Methods of determining molecular weight and comonomer characteristics of a copolymer in polymer blends

Patent metadata

Field	Value
Publication number	US-10139378-B2
Application number	US-201715477359-A
Country	US
Kind code	B2
Filing date	Apr 3, 2017
Priority date	May 16, 2016
Publication date	Nov 27, 2018
Grant date	Nov 27, 2018

Abstract

A method for deconvoluting the molecular weight characteristics of the copolymer or rubber in an impact copolymer (ICP) comprising at least one copolymer or rubber and at least one homopolymer such as polypropylene, as well as a method of determining the comonomer characteristics of the rubber in an ICP, the methods comprising in part eluting a solubilized ICP through a gel permeation chromatographic (GPC) column to form an eluate comprising the rubber and/or polypropylene, measuring the Infrared (IR) absorption of at least the primary monomer-derived unit stretch frequency and the comonomer-derived unit in elution volume slices to determine the amount of comonomer, measuring the concentration of ICP using any detector, and determining the mass concentration, comonomer composition, and the total comonomer content of the ICP through the appropriate mathematical transformations.

First claim

The invention claimed is:

1. A method of determining the molecular weight characteristics of the copolymer component in an impact copolymer (ICP) comprising at least one copolymer (EP) and at least one homopolymer (PP), the method comprising:
a) eluting a solubilized ICP through a gel permeation chromatographic (GPC) column to form an eluate comprising the EP and/or PP;
b) measuring the Infrared (IR) absorption of at least the primary monomer-derived unit stretch frequency and the comonomer-derived unit in elution volume slices (Ve) to determine the amount of comonomer (S ICP ), and measuring the concentration of ICP (C ICP ) using any detector;
c) determining the mass concentration, comonomer composition at each Ve, and the total comonomer content (Tc 2 ) of the ICP; and
d) for each Ve, calculating the amount of EP and PP using the following equations:
c EP h EP +c PP h PP =c ICP h ICP
c EP h EP s EP +c PP h PP s PP =c ICP h ICP s ICP ,

wherein “c” is the concentration of ICP, EP and PP; “h” is the mass constant for EP, ICP, and PP; and “s” is the weight percent of comonomer for each of EP, ICP, and PP; and wherein:
(i) when the total EP content (T EP ) is known, S EP is equal to the Tc 2 /T EP , and/or
(ii) when the molecular weight characteristics of the PP is known, the value of S EP is chosen so that the C PP in each Ve has the same shape, and repeating the calculation until the C PP and the C′ PP only differs by a multiplication factor.

2. The method of claim 1 , wherein for each Ve the molecular weight (MW) is calculated by using the following equation:

log
⁢

⁢

M
X

=

log
⁡

(

K
ST

/

K
X

)

a
X

+
1

+

a
ST

+
1

a
X

+
1

⁢

⁢
log
⁢

⁢

M
ST

,

where “ST” refers to a standard polymer used to calibrate the GPC, and the values of a ST and K ST are known, and wherein the “X” values are the EP or PP where “K” and “a” values are known for each of these.

3. The method of claim 2 , wherein the values of K/a for PS are 0.000175/0.67, and wherein the “X” values are the EP or PP, and K/a values for PP are 0.000229/0.705 and for EP are calculated with the equations:
K= 0.000579(1−0.486 X p −0.069 X p 2 )/20000 Trunc(10X p )/1000 ,

a= 0.695+Trunc(10 X p )/1000, and
X P =1− s EP /100.

4. The method of claim 1 , wherein for step (i) the total rubber content (T EP ) is known and the S EP is calculated with equation:
s EP =Tc 2 /T EP ,
wherein the T C2 is obtained by equation:

T

C
⁢

⁢
2

=

∑
i

⁢

c
ICP
i

⁢

s
ICP
i

/

∑
i

⁢

c
ICP
i

.

5. The method of claim 1 , wherein for step (ii) a concentration profile (C′ PP ) for the PP portion of the ICP as a function of each Ve is obtained, and where a value of S EP is chosen and C PP calculated with equations (1) and the calculation is repeated until the C PP and the C′ PP only differs by a multiplication factor.

6. The method of claim 1 , wherein the PP and EP elute independently without interference with one another.

7. The method of claim 1 , wherein the S EP is constant across molecular weight of the EP.

8. The method of claim 1 , wherein the rubber is not physically separated from the polypropylene prior to elution.

9. The method of claim 1 , wherein the rubber is an ethylene-propylene copolymer having within the range from 5 wt % to 60 wt % ethylene-derived units by weight of the copolymer.

10. The method of claim 1 , wherein the polypropylene is a homopolymer, and S PP is zero, and wherein the “h” value for the ICP, EP, and PP are each equivalent, thus reducing the equations to equation:
c EP =c ICP s ICP /s EP and c PP =c ICP −c EP .

11. The method of claim 1 , wherein the ICP has a rubber content within the range from 10 wt % to 50 wt % by weight of the ICP.

12. A chromatographic system comprising at least a GPC column, and having detectors in which the output is captured by a computing system comprising code to convert the output into a concentration as a function of molecular weight by the method of claim 1 for at least the rubber component of the ICP.

13. A method of determining the molecular weight characteristics of the rubber in a polyolefin-based copolymer (ICP) comprising at least one rubber (EP) and at least one polypropylene (PP), the method comprising:
a) eluting a solubilized ICP through a gel permeation chromatographic (GPC) column to form an eluate comprising the EP and/or PP;
b) measuring

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Kang Shuhui

Classifications

• G01N30/74 Primary

  Optical detectors {(measurement of intensity, velocity, spectral content, polarisation, or phase of infrared, visible or ultraviolet light G01J)} · CPC title

• G01N2030/885

  involving polymers · CPC title

• G01N30/8675

  Evaluation, i.e. decoding of the signal into analytical information (for analysis of specific compounds see also G01N30/88 and subgroups of G01N33/00; chemical libraries per se C40B) · CPC title

• G01N33/442

  Resins; Plastics · CPC title

• G01N30/48

  Physics · mapped topic