Unsaturated Polyester Resin for Toner Fixing and Offset
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Solution Overview
Problem
Current polyester resins for toners lack a balance between low-temperature fixability, high-temperature offset resistance, wide fixing temperature range, and satisfactory storage stability and durability, with existing solutions either compromising on one or more of these properties.
Innovation Solution
A polyester resin with a peak molecular weight of at least 12,000 and containing unsaturated double bonds, combined with a crosslinking reaction to create a THF-soluble and THF-insoluble fraction, achieving a mass-average molecular weight/number-average molecular weight ratio of 6 or greater and a sum acid value and hydroxyl value of no greater than 40 mgKOH/g in the insoluble fraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If non-linear polyester resins with three-dimensional crosslinked structures are used, then high-temperature offset resistance is improved, but low-temperature fixability deteriorates
Solution Approach 1:
The patent segments the polyester resin structure into linear chains with unsaturated double bonds rather than using fully crosslinked three-dimensional networks. This segmentation allows the resin to maintain order at low temperatures for good fixability while forming sufficient crosslinks at high temperatures for offset resistance, resolving the contradiction between these two temperature-dependent properties
Solution Approach 2:
The patent changes the molecular structure parameter from saturated to unsaturated polyester resins, introducing double bonds that can undergo crosslinking reactions. This parameter change enables the resin to dynamically adjust its crosslinking density based on temperature conditions, achieving both low-temperature fixability and high-temperature offset resistance
2Temperature
If linear polyester resins are used, then low-temperature fixability is improved, but high-temperature offset resistance deteriorates
Solution Approach 1:
The patent incorporates unsaturated double bonds into the linear polyester resin structure during synthesis, preparing the resin in advance for crosslinking reactions. This preliminary action allows the resin to form crosslinks when needed (at high temperatures) while maintaining its linear structure at low temperatures for good fixability
Solution Approach 2:
The patent creates a composite structure within the polyester resin by combining linear chains with unsaturated double bonds that can form crosslinks. This composite approach integrates the low-temperature properties of linear resins with the high-temperature properties of crosslinked structures, resolving the contradiction between fixability and offset resistance
3Temperature
If unsaturated groups are introduced into linear polyester resins for crosslinking, then fixability is improved, but storage stability deteriorates due to peroxide residue
Solution Approach 1:
The patent extracts or removes the harmful peroxide residue from the crosslinking system by using alternative crosslinking mechanisms that do not require peroxide initiators. This allows the unsaturated groups to undergo crosslinking for improved fixability while eliminating the storage stability issue caused by peroxide decomposition products
Solution Approach 2:
The patent converts the potential harm of peroxide residue into a benefit by using unsaturated double bonds that can be crosslinked without requiring peroxide initiators. The double bonds themselves serve as the crosslinking sites, eliminating the need for harmful peroxide additives while maintaining the desired crosslinking functionality for improved fixability
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 provides toners with sufficient fixing strength at low temperatures, excellent high-temperature offset resistance, a broad fixing temperature range, and improved storage stability and durability.
Implementation Method 1
crosslinking reaction of polyester resin for toner (1) with a peak molecular weight of at least 12,000 in gel permeation chromatography and containing an unsaturated double bond
Implementation Method 2
a peak molecular weight of at least 12,000 in gel permeation chromatography
Data Source
AI summary
Disclosed is a toner which is excellent in low-temperature fixability, high-temperature offset resistance, storage stability and durability, while having a wide range of fixing temperature. Also disclosed is a polyester resin used for such a toner. The polyester resin is one of the following polyester resin (A)-(E) for toners. (A) A polyester resin for toners having an Mp as determined by GPC of not less than 12,000 and having an unsaturated double bond (B) A polyester resin for toners obtained by crosslinking the polyester resin (A) (C) A polyester resin for toners containing the polyester resin (A) and another polyester resin having an Mp as determined by GPC of less than 12,000 (D) A polyester resin for toners obtained by crosslinking the polyester resin (C) (E) A polyester resin for toners containing a THF soluble fraction and a THF insoluble fraction wherein the Mw/Mn of the THF soluble fraction is not less than 6 and the total of the acid value and the hydroxyl value of the THF insoluble fraction is not more than 40 mgKOH/g.