Abstract: The present invention provides a method for manufacturing a calcined gypsum wherein the mixing water amount is reduced and the setting time does not increase. As a raw gypsum is compounded with a carboxylic acid-type material and calcined, a calcined gypsum can be manufactured wherein the mixing water amount is small and the setting time does not increase. Furthermore, a regular gypsum board can be manufactured without reducing the productivity of the gypsum board even if a large quantity of recycled gypsum causing increase of the mixing water amount is used as a raw gypsum, because the mixing water amount is small and the setting time does not increase for the calcined gypsum manufactured as described above.

Abstract: The present invention provides an apparatus and a method for fractionating gypsum slurry which can surely control the density of the gypsum slurry fractionated from the mixer (fractionated slurry), which can restrict change of the flow rate of the fractionated slurry, and which can reduce the consumption of foam or foaming agent. The fractionation apparatus (30) fractionates the gypsum slurry from a mixer (4) for mixing calcined gypsum and water. The mixer has a hollow connector section (50), which allows the gypsum slurry to flow from a mixing area inside of the mixer into a chute section (5), and the chute section (5) discharging the inflow of gypsum slurry through its slurry discharge port onto a gypsum board liner paper. The fractionation apparatus has a slurry fractionation port (33) opening to the chute section or the hollow connector section, and causes a part of the gypsum slurry in the chute or hollow connector section to be delivered to a slurry delivery conduit (11,13,19).

Abstract: A gypsum-based building material comprising gypsum as the main material and an anthraquinone compound incorporated.

Abstract: Provided are a process and an apparatus for producing gypsum boards, both of which feature minimized occurrence of defective products and especially excellent continuous productivity and superb efficiency. Making use of the facts that lining paper sheets for gypsum boards are insulators and a gypsum slurry held between the lining paper sheets is a good electrical conductor, a detection of an electric current flowing between an upper forming unit and a lower forming unit or a like method makes it possible to promptly detect any localized tearing which may occur in the overlay paper and/or underlay paper due to an undesired object or the like mixed in during continuous production of gypsum boards and moreover, to readily remove the undesired object or the like as a cause for the tearing without stopping the production of gypsum boards while preventing the localized tearing from spreading over the entire width of the paper.

Abstract: A mixer 10 comprises a disc 32 having peripheral edge 35, which is formed in a circular profile concentric with inner circumferential surface 25 of annular outer wall 23; lower pins 50 provided with rear bulged portions 73 extend backward of the rotational direction R; and upper pins 60 provided with front bulged portion 72′ which extends forward of the rotational direction. A disc without a toothed formation on its peripheral edge zone can prevent the slurry from depositing on the outer periphery of the disc. Front and rear bulged portions 72′, 73 occupy a rearward area of the lower pin and a forward area of the upper pin so as not to provide retentive regions for the slurry, which might otherwise have caused a vortex or turbulent flow of the slurry. Accordingly, the deposition of slurry on the lower and upper pins can be prevented from occurring.

Abstract: There is provided a partition wall which is characterized in that studs are secured to upper and lower runners fitted to a substrate in a zigzag arrangement or as common studs; that basic face materials are fitted to the skeleton through sound insulation materials so that the face materials are arranged, in parallel, on both outer sides of the studs, while the studs are internally positioned; and that a hard gypsum sheet comprising fibers dispersed in the gypsum core thereof is arranged on the corresponding outer side of