Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
2002-07-26
2003-11-18
Chen, Vivian (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S486000, C428S910000, C428S346000, C428S347000, C428S349000, C428S3550RA, C428S903300, C264S288400, C264S290200, C106S015050, C106S018110, C106S018140, C106S018180, C106S018310
Reexamination Certificate
active
06649247
ABSTRACT:
The invention relates to a sealable, flame-retardant, coextruded, biaxially oriented polyester film with one matt side, and composed of at least one base layer B and of, applied to the two sides of this base layer, a sealable outer layer A and a matt outer layer C. The film also comprises at least one flame retardant. The invention further relates to the use of the film and to a process for its production.
BACKGROUND OF THE INVENTION
GB-A 1 465 973 describes a coextruded, two-layer polyester film in which one layer is composed of isophthalic acid-containing and terephthalic acid-containing copolyesters and in which the other layer is composed of polyethylene terephthalate. The specification gives no useful information concerning the sealing performance of the film. Lack of pigmentation means that the process for producing the film is not reliable (the film cannot be wound) and that there are limitations on further processing of the film.
EP-A-0 035 835 describes a coextruded sealable polyester film which has particles admixed in the sealable layer to improve winding and processing performance, the median size of these particles exceeding the thickness of the sealable layer. The particulate additives form surface protrusions which prevent undesired blocking and sticking to rollers or guides. No further detail is given concerning incorporation of antiblocking agents in the other, non-sealable layer of the film. It is uncertain whether this layer comprises antiblocking agents. The sealing performance of the film is impaired by selecting particles with diameters greater than the sealing layer, and by selecting the concentrations given in the examples. The specification gives no information on the sealing temperature range of the film. Seal seam strength is measured at 140° C. and is in the range from 63 to 120 N/m (from 0.97 to 1.8 N/15 m of film width).
EP-A-0 432 886 describes a coextruded multilayer polyester film which has one surface on which a sealable layer has been arranged and a second surface on which an acrylate layer has been arranged. Here, too, the sealable outer layer may be composed of isophthalic acid-containing and terephthalic acid-containing copolyesters. The reverse-side coating gives the film improved processing performance. The specification gives no information concerning the sealing range of the film. Seal seam strength is measured at 140° C. For a sealing layer of thickness 11 &mgr;m the seal seam strength given is 761.5 N/m (11.4 N/15 mm). A disadvantage of the reverse-side acrylate coating is that this side is not then sealable with respect to the sealable outer layer. The uses of the film are therefore highly restricted.
EP-A-0 515 096 describes a coextruded, multilayer sealable polyester film which comprises an additional additive on the sealable layer. The additive may comprise inorganic particles, for example, and is preferably applied in an aqueous layer to the film during its production. The result is said to be that the film retains good sealing properties and processes well. The reverse side comprises only very few particles, which pass into this layer mainly via the regrind. Again, the specification gives no information concerning the sealing temperature range of the film. Seal seam strength is measured at 140° C. and is more than 200 N/m (3 N/15 mm). For a sealing layer of thickness 3 &mgr;m the seal seam strength given is 275 N/m (4.125 N/15 mm).
WO 98/06575 describes a coextruded multilayer polyester film which comprises a sealable outer layer and a non-sealable base layer. The base layer here may be composed of one or more layers, the interior layer being in contact with the sealable layer. The other (exterior) layer then forms the second non-sealable outer layer. Here, too, the sealable outer layer may be composed of isophthalic acid-containing and terephthalic acid-containing copolyesters, but no antiblocking particles are present in these. In addition, the film also comprises at least one UV absorber, which is added to the base layer in a weight ratio of from 0.1 to 10%. The base layer has conventional antiblocking agents. The film has good sealability, but does not have the desired processing performance and also has shortcomings in optical properties. The film may also have a matt surface, but then has high haze, which is undesirable.
DE-B 23 46 787 describes a flame-retardant raw material. Besides the raw material, its use to give films and fibers is also claimed. The following shortcomings were apparent during production of film using this claimed phospholane-modified raw material
the raw material mentioned is susceptible to hydrolysis and has to be very effectively predried. When the raw material is dried using prior art dryers it cakes, and production of a film is possible only under very difficult conditions,
the films produced, under uneconomic conditions, also embrittle at high temperatures, i.e. the mechanical properties decline sharply as a result of embrittlement, making the film unusable; this embrittlement arises after as little as 48 hours at high temperature.
It is an object of the present invention to eliminate the disadvantages of the prior art.
BRIEF DESCRIPTION OF THE INVENTION
The invention provides a sealable, flame-retardant, coextruded, biaxially oriented polyester film with one matt side and with at least one base layer B, and with a sealable outer layer A, and also with a matt outer layer C, where a flame retardant is present in at least one layer, where the sealable outer layer A has a minimum sealing temperature of 110° C. and a seal seam strength of at least 1.3 N/15 mm, and the topographies of the two outer layers A and C have the following features.
Sealable outer layer A:
R
a
<30 nm
Value measured for gas flow from 500 to 4000 s
Non-sealable, matt outer layer C:
200 nm<R
a
<1000 nm
Value measured for gas flow <50 s.
DETAILED DESCRIPTION OF THE INVENTION
The invention therefore provides a sealable, transparent, flame-retardant, sealable, coextruded and biaxially oriented polyester film with one matt side and not having the disadvantages of the prior art films mentioned and having in particular very good sealability, and capable of being produced cost-effectively, and which has improved processability, and improved optical properties. In particular, it is flame-retardant and does not embrittle after exposure to high temperature.
Success has been achieved in extending the sealing range of the film at low temperatures, increasing the seal seam strength of the film, and at the same time providing film handling which is better than that known from the prior art. It has moreover been ensured that the film can also be processed on high-speed processing machinery. During production of the film it is possible to introduce directly-arising regrind at a concentration of up to 60% by weight, based on the total weight of the film to the extrusion process without any significant resultant adverse effect on the physical properties of the film.
Flame retardancy means that in what is known as a fire protection test the transparent film meets the requirements of DIN 4102 Part 2 and in particular the requirements of DIN 4102 Part 1 and can be assigned to building materials classification B2 and in particular B1 for low-flammability materials.
The film is also intended to pass the UL 94 test “Vertical Burning Test for Flammability of Plastic Material”, thus permitting its classification in class 94 VTM-0. This means that the film has ceased to burn 10 seconds after removal of the Bunsen burner, and that after 30 seconds no smoldering is observed, and moreover no burning drops are observed.
Cost-effective production includes the capability of the raw materials or the raw material components needed to produce the flame-retardant film to be dried using industrial dryers of the prior art. It is significant that the raw materials do not cake and do not undergo thermal degradation. These industrial dryers of the prior art include vacuum dryers, fluidized-bed dryers, and fixed-bed dryers (tower dryers).
These dryers oper
Crass Guenther
Kern Ulrich
Mahl Hans
Murschall Ursula
Peiffer Herbert
Chen Vivian
Mitsubishi Polyester Film GmbH
ProPat L.L.C.
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