DE10214006A1 - Laminated composite film production, for use as barrier film especially in packaging foodstuffs, involves preheating solvent-free adhesive system, applying the adhesive to one film and laminating with the second film under cooling - Google Patents

Abstract

Production of laminated composite films, by adhering a first film to a second using a solvent-free adhesive system, involves: (i) preheating the adhesive system to the application temperature; (ii) applying the adhesive system to the first film (after mixing together preheated adhesive components if necessary); and (iii) combining the adhesive-coated film with a moving second film while cooling. An Independent claim is also included for composite films obtained by the process, where the adhesive system consists of a hydroxy-terminated polyester resin as adhesive component and an aliphatic diisocyanate as hardener component and (i) the composite film has a water vapor permeability of less than 2 (especially less than 1) g/(m<2> x d), (ii) at least one of the films to be combined is a metallized plastics film and/or (iii) the aromatic diisocyanate content in the hardener component is not more than 0.1 wt. %.

Description

The present invention relates to a method for producing composite films by means of a solvent-free adhesive system, in particular from Composite films with barrier properties and according to this process available composite films.

Depending on the goods to be packaged, packaging is used in the packaging industry materials with a wide variety of property profiles are required.

Depending on the goods to be packaged, it may be desirable that the used Packaging material for gases such as oxygen, nitrogen, Carbon dioxide and moisture is permeable, or reduced Permeability or impermeability.

Packaging materials with barrier properties should in particular the atmosphere contained or intended for the packaging, to Example nitrogen protective gas atmosphere, can preserve the quality guarantee the packaging goods even over a longer period can.

Such materials should also prevent the penetration of oxygen and / or Prevent moisture in the packaging that could spoil the goods.

Particularly high demands on the barrier properties of packaging materials are used particularly by the food industry and the like Industries.

In addition to the properties required for the respective application The packaging materials used should be as inexpensive as possible. This requires corresponding economic manufacturing processes.  

To increase the barrier properties of films, two or more Films glued together to form a composite film, being used as Glue an adhesive with barrier properties is used. So you can according to the invention 2-fold, 3-fold, 4-fold composite films and composite films with more than 4 slides can be obtained.

Adhesive systems used with preference are solvent-free, since in this case the energy-intensive, requiring additional work steps and thus there is no need for costly removal of solvents, as is usual solvent-based adhesive systems are available.

For example, EP 0 906 944 proposed a solvent-free adhesive system based on polyurethane for the production of composite films with To use barrier properties, a polyester resin with hydroxyl groups as the first adhesive component and a diisocyanate as the second hardener component includes. The polyester resin with hydroxyl groups is obtained by Reaction of a linear aliphatic diol with two to ten carbon atoms with a linear dicarboxylic acid, where n-butanediol and N-hexanediol as preferred diols and adipic acid are mentioned as preferred dicarboxylic acid. The polyester resin used is in crystalline form at room temperature and has a melting point of about 80 ° or less, being lower melting polyester resins are preferred. The number average of the Molecular weight of the polyester component is between 300 and 5000, preferably between 500 and 2000. The hydroxyl number of the Polyester resin component is preferred with about 20 to about 350 about 100 to about 250. Due to the low melting point of the The resin system can also use polyester resin at low temperatures are used, which are necessary to a deformation or other Exclude impairment of the polymer films due to high temperature.

The diisocyanate component used is aliphatic, preferably linear, but also called aromatic diisocyanates.  

According to the method described in EP 0 906 944, the two Components of the adhesive system are heated to the lamination temperature and immediately before the second film is laminated onto the first film wear. For complete curing of the composite film obtained recommended to store them for at least a week afterwards.

The films described in the working examples show good barriers properties related to oxygen permeability as well as in a case for the moisture permeability.

Because of the health and environmental concerns associated with the use of aromatic compounds, it is general desirable to add aromatic diisocyanates as adhesive components reduce or replace with aliphatic.

US 4,496,417 describes a laminating device for connecting a Plastic film with a paper reinforcement material. With this one described method, the adhesive is applied to both at the same time Plastic film as well as on the paper web during the lamination process applied, the laminating process can also take place with cooling. It was therefore an object of the present invention to produce a new process Provision of composite films, in particular composite films with a barrier properties, using a solvent-free adhesive system for Make available, aliphatic diisocyanates for the adhesive system can be used without any problems.

Furthermore, the method according to the invention makes it possible to shorten the night curing time of the finished composite films.

The object according to the invention is achieved by a method for producing composite films by gluing a first film to a second film using a solvent-free adhesive system, the adhesive system being preheated to the application temperature in a first stage,
in a second stage the preheated to the application temperature adhesive system, optionally after mixing individual adhesive system components, is applied to the first film, and
in a third stage, the first film coated with the adhesive system is connected to an incoming second film with cooling.

