Patented Oct. \22, 1946’ 2,409,629 UNITED STATES PATENT OFFICE MANUFACTURE OF coa'ran BOARD Clark 0. Heritage, Cloquet, Minn.,a'ssignor to Wood Conversion Company, Cloquet, Minn., a corporation of Delaware No Drawing. Application September 9, 1939, ‘Serial No. 294,213 ’ 1 ' 6 Claims._ (Cl. 92—40) The present invention relates generally to coat ing compositions and to the use thereof. In par ticular it relates to the‘manufacture of arti?cial board with a coating thereon. It also relates par > 2 It is also an object of the invention to provide a coating composition for wallboard, which may be used in process of manufacture or after manu facture of the ?nished board per se, which main ticularly to such a coating applied during the tains its applied position and its covering power manufacture of the board. for ?bers. It is a particular object of the invention to Heretofore, considerable di?iculty has been en countered in attempts to produce coats on inher provide an aqueous coating composition so that ently rough surfaced ?ber boards, of vegetable it may be used compatibly with wet stock in the ?ber, of natural mineral ?ber, or ‘of synthetic 10 manufacture of board. mineral ?ber. To secure the desired color and It is also an object of the invention to use a permanence, it is necessary to cover entirely all coating composition which will withstand a high of the exposed surface ?bers. This may be done temperature such as to permit it to be dried by loading the surfaces to ?ll all the interstices simultaneously with a wet sheet carrying it in and to cover all the ?bers. However, this is waste 15 forming a board, and which is highly bene?ted by the action of heat on such drying. ful of coating material, and in addition it hides the texture of the uncoated board, which texture It is another object of the ‘invention to use a is often desired, not in the natural ?ber color permanent white pigment to form a coated board but in the same or other colors which may be of of high light re?ectance. more varied and permanent‘ character. It is'also an objectiof ‘the invention to provide 20 a coating composition and a coated board which Heretofore, formed ?ber boards, that is dry boards after formation, have been treated with ’ is washable with soap and water; which is re coating compositions in attempts to give new surface colors. There, are disadvantages in such sistant to scuff; which may be easily painted later with oil-paints without high absorption of practices. The composition either soaks in, or 25 the oil; which resists absorption of water; which if it ‘does not take well, the fibers are not wholly will not spot with water, and may be later painted covered. A fractional area of exposed vegetable ?ber readily affects the appearance and perma nence of the color in spite of the fact that the added color itself may be permanent in char acter. This is due to a change in color in vege table ?ber when it is exposed to light. Also, on with a water‘ paint; which will not cause warping of the board; which is cleanable with wall paper cleaners; which lacks odor; and which has gen erally desirable characteristics to provide and to maintain pigmented colored ‘walls or ceilings in a home, o?ice, hall or like quarters. » drying liquid coating compositions applied to dry Various other and ancillary objects and advan board, the board may be pulled into a warp by tages of the invention will become apparent from "stresses produced in the coat, if there is no vre 35 the following description and explanation of the straint in drying. Particularly, boards which are invention. made water-resistant when dry, do not take well The boards for which the coating compositions are most desirable are these-called insulating any aqueous composition applied to surface, unless it is copiously applied. A copious applica wall boards. For their practical uses, such boards 40 are required to be water-proofed or water-resist ' tion increases the warping tendency. The present invention provides a composition which may be applied to boards while they are ant. This is commonly done in process of manu facture by using an emulsion of a water-proo?ng agent such as a fat, oil, wax or metallic soap, ’ wet in process of manufacture, which takes well in both light and heavy usages to assure covering which will e?ect the result desired. Where wax 45 all the exposed ?bers, and which may be used is used as an emulsion, the emulsion is precipi in small quantity to leave the texture and coat tated, as with alum, and the precipitated'par the ?bers, or in higher quantity to coat the ?bers ticles on the ?ber do not attain their ultimate and partially ?ll the interstices, thus exhibiting function until the board is dry. Thus, a so— texture, or in still higher quantity which may 50 treated board when dry is resistant to an aqueous coating composition. Yet the same board in hide the ?bers and the interstices to