Stack sealable heat shrinkable film
Abstract
A heat shrink film having a shrinkage of at least 10% measured in accordance with ASTM 2732 in water at 90 ° C in at least one of the MD, TD directions, in which the film comprises an outer layer comprising an elastomer of polyester and a core barrier layer comprising EVOH and / or PVDC and an inner sealing layer.
Term
1.6 yearsto projected expiry
Projected expiry 17 April 2028, counted from filing; an application has no term until it is granted.
- Priority
- Filed
- Published
- Today
- Projected expiry
11 claims: 7 independent, 4 dependent
- 1ES 2 380 973 T3 IS 2 380 973 T3 CLAIMS REIVINDICACIONES 1. A heat shrink film having a shrinkage of at least 10% measured in accordance with ASTM 2732 in water at 90 ° C in at least one of the MD, TD directions, wherein the film comprises an outer layer comprising an elastomer of polyester and a core barrier layer comprising EVOH and / or PVDC and an inner seal layer. 1. Una película termorretráctil que tiene una retracción de al menos un 10% medida de acuerdo con ASTM 2732 en agua a 90 °C en al menos una de las direcciones MD, TD, en la que la película comprende una capa externa que comprende un elastómero de poliéster y una capa de barrera de núcleo que comprende EVOH y/o PVDC y una capa de sellado interior.
- 4La película de una o más de las reivindicaciones precedentes, en la que la película comprende además una capa adyacente, la capa adyacente une la capa externa a la capa de barrera de núcleo y comprende preferentemente poliolefina modificada con anhídrido maleico u otros materiales poliolefínicos. Four. The film of one or more of the preceding claims, wherein the film further comprises an adjacent layer, the adjacent layer bonds the outer layer to the core barrier layer and preferably comprises maleic anhydride modified polyolefin or other polyolefinic materials.
- 5The film of one or more of the preceding claims, wherein a tie layer is located between the seal layer and the core barrier layer and wherein the tie layer comprises ethylene-ester copolymers, such as copolymers ethylene-vinyl acetate, and / or ethylene-methyl acrylate copolymers, or wherein the tie layer includes maleic anhydride modified ethylene-ester copolymers or maleic anhydride modified LLDPE. 5. La película de una o más de las reivindicaciones precedentes, en la que entre la capa de sellado y la capa de barrera de núcleo se sitúa una capa de sujeción y en la que la capa de sujeción comprende copolímeros de etileno-éster, tales como copolímeros de etileno-acetato de vinilo, y/o copolímeros de etileno-acrilato de metilo, o en la que la capa de sujeción incluye copolímeros de etileno-éster modificados con anhídrido maleico o LLDPE modificados con anhídrido maleico.
- 7The film of one or more of the preceding claims, wherein any of the layers includes additives such as slip agents, antiblocking, polymer processing aids, antistatic, antifog, acid sequestrants or odor sequestrants. 7. La película de una o más de las reivindicaciones precedentes, en la que cualquiera de las capas incluye aditivos tales como agentes deslizantes, antibloqueo, coadyuvantes de procesado de polímeros, antiestático, antivaho, secuestrantes de ácidos o secuestrantes de olores.
- 8The film of one or more of the preceding claims, wherein the heat shrink film is irradiated after extrusion. 8. La película de una o más de las reivindicaciones precedentes, en la que la película termorretráctil se irradia después de la extrusión.
- 9A bag or sachet comprising a film according to one or more of the preceding claims. 9. Una bolsa o bolsita que comprende una película de acuerdo con una o más de las reivindicaciones precedentes.
- 11Un procedimiento para producir un artículo alimenticio envasado que comprende las etapas de:eleven. A process for producing a packaged food item comprising the steps of: a) proporcionar una bolsa o bolsita de la reivindicación 9, a) providing a pouch or sachet of claim 9, b) poner un artículo alimenticio dentro de la bolsa o bolsita;b) putting a food item inside the bag or sachet;c) removing the air (vacuum procedure) from the bag or sachet;c) retirar el aire (procedimiento de vacío) de la bolsa o bolsita;d) sealing the open end of the bag or sachet;Y d) sellar el extremo abierto de la bolsa o bolsita;y e) colocar el envase a vacío en un medio de termorretracción, preferentemente agua caliente bajo una temperatura que garantice la retracción del envase (p. ej. 90 °C). e) place the vacuum container in a heat shrinkage medium, preferably hot water at a temperature that guarantees the shrinkage of the container (eg 90 ° C).
