Label, especially for a reusable container

Abstract

A proposal is made for a label (1) which can be adhered to an article (5), more particularly to a beverage bottle, and can be detached again in a washing liquid at a washing temperature of at least 50? C., in the form of a laminate at least with the following layers: a biaxially stretched polymeric film layer (9) which shrinks at the washing temperature, a printed decoration layer (11), and an adhesive layer (13), more particularly a pressure-sensitive adhesive layer, for adhering the label (1) to the article (5). The polymeric film layer (9) is designed in such a way that in the laminate at the washing temperature within a maximum time span of less than 5 minutes, in particular less than 3 minutes, it attains degrees of contraction in its two stretching directions which differ from one another by less than 50% and are lower than 50%. As a result of this, whereas the adhesive force between the label (1) and the article (5) is high, the label (1) can be washed off from the article (5) without splitting.

Claims

1. A label adapted to be adhered to an article and adapted to be detached in a washing liquid at a mandated washing temperature from a temperature range between 50? C. and 95? C., the label being in the form of a laminate comprising at least the following layers: a polymeric film layer being biaxially stretched in two stretching directions and being adapted to recontract in the two stretching directions at the mandated washing temperature, a printed decoration layer, and an adhesive layer for adhering the label to the article, wherein the polymeric film layer is designed such that the laminate, at the mandated washing temperature and within a maximum time span of less than 5 minutes and with the polymeric film layer being allowed to freely contract in the two stretching directions, achieves maximum degrees of contraction in the two stretching directions which are equal or achieves maximum degrees of contraction in the two stretching directions which are different from each other with a lower maximum degree of contraction differing by less than 50% from a higher maximum degree of contraction, wherein the stretched polymeric film layer is designed in such a way that the laminate, in the two stretching directions of the polymeric film layer, when subjected to a washing temperature of 80? C. and within the maximum time span, attains a contraction tension of maximally 18 N/mm.sup.2, and when subjected to a washing temperature of 60? C. and within the maximum time span, attains a contraction tension of maximally 3.5 N/mm.sup.2.

2. The label of claim 1, wherein the polymeric film layer is designed such that the laminate, at the mandated washing temperature and within the maximum time span and on free contraction in the two stretching directions of the polymeric film layer, achieves maximum degrees of contraction which are lower than 65%.

3. The label of claim 2, wherein the polymeric film layer is designed such that the laminate achieves in the two stretching directions maximum degrees of contraction of less than 50%.

4. The label of claim 1, wherein the maximum time span is less than 3 minutes.

5. The label of claim 1, wherein said adhesive layer is a pressure-sensitive adhesive layer.

6. The label of claim 1, wherein said article is a beverage bottle.

7. The label of claim 1, wherein the stretched polymeric film layer is designed in such a way that the laminate, in the two stretching directions of the polymeric film layer and within the maximum time span, a) when subjected to a washing temperature of 60? C. does not exceed a contraction tension of maximally 3.5 N/mm.sup.2 and a degree of contraction of maximally 20%, and/or b) when subjected to a washing temperature of 70? C. does not exceed a contraction tension of maximally 15 N/mm.sup.2 and a degree of contraction of maximally 55%, and/or c) when subjected to a washing temperature of 80? C. does not exceed a contraction tension of maximally 18 N/mm.sup.2 and a degree of contraction of maximally 60%, and/or d) when subjected to a washing temperature of 90? C. does not exceed a contraction tension of maximally 20 N/mm.sup.2 and a degree of contraction of maximally 65%.

8. The label of claim 7, wherein the stretched polymeric film layer is designed in such a way that the laminate, in the two stretching directions of the polymeric film layer and within the maximum time span, a) when subjected to a washing temperature of 60? C. does not exceed a contraction tension of maximally 3.5 N/mm.sup.2 and a degree of contraction of maximally 13%, and/or b) when subjected to a washing temperature of 70? C. does not exceed a contraction tension of maximally 12 N/mm.sup.2 and a degree of contraction of maximally 36%, and/or c) when subjected to a washing temperature of 80? C. does not exceed a contraction tension of maximally 18 N/mm.sup.2 and a degree of contraction of maximally 46%, and/or d) when subjected to a washing temperature of 90? C. does not exceed a contraction tension of maximally 20 N/mm.sup.2 and a degree of contraction of maximally 50%.

