US 2550143 A
Description (OCR text may contain errors)
April 24, 1951 E. EGER 2,550,143
CONSTRUCTION BOARD AND METHOD OF MAKING SAME Filed NOV. 29, 1947 .ATTRNEY BY mzfmw Patented Apr. 24, r`1.951
CONSTRUCTION BOARD AND METHOD- F MAKING SAME Ernst Eger, Los Angeles, Calif., assgnor to United States Rubber Company, New York, N; Y., `a corporation of New Jersey Application November Z9, 1947, Serial No. 788,895
14 Claims. (Cl. 2GB-17.2)
This yinvention relates to a composition of matter in the formV of a board which is useful for construction purposes and l'to a method of making same.
The principal object 'of the present invention is to :provide an improved board useful for constructional purposes. Another object is to provide a-method of making such a board. Another object is to provide a structural boardv which is name-resistant even though a large proportion of combustible fibrous material enters into its composition. Another object is to provide such a board which is cheap to manufacture, strong, light in weight, resistant to Water and rmoisture and which may be produced either in relatively compact form for use as a backing or paneling material useful either in furniture or in the building trade or in a more porous, softer, less compact formhaving properties particularly adapting it for heat insulation or sound deadening. Another object is to produce a fibrous board of the foregoing type Without using high-pressure equipment. Another` object is to provide a composition and Vmethod yielding a brous board without requiring the application of positive mechanical pressure during the setting of the mixture. Numerous other objectsfof the present invention will more fully hereinafter appear.
In the accompanying drawing:
Fig. l is a flow diagram of the process of manufacture ofthe board of the present invention.
Fig. 2 is an edge view of a relatively compact board made in accordance with my invention. This view portrays the appearance of a cut edge or cross-section of the board;
Fig. Sis a similar view of a less compact boardv Amade in accordance with the present invention and especially useful for thermal insulating and sound absorbing applications.
I have discovered that an improved construction board can .be prepared by intimately mixing a brous material with an aqueous mixture comprising dispersed polymerizedv chloroprene and dissolved partially condensed vresorcinol-formaldehyde resin, allowing the aqueous mixture to set to a friable solid gel state, and drying to remove the water.
Any fibrous materialmay be employed in making the board of the present invention but I prefer to use ibrous material a substantial pro portion of which is composed of bers which are relatively elongated, i. e., which are long relative to their thickness, and which are adapted to interlace and form when bonded 'with the binder of the present invention ahomogeneous rboardlike structure of interlaced -bers in random distributionexhibiting greatstrength althoughjlight in weight. In practice I prefer that atleast 40% of the fibrous material employed be of such randomly interlacing fibers. Such interlacing fibrous material is to be distinguished from a granular or powdered fibrous material like sawdust, wood our orcork which vdoes not Yin'terlace and which when used alone does not give a product having the desired great strength. Y
- Examples of interlac'ing'brous materials which are sufficiently cheap and readily available to 'be employed -in making lthe board of my invention are straw, bagasse, cornstalks, cottonstalks, palmetto liber, jute liber, oat hulls, shredded woodbers such as excelsior, exploded wood fibers,
wood'barkiiber, etc. I prefer to use organic ber which is a by-product of the lumber industry or of agriculture and which vis available at very low cost and vis obtained chiefly asa waste product. The fibrous material is almost valways organic although I-can use inorganic fibrous materials such as asbestos, glass liber, slag, rock or mineral woolyetc. provided they are not too costly.
I have obtained unusually good results by the use of, a mixtureof shredded wood fibers, and
` ground .corkthe wood Iiberconstituting the in-v terlacingber component of themixture andthe cork serving as a non-interlacing fibrous compof nent which ,lls the voidsbetween the elongated, wood Yibers and giving a strong lyet lightprode uct. I especially prefer to employ a mixture of4 wood 'bark ber and wood bark cork both of which are found inthe barks of evergreens Use of a mixtureconsistingof approximately equal proportions of such wood bark fiber and such do# mestic cork obtained in known manner from 'evergreen bark is :especially satisfactory from -the standpoints of low cost and ready availability. A
The use of substantial proportions of cork in;` admixture with the interlacing brous material isv highly.. preferred `because itproduces a boardv which is much lighter in weight ythan a 'similar board in which no cork is employed. At the" same time the board made with cork has adequate 'strength and other characteristics adapt' ing/it for structural uses. The use of cork in the formof native woodrbark cork is especially advantageous because such cork is much cheaper than the imported cork from the cork oak. I prefer' to use cork in `amount ranging from 40 to of the fibrous material employed.
In practicing the present invention the fibrous material `is-int-imately mixed with an aqueous mixture comprising dispersed polymerized chloroprene and dissolved partially condensed resorcino1-formaldehyde resin and containing a condensing agent capable of effecting further condensation of the resin from the water-soluble state to a substantially insoluble substantially infusible state. After-effecting uniform intermixture of the brous material and the aqueous binder, the mixture is shaped to board-like form, as by troweling into place or in any other suitable manner. The resulting mixture is then allowed to stand, taking precautions if necessary to insure that substantial evaporation from the interior of the mass does not occur until the aqueous binding mixture sets to a friable solid gel state. After gelling has taken place, the board-shaped material is dried to remove the water. The drying step completes the resinforming reaction, carrying the resin to the insoluble infusible stage and effects removal of both ywater of reaction and water of solution, forming a tough, strong, flexible binder.