Independent claims7
107 paragraphs in 7 sections, as filed
IS 2 380 973 T3
DESCRIPTION
Overlap Sealable Heat Shrink Film
The present invention relates to a multilayer heat shrink film characterized by a combination of desirable properties, such as high shrinkage, good optical properties, sealability, and excellent overlap sealability. The invention also relates to a process for the production of a packaged food item using said film. The invention further relates to the use of said film or of bags and containers made from it to package articles such as food products.
In general, the packaging of food items by means of a heat shrink bag comprises the following steps
1. Put the food item into the bag and remove the air (subjecting it to a vacuum) with the help of a vacuum device.
2. Seal the open end of the bag.
3. Place the vacuum container in a heat shrinkage medium, such as hot water, at a temperature that guarantees the container shrinkage (eg 90 ° C).
Four. The package is prepared and characterized by an attractive appearance and a long shelf life due to the absence of oxygen.
These films need high shrink properties and good optical properties to ensure excellent appearance and excellent sealability, so that there is no oxygen ingress into the package, as this would be detrimental to the shelf life of the food.
In some cases, when food is stored in freezing conditions, for example, there is the possibility of using a film without a gas barrier. The other characteristics are the same.
Packaging films with the above properties are well known in the art.
A problem often encountered in the art is that during the packaging process, operators must deposit food into the bags more carefully, as they must avoid overlapping of the bags. When overlapping or partially overlapping containers are vacuum-sealed and sealed, the outer surfaces of the two (or more) bags are sealed to each other under the conditions of temperature and pressure used to ensure the sealability of the inner surfaces. This can lead to many defective products and a loss of productivity. This situation, in particular, occurs in overlap closure procedures, that is, in a situation, in which two or more products are placed on top of each other and then sealed.
If the operator tries to modify the temperature, the sealing time, the pressure conditions, there is a high possibility that the internal surfaces will not seal sufficiently.
The use of bags that can be heat sealed when overlapping occurs, without problems of insufficient sealing force or sealing of the external surfaces could lead to higher productivity, a shorter cycle of each packaged product and the attention required by the minor operator.
The problem to be solved has been dealt with in the past:
EP 1131205 refers to the use of a high melting point polyamide in the outer layer. The use of this material has the disadvantage that it reduces the shrinkage of the final film due to the high Vicat point of this resin. Therefore, this approach is not suitable for heat shrink films and products made from them.
EP0810087 also suggests the use of polyester, polyamide and EVOH materials in coextrusion.
EP 1060077 refers to the use of a polyester material in the outer layer and a polyamide in the core layer. This material also has a high Vicat point and reduces shrinkage of the multilayer product.
EP 1415930 A1 relates to the use of release blends comprising polybutylene in the outer layer. The problem in this case is that there is a high risk of deterioration of the optical properties since the outer layer (which contributes greatly to the optical properties of the combination) consists of the mixture of two incompatible polymers that can make a cohesive skin. . The outer layer should comprise an easily peelable blend so that overlap sealability is easily achieved. The release composition is applied by extrusion, coextrusion or coating of a substrate.
IS 2 380 973 T3
Summary of the invention
Therefore, the essential problem of the invention is to provide a heat sealable film, which can be advantageously used in overlap sealing applications. Another problem of the invention is to prevent the external surfaces of the two (or more) bags in overlapping sealing applications from sealing one another under the conditions of temperature and pressure used to guarantee the sealability of the internal surfaces. A further problem is to provide bags that can be heat sealed when overlapping occurs, without problems of insufficient sealing force and sealing of the outer surfaces. A further problem is to provide a film for overlap sealing applications having excellent optical properties and high heat shrinkage. Still another problem is that of avoiding the use of polyamide resin in the framework due to the following disadvantages:
1. Polyamide does not have dimensional stability in high humidity conditions. This means that it can potentially create problems stabilizing the length and width of the bags exposed to the atmosphere.
2. The shrinkage capacity of polyamide is low.
These problems are overcome by object of the independent claims. Preferred embodiments are set out in the dependent claims.
