Polypropylene for films

Patent metadata

Field	Value
Publication number	US-2022056253-A1
Application number	US-201917279739-A
Country	US
Kind code	A1
Filing date	Sep 25, 2019
Priority date	Oct 10, 2018
Publication date	Feb 24, 2022
Grant date	—

Abstract

The present disclosure provides polypropylene compositions that have a high gloss and minimum or no haze while also having a high melt strength (e.g., high temperature resistance) and a relative high stiffness. Polypropylene compositions contain one or more base polypropylenes (e.g., trimmed polypropylenes (tPPs)) and one or more clarifying agents. The base or trimmed polypropylene contains at least 50 mol % of propylene and has a molecular weight distribution (Mw/Mn) in a range from 7 to 22, a z-average molecular weight of less than 2,500,000 g/mol, a branching index (g′vis) of at least 0.95, and a melt strength of less than 20 cN determined using an extensional rheometer at 190° C. The base or trimmed polypropylene can be produced from one or more high melt strength polypropylenes (HMS PPs).

First claim

1 . A polypropylene composition comprising:
a base polypropylene comprising at least 50 mol % propylene content and having:
a molecular weight distribution (Mw/Mn) from 7 to 22,
a z-average molecular weight of less than 2,500,000 g/mol,
a branching index (g′ vis ) of 0.95 or greater, and
a melt strength of less than 20 cN determined using an extensional rheometer at 190° C.; and
a clarifying agent.

2 . The polypropylene composition of claim 1 , wherein the base polypropylene comprises a trimmed polypropylene (tPP).

3 . The polypropylene composition of claim 1 , wherein the tPP is produced from a high melt strength polypropylene (HMS PP).

4 . The polypropylene composition according to claim 1 , comprising 50 ppm to 5,000 ppm of the clarifying agent.

5 . The polypropylene composition according to claim 1 , wherein the clarifying agent comprises a sorbitol, a benzoate, an organic phosphate, a norbornyl diacid, esters thereof, salts thereof, or any combination thereof.

6 . The polypropylene composition according to claim 1 , wherein the clarifying agent comprises 1,2,3-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol, esters thereof, or salts thereof.

7 . The polypropylene composition according claim 1 , wherein the polypropylene composition has a haze value of 50% or less, according to ASTM D1003.

8 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a haze value of 1% to less than 30%, according to ASTM D1003.

9 . The polypropylene composition of according to claim 1 , wherein the polypropylene composition has a gloss value in the machine direction of greater than 15, according to ASTM D2457.

10 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a gloss value in the machine direction of 20 to 70, according to ASTM D2457.

11 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a gloss value in the transverse direction of greater than 15, according to ASTM D2457.

12 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a gloss value in the transverse direction of 20 to 70, according to ASTM D2457.

13 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a gloss value at an angle of 20° of greater than 10, according to ASTM D523.

14 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a gloss value at an angle of 20° of 20 to 50, according to ASTM D523.

15 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a gloss value at an angle of 60° of greater than 20, according to ASTM D523.

16 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a gloss value at an angle of 60° of 30 to 100, according to ASTM D523.

17 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a gloss value at an angle of 85° of greater than 75, according to ASTM D523.

18 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a gloss value at an angle of 85° of 80 to 100, according to ASTM D523.

19 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a 1% secant flexural modulus in the machine or transverse direction of greater than 200,000 psi.

20 . The polypropylene composition according to claim 1 , wherein the polypropylene composition has a 1% secant flexural modulus in the machine or transverse direction of 215,000 psi to 270,000 psi.

21 . The polypropylene composition according to claim 1 , wherein the polypropylene composition is in the form of a blown film.

22 . The polypropylene composition according to claim 1 , wherein the melt strength (190° C.) of the base polypropylene is in a range from 1 cN to 15 cN.

23 .- 28 . (canceled)

29 . A method of forming a finished film comprising:
extruding a molten polypropylene composition comprising a base polypropylene and a clarifying agent through a die opening to form a film, wherein the base polypropylene comprises at least 50 mol % of propylene and has:
a molecular weight distribution (Mw/Mn) of from 7 to 22,
a z-average molecular weight of less than 2,500,000 g/mol,
a branching index (g′ vis ) of at least 0.95, and
a melt strength of less than 20 cN determined using an extensional rheometer at 190° C.; and
cooling the film at a distance away from the die opening to produce the finished film.

30 . A method of forming a finished film comprising:
trimming a high melt strength polypropylene (HMS PP) to produce a trimmed polypropylene (tPP); extruding a molten polypropylene composition comprising the tPP and a clarifying agent through a die opening to form a film, wherein the tPP comprises at least 50 mol % of propylene and has:
a molecular weight distribution (Mw/Mn) of from 7 to 22,
a z-average molecular weight of less than 2,500,000 g/mol,
a branching index (g′ vis ) of at least 0.95, and
a melt strength of less than 20 cN determined using an extensional rheometer at 190° C.; and
cooling the film at a distance away from the die opening to produce the finished film.

31 . The method of claim 29 , wherein cooling the film comprises blowing air on at least a portion of the film.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Schmitt Sasha P
• Spofford Caitlin A
• Pehlert George J

Classifications

• C08L2203/16

  used for films · CPC title

• C08J2323/10

  Homopolymers or copolymers of propene · CPC title

• C08J5/18

  Manufacture of films or sheets · CPC title

• C08K5/0083 Primary

  Nucleating agents promoting the crystallisation of the polymer matrix · CPC title

• B29C48/022

  characterised by the choice of material · CPC title