Multilayer heat shrinkable cook-in film

0001The present invention is directed to a cook-in film and to bags, pouches and the like made therefrom. The invention is further directed to a method of producing and preserving a food product using such a film, bag or pouche and to a packaged food product obtained therefrom.

0002Many food products are processed in thermoplastic film packages by subjecting the packed product to elevated temperatures produced by, for example, exposure to steam, hot air or immersion into boiling water. This thermal processing is usually called cook-in and the films used for such applications are generally called cook-in films.

0003A cook-in film must be capable of withstanding exposure to severe temperature conditions like immersion in hot water of temperature 70 to 90 °C for a time period of about 4 to 18 hours. During these severe thermal conditions, the film should be able to withstand <ol id="ol0001" compact="compact" ol-style=""><li>1. Opening of the seals</li><li>2. Delamination of the different layers of the multilayer structure.</li></ol>

0004A further desirable effect of the cook-in films is heat shrinkability, which is the ability of a film to shrink under heat conditions so that it conforms tightly to the packed food and gives a good aesthetic appearance.

0005A further desirable effect is good optical properties, meaning high gloss and low haze of the film, providing a nice presentation to the consumer.

0006Another desirable effect is the ability of the film to heat seal effectively in commercial bag making machines. The reason for this is that very often, the film is used in the form of a bag (pouch) in which the product is packed under vacuum and then is put in a hot water bath or in a steam container in order to be cooked.

0007Thus, it would be desirable to make a heat shrinkable film combining all these different requirements <ol id="ol0002" compact="compact" ol-style=""><li>1. Resistance to bag opening and delamination</li><li>2. High shrinkage</li><li>3. Excellent optics</li><li>4. Efficient heat sealability</li></ol>

0008It is also known in the art a similar process called post pasteurization. Many foods require pasteurization after being hermetically packed so that harmful microbes are destroyed. Specific pasteurization requirements may vary from country to country but 1 hour at 95°C is considered a possible limiting case. The film of the invention may be used also to withstand these conditions.

0009In the prior art, often polypropylene copolymers have been proposed to be used in cook-in applications. These copolymers generally have vicat softening point more than 115°C. This makes the film hard to seal in an effective way both by the producer and by the packer of the final product before the cook-in process. This problem is addressed and solved by the structures of this application, without sacrificing the cook-in performance.

SUMMARY OF THE INVENTION

0010It is, therefore, an object of the present invention to provide a heat shrinkable multilayer film having excellent optics, efficient heat sealability, resistance to bag seal opening (failure) and delamination. It is a further object of the present invention to provide a cook-in film having the above properties.

0011These objects are achieved by the subject-matter of the independent claims. Preferred embodiments are set forth in the dependent claims.

0012The invention is based on the surprising insight that multilayer films for high temperature applications (up to about 95°C; so called cook-in films) may be produced by introducing a heat sealing layer comprising a polypropylene polymer with a vicat softening point of less than 105°C. This is surprising since a skilled person having average knowledge in this field would expect those films to be unstable. In particular, a skilled person would expect opening of the seals and delaminating of the different layers of the multilayer structure, if a sealing layer comprising a polypropylene polymer with a vicat softening point of less than 105°C is chosen.

0013However, it surprisingly turned out that the multilayer films of the present invention remained stable under these circumstances, i.e. did not show opening of the seals and delamination. Moreover, and even more unexpected, the multilayer film of the invention showed an improved heat sealability due to using an inner heat sealing layer having the above properties.

0014Thus, a very stable multilayer film for cook-in applications could be generated having improved characteristics regarding opening of the seals and delamination, but also regarding heat-shrinkability and optics.

0015Briefly the invention provides an oriented heat shrinkable film comprising a heat sealing layer comprising a polypropylene polymer with a vicat softening point of less than 105°C. The heat sealing layer is the inner layer. Other layers may include an oxygen barrier layer and an outer layer comprising polyolefin polymer or styrene butadiene copolymer.