It is important that the shaped mixture be heldimmobilized, i. e. with its various parts stationary with respect to one another, during the gelling and during at least the major portion of the drying. Otherwise a -satisfactory bond is not obtained. Preferably the material isl maintained in undisturbed condition until at least 90% of the water present has been removed.
In some. cases the brous material may be wetted with water before intermixing it with the aqueous binding composition. This pre-wetting of the fibrous material causes it to mix more easily and more uniformly with the aqueous binding composition. Preferably the ber and the prewetting water are intimately mixed together in any suitable manner prior to addition Vof the binding composition. Where a mixture of fibrous materials, such as the mixture of wood bark ber and domestic cork described above, is employed this preliminary mixing with the pre-wetting waterhas the additional advantage of vfacilitating intermixture of the various types of fibrous material with one another so that a, better and more uniform product is obtained. The amount of water employed to pre-wet the fibrous material in the manner just described may vary widely depending upon `many factors including the water-absorptivity of the fibrous material; itl may range from-fonly a small amount up to that required to completely saturate the fibrous material. Usually the pre-wetting water is employed in an amount equal to at least 5% Aby weight of the fibrous'material.
Instead of pre-wetting the fiber with water as just described, it is voften more advantageous and practical to add the water for wetting the fiber to the aqueous binding composition, water` being added Ythereto in amount sufficient to dilute it substantially below 30%Y and usually to not over 25% of elastomer plus partially condensed resin, the dilution, however', being only to such anv extent that the elastomer plus resin content of the aqueous binder vleft after absorption of water therefrom by the fiber is at least 30%. For example the fiber-wetting water may be added to the aqueous binder and the fiber then added to the resulting diluted binder with mixing whereupon the fiber absorbs the excess water rapidly. This mode of operation is preferred since it has the advantage of eliminating one mixing operation, namely the pre-wetting-operation, the abs orption of the excess water by the fiber aiding in the mixing and readily giving a mixture which can be troweled into place or otherwise shaped for the production of the board.
Alternatively, a portion of the added water may be used to pre-wet the ber and the rest may be employed to dilute the aqueous binder.
An important requirement in practicing the present invention is that the Water content of the mixture be so adjusted that the content of neoprene (polymerized chloroprene) plus partially condensed resorcinol-formaldehyde resin in the aqueous mixture present on and around the bers after intermixture be at least by weight of such aqueous mixture. For example, if the fibrous material is completely saturated with water in the preliminary wetting step described above, the aqueous binder admixed there- A with should contain at least 30% of neoprene plus resin. If on' the other hand the fibers are dry or are incompletely saturated with water, then the aqueous binder commingled therewith can be diluted with water to a neoprene plus resin content below 30% provided the fibrous material is capable of absorbing enough water from the aqueous binder to raise the neoprene plus c resin content thereof at least to the 30% level.
Unless the neoprene plus resin content of the aqueous binder in the mixture after intermixture of fibrous material and binder is at least 30%, the binder will not go through the solid friable gel state and a satisfactory bond will not be obtained.
The aqueous binder composition should contain neoprene and the partially condensed resin in such relative proportions that the resorcinol content of the resin ranges from 3.8 to 16.8 and preferably from 6.75 to 15.0 per cent by weight based on the Vweight of neoprene. Unless these limits are observed, the material obtained byv gelling and drying of the binding composition is not satisfactory as a binder for the fibrous material.
The speed with which the binding composition used in the present invention gels to the requisite solid friable gel state isgreatly affected by the temperature, increasing rapidly therewith. Thus at room temperature it may not gel for several hours but as the temperature rises above F. it begins to gel very rapidly and at F. it gels almost immediately. For this reason, gelling may be greatly accelerated by subjecting the shaped mixture to elevated temperature conditions.
The speed of gelling is also greatly affected by the concentration of neoprene plus partially condensed resin in the aqueous binding mixture surrounding the fibers after mixture has been effected. Increase of this concentration by a few or even by a single per cent effects a considerable shortening of the gelling time. This concentration is often at least 35% and it may range as high as 55 or 460 per cent.
For this reason gelling is greatly accelerated by the phenomenon of absorption of water from the binding composition by the fibrous material with which it is mixed. If the fibrous material mixed with the aqueous binding composition is dry or is incompletely saturated with water, it will selectively remove water from the binding composition and thereby concentrate the same so that it will gel or will gel more rapidly.
After intermixture of the fibrous material with the aqueous binding composition and shaping thereof to the desired board-like form, evaporation of volatile material, principally water, from the mixture should be so limited that the requisite gelling takes place before any substantial surface evaporation occurs. '-If :surface evaporapreferably atelevated temperature to acceleratev gelling, for example by *maintaining same in a heated atmosphere of controlled high humidity until gelling has taken place. After gelling has been effected, the resulting mixture maybe `dried inanysuitable manner. I prefer` to yemploy elevated temperature during the dryinglstep to accelerate the same. For example l may employ a temperature fof from 1259-1?. to 150 F. in the drying step.
