when the adhesive label was left in an environment of 65 ° C., no curling or peeling of the adhesive label was observed.

Example 2 40 μm PVC film as substrate (HR, manufactured by Shin-Etsu Chemical Co., Ltd., heat shrinkage at 70 ° C .: 40%, 65 ° C.)
The same pressure-sensitive adhesive sheet as in Example 1 was obtained except that the heat shrinkage in the above was 15%.

(Evaluation) The recyclability was evaluated in the same manner as in Example 1. The container surface temperature when placed in a hot air circulation type dryer at 80 ° C. for 60 seconds was 71 ° C. When the degree of peeling of the pressure-sensitive adhesive label at this time was evaluated, the pressure-sensitive adhesive label was easily peeled off without leaving adhesive on the plastic container. When the pressure-sensitive adhesive label was left in an environment at 65 ° C., the pressure-sensitive adhesive label slightly shrunk, but no curling or peeling of the pressure-sensitive adhesive label was observed.

Example 3 (Adhesive preparation) 2-ethylhexyl acrylate 70
Parts by weight, 15 parts by weight of butyl acrylate, 10 parts by weight of butyl methacrylate, and 5 parts by weight of acrylic acid are solution-polymerized in ethyl acetate using 1 part by weight of benzoyl peroxide as an initiator, and the solid concentration is 40% by weight. Was obtained. A pressure-sensitive adhesive was prepared by adding 2 parts by weight of a crosslinking agent (Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.) to this pressure-sensitive adhesive base material. (Production of pressure-sensitive adhesive sheet) A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the above-mentioned pressure-sensitive adhesive was used.

(Evaluation) When the holding power of the pressure-sensitive adhesive was measured in the same manner as in Example 1, the holding power at 70 ° C. did not fall for 2 hours. The recyclability was evaluated in the same manner as in Example 1. The container surface temperature when placed in a hot air circulation type dryer at 80 ° C. for 60 seconds was 71 ° C. When the degree of peeling of the pressure-sensitive adhesive label at this time was evaluated, the pressure-sensitive adhesive label was easily peeled off without leaving adhesive on the plastic container. Further, even when the adhesive label was left in an environment of 65 ° C., no curling or peeling of the adhesive label was observed.

Comparative Example 1 Adhesion was carried out in the same manner as in Example 1 except that a 40 μm PVC film (BYC, heat shrinkage at 70 ° C .: 20%, unidirectional) of 40 μm was used as a surface substrate. I got a sheet. (Evaluation) The recyclability was evaluated in the same manner as in Example 1. The container surface temperature when placed in a hot air circulation type dryer at 80 ° C. for 60 seconds was 71 ° C. When the degree of peeling of the adhesive label at this time was evaluated, it was not easily peeled from the plastic container.

Comparative Example 2 40 μm PVC film (Shin-Etsu Chemical Co., Ltd., TR, heat shrinkage at 70 ° C .: 48%, 6)
A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the heat shrinkage at 5 ° C .: 35%) was used. (Evaluation) The recyclability was evaluated in the same manner as in Example 1. The container surface temperature when placed in a hot air circulation type dryer at 80 ° C. for 60 seconds was 71 ° C. When the degree of peeling of the adhesive label at this time was evaluated, it was easily peeled off from the plastic container. However, when the plastic to which the adhesive label was attached was placed in an environment of 65 ° C., both ends of the adhesive label were turned up.

As is apparent from the above Examples and Comparative Examples, in each Example, the adhesive label was easily peeled off without leaving adhesive on the plastic container, and the adhesive label was not adhered at a temperature lower than the heat treatment conditions for collecting the plastic container. The label was not turned or peeled off. That is, the adhesive label does not peel off before the container is collected, and the container can be collected by the heat treatment, which is the object of the present invention.

Comparative Example 1 shrank to some extent due to the heat treatment, but did not easily come off. In Comparative Example 2, the adhesive label was easily peeled off by the heat treatment, but it was rolled up from the plastic container before being collected and heat-treated. It can be difficult.

[0036]

The pressure-sensitive adhesive sheet of the present invention can be easily peeled off by heat treatment after it is applied to a container, and thus is suitable for recycling the container. Also, the adhesive sheet is an excellent adhesive sheet in which the adhesive label is not turned up or peeled off at a temperature lower than the heat treatment conditions at the time of the collection, and the adhesive does not remain in the container.

Claims (4)

[Claims] 1. A pressure-sensitive adhesive sheet having a surface substrate and a pressure-sensitive adhesive layer, wherein the surface substrate has a heat shrinkage in at least one direction at 70 to 120 ° C. of at least 40% and a heat shrinkage of both directions at 65 ° C. or less. Is a film of 20% or less, and the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is a crosslinker-reactive acrylic pressure-sensitive adhesive. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a pressure-sensitive adhesive strength according to JIS Z 0237 of 150 to 700 N / m. 3. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive having a holding power at 70 ° C. of 2 hours or more. 4. A cross-linking agent-reactive acrylic pressure-sensitive adhesive is applied to the surface of the pressure-sensitive adhesive layer of the release sheet, and the pressure-sensitive adhesive layer is dried at 70 ° C.
The heat shrinkage in at least one direction at 40 ° C. is 40% or more,
A method for producing a pressure-sensitive adhesive sheet, comprising laminating films having a heat shrinkage in both directions at 20 ° C. or less of 20% or less.