CA1194043A

CA1194043A - Gypsum fire break composition

Info

Publication number: CA1194043A
Application number: CA000420823A
Authority: CA
Inventors: Edmund J. Janicki
Original assignee: National Gypsum Co
Current assignee: National Gypsum Properties LLC
Priority date: 1982-06-30
Filing date: 1983-02-03
Publication date: 1985-09-24

Abstract

GYPSUM FIRE BREAK COMPOSITION

ABSTRACT OF THE DISCLOSURE
A gypsum plaster composition which, on admixture of water, has improved plasticity and slip, together with other characteristics essential in a plaster for fire breaks and fire stops, such as used with electrical cables, consisting essentially of calcined gypsum, expanded vermiculite, bentonite clay, a dispersant and a set control additive for the gypsum.

Description

4~43 This invention relates to a specialized plaster composition for uses such as fire breaks and fire stops surrounding electrical cables. In particular it relates to compositions containing essentially calcined gypsum, expanded vermiculite and bentonite clay.
Compositions containing calcined gypsum as the potential binder formulated for use as fire breaks and fire stops around electrical cables are known, examples being the formulations disclosed in U. S. Patent 4~278,468, all of which contain diatomaceous earth, glycerine and boric acid. In addition to these essential ingredients of this prior patent disclosure, it is taught that other aggregates may be expanded vermiculite9 expand~d perlite, glass microspheres, wollastonite or the like. This prior patent also recognizes the importance of flow properties of a slurry of this gypsum composition and water.
The present invention is directed to pro~iding a gypsum composition with characteristics more like the characteristics being sought in this prior patent than the compositions disclosed therein. The characteristic which is particularly improved upon is the flow ; characteristic; however, other advantages are also noticeable~ The invention resides essentially in the combination of calcined gypsum, expanded vermiculite and bentonite clay, and also the absence of diatomaceous earth.

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It is an object of the present invention to provide a novel improved gypsum composition for fire stops and fire breaks.
It is a further object to provide such a composition having particularly improved flow or slip properties.
In accordance with the invention, gypsum compositions are provided consisting essentiaLly of ; calcined gypsum, expanded vermiculite and bentonite clay, which have characteristics, when mixed with water9 particularly suited for use as a fire break or fire stop around a group of electrical cables, or other slightly high temperature utility lines capable of, otherwise, conducting fires therealong.
A group of electrical cables with flammable insulation create a potential problem of spreading fires within a room, or from room to room through openings provided for passage of the cables. Aqueous settable gypsum slurries have been provided for encasing

2~ the group of cables. The formulation of the present invention permits such a slurry to more thoroughly and easily encase a group of cables.
EXAMPLE I
The preferred formulation of the invention is ; as follows:
Parts by Wei~ht Calcined Gypsum (CaS04-1/2H20) fiS
Expanded Vermiculite (#4 Grade) 25 Bentonite Clay 10 Lignin SulEonic Acid (Dispersant) 0.4 Hydrolyzed Proteinaceous Set Retarder (As required) Water - 2 - 120-160 The amount of water to be used in the preerred formulation may be varied in accordance with the degree of fluidity desired. The calcined gypsum has a fineness of 95% through a 100 mesh screen. The expanded vermiculite, of No. 4 grade, is available from the W. R.
Grace Company. No. 4 grade has a 6 to 10 #/cu ft density, with 0-5% retained on 16 mesh, 15-65 on 30 mesh, 60-98%
on 50 mesh and 90-100% on 100 mesh. A suitable bentonite clay is grade SPV-200 from American Colloids Company, with 80% below 200 mesh, a ph of 9 and a moisture content of between 5 to 9 percent. The lignin sulfonic acid dispersant may be .~merican Can Company's Marasperce C-21.
The hydrolyzed proteinaceous set retarder can be prepared in accordance with U.SO Patent 2,865,905.
The amount desired will vary with individual job require-ments.
-EXAMPIES II and III
The amount of calcined gypsum can be varied from about 50% to about 80% of the total weight of the dry ingredients as follows:
II III
Parts b~ Wei~h~ _arts by Wei~ht Calcined Gypsum 50 80 Expanded VeL~iculite 30 15 Bentonite Clay 20 5 Lignin Sulfonic Acid 0.6 0.2 Set Retarder (As required) The wet mix density of the ~rmulations of the invention, with 120 to 160 parts water added, is about 66 to 68 lbs/cu ft, while the dry set densities are about ~$~ 3 28 to 33 lbs/cu ft. Compressive strengths of the set products vary from 70-180 psi. The percent of setting expansion is about .19% to .25%.
The thermal conductivity K value at 3Q lbs/cu ft dry density is about .97 BTU/hr/ft2 - 0F/in.. The drying time, under ambient conditions, of a two~inch thick section is about 4 to 5 days.
It will be particularly noted that the formulations of the invention are free of any diatomaceous earth. The bentonite clay functions to thicken an aqueous slurry of the formulations of the invention, holding water and providing excellent slip.
Having completed a detailed disclosure of the preferred embodiments of my invention so that those skilled in the art may practice the same, I contemplate that variations may be made without departing rom the essence of the invention or the scope of the appended claims.

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A gypsum fire barrier composition consisting essentially of about 50 to 80 parts by weight calcined gypsum, about 15 to 30 parts by weight expanded vermiculite and about 5 to 20 parts bentonite clay, said composition being free of diatomaceous earth.

2. A gypsum fire barrier composition as defined in claim 1 wherein said composition additionally includes about 1% or less of a dispersant, and set retarder as needed for said calcined gypsum.

3. A gypsum fire barrier composition as defined in claim 1 consisting essentially of about 65% calcined gypsum, 25% expanded vermiculite and 10%
bentonite clay.

4. A gypsum fire barrier composition as defined in claim 3, wherein said composition additionally includes about 1% or less of a dispersant, and set retarder as needed for said calcined gypsum.

5. A gypsum fire barrier composition as defined in claim 1 wherein said calcined gypsum has a fineness such that 95% passes through a 100 mesh screen, said expanded vermiculite is No. 4 Grade, and said bentonite clay has a fineness such that 80% passes through a 200 mesh screen.

6. An aqueous settable gypsum slurry comprising about 100 parts by weight of the composition of claim 1 and about 120 to 160 parts by weight of water.

7. An aqueous settable gypsum slurry comprising about 100 parts by weight of the composition of claim 2 and about 120 to 160 parts by weight of water.

8. An aqueous settable gypsum slurry comprising about 100 parts by weight of the composition of claim 3 and about 120 to 160 parts by weight of water.

9. An aqueous settable gypsum slurry comprising about 100 parts by weight of the composition of claim 4 and about 120 to 160 parts by weight of water.

10. An aqueous settable gypsum slurry comprising about 100 parts by weight of the composition of claim 5 and about 120 to 160 parts by weight of water.