1. Il` often prefer to place. the Wet mixture of fibrous material and binder in sheet .form betweenscreens or perforated ysurfaces which may be free `tomove `or' may be locked in any suitable manner to Vprevent .separation during setting, the
gelling and drying steps being carried out whilev thefmaterial is between such screens or the like.
It is important that `the wet shaped; mixture be maintained in a relatively undisturbed condition until `it has taken its set, i. e. immobilized during the. gelling step .and during the major portion of the drying step, i. eruntil substantially all the. water-has been removed. The material is usually dried until at least 90% by weight of the water present has been removed before itis subjected to forces which wouldtend to disturb the relative positions of Ythe various portions thereof. If the material is' disturbed before it has taken itsfinal set, i. e. before the major rportion ofthe Water has been removed, it will be disintegrated into discrete portions. and rendered worthless.
The aqueous composition `used to form the binder in accordance with my invention is preferably ycomposed essentially Vof an aqueous `mixture Aof dispersed polymerized chlo-roprene, .clis-v solved partially condensed Water-*soluble resorcinol-formaldehyde resin :capable of settingupon removal of water by `further condensation to a substantially infusible, Asubstantially insoluble state, and an alkali metal hydroxide capable; of effecting such further condensation ofjsaid resin. Thisl composition is most conveniently prepared by simply mixing an aqueous dispersion of polymerized chloroprene with an aqueous solution of the partially condensed resorcinol-formaldehyde. l
resin `and an aqueous solution of alkali metal hydroxide. The aqueous mixture may embody otheningredients such as suitable proportions of fillers, pigments, anti-oxidants, dyestuffs, suspending agents, dispersing agents, wetting agents, etc. such asagents for holding the polymerized chloroprene and the llers or pigments in suspension in the aqueous medium. The aqueous mixture may contain ingredients solubilizing or holding in solution the partially condensed resorcinol-formald-ehyde resin, a preferred example of such a material being an alkali metal hydroxide, typically sodium hydroxide. The lcomposition will contain excess or unreacted formaldehyde for completing condensation of the resin and effecting hardening'such other components of the formulation as casein, glue, etc. It is preferred that the aqueous composition embody. a catalyst for effecting completion of the resin-forming condensation, such catalyst preferablybeing an excess of alkali metal hydroxideV i in formulating 'the resin may vary Widely but usually a molar excess of formaldehyde over res-` orcinol is employed to give the ultimate formation of an insoluble infusible resin. The resorcinol and formaldehyde are preliminarily reacted together, the reaction being stopped before completion, i. e. before lthe condensation product has reached the insoluble infusible stage which may also be before all the formaldehyde has reacted. The ,partially condensed resin is soluble in Water andy in dilute .aqueous alkali metal hydroxide-solution. If desired the resorcinolmay be reacted withy a .part only .of the formaldehyde and the remainder of the formaldehyde may be added to the formulation at any time prior to use.
In themanufacture of the partially condensed resin capable of setting upon removal of Water to the insoluble infusible stage, it is often pre-` ferred -to employ a molar ratio of total formaldehyde to resorcinol ranging from V2:1 to l3:1.
Upon gelling and drying, :the incomplete kresinforming reaction proceeds to completion. The free formaldehyde present after the initial reaction is available to carry the reaction to completion during the drying step and also to harden :and insolubilize any protein such Aas casein-.or
glue present in the -formulation. The preliminary' resin-forming reaction may conveniently becarriedout by forming amixture of resorcinol` and waterat an elevated temperature, say 130 to 200 F., and adding the formaldehyde, e. g. in the form of commercial 37 to 40% aqueous solution, withstirring. It may be desirable to add the formal-i dehyde-gradually over a considerable period of time in View of the highly exothermic nature Vof the .resin-forming reaction which, if allowed to get out of control, may yield a completely unusable resin.` If desired, known catalysts vfor the resin-forming reaction such as oxalic acid, ben-v zene sulfonic acid, etc. may be employed. Preferably :ho-Wever an alkali metal hydroxide, typically included inthe final vcomposition additional aqueous alkali metal hydroxide solution beyond that necessary vto hold the partiallycondensed` resin in' solution, such additional alkali metalhydroxide serving to complete the resin-forming reaction las above stated. The resulting mixture `is unstable, that is, it gels upon standing for a relatively short time, usually not over 8 hours, the length of'` time required -for gelling to take place depending upon many factors, especially the 'concentration Yofneofprene plus resin and thertemperature to which the mixture is subjected.
Any "desired .proportions 'of.1; igments,I llers, etc.
may be used in the formulation depending uponv the desired consistency of the aqueous mixture and the properties desired in the final gelled `and dried binder. The proportions of casein or similar protein will usually not exceed The proportion of alkali metal hydroxide present in the nal formulation will not ordinarily exceed 2% but is'usually at least 0.1% of the aqueous mixture used to form the binder. These percentages are by weight of the total binding composition on a water-free basis.