9. The label of claim 1, wherein the stretched polymeric film layer is formed of a plastics material based on polyethylene terephthalate (PET) or polyester or polyvinyl chloride (PVC) or polystyrene (PS) or polypropylene (PP) or polyethylene (PE) or polylactic acid (PLA) or cycloolefin copolymer (COC).

10. The label of claim 9, wherein the stretched polymeric film layer has an elasticity modulus of at least 2500 MPa.

11. The label of claim 10, wherein the adhesive layer comprises as its base substance an adhesive which is adapted to be excited to crosslinking by radiation.

12. The label of claim 11, wherein said radiation is ultraviolet light.

13. The label of claim 1, wherein the stretched polymeric film layer is a layer constituent of a film composite layer in the form of a laminate composite layer or a coextruded composite layer, wherein the film composite layer comprises at least one further polymeric film layer in the form of a monoaxially or biaxially stretched polymeric film layer which contracts on exposure to heat.

14. The label of claim 1, wherein the adhesive layer is formed of a crosslinking polymer, and is joined via an interlayer of crosslinking laminating adhesive to one layer of the laminate other than said adhesive layer.

15. The label of claim 14, wherein the interlayer comprises two-component polyurethane adhesive as its base substance.

16. The label of claim 1, wherein the stretched polymeric film layer is composed of transparent plastics material, and the printed decoration layer is disposed between the stretched polymeric film layer and the adhesive layer.

17. The label of claim 1, wherein the decoration layer and the adhesive layer are disposed on opposite sides of the stretched polymeric film layer, and the decoration layer is disposed between the stretched polymeric film layer and a protective layer.

18. The label of claim 17, wherein the protective layer is designed as a protective layer or as a polymeric film layer.

19. The label of claim 18, wherein the protective layer is a monoaxially or biaxially stretched, polymeric film layer which is adapted to contract on exposure to heat.

20. A container in the form of a beverage bottle, wherein a label of claim 1 is adhered to the container.

21. A method of adhering a label to an article and detaching the label from the article, wherein the label is adapted to be adhered to the article and is in the form of a laminate with at least the following layers: a polymeric film layer being biaxially stretched in two stretching directions and being adapted to recontract in the two stretching directions when exposed to heat, a printed decoration layer, and an adhesive layer for adhering to the article, wherein the label is adhered by its adhesive layer to the article, and wherein said label can be treated for the purpose of detachment of the label, with a washing liquid which has a mandated washing temperature in the range between 50? C. and 95? C., such that the polymeric film layer recontracts and, in so doing, overcomes the adhesive force of the adhesive layer, wherein the polymeric film layer is designed such that the laminate, at the mandated washing temperature and within a maximum time span of less than 5 minutes and with the polymeric film layer being allowed to freely contract in the two stretching directions achieves maximum degrees of contraction in the two stretching directions which are lower than 65%, and achieves a maximum degree of contraction in a first one of the two stretching directions which is less than 50% of the maximum degree of contraction in a second one of the two stretching directions, wherein the polymeric film layer is designed in such a way that the laminate, in the two stretching directions, at the mandated washing temperature and within the maximum time span, attains a contraction tension of at least 0.6 N/mm.sup.2 and a degree of contraction of at least 0.5%, wherein when subjected to a washing temperature of 60? C. and within the maximum time span, attains a contraction tension of maximally 3.5 N/mm.sup.2.

22. The method of claim 21, wherein the polymeric film layer is designed in such a way that the laminate, in the two stretching directions of the polymeric film layer and within the maximum time span, a) when subjected to a washing temperature of 60? C. does not exceed a contraction tension of maximally 3.5 N/mm.sup.2 and a degree of contraction of maximally 20%, and/or b) when subjected to a washing temperature of 70? C. does not exceed a contraction tension of maximally 15 N/mm.sup.2, more particularly of maximally 12 N/mm2, and a degree of contraction of maximally 55%, and/or c) when subjected to a washing temperature of 80? C. does not exceed a contraction tension of maximally 18 N/mm.sup.2 and a degree of contraction of maximally 60%, and/or d) when subjected to a washing temperature of 90? C. does not exceed a contraction tension of maximally 20 N/mm.sup.2 and a degree of contraction of maximally 65%.

