# US 5,707,870 A · Process for neutralizing acids in a solution of solvent and polymer

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- Number: US 5,707,870 A
- Document ID: US5707870A
- Status: Granted
- Kind: A
- Application number: 08/643,692
- Filed: 1996-05-06
- Granted: 1998-01-13
- Earliest claimed: 1994-09-01
- Assignees: E. I. Du Pont de Nemours and Company
- Inventors: Richard Crosby Moessner
- Web page: https://patentgrep.com/patent/US5707870A

## CPC

- G01N 21/359: using near infrared light
- G01N 21/3577: for analysing liquids, e.g. polluted water
- G01N 33/442: {Resins; Plastics}
- Y10T 436/12: Condition responsive control
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

A process for measuring and controlling at an aim point the neutralization of an organic acid in an organic polymer solution using a near-infrared analyzer.

## Claims

### Claim 1

A process for measuring and controlling the neutralization of an inorganic acid in an organic polymer solution at an aim point using a near-infrared analyzer and growth of absorbance due to the formation of water and increasing turbidity, said process comprising the steps of:
a) adding a base to a polymer solution having an inorganic acid to create a reacting solution;
b) obtaining multiple spectra;
c) averaging the measured values for the various wavelengths to generate an average spectra;
d) smoothing the averaged spectra one or more times using multi-point spectral smoothing;
e) applying a partial least squares regression model to the intensity of the spectra of the reacting solution for the absorbance region from about 1300 to 1610 nanometers to generate a a value for percent neutrality; and
f) comparing the percent neutrality value to the setpoint neutrality value and adjusting the amount of the base and solvent mixture added to the acidic polymer solution.

### Claim 2 (depends on 1)

The process of claim 1 wherein the organic polymer solution is an aromatic polymer solution of an aromatic polymer in an organic solvent.

### Claim 3 (depends on 2)

The process of claim 2 wherein the aromatic polyamide polymer is an aramid polymer.

### Claim 4 (depends on 2)

The process of claim 2 wherein the aromatic polyamide polymer is poly(meta-phenylene isophthalamide).

### Claim 5 (depends on 1)

The process of claim 1 wherein the organic solvent is diethyl acetamide.

### Claim 6

A process for measuring and controlling the neutralization of an inorganic acid in an organic polymer solution at an aim point using a near-infrared analyzer and growth of absorbance due to the formation of water and increasing turbidity, said process comprising the steps of:
a) adding a base to a polymer solution having an inorganic acid to create a reacting solution;
b) obtaining multiple spectra;
c) averaging the measured values for the various wavelengths to generate an average spectra;
d) smoothing the averaged spectra one or more times using multi-point spectral smoothing;
e) applying a partial least squares regression model to the intensity of the spectra of the reacting solution for the absorbance region from about 800 to 1200 nanometers to generate a a value for percent neutrality; and
f) comparing the percent neutrality value to the setpoint neutrality value and adjusting the amount of the base and solvent mixture added to the acidic polymer solution.

### Claim 7 (depends on 6)

The process of claim 6 wherein the organic polymer solution is an aromatic polymer solution of an aromatic polymer in an organic solvent.

### Claim 8 (depends on 7)

The process of claim 7 wherein the aromatic polyamide polymer is poly(meta-phenylene isophthalamide) and the organic solvent is dimethyl acetamide.

### Claim 9

A process for measuring and controlling the neutralization of an inorganic acid in an organic polymer solution at an aim point using a near-infrared analyzer and growth of absorbance due to the formation of water and increasing turbidity, said process comprising the steps of:
a) adding a base to a polymer solution having an inorganic acid to create a reacting solution;
b) obtaining multiple spectra;
c) averaging the measured values for the various wavelengths to generate an average spectra;
d) smoothing the averaged spectra one or more times using multi-point spectral smoothing;
e) applying a partial least squares regression model to the intensity of the spectra of the reacting solution for the absorbance region from about 1800 to 2200 nanometers to generate a a value for percent neutrality; and
f) comparing the percent neutrality value to the setpoint neutrality value and adjusting the amount of the base and solvent mixture added to the acidic polymer solution.

### Claim 10 (depends on 9)

The process of claim 9 wherein the organic polymer solution is an aromatic polymer solution of an aromatic polymer in an organic solvent.

### Claim 11 (depends on 10)

The process of claim 10 wherein the aromatic polyamide polymer is poly(meta-phenylene isophthalamide) and the organic solvent is dimethyl acetamide.