When, as in the preferred practice of my invention, polymerized chloroprene is the sole rubbery or elastomeric material present, the gelling and setting of the aqueous mixture does not depend upon vulcanization and in fact no vulcanizing agents, accelerators or the like ingredients are used in the aqueous mixture. The excellent results of the present invention are obtained Without'vulcanization merely by allowing such an aqueous composition to gell followed by drying to remove the water.
Where reference is made herein to the proportion of partially condensed resin (as where I refer to thev percentage of the sum of polymerized chloroprene and resin), the sum of resorcinol and the total formaldehyde required to set the same to the insoluble infusible state is intended, although all such formaldehyde is not combined in the initial resin-forming condensation. Of course formaldehyde in excess of such requirement is not included although the amount of such excess would ordinarily be so small as to be almost inconsequential.
Instead of using an aqueous dispersion of polymerized chloroprene (neoprene) in the practice of my invention I may less preferably use latices ofelastic rubbery or rubber-like sulfur-vulcanizablematerials such as GR-S (butadiene-styrene synthetic rubber) latex, Buna N (butadieneacrylonitrile synthetic rubber) latex, isoprenestyrene synthetic rubber latex, etc. in the same proportions as given above for neoprene latex. I may also use blends of such other rubbery materials in latex form with neoprene latex. However when latices of rubbery material other than neoprene are used it is necessary to include the conventional vulcanizing ingredients in the composition and to cure at a temperature sufficiently elevated; to effect vulcanization of such other elastomeric material. Such temperatures are considerably above those required when neoprene is used as the sole rubbery component of the formulation` As explained above simple drying of the neoprene formulations at temperatures only sufficiently elevated to effect removal of the Water is all that is required. Neoprene gives a much better product than the other rubbery materials. When a neoprene latex by itself is airdried it gives a tacky film but the combination with the resorcinol-formaldehyde resin as described herein gives upon air-drying a tack-free lm; with latices of other elastomers such as GR-S this reduction of tackiness by the resin is not nearly so pronounced. For these and other reasons, neoprene is by far the preferred elastomer. Y
While I much prefer to use resorcinol in the practice of my invention, I may use equivalent proportions of pyrogallol which gives a resinforming Vreaction substantially the same as that described above for resorcinol. Resorcinol and pyrogallol are similar, both being polyhydric phenols having hydroxyl groups in the 1- and 3,-positions on the benzene ring, pyrogallol differcomposition which when shaped, allowed to go' ing from resorcinol in having the 2-position also occupied by hydroxyl.
Instead of pure resorcinol, I may with substantially equivalent results use commercial resorcinol which contains related phenolic bodies as impurities and usually contains at least of resorcinol.
Instead of formaldehyde I may use equivalent proportions of other water-soluble aldehydes capable of giving the resin-forming reaction With resorcinol or pyrogallol. Examples are other aliphatic aldehydes such as acetaldehyde, propionaldehyde, butyraldehyde, etc. I may even use furfural although when it is used I prefer to use it only in making the partially condensed water-soluble resin and to use an aliphatic aldehyde such as formaldehyde or a homolog thereof in the formulation to complete the resin-forming reaction. I may use one aliphatic aldehyde in the initial resin-forming reaction and use another in the formulation to carry this reaction to completion; thus I may employ formaldehyde in making the partially condensed resin and then a homolog such as acetaldehyde or propionaldehyde to complete the reaction; or acetaldehyde first and then formaldehyde to complete the reaction; or propionaldehyde first and then formaldehyde or acetaldehyde.
I prefer to use resorcinol in conjunction with formaldehyde both for the partial condensation and to complete the resin-forming reaction or in conjunction with furfural for the initial condensation and formaldehyde to complete the condensation.
The mixture of the fibrous material and the aqueous binding mixture must be given its nal shape prior to the occurrence of gelling because material shaped from the mixture aft'er gelling has begun or is completed will not have enough strength to be useful.
The relative proportions of fibrous material and aqueous binding composition employed in manufacturing a fibrous board in accordance with my invention may vary widely depending upon many factors including physical characteristics desired in the board, type of fibrous material used, etc. The amount of binder should be sufficient to produce a strong, coherent board capable of standing up during handling, installation and use. I have successfully used the binding composition in a proportion such that the amount of elastomer plus partially condensed resin ranges from 20 to 70 parts by weight per parts of the brous material such as wood fiber and ground cork. Use of from 20 to 40 parts of elastomer plus resin per 100 parts of wood fiber and ground cork gives a mixture which can be troweled and thus easily shaped into the desired board-like form.