form a smooth coat, practically hiding texture. process, while moist and lbefore drying, is not re It is an object of the invention to provide a sistant to such a composition. This is a very pigmented surface appearance on board with important distinction where low usage of coating complete coverage. of ?ber surface by the pig w material is desired. Under such conditions of ment, and with varying e?ects in appearance of low usage, the board surface (viewed microscopi texture due to variations in usage. cally) presents a brush-heap‘appearance, with 2,409,029 3 individual ?bers raised high from the body, and Example 2 with deep recesses de?ned by other matted ?bers of the brush-heap appearance. A‘ thin coat of material must adhere to the entire surface of the ?bers. Dry water-resistant ?bers tend to repel the composition leaving un'coated portions of ?bers, and forcing the composition to span the inter-?ber spaces. No perfect continuous color results, because of the uncoated portions of ?bers showing through. Such a board is not stable in color because of the photochemical and atmos pherically induced change of color in the exposed ?ber. To avoid uncoated spots on ?bers, high usage is required, which also has a ?lling action Parts by weight “Aquaplex" No. A-90 ____________________ __ 24 Water _____ __ 39 Pigment (such as titanium dioxide) _____ _'___ 36 Example 3 ' , Parts by weight “Aquaplex" No. A-90 ____ ___ _____________ _.. 34 Water _ 34 Calcium carbonate ___________ ____________ __ 32 The above composition of Example 1 is pre ferred. It contains about 45% water, and the on the pores or interstices. 15 proportions of solids to water are made such as Accordingly, it is most important to provide a coating composition which is susceptible to use to render the composition suitable for the process of application, which is speci?cally the use of a roll pressing on wet board (60% water) behind which roll there is a pool of the composition. for entirely covering all the exposed ?bers at very low usage. The composition requires a. pigment to give the 20 In the preferred composition of Example 1 color, and a vehicle therefor containing binder there are about 11 parts of binder to 44 parts of for binding pigment particles to each other and ' pigment, which makes a coating residue of about - to the ?ber. Mineral pigments are preferred, but 20% binder. These proportions are by no means any pigment which withstands the action of heat limitations, because the amount of water depends where it is encountered in the procedure chosen, 25 in part upon the workability of the process, and as for example, where the wet coated board is the proportion of binder to pigment depends in oven dried. part upon the kind and form of pigment. The The vehicle is essentially aqueous to assure a pigment however, should predominate, inasmuch loss of vehicle substance in drying the coating, as the intended coat is one of particles cemented to assure mutual wetting of wet ?bers and the 30 to each other and to ?ber, rather than a ?lm of composition, to avoid vapors of organic solvent vehicle in which the pigment is dispersed. material, and to lessen cost. With reference to the above pneferred ex The binder for the present invention is one ample, it is to be noted that the “Aquaplex" which may be dispersed in an aqueous vehicle, emulsion is diluted about 100% with water, and and which is set as a, binder at normal tempera 35 the pigment is ultimately dispersed in the diluted ture when dry, being either thermo-plastic or emulsion. The binder and the pigment are each heat-hardening. In other words, resins which largely suspended independently of each other in set on heating, as well as thermoplastic materials, the aqueous vehicle. are included. The binder may be water-soluble, The composition has high adherence and uni water-emulsi?able, or otherwise dispersible- in 40 form spreading power over wet ?bers, with or water. It may be a synthetic resin not in ?nal without a latent water-proo?ng compound, such reacted form, a condensation product capable of as paraf?n precipitated from emulsion in the ?ber further reaction with itself or some other ingredi slurry which forms the board. In high usage it ent, or it may be a mixture of materials which also has adherent power to dried ?bers with or react after application to the board. For exam 45 without the water-proo?ng treatment. But in ple, it may be monomethylol urea, or dimethylol low usage it does not adhere uniformly to the ,urea, or some water-soluble mixture or product ’ of urea and formaldehyde. It may be an emul dried water-proofed board. By applying the preferred composition to moist sion of phenol-aldehyde resin, or the alkyd resins or wet board before the ?rst drying, light to which are thermo-setting with increasing tem 50 heavy usage may be employed with variable re perature. Certain polymerized esters of alcohols sults as desired. By drying the coating and the and acrylic acid are water-soluble before the board together, the tensions resulting are such water is driven off, and insoluble thereafter, and that the coating, even though it is thick, does not hence, although thermoplastic, are suitable for pull the board into a warp. use. The thermoplastic binders are not so uni 55 versally useful as the heat-setting resins, since the former call for too careful action at the ele vated temperatures where the binder is soft. Preferably, the heat-setting products are used which harden at high temperatures. 