Document oMyovB511QZ81MQ0Xk2woO727

BEST WALL GYPSUM COMPANY GYPSUM WALLBOARD MANUAL Section 3 1965 EDITION MANUFACTURE of GYPSUM WALLBOARD and GYPSUM LATH Board Products* 1 Gypsum Wallboard, Lath and Sheathing are composed of a core, hydrated calcined gypsum fibers and other ingredients, surfaced on both sides with smooth, uniform, specially-prepared paper forming the finished surfaces and serving as a reinforce ment. Each raw material used in the manufacture of these products is for a specific pur pose, and only those that meet our rigid specifications are used. The quality and structural value of each board product depends upon its composition and fabrica tion during manufacture* To thoroughly understand the quality, properties, uses, etc c, of each product, its composition and manufacture should be known. There fore, the manufacturing may best be followed by starting with the raw materials and following their course, step by step, through the process. 1. RAW MATERIALS (a) Paper; Bestwall manufactures in its own paper plants, most of the special paper used for surfacing wallboard, lath and sheathing. A different kind of paper is used for each finished product. Bestwall*s three paper mills are located at Pryor, Oklahoma; Thorold, Canada; and Delair, New Jersey. Some paper, as necessary, is purchased from out side sources in accordance with our own specifications. The papers are manufactured on seven or eight cylinder paper machines, which means that there are seven or eight separate layers of paper stock felted together to form the solid finished sheet. The finished sheet as formed consists of 3 parts which are known as the face liner, filler, and bond liner. By building up the solid sheet in this manner, the composition of each part of the sheet can be controlled so as to produce a paper which will have the properties required by the finished gypsum board products. All papers used for wallboard, lath and sheathing have certain pro perties in common: 1. The bond liner in all cases is made from unsized stock and is designed to produce perfect bond to the gypsum core. The bond to the gypsum core is accomplished by the bond liner absorbing the saturated gypsum solution from the gypsum slurry used for forming the core. Gypsum crystals grow in this saturated solution that has been absorbed by the bond liner and Interlace into the cry stals of the core, thereby producing the bond. SGP 0025234 G^PST1 HILLPOA1T 1'*A'n'\L 196 Edition 2- - Manufacture of Oyosum 1?ailboard & Ggosum Lath (Contlnv.ee1) Section 3 2. The filler of all our paper is rra^e from a specially-treated (sized) paper stock to render it water resistant. The water resistance of the filler is very important. It is one of the features of the paper which we use for all types of board, lath and shea thine. The filler is designed to prevent the free water present in the slurry and core from percolating through the face and back capers to the surfaces while the board is being manufactured. If this water filtered through the face and back papers, it would cause unsightly water narks, stains, etc. on the .-fi nished sheet. The water resistant filler in lath caper prevents the passage of free water present in gyosum plaster mortar when it is applied on the sur face of gypsum lath, from passing through the covering paper into the core of the lath. 3. The face lin r used for wallboards is made from a special pacer stock which is colored, highly sized, and treated to render it water and scuf resistant. The finished surface is smooth, uniform, and nonabsorptive. The face liner of lath paper is water absorbent exactly the same as the bond liner (as explained in 1 above), because its surface must have the properties of bonding to the gypsum plaster applied to the lath. The face liner of gray wallboard back paper is made from stock that is slightly sized so as to render it scuff-resistant,, The face liner of the pap^r used on sheathing is made from paper stock which is colored black, highly siz^d, and treated to render it water resistant, and scuff resistant. The finished surface is smooth, uniform and nonabsorptive. (b) Stucco: The stucco used for manufacturing the core is designed especially for this purpose. It is of proper fineness and is low in water cariying capacity. This produces a core which has the proper hardness and strength. (c.) Glass 'Tiber: The glass fib^r used in Bestwall gypsum wallboards is the continuous textile i-raHe which is soft and non-irritating to the skin. It has a very high tensile strength, being stronger than manv steels. It is obtained in multiple strands wound in spools, and is cut to proper length continuously in svnchronizativn with the belt speed of the boa1"'1 machine. The rtass fiber is used under Bestwall Gypsum Company's Patent No. 2,601,063. (d) Paper ^ber: Paper Fiber is used along with glass fiber in all lath and board products except Firestop bestwall, which contains only glass, lath and fiber. The paper fiber is scrap paper purchased from otviside sources or itfaste paper from the wallboard operation. The paper is beaten up in water in a hydro-pvilper in either a 2-|- or 3 percent SGP 0025235 C-'rpSLT' HtLLBOtRO 1965 Edition -3 - Section 3 concentration,* It is pumoed to the mincer by a variable speed pump which proportions the proper amount of paper pulp, depending unon he type of nroduct being made and the soeed of operation. The glass fiber and paper pulp are added to the core for the follow in'? reasons: 1. To give proper nailing properties to the core and to eliminate chinping and shattering of t. e core at open edges of the board. 