0016The heat sealing layer may comprise a blend of the polypropylene polymer with other materials but the vicat softening point of the blend should be less than 105°C. The vicat softening point of a blend is calculated as follows: <maths id="math0001" num=""><math display="block"><mi>Vb</mi><mo mathvariant="normal">=</mo><mi mathvariant="normal">x</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">*</mo><mi mathvariant="normal">v</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">+</mo><mi mathvariant="normal">x</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal">*</mo><mi mathvariant="normal">v</mi><mo>⁢</mo><mn mathvariant="normal">2</mn></math><img file="EP1854625A1_D0001.tif" /></maths> where <dl id="dl0001" compact="compact"><dt>Vb=</dt><dd>softening point of the blend</dd><dt>V1=</dt><dd>softening point of component 1</dd><dt>V2=</dt><dd>softening point of component 2</dd><dt>X1=</dt><dd>percentage per mass of component 1 in the blend</dd><dt>X2=</dt><dd>percentage per mass of component 2 in the blend</dd></dl>

0017The definitions used in the following are as follows:

0018The term " film" refers to a flat or tubular flexible structure of thermoplastic material. A "cook-in film" is more specifically defined as being a film adapted for high temperature applications, e.g. treatment with hot water at temperatures up to about 95°C.

0019The term "heat shrinkable" refers to a film that shrinks at least 10% in at least one of the longitudinal and transverse directions when heated at 90°C for 4 seconds. The shrinkability is measured according to ASTM 2732. This test method covers the determination of the degree of unrestrained linear thermal shrinkage at given specimen temperatures of a plastic film and sheeting of 0.76 mm thickness or less.

0020All measurement methods mentioned herein are readily available for the skilled person. For example, they can be obtained from the American National Standards Institute at: <u style="single">www.webstore.ansi.org</u>

0021The phrase "longitudinal direction" or " machine direction" herein abbreviated " MD" refers to a direction along the length of the film.

0022The phrase "outside layer" refers to the film layer which comes in immediate contact with the outside environment (atmosphere).

0023The phrase "inner layer" refers to the film layer that comes in direct contact with the product packed. This is also called "sealing layer" as this layer must be hermetically sealed in order to protect the product from ingress of air.

0024As used herein, the term "homopolymer" refers to a polymer resulting from polymerization of a single monomer.

0025As used herein, the term "copolymer" refers to a polymer resulting from polymerization of at least two different polymers.

0026As used herein, the term "polymer" includes both above types.

0027As used herein the term "polyethylene" identifies polymers consisting essentially of the ethylene repeating unit. The ones that have a density more than 0.940 are called high density polyethylene (HDPE), the ones that are have less than 0.940 are low density polyethylene (LDPE).

0028As used herein the phrase "ethylene alpha olefin copolymer" refers to polymers like linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), very low density polyethylene (VLDPE), ultra low density polyethylene (ULDPE), metallocene catalysed polymers and polyethylene plastomers and elastomers.

0029As used herein the phrase "styrene polymers" refers to styrene homopolymer such as polystyrene and to styrene copolymers such as styrene-butadiene copolymers, styrene-butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-ethylene-butadiene-styrene copolymers, ethylene-styrene copolymers and the like.

0030As used herein the phrase "ethylene methacrylate copolymers" refers to copolymers of ethylene and methacrylate monomer. The monomer content is preferably less than 40%.

0031As used herein the phrase "ethylene vinyl acetate copolymer" refer to copolymers of ethylene and vinyl acetate.

0032As used herein, the term EVOH refers to saponified products of ethylene vinyl ester copolymers. The ethylene content is typically in the range of 25 to 50%.

0033As used herein the term PVDC refers to a vinylidene chloride copolymer wherein a major 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.

0034As used herein the term polyamide refers to homopolymers and copolymers.

0035As used herein the term "polypropylene" refers to any homopolymer, copolymer, terpolymer, tetrapolymer etc. that includes mer units of propylene. The term as used in the present application includes homopolymers, random copolymers, propylene alpha olefin copolymers, propylene ethylene copolymers propylene-ethylene-alpha olefin copolymers and other propylene polymers.

DETAILED DESCRIPTION

0036According to a first aspect, the present invention provides a heat shrinkable film comprising a heat sealing layer comprising a polypropylene polymer with a vicat softening point of less than 105°C, preferably less than 100°C, measured according to ASTM D 1525.

0037More precisely, the heat sealing layer of the multilayer film of the present invention comprises a polypropylene (PP) homopolymer or copolymer and has a vicat softening point of less than 105°C measured under ASTM D 1525.

