초록 ▼

The invention provides gypsum wallboard, made from gypsum-containing slurries having outstanding hydration rate characteristics comprising alpha-hemihydrate ground to a particular particle size distribution range and having a Blaine surface area in the range from about 3100 cm2/g to about 9000 cm2/g

The invention provides gypsum wallboard, made from gypsum-containing slurries having outstanding hydration rate characteristics comprising alpha-hemihydrate ground to a particular particle size distribution range and having a Blaine surface area in the range from about 3100 cm2/g to about 9000 cm2/g, alone or in combination with beta-hemihydrate.

대표청구항 ▼

What is claimed is: 1. A 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, and ground alpha-hemihydrate having a particle size distribution within the foll

What is claimed is: 1. A 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, and ground alpha-hemihydrate having a particle size distribution within the following range: d (0.1)=about 3μ-5μ, d (0.5)=about 14μ-50μ, d (0.9)=about 40μ-100μ, and a Blaine surface area in the range from about 3100 cm2/g to about 9000 cm2/g. 2. The gypsum wallboard of claim 1, wherein the ground alpha-hemihydrate has a particle size distribution within the following range: d (0.1)=about 3μ-5μ, d (0.5)=about 14μ-20μ, d (0.9)=about 40μ-50μ, and a Blaine surface area in the range from about 3500 cm2/g to about 6000 cm2/g. 3. The gypsum wallboard of claim 1, wherein the ground alpha-hemihydrate has a particle size distribution of d (0.1)=about 3μ, d (0.5)=about 14.1μ, d (0.9)=about 45.9μ, and a Blaine surface area of about 3900 cm2/g. 4. The gypsum wallboard of claim 1, wherein the gypsum-containing slurry further comprises sodium trimetaphosphate present in an amount of at least about 0.12% by weight based on the weight of alpha-hemihydrate, and a naphthalenesulfonate dispersant present in an amount from about 0.5% to about 2.5% by weight based on the weight of alpha-hemihydrate. 5. The gypsum wallboard of claim 4, wherein the gypsum-containing slurry further includes a starch. 6. The gypsum wallboard of claim 5, wherein the starch is pregelatinized corn starch present in an amount up to about 6% by weight based on the weight of alpha-hemihydrate. 7. The gypsum wallboard of claim 1, wherein the gypsum-containing slurry further comprises beta-hemihydrate. 8. The gypsum wallboard of claim 7, wherein the ratio of alpha-hemihydrate to beta-hemihydrate is about 50:50 (w/w). 9. The gypsum wallboard of claim 7, wherein the gypsum-containing slurry further comprises sodium trimetaphosphate present in an amount of at least about 0.12% by weight based on the total weight of alpha-hemihydrate and beta-hemihydrate, and a naphthalenesulfonate dispersant present in an amount from about 0.5% to about 2.5% by weight based on the total weight of alpha-hemihydrate and beta-hemihydrate. 10. The gypsum wallboard of claim 8, wherein the gypsum-containing slurry further comprises sodium trimetaphosphate present in an amount of at least about 0.12% by weight based on the total weight of alpha-hemihydrate and beta-hemihydrate, and a naphthalenesulfonate dispersant present in an amount from about 0.5% to about 2.5% by weight based on the total weight of alpha-hemihydrate and beta-hemihydrate. 11. The gypsum wallboard of claim 10, wherein the gypsum-containing slurry further includes a starch. 12. The gypsum wallboard of claim 11, wherein the starch is pregelatinized corn starch present in an amount up to about 6% by weight based on the total weight of alpha-hemihydrate and beta-hemihydrate. 13. The gypsum wallboard of claim 1, wherein the cover sheets comprise paper. 14. A gypsum-containing slurry comprising: water, and ground alpha-hemihydrate having a particle size distribution within the following range: d (0.1)=about 3μ-5μ, d (0.5)=about 14μ-50μ, d (0.9)=about 40μ-100μ, and a Blaine surface area in the range from about 3100 cm2/g to about 9000 cm2/g. 15. The gypsum-containing slurry of claim 14, wherein the ground alpha-hemihydrate has a particle size distribution within the following range: d (0.1)=about 3μ-5μ, d (0.5)=about 14μ-20μ, d (0.9)=about 40μ-50μ, and a Blaine surface area in the range from about 3500 cm2/g to about 6000 cm2/g. 16. The gypsum-containing slurry of claim 14, wherein the ground alpha-hemihydrate has a particle size distribution of d (0.1)=about 3μ, d (0.5)=about 14.1μ, d (0.9)=about 45.9μ, and a Blaine surface area of about 3900 cm2/g. 17. The gypsum-containing slurry of claim 14, further comprising sodium trimetaphosphate present in an amount of at least about 0.12% by weight based on the weight of alpha-hemihydrate, and a naphthalenesulfonate dispersant present in an amount from about 0.5% to about 2.5% by weight based on the weight of alpha-hemihydrate. 18. The gypsum-containing slurry of claim 14, further comprising beta-hemihydrate. 19. A method of making gypsum wallboard, comprising the steps of: (a) mixing a gypsum-containing slurry comprising water, and ground alpha-hemihydrate having a particle size distribution within the following range: d (0.1)=about 3μ-5μ, d (0.5)=about 14μ-50μ, d (0.9)=about 40μ-100μ, and a Blaine surface area in the range from about 3100 cm2/g to about 9000 cm2/g; (b) depositing the gypsum-containing slurry on a first cover sheet; (c) placing a second cover sheet over the deposited slurry to form a gypsum wallboard; (d) cutting the gypsum wallboard after the gypsum-containing slurry has hardened sufficiently for cutting; and (e) drying the gypsum wallboard. 20. The method of claim 19, wherein the ground alpha-hemihydrate has a particle size distribution within the following range: d (0.1)=about 3μ-5μ, d (0.5)=about 14μ-20μ, d (0.9)=about 40μ-50μ, and a Blaine surface area in the range from about 3500 cm2/g to about 6000 cm2/g. 21. The method of claim 19, wherein the ground alpha-hemihydrate has a particle size distribution of d (0.1)=about 3μ, d (0.5)=about 14.1μ, d (0.9)=about 45.9μ, and a Blaine surface area of about 3900 cm2/g. 22. The method of claim 19, wherein the gypsum-containing slurry further comprises sodium trimetaphosphate present in an amount of at least about 0.12% by weight based on the weight of alpha-hemihydrate, and a naphthalenesulfonate dispersant present in an amount from about 0.5% to about 2.5% by weight based on the weight of alpha-hemihydrate. 23. The method of claim 19, wherein the gypsum-containing slurry further comprises beta-hemihydrate. 24. The method of claim 19, in which the first cover sheet and the second cover sheet are made of paper. 25. A gypsum wallboard consisting essentially of: a set gypsum composition formed between two substantially parallel cover sheets, the set gypsum composition made using a gypsum-containing slurry of: water, and ground alpha-hemihydrate having a generally unimodal particle size distribution within the following range: d (0.1)=about 3μ-5μ, d (0.5)=about 14μ-50μ, d (0.9)=about 40μ-100μ, and a Blaine surface area in the range from about 3100 cm2/g to about 9000 cm2/g.