US2108761A

US2108761A - Fire resistant pulp board

Info

Publication number: US2108761A
Application number: US71535A
Authority: US
Inventors: Hubert L Becher
Original assignee: Homasote Co
Current assignee: Homasote Co
Priority date: 1936-03-28
Filing date: 1936-03-28
Publication date: 1938-02-15
Anticipated expiration: 1955-02-15

Description

Patented Feb. is, 1938 UNlTED STATES PATENT Homasote Company,

Jersey No Drawing. Application March Serial No. 71,535

12 Claims.

My invention relates to a pulp board which is highly fire-resistant and to the method of making the same;

-My invention is of particular advantage in 5. connection with molded pulp board, such as is usually nmde by running wood pulp, paper pulp or the like into a mold and'by means of pressure removing the majority of the water (see, for instance, United States Letters Patent No. 971,936,

dated October 4, 1910, and No. 1,272,566 dated July 16, 1918) and subsequently drying out the,. remainder of thewater by the application of heat. After it has been dried, or simultaneously with the drying, the board may, if desired, be

subjected to high pressure in order to compact the same thus giving it higher tensile and transverse strength-and a higher degree of hardness. The

object of my invention is to produce a pulp board whose fibres are coated with aluminum hydrate to such an extent that the board is highly fire-resistant and will smolder as little as possible, if at all, after having been exposed to a flame, which contains a substantial proportion of incombustible substances, and which has a surface suflclently hard to resist minor injuries.

- It is a further object of my invention to apply aluminum. hydrate to fibres in such a manner that when such fibres are molded or otherwise formed into the preliminary shape of the finished 0 board there will be as little interference as possible with the drainage of the water from the pulp and no undue warping of the wet board.

()ther objects of my invention will be apparent from the following description thereof.

35 In order to fireproof the pulp fibres in the best manner known to me, I deposit aluminum hydrate thereupon before they are shaped into the form of a board. I deposit such aluminum hydrate preferably in the form of a precipitate from a double 40 decomposition of an aluminum salt and of some ,fother' substance which willreact with such aluml num salt to form aluminum hydrate, but not such a substance-as will react'with the aluminum salt to form insoluble crystals. I-prefer to use alumlnum sulfate and caustic soda or, sodium alwminate, obtaining in each case aluminum hydrate and sodium sulfate, the latter in-the form of soldble crystals which eventually will go out with the wash water. The aluminum hydrate when obtained as a precipitate from the double decomposition referred to, is in a fine state of subdivision and will therefore more readily coat each of the pulp fibres. I prefer to cause the reaction between the aluminum sulfate and the 55 caustic soda or other reagent to take place in the beater in which, and while, the pulp is being beaten. first adding the aluminum sulfate and. when this has been thoroughly dissolved in the beater, adding a suspension of caustic soda or other suitable reagent, but I may cause such rea corporation of New action, and obtain the precipitated aluminum hydrate resulting therefrom, in a separate vessel, ln which event the precipitate should'be used as soon as possible to prevent agglomeration thereof. The proportion of aluminum hydrate is preferably such as will result in as complete a coating of .the pulp fibres as possible, but not much more than that, so as not to interfere with the proper felting thereof.

To the pulp which is being beaten in the beater, I add, preferably before adding the aluminum hydr te and other reagent, a substantial proporti n of fullers earth, although I may add this while the reaction'is taking place or even afterwards. Preferably at the same time at which I add the fullers earth, I add to the pulp, while it is being beaten, a substantial proportion of en foliated vermiculite, although I may do this at a later stage. Preferably, after the reaction has taken place and before adding any sizing (if sizing be added) I add a substantial proportion of asbestos fibres sufficiently short, for instance, I /3 inch in average length, so as not to interfere with the subsequent proper felting of the fibres and the pulp. The flbresare known in the trade as asbestos floats. My reason for adding the asbestos fibres, if I add them at all, after the re- "action has been completed, is that I desire to have'the aluminum hydrate coat as fully as possible the fibres of the pulp, which must be fireproofed, the asbestos itself, of course, needing no fireproofing; also to have the asbestos fibres protect the coated fibres. I prefer to render the board waterproof as well as fire resistant, and therefore prefer to add to the beaten mixture of the ingredients hereinabove referred to, the usual soap (sizing) and thereafter to precipitate it ontothe fibres. A

After the materials hereinabove referred to have been thoroughly mixed, the board is shaped in a mold. or otherwise and dried. after which it may, if desired, be compacted; or it may be simultaneously dried and compacted, for instance, in a hot press, My present preferred formula is the following, by weight:

. a Per "cent Pulp (dry) s 26 Aluminum hydrate"; e Asbestos 7 Fuller's earth I 2c Exfoliated vermiculite r.. '35.