60 Emulsions of resins which are heat-setting are available on the market. One such is termed The coating may be applied by brushing, by spraying, by roll transfer, by roll and pool, or by doctor blade, according to desire. The viscosity of the coating is pertinent to the method of applica tion, and it may be controlled by varying the wa ter content, or the binder content, or both, or the kind or form of the pigment. For example, a composition which is suitable for application by “Aquaplex” No. A-90, manufactured by Resinous a pool behind a roll, is suitable for application Products 8: Chemical Company, Inc., of Philadel by spraying, but every composition which is suit phia, Pennsylvania, and it is a glycerol-phthalate 85 able for spray-coating is not suitable for the roll carried in aqueous suspension of 40% solids. It and pool method. sets on losing water, as by drying, to an irreversi The effect of viscosity is exempli?ed by refer ble form. At elevated temperature setting prop ence to the use of a pool behind a roll. In such erty is enhanced. use the moist mat approaches downwardly the 70 nip of two rolls and passes through with the Example 1 formation of a pool of coating composition on the Parts by weight mat behind the top roll. The moisture in the mat “Aquaplex” No. A-90 ___________________ __ 28 and ?bers assures that the ?bers are wettable Water ___ by the composition, and the covering pool assures 28 Pigment (such as titanium dioxide) _______ __ 44 75 perfect contact. 2,409,029 . The pressure of the upper roll is controllable in the degree-with which it compresses the mat. Thus it effects a forcing of the composition well into the surface, controls the amount which is squeezed back into the pool, and hence controls the amount left on the mat. The ?bers at the top spring back and carry with them a perfect coat of pigment. In such springing back, the pores tend to suck in any free liquid. Where a 6 ‘ _ (thick-boiled as in laundering) may be used as an under-coat, ?lling the pores and sizing the ?bers, and while the board is still wet with such starch solution, the pigmented aqueous composi tion may be applied, as if no sizing were present. In the speci?cation and accompanying claims where reference is made to binding the particles of pigment to the ?ber, it is to be understood that the ?ber may be sized before or after the mat is light usage is employed, the ?bers rather than the 10 formed, as described, or not at all. void spaces select the composition. Where heavy From the foregoing it will be understood how coats are used, the interstices are comparably the invention may be varied within the scope of ?lled. »~ the appended claims. In drying, the mass and the ?bers shrink in suf . I claim: ?ciently close degree to maintain a complete coat 15 1. The method of making a coated rigid porous on the ?bers, and to ?ll the interstices as the structural ?ber board which comprises ‘coating a quantity permits. In practice the coated mat is wet structural-board-forming mat of ?bers with dried at 310° F. to 345° F. Thus, moisture is prac a composition having su?icient pigment to hide tically boiled out of the board. In light usages, the surface ?bers, and having an aqueous vehicle the interstices being not sealed, permit the water 20 in which is dispersed a heat-reactive binding ma vapor to escape. Where the composition is pre terial capable of binding the pigment to the ?ber sent to such an extent as to seal the pores, micro and to itself, said binding material after reaction scopic craters may be found where the steam by heat being set when dry at normal temperature blows out. However, these craters do_ not alter and exerting anadhesive action at an elevated the continuous colored or white appearance of 25 temperature at least prior to completed thermal the surface. reaction, and drying the mat and the coat thereon The drying of the preferred composition at the simultaneously at an elevated ‘temperature to elevated temperatures sets the binder to insoluble form the board. ' infusible resin form. Where the given composi 2. The method of making a coated rigid porous tion is spread upon the board at a usage of 57 lbs. 30 structural ?ber board which comprises coating a of composition (or 25 lbs. of pigment) per 1000 wet structural-board-forming mat of ?bers with sq. feet, a board is obtained as follows: a composition having sufficient pigment to hide the surface ?bers, and having an aqueous vehicle . Initial light-re?ectivity is 78%. in which is dispersed heat-hardening binding . Color-high white. . Permanent against discoloration. . . A substantial retention of porosity and sound absorbency (due to craters). ~ . Matted surface is retained, giving dull effect lacking glare. ‘ . Texture is unaltered by coating. 