I have found that formulation of a mixture consisting of approximately equal parts of wood bark fiber and ground wood bark cork and an aqueous elastomer-partially condensed resin binding composition in relative proportions corresponding to from 20 to 40 parts of elastomer plus resin per 100 parts of the fibrous material, the relative proportions of elastomer and resin being such that the polyhydric phenol content of the resin ranges from 3.8 to 16.8 per cent by weight based on the Weight of elastomer and the concentration of elastomer plus resin in the aqueous mixture surrounding the fibrous material following intermixture being at least 30 per cent by weight of said aqueous mixture, gives a 9 through the: gell stage and dried; yields ea-A compact boardV which lends itselfas a backing mate'- 'ral or panelingl `material and. can bei Lutilized in furniture orain the building trade. I: believe that the great shrinkage 'of the-aqueous binding l material, A when it is- Aemployed iny such proportions, effects compaction `ofA the fibrous material during the drying step. Ihave observed that there is about l to 11% llinearshrinkage'of the mixture during drying and that this shrinle age compacts -the ber; Thislgreatshrinkage enablesme to obtain a compact boardwitho-ut'the necessity of using expensive highpressdreplaten presses. Thus I can simply place the wet intermixture of brous material and binder between 'screensor like perforated surfaces allowing escape of `water and hold it there'untiigeilingand drying are accomplished In making sueh-k -a hard, compact board, it is desirabley to leave the top. and bottom ofthe form asI -Wel1- as `the sides f free so as to enable these to follow'the shrinkage ofthe-materialtv v The technique deseribedvin '-thepreced'ing-par graph requires only 4very simple and# inexpensive Lequipment' Vandthe application of vno positive external mechanical". pressure. Although' the shrinkage upon gel/ling and drying ofA the f aqueous.) neoprene-partially condensedi-- resorcinolformaldehyde composition byy itselfL .or with the ordinary fillers andpigments but withouteinter- `mixture of alarge-proportion of nbrousmaterial is? often so excessive -as toprecludes--the vproduction therefromuof useful articles-thicker than one-fourth of an inch, nevertheless-the present inventiontakes advantage of4 this great shrinkage to; obtain an. unexpected resulti namely '-the production i of a-= compacting action-- whicha eliminates the; lneed of i highpressure `equipment :and yields a useful product even when made in Agreat thickness'say upto three-fourthsofan inch. orleven greater. Infother words rshrinkage impcsesrno limitation on thickness of the` boardproduceelaby my invention, Atheonly limitations oni-:thickness of my. board-s being-thatimposedfby-the=dif`u`culty of drying. extremely thickf boards.- Fora thin boa-rdi the particle 'size` of theJ ber' Ilimits `the -thinness -ofithe board'. f
I havevfurther fou-ndi that by: incorporation` of ya minorfproportionf cottonor rayon l fiber: into the.y composition .dl-ascribed abovegV a` much-less compact board'isobtainedi Thisembodiment of my invention is especially-valuable where aboard having Va rather. lou/weight `per-square foot characteristic .and a ratherwpcrous: and loosely` connectedistructurefor the purposeof sounctdead ening and temperature insulation'isdesired.` For this` purposeI may incorporate .into thesformulation from 5 i tor 20% by weight based: onL the weight of .other fibrous material, such asamixture of wood ber and cork, of ground wasteicellulosefbers, preferably the vfibersA thatffarereclaimed from old tire carcasses madeffrom cotton or..rayon .byY vcrackingror grinding tiresito'- about to. .1@ inch `particle size, then passing this ground material through-avmechanical device that' .beats` the. liber free fromr the rub-ber: and separates it; by air suction. Suchnb-ers mayfbe described.I as Acotton and/or` viscose. rayonfiber i' composed of a vmixture of twisted :cordand shredded.` singlet strands both' spunandilunspun r i in.various1.lengths, the ber length=varyin`g from 1/4' to.l inch Vwith' the .bulk around .1/4` inch. The use; of such; a. .minorinproportionI` of short-l'ength (lengthrgenerally averaging il@ of :anrinc-h) cel-.- lulose.` textile; f. bers produces .unusual results;
yielding amore-porous; muchfless com-pactboard than the same composition 1from-which ^such fibers are omitted. Atithei same time the lighter board so obtained has suicient strength and other'c-haracteristics adapting itv to use-as aicon- `s tructional material: The resulting board -canbe laminatedvvith various materialsV sucl'ras` a resinoussheet orproducing awall-v panel that can be; directlyapplied tothe studding of a building and" become 'parir of the building. Thisboard, like the vmore compact-i board obtainedV without the' cotton or rayon;is-flameresistanh Instead ofreclaimed tire-cord; *I may use cotton orl rayon-'nook' or' any ot-her/form-'ofV shortlength- L substantially pure-cellulose ber, such *as cottonor;regeneratedf'cellulose textile fiberruniformly'dist-ri-buted throughout "the mixturel from whichthe boardr-ismade;4 However' from the standpoint' of cheapness- I prefer to use the waste tire fabric.` f
