US2046296A - Acoustical paint - Google Patents

Description

COATING OR PLASTIC Patented June 30, 1936 I UNITED STATES Cross Reference 2,046,296 PATENT OFFICE ACOUSTICAL PAINT No Drawing;

Application May 31, 1930, el'ial No. 458,926

This invention relates to plastic compositions, and has reference more particularly to plastic compositions for application to the walls and ceilings of buildings for the purpose of correcting the acoustical properties in said building.

In correcting the acoustical properties of rooms and buildings it is customary to apply an acoustical plaster, or other surface, to the ceilings or walls of the room, in a comparatively thick layer for absorbing the sound waves and preventing echoes in the room. Fiber boards and hair felt have been used for this purpose-but they are unsightly in appearance and give little or no decorative effect. After a period of time, these acoustical materials become soiled through use and rather unsightly, so that it is desirable to apply a thin layer of an acoustical paint over the acoustical material to give a fresh and clean surface and improve the appearance of the room. However, it is important that this acoustical paint applied to the acoustical plaster does not appreciably reduce the sound absorbing qualities of the acoustical material. It is also sometimes desirable to apply an acoustical paint in a rather thick, sound absorbing layer over a room surface which in itself is not sound absorbing, or over an old and soiled coating of acoustical paint. The decorative effect may also be produced by texturing our acoustical paint.

An object of this invention, therefore, is to provide a composition which is suitable for application over acoustical plaster, boards, tiles or mats for the purpose of improving the appearance and decorative effect of same.

Another object of the invention is to provide an acoustical composition which may be applied to building surfaces, for the purposes of absorbing sound waves; also to improveacoustical surfacing materials in other respects hereinafter specified and claimed.

Our improved composition is primarily intended for brush application to the surfaces of buildings for the purpose of absorbing impinging sound waves. It preferably contains a substantial amount of fibrous materials, and in order to secure proper brush application, we have found it necessary to provide special pre-treatment of the fibers in order to secure a uniform dispersion of same, as well as other qualities. This pretreatment of the fibrous material consists essentially in coating the fibers with a binder by mixing the fibrous material with the solution containing the binding material, drying, grinding and grading the product. While one pretreatment may be suihcient in certain cases, we have found that two or more pretreatments are desirable, and we shall designate these pretreatments as pretreatment M and pretreatment N". The pretreatments very materially improve the plasticitgifsni brushability of our acoustical product.

Pretreatment M ispre ed by adding a mixture of the following:

Parts by weight The wetted mass is placed on screens and dried, then ground through a Prater mill or other pulverizing machine and screened so that all passes an 8 mesh screen.

Pretreatment N is prepared by adding a mixture of the following:

Parts by weight Mineral wool 45.2 Asbestos No. 7 M 2.6 Pine sawdust (white pine, graded) 4.2

to the following binder solution:

Casein 32.0 Water 141.0 Ca (OH) 2 6 .4 Silicate of soda 22.4

This wetted mass is spread on a screen, dried, ground through a Prater'mill, and then screened so that all passes a 16 mesh screen.

Pretreatment M is a means of incorporating fibrous fillers, which have been wetted with an adhesive mixture. This aids in the dispersion of the fillers without greatly decreasing the fiber length of the mineral wool and cottonwood fibers, and without it the material is heavy and dense. The processed wheat or corn paste is a artiall dextrinized starch Corn or other fannaceous astes may be used with varying success.

Eetreatment.N"v contributes greatly to the porosity when used in conjunction with the other ingredients in the formula, and prevents the formation of a skin on the surface of the finished and dried acoustical paint which would reduce the porosity and sound absorbing qualities. An excess of pretreatment N darkens the color of the final composition and increases the number of surface cracks. It is our belief that 'the sodium lime caseinate precipitated on the surfaces of the fibers by the interaction of the ingredients in the pretreatment N", swells in the wet mix, and in drying contracts, leaving open and interconnecting pores which aid the sound absorbing qualities of the composition. The sodium silicate preferred has a NazO:SiOz ratio of 1:531 Having Examiner 11 per cent NazO and 31.2 percent 310: and a due to the increase in the percentage of pumice gravity of 47 B.

This pretreatment of the fibers may be accomplished in a number of different ways as long as the fibers are coated with the binding material before mixing with the main part of the composition. and only the preferred form of accomplishing these pretreatments is given below. The pretreated fibrous material may also be mixed with the other ingredients in the composition in a number of different ways, and two characteristic formulas will be given.

Formula No. 1 consists of the following ingredlents:

' Per cent Iumice (passing 20 mesh, retained on tion.

characteristic in the final composition. The marble gives weight, color and aids texturing properties besides ma ng a small contribution to the porosity.