This formula may be varied, not only by leavlog out the asbestos but also by changing the proportions of the remaining ingredients. I have obtained good results by using pulpidfy weight) to aluminum hydrate 6 to 8%, asbestos 'l to 10%, fullers earth 25 to 30%, and exfoliated vermiculite 30 to I I have already indicated that the asbestos may be omitted, although the board is very much improved by its presence. In place of fuller's earth I may use an equivalent material, such as kaolin, or other finely divided clay, or bauxite, but I have not found as yet any equivalent which is as. effective as fullers earth or nearly so as bauxite; care should, however, be taken to use a fullers earth'which is not too dense-for instance, such as I have obtained from England which, I understand, is of the density characteristic of the fuller's earths found in suchcountry, and isnot so effective because it is entirely too dense. The main purpose of using this material is not only to avoid using in the fire-resistant board too much of the combustible pulp, but also to assist in hardening the surface of the completed board. The purpose of using exfoliated vermiculite is to obtain very free drainage during the step of reor other suitable hygroscopic salt or sodium .thiosulfate, to produce a 2% or 3% solution of this material with the water in the beater. The purpose of adding this material is to guard against a deterioration of the aluminum hydrate covering of the individual fibres, if the board should be dried, or exposed to fire, for so long a time as would otherwise cause suchdeterioration. Of course, such overdrying should be avoided, if possible, but with the'addition of either one of these salts the danger of the aluminum hydrate becoming porous or shrinking (because of dehydration) thus exposing some of the fibre, is avoided.

My preferred method (which results in the let's?1 costly board) therefore includes the fol- 10 g steps:

1. Preparation of a pulp suspension from any suitable fibre, such as wood fibre, chemically digested fibre or mixtures thereof, as can be obtained, for instance, by beating up old newspapers; bagasse or straw may be used in whole or in part. I refer to all such substances in my claims as cellulosic fibres. Enough water should be used to permit the fibres to fiow freely.

2. Adding to 26 parts by weight of pulp (dry), as it is being beaten in the beater, 26 parts by weight .of fullers earth and 35 parts by weight of exfoliated vermiculite, the beating continuing until all the ingredients have. been thoroughly mixed.

4. Preparation of aluminum -hydrate in the requisite finely divided form, in an amount just about suificient to coat the fibres, by adding aluminum sulfate to the beater and, when this is dissolved, adding .a solution of the requisite amount of sodium aluminate; Just about, enough ofthe latter substance should be used to convert the aluminum of the aluminum sulfate. into aluminum hydrate; I' prefer to use-this substance, as the combination of the sodium with the sulfate-ion will also release aluminum hydrate contained in the sodium alumin'ate. It is advisable that the solution of sodium aluminatebe added gradually to the solution'of the aluminum sulfate, to give full opportunity to the aluminum hydrate particlu to coat fully the pulp fibres.

The beating should be continued during this step.

Enough aluminum sulfate and sodium alumi nate should beadded to result in the formation of about 6 parts by weight of aluminum hydrate, keeping in'mind that aluminum hydrate is obtained not only from the reaction between the aluminum of the aluminum sulfate, but that the sodium aluminate itself embodies aluminum hydrate.

As the pulp is to be subsequently sized, care should be taken to keep or render the mixture in the beater neutral or slightly alkaline, so as to avoid premature precipitation of the soap.

4. Adding to the beater 9 parts of well shredded asbestos fibres, the fibres preferably not exceeding M; inch in length, to 26 parts by weight of pulp (dry), the beating being continued until the ingredients are thoroughly mixed.

5. A suitable rosin or other soap, in weight equal to about 2% to 3% of the total weight of the solid materials, is added to the beater charge as a sizing ingredient, preferably after the asbestos, fullers earth and exfoliated vermiculite have been thoroughly mixed with the pulp.