The inventors have managed to overcome all these problems by discovering a film that combines
1. Excellent overlap sealability
2. Excellent sealing properties under a wide variety of machine conditions.
3. Excellent optical properties
Four. Manufacture in a controlled and stable way.
5. High shrink capacity
This is accomplished by a heat shrink film incorporating a polyester elastomer outer layer and a core layer comprising EVOH and / or PVDC.
Definitions:
The following definitions are used in this application:
The term film refers to a flexible flat or tubular structure of thermoplastic material.
The term "heat shrinkable" refers to a film that shrinks by at least 10% in at least one of the longitudinal and transverse directions when heated to 90 ° C for 4 seconds. Shrinkage ability is measured in accordance with ASTM 2732.
The term "longitudinal direction" or "machine direction" abbreviated herein as "MD" refers to a direction along the length of the film.
The term "outer layer" refers to the layer of film that is in immediate contact with the external environment (atmosphere).
The term "inner layer" refers to the layer of film that is in direct contact with the packaged product. This is also called a sealing layer as this layer must be hermetically closed to protect the product from the entry of air.
The term "core layer" refers to all the film layers that exist between the outer and inner film layers.
The term "adjacent layer" refers to a layer that is to bond the outer layer to the core barrier layer. The adjacent layer preferably comprises maleic anhydride modified polyolefin or other polyolefin tie down layer.
As used herein, the term "homopolymer" refers to a polymer that results from the polymerization of a single monomer.
As used herein, the term "copolymer" refers to a polymer that results from the polymerization of at least two different polymers.
As used herein, the term "polymer" includes both of the above types.
IS 2 380 973 T3
As used herein, the term polyethylene identifies polymers that consist essentially of the repeating unit of ethylene. Those with a density greater than 0.940 are called high-density polyethylene (HDPE), those with less than 0.940 are low-density polyethylene (LDPE).
As used herein, the term "ethylene-alpha-olefin copolymer" refers to polymers such as linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), very low density polyethylene (VLDPE), ultra low density (ULDPE), metallocene catalyzed polymers and polyethylene plastomers and elastomers.
As used herein, the term "styrene polymers" refers to homopolymer of styrene, such as copolymers of polystyrene and styrene, such as copolymers of styrene-butadiene, copolymers of styrene-butadiene-styrene, copolymers of styrene-isoprene- styrene, styrene-ethylene-butadiene-styrene copolymers, ethylene-styrene copolymers, and the like.
As used herein, the term "methacrylate-ethylene copolymers" refers to copolymers of methacrylate-ethylene monomer. The monomer content is less than 40%.
As used herein, the term "ethylene-vinyl acetate copolymer" refers to copolymers of ethylene and vinyl acetate.
As used herein, the term EVOH refers to saponified products of ethylene vinyl ester copolymers. Typically, the ethylene content is in the range of 25 to 50%.
As used herein, the term PVDC refers to a vinylidene chloride copolymer, in which a large amount of the copolymer comprises vinylidene chloride and a minor amount of the copolymer comprises one or more monomers, such as vinyl chloride. and / or alkyl acrylates and methacrylates. Typically, the PVDC copolymer may comprise heat stabilizers and plasticizers, as is well known in the art.
As used herein, the term polyamide refers to homopolymers and copolymers.
As used herein, the term "polyester elastomer" refers to block copolymers in which there are hard and soft blocks in the polymer chain. Examples of this type of polymers are polyester-ether and polyester-ester copolymers, such as ARNITEL® from DSM, HYTREL® from Dupont and RITEFLEX® from TICONA.
All the measurement procedures mentioned in this document are readily available to the skilled person. For example, they can be obtained from the American National Standards Institute at: www.webstore.ansi.org
Detailed description of the invention
According to a first aspect, the present invention relates to a heat shrink film having a shrinkage of at least 10% measured according to ASTM 2732 in water at 90 ° C in at least one of the directions MD, TD, in wherein the film comprises an outer layer comprising a polyester elastomer and a core layer comprising EVOH and / or PVDC.
A preferred resin for the outer layer according to the invention is a polyester elastomer, preferably an ether elastomer. The melting point of this material is preferably 190 ° C to 220 ° C. A blend of this polymer with a non-elastomeric copolyester (eg, polybutylene terephthalate) is also beneficial.
