阅读说明：本技术 用于热封的双轴定向聚丙烯膜 (Biaxially oriented polypropylene film for heat sealing ) 是由 樊玲 石洪涛 M·索利曼 覃杉 崔胜明 P·加尔格 J·C·J·F·塔克斯 于 2019-10-17 设计创作，主要内容包括：本发明涉及一种包括多个共挤出膜层的膜,所述膜具有长度和宽度以及厚度,所述厚度被定义为垂直于由所述长度和所述宽度界定的平面的所述膜的尺寸,其中所述膜是包括至少芯层A和一个或两个密封层B的双轴定向膜,所述芯层A具有第一表面和第二表面,其中所述芯层A包含聚丙烯,并且其中所述密封层B包含相对于所述密封层B的总重量计>50.0重量％的聚乙烯,所述聚乙烯包含衍生自乙烯的结构部分和衍生自包含4至10个碳原子的α-烯烃的结构部分,所述聚乙烯具有根据ASTM D1505(2010)测定的≥870且≤920kg/m～3的密度,其中所述密封层B直接粘附于所述芯层A的所述第一表面或第二表面中的一者。这种膜允许在降低的密封温度、也被称为密封起始温度下生产具有足够高密封强度的密封包装。(The present invention relates to a film comprising a plurality of coextruded film layers, said film having a length and a width and a thickness, said thickness being defined as the dimension of the film perpendicular to a plane defined by the length and the width, wherein the film is a biaxially oriented film comprising at least a core layer a and one or two sealing layers B, said core layer a having a first surface and a second surface, wherein the core layer a comprises polypropylene and wherein the sealing layers B comprise a polypropylene relative to the total weight of the sealing layers B>50.0 wt% of a polyethylene comprising moieties derived from ethylene and moieties derived from alpha-olefins comprising from 4 to 10 carbon atoms, the polyethylene having a composition according to ASTM D1505 (201)0) Measured more than or equal to 870 and less than or equal to 920kg/m 3 Wherein the sealing layer B is adhered directly to one of the first or second surfaces of the core layer a. Such films allow the production of sealed packages with sufficiently high seal strength at reduced sealing temperatures, also referred to as seal initiation temperatures.)

1. A film comprising a plurality of coextruded film layers, the film having a length and a width and a thickness, the thickness being defined as the dimension of the film perpendicular to a plane defined by the length and the width,

wherein the film is a biaxially oriented film comprising at least a core layer A and one or two sealant layers B, the core layer A having a first surface and a second surface,

wherein the core layer A comprises polypropylene, and

wherein the sealing layer B comprises a total weight of the sealing layer B>50.0 wt% of a polyethylene comprising moieties derived from ethylene and moieties derived from alpha-olefins comprising from 4 to 10 carbon atoms, the polyethylene having ≥ 870 and ≤ 920kg/m determined according to ASTM D1505(2010)³The density of (a) of (b),

wherein the sealing layer B is adhered directly to one of the first or second surfaces of the core layer A.

2. The film according to claim 1, wherein the sealing layer B further comprises <50.0 wt% of polypropylene relative to the total weight of the layer B.

3. The film of claim 2 wherein the polypropylene in layer B is a terpolymer of propylene with >1.0 and <10.0 wt% ethylene and >1.0 and <10.0 wt% of an additional olefin selected from 1-butene, 1-hexene and 1-octene, relative to the total weight of the polypropylene.

4. The film according to any one of claims 1 to 3, wherein the core layer A has a thickness of ≥ 60.0%, preferably ≥ 60.0% and ≤ 98.0% relative to the total thickness of the film.

5. The film according to any of claims 1-4, wherein the core layer A consists of a plurality of coextruded film layers, preferably a plurality of coextruded film layers each having the same material formulation, preferably three or five coextruded film layers.

6. The film according to claims 1-5, wherein the polypropylene in the core layer A is a propylene homopolymer, preferably a propylene homopolymer having a melt mass flow rate of ≥ 1.0 and ≤ 10.0g/10min, measured according to ISO 1133(2011) at 230 ℃, 2.16kg load.

7. The film of any of claims 1-5, wherein each of the one or more sealing layers B has a thickness ≧ 2.0% and ≦ 15.0% for the total thickness of the film.

8. The film of any one of claims 1-7, wherein the film is oriented to an extent of ≥ 5.0 in the length and width directions and ≥ 5.0 in the width direction of the film before undergoing biaxial orientation with respect to the film, wherein the extent of orientation is the ratio of either the length or the width after orientation versus before orientation.

9. The film of any one of claims 1-8, wherein the polyethylene has:

a fraction of material eluting in analytical temperature rising elution fractionation (a-TREF) at a temperature of 30.0 ℃ or less of 5.0 wt% or more, preferably 10.0 wt% or more, relative to the total weight of the polyethylene;

a shear storage modulus G ', G' and G "of >1000Pa measured at a shear loss modulus G" ═ 5000Pa, determined according to ISO 6721-10(2015) at 190 ℃; and

a chemical composition distribution Width (CCDB) of ≥ 15.0, preferably ≥ 20.0,

wherein said CCDB is determined according to formula I:

wherein

·T_n-2Is the moment calculated according to formula II:

and is

·T_z+2Is the moment calculated according to formula III:

wherein

W (i) is the fraction of the sample weight in wt% relative to the total sample weight in a-TREF analysis of sample (i) taken at temperature t (i), where t (i) >30 ℃, the area under the a-TREF curve is normalized to a surface area of 1 for t (i) >30 ℃; and is

T (i) is the temperature at which sample (i) is taken in the a-TREF analysis, in degrees C.

10. The film according to any one of claims 1-9, wherein the a-olefin is selected from the group consisting of 1-butene, 1-hexene and 1-octene, preferably 1-octene.

11. The film according to any one of claims 1-10, wherein each layer B comprises ≧ 60.0 wt.% of the polyethylene, relative to the total weight of each layer B.

12. A method of producing a biaxially oriented film according to any one of claims 1 to 11, said method comprising the steps in the following order:

(a) preparing a film via continuous melt extrusion;

(b) subjecting the membrane obtained in step (a) to an orientation in the machine direction to obtain a membrane having a degree of orientation in the length direction of ≧ 5.0, wherein the orientation in the machine direction occurs at a temperature in the range of 150-170 ℃, wherein the degree of orientation is the ratio of the length of the membrane after step (b) to the length of the membrane obtained in step (a);

(c) subjecting the film obtained in step (b) to an orientation in the transverse direction which occurs at a temperature of 150 ℃ and 170 ℃ to obtain a film having a degree of orientation in the width direction of ≧ 5.0, wherein the degree of orientation is the ratio of the width of the film after step (c) to the width of the film obtained in step (a).

13. The method of claim 12, wherein step (a) comprises co-extruding the core layer a and one or two sealing layers B.

14. The method of claim 13, wherein the co-extruding comprises extruding a core layer a comprising one or more layers, each layer being provided by a separate melt extruder, a first sealing layer B being provided on one side of the core layer a, and a second sealing layer B being provided on the other side of the core layer a, wherein each layer B is provided by a separate melt extruder, wherein each of the layers making up core layer a and each of the sealing layers B are in contact with each other in the molten state upon exiting the respective melt extruder to form a co-extruded multilayer film.

15. An article comprising a film according to any one of claims 1 to 11 or a film produced according to the method of any one of claims 12 to 14.