Abstract:
The invention relates to a substrate coated with an oriented multilayer polymeric film comprising at least two layers of polymer particles oriented along two different directions with respect to one another. Such an oriented multilayer polymeric film has improved flexibility as well as improved gas barrier properties. A method of forming the film on a substrate is also disclosed.

Description:
BACKGROUND OF THE INVENTION 
     The present invention pertains to improvements in the field of oriented multilayer polymeric films. More particularly, the invention relates to a substrate coated with an oriented multilayer polymeric film having improved flexibility and improved gas barrier properties, as well as to a method of forming such a film on a substrate. 
     When considering gas barrier properties of an extruded polymeric film coated on a substrate, it is already known in the art that the diffusion coefficient of any penetrating gas such as oxygen, carbon dioxide or water vapor through the polymer film decreases by increasing the crystallinity of the film. This can be achieved by a chemical approach (molecular design) and appropriate cooling rate (chilling in the coating process). 
     In the case of a substrate coated with an oriented multilayer polymeric film formed from a water-based polymer dispersion and wherein the polymer particles of each layer are oriented in the same direction, it is also known that a three-layer film provides a stronger barrier to gas than a two-layer film having the same weight, which in turn is much more efficient than a one-layer film also having the same weight. Water-based polymer dispersions comprise very small polymer particles having an average size ranging from 150 to 200 mm and containing macro-molecules. When coated on a substrate and properly dried to remove the water, a continuous film is formed. 
     Whereas scientists are still studying and modeling oriented multilayer polymeric films formed from water-based polymer dispersions, they all agree that these films have a weak flexibility compared to that of extruded polymeric films. This weak flexibility renders waterborne barrier coatings in the packaging industry less attractive. The film flexibility is weak mainly when the film is folded about a fold line parallel to the direction of orientation of the polymer particles in each layer of the multilayer film, causing the film to break at the fold line. This of course impairs the gas barrier properties of the film. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to overcome the above drawbacks and to provide a substrate coated with an oriented multilayer polymeric film which is formed from a polymer dispersion and which has improved flexibility as well as improved gas barrier properties. 
     It is another object of the invention to provide a method of forming the above film on a substrate. 
     According to one aspect of the present invention, there is thus provided a substrate coated with an oriented multilayer polymeric film, wherein the film comprises at least two layers of polymer particles oriented along two different directions with respect to one another. 
     Applicant has found quite unexpectedly that the presence of at least two layers of polymer particles oriented along two different directions with respect to one another in a multilayer polymeric film improves the flexibility of such a film as well as the gas barrier properties thereof. 
     The present invention also provides, in another aspect thereof, a method of forming the above oriented multilayer polymeric film on a substrate. The method according to the invention comprises the steps of: 
     a) conveying a substrate along a predetermined path at a predetermined travelling speed and in a predetermined travelling direction; 
     b) coating the substrate with a polymer dispersion containing polymer particles and a liquid dispersing medium to form on the substrate a first coating of the dispersion; 
     c) contacting the first coating with a first particle orienting roller driven for rotation about a first longitudinal axis thereof independently of the substrate so as to have a first tangential speed at a surface of the coated substrate, the first particle orienting roller having a first particle orienting pattern arranged at a first angle relative to the travelling direction of the substrate to cause orientation of the polymer particles of the first coating along a first predetermined direction; 
     d) drying the first coating to cause evaporation of the liquid dispersing medium and formation of a first layer of oriented polymer particles on the substrate; and 
     e) successively forming on the first layer at least one further layer of oriented polymer particles, each further layer being formed by: 
     i) coating a previously formed underlying layer of oriented polymer particles with the polymer dispersion to form on the underlying layer a further coating of the dispersion; 
     ii) contacting the further coating with a further particle orienting roller driven for rotation about a further longitudinal axis thereof independently of the substrate so as to have a further tangential speed at the surface of the coated substrate, the further particle orienting roller having a further particle orienting pattern arranged at a further angle relative to the travelling direction of the substrate to cause orientation of the polymer particles of the further coating along a further predetermined direction; and 