The adjacent layer preferably comprises maleic anhydride modified polyolefin or other polyolefin tie down layer. The purpose of this layer is to bond the outer layer to the core barrier layer.
The core barrier layer comprises an oxygen barrier material selected from EVOH and PVDC. PVDC is preferable to higher shrinkage capacity.
In the case of EVOH, a small proportion of special polyamide can be used to increase the flexibility of EVOH.
Between the sealing layer and the oxygen barrier layer, a tie layer could be used. Preferred materials in this tie layer can be ethylene-ester copolymers, such as ethylene-vinyl acetate copolymers, ethylene-methyl acrylate copolymers, and other materials well known in the art. A preferred version may include maleic anhydride modified ethylene ester copolymers or maleic anhydride modified LLDPE. Trademarks are, for example, BYNEL from Dupont and ADMER from Mitsui.
The inner heat seal layer of the film may comprise ethylene-alpha-olefin copolymers and / or ethylene-propylene copolymers or terpolymers. Typical examples are AFFINITY® homogeneous polymers (DOW),
IS 2 380 973 T3
EXACT® (EXXON), TAFMER® (MITSUI), ethylene-vinyl acetate copolymers and others well known in the layer polymer sealing art.
Between the outer and barrier layer there may be another layer incorporating a tie layer. Preferred materials in this tie layer can be ethylene-ester copolymers, such as ethylene-vinyl acetate copolymers, ethylene-methyl acrylate copolymers, and other materials well known in the art. A preferred version may include maleic anhydride modified ethylene ester copolymers or maleic anhydride modified LLDPE. Trademarks are, for example, BYNEL from Dupont and ADMER from Mitsui.
Any of the layers described above can also include additives well known in the art, such as slip agents, antiblocking, polymer processing aids, antistatic, antifog, acid sequestrants, odor sequestrants, and the like. One skilled in the art can select the correct additives according to particular needs.
In a preferred embodiment, the heat shrink film is irradiated after extrusion. An electron beam is a recommended procedure to cross-link the structure and increase the mechanical properties.
In another aspect, the invention relates to the use of the films or the bag or sachet of the invention for packaging food and a method for packaging food items. For example, the food item is put into the bag and the air is removed (vacuum procedure) with the help of a vacuum device. Subsequently, the open end of the bag is sealed and the container is placed under vacuum in a heat shrinkage medium, such as hot water under a temperature that guarantees the container shrinkage (eg 90 ° C). The container is then prepared and characterized by an attractive appearance and a long shelf life due to the absence of oxygen.
The present invention is now described by the following examples:
Example 1
A 5 layer film is produced on a commercial double bubble line with the following formula
Interior (sealing layer) 32% P1 + 30% P2 + 20% E1 + 10% E2 + 8% additives
The percentage is in% by weight unless otherwise indicated.
<td>Adjacent layer</td><td>D1</td>
<td>Barrier layer</td><td>Commercial grade PVDC</td>
<td>Adjacent layer</td><td>D2</td>
<td>Outer layer</td><td>PEE 1</td>
See table 1.
The frame thickness is 26/7/7/7/8 starting from the inside and going to the outer layer.
Example 2
A 5 layer film is produced on a commercial double bubble line with the following formula
Interior (sealing layer) 32% P1 + 30% P2 + 20% E1 + 10% E2 + 8% additives
<td>Adjacent layer</td><td>D1</td>
<td>Barrier layer</td><td>EVOH 44% ethylene content</td>
<td>Adjacent layer</td><td>D2</td>
<td>Outer layer</td><td>PEE1</td>
See table 1.
The frame thickness is 26/7/7/7/8 starting from the inside and going to the outer layer.