0038PP might be present as a heterogeneous or a homogeneous polymer produced with single site catalyst. It may also be a blend of such a material with the following <ol id="ol0003" compact="compact" ol-style=""><li>1. another PP polymer such as random copolymer or homopolymer(among others)</li><li>2. a polyethylene polymer such as an alpha olefin copolymer with density 0.860 to about 0.960 or such as an ethylene ester copolymer</li><li>3. a cyclic olefin copolymer</li><li>4. a styrene polymer</li><li>5. an ionomer or a methacrylic acid copolymer</li><li>6. polybutene polymer</li></ol>

0039In a preferred case, the vicat softening point of the heat sealing layer is less than 100°C. As mentioned above, this is an unexpected effect, as the vicat softening point of the polymer is so close to the actual thermal conditions that the material is subjected (going up to 95°C).

0040The Vicat softening point is the determination of the softening point for materials such as polypropylene or polyethylene, which have no definite melting point. It is taken as the temperature at which the specimen is penetrated to a specified depth by a flat-ended needle with a defined circular or square cross-section, under a specified load.

0041In another preferred case, the PP polymer of the heat sealing layer is blended with an ethylene alpha olefin copolymer which has a vicat softening point less than 100°C.

0042Examples of polymers that could be useful are <ul id="ul0001" list-style="dash" compact="compact"><li>Homogeneous ethylene alpha olefin copolymers like the EXACT grades from EXXON;</li><li>Homogeneous ethylene alpha olefin copolymers with long chain branching such as the AFFINITY grades from DOW;</li><li>TAFMER linear ethylene alpha olefin copolymers from MITSUI.</li></ul>

0043The oxygen barrier used may be a material such as a polyvinylidene chloride homopolymer or copolymer or an ethylene vinyl alcohol copolymer (EVOH). Other oxygen barrier materials are also well known in the art. As example, oxygen barrier materials, also polyamides or polyesters may be used.

0044In the outside layer the following materials may be used <ol id="ol0004" compact="compact" ol-style=""><li>1. a polypropylene homopolymer or copolymer having a vicat softening point of less than 105°C measured under ASTM D 1525. It is preferably a homogeneous polymer produced with single site catalyst,</li><li>2. PP polymer such as random copolymer or homopolymer (among others)</li><li>3. Polyethylene polymer such as an alpha olefin copolymer with density 0.860 to about 0.960 or such as an ethylene ester copolymer</li><li>4. a cyclic olefin copolymer</li><li>5. a styrene polymer</li><li>6. an ionomer or a methacrylic acid copolymer</li></ol>

0045A preferred version comprises a <ol id="ol0005" compact="compact" ol-style=""><li>1. styrene butadiene copolymer</li><li>2. a blend of styrene butadiene copolymer and an ethylene alpha olefin copolymer</li><li>3. a reactor made TPO polymer incorporating propylene mer units</li><li>4. a blend of a reactor made TPO polymer incorporating propylene mer units and polypropylene homopolymer or copolymer</li><li>5. a propylene ethylene polymer with a vicat softening point less than 100°C</li><li>6. a blend of two propylene ethylene polymers with a vicat softening point less than 100°C</li></ol>

0046Between the inner heat sealing layer and the oxygen barrier layer may exist further layers that could comprise any of the polymers mentioned in the possibilities for inner heat sealing layer. Preferred materials are ethylene vinyl acetate, ethylene alpha olefin copolymers, EMA polymers, polypropylene copolymers, polybutylene, styrene homopolymers or copolymers.

0047Any of the layers described above may also include additives well known in the art such as slip agents, antiblock, polymer processing aids, antistatic, antifog, acid scavengers, odour scavengers and the like. A person skilled in the art may select the right additives according to any particular needs.

0048In a preferred version of the application, the film is irradiated with e beam radiation of levels from 1 to 10 MRAD.

0049All the percentages indicated in this application are per weight except if differently stated.