     iii) drying the further coating to cause evaporation of the liquid dispersing medium and formation of the further layer of oriented polymer particles on the underlying layer; 
     wherein at least one further angle is different from the first angle or at least one further tangential speed is different from the first tangential speed, thereby forming on the substrate an oriented multilayer polymeric film having at least two layers of polymer particles oriented along two different directions with respect to one another. 
     The polymer particles are preferably particles of a waterborne polymer. Examples of suitable waterborne polymers which may be used include polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol and styrene-butadiene copolymers. The liquid dispersing medium can comprise, for example, water, an alcohol or a mixture thereof. 
     According to a preferred embodiment of the invention, the first particle orienting roller comprises a first cylindrical member rotatable about the aforesaid first longitudinal axis and a first continuous helical land on the first cylindrical member over at least a portion of the length thereof, the first helical land forming a first continuous helical particle orienting groove along the first cylindrical member. The first land and the first groove define the aforesaid first particle orienting pattern. The first helical land may be defined by a single wire helically and tightly wound about a major portion of the length of the first cylindrical member. 
     According to another preferred embodiment of the invention, two further layers of oriented polymer particles are formed in step (e) by: 
     i) coating the first layer of oriented polymer particles with the polymer dispersion to form on the first layer a second coating of the dispersion; 
     ii) contacting the second coating with a second particle orienting roller driven for rotation about a second longitudinal axis thereof independently of the substrate so as to have a second tangential speed at the surface of the coated substrate, the second particle orienting roller having a second particle orienting pattern arranged at a second angle relative to the travelling direction of the substrate to cause orientation of the polymer particles of the second coating along a second predetermined direction; 
     iii) drying the second coating to cause evaporation of the liquid dispersing medium and formation of a second layer of oriented polymer particles on the first layer; 
     iv) coating the second layer of oriented polymer particles with the polymer dispersion to form on the second layer a third coating of the dispersion; 
     v) contacting the third coating with a third particle orienting roller driven for rotation about a third longitudinal axis thereof independently of the substrate so as to have a third tangential speed at the surface of the coated substrate, the third particle orienting roller having a third particle orienting pattern arranged at a third angle relative to the travelling direction of the substrate to cause orientation of the polymer particles of the third coating along a third predetermined direction; and 
     vi) drying the third coating to cause evaporation of the liquid dispersing medium and formation of a third layer of oriented polymer particles on the second layer. 
     The second angle is different from the aforementioned first angle or the second tangential speed is different from the aforementioned first tangential speed, whereby the second predetermined direction is different from the aforementioned first predetermined direction. The third angle is different from the second angle or the third tangential speed is different from the second tangential speed, whereby the third predetermined direction is different from the second predetermined direction. 
     Preferably, the second particle orienting roller comprises a second cylindrical member rotatable about the aforesaid second longitudinal axis and a first plurality of juxtaposed continuous helical lands on the second cylindrical member over at least a portion of the length thereof, the helical lands of the first plurality having a similar pitch and forming a first series of helical particle orienting grooves along the second cylindrical member, the lands of the first plurality and the grooves of the first series defining the second particle orienting pattern. The third particle orienting roller, on the other hand, comprises a third cylindrical member rotatable about the aforesaid third longitudinal axis and a second plurality of juxtaposed continuous helical lands on the third cylindrical member over at least a portion of the length thereof, the helical lands of the second plurality having a similar pitch and forming a second series of helical particle orienting grooves along the third cylindrical member, the lands of the second plurality and the grooves of the second series defining the third particle orienting pattern. 
     The aforementioned particle orienting roller provided with a series of helical particle orienting grooves is novel and constitutes a further aspect of the invention. 
     The present invention therefore provides, in a further aspect thereof, a particle orienting roller for orienting polymer particles present in a polymer dispersion coated on a substrate. The particle orienting roller according to the invention comprises a cylindrical member rotatable about a longitudinal axis thereof and a plurality of juxtaposed continuous helical lands on the cylindrical member over at least a portion of the length thereof. The helical lands have a similar pitch and form a series of helical particle orienting grooves along the cylindrical member for imparting a predetermined orientation to the polymer particles when the cylindrical member is rotated while being in contact with the polymer dispersion. 
