Light weight gypsum board
A low-density gypsum core (roughly 10–30 pcf) engineered around a target void population where most of the void volume is made of relatively coarse air voids (>10 µm), stabilised by pregelatinised starch and a naphthalenesulfonate dispersant.
- Assignee
- United States Gypsum Co
- Inventors
- Qiang Yu, Weixin David Song
- Jurisdiction
- United States (USPTO)
- Filed
- 2006-11-02
- Published
- 2019-09-10
- Priority
- 2017-09-14
Board weight has been the single largest lever for panel manufacturers for two decades: lighter panels reduce raw material consumption per m², cut kiln residence time and lower freight cost per truck. The trade-off is always the same — as density drops, the core tends to lose nail-pull strength, edge hardness and machinability, and dust generation during cutting or routing rises.
This patent tackles that trade-off from the void side rather than from the paper side: it prescribes an internal architecture where the majority of the porosity is carried by large, well-formed air voids rather than a fog of fine water voids. The chemistry that survives set (pregel starch + naphthalenesulfonate dispersant) is what keeps the crystal network glued together at that porosity.
- 01Air is entrained by soap foam, sized and stabilised so the finished core lands in the 75–82 % total void range with at least 60 % of that volume in voids larger than ~10 µm.
- 02The naphthalenesulfonate (NS) dispersant deflocculates the stucco slurry so the mixer can still be run with a workable water-to-stucco ratio despite the low target density.
- 03Pregelatinised starch — hydrated during mixing rather than in the kiln — migrates with the water film and, after set, acts as a binder between adjacent gypsum crystals, restoring some of the strength that porosity removes and reducing the fine, respirable dust released when the panel is later cut, sawn, routed, snapped, nailed, screwed or drilled.
| Parameter | Value | Source |
|---|---|---|
| Target board density | ≈ 10 – 30 pcf | abstract |
| Total core void volume | ≈ 80 – 92 % (abstract) / 75 – 82 % (claim 1) | claim 1 |
| Fraction of voids that are large air voids | ≥ 60 % of total void volume | claim 1 |
| Large air-void size | > ~10 µm diameter (average) | claim 1 |
- 01Foam quality control (draw density and half-life at the mixer inlet) is the primary lever — you cannot hit this architecture with a marginal foam generator.
- 02NS dosage and pregel starch dosage move together: reducing dispersant to save cost usually forces water up and pushes the void distribution away from the >10 µm mode.
- 03Kiln profile has to be re-tuned when moving to this architecture — a lighter, more porous board dries faster and can be over-fired on the same setpoint as a legacy formulation.
This invention provides low dust low density gypsum wallboard products having high total core void volumes, corresponding to low densities in the range of about 10 to 30 pcf. The wallboards have a set gypsum core formed between two substantially parallel cover sheets, the set gypsum core preferably having a total void volume from about 80% to about 92%, and made from a slurry including stucco, pregelatinized starch, and a naphthalenesulfonate dispersant. The combination of the pregelatinized starch and the naphthalenesulfonate dispersant also provides a glue-like effect in binding the set gypsum crystals together. The wallboard formulation, along with small air bubble voids (and water voids) provides dust control during cutting, sawing, routing, snapping, nailing or screwing down, or drilling of the gypsum-containing products. This invention also provides a method of making the low dust low density gypsum products including the introduction of soap foam in an amount sufficient to form a total void volume, including air voids, preferably from about 80% to about 92% in the set gypsum core, corresponding to a set gypsum core density from about 10 pcf to about 30 pcf. The wallboards produced by the method generate significantly less dust during working.
A light weight gypsum board comprising: a set gypsum core disposed between two cover sheets; the set gypsum core formed from a slurry comprising water, foam, and stucco; the set gypsum core having a total void volume from about 75% to about 82% of the core volume, at least about 60% of the total void volume comprising air voids having an average air void pore size greater than about 10 microns in diameter […]
Further claims, drawings, prosecution history and legal status: see the official record.
- [1]US 10,407,345 B2 — Light weight gypsum board — Google Patents · 2019-09-10