Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Reshaping running or indefinite-length work
Reexamination Certificate
2001-03-13
2004-04-13
Tentoni, Leo B. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Reshaping running or indefinite-length work
C264S290200
Reexamination Certificate
active
06719940
ABSTRACT:
The present invention relates to a white, biaxially oriented polyester film which comprises at least one layer comprising a polyester and a cycloolefin copolymer (COC). The invention also relates to a process for producing the polyester film, and also to the use of the film.
White, biaxially oriented polyester films are known from the prior art. These films known from the prior art are either easy to produce or have good optical properties or have acceptable processing performance.
DE-A 2 353 347 describes a process for producing a milky polyester film having one or more layers, which comprises preparing a mixture of particles of a linear polyester with from 3 to 27% by weight of a homopolymer or copolymer of ethylene or propylene, extruding the mixture as a film, quenching the film and biaxially orienting the same in directions running perpendicularly to one another, and heat-setting the film. A disadvantage of the process is that regenerated material produced during the production of the film (essentially a mixture of polyester and ethylene or propylene copolymer) cannot be reused without yellowing of the film. However, this makes the process uneconomic, and the film produced with regenerated material was not successful on the market. In addition, the film has roughness values which are significantly too high, giving it a very matt appearance (very low gloss) undesirable for many applications.
EP-A 0 300 060 describes a single-layer polyester film which comprises, besides polyethylene terephthalate, from 3 to 40% by weight of a crystalline propylene polymer and from 0.001 to 3% by weight of a surface-active substance. The effect of the surface-active substance is to increase the number of vacuoles in the film and at the same time to reduce their size to the extent desired. This achieves higher opacity and lower density of the film. A disadvantage of the film continues to be that regenerated material produced during the production of the film (essentially a mixture of polyester and propylene homopolymer) cannot be reused without yellowing of the film. However, this makes the process uneconomic, and the film produced with regenerated material was not successful on the market. In addition, the film has roughness values which are significantly too high, giving it a very matt appearance (very low gloss) undesirable for many applications.
EP-A 0 360 201 describes a polyester film having at least two layers, comprising a base layer with fine vacuoles, the density of which is from 0.4 to 1.3 kg/dm
3
, and at least one outer layer, the density of which is greater than 1.3 kg/dm
3
. The vacuoles are achieved by adding from 4 to 30% by weight of a crystalline propylene polymer, followed by biaxial stretching of the film. As a result of adding the outer layer the ease of production of the film is improved (no streaking on the film surface), the surface tension is increased and the roughness of the laminated surface can be reduced. A disadvantage still present is that regenerated material produced during the production of the film (essentially a mixture of polyester and propylene homopolymer) cannot be reused without yellowing of the film. However, this makes the process uneconomic, and the film produced with regenerated material was not successful on the market. In addition, the film listed in the examples continues to have excessive roughness values, giving it a matt appearance (low gloss) undesirable for many applications.
EP-A 0 795 399 describes a polyester film having at least two layers and comprising a base layer with fine vacuoles, the density of which is from 0.4 to 1.3 kg/dm
3
, and having at least one outer layer, the density of which is greater than 1.3 kg/dm
3
. The vacuoles are achieved by adding from 5 to 45% by weight of a thermoplastic polymer to the polyester in the base, followed by biaxial stretching of the film. The thermoplastic polymers used are, inter alia, polypropylene, polyethylene, polymethylpentene, polystyrene or polycarbonate, and the preferred thermoplastic polymer is polypropylene. As a result of adding the outer layer the ease of production of the film is improved (no streaking on the film surface), the surface tension is increased and the roughness of the laminated surface can be matched to prevailing requirements. Further modification of the film in the base layer and/or in the outer layers, using white pigments (generally TiO
2
) and/or using optical brighteners permits the properties of the film to be matched to the prevailing requirements of the application. A continuing disadvantage is that regenerated material produced during the production of the film (essentially a mixture of polyester and the added polymer) cannot be reused without undefined and undesirable changes in the color of the film. This makes the process uneconomic, and the film produced with regenerated material was not successful on the market. In addition, the films listed in the examples continue to have excessive roughness values, giving it a matt appearance (low gloss) undesirable for many applications.
DE-A 195 40 277 describes a polyester film having one or more layers, which comprises a base layer with fine vacuoles, the density of which is from 0.6 to 1.3 kg/dm
3
, and which has a planar birefringence of from −0.02 to 0.04. The vacuoles are achieved by adding from 3 to 40% by weight of a thermoplastic resin to the polyester in the base, followed by biaxial stretching of the film. The thermoplastic resins used are, inter alia, polypropylene, polyethylene, polymethylpentene, cyclic olefin polymers, polyacrylic resins, polystyrene or polycarbonate, and preferred polymers are polypropylene and polystyrene. Maintaining the stated limits for the birefringence of the film gives the claimed film in particular a superior tear strength and superior isotropic properties. A continuing disadvantage is that regenerated material produced during the production of the film cannot be reused without undefined and undesirable changes in the color of the film. This makes the process uneconomic, and the film produced with regenerated material was not successful on the market. In addition, the films listed in the examples continue to have excessive roughness values, giving it a matt appearance (low gloss) undesirable for many applications.
The object of the present invention was to provide a white, biaxially oriented polyester film which has high gloss, and in particular is easier to produce, i.e. has lower production costs. In particular it should be ensured that the regenerated material produced directly during the production process can be reused at a concentration of from 10 to 70% by weight, based on the total weight of the film, without any significant negative effect on the physical properties of the film. In particular, adding regenerated material should not give any significant yellowing of the film.
The object has been achieved by means of a white, biaxially oriented polyester film having at least a base layer, the characterizing features of which are that at least this base layer additionally comprises a cycloolefin copolymer (COC) at a concentration from 4 to 60% by weight, based on the base layer, where the glass transition temperature of the cycloolefin copolymer (COC) is in the range from 70 to 270° C.
For the purposes of the present invention, a white, biaxially oriented polyester film is a film of this type which has a whiteness above 70%, preferably above 75%, particularly preferably above 80%. The opacity of the novel film is moreover above 55%, preferably above 60% and particularly preferably above 65%.
To achieve the desired whiteness of the novel film the proportion of the cycloolefin copolymer (COC) in the base layer must be greater than 4%, otherwise the whiteness is below 70%. If, on the other hand, the cycloolefin copolymer (COC) content is greater than 60%, the production of the film becomes uneconomic, since the orientation process becomes unreliable.
It is also necessary for the glass transition temperature of the cycloolefin copolymer (COC) used to be above 70°
Mitsubishi Polyester Film LLC
Tentoni Leo B.
LandOfFree
White, biaxially oriented polyester film with cycloolefin... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with White, biaxially oriented polyester film with cycloolefin..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and White, biaxially oriented polyester film with cycloolefin... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3193235