Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
2002-06-19
2004-06-15
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C156S069000, C156S272800, C156S305000, C156S308400, C428S319700, C428S319900, C428S329000, C428S332000, C428S336000, C428S516000, C428S910000
Reexamination Certificate
active
06749933
ABSTRACT:
The invention relates to packaging made of a biaxially oriented polyolefin film.
Polyolefin films are widely used as packaging films. The success of these materials is based on the good optical and mechanical properties and on the simple weldability of the films. Besides welding, heat-sealing of films has increased in importance. Heat-sealable films have an outer layer of a polymer which has a lower crystallite melting point than the polymer of the base layer. For heat-sealing, the film layers are laid one on top of the other and warmed to only from 10 to 20° C. below the crystallite melting point, i.e. the outer layers are not completely melted. The adhesion of the heat-sealing layers which is achieved is significantly less than in the case of welding of the same material, but is sufficient for many applications (Kunststoff-Handbuch [Plastics Handbook], Volume IV, Carl Hanser Verlag, Munich, 1969, pages 623 to 640).
Besides the use of heat-sealable layers, the application of so-called cold-sealing layers is known. Cold-sealing layers are used, in particular, where heat-sensitive package contents, such as, for example, chocolate, are packaged in film. The application of cold-sealing layers is an additional processing step which considerably increases the costs for a package.
Independently of these packaging technologies, such as welding, heat-sealing or cold-sealing, processes for marking polymeric materials have been developed in recent years. Materials of this type contain a radiation-sensitive additive which causes a colour change in the material on exposure to radiation in certain wavelength ranges. Suitable additives for this application are, for example, laser pigments.
In addition, the prior art discloses processes for joining plastic components by means of lasers, in which the thermal and mechanical load on the components is low. For many applications, transmission laser welding has become established. In this method, the laser beam passes through a transparent component unhindered and hits the laser-absorbent join partner. The action of the laser beam causes the plastic of the absorbent partner to melt at the surface and join to the join partner on cooling. In this process, diode lasers or solid-state lasers having wavelengths in the near infrared region are employed.
The object of the present invention therefore consisted in providing packaging made of a polyolefin film which avoids the disadvantages of cold-sealing coating, but is equally suitable for the packaging of heat-sensitive products.
This object is achieved by packaging made of a multilayered, oriented polyolefin film which comprises a base layer and at least one first outer layer, where this first outer layer is in contact with itself or in contact with the opposite surface of the film or in contact with the surface of a further film, characterized in that the film comprises in this first outer layer an additive which has an absorption in the wavelength range of a laser such that, on local irradiation of the film with this laser, a temperature increase occurs in the area of the irradiation such that the polyolefin of the first outer layer softens or melts in the irradiated area and bonds to a further layer on cooling. The subclaims indicate further embodiments of the invention.
A further object of the present invention consisted in indicating advantageous packaging comprising a container with lid.
This object is achieved by packaging made of a multilayered, oriented polyolefin film which comprises a base layer and at least one first outer layer, where the polyolefin film comprises in the first outer layer an additive which has an absorption in the wavelength range of lasers such that, on local irradiation of the film with a laser, a temperature increase occurs in the area of the irradiation such that the polyolefin of the first outer layer softens or melts therein in the irradiated area and bonds to a further layer on cooling.
Besides the laser-absorbent pigment, the outer layer of the film generally comprises at least 80% by weight, preferably from 85 to <100% by weight, in particular from 90 to 98% by weight, in each case based on the layer, of a polyolefin.
Examples of suitable olefinic polymers of the outer layer are
propylene homopolymers
ethylene homopolymers
copolymers of
ethylene and propylene or
ethylene and 1-butylene or
propylene and 1-butylene or
terpolymers of
ethylene and propylene and 1-butylene or
a mixture or blend of two or more of the said homopolymers, co-polymers and terpolymers,
particular preference being given to
random ethylene-propylene copolymers having
an ethylene content of from 1 to 10% by weight, preferably from 2.5 to 8% by weight, or
random propylene-1-butylene copolymers having
a butylene content of from 2 to 25% by weight, preferably from 4 to 20% by weight,
in each case based on the total weight of the copolymer, or
random ethylene-propylene-1-butylene terpolymers having
an ethylene content of from 1 to 10% by weight, preferably from 2 to 6% by weight, and a 1-butylene content of from 2 to 20% by weight, preferably from 4 to 20% by weight, in each case based on the total weight of the terpolymer, or
a blend of an ethylene-propylene-1-butylene terpolymer and a propylene-1-butylene copolymer
having an ethylene content of from 0.1 to 7% by weight
and a propylene content of from 50 to 90% by weight
and a 1-butylene content of from 10 to 40% by weight,
in each case based on the total weight of the polymer blend.
The above-described copolymers and/or terpolymers employed in the outer layer generally have a melt flow index of from 1.5 to 30 g/10 min, preferably from 3 to 15 g/10 min. The melting point is in the range from 120 to 140° C. The above-described blend of copolymers and terpolymers has a melt flow index of from 5 to 9 g/10 min and a melting point of from 120 to 150° C. All the above-mentioned melt flow indices are measured at 230° C. and a force of 21.6 N (DIN 53 735).
The propylene homopolymers employed in the outer layer generally have a melt flow index of from 1.5 to 30 g/10 min, preferably from 3 to 15 g/10 min. The melting point of the homopolymers is in the range from 150 to 170° C., preferably from 155 to 165° C. Preference is given to isotactic homopolymers whose isotacticity is greater than 92%, preferably in the range from 94 to 98%. The n-heptane-soluble content of the isotactic propylene homopolymers is less than 10% by weight, preferably from 1 to 8% by weight, based on the weight of the homopolymer. All the above-mentioned melt flow indices are measured at 230° C. and a force of 21.6 N (DIN 53 735).
If desired, conventional additives, such as antistatics, neutralizers, lubricants and/or stabilizers, and, if desired, additionally antiblocking agents in effective amounts in each case may be added to the outer layer(s).
It is essential to the invention that the absorbent outer layer of the film comprises an additive which absorbs radiation in the wavelength range of lasers. Additives of this type are referred to below for the purposes of the present invention as pigments or laser pigments.
The incorporation of laser pigments of this type into the outer layer of the film results in absorption of the radiation, i.e. a take-up of energy, on irradiation of the film. It is known in the prior art that, given an appropriate wavelength, the laser beam leaves behind a visible track in the form of a white or coloured line in the pigmented plastic. This effect is utilized for marking plastic components and plastic films by means of a laser. As part of the present invention, it has now been found that irradiation of films laid one on top of the other by means of a laser beam produces a strong connection between the two film layers, in a similar manner to a heat-seal or weld seam, if at least one of the two films has a laser pigment-containing outer layer and this laser pigment-containing layer is facing the second films in such a way that the pigmented outer layer is in contact with the second film layer. It has been found here that it is particularly adv
Dries Thomas
Eiser Wolfgang
Nakarani D. S.
ProPat L.L.C.
Trespaphan GmbH
LandOfFree
Packaging material made of biaxially oriented polyolefin film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Packaging material made of biaxially oriented polyolefin film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Packaging material made of biaxially oriented polyolefin film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3344747