EXAMPLES

Example 1

0050A 5 layer film is produced in a double bubble (the double bubble method is described in <patcit id="pcit0001" dnum="US3456044A"><text>US 3,456,044</text></patcit>, incorporated herein by reference) commercial line with the following structure: <tables id="tabl0001" num="0001"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="54mm" /><tbody><row><entry>Inner (sealing) layer,</entry><entry>100% PP1</entry></row><row><entry>Adjacent layer</entry><entry>93% E1 + 7% ADDITIVES</entry></row><row><entry>Barrier layer</entry><entry>PVDC commercial grade</entry></row><row><entry>Adjacent layer</entry><entry>30% M1+ 65% E3+ 5% ADDITIVES</entry></row><row><entry>Outer layer</entry><entry>95% S1 + 5% ADDITIVES</entry></row></tbody></tgroup></table></tables> See table 1,2

Example 2

0051A 5 layer film is produced in a double bubble (the double bubble method is described in <patcit id="pcit0002" dnum="US3456044A"><text>US 3,456,044</text></patcit>) commercial line with the following recipe <tables id="tabl0002" num="0002"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="54mm" /><tbody><row><entry>Inner(sealing layer),</entry><entry>80%PP1+20% PP2</entry></row><row><entry>Adjacent layer</entry><entry>93% E1+7% ADDITIVES</entry></row><row><entry>Barrier layer</entry><entry>PVDC commercial grade</entry></row><row><entry>Adjacent layer</entry><entry>30% M1+ 65% E3+ 5% ADDITIVES</entry></row><row><entry>Outer layer</entry><entry>95% S1+ 5% ADDITIVES</entry></row></tbody></tgroup></table></tables>

Example 3

0052A 5 layer film is produced in a double bubble (the double bubble method is described in <patcit id="pcit0003" dnum="US3456044A"><text>US 3,456,044</text></patcit>, included herein by reference) commercial line with the following recipe <tables id="tabl0003" num="0003"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="54mm" /><tbody><row><entry>Inner(sealing layer),</entry><entry>100% PP3</entry></row><row><entry>Adjacent layer</entry><entry>93% E1+ 7% ADDITIVES</entry></row><row><entry>Barrier layer</entry><entry>PVDC commercial grade</entry></row><row><entry>Adjacent layer</entry><entry>30% M1+ 65% E3+ 5% ADDITIVES</entry></row><row><entry>Outer layer</entry><entry>95% S1+ 5% ADDITIVES</entry></row></tbody></tgroup></table></tables> See table 1, 2

Example 4

0053A 5 layer film is produced in a double bubble commercial line with the following recipe: <tables id="tabl0004" num="0004"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="57mm" /><tbody><row><entry>Inner(sealing layer),</entry><entry>95% PP1+5% B 1</entry></row><row><entry>Adjacent layer</entry><entry>93% E1+ 7% ADDITIVES</entry></row><row><entry>Barrier layer</entry><entry>PVDC commercial grade</entry></row><row><entry>Adjacent layer</entry><entry>30% M1+ 65% E3+ 5% ADDITIVES</entry></row><row><entry>Outer layer</entry><entry>60% PP1+ 35% PP6+5% ADDITIVES</entry></row></tbody></tgroup></table></tables>

Example 5

0054A 5 layer film is produced in a double bubble commercial line with the following recipe: <tables id="tabl0005" num="0005"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="57mm" /><tbody><row><entry>Inner(sealing layer),</entry><entry>95% PP1+10% B1</entry></row><row><entry>Adjacent layer</entry><entry>93% E1+7% ADDITIVES</entry></row><row><entry>Barrier layer</entry><entry>PVDC commercial grade</entry></row><row><entry>Adjacent layer</entry><entry>30% M1+ 65% E3+ 5% ADDITIVES</entry></row><row><entry>Outer layer</entry><entry>60% PP1 + 3 5% PP6+5% ADDITIVES</entry></row></tbody></tgroup></table></tables>

Example 6

0055A 5 layer film is produced in a double bubble commercial line with the following recipe: <tables id="tabl0006" num="0006"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="57mm" /><tbody><row><entry>Inner(sealing layer),</entry><entry>95% PP1+15% B1</entry></row><row><entry>Adjacent layer</entry><entry>93% E1+7% ADDITIVES</entry></row><row><entry>Barrier layer</entry><entry>PVDC commercial grade</entry></row><row><entry>Adjacent layer</entry><entry>30% M1+ 65% E3+ 5% ADDITIVES</entry></row><row><entry>Outer layer</entry><entry>60% PP1+ 35% PP6+5% ADDITIVES</entry></row></tbody></tgroup></table></tables>

