Cross-laminate of films and method of manufacturing
OwnerOle-Bendt Rasmusseninventor
Life of this patent
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Abstract
A cross-laminate web is formed of two oriented films, the films being arranged so that the main direction of orientation of the first film (A) generally follows the longitudinal direction (D) of the web and the main direction of the second film (B) is perpendicular (F) to that direction. The coefficient of elasticity of the material of the first film, in an unoriented state, is at least 115% lower than that of the material of the second film, and the heat shrinkability of the first film is greater than that of the second film. Bags formed from the cross-laminate have heat seals with improved shock peel strength.
Claims21
A cross-laminate in the form of an elongated web and consisting of two or more mutually bonded films or film assemblies, each of which is uniaxially oriented or unbalanced biaxially oriented, wherein said cross-laminate has on one of its sides a material A comprising either a) a film having a main direction of orientation generally corresponding to the longitudinal direction of the web, or b) an assembly of films having a resultant main direction of orientation generally corresponding to said longitudinal direction, and on the other side a material (B) comprising either a) a film having a main direction of orientation generally perpendicular to the longitudinal direction of the web, or b) an assembly of films having a resultant main direction of orientation generally perpendicular to the longitudinal direction of the web, and the coefficient of elasticity (E) of the material A in its unoriented state is at least 15% lower than the coefficient of elasticity of the material B in its unoriented state and wherein upon heating the cross laminate, materials A and B exhibit differential shrinkability along the said longitudinal direction, A being more shrinkable.
In a method of manufacturing a cross-laminate which comprises forming an elongated web made of a sandwich formed of different films, each exhibiting a main direction of orientation, and wherein these directions cross each other, subsequently further orienting the sandwiched films at a temperature below their melting range by stretching the same together in the longitudinal direction of the web, before or after this longitudinal stretching, also stretching the sandwiched films in the transverse direction of the web, this transverse stretching being carried out by passing the sandwiched films between grooved rollers, and bonding together the films in the sandwich to form a laminate before, during or after said longitudinal and transverse stretching operations, the improvement wherein said film sandwich consists of two materials (A′) and (B′), with material (A′) being situated on the one and material (B′) on the other side of the sandwich, material (A′) being either a) a film having a main direction of orientation generally corresponding to the longitudinal direction of the web, or b) an assembly of films having a resultant main direction of orientation generally corresponding to the said direction, and said orientation of material (A′) is stronger—as measured by shrink testing the materials (A′) and (B′) individually—than the orientation in material (B′) in the same direction, and material (B′) is either a) a film having a main direction of orientation generally perpendicular to the longitudinal direction of the web, or b) an assembly of films having a resultant main direction of orientation generally perpendicular to the longitudinal direction of the web, in which the coefficient of elasticity (E) of material (A′) in its unoriented state is at least 15% lower than the coefficient of elasticity of material (B′) in its unoriented state and said orientation of material (B′) is stronger—again measured for the materials individually—than the orientation in material (A′) in said perpendicular direction.
Dependencies are inferred from the claim text.