I am not'certainas to -hoW the intermixture ofthe minor proportion of cotton'or raycnfiber bringsabout the fresultdescribed. 'l Nevertheless such intermiXture-results in a substantialidimins "ishing'oi the compactingeifeot ofthe binder Without preventing formation of a lstrong, useful board; It may be that the cotton or rayon bers have a tendency to filter out vthe elastomersand resin constituents of the aqueous mixture and thus prevent the penetration thereof into. the wood ber andcork'v so that"afte`r dryingtlie resulting assembly `is intenocked" through.; face adhesion `of coated cotton or rayon fibers with th'W'ood fiber and cork` but due tothe lack of binder adjacent the latter sufficient voids are left therebetween to give a softer and more porous materiallending itself `touse as ai'heat insulating and sound absorbing material? It may be that the cotton'-or'frayon ber, being substantiallyi pure cellulose highly swellabiei by aqueous-f4 media is highly` ,swollen shy, the aqueous mixture and upon .dryingshrinks back to its originalsizaleavingvoids and holding su'cient- 1y someof the 'wood bers apart preventing .the binder from contracting upon drying, thus'.form ing a porous board. Thealkali,metalhydroxide condensing agent in ,the binding` Vmaterialyifoillcl accentuate such swelling. "Iheother fibers..pres-` ent SuchasWoQdJber 'andccorlaA being:- very impure, Woody ligninfcontaining cellulose which is relatively nonfswellable by aqueous mediasas compared to pure cellulose such as cottonpand rayon, would' not *undergo suchH great swelling and subsequent shrinkage leaving voids;V 'In the preferred practice of my inventionno positive external mechanical. pressure'is applied to the shapedmixture during the gelling yand drying steps, sole reliance. being placed uponthe self-compacting Ynature of" the mixturetoieifect the production ofthe desired board having excellent strength and others physical properties adapting; ivt to. structural uses and having the desired degreeofcompactness. l,
I n the accompanying ,dravvingvvhich is largely self-explanatory, Fig. 1, is a flow diagram of the process of making the board, Fig. 2 portrays a compact boardmadeasdescribed inzyEXample 1 belowsands Fig... 3.1:xortraysY a relatively porous board made iii-.identcali. manner =.ton `\the=board of Fig. 2fexept with.the-incorporationof 102%L-#by weight` ofground. cellulose textile fiber obtained from reclaimed tire carcasses as described-lin Example'2wbelow. The looser, more porous texturelofth'e lboard as a result of the intermixture :11 of the cotton or rayon bers will be apparent from inspection of Fig. 3.
EXAMPLE 1 To approximately equal parts of wood fiber and of ground domestic cork, both derived from vthe bark of native evergreens, was added about by weight thereof of water and the materials -were mixed until a uniform mixture was obtained. There was then added an aqueous mix- Lture freshly made as described below. The relative proportions were such that for each 100 parts .of wood fiber and cork there was employed 100 parts of said aqueous mixture. Since the aqueouswmixture .contained 28.2% neoprene and 5.05% Yof resorcinol-formaldehyde resin, there were employed 33.25 parts of neoprene plus resin per .100 parts of the fibrous material. The resulting materials were mixed to a uniform condition and the mixture which had a troweling consistency was placed in sheet form between screens, allowed to stand for minutes and then dried at 12S-150 F. A strong, compact ibrousboard illustrated in Fig. 2 was obtained.
' The aqueous compositionused to' form the binder was prepared from four separate recipes, identified as A, B, C and D which were admixed together, just prior to use, in the following proportions by weight.
'Parts by weight Recipe A t 200 Recipe B 40 Recipe C 6 Recipe D 110 Recipes A, B, C and D had the following compositions: v
Recipe A This was an aqueous neoprene latex containing 75; vof dispersed polymerized chloropene.
Recipe B Per cent 'by weight Zinc oxide 12.50 Casein 1.25 Conc. NH4OH(29.4% NH3) 1.25 -Phenyl beta naphthylarnine v 5.00 Lithopone 30.00 Sodium salt of short chain alkyl naphthalene sulfonic acid 1.25 Water 48.75
, Recipe B was prepared as follows: The casein 'and ammonia were added to 20 parts of water. The mixture was ball-milled one hour. There- Vmaining ingredients were then" added and the mixture ball-milled for a minimum of 8 hours. The resulting dispersion was stored in such a way as to permit agitation suiiicient to prevent Crushed ice 188 A lbs;
441 ibs. '1oA oz.
12 Recipe D was prepared as follows: 'The resorcinol was placed in the water which was at a .temperature of approximately 150 F. After mix- EXAMPLE 2 Example 1 was duplicated exactly except that there was included with the wood bark fiber and ground cork 10% by weight thereof of ground cotton and viscose rayon cellulose fiber obtained from tire carcasses in the rubber reclaiming operation. The resulting board had the looser, more porous structure indicated in Fig. 3 of the drawing and was eminently suited for sound absorption and thermal insulation use.
From the foregoing, many advantages of the present invention will be apparent to those skilled in the art. The principal advantage is that a name-resistant building board having good strength is produced in a simple and economical manner. Another advantage is that the mixture is self-compacting during setting so that a compact board in the case where the cotton or rayon liber is not used and a somewhat less compact board, though still sufficiently compact for the purposes required where `such cellulose fiber is used, are obtained While subjecting the mixture to substantially no external pressure during its formation, i. e. after shaping and during the gelling and drying steps. 'This elimination of the necessity of subjecting the mixture to external mechanical pressure while it is taking its set is highly advantageous because the manufacture is thereby greatly simplied and accelerated and the equipment investment is much lower since mere placement of the sheeted material between foraminous surfaces such as screens is all that is required in contrast to the complexity and expense of using high pressure platen presses. Another advantage of the present invention is that the mixing of the aqueous binder mixture with the fibrous material to obtain a uniform homogeneous mixture is greatly facilitated by the form of the aqueous mixture used to form the binder, in comparison to prior art methods of making wall-board or the like using a powdered binder which is extremely dicult to distribute uniformly around each fiber and throughout the fibrous mass. Numerous other advantages of my invention will be obvious from the foregoing description.