     According to a preferred embodiment, the helical lands are defined by a plurality of juxtaposed wires helically wound about the cylindrical member, the helical particle orienting grooves being each defined between adjacent wires. 
     According to another preferred embodiment, the helical lands are defined by a plurality of helical ribs integrally formed on a peripheral surface of the cylindrical member, the helical particle orienting grooves being each defined between adjacent ribs. 
     According to a further preferred embodiment, the helical particle orienting grooves are integrally defined in a peripheral surface of the cylindrical member. 
     A particularly preferred oriented multilayer polymeric film formed on a substrate in accordance with the invention is an oriented three-layer polymeric film having a first layer comprising polymer particles oriented along a first direction, a second layer disposed on the first layer and comprising polymer particles oriented along a second direction angled at about 45° relative to the first direction, and a third layer disposed on the second layer and comprising polymer particles oriented along a third direction parallel to the first direction. 
     As previously noted, the oriented multilayer polymeric film formed on a substrate in accordance with the present invention has improved flexibility and improved gas barrier properties. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further features and advantages of the invention will become more readily apparent from the following description of preferred embodiments as illustrated by way of examples in the accompanying drawings, in which: 
     FIG. 1 is a schematic view of an apparatus for carrying out a method of forming an oriented two-layer polymeric film on a substrate, according to a preferred embodiment of the invention; 
     FIG. 2 is a partial schematic bottom plan view of the apparatus shown in FIG. 1, illustrating the orientation of the polymer particles in the successive coatings applied onto the substrate; 
     FIG. 3 is a schematic view of an apparatus for carrying out a method of forming an oriented three-layer polymer film on a substrate, according to another preferred embodiment of the invention; 
     FIG. 4 is a partial schematic bottom plan view of the apparatus shown in FIG. 3, illustrating the orientation of the polymer particles in the successive coatings applied onto the substrate; 
     FIG. 5 is a partial side view of a conventional particle orienting roller which is used in the apparatuses shown in FIGS. 1 and 3; 
     FIG. 6 is a partial side view of another conventional particle orienting roller which may also be used in the apparatus shown in FIG. 1 or  3 ; 
     FIG. 7 is a part-sectional side view of a particle orienting roller according to a preferred embodiment of the invention, which is used in the apparatuses shown in FIGS. 1 and 3; 
     FIG. 8 is a side view of a particle orienting roller according to another preferred embodiment of the invention, which may also be used in the apparatus shown in FIG. 1 or  3 ; 
     FIG. 9 is a side view of a particle orienting roller according to a further preferred embodiment of the invention, which may also be used in the apparatus shown in FIG. 1 or  3 ; 
     FIG. 10 is a schematic top plan view illustrating how conventional particle orienting rollers may disposed in the travelling path of the substrate to form thereon an oriented three-layer polymeric film, according to a preferred embodiment of the invention; and 
     FIG. 11 is a view similar to FIG. 11, illustrating how the travelling direction of the substrate may be varied relative to the rotation axis of one of the conventional particle orienting rollers to form on the substrate an oriented three-layer polymeric film, according to another preferred embodiment of the invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring first to FIGS. 1 and 2, a continuous web  10  of paper is conveyed from a paper roll  12  through a first coating station  14 , a first particle orienting station  16 , a first drying station  18 , a second coating station  20 , a second particle orienting station  22  and a second drying station  24 , by guide rollers  26  and a take-up driving roller  28 . At the coating station  14 , a first coating roller  30 A partially immersed in a first bath  32 A of polymer dispersion containing polymer particles and water is used for coating the paper web  10  with the polymer dispersion so as to form on the paper web  10  a first coating  34 A of polymer dispersion. At the particle orienting station  16 , the first coating  34 A is contacted with a first particle orienting roller  36  which is driven for counterclockwise rotation about its longitudinal axis independently of the paper web  10  so as to have a tangential speed at the surface of the coated paper web  10 . The particle orienting roller  36  is driven by a suitable drive mechanism (not shown). It has a particle orienting pattern  38  arranged at an angle relative to the travelling direction  40  of the paper web  10  to cause orientation of the polymer particles of the first coating  34 A along a first predetermined direction. In the embodiment illustrated, the polymer particles  42 A of the first coating  34 A′ downstream of the roller  36  are oriented in a direction parallel to the travelling direction  40  of the paper web  10 ; in other words, they are oriented at an angle of 0°. The paper web  10  provided with the coating  34 A′ of oriented polymer particles  42 A is then passed through a first dryer  44 A to cause evaporation of the water present in the coating  34 A′ and formation of a first layer  46 A of oriented polymer particles  42 A on the paper web  10 . In FIG. 2, the broken line  48  represents the start of the first drying step. 
