Redispersible Polymer Powders Using Polyacrylamide Colloids
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Solution Overview
Problem
Current redispersible polymer powders face limitations with existing redispersing aids, such as polyvinyl alcohol and aryl sulfonic acid formaldehyde condensates, which suffer from issues like color retardation and unsatisfactory hydrophobicity, particularly at high dosage levels, and lack effective use of polyacrylamide as a protective colloid.
Innovation Solution
Incorporating a protective colloid system with 30% to 100% low molecular weight polyacrylamide colloid, having a 20% solution viscosity of 200 to 800 Centipoise, which acts as an excellent colloidal stabilizer and redispersing aid during emulsion polymerization of vinyl (meth)acrylic-based polymers, potentially replacing or complementing polyvinyl alcohol, and using persulfate initiators and chain transfer agents to control molecular weight and improve water solubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If polyvinyl alcohol or aryl sulfonic acid formaldehyde condensates are used as redispersing aids, then redispersibility is improved, but color retardation and unsatisfactory hydrophobicity occur at high dosage levels
Solution Approach 1:
The patent changes the chemical composition parameter of the redispersing aid by introducing polyacrylamide colloid with specific molecular weight (3,000 to 500,000) and acrylamide content (5-50%). This parameter change resolves the contradiction by achieving redispersibility without the color retardation and hydrophobicity issues associated with conventional redispersing aids at high dosages.
Solution Approach 2:
The patent creates a composite redispersing system by combining polyacrylamide colloid with the polymer matrix. This composite approach allows the polyacrylamide to provide redispersibility while its specific chemical structure prevents the harmful effects of color retardation and poor hydrophobicity that plague conventional single-component redispersing aids.
2Ease of operation
If conventional redispersing aids are used to prevent primary particle formation during spray drying, then redispersibility is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent employs polyacrylamide colloid as a cost-effective redispersing aid that can be used at optimized dosages (0.1-10% by weight). This approach replaces expensive conventional redispersing aids while maintaining effectiveness, thereby reducing manufacturing complexity and cost without sacrificing redispersibility.
Solution Approach 2:
By optimizing the molecular weight and acrylamide content parameters of the polyacrylamide colloid, the patent achieves effective redispersibility at lower dosages compared to conventional aids. This parameter optimization simplifies the manufacturing process and reduces the complexity associated with handling and dosing conventional redispersing aids.
3Strength
If high molecular weight redispersing aids are used, then coating effectiveness is improved, but water solubility and redispersability decrease
Solution Approach 1:
The patent precisely controls the molecular weight parameter of polyacrylamide colloid within the range of 3,000 to 500,000, with acrylamide content of 5-50%. This parameter optimization achieves the optimal balance where the colloid is sufficiently large to provide effective coating on polymer particles during spray drying, yet small enough to maintain excellent water solubility and redispersability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The low molecular weight polyacrylamide colloid enhances the redispersability, storage stability, and cost-effectiveness of redispersible polymer powders, providing improved film formation and water resistance, while minimizing primary particle formation and sticking during spray drying.
Implementation Method 1
a protective colloid system which includes from 30% to 100% of a low molecular weight polyacrylamide colloid
Implementation Method 2
Redispersing aids act to coat the individual polymer particles to prevent irreversible primary particle formation during drying operations
Implementation Method 3
a liquid dispersion of the polymer is subjected to a drying operation where the water is removed. The method may include, for example, spray drying
Data Source
AI summary
A redispersible polymer including, as a redispersing aid, a protective colloid system including from 30% to 100% of a low molecular weight polyacrylamide colloid having a 20% solution viscosity in water of 200 to 800 Centipoise.