With the method according to the invention, adhesive systems can be used Basis of aliphatic, especially aliphatic linear, diisocyanates Composite films with excellent barrier properties easily and economically sustainably.

In addition, the curing time of the foils can be increased with this method shorten a few days.

The has proved to be a decisive factor for the method according to the invention Temperature logistics proved that in particular adequate preheating of the adhesive system or its components, the guarantee the application of the adhesive system to the first film for the one used Materials required application temperature and cooling the first film during the lamination of the second film.

The total amount of adhesive system that is applied to the first film should have a temperature that is as constant and uniform as possible. The individual adhesive components are therefore pre-selected over a period of time warms, which is sufficient for the total amount of compo used to ensure as uniform a temperature as possible.

The time required for this varies depending on the desired application temperature, The amount and type of material and is dependent on the above Set parameters routinely.

Thermal insulation of the line system with which the the individual adhesive system components to the application point in the  Laminating unit are to be provided to accommodate temperature fluctuations of the Avoid adhesive system.

Due to the accuracy and equality achieved by the above measures form of the application temperature, the accuracy of the viscosity of the Adhesive system guaranteed and thus a uniform quality of the Adhesive application. In addition, the risk of fog is prevented, that is, the Spraying of adhesive system applied to the film.

Glue the second film with the first one with the adhesive system NEN film, takes place according to the invention with cooling of the first film.

For the cooling, the laminating roller is preferably used, over which the first film running during connection, cooled.

The temperature at which the first film is cooled is around 15 ° C or more below the temperature at which the adhesive system at first Foil is applied. Preferably, a temperature difference of selected at least 20 ° and particularly preferably at least 25 °.

It is assumed that the exact setting of the adhesive application in com combination with the cooling of the first film during lamination properties, especially the barrier properties, of the composite film obtained significantly influence.

For the implementation of the method according to the invention, a conventional Lich laminating mill can be used.

The first film can be cooled by cooling the laminating roller itself over which the film runs during lamination with the second film. However, any other cooling device with the same effect can also be provided such as a cooling channel through which the first film runs.  

The web speed of the foils is used for the method according to the invention typically in a range from 200 to 300 m / min., preferably from 200 up to 250 m / min.

The amount of adhesive system applied depends on the type of film to be laminated and the type of adhesive system itself. The application quantity is usually between 1.5 to 4 g / m ² , preferably 2.0 to 3.0 g / m ² and in particular 2.5 to 2.7 g / m ² .

The web tension should be regulated to achieve good film quality so that there is an even pull on both of the two individual foils and is exerted on the laminated film composite. By this measure the overall product quality can be increased. In addition, the Adhesive quality and the winding of the film promoted.

In principle, any solvent-free can be used for the process according to the invention Adhesive system can be used.

Suitable examples of adhesive systems as preferred according to the invention are used, are described in the aforementioned EP 0 906 944 A2 ben.

These adhesive systems contain as an adhesive component a polyester resin with hydroxyl end groups, which is the reaction product of a linear aliphatic diol with 2 to 10 carbon atoms and a linear dicarboxylic acid. The polyester resin is crystalline at room temperature and has a melting point of about 80 ° C or less, with lower melting polyester resins being preferred. The number average molecular weight (M _n ) is from about 300 to about 5000 and the OH number is from about 20 to 350, with from about 100 to about 250 being preferred.

An aliphatic, preferably linear, or aromatic diisocyanate used.  

Examples of aliphatic diisocyanates as they are also suitable according to the invention Neter way can be used are polymeric hexamethylene diisocyanate nat and dicyclohexylmethane 4,4'-diisocyanate.

Examples of aromatic diisocyanates are methylene diphenyl diisocyanate and Toluene diisocyanate.

Preferred examples of polyester resins are the reaction products of C ₃ -C ₆ diols, in particular n-butanediol and n-hexanediol, with adipic acid, azelaic acid and sebacic acid, with adipic acid being preferred.

As already stated above, the Ver drive especially aliphatic hardener can be processed advantageously.

The use of aliphatic hardeners can be used in particular for composite films are intended for the food sector, due to the health and ecological harmlessness can be an advantage.

Adhesive layers obtained with aliphatic hardener components are also non-fading, in contrast to aromatic hardener components obtained adhesive layers do not yellow under the influence of light like daylight.

In addition, there are composite films by the inventive method with aliphatic hardeners have already been obtained after a post-curing time of about three days ready for further processing.