Example 7

0056A 5 layer film is produced in a double bubble commercial line with the following recipe: <tables id="tabl0007" num="0007"><table frame="none"><tgroup cols="2" colsep="0" rowsep="0"><colspec colnum="1" colname="col1" colwidth="34mm" /><colspec colnum="2" colname="col2" colwidth="45mm" /><tbody><row><entry>Inner(sealing layer),</entry><entry>95% PP1+5% B1</entry></row><row><entry>Adjacent layer</entry><entry>93% E1+7% ADDITIVES</entry></row><row><entry>Barrier layer</entry><entry>PVDC commercial grade</entry></row><row><entry>Adjacent layer</entry><entry>25% PP1+25% B2+ 50% M1</entry></row><row><entry>Outer layer</entry><entry>90% PP4+ 10% PP5</entry></row></tbody></tgroup></table></tables> See table 1, 2

0057In all the above examples, the thickness of the layers are (in microns) <dl id="dl0002" compact="compact"><dt>8,</dt><dd>outer layer</dd><dt>10,</dt><dd>adjacent layer</dd><dt>4,</dt><dd>barrier layer</dd><dt>6,</dt><dd>adjacent layer</dd><dt>27,</dt><dd>heat sealing layer</dd></dl>

Comparative example

0058Under exactly the same conditions a commercial product FMXBK was produced. It is noted that FMXBK does not contain polypropylenes of the specific kind as defined in the invention in the sealing layer.

0059All the samples were e-beam radiated with a dose of 4 MRAD prior to bag making. <tables id="tabl0008" num="0008"><table frame="all"><title>TABLE 1</title><tgroup cols="7"><colspec colnum="1" colname="col1" colwidth="12mm" /><colspec colnum="2" colname="col2" colwidth="35mm" /><colspec colnum="3" colname="col3" colwidth="36mm" /><colspec colnum="4" colname="col4" colwidth="31mm" /><colspec colnum="5" colname="col5" colwidth="25mm" /><colspec colnum="6" colname="col6" colwidth="14mm" /><colspec colnum="7" colname="col7" colwidth="14mm" /><thead><row><entry valign="top">Type</entry><entry valign="top">Description</entry><entry valign="top">Manufacturer</entry><entry valign="top">Melt Index g/10 min</entry><entry valign="top">Density g/cm³</entry><entry namest="col6" nameend="col7" align="left" valign="top">Melting point °C.</entry></row></thead><tbody><row><entry>E1</entry><entry>EVA</entry><entry>Dupont 3135 X</entry><entry>0.35</entry><entry>0.93</entry><entry namest="col6" nameend="col7" align="left">95</entry></row><row><entry>E2</entry><entry>EVA</entry><entry>1005 VN2</entry><entry>0.40</entry><entry>0.928</entry><entry namest="col6" nameend="col7" align="left">102</entry></row><row><entry>E3</entry><entry>EVA</entry><entry>Dupont 3165</entry><entry>0.7</entry><entry>0.94</entry><entry namest="col6" nameend="col7" align="left">89</entry></row><row><entry /><entry /><entry /><entry /><entry /><entry namest="col6" nameend="col7" align="left" /></row><row><entry>S1</entry><entry>SB COPOLYMER</entry><entry>DK13</entry><entry>10</entry><entry>1.01</entry><entry namest="col6" nameend="col7" align="left" /></row><row><entry>M1</entry><entry>EMA copolymer</entry><entry>ARKEMA LOTRYL 29MAO3</entry><entry>2-3,5</entry><entry>0,95</entry><entry>61</entry><entry /></row><row><entry>B1</entry><entry>Ethylene alpha olefin copolymer</entry><entry>TAFMER 1085</entry><entry>1.2</entry><entry>0.885</entry><entry>68</entry><entry /></row><row><entry>B2</entry><entry>Ethylene alpha olefin copolymer</entry><entry>TAFMER P0480</entry><entry>1.8(230C, 2.16KG)</entry><entry>0.87</entry><entry /><entry /></row></tbody></tgroup></table></tables><tables id="tabl0009" num="0009"><table frame="all"><title>TABLE 2</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="12mm" /><colspec colnum="2" colname="col2" colwidth="48mm" /><colspec colnum="3" colname="col3" colwidth="50mm" /><colspec colnum="4" colname="col4" colwidth="25mm" /><colspec colnum="5" colname="col5" colwidth="32mm" /><thead><row><entry valign="top">Type</entry><entry valign="top">Description</entry><entry valign="top">Melt Index g/10 min 230c, 2.16kg</entry><entry valign="top">Density g/cm³</entry><entry valign="top">Vicat softening point</entry></row></thead><tbody><row><entry /><entry /><entry /><entry /><entry /></row><row><entry>PP1</entry><entry>PP copolymer</entry><entry>2</entry><entry>0.89</entry><entry>97</entry></row><row><entry>PP2</entry><entry>RB707CF</entry><entry>1.5</entry><entry>0.905</entry><entry>125</entry></row><row><entry>PP3</entry><entry>PP ethylene alpha olefin copolymer</entry><entry>7</entry><entry>0.89</entry><entry>91</entry></row><row><entry>PP4</entry><entry>Reactor made TPO</entry><entry>2</entry><entry>0.89</entry><entry /></row><row><entry>PP5</entry><entry>PP homopolymer</entry><entry>8</entry><entry>0.905</entry><entry>152</entry></row><row><entry>PP6</entry><entry>PP copolymer</entry><entry>2</entry><entry>0.89</entry><entry>65</entry></row></tbody></tgroup></table></tables><tables id="tabl0010" num="0010"><table frame="all"><title>TABLE 3</title><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="23mm" /><colspec colnum="2" colname="col2" colwidth="14mm" /><colspec colnum="3" colname="col3" colwidth="16mm" /><colspec colnum="4" colname="col4" colwidth="47mm" /><thead><row><entry align="center" valign="top" /><entry align="center" valign="top">HAZE</entry><entry align="center" valign="top">GLOSS</entry><entry align="center" valign="top">SHRINKAGE(MD/TD) at 90°C</entry></row></thead><tbody><row><entry align="center">Example 1</entry><entry align="center">6</entry><entry align="center">102</entry><entry align="center">42/42</entry></row><row><entry align="center">Example 2</entry><entry align="center">7</entry><entry align="center">101</entry><entry align="center">38/37</entry></row><row><entry align="center">Example 3</entry><entry align="center">7</entry><entry align="center">99</entry><entry align="center">41/41</entry></row><row><entry align="center">Example 4</entry><entry align="center">10</entry><entry align="center">82</entry><entry align="center">41/41</entry></row><row><entry align="center">Example 5</entry><entry align="center">11</entry><entry align="center">78</entry><entry align="center">40/41</entry></row><row><entry align="center">Example 6</entry><entry align="center">11</entry><entry align="center">77</entry><entry align="center">41/43</entry></row><row><entry align="center">Example 7</entry><entry align="center">13</entry><entry align="center">75</entry><entry align="center">30/31</entry></row><row><entry align="center">Comparison</entry><entry align="center">8</entry><entry align="center">90</entry><entry align="center">49/45</entry></row></tbody></tgroup></table></tables>

