Sodium Zinc Mixed Ionomer Interlayer for Low Haze
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Solution Overview
Problem
Existing safety laminates face challenges in maintaining good optical properties and moisture resistance at greater thicknesses, particularly with slower cooling rates which can lead to crystal formation and increased haze.
Innovation Solution
A sodium/zinc mixed ionomer composition is used for the interlayer sheets, comprising 50 to 95 equivalent% sodium cations and 5 to 50 equivalent% zinc cations, based on total carboxylate groups, derived from a precursor acid copolymer with specific copolymerized units and melt flow rates, which are neutralized to produce sheets with improved clarity and moisture resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the interlayer material is increased to improve ballistic resistance, then penetration resistance is improved, but optical properties deteriorate due to increased haze from crystal formation during slower cooling rates
Solution Approach 1:
The patent changes the chemical composition parameters of the ionomer by controlling the ratio of sodium to zinc cations (5:1 to 1:5 ratio) and adjusting the neutralization level (40-90% of carboxylic acid groups). This compositional parameter change modifies the crystallization behavior of the polymer, enabling thick interlayers to maintain low haze (<5%) even during slower cooling rates typical of thick laminate processing, thus resolving the contradiction between thickness for ballistic resistance and optical clarity
Solution Approach 2:
The patent creates a composite ionomer system by combining two different cations (sodium and zinc) in specific proportions within the same polymer matrix. This composite approach leverages the complementary properties of each cation: sodium provides good optical properties while zinc enhances moisture resistance and controls crystallization. The synergistic effect of this composite material allows thick interlayers to achieve both ballistic resistance and maintained optical properties
2Strength
If the thickness of the interlayer material is increased for enhanced protection, then safety performance is improved, but moisture resistance deteriorates
Solution Approach 1:
The patent changes the ionic composition parameters by incorporating zinc cations at levels of 10-50 equivalent% in the mixed sodium/zinc ionomer. This parameter change fundamentally alters the polymer's interaction with moisture, as zinc ions provide superior moisture resistance compared to sodium ions. The specific ratio of sodium to zinc cations (5:1 to 1:5) optimizes both the moisture barrier properties and the mechanical strength, allowing thick interlayers to maintain both safety performance and moisture resistance simultaneously
3Ease of manufacture
If slower cooling rates are used during manufacturing to accommodate thicker laminates, then processing flexibility is improved, but crystal formation increases leading to higher haze
Solution Approach 1:
The patent changes the thermal and compositional parameters of the ionomer material. By adjusting the sodium/zinc cation ratio and neutralization level, the material's crystallization kinetics are modified. This allows the material to be processed at slower cooling rates (providcing processing flexibility for thick laminates) without forming excessive crystals that would cause haze. The modified material parameters enable crystallization control even under slow cooling conditions, maintaining clarity while accommodating thick laminate manufacturing
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 sodium/zinc mixed ionomer composition maintains high clarity and moisture resistance, with percent haze levels less than 5% and moisture weight gain less than 5% after immersion, independent of cooling rates during the lamination process, enhancing the performance of safety laminates.
Implementation Method 1
The interlayer sheet comprises or is prepared from a sodium/zinc mixed ionomer that comprises carboxylate groups and a combination of counterions. This combination consists essentially of 50 to 95 equivalent% of sodium cations, and, complementarity, 50 to 5 equivalent% of zinc cations, based on the total number of equivalents of carboxylate groups in the sodium/zinc mixed ionomer.
Implementation Method 2
any deficiency in the material's optical properties, such as haze, for example, increases in significance. These deficiencies may be exacerbated by the slower cooling rates typical of thicker safety laminates, which are more conducive to the formation of crystals.
Data Source
AI summary
A laminate comprises an ionomeric interlayer sheet which, in turn, comprises or is prepared from a sodium/zinc mixed ionomer that comprises carboxylate groups and a combination of counterions that consists essentially of sodium cations and zinc cations. The sodium/zinc mixed ionomer is the neutralization product of a precursor acid copolymer. The precursor acid copolymer comprises copolymerized units of an a-olefin and an a,-ethylenically unsaturated carboxylic acid, and it has a melt flow rate of about 70 to about 1000 g/10 min. In addition, the precursor acid copolymer, when neutralized to a level of about 40% to about 90%, and when comprising counterions that consist essentially of sodium ions, produces a sodium ionomer that has a freeze enthalpy that is not detectable or that is less than about 3.0 j/g, when determined by differential scanning calorimetry.