     At the second coating station  20 , a second coating roller  30 B partially immersed in a second bath  32 B of the polymer dispersion is used for coating the first layer  46 A with the polymer dispersion so as to form on the layer  46 A a second coating  34 B of polymer dispersion. At the second particle orienting station  22 , the second coating  34 B is contacted with a second particle orienting roller  50 A which is driven for counterclockwise rotation about its longitudinal axis independently of the paper web  10  so as to have a tangential speed at the surface of the coated paper web  10 . The particle orienting roller  50 A is driven by a suitable drive mechanism (not shown). The tangential speed of the particle orienting roller  50 A is the same as the tangential speed of the particle orienting roller  36 . The roller  50 A has a particle orienting pattern  52 A arranged at angle relative to the travelling direction  40  of the paper web  10  to cause orientation of the of the polymer particles of the second coating  34 B along a second predetermined direction. In the embodiment illustrated, the polymer particles  42 B of the second coating  34 B′ downstream of the roller  50 A are oriented in a direction angled at about 45° relative to the travelling direction  40  of the paper web  10 . The paper web  10  provided with the layer  46 A of oriented polymer particles  42 A, on which is disposed the coating  34 B′ of oriented polymer particle  42 B′ of oriented polymer particles  42 B, is then passed through a second dryer  44 B to cause evaporation of the water present in the coating  34 B′ and formation of a second layer  46 B of oriented polymer particles  42 B on the first layer  46 A of oriented polymer particles  42 A. In FIG. 2, the broken line  54  represents the start of the second drying step. 
     Thus, the apparatus shown in FIG. 1 enables one to form on the paper web  10  an oriented two-layer polymeric film having a first layer  46 A comprising polymer particles  42 A oriented along a predetermined direction (i.e. 0°), and a second layer  46 B disposed on the first layer  46 A and comprising polymer particles  42 B oriented along a direction angled at about 45° relative to the direction of orientation of the polymer particles  42 A. 
     The apparatus illustrated in FIG. 3 is similar to the one illustrated in FIG. 1, with the exception that a third coating station  56 , a third particle orienting station  58  and a third drying station  60  have been added in order to form on the second layer  46 B of oriented polymer particles  42 B a third layer of oriented polymer particles, As shown in FIGS. 3 and 4, at the coating station  56 , a third coating roller  30 C partially immersed in a third bath  32 C of the polymer dispersion is used for coating the second layer  46 B with the polymer dispersion so as to form on the layer  46 B a third coating  34 C of polymer dispersion. At the particle orienting station  58 , the third coating  34 C is contacted with a third particle orienting roller  50 B which is driven for clockwise rotation about its longitudinal axis independently of the paper web  10  so as to have a tangential speed at the surface of the coated paper web  10 . The particle orienting roller  50 B is driven by a suitable drive mechanism (not shown). It has a particle orienting pattern  52 B which is the same as the particle orienting pattern  52 A of the particle orienting roller  50 A. Since the roller  50 B has a negative tangential speed as opposed to the positive tangential speed of the roller  50 A, the particle orienting pattern  52 B of the roller  50 B imparts to the polymer particles of the third coating  34 C an orientation along a direction which is the mirror image of the direction of orientation of the polymer particles  42 B of the second layer  46 B Thus, in the embodiment illustrated, the polymer particles  42 C of the third coating  34 C′ downstream of the roller  50 B are oriented in a direction angled at about 45° relative to the travelling direction  40  of the paper web  10 , but at 90° relative to the direction of orientation of the polymer particles  42 B of the second layer  46 B. The paper web  10  provided with the layer  46 A of oriented polymer particles  42 A and the layer  46 B of oriented polymer particles  42 B, on which is disposed the coating  34 C′ of oriented polymer particles  42 C, is then passed through a third dryer  44 C to cause evaporation of the water present in the coating  34 C′ and formation of a third layer  46 C of oriented polymer particles  42 C on the second layer  46 B of oriented polymer particles  42 B. In FIG. 4, the broken line  62  represents the start of the third drying step. 