23. The method according to claim 21, wherein the stretched polymeric film layer is designed in such a way that the laminate, in the two stretching directions of the polymeric film layer and within the maximum time span, at a washing temperature of at least 70? C. exceeds a contraction tension of at least 1.5 N/mm2 and a degree of contraction of at least 4%.

24. The method according to claim 21, wherein the stretched polymeric film layer is designed in such a way that the laminate, in the two stretching directions of the polymeric film layer and within the maximum time span, a) when subjected to a washing temperature of at least 70? C. exceeds a contraction tension of at least 1.5 N/mm.sup.2 and a degree of contraction of at least 4%, and/or b) when subjected to a washing temperature of at least 80? C. exceeds a contraction tension of at least 0.8 N/mm.sup.2 and a degree of contraction of at least 2%.

Description

(1) Below, exemplary embodiments of the invention are explained in more detail with reference to a drawing. In that drawing

(2) FIG. 1 shows a container with a label in accordance with the invention adhered to its outer periphery at the beginning of detachment in a washing liquid;

(3) FIG. 2 shows a section through the container and the label, viewed along a line II-II in FIG. 1;

(4) FIG. 3 shows a sectional view through a variant of the label from FIG. 1, at the beginning of detachment; and

(5) FIG. 4 shows a further variant of the label from FIG. 1, at the beginning of detachment.

(6) FIGS. 1 and 2 show a label, designated generally by 1, which is adhered to a substantially cylindrical outer surface 3 of a container 5, as for example of a multi-use beverage bottle, in a condition in which the label 1 is beginning to detach, almost simultaneously from all four edges 7, in a hot washing liquid (not shown). In the condition before the detachment of the label 1, it is adhered up to the edges 7 to the surface 3 of the container 5.

(7) The label 1 is designed as a laminate and has a biaxially stretched polymeric film layer 9 which shrinks, i.e., contracts, in both stretching directions at the washing temperature of the washing liquid of, for example, about 80? C. The layer 9 is composed of transparent plastics material and bears, on its side facing the container 5, a printed decoration layer 11, which is visible from the outside through the polymeric film layer 9. Applied to the decoration layer 11 is an adhesive layer 13 composed of a pressure-sensitive adhesive material, which bonds the label 1 to the container 5.

(8) The polymeric film layer 9 is preferably composed of a polyethylene terephthalate (PET) plastics material which is biaxially stretched and which in both of its stretching directions has maximum degrees of contraction which differ, when the polymeric film material is heated in the washing liquid, while allowing free contraction of the laminate, by less than 50% (based on the higher degree of contraction). The degree of contraction in each of the two stretching directions is less than 65%, more particularly less than 50% (based on the stretched original condition). The polymeric film layer 9 is configured such that the stated values are achieved within a washing time span of approximately 5 minutes, advantageously of about 3 minutes, which is customary for reusable containers in industrial washing installations.

(9) Since the build-up in contraction tension is distributed on both stretching directions of the polymeric film layer 9 over the entire washing time span, and since the contractions which develop approximately uniformly in both stretching directions are restricted, the generation of stresses by the contraction process that may lead to splitting of the detaching label into a detaching part and a remnant part remaining on the container is prevented. Because the detachment procedure takes place in a controlled way in both stretching directions, labels can be detached without splitting even when the adhesive layer 13 is designed for comparatively high adhesion forces, in order to prevent unwanted detachment of the label 1 from bottles having different surface properties.

(10) The contraction parameters of the polymeric film layer 9 are set such that the laminate in the two stretching directions of the polymeric film layer 9, during the washing time span and at a washing temperature of at least 50? C., attains a contraction tension of at least 0.6 N/mm.sup.2 with a degree of contraction of at least 0.5%. It has been found that, if these parameters are observed, the label can be washed off on the basis of the biaxial stretching of the polymeric film material.