According to a preferred embodiment, for the present invention an aliphatic adhesive system used, which is a poly as an adhesive component contains ester resin, which from Rohm and Haas (formerly Morton) under the Description Mor-Free VP 130-01 is sold, and as hardener components polymeric hexamethylene diisocyanate, which is available from Rohm and Haas the designation Mor-Free VP 200 C is sold. The ratio of glue Component to hardener component can be used depending on the type of to be connected Films vary and will typically be according to the manufacturer's instructions selected.  

A suitable mixing ratio for the process according to the invention can in a range of preferably 100: 55 to 100: 70 (adhesive: hardener) to get voted.

The proportion of hardener can be increased as required without removing the barrier Properties of the composite films obtained are impaired.

For the process according to the invention, alipha can be used for the hardener component tables as well as aromatic diisocyanates are used.

Since the properties of the adhesive layer and thus the composite film also from the Type of the individual adhesive system components used, such as the used hardener components, can depend on the use of Such systems have certain properties of the obtained, as required Composite film can be modified.

The barrier layer can be created by using aromatic hardener components resistance of the composite film against moist gases can be improved.

Although the proportion of aromatic monomers in the hardener component is prin is subject to no restrictions, the proportion of aromatic Monomers in the hardener component are selected so that after the Hardening time of the composite film in the adhesive layer obtained no free aroma table diisocyanates are detectable. In other words, after curing the total amount of aromatic hardeners with the adhesive component have reacted.

In a preferred embodiment, the proportion of free aroma table monomers, based on the total proportion of hardener component selected a range of about 0.1%. It has been shown that in one Approx. 0.1% of aromatic monomer in the aromatic monomer composite film obtained is no longer detectable after only seven days.  

A suitable example of a hardener component that contains approx. 0.1% of aromati contains diisocyanates, are hardeners, such as those from Rohm and Haas sold under the name Mor-Free VP 413 A / S and Mor-Free VP 413 A. become.

The method according to the invention is suitable for laminating itself any materials known for the production of composite films, such as Plastic films, metallized plastic films with a thin metal coating, for example aluminum coating, or also for the lamination of Plastic films on paper.

Examples of plastic films are films made of polyolefins such as polyethylene and Polypropylene, polyester such as polyethylene terephythalate, polyamide such as PA6 and co-extruded films.

The number of films that make up the composite film is in principle subject to no particular limitation. The composite film can therefore two, three, four or contain more slides.

Through the combined use of the method according to the invention with a Adhesive system made of a polyester resin with hydroxyl end groups as an adhesive component and a diisocyanate as hardener component, as described above have been described, composite films with excellent Obtain barrier properties, for example with respect to oxygen transmission, moisture transmission and nitrogen and / or carbon dioxide Transmission.

Such films are also the subject of the invention. So with composite films with a barrier layer made of an adhesive system that the reaction product of a polyester resin with hydroxyl end groups as an adhesive component and an aliphatic or aromatic diisocyanant as a hardness component is water vapor permeability of less than 2, preferably less than 1.5 and in particular less can be obtained as 1 g / (m ² × d) with d = day.

In particular, water vapor permeabilities of less than 1 g / (m ² × d) and preferably less than 1.5 g / (m ² × d) could be obtained for composite films made of a metallized plastic film and a PE or PP film. Such composite films obtained according to the invention also show particularly low values for the oxygen permeability and nitrogen and carbon dioxide permeability.

In particular, it has been shown that particularly advantageous composite films metallized plastic films can be obtained, the obtained Composite foils for water vapor and the gases mentioned are almost impermeable are.

Surprisingly, it has been shown that water vapor in particular permeability of films coated with polyvinyl dichloride (PVDC) like them can be obtained commercially by using the invention according to the procedure for the lamination of another film considerably can be improved. The improvement also occurs when the further laminated film itself does not contribute to improving the Provides water vapor permeability. This is an advantageous effect Consequence of the method according to the invention and the one to be laminated on Slide independently.

According to the invention, a PVDC coated polyester film such as it is commercially available, such as a PVDC coated PET film with a thickness of 12 µm.

A preferred embodiment for the method according to the invention is explained below with reference to FIG. 1, which schematically shows a laminating device as can be used for the method according to the invention.

The adhesive system components preheated to the application temperature are mixed in a mixing tube 1, for example using the vortex method, and injected into a gap 9 between a pre-metering roller 2 and a metering roller 3 and applied to the first film A via an application roller 4 .

The lamination of the coated first film A with the second film B he preferably follows immediately after the adhesive application by the first film A is fed for cooling and simultaneous lamination over a cooled lamination roller 5 . By running the coated first film A over the cooled laminating roller 5 , the adhesive system applied to the first film A is subjected to immediate cooling, similar to a deterrent.