0060For better evaluation of the resistance of the sealing properties under cook-in conditions, the following experiment was executed.

0061Material from samples 1-7 and from the comparative sample were made into bag configuration in a pouch making machine. Then the bags were filled with water and sealed at the open end. Then the bags were put in a hot water bath and cooked at 95°C for 5 hours. After this thermal treatment, the bags were examined if their seals were destroyed and if delamination was noticed. <tables id="tabl0011" num="0011"><table frame="all"><title>TABLE 4 Results of cook-in test</title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="28mm" /><colspec colnum="2" colname="col2" colwidth="27mm" /><tbody><row><entry align="center" /><entry align="center" /></row><row><entry align="center">Example 1</entry><entry align="center">No bag opened</entry></row><row><entry align="center">Example 2</entry><entry align="center">No bag opened</entry></row><row><entry align="center">Example 3</entry><entry align="center">No bag opened</entry></row><row><entry align="center">Example 4</entry><entry align="center">No bag opened</entry></row><row><entry align="center">Example 5</entry><entry align="center">No bag opened</entry></row><row><entry align="center">Example 6</entry><entry align="center">No bag opened</entry></row><row><entry align="center">Example 7</entry><entry align="center">No bag opened</entry></row><row><entry align="center" /><entry align="center" /></row><row><entry align="center">Comparison</entry><entry align="center">All bags opened</entry></row></tbody></tgroup></table></tables>

0062Haze is measured according to ASTM D 1003, gloss according to BS 2782 and shrinkage according to ASTM 2732.