Cellulose Acetate Plasticizer Mixture Prevents Polycarbonate Migration
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Solution Overview
Problem
Cellulose acetate-based materials with traditional plasticizers, such as diethyl phthalate, experience migration issues when used in combination with polycarbonate, leading to opacity and cracking, and existing alternatives do not meet the specific requirements of the eyewear and jewelry industries in terms of mechanical properties, cost, and color stability.
Innovation Solution
A plastic material based on cellulose acetate with a mixture of citric acid esters, such as acetyl triethyl citrate, and organic phosphates, like triphenyl phosphate, in specific weight ratios (60-70% citrate and 30-40% phosphate), which prevents plasticizer migration and maintains mechanical and aesthetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If diethyl phthalate is used as a plasticiser in cellulose acetate, then the material becomes processable and flexible, but it migrates to polycarbonate components causing opacity and cracking
Solution Approach 1:
The patent changes the chemical parameters of the plasticiser by selecting specific esters with controlled molecular weight and functional groups. The chosen plasticisers (citrate esters, adipate esters, sebate esters, or phthalate esters with specific characteristics) have modified chemical structures that prevent migration while maintaining plasticising effectiveness, thus resolving the contradiction between processability and compatibility
Solution Approach 2:
The patent introduces a carefully selected plasticiser as an intermediary substance that mediates between cellulose acetate and polycarbonate. This intermediary plasticiser creates a compatible interface by having appropriate solubility parameters and molecular characteristics that prevent phase separation and migration, allowing both materials to coexist without adverse interactions
2Temperature
If citrates are used as plasticisers to achieve sufficient plasticisation, then the softening temperature decreases, but mechanical properties are impaired and unwanted colouring occurs
Solution Approach 1:
The patent modifies the parameters of citrate esters by selecting specific variants (such as acetyl tributyl citrate, acetyl triethyl citrate) with controlled molecular weights and acetylation degrees. These parameter adjustments allow achieving the necessary softening temperature reduction while preserving mechanical properties and avoiding unwanted colouring, thus resolving the contradiction
Solution Approach 2:
The patent creates a composite plasticising system by combining cellulose acetate with specifically selected citrate ester variants. This composite approach allows the plasticiser to effectively lower softening temperature while the controlled composition prevents excessive softening that would impair mechanical properties, and the selected esters maintain color stability
3Stability of the object's composition
If high purity citrates are used to avoid unwanted colouring, then color stability is improved, but costs increase
Solution Approach 1:
The patent changes the purity parameter requirements by selecting citrate ester variants (such as acetyl tributyl citrate, acetyl triethyl citrate) that inherently provide color stability at moderate purity levels. These specific esters have molecular structures that resist degradation and discoloration, allowing manufacturers to achieve color stability without requiring expensive high-purity grades, thus resolving the contradiction between color stability and manufacturing cost
Data Source
AI summary
The invention relates to a plastic material based on cellulose acetate, comprising at least one plasticiser, in which said plasticiser is comprised of the mixture of a first plasticiser comprised of citric acid esters and at least one second plasticiser selected from the group of organic phosphates, glycerol esters and trimellitic acid esters, the content of the first plasticiser being equal to or greater than the second plasticiser and the aforementioned mixture of plasticisers constituting overall 25-35% by weight of said plastic material.