TABLE 1
<td>Guy</td><td>Description</td><td>Maker</td><td>Melt index g / 10 min</td><td>Density g / cm<sup>3</sup></td><td>Melting point ° C.</td>
<td>E1</td><td>EVE</td><td>Dupont3135X</td><td> 0,35</td><td> 0,93</td><td> 95</td>
ES 2 380 973 T3 (continued)
<td>Guy</td><td>Description</td><td>Maker</td><td>Melt index g / 10 min</td><td>Density g / cm<sup>3</sup></td><td>Melting point ° C.</td>
<td>E2</td><td>EVE</td><td>1005VN2</td><td> 0,40</td><td> 0,928</td><td> 102</td>
<td>D1</td><td>MODIFIED LLDPE</td><td>MITSUI ADMER 518</td><td> 3</td><td> 0,91</td><td></td>
<td>P1</td><td>Plastomer</td><td>Dow Affinity VP 8770</td><td> 1,0</td><td> 0,885</td><td> 74</td>
<td>PEE1</td><td>ELASTOMER OF POLYESTER</td><td>ARNITEL EM 630</td><td>7 at 230C</td><td> 1,25</td><td> 213</td>
<td>D2</td><td>MODIFIED EVA</td><td>BYNEL 3861</td><td></td><td></td><td></td>
<td>P2</td><td>PLASTOMER</td><td>DOW AFFINITY PL 1880</td><td> 1,0</td><td> 0,902</td><td> 100</td>
Tests
1. Measurement of turbidity. Haze measurement was performed in accordance with ASTM D 1003.
2. Gloss measurement. This was done in accordance with BS 2782.
3. Shrinkage measurement performed in accordance with ASTM 2732.
Four. Sealing window.
The final test was performed on a Bosch vacuum sealing machine. One piece of the tube of each material was placed over another so that there is an overlapping area. This area is sealed and then removed. The material is supposed to be fine if the outer surfaces are easily removed without any delamination or resistance and the inner (sealing layers) are at the same time tightly sealed. Different seal times were applied to see which of the 10 three materials has the longest operating window.
The results are presented in Table 2
TABLE 2
<td></td><td>TURBID EZ</td><td>BRIGHTNESS</td><td>RETRACTION (MD / TD)</td><td>SEALING WINDOW IN OVERLAP (sealing times)</td>
<td>Material 1</td><td> 6</td><td> 93</td><td> 52/40</td><td> 4-10</td>
<td>Material 2</td><td> 7</td><td> 98</td><td> 42/41</td><td> 4-10</td>
<td>Comparison</td><td> 10</td><td> 95</td><td> 35/42</td><td> 4-10</td>
Thus, the materials have the same overlapping operating window and combine greatly improved shrinkage properties as well as excellent optical properties, in the case of material 1,2.
Contents7
10 members in 6 offices
Priority claims5
| Document | Office | Kind | Date |
|---|---|---|---|
| 07107035 | European Patent Office (EPO) | A | |
| 07107035 | European Patent Office (EPO) | A | |
| 07107035 | European Patent Office (EPO) | – | |
| 07107035 | – | – | – |
| EP20070107035 | – | – | – |
Members10
| Document | Office | Kind | |
|---|---|---|---|
| EP1985443A2 | European Patent Office (EPO) | A2 | |
| US2008274314A1 | United States of America | A1 | |
| AU2008201820A1 | Australia | A1 | |
| EP1985443A3 | European Patent Office (EPO) | A3 | |
| NZ567767A | New Zealand | A | |
| EP1985443B1 | European Patent Office (EPO) | B1 | |
| ATE531515T1 | Austria | T1 | |
| ES2380973T3This record | Spain | T3 | |
| AU2008201820B2 | Australia | B2 | |
| US8697211B2 | United States of America | B2 |
Numbers
- Publication
- 2380973
- Publication, DOCDB
- 2380973
- Publication, EPODOC
- ES2380973T
- Application
- 8154742
- Application, DOCDB
- 08154742
- Application, EPODOC
- ES20080154742T
Titles2
- Spanish
- Película termorretráctil sellable en superposición
- English
- Overlay sealable shrink film
Classification
- CPC, 18
- B32B27/08
- B32B27/36
- B32B7/12
- B32B27/16
- B32B27/18
- B32B27/304
- B32B27/306
- B32B27/308
- B32B27/32
- B32B2270/00
- B32B2307/31
- B32B2307/40
- B32B2307/7244
- B32B2307/736
- B32B2439/70
- Y10T428/1328
- Y10T428/1359
- Y10T428/31797
- IPC, 4
- B32B27 08
- B65D65 40
- B32B27 36
- B31B50 64