     It is of course possible to replace the particle orienting roller  50 B by the particle orienting roller  36  driven for counterclockwise rotation about its longitudinal axis. In this case, the direction of orientation of the polymer particles  42 C of the third layer  46 C would be the same as the direction of orientation of the polymer particles  42 A of the first layer  46 A. In other words, the polymer particles  42 C of the third layer  46 C would be oriented in a direction parallel to the travelling direction  40  of the paper web  10  (i.e. at 0°). 
     The particle orienting roller  36  used in the apparatuses shown in FIGS. 1 and 3 is a conventional particle orienting roller which is illustrated in more detail in FIG.  5 . As shown in FIG. 5, the roller  36  comprises a cylindrical member  64  and a single wire  66  helically and tightly wound about the cylindrical member  64  over a major portion of the length thereof. The single wire  66  forms a continuous helical groove  68  adapted to impart to the polymer particles an orientation in a direction at 90° relative to the longitudinal axis of the cylindrical member  64 . The single wire  66  defines a continuous helical land or ridge on the circumference of the cylindrical member  64 . Thus, the pitch of the particle orienting roller  36  is equal to a lead thereof, the lead being the distance a helical land or ridge advances axially in one turn of the particle orienting roller  36 . The land defined by the single wire  66  together with the groove  68  define the aforesaid particle orienting pattern  38 . 
     Instead of using the particle orienting roller  36 , it is possible to use the roller  36 ′ illustrated in FIG.  6 . As shown, the particle orienting roller  36 ′ comprises a cylindrical member  70  provided with a single helical groove  72  which is integrally defined in the peripheral surface of the cylindrical member  70  and extends along a major portion of the length thereof. The helical groove  72  is adapted to impart to the polymer particles an orientation in a direction at 90° relative to the longitudinal axis of the cylindrical member  70 . In this single helical groove  72 , the lead is equal to the pitch of the particle orienting roller  36 ′. A single continuous helical land  73  is formed. 
     Each of the particle orienting rollers  50 A and  50 B is a particle orienting roller  50  according to a preferred embodiment of the invention, which is illustrated in FIG.  7 . As shown, the roller  50  comprises a cylindrical member  74  and a plurality of juxtaposed continuous helical lands defined by a plurality of juxtaposed wires  76  helically wound about the cylindrical member  74  over a major portion of the length thereof. The wires  76  are wound so as to have the same pitch. A helical particle orienting groove  78  is defined between each pair of adjacent wires  76 . The lands defined by the wires  76  together with the grooves  78  define the aforesaid particle orienting pattern  52 A, 52 B. As opposed to the particle orienting rollers  36  and  36 ′ shown in FIGS. 5 and 6, respectively, the lead l of the particle orienting roller  50  is not equal to the pitch thereof, but rather to “n” times the pitch thereof, “n” being the number of wires  76  helically wound about the cylindrical member  74 . This enables the particle orienting grooves  78  to orient the polymer particles along a direction which is angled at about 5° to about 85° relative to the travelling direction  40  of the paper web  10 , depending on the pitch and the tangential speed of the roller  50 . 
     The pitch of the particle orienting roller  50  has a direct influence on the angle of the particle orienting pattern thereof. Therefore, by changing the pitch of the roller  50 , it becomes possible to change the direction of orientation of the polymer particles. Alternatively, this can be done by changing the relative orientation of the roller  50  with respect to the travelling direction  40  of the web  10 . Further directional changes can be imparted to the polymer particles by varying the tangential speed of the particle orienting roller  50 . The tangential speed can be varied by changing the angular speed of the roller or its diameter. The tangential speed can also be varied by changing the direction of rotation of the roller  50 . As previously noted, a change in the direction of rotation of the roller  50  from a counterclockwise to a clockwise rotation may be seen as a change from a positive to a negative tangential speed. 
     Instead of using the particle orienting roller  50 , it is also possible to use the rollers  50 ′ and  50 ″ illustrated in FIGS. 8 and 9, respectively. As shown in FIG. 8, the particle orienting roller  50 ′ comprises a cylindrical member  80  and a plurality of juxtaposed continuous helical lands defined by a plurality of helical ribs  82  integrally formed on the peripheral surface of the cylindrical member  80  over a major portion of the length thereof. A helical particle orienting groove  84  is defined between each pair of adjacent ribs  82 . The helical grooves  84  are adapted to orient the polymer particles along a direction which is angled at about 5° to about 85° relative to the travelling direction  40  of the paper web  10 , depending on the pitch and the tangential speed of the roller  50 ′. The particle orienting roller  50 ″ illustrated in FIG. 9 comprises a cylindrical member  86  provided with a plurality of helical particle orienting grooves  88  which are integrally defined in the peripheral surface of the cylindrical member  86  and extend along a major portion of the length thereof. The helical grooves  88  are also adapted to orient the polymer particles along a direction which is angled at about 5° to about 85° relative to the travelling direction  40  of the paper web  10 , depending on the pitch and the tangential speed of the roller  50 ″. A plurality of juxtaposed continuous helical lands  89  are formed. In the embodiments illustrated in FIGS. 8 and 9, the particle orienting grooves  84  and  88  are similar to the particle orienting grooves  78  of the roller  50  shown in FIG.  7 . The lead l′ of the roller  50 ′ and the lead l″ of the roller  50 ″ are also the same as the lead l of the roller  50 . 