The cooling roller 5 is typically cooled to 15 ° C to 25 ° C.

The device shown is additionally provided with pressure rollers (called impression roller) 6 and 7 and a supporting pressure roller (called impression roller) 8 . The pressure roller 6 is applied above the application roller 4 and the pressure roller 7 provides the necessary pressure for the incoming second foil B to be laminated onto the coated first foil.

After laminating, the laminated film composite leaves the laminating roller 5 in the direction of the arrow shown in FIG. 1 and reaches a winding (not shown in the figure).

The composite film is preferably a second one before winding Subjected to cooling. For this purpose, the composite film can be placed on a second cooling roller (not shown). This second chill roll is also here typically cooled to 15 ° C to 25 ° C.

The individual components of the adhesive system, i.e. the adhesive component and the hardener component, before mixing and the Apply to the first film over a sufficiently long period of time Application temperature warmed to a homogeneous heating of the To achieve the amount of adhesive and the amount of hardener.

For this purpose, the individual components can be placed in heat containers the.  

The individual components of the adhesive are used to protect against atmospheric moisture systems here preferably under a protective gas atmosphere, such as nitrogen atmosphere, held.

If necessary, the films to be laminated can be laminated before laminating Corona treatment to increase wettability with glue improve in order to achieve an improvement in the bond adhesion.

Foil composites that have undergone corona pretreatment however, tend to have electrostatic attraction effects. Therefore, for users cases in which such side effects can disrupt one Corona pretreatment can be dispensed with.

According to a further preferred measure, the voltage that is applied to the individual foils A and B and on the film composite is exerted to agree otherwise, so that the same on the films or the film composite moderate tension is exerted. With this measure, the general increase my product quality and it can tension-free film composites be preserved.

By exercising an even tension, the winding will also be supports the film composite and get a uniform winding.  

The present invention is explained below on the basis of concrete examples illustrated.

Examples 1 to 9

In the following examples 1-6 some advantageous according to the invention Composite films and their barrier properties are described as they with the Process according to the invention can be obtained.

The foils were laminated with a Vario laminating machine coater LF, manufactured by Windmöller & Hölscher (W).

A polyester resin with hydroxyl end groups was used as the adhesive component Rohm and Haas with the product name Mor-Free VP 130-01 sets as well as the hardener component hexamethylene-1,6-diisocyanate, as it from the Rohm and Haas under the product name Mor-Free VP 200C is distributed.

The adhesive system components were placed in heat containers under nitrogenate pre-tempered to the application temperature of 60 ° C.

Here, the temperature control for an adhesive system quantity of 400 kg Performed 24 hours.

The supply lines for the adhesive components to the metering gap 9 between the front metering roller 2 and metering roller 3 were made via heated supply systems.

The order quantity was between approx. 2.6 to 3.0 g / m ² and the production speed was 200 m / min. The temperature of the laminating roller was set at 20 ° to 25 ° C.

Before the rewinder, a second cooling roller was provided, which was also a Temperature of 20 ° to 25 ° C.  

For Examples 7-9, a polyester resin was used as the adhesive component set by Rohm and Haas under the product name Mor- Free XVP PE 130-01 is distributed. Here, for Examples 7 and 9 used a hardener component with aromatic diisocyanate, just like them if by Rohm and Haas under the product name Mor-Free 413A is sold with a proportion of free toluene diisocyanate (TDI) from less than 0.1%.

For example 8, Mor-Free VP 200C with hexa was used as the hardener component methylene-1,6-diisocyanate from Rohm and Haas.

The application amount for Examples 7 and 9 was between 2.8-2.9 g / m ² and between 2.6-2.8 g / m ² and for Example 8 between 2.5-2.6 g / m ² ,

In the examples, PP means polypropylene, PE polyethylene, PA polyamide, PET Polyethylene terephthalate, LDPE low density polyethylene, LLDPE linear low density PE, met.PP or met.PET metallized PP or metallized PET, C (reproduced) a co-extruded film with a second thin layer Polyethylene, U (in front) an unoriented film and O (in front) one oriented film, and X (reproduced) a coating with PVDC (polyvinyl dichloride).

Carrying out the investigation of the barrier properties 1. Determination of water vapor permeability

The determination was made according to DIN 53 122, Part 2 (electrolysis method).

The test conditions were:
Climate D, (23 +/- 0.5) ° C and 85 +/- 2 (% relative humidity)
Partial pressure difference: 24 mbar.

The tests were carried out on both sides of the samples. The lower detection limit of the test method used is 0.05 g / (m ² × d) with d = day.