6. The soap is then precipitated by adding a suitable quantity of a suitable precipitant, such as aluminum sulfate.

7. Calcium chloride (or magnesium chloride) is then added in an amount sui'ilcient to produce a solution of 2% strength with the water in the beater.

1-7. Preferably the beatingof the pulp, and thereafter of the pulp and other ingredients as the latter are being added, continues throughout the first seven steps, so that a thorough mixture of the various ingredients is obtained.

8. The pulp is then shaped in a mold or otherwise, and dried, and compacted. The drying time depends, of course, upon a number of factors, such as the thickness of the board and the amount of water contained therein. Care should .be taken not to dry for so long a time as to over usein construction work exposed to the elements.

It has-rigidity and good mechanical strength with freedom from brittleness. and a low heat transmission as compared with boards composed principally of mineral products, such as cement, asbestos or plaster. My invention may be employed, with substantially equally good results, in making a pulp board bythe laying up process, that is, by forming paper-like layers of the board, for

instance, on a paper making machine, and uniting the layers thereof in the usual manner, for instance, with the aid of sodium silicate.

The proportions of material hereinabove given may be varied, as may also the steps and succession .of steps outlined in my statement of. preferred method, without departing from the spirit of my invention. All of the proportions given hereinabove are approximate. 1

The aluminum hydrate, referred to by me, is

I claim:

1. A highly-fire resistant'lubstantially hard surface board comprising cellulosic fibres coated with aluminum hydrate and mixed with a substantial proportion of fullers earth and exfoliated vermiculite. a A

2. A highly fire resistant substantially hard surface board, as claimed in .claim 1, containing, by weight, cellulosic fibres 25 to 30 parts, aluminum hydrate 6 to 8 parts, fuliers earth 25 to 30 parts, and exfoliated vermiculite 30 to 40 parts.

.3. A highly fire resistant substantially hard surface board, as claimed in claim 1, comprising, by weight, cellulosic fibres approximately 26 parts, aluminum hydrate approximately 6 parts, ful1er's earth approximately 26 parts and exfoliated vermiculite approximately 36 parts.

4. A highly fire resistant substantially hard surface board, as claimed in claim 1, containing also a substantial proportion of asbestos.

5.. A highly flre resistant substantially hard surface board as claimed in claim 1, comprising,

by weight,'cellulosic fibres 25 to 30 parts, aluminum hydrate 6 to 8 parts, fullers earth 25 to 30 parts, exfoliated vermiculite 30 to 40 parts, and

asbestos 7 to parts.

6. A highly fire resistant substantially hard surface board as claimed in claim 1, comprising by weight, cellulosic fibres approximately 26 parts, aluminum hydrate approximately 6 parts,

fullers earth-approximately'26 parts, exfoliated vermiculite approximately 36 parts, and asbestos 7 parts.

7. A highly fire resistant substantially hard surface board as claimed in claim 1, containing also from 2% to 3% of a hygroscopic salt suitable to protect the aluminum hydrate from dehydration when exposed to heat. 4

8. A highly fire resistant substantially hard surface board as claimed in claim 1, containing by weight, cellulosic fibres 25 to 30 parts, aluminum hydrate 6 to 8 parts, fullers earth 25 to 30 parts, exfoliated vermiculite 30 to 40 parts and from 2% to 3% of a hygroscopic salt suitable to protect the aluminum hydrate from dehydration when exposed to heat. I

9. A highly fire resistant substantially hard surface board, as claimed in claim 1, comprising, by weight, cellulosic fibres approximately 26 parts, aluminum hydrate approximately 6 parts,

fullers earth approximately 26 parts, exfoliated vermiculite approximately 36 parts and from 2% to 3% of a hygroscopic salt suitable to protect the aluminum hydrate from dehydration when exposed to heat.

10. A highly fire resistant substantially hard surface board, as claimed in claim 1, containing also a substantial proportion of asbestos and from hygroscopic salt suitable to protect the aluminum hydrate from dehydration when exposed to heat. 12. A highly fire resistant substantially hard surface board, as claimed in claim 1, containing,

by weight, cellulosic fibres 26 parts,-aluminum hydrate 6 parts, fullers earth 26 parts, exfoliated vermiculite 36 parts, asbestos 7 parts and from 2% to 3% of a hygroscopic salt suitable to pro tect the aluminum hydrate from dehydration when exposed to heat.

. HUBERT L. BECHER.