Patent ID: 11945201
Assignee: TOYOBO CO., LTD.
Field: Other special machines (Mechanical engineering)
Classification: CPC B | IPC B

Claim 0:
1. A cavity-containing polyester film, comprising:
a layer A which has therein cavities, and
layers B which each comprise a polyester resin containing inorganic particles and which are laminated, respectively, over both surfaces of the layer A;
the layer A comprises a composition comprising a polyester resin and an incompatible resin which is thermoplastic resin incompatible with the polyester resin;
a proportion of a polypropylene resin in a total amount of the incompatible resin in the layer A being 90% or more by weight;
a content of the polypropylene resin is 3-25% by weight of a total amount of the composition in layer A;
the polypropylene resin satisfying all of the following requirements (1) to (3):
(1) the polypropylene resin having a melt flow rate (MFR) ranging from 1.0 to 10 g/10-minutes (at a temperature of 230° C. under a load of 2.16 kg),
(2) the polypropylene resin showing a deflection temperature of 85° C. or higher under load (at a bending stress of 0.45 MPa), and
(3) the polypropylene resin having a weight-average molecular weight Mw ranging from 200000 to 330000, this weight-average molecular weight being measured by gel permeation chromatography (GPC), and having a molecular weight distribution ranging from 2 to 5, this molecular weight distribution being represented as the ratio of the weight-average molecular weight Mw to the number-average molecular weight Mn of the polypropylene resin (Mw/Mn),
the cavity-containing polyester film has an apparent density ranging from 0.8 to 1.2 g/cm3 and having a bending resistance of 10 mN·cm or more in each of the longitudinal direction and the lateral direction of the film,
the cavity-containing polyester film has an optical density (OD value) of 0.55 or more (in terms of a value when the film thickness is regarded as 50 μm), and
the layer A further comprises a waste material of the cavity-containing polyester film in a proportion of 5 to 60% by weight.