All parts and percentages referred to herein are by weight.
Having thus described my invention, what I claim and desire to protect by Letters Patent is:
1. A fibrous board comprising a mass of fibrous material comprising randomly interlaced fibers bonded together by a bonding medium comprising the dried gelled residue of an aqueous mixture comprising dispersed polymerized chloroprene and dissolved partially condensed resorcinolformaldehyde resin capable of setting upon removal of water to a substantially infusible, substantially insoluble state, said mixture containing said polymerized chloroprene and said resin in such relative proportions that the resorcinol conassortis by weight basedV on the weightof said. polymerized chloroprene andcontaining at least 30 per cent by `weight of said polymerized chloroprene and said resin.
2. A fibrous board .composed essentially of a mass of shredded wood liber and ground cork bonded together vby a bonding. medium compris,-
ing the dried gelled residue of an aqueousmixture comprising dispersed polymerized. `chloroprene and. dissolved partially .condensed resorcinolformaldehyde resin capableV of setting uponremoval of water to a substantially infusible.. sub.- stantially insoluble. state, saidy mixture containing. said polymerized ,chloropreneand saidresin in such relative proportionsthat the resorcinol content of said resin ranges from3.8.to 16.8 per cent by weightbased. onthe. weight of, said polymerized chloropreneand containing at. least. 3) per cent by weightv ofv said polymerized chloroprene andsaid resinthe weight` vof' said polymerized chloroprene and said resin rangingfrom 20.to 70 parts per 10Q partsof said woodber and. ground cork.
3. A brous board comprising a massY of fibrous material 'comprising shredded wood ber and ground cork having uniformly distributed therethrough a minorproportion of short-length cellulose textile iber, said brous material being bonded together by a bonding medium compris- Ving the dried gelled residue of. an aqueous mixture comprising dispersed polymerized chloroprene and dissolved partially condensed resorcinol-formaldehyde resin capable of setting upon removal of water to a substantially infusible, substantially insoluble state, said mixture containing said polymerized chloroprene and said resin in such relative proportions that the resorcinol content ofsaid resin ranges from 3.8 to 16.8 per cent by. weight based on the weight of said polymerized chloroprene and containing at least 30 per cent by weight of said polymerized chloroprene and said resin, the, weight of said polymerized chloroprene and said resin in said composition ranging from 20 to 70 parts per 100 parts of said wood liber and ground cork, said board being substantially more porous, less compact and less dense than the same board from which said short-length cellulose textile fiber is omitted.
4. Aprocess of making a fibrous board comprising intimately mixing a mass of fibrous material comprising randomly interlaced fibers with an aqueous mixture comprising dispersed polymerized chloroprene and dissolved partially condensed resorcinol-formaldehyde resin capable of setting upon removal of water to a substantially infusible, substantially insoluble state, said mixture containing said polymerized chloroprene and said resin in such relative proportions that the resorcinol content of said resin ranges from 3.8 to 16.8 per cent by weight based on the weight of said polymerized chloroprene, said aqueous mixture containing after said mixing has been accomplished at least 30 per cent by weight of said polymerized chloroprene and said resin, shaping the resulting mixture to board-like form, allowing the shaped mixture to stand until 4said aqueous mixture has set to a friable solid gel state, and drying the resulting mixture to remove the water.
5. The process of claim 4 wherein said fibrous material is wetted with water prior to completion of admixture with said aqueous mixture.
6, A process of making a fibrous board comprising intimately .mixingy a .mass of shredded wood fiber and ground cork with an'aqueous mix;-
ture comprising dispersed polymerized chloroprene and dissolved` partially condensed resorcinol-,iormaldehyde resin-,capable ofsetting upon removal of water to a substantially infusible, substantially insolubleA state, said mixture contain: ing4 said polymerized chloroprene-.and said..` resin in such relative proportions that the resorcinol content of said resin ranges from 3.8 to 16.8 per cent. by weight based on the. weight. of said polymerized chloroprene, said aqueous mixture containing after said mixing has been accomplished at least 30 per cent by weightof said polymerized chloroprene and said resin, the weight of said polymerized chloroprene and said resin ranging from 20 to 70 parts per 100 parts of said wood fiber and ground cork, shaping the resulting mixture to board-like form, allowing the shaped mix.- ture to stand until said aqueous mixture has set to a friable solid gel state, and drying the resulting mixture to remove the water.
7; The process of claim 6 wherein said fibrous material is wetted with water prior to completion ofr admixture with said aqueous mixture.
8. The process of claim 6 wherein said mixture is subjected to substantially no external pressure during said gelling and drying steps and the mix.-v ture is. compacted throughv the sole agency of shrinkage which occurs during said drying.