2. To redu.ee the brittleness of the core. 3. To orocuce a wallboard that has the required flexibility and which can be handled rnLthout breakage. Lu To rnch.ce the weight of the board. (e) Adhesives: The gypsum crystals which form the core and bond it to the bond liner of the oaoer used are vera fine and brittle. To protect these cry stals, and to add to the bond between the core and the bond liner of the paper, a special adhesive is used. This adhesive is mixed into the ingredients in the core. It is water soluble and, therefore, concentrates between the gypsum crystals where the core is in contact with the bond liner. This reinforces the crystalline structure and adds to the bend between the core and the paper covering. This con centration of the adhesive at the surfaces of the core is somewhat similar t the action of the soluble gum addad to produce the casehardened surfaces of statuary casting plaster. (f) Accelerator. The gypsum ore must be set hard by the time the board reaches the cut-off kni b, which is near the end of the board machine, so that the board c. r be cut into the required lengths. This makes it necessay to use an accelerator to rgulate the setting time of the slurry. The accelerator which we use is ordinary pulverized gypsum rock. Chemical accelerators such as potassium sulphate, anmoniu.m sulphate, etc. nisy a'^cbe used. (Foam: The foam added to the slurry used for producing the core is mar'e from a solution of rosin soap or other foaminn agent. This solution is passed through special eoyipment that beats it into a stable, uniformstructured, small-bubble foam. The fcam produces microscopic air voids throughout the gysum core. The soap solution reacts with the gy psum to form insoluble calcium salts itiich further reinforce the void structure of the gypsum core. Foam is added to the slurry to: 1. Increase the thermal insulatioh value of the board. 2 Reduce the brittleness of the core SGP 0025236 GYPSUM WALLBOARD MANUAL 1965 Edition. -h- Section 3 3 Add to the flexibility of the board* U Reduce the weight of the board. 2. PROCESS OF MANUFACTURE: Each step in the process of manufacture is carefully controlled to produce quality and uniformity in the boapd, lath or sheathing* Quality depends upon the combination of the face and back paper used and the structure of the core (the paper has been described above)* The paper and the structure of the core controls rigidity, structural strength and durability of the finished product. The required hardness and strength of the core ean be achieved by proper formu lation of the dry ingredients and control of the water-plaster rati% The proper mixing of the dry ingredients, the addition of the foam, paper pulp, glass fibers and the proper wet mixing before the slurry is poured onto the paper covering are all very important. A very rigid system of inspection, testing and control is maintained at all eur plants to make sure that the pro per percentage of each raw material is used, and that the mixture is thoroughly dry mixed and wet mixed before it io used for forming the core* (a) Dry Mixing: It is essential, to thoroughly mix the glass fiber, accelerator and adhesive into the dry stuceo so that a uniform mixture is obtained. Dry mixing is accomplished in the conveying equipment as the material is delivered to the wet end of the maohine. (b) Wet Mixing; The dry ingredients are fed into a high-speed p.eatrlfugal iixr and are blended with mixing water, paper pulp and foam* The c nsistency of the slurry is accurately controlled by regulating the ir.xing water through the use of a recording water meter. The wel ht of the slurry is controlled by varying the foam oontent as required to pro duce a slurry of a definite density. Slurry from the mixer is dis charged in three streams so that three streams of gypsum lath may be ra.de at one time. For other boards, the streams all blend to gether at the forming rolls except where two streams of sneathing are made in which case only two streams are used. (c) Edge Formation; SGP 0025237 Square Edge, Tapered Edge, Tongue & Groove Edge, and Beveled Edge Boards are made by cutting grooves along the edges of the face paper after it leaves the paper rack* The inside grooves regulate the width of the finished product. As the grooved paper approaches the forming rolls, it is folded into the various shapes along the grooves which are required for the particular type edge being made by means of edge folding devices. Spaces between grooves are set depending upon the type product being made and its thickness* Gypsum lath paper is not grooved along its edges (continued on next page) O.YPSIM IJA.LLRQA.RD MANUAL 1965 EDITION -3- Sect:W 3 but is passed through edge forming devices which fold the paper in a semi-circle on each side producing a "round11 edge product. As the papers pass through the forming rolls, adhesive is applied to each edge of the back paper which serves to stick the edges of the back paper to the folded edges of the face paper. (d) Thickness: Thickness of the various products is controlled by the spacing of the forming rolls* (e) Length of the Machine: As the gypsum board or lath leaves the forming sectj on, it is carried on wide rubber belts and carrier rolls to allow time for the gypsum core to harden (set) The total length of the machine depends to a considerable degree upon the speed operated. Our longest machine is at Brunswick where this distance is 9h9 fto (f) Cut-Off Knife: All plants use rotary knives for cutting the board into various lengths. The drive for the cutting mechanism is adjustable so that lengths can be varied as needed for various products. (g) Transfer Table: After the boards are cut to length, they are picked up by a trans fer table and carried sideways to a tipple table which feeds the boards into the dryer. The dryer runs parallel with and alongside the board machine. As 2|8" wide wallboards are transferred, they are inverted so that the ivory face is turned up. "his preserves the finish of the ivory paper from blemishes, slick spotB, etc. which may occur when the paper is in contact with t}e kiln rolls. (h) Drying The board from the transfer is fed by the tipple table into the dryer which has 6 or 8 decks, and is wide enough to take 2 streams of board U' wide, 3 streams 32" wide, b streams 2b" wide, and 6 streams 16" wide. Our dryers are heated either by steam coils or by direct combustion of natural gas. The temperature is carefully controlled in the various zones into which the dryer is divided so as to dry the products properly. Large circulating fans blow the hot gases over the boards arid' laths and the moisture which is evap orated is blown out through exhaust stacks. (i) Take-off: SGP 0025238 In all plants except Blue Rapids, wallboard products are grouped into pairs face to face automatically and conveyed through a bundling machine where the end tapes are applied. The bundled packages are GYPSUM WALLBOARD MANUAL 1965 Edition -6- Section 3, stacked automatically and handled to the warehouse or loading dock by fork trucks. Lath is handled on a separate system where it is bundled into 6 pieces to the bundle (5 at Sigurd). At Blue Rapids, board and lath are unloaded from the kiln by hand and fod into the packaging machines. (j) Pinholath Pinholath is made under exclusive license from the Pinco Co. under Patent No. 3,879,662. The pinholes puncture the paper and permit water from plaster applied thereto to be absolbed into the core in a controlled amount. This serves to rigidify the plaster next to the paper face and is designed specifically for use with machine applied plaster. (k) Perforated Lath The perforating is done by a punching machine at the end of the board machinej the operation being performed on the wet lath be fore it is cut into ii8" lengths. The perforations are 3/U" in diameter and spaced U" apart. (l) Reclaiming Department In this department, re-cutting equipment is available so that the damaged goods can be cut into smaller sizes and reclaimed for ship ment to the trade. (m) Loading Cars & Trucks Loading cars of wallboard, lath and sheathing is done under close supervision. All possible precautions are taken to insure delivery of board in good condition. To illustrate the precautions which are taken, here is the routine which is followed in loading cars: All cars are carefully inspected before they are accepted for loading wallboard, lath & sheathing. Any cars with leaky roofs, broken or unusually dirty floors, etc., are rejected. All loose nails are pulled from the floors & sides. Any loose boards are fastened to prevent damage to the load. After the cars have been cleaned and prepared, the floors are covered with dunnage board and the walls covered with paper. Only then does loading start. While loading the cars, paper pads are attached to the side of the cars to protect the ends & edges of the piles of board, lath or sheathing. Special care is used to brace, tie and protect the piles, and to prevent shifting or damage enroute. Wherever possible, gypsum board products are now loaded into box cars or on flat cars by fork lift trucks. By this method, whole units are set in place at one time. Spacers are placed between each unit so that the forks of the lift truck can be easily inserted and withdrawn. Flat cars are covered & the load held in place with steel strapping. SGP 0025239 GypsTT" ''v-.irwiT ''a-t-'al l?6g Edition -7- 5notion 3 3o IbP~'CTIO~T; All ra.iT materials and entire process of manufacture are under the super vision of competent inspectors. An ins '"'ctor is on duty at all times and on all shifts and is responsible for the qua lit'' of the products produced on that shift* 'nv~ry step in the process is checked hurly or at fixed intervals as a matter of control. finished boards are tested houbly or more often for thickness, width, length, bond, nailing propertiesp flexi bility, strength, weight, appearance, resistance to moisture, etc. All tests and inspections are recorded on standard report forms which are made up in duplicate, ^hese reports are watched by the board plant superinten dent as the entries are made throughout the day. The reports when com pleted are signed 1ry the inspectors an'1 turned over to the board plant superintendent and plant manager for approval. One copy of the report is sent to the Paoli Laboratory. These reports are carefully analyzed by all concerned and then filed far reference. SAJ'PLES: All samples of wallboard, lath and sheathin" are cut from standard pro duction at ^ort rodge where the sample department is located. SGP 0025240 SGP 0025233