(11) It is understood that in actual practice the values for contraction tension and degree of contraction that are selected may also be higher, in order to increase the reliability of detachment. Also the washing temperature in many cases can be selected to be higher than 50? C. In order to be able to detach the label without splitting, however, maximum values for the contraction tension and the degree of contraction ought not to be exceeded. It has emerged as being suitable if the polymeric film layer 9 is designed such that the laminate in the two stretching directions of the polymeric film layer, within the mandated wash removal time span of, for example, 3 minutes at a washing temperature of 60? C., does not exceed a contraction tension of maximally 3.5 N/mm.sup.2 and a degree of contraction of maximally 20%, but more particularly maximally 13%. At a washing temperature of 70? C. the contraction tension should be below a maximum of 15 N/mm.sup.2, in particular below a maximum of 12 N/mm.sup.2, while the degree of contraction should be maximally 55%, more particularly maximally 36%. At a washing temperature of 80? C., the contraction tension ought not to exceed a value of maximally 18 N/mm.sup.2 and a degree of contraction of maximally 60%, in particular maximally 46%. In the case of a washing temperature of 90? C., the contraction tension ought not to exceed maximally 20 N/mm.sup.2 and a degree of contraction of maximally 65%, more particularly maximally 50%.

(12) There should also be certain minimum threshold values achieved for the contraction tension, in order to improve the reliability of detachment as a function of the washing temperature. At a washing temperature of 70? C., for instance, the polymeric film layer 9 ought in its two stretching directions to obtain a degree of contraction of at least 4% for a contraction tension of at least 1.5 N/mm.sup.2 during a washing time span of 3 minutes. In the case of a washing temperature of 80? C., the degree of contraction achieved in both stretching directions within the washing time span of 3 minutes ought to be at least 2%, and the contraction tension achieved under the same conditions ought to be at least 0.8 N/mm.sup.2.

(13) Depending on the washing temperature, the degree of contraction of the polymeric film layer 9 is less directionally dependent and considerably smaller than the degree of contraction of the polymeric film layer of conventional labels that are removable by washing, as shown by Table below for PET films:

(14) TABLE-US-00001 TABLE 1 Invention Prior art Degree of Degree of contraction contraction [%] [%] Washing temperature cross- length- cross- length- [? C.] wise wise wise wise 60? ?1.1 ?1.4 ?23.8 ?5.1 65? ?3.6 ?3.8 ?63.7 1.8 70? ?11 ?10.2 ?64.9 1.3 75? ?17.5 ?15.0 ?65.3 ?0.6 80? ?22.5 ?17.7 ?69.1 ?1.1 85? ?24.8 ?18.8 ?69.4 ?3.8 90? ?27.5 ?19.8 ?73.2 ?4.3 95? ?30.3 ?21.7 ?75.1 ?5.2

(15) The free contraction of the films was determined, by immersing the films for three minutes in water at the corresponding temperature.

(16) The degree of contraction in lengthwise direction is the degree of contraction in the longitudinal film web direction of the film production machine. The degree of contraction in the crosswise direction identifies the degree of contraction transverse to the longitudinal machine direction.

(17) Table 2 shows the maximum contraction tension of a PET film approximately 50 ?m thick, as used in accordance with the invention, in comparison to a PET film of the prior art. The maximum contraction tension developed on the PET film in accordance with the invention in both stretching directions is greater than the maximum contraction tension of conventional films. The table shows the maximum contraction tensions in comparison. The contraction tension is determined in accordance with DIN 53 369, the temperature being altered linearly at 20? K/h from 30 to 105? C. in a measurement chamber, instead of the DIN change rate of 50 or 120? K/h. With a rate of change of 20? K/h, the residence time is approximately 3 minutes at a temperature which is representative of the washing temperature.