35 material capable of binding the pigment to the ?ber and to itself, and drying the mat and the coat thereon simultaneously at an elevated tem perature to form the board. 3. The method of making a coated water-resist 40 ant rigid porous structural vegetable ?ber board . Surface readily redecorated with oil or water which comprises forming a water slurry of wet vegetable ?bers carrying a water-proo?ng agent deposited thereon, forming said slurry into a wet 9. Coating is continuous except for microscopic the exposed ?bers of said mat and having an . Surface is resistant to cleaning, washing, and scu?lng. structural-board-making mat, coating said wet .base paints, lacquers, etc., without undue ab 45 mat with a composition having pigment to cover sorption. aqueous vehicle in which is dispersed heat-re craters. active binding material capable of binding the There are commercially available water-dis pigment to the ?ber and to itself, said binding persible compositions of other resins suitable for 60 material after reaction by heat being set when dry use in the present invention. Heat-hardening at normal temperature and exerting an adhesive phenol-aldehyde resins are so available. Heat action at an elevated temperature at least prior hardening urea-formaldehyde resins are also to completed thermal reaction, and drying the mat available. . and the tcoat thereon simultaneously at an ele It is a practice in making boards to add ?ller 55 vated temperature to form the board. or sizing material to the stock so as to leave the 4. The method of making a coated water-resist same in the ?nished board, for example, a col ant rigid porous structural vegetable ?ber board loidal starch. This may be done with the stock which comprises forming a water slurry of wet of which the mat is to be coated, without in any vegetable ?bers carrying a water-proo?ng agent way interfering with the invention as described. 60 deposited thereon, forming said slurry into a wet Also, where such filler is or is not present, the 'structural-board-making mat, coating said wet surface of the wet mat may be sized with the mat with a composition having pigment to cover same'e?'ect by wetting the formed board with a the exposed ?bers of said mat and having an aque thickened sizing solution, such as gelatine or ous vehicle in which is dispersed heat-hardening other protein, or starch or the like. This pene 65 binding material capable of binding the pigment trates into the surface for a limited distance, so to the ?ber and to itself, and drying the mat and that on drying the board, the so-treated surface the coat thereon simultaneously at an elevated is harder and more resistant to scu?‘. Such size temperature to form the board. more readily enters the board than the coating 5. The method of making a coated water-resist- . composition with its load of pigment. By using 70 ant rigid porous structural vegetable ?ber board such size preliminarily to using the composition, which comprises forming a water slurry of wet more of the binder of the composition remains in vegetable ?bers carrying a water-proo?ng agent the pigment coat. Thus, where a more expensive deposited thereon, forming said slurry into a wet binder, such as synthetic resin is employed, its structural-board-making mat, coating said wet quantity may be reduced. A starch solution 75 mat with a composition having pigment to cover 2,409,629 8 the exposed ?bers of said mat and having an aque ous vehicle in which is dispersed heat-hardening alkyd resin capable of binding the pigment to the ?ber and to itself, and drying the mat and the mat with a composition having pigment to cover the exposed ?bers of said mat and having an aqueous vehicle in which is dispersed heat-hard coat thereon at an elevated temperature to form to itself and to the ?bers, the quantity of com the board. 6. The method of making a coated water-resist ening alkyd resin capable of binding the pigment position applied being su?icient when dry to seal the pores of the board, and drying the mat and the coat thereon simultaneously under conditions ant rigid porous structural vegetable ?ber board which comprises forming a. water slurry of wet to boil oil’ water in the mat, whereby microscopic vegetable ?bers carrying a water-proo?ng agent 10 steam craters are formed and set in an other deposited thereon, forming said slurry into a wet wise continuous coat on said board. structural-board-making mat, coating said wet CLARK C. HERITAGE.