US 11,945,201 B2
Cavity-containing polyester film and method for producing same
Shoji Deguchi, Tsuruga (JP); and Shunichiro Baba, Osaka (JP)
Assigned to TOYOBO CO., LTD., Osaka (JP)
Filed by TOYOBO CO., LTD., Osaka (JP)
Filed on Jun. 15, 2021, as Appl. No. 17/347,749.
Application 17/347,749 is a continuation of application No. 15/741,543, previously published as PCT/JP2016/069492, filed on Jun. 30, 2016.
Claims priority of application No. 2015-138738 (JP), filed on Jul. 10, 2015.
Prior Publication US 2021/0308982 A1, Oct. 7, 2021
Int. Cl. B32B 3/26 (2006.01); B29C 44/12 (2006.01); B29C 44/14 (2006.01); B29C 48/08 (2019.01); B29C 48/18 (2019.01); B29C 48/21 (2019.01); B29K 21/00 (2006.01); B32B 27/08 (2006.01); B32B 27/20 (2006.01); B32B 27/32 (2006.01); B32B 27/36 (2006.01); B32B 37/06 (2006.01)
CPC B32B 3/26 (2013.01) [B29C 44/1271 (2013.01); B29C 44/1285 (2013.01); B29C 44/14 (2013.01); B29C 48/18 (2019.02); B32B 27/08 (2013.01); B32B 27/205 (2013.01); B32B 27/32 (2013.01); B32B 27/36 (2013.01); B32B 37/06 (2013.01); B29C 48/08 (2019.02); B29C 48/21 (2019.02); B29K 2021/003 (2013.01); B32B 2250/03 (2013.01); B32B 2250/24 (2013.01); B32B 2250/40 (2013.01); B32B 2264/0257 (2013.01); B32B 2264/10 (2013.01); B32B 2264/102 (2013.01); B32B 2270/00 (2013.01); B32B 2272/00 (2013.01); B32B 2307/40 (2013.01); B32B 2307/4026 (2013.01); B32B 2307/41 (2013.01); B32B 2307/516 (2013.01); B32B 2307/518 (2013.01); B32B 2307/546 (2013.01); B32B 2307/718 (2013.01); B32B 2307/72 (2013.01); B32B 2323/10 (2013.01)] 18 Claims
 
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.