The glue gives a stickiness very desirable for brush application. Glue gives a great portion of the final strength and an excess of glue reduces the porosity. Bone glue has given us the best results. The mas a preservative for the wheat paste and affects the viscosity of the glue. The wheat paste modifies the tenacious nature of the glue, increasing the consistency and contributing to the final strength and hardness. We believe furthermore it helps brushing characteristics and plasticity. The gum Karaya greatly increases the consistency and final porosity. It lightens the wet material and while an excess helps the porosity, it injures the application. The lithopone helps the color and brushing, giving a plasticity and gel characteristic very desirable for brush application. Its use must be controlled since an excess reduces porosity to a marked degree. The tribromophenol acts as a reservative and mold reventative. The oil of sassafras E used to mask the o ec onable phenol odor of the tribromophenol.

In formula No. 2 an increase in the pumice and marble gives better porosity and lower initial cost, but there is some sacrificing of desirable working characteristics and hardness of the final formula. Oxalic acid and paraformaldehyde act as insolubilizing agents on the glue. The paraformaldehyde may 5 added at the job if desired to prevent any undesired reactions in the dry mixture. Sodium phosphate increases the viscosity of times-a better body to the formula, but is not essential thereto. Other materials have been varied somewhat in proportion,

and marble.

Formula No. 2 is as follows:

Per-cent. Fumice (passing 30 mesh, retained on 48 5 mesh) 16.!

Marble (passing 30 mesh, retained on 48 48 mesh) 13.0 Marble (passing 20 mesh, retained on 48 mesh) 28.7 Cold water glue 2.4 Aluminum sulphate (A1:(SO4):.18H2O)..--- 1.3 Wheat past 2.4 Gum Karaya-.. 1.01 Lithopone 18.0 Pretreatment "M (Precoated fibrous material) 21.0 Pretreatment N (Precoated fibrous material) 16.0 Tribromophennl 0.2

Oil of sassafras, 4-5 drops per pound of composimesh) 33.4 Cold water glue 2.0 Aluminum sulphate (Alz(SO4):.18H2O) 1.1 10 Wheat paste 2.0 Lithopone m 12.5 Pretreatment "11 (Precoaied fibrous material) 16.7 Pretreatment "N" (Precoated fibrous mal5 terial) 13.3 Oxalic acid .1 Paraformaldehyde. .2 Karaya gum .83

\Dibasic sodium phosphate 12 20 Various materials may be substituted for those in our formulas Nos. 1 and 2, with varying success. Instead of the pumice and marble, we may use crushed, other crush pyro hyllite silica or 25 or graded fiii g fiagria s. Instead of cold water glue, casein bloo a umen,

or other binding or adhesive material? may He used.

It is thought that carbon dioxide gas is 30 formed by the action of alum on the marble. Potassium orsodi rbona or whiting may e as equivalent gas forming agents to react with the alum. This generated carbon dioxide not only improves the porosity of the dried paint, but also aids materially in preventing the formation of a surface crust which would reduce the sound absorbing efficiency of the paint. Instead of the wheat paste, corn sfg, tapioca or other farinaceous pastes may used. The gum Karaya has the property of forming a thick solution with 50 to 75 parts by weight of water, and when this water dries out, it gives the resulting dried composition a porosity where the space was previously occupied by water. Gum 45 tra acanth and Irish moss may be substituted for the gum Karaya. ad of the lithopone, other white igments may be used such as zinc oxide, um o e pigments and white lead pigmenmrvatives may e use stead of the tribromopfienol, such as phenol, crew} or beta naEthol, etc. Other aromatic substances mayt use tead oi oil of sassafras, such as oil 0 cloves, winter reen, ine oil, etc. WoH fibers other than cot'finwoo may be use cm a No. 2 tartaric and citric acid may be substituted insteme om with varying degrees of success and formaldehyde, lead acetate, or sodium or potass'm de. Instead of the dibasic sodium phosphate, monosodium ho hate, magesium chloride, soaF'um' Hydroxide or airome alum may be submmmnsimat paste, gum Karaya, tribromophenol, oil of sass'afras, asbestos. cottonwood fibers, sawdust, oxalic acid, paraformaldehyde and sodium phosphate desirable but non-essential ingredients of ourcom- D OIL Our acoustical paint may be colored in any shade by the addition of a suitable color pigment. The coloring, 'texturing and acoustical properties and possibilities, gives to our paint a. unique field of usefulness not achieved by other methods of decorating. 7

COATING R PLASTIC We would state in conclusion that while the illustrated examples constitute practical embodiments of our invention, we do not wish to limit ourselves precisely to these details, since manifestly the same may be considerably varied without departing from the spirit of the invention as defined in the appended claims.

Having thus described our invention, we claim as new and desire to secure by Letters Patent:

1. The step in the preparation of an acoustical composition which comprises mixing a fibrous material with a solution containing casein, water, hydrated lime, and silicate of soda, drying said fibrous mass to precipitate coating material on the surface of said fibers, and pulverizing said fibrous mass.

