Cross-linkable Polymer Powder Premature Crosslinking
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Solution Overview
Problem
Existing methods for producing water-redispersible polymer powder compositions face challenges with premature crosslinking due to the presence of epoxy groups and amino hardeners in the aqueous dispersion, leading to instability and reduced efficiency during storage and application.
Innovation Solution
A crosslinkable, water-redispersible polymer powder composition is produced through radically initiated polymerization of specific monomers without epoxy-functional comonomers, with epoxy resin added before drying and a suitable hardener incorporated during drying to prevent premature crosslinking, ensuring stability and effective crosslinking upon redispersion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If epoxy resin and amino hardener are present together in the aqueous dispersion, then crosslinking capability is achieved, but premature crosslinking occurs during storage
Solution Approach 1:
The crosslinking system is segmented into two separate components: epoxy-functional comonomers incorporated into the polymer during emulsion polymerization, and amino hardeners added separately to the finished dispersion. This physical separation prevents premature crosslinking while maintaining crosslinking capability when the components are mixed in the final application.
Solution Approach 2:
The epoxy-functional groups are pre-incorporated into the polymer chains during emulsion polymerization, but the actual crosslinking reaction is postponed until the amino hardener is added to the finished dispersion. This preliminary preparation of one reactant without the other prevents premature reaction while ensuring readiness for crosslinking.
2Strength
If crosslinkable comonomers are copolymerized with vinyl monomers, then crosslinking efficiency is improved, but premature networking occurs during polymerization
Solution Approach 1:
Epoxy-functional comonomers are copolymerized with vinyl monomers to incorporate crosslinkable groups into the polymer chains, but the actual crosslinking is postponed until amino hardener is added later. This preliminary incorporation without immediate crosslinking prevents premature networking while ensuring crosslinking efficiency.
Solution Approach 2:
The epoxy-functional comonomers act as intermediaries that incorporate crosslinkable groups into the polymer structure during polymerization without causing immediate crosslinking. The actual crosslinking is mediated by the subsequent addition of amino hardener, which triggers the reaction at the appropriate time.
3Stability of the object's composition
If polymer particles are surrounded by protective colloid, then redispersibility is maintained, but crosslinking efficiency is reduced
Solution Approach 1:
Protective colloids are used during the drying process to prevent irreversible aggregation of polymer particles, and then removed or dissolved upon redispersion in water. This preliminary protection during drying maintains redispersibility while allowing efficient crosslinking when the particles are redispersed and the amino hardener is added.
Solution Approach 2:
The protective colloid is temporarily used during drying to prevent particle aggregation, then discarded (removed or dissolved) upon redispersion in water. This temporary protection enables both maintenance of redispersibility and achievement of crosslinking efficiency when the colloid is no longer present to interfere with the crosslinking reaction.
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 solution prevents premature crosslinking, maintains redispersibility, and achieves high mechanical strength in films, even without mineral binders, providing long-term stability and effective crosslinking in construction chemical products.
Implementation Method 1
emulsion polymerization... by radically initiated polymerization in an aqueous medium of one or more monomers
Implementation Method 2
epoxy resin... and a suitable hardener which crosslinks with the epoxy resin
Implementation Method 3
drying the corresponding aqueous polymer dispersions in the presence of a drying aid (generally a protective colloid)... the polymer particles are surrounded by the water-soluble protective colloid particles
Implementation Method 4
this protective colloid matrix, which dissolves again when the polymer powder is dispersed in water, causes the polymer particles to be present in the aqueous dispersion again with the particle size of the initial dispersion
Data Source
AI summary
The invention relates to a cross-linkable, in water redispersible polymer powder compound obtainable by means of radically initiated polymerization in an aqueous medium from one or more monomers from the group comprising vinylester from unbranched or branched alkylcarboxylic acids having 1 to 15 C-atoms, methacrylic esters and acrylic acid esters from alcohols having 1 to 15 C-atoms, vinyl aromatic compounds, olefins, dienes and vinyl halides, wherein no epoxide-functional comonomers are copolymerized, and subsequent drying of the polymer dispersion thus obtained, characterized in that before and/or during the polymerization and/or before the drying of the polymer dispersion thus obtained an epoxide resin is added and a hardener cross-linked to the epoxide resin is added after the drying as applicable.