2. Determination of oxygen permeability

The determination was made according to DIN 53 380.

The test conditions were
for examples 1 to 6:
Dry gas
Temperature 23 ° C, and
for examples 7 to 9:
Relative gas humidity 50%
Temperature 23 ° C.

The tests were carried out on both sides of the samples. The lower detection limit of the test method used is 0.25 ml / (m ² × d × bar) with d = day.

3. Determination of nitrogen permeability

The determination was made according to DIN 53 380.

The test conditions were:
Dry gas
Temperature 23 ° C.

The tests were carried out on both sides of the samples. The lower detection limit of the test method used is 0.25 ml / (m ² × d × bar) with d = day.

4. Determination of carbon dioxide permeability

The determination was made according to DIN 53 380.

The test conditions were:
Dry gas
Temperature 23 ° C.

The examination was carried out on both sides of the samples. The lower detection limit of the test method used is 0.25 ml / (m ² × d × bar) with d = day.

The results are shown in Table 1.

Example 10

Analogous to the process described in Examples 1-9, composite films can can be obtained with the following structure. The abbreviations have the Above meaning.

Double composite films

OPP C 20 // white PE 30 to 100
PET 12 // met. OPP C 20

Triple laminated films

OPP 20 // met. OPP 15 to 20 // PE 30 to 100
PET 12 // met. OPP 15 to 20 // PE 30 to 100
PET 12 // met. PET 12 // PE 30 to 100
(Thickness in µm)

LIST OF REFERENCE NUMBERS

A first film (with adhesive application)
B second film (tapering)

1

mixing tube

2

Vordosierwalze

3

metering

4

applicator roll

5

Laminating roller (cooled)

6

.

7

Pressure roller (impression roller)

8th

Back-up roller (back-up press)

9

metering

Claims (16)

1. Process for the production of laminated composite films by gluing a first film with a second film by means of a solvent-free adhesive system,
characterized by
that in a first stage the adhesive system is preheated to the application temperature,
in a second stage, the adhesive components preheated to the application temperature are mixed with one another and applied to a first film and
in a third stage, the first film coated with the adhesive system is connected to an incoming second film with cooling. 2. The method according to claim 1, characterized, that the adhesive system as an adhesive component with a polyester resin Contains hydroxyl end groups and a diisocyanate as hardener component. 3. The method according to claim 2, characterized, that the hardener component is an aliphatic diisocyanate. 4. The method according to claim 2 or 3, characterized, that the hardener component does not exceed 0.1 percent by weight contains an aromatic diisocyanate. 5. The method according to any one of the preceding claims, characterized, that the composite film before winding up a second cooling is subjected.   6. The method according to any one of the preceding claims, characterized, that the difference between the application temperature of the adhesive system and cooling the coated first film at least 15 ° C is. 7. The method according to any one of the preceding claims, characterized, that the cooling by means of a Cooling roll takes place, which is at a temperature in a range from 15 ° to 25 ° C is set. 8. The method according to any one of the preceding claims, characterized, that the first and / or the second film before laminating one Undergo corona treatment. 9. The method according to any one of the preceding claims, characterized, that multiple composite films by gluing three or more films getting produced. 10. Composite film, obtainable by a process according to one of claims 1 to 9, using an adhesive system with a polyester resin with hydroxyl end groups as the adhesive component and an aliphatic diisocyanate as the hardener component, characterized in that the composite film has a water vapor permeability of less than 2, preferably less than 1, 5, and in particular less than 1 g (m ² × d) d = day. 11. Composite film, obtainable by a method according to one of the claims 1 to 9, using an adhesive system with a polyester resin with hydroxy end groups as an adhesive component and an aliphatic Diisocyanate as hardener component, characterized, that at least one of the interconnected foils has a metallic is plastic film. 12. The composite film according to claim 11, characterized in that the composite film has a water vapor permeability of less than 0.2 g (m ² × d), d = day. 13. Composite film obtainable by a method according to one of the claims 1 to 9, characterized, that the composite film has an adhesive layer that the reaction Product of a polyester resin with hydroxyl end groups as an adhesive component and a hardener component with aromatic Is diisosocyanate, the proportion of aromatic diisocyanate in the Hardener component does not exceed 0.1 percent by weight. 14. Composite film according to one of claims 10 to 13, characterized, that for the composite film has a film that with polyvinyl dichloride (PVDC) is coated. 15. composite film according to claim 14, characterized, that the film coated with PVDC is a polyester.   16. Composite films according to one of claims 9 to 15, characterized, that the composite film is a multiple composite film of three or more Films.