High starch light weight gypsum wallboard
A slurry recipe that combines a naphthalenesulfonate dispersant (0.1 – 3 % of stucco) with an unusually high pregelatinised starch loading (0.5 – 10 % of stucco) to produce a light, high-strength, low-dust wallboard.
- Assignee
- United States Gypsum Co
- Inventors
- Qiang Yu, Weixin D. Song, Michael R. Lynn
- Jurisdiction
- United States (USPTO)
- Filed
- 2006-06-07
- Published
- 2010-06-08
- Priority
- 2006-06-07
This patent is essentially the chemistry backbone that the later light-weight-board patents rely on. It legitimises pushing pregel starch far above the traditional cooked-starch dose of a legacy board recipe, on the argument that at this loading the starch stops being just a paper-bond aid and starts binding the crystal network from the inside.
The dispersant side is a naphthalenesulfonate (NS) salt — the workhorse dispersant of the industry — used inside a defined dose envelope so the slurry stays rheologically stable at the low water levels that lightweight boards require.
- 01NS dispersant deflocculates stucco particles so the mixer can produce a homogeneous slurry with less water than a plain formulation would need.
- 02Pregelatinised starch, hydrated in cold water rather than in the kiln, migrates uniformly through the slurry. During set it stays inside the core, providing a starch–gypsum glue-like network.
- 03The claim also envisages secondary additives — trimetaphosphate salts, accelerators, binders, paper and glass fibres — used within the same recipe, showing the combination is meant to be tuned around a full board formulation, not a single additive.
| Parameter | Value | Source |
|---|---|---|
| Naphthalenesulfonate dispersant dose | 0.1 – 3.0 % w/w of dry stucco | abstract |
| Pregelatinised starch dose | 0.5 – 10 % w/w of dry stucco | claim 1 |
| Ancillary additives contemplated | trimetaphosphate salts, accelerators, binders, paper fibre, glass fibre | abstract |
- 01Pregel starch at this loading changes slurry viscosity noticeably. Mixer power draw and head-box level should be baselined before and after a switch.
- 02The dispersant/starch balance is not additive: raising starch usually forces a small increase in dispersant to keep the target water/stucco ratio.
- 03Trimetaphosphate is called out as an optional companion — worth knowing when investigating recurring sag or edge softness problems.
The invention generally provides gypsum-containing slurries including stucco, naphthalenesulfonate dispersant, and pregelatinized starch. The naphthalenesulfonate dispersant is present in an amount of about 0.1%–3.0% by weight based on the weight of dry stucco. The pregelatinized starch is present in an amount of at least about 0.5% by weight up to about 10% by weight of pregelatinized starch by weight based on the weight of dry stucco in the formulation. Other slurry additives can include trimetaphosphate salts, accelerators, binders, paper fiber, glass fiber, and other known ingredients. The invention also comprises the gypsum-containing products made with such slurries, for example, gypsum wallboard, and a method of making gypsum wallboard.
A light weight high strength, low dusting gypsum wallboard comprising: a set gypsum composition formed between two substantially parallel cover sheets, the set gypsum composition made using a gypsum-containing slurry comprising: water, stucco, pregelatinized starch, and a naphthalenesulfonate dispersant, wherein the pregelatinized starch is present in an amount from about 0.5% by weight to about 10% by weight based on the weight of stucco.
Further claims, drawings, prosecution history and legal status: see the official record.
- [1]US 7,731,794 B2 — High starch light weight gypsum wallboard — Google Patents · 2010-06-08