     In the embodiments illustrated in FIGS. 1-4, the rotation axes of the rollers  36 ,  50 A and  50 B are all at right angle relative to the travelling direction  40  of the paper web  10 . It is possible to achieve the same results without using the particle orienting rollers  50 A and  50 B, by replacing these rollers with the particle orienting rollers  36  and inclining one of the rollers  36  relative to the travelling direction  40  of the paper web  10 . This is schematically illustrated in FIG.  10 . As shown, three particle orienting rollers  36 A,  36 B and  36 C are used, the rollers  36 A and  36 C being disposed so that their rotation axis extends at right angle relative to the travelling direction  40  of the paper web  10 . The roller  36 B, however, is disposed so that its rotation axis extends at a tilt angle of about 45° relative to the travelling direction  40  of the paper web  10 . As a result of such an inclination, the particle orienting groove  68  (shown in FIG. 5) of the roller  36 B imparts to the polymer particles an orientation which is angled at about 45° relative to the travelling direction  40  of the paper web  10 . Thus, the oriented three-layer film formed as a result of the disposition of the rollers  36 A,  36 B and  36 C comprises a first layer of polymer particles oriented along a direction parallel to the travelling direction  40  of the paper web, a second layer of polymer particles oriented along a direction angled at about 45° relative to the direction  40 , and a third layer of polymer particles oriented along a direction parallel to the direction  40 . Although the particle orienting roller  36 B is shown in FIG. 10 as being inclined at about 45° relative to the travelling direction  40  of the paper web  10 , it is possible to dispose the roller  36 B so that its rotation axis extends at a tilt angle ranging from about 5° to about 85° relative to the direction  40 . 
     The same result as that obtained with the embodiment shown in FIG. 10 can also be achieved by disposing the particle orienting roller  36 B so that its rotation axis is parallel to the rotation axis of the particle orienting roller  36 A and by varying the travelling direction of the paper web  10 , prior to the second coating of polymer dispersion being contacted by the roller  36 B, so that it is angled at the aforesaid tilt angle relative to the rotation axis of the roller  36 B. This is schematically illustrated in FIG.  11 . As shown, by using appropriate guide rollers  90 , one may vary the travelling direction of the paper web  10  upstream of the roller  36 B so that the travelling direction  40 ′ is angled at about 45° relative to the rotation axis of the roller  36 B. 
     The following non-limiting example further illustrates the invention. 
     EXAMPLE 
     An oriented three-layer polymeric film A was formed on a paperboard, by the method described above. The film A comprised a first layer of polymer particles oriented along a direction parallel to the travelling direction of the paperboard (i.e. 0°), a second layer of polymer particles oriented along a direction angled at 45° relative to the travelling direction of the paperboard (i.e. 45°), and a third layer of polymer particles oriented along a direction parallel to the travelling direction of the paperboard (i.e. 0°). The moisture vapor transmission rate (MVTR) of such a film was measured at 37.8° C. and 100% relative humidity and compared with the MVTR of an oriented three-layer polymeric film B formed on the same type of paperboard by replacing the particle orienting rollers  50 A and  50 B in the apparatus of FIG. 3 with the particle orienting rollers  36  shown in FIG.  5 . The film B comprised three layers of polymers particles all oriented along a direction parallel to the travelling direction of the paperboard (i.e. 0°, 0°, 0°). The results are as follows: 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 Film A 
                   
                 Film B 
                   
               
               
                   
                 (0°, 45°, 0°) 
                   
                 (0°, 0°, 0°) 
               
             
          
           
               
                   
                 Film Weight 
                 MVTR 
                 Film Weight 
                 MVTR 
               
               
                   
                 (g/m 2 ) 
                 (g/m 2 /day) 
                 (g/m 2 ) 
                 (g/m 2 /day) 
               
               
                   
                   
               
               
                   
                 17 
                 2 
                 17 
                 4 
               
               
                   
                   
               
             
          
         
       
     
     As it is apparent, the film A has better moisture vapor barrier an the film B.