2. The method of pretreating fibrous material preparatory to mixing with an acoustical composition, which comprises precipitating a coating of sodium calcium caseinate on the fibers of the fibrous material, drying the fibrous material, and pulverizing said fibrous material.

3. A composition oi! matter for acoustical absorption of sound, having substantially the following formula:

Per cent Pumice (passing 20 mesh, retained on 48 mesh) 13.0 Marble (passing 20 mesh, retained on 48 mesh)- 26.65 Cold water (bone) glue 2.4 Aluminum sulphate (A12(SO4):.18H2O 1.3 Wheat paste 2.4 Gum Karay 1.05 Lithnpnne 16.0 Mixed mineral and vegetable fibers coated with a dextrin binder 21.0 Mixed mineral and vegetable fibers coated with a casein binder 16.0 Tribromophen 0.2

011 of sassafras, 4 to 5 drops per pound of composition. I 4. The method of preparing an acoustical composition, which comprises mixing a fibrous ma terial with a solution containing reactive agents for precipitating a water insoluble caseinate coating material on the surface of said fibers, drying and puiverizing the wetted fibrous mass to form a pretreated fibrous material, and mixing said pretreated fibrous material with a granular, inert filler, binding material selected from the group consisting of i'arinaceous paste, glue, casein, .and blood albumen, and with gas forming agents comprising carbonates and acid salts, water absorbing gum, a pigment, and a preservative agent.

5. The method of preparing an acoustical composition, which comprises applying a water insoluble caseinate coating material to the surface of fibers in a fibrous mass containing mixed vegetable and mineral fibers, drying and pulverizing said mass to form a pretreated fibrous material, and mixing said pretreated fibrous material with a granular filling material, a binding agent selected from the group consisting oi iarinaceous paste, glue, casein and blood albumen, and with gas forming agents, comprising carbonates and acid salts, and a pigment.

6. The step in the method of producing an acoustical composition, which comprises mixing Cross Reference 7. An acoustical composition comprising 30 to 37% of a mineral and vegetable fibrous material precoated with a mixture containing a binding material selected from the group consisting of iarinaceous paste, gum Arabic, casein and sodium silicate solution, 39.7 to 50.1% of an inert filler selected from the group consisting of granular pumice, marble, burned clay, pyrophyllite, and silica, gas forming agents comprising carbonates and acid salts, a water absorbent gum, and a preservative.

8. An-acoustical paint composition comprising 13.0 to 16.7% of granular pumice, 26.7 to 33.4% of granular marble, 'a binding agent selected from the group consisting of farinaceous paste, glue, casein and blood albumen, said composition also including gas producing agents comprising carbonates and acid salts, a gum having a high water absorbing property, and pigment, and 30 to 37% of a mixed vegetable and mineral fibrous material precoated with a binder selected from the group consisting of iarinaceous paste, gum Arabic, casein and sodium silicate solution.

9. An acoustical composition comprising 39.7 to 50.1% oil a granular inert material selected from the group consisting of pumice, marble, burned clay, pyrophyliite and silica, and passing a 20 mesh screen and retained on a 48 mesh screen, 30 to 37% of mixed mineral and vegetable fibrous materials precoated with a caseinate binder, a binding agent selected from the group consisting of farinaceous paste,'glue, casein and blood albumen, and agents comprising carbonates and acid salts for causing a porous structure in the mass of material for the absorption of impinging sound waves.

10. An acoustical composition comprising 30 to 37% of mineral and vegetable fibrous material precoated with a mixture containing an adhesive material selected from the group consisting of Iarinaceous paste,- Karaya gum, gum Arabic, casein, land sodium silicate; 39.7 to 50.1% of an inert filler selected from the group consisting of granular pumice, marble, burned clay, pyrophyilite and silica; glue; insolubilizing agents; gas forming agents comprising carbonates and acid salts; and a water absorbing gum.

11. An acoustical composition comprising 30 to 37% of mixed mineral and vegetable fibrous material precoated with a mixture containing an adhesive selected from the group consisting of Iarinaceous paste, Karaya gum, gum Arabic, casein, and sodium silicate; 39.7 to 50.1% of agranular inert filler material selected from the group consisting of granular pumice, marble, burned clay, pyrophyllite and silica; said mixture also containing glue, wheat paste, a gum having a high water absorbing property; gas generating materials comprising carbonates and acid salts, and a preservative.

12. The step in the preparation of an acoustical composition, which comprises mixing a fibrous material with a solution of fiber coating adhesive materials selected from the group consisting of iarinaceous paste, Karaya gum, gum Arabic. casein and sodium silicate; and drying and pulverizing the wetted mass to form a pretreated material suitable for use in an acoustical coating composition.

CARLISLE K. ROOS.

JAMES S. OFFU'IT.

HERMAN A. SCHOLZ.

EXcimi ner-