Reactive DOPO Flame Retardants for Low-Viscosity Polyester Resins
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Solution Overview
Problem
Existing flame retardants for polyester resins, such as halogen-free additives like DOPO, negatively affect the mechanical properties of the materials and are difficult to dissolve or mix, while halogenated compounds pose environmental and health risks.
Innovation Solution
Development of novel derivatives of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) with specific chemical structures that act as liquid, reactive flame retardants, integrating into the polyester resin backbone without deteriorating mechanical properties and reducing viscosity, allowing for reduced styrene content and lower filler loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If halogen-free flame retardants such as aluminum trihydrate, magnesium hydroxide, ammonium polyphosphate, or melamine polyphosphate are used, then environmental safety and health protection are improved, but the mechanical properties of polyester resins deteriorate and the substances are difficult to dissolve or mix into curable resins
Solution Approach 1:
The invention modifies the physical and chemical parameters of flame retardant compounds by creating DOPO derivatives with specific molecular structures (formula I) that have lower melting points and improved solubility. This allows the flame retardant to be effectively incorporated into polyester resins without requiring high filler loads, thereby maintaining mechanical properties while achieving flame retardancy.
Solution Approach 2:
The invention uses composite molecular structures combining DOPO core with various substituent groups (R1-R6) to create flame retardant compounds that integrate multiple functions: flame inhibition, resin compatibility, and mechanical property preservation. The composite structure allows the flame retardant to work synergistically with the polyester resin matrix.
2Object-affected harmful factors
If DOPO is used as a flame retardant in unsaturated polyester resins, then flame retardancy is achieved, but the mechanical properties of the materials deteriorate because DOPO acts as a radical scavenger preventing desired crosslinking
Solution Approach 1:
The invention extracts the problematic radical-scavenging property from the DOPO molecule by modifying its chemical structure. The derivatives (formula I) retain the flame-retardant phosphorus-containing core but have altered reactivity toward radicals, allowing crosslinking to proceed normally while maintaining flame inhibition capability.
Solution Approach 2:
The invention applies local quality modification by placing specific functional groups at different positions (R1-R6) of the DOPO molecule. This creates localized regions with different chemical properties: the phosphorus-containing core provides flame retardancy while the substituent groups control solubility, reactivity, and compatibility with the resin matrix.
3Object-affected harmful factors
If halogenated flame retardants such as aromatic polybrominated compounds are used, then flame retardancy is improved, but environmental concerns arise and hydrogen halides are formed during fire which are corrosive and harmful to health
Solution Approach 1:
The invention converts the historical approach of using halogenated compounds (which caused harm) into a beneficial halogen-free alternative. The DOPO derivatives provide equivalent or superior flame retardancy without generating harmful hydrogen halides, effectively using the lesson from halogenated compound drawbacks to create an improved solution.
4Object-affected harmful factors
If high-melting solid flame retardants are used, then flame retardancy is achieved, but the substances cannot be sufficiently dissolved or mixed into curable resins and often require combination with expandable graphite as synergists
Solution Approach 1:
The invention fundamentally changes the physical state parameter of flame retardants from solid to liquid by designing DOPO derivatives with lower melting points. The liquid state improves dissolution and mixing characteristics, allowing homogeneous incorporation into polyester resins without requiring additional synergists like expandable graphite.
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 new DOPO derivatives maintain mechanical properties, reduce resin viscosity, and enable effective flame retardancy with lower styrene content, offering environmental benefits and suitability for lightweight applications.
Implementation Method 1
DOPO can act as a radical scavenger, thus preventing the desired degree of crosslinking of the unsaturated polyester resins from being achieved
Implementation Method 2
wherein the compounds react with the chemical 'backbone' of the polyester resin without altering or deteriorating the mechanical properties of the polyester resin
Implementation Method 3
The viscosity of polyester resin formulations can be significantly reduced by adding the compounds according to the invention
Data Source
AI summary
The invention relates to a compound with the following chemical formula (I) and to a flame retardant comprising the compound according to the invention. Furthermore, the present invention relates to a polyester resin formulation comprising at least one unsaturated crosslinkable polyester resin and at least one flame retardant according to the invention. The present invention further relates to the use of the compound according to the invention as a flame retardant in an unsaturated crosslinkable polyester resin. Finally, the present invention relates to a process for preparing the compound according to the invention, wherein a compound of formula (III) described herein is reacted with a compound of formula (IV) described herein in the presence of a catalyst.