Optimizing pH Control for Consistent Pigment Quality

Yokogawa’s Process Liquid Analyzers series helps pigment producers achieve more reliable, accurate pH analysis in industrial bioprocesses, improving product quality while lowering total operation costs.

 

Introduction

Consistent product quality in pigment manufacturing depends on maintaining critical process conditions within the required operating range. Among these variables, pH and temperature can significantly affect pigment processing and the performance of the finished product.

Pigments are used across a wide range of products and industries, including paints, plastics, rubber, inks, textiles, construction materials, detergents, soaps, and other manufactured products. Because pigment formulations and manufacturing conditions vary, producers need dependable process measurements to maintain the conditions required for consistent production.

Accurate pH measurement is particularly important where pH-sensitive polymers and other process materials are involved. The manufacturer must maintain an appropriate pH range to support proper viscosity, rheology, process stability, and ultimately end-product quality.

Challenges

Maintaining the Correct pH

Small pH changes can affect the behavior of materials used in pigment and paint manufacturing. 

The desired pH range is 8.0 to 8.8, and the acrylic polymer used in the process becomes unstable below pH 7.5. Adding dispersions and thickeners can lower pH, potentially moving the process outside its preferred operating range.

Maintaining appropriate pH is therefore important to keep the mixture stable and achieve the desired product characteristics.

Controlling Viscosity and Rheology

pH also affects the polymers used to achieve the required viscosity and rheology.

The process uses pH-sensitive polymers that swell when the paint is maintained between approximately pH 8.0 and 9.5, making pH control critical to achieving the desired thickness and material characteristics. The process uses ammonia to help maintain pH within the acceptable range.

Managing Difficult Measurement Conditions

The pH measurement itself presents additional challenges:

• Process temperature can range from -5°C to +105°C, with a typical batch process temperature of approximately 95°C. 
• Scaling can occur on the electrode.
• Calibration may be required once per day because the customer observed approximately 1 pH unit of drift per day.
• The customer reported a typical sensor life of about 1.5 to 2 months.
• Chemical concentrations may be difficult for the customer to define.

These conditions make sensor selection, measurement reliability, maintainability, and chemical resistance important considerations.

Solution

Yokogawa recommended a process liquid analysis solution designed to provide reliable pH measurement while meeting the demanding conditions of pigment manufacturing.

FLEXA pH/ORP Analyzers

Two analyzer configurations are identified for the application:

2-wire FLEXA pH/ORP Analyzer

• Dual-sensor measurement
• Sensor wellness indication

4-wire FLXA402 pH/ORP Analyzer

• Connectivity for up to five sensors
• Color LCD display
• Touchscreen operation

These capabilities offer options for integrating pH measurement into the production process while giving operators greater visibility into the measurement system's condition. control.

pH Sensor and Immersion Fitting

For sensor selection, Yokogawa recommended a pH immersion fitting or equivalent with a PH8EFP sensor.

The sensor body uses Ryton, an engineering plastic, providing corrosion and heat resistance for a wide range of applications. Its integrated design simplifies calibration and maintenance, while individual components, including the pH glass electrode, platinum or gold ORP electrode, and junction, can be replaced separately.

When scaling, temperature variation, chemical exposure, calibration frequency, and sensor life create measurement challenges; selecting the right analyzer and sensor system helps establish a more dependable basis for process control.

Key Benefits

Improve Product Quality

More reliable, accurate pH analysis helps manufacturers maintain critical process conditions that affect end-product quality.

Improve Measurement Reliability

Sensor and analyzer selections address the chemical resistance, heat resistance, calibration, and maintenance requirements of challenging pH applications.

Simplify Sensor Maintenance

The recommended sensor design lets the operator replace key sensor components individually and simplifies calibration and maintenance.

Gain Greater Visibility into Sensor Condition

The 2-wire FLEXA analyzer provides sensor wellness indication, helping users monitor the measurement system.

Lower Total Operating Cost

The original application identifies more reliable and accurate pH analysis, improved end-product quality, and lower total operating cost as tangible benefits.