9. A process of making a brousboard comprising forming an intimate uniform mixture of a fibrous material comprising a mass of shredded wood'ber and ground cork and a minor proportion of short-length cellulose textile fiber with an aqueous mixture comprising dispersed polymerized` chloroprene and dissolved partially condensed resorcinol-formaldehyde resin capable of setting upon removal of water to a substantially infusible, substantially insoluble state, said mixture containing said polymerized chloroprene and said resin in such relative proportions that theresorcinol content of saidresin ranges from 3.8 to 16,8 per cent by weight based on the weight of said polymerized chloroprene, said `aqueous mixture containing after said mixing has been accomplished at least 30 per cent by weight of said polymerized chloroprene and said resin, the weight of said polymerized chloroprene and said resin ranging from 20r to 70 parts per 100 parts of said Wood berV and ground cork, shaping the resulting mixture to board-like form, allowing the shaped mixture to stand until said aqueous mixture has set to a friable solid gel state, and drying the resulting mixture to remove the water and yield a board which is substantially less compact than the same board from which said cellulose ber is omitted.
10. The process of claim 9 wherein said brous material is wetted with water prior to completion of admixture with said aqueous mixture.
11. The process of claim 9 wherein saidmixture is subjected to substantially no external pressure during said gelling and drying steps and the mixture is compacted through the sole agency of shrinkage which occurs during said drying.
12. A process of making a fibrous board comprising intimately mixing a mass of water,- absorbent brous material comprising randomly interlaced fibers with an aqueous mixture comprising dispersed polymerized chloroprene and dissolved partially condensed resorcinol-formaldehyde resin capable of setting upon removal of water to a substantially infusible, substantially insoluble state, said mixture containing said polymerized chloroprene and said'resin in Ysuch relative proportions that the resoicinol content of said resin ranges from 3.8 to 16.8 per cent by weight based on the weight of said polymerized chloroprene, said aqueous mixture containing not over 25% by weight of saidpolymerized chloroprene and said resin, causing said fibrous material to absorb suiiicient water from said aqueous mixture during said mixing step that the aqueous mixture present on and around the bers after intermixture contains at least 30 per cent by weight of said polymerized chloroprene and said resin, shaping the resulting mixture to board-like form, allowing the shaped mixture to stand until said aqueous mixture has set to a friable solid gel state, and drying the resulting mixture to remove the water.
13. A fibrous board comprising a mass of randomly and initially loosely interlaced nbers bonded firmly together by a bonding medium comprising the dried gelled residue of a hardenable aqueous mixture comprising dispersed elastic rubbery composition selected from the group consisting of rubbery copolymer of butadiene and styrene in admixture with vulcanizing ingredients, rubbery copolymer of butadiene and acrylonitrile in admixture with vulcanizing ingredients, rubbery copolymer of isoprene and styrene in admixture with vulcanizing ingredients, and rubbery polymerized chloroprene, and dissolved partially condensed resin obtained by the partial condensation of a polyhydric phenol having hydroxyl groups in the 1- and 3-positions and an aldehyde and capable of setting in the aqueous condition to a friable solid gel and capable of being converted upon removal of water to a substantially infusible, substantially insoluble state, said mixture containing said rubbery polymer and said resin in such relative proportions that the polyhydric phenol content of said resin ranges from 3.8 to 16.8% by weight based on the weight of said rubbery polymer and containing at least 30% by weight of said rubbery polymer and said resin.
14. The process of making a fibrous board comprising intimately mixing a mass of randomly loosely interlaced fibers with an aqueous mixture comprising dispersed elastic rubbery composition selected from the group consisting of rubbery copolymer of butadiene and styrene in admixture with vulcanizing ingredients, rubbery copolymer of butadiene and acrylonitrile in admixture with vulcanizing ingredients, rubbery copolymer of isoprene and styrene in admixture with vulcanizing ingredients, and rubbery polymerized chloroprene, and dissolved partially condensed resin obtained by the partial condensation of a polyhydric phenol having hydroxyl groups in the 1- and 3-positions with an aldehyde and capable of setting in the aqueous condition to a friable solid gel and capable of being converted upon removal of water to a substantially infusible, substantially insoluble state, said mixture containing said rubbery polymer and said resin in such relative proportions that the polyhydric phenol content of said resin ranges Yfrom 3.8 to 16.8 per cent by weight based on the weight of saidV rubbery polymer, said aqueous mixture containing after said mixing has been accomplished at least 30% by weight of said rubbery polymer and said resin, shaping the resulting mixture to board-like form, allowing the shaped mixture to stand until said aqueous mixture has set to a iriable solid gel state, and thereafter drying the resulting gelled mixture and converting the same to a substantially infusible, substantially insoluble state.
REFERENCES CITED The following references are of record in the le of this patent:
UNITED STATES PATENTS Number Name Date 1,398,146 Novotny et al Nov. 22, 1921 2,087,942 West July 27, 1937 2,277,941 Almy Mar. 31, 1942 2,314,998 Lessig et a1 Mar. 30, 1943