(18) TABLE-US-00002 TABLE 2 PET film 50 ?m thick Maximum contraction crosswise lengthwise tension [N/mm.sup.2] [N/mm.sup.2] Invention 12.9 9.1 Prior art 8.7 0

(19) The above measurements in Table 1 show that the beginning of contraction of the polymeric film layer utilized in the context of the invention is located at a higher temperature than in the case of conventional, stretched, shrinkable polymeric films, in this case at about 65? C. in contrast to conventional films, which begin to contract at only about 55 to 60? C.

(20) In the case of the label 1 shown in FIGS. 1 and 2, the printed decoration layer 11, as viewed from the outside, is protected beneath the polymeric film layer 9, which where appropriate may also serve as a production carrier for the label. The adhesive layer 13 may be applied directly to the ink layer 11. Preferably, however, there is an interlayer 15 as an adhesive promoter between decoration layer 11 and the adhesive layer 13. The interlayer 15 may be a conventional primer layer. Preferably, the interlayer 15 is a reactive layer of two-component polyurethane laminating adhesive, which is able to crosslink not only with the decoration layer 11 but also with the adhesive layer 13. Advantageously the adhesive layer 13 is likewise composed of crosslinking polymer, more particularly of a crosslinking system which can be excited by radiation, such as, for example, UV-excitable adhesive material. The interlayer 15 raises the splitting resistance of the label 1.

(21) In the text below, variants of the label of FIGS. 1 and 2 are illustrated. Components having an equivalent effect are identified with the reference numbers of FIGS. 1 and 2, and to distinguish them are given a letter. For elucidation of the construction, the mode of action, and any variants, reference is made to the description of FIGS. 1 and 2.

(22) FIG. 3 shows a label 1a adhered to the outer surface 3a of the container 5a at the beginning of the detachment procedure. In contrast to the label 1 of FIGS. 1 and 2, the decoration layer 11a is printed via a primer layer 17 onto the biaxially stretched polymeric film layer 9a. In this example as well the decoration layer 11a is disposed between the adhesive layer 13a and the polymeric film layer 9a. The biaxially stretched polymeric film layer 9a is a constituent of a laminate composite layer 19 in which the biaxially stretched polymeric film layer 9a is joined two-dimensionally via an adhesive layer 21, for example, of laminating adhesive, to a further polymeric film layer 23. The overall laminate composite layer 19 is transparent, and so the decoration layer 11a remains visible from the outside. Through the lamination of the layers 9a and 23 it is possible to increase the contraction force of the label 1a if the polymeric film layer 23 is a monoaxially stretched film or, as is preferred in order to lessen the stresses in the assembly of materials, is likewise a biaxially stretched film. It is understood that the polymeric film layer 23 may also be of a non-shrinking design. In that case the contraction force of the label 1a would be reduced. If layers 9a and 23 which contract differently are laminated, the direction of the detachment movement of the label on contraction may be influenced and the detachment behavior may be improved.

(23) In the labels explained above, the decoration layer in the laminate is located between the biaxially stretched polymeric film layer and the adhesive layer. In the case of the label 1b of FIG. 4, the adhesive layer 13b is attached directly, or else, if appropriate, via an adhesive promoter layer, to the biaxially stretched polymeric film layer 9b, while the decoration layer 11b is printed onto the opposite side of the polymeric film layer 9b, which here as well serves as a production carrier. Attached to the decoration layer 11b via an adhesion promoter layer 25, e.g., a laminated adhesive layer, is a protective layer 27. The protective layer 27 may be a layer of protective varnish, or else a further, stretched or unstretched, polymeric film layer. Here as well the polymeric film layer may be biaxially or monoaxially stretched. Where the protective layer 27 is configured as a layer of protective varnish, there is no need for an adhesion promoter layer 25, e.g., a layer of laminating adhesive between the protective layer 27 and the decoration layer 11b. An option would be the use of an adhesion promoter layer in the form of a primer on the polymeric film layer 9b. In such a case the decoration layer 11b and the adhesion promoter layer 25 switch their positions with one another in FIG. 4.

(24) If a polymeric film is used as protective layer 27, the decoration layer 11b may also be applied to that polymeric film, and may be fixed to the polymeric film layer 9b via the adhesion promoter layer 25, more particularly a layer of laminating adhesive.