Producing foamed gypsum board using a foaming agent blend
Two foaming agents — one producing stable voids, one producing unstable voids — are preformed separately, then blended in a controlled pump ratio before entering the slurry, so the operator can tune void size independently of soap chemistry.
- Assignee
- United States Gypsum Co, USG Corp
- Inventors
- Steven W. Sucech
- Jurisdiction
- United States (USPTO)
- Filed
- 1996-02-08
- Published
- 1997-07-01
- Priority
- 1996-02-08
Every board plant knows that void size, not just void volume, drives finished-board properties: fine voids trade weight for strength, large voids trade strength for weight and sound absorption. Historically the only levers were changing the soap or reworking the mixer.
This patent gives the operator a mechanical lever instead: two foam streams, each preformed with a soap tuned for a specific void behaviour, blended at a variable ratio just upstream of the slurry mixer.
- 01Stream A is preformed foam made with an agent that yields stable voids in a gypsum slurry (fine, long-lived bubbles).
- 02Stream B is preformed foam made with an agent that yields unstable voids (larger, shorter-lived bubbles that coalesce into the finished large-void population).
- 03The two streams are pumped independently and blended at a set weight ratio — the claim specifies a greater weight of the unstable agent and a lesser weight of the stable agent.
- 04The blended foam is mixed into the slurry, producing a multiplicity of large voids distributed through the core; the ratio is trimmed on the fly through pump-set adjustments.
| Parameter | Value | Source |
|---|---|---|
| Foam agents used | two — one producing stable voids, one producing unstable voids | claim 1 |
| Blend ratio | unstable agent > stable agent (by weight) | claim 1 |
| Adjustment mechanism | adjust pump settings to change the weight ratio of the two agents | claim 1 |
- 01Requires two independent foam generators and dosing pumps of comparable calibration — the whole benefit disappears if pump A drifts against pump B.
- 02The blend ratio is a fast, physical setpoint operators can move during a shift, which makes recovery from off-target density much quicker than a soap change.
This invention is a process and foaming system for producing foamed gypsum board which permits the production and control of large foam voids in the gypsum core by adjusting the ratio of a first foaming agent and a second foaming agent. My process includes the steps of preforming a first foaming agent which forms stable foam voids in a gypsum slurry and independently preforming a second foaming agent which forms unstable foam voids in a gypsum slurry. Independently, blending the two different foaming agents is the key to controlling void size. A greater amount of the second foaming agent and a lesser amount of the first foaming agent is preferred.
A process for producing foamed gypsum board which comprises the steps of: providing an aqueous gypsum slurry; providing a stream of a preformed first foaming agent which forms stable voids in a gypsum slurry; providing a stream of a preformed second foaming agent which forms unstable voids in a gypsum slurry; pumping and blending the streams of the first foaming agent and the second foaming agent together to form a blended stream of the foaming agents having a greater amount by weight of the second foaming agent and a lesser amount by weight of the first foaming agent; mixing the blended stream of foaming agents with the gypsum slurry to produce a foamed gypsum core wherein the mixing produces a multiplicity of large voids substantially uniformly distributed throughout the foamed gypsum core; and controlling the production of the large voids by adjusting pump settings to adjust the weight ratio of the first foaming agent to the second foaming agent […]
Further claims, drawings, prosecution history and legal status: see the official record.
- [1]US 5,643,510 A — Producing foamed gypsum board using a foaming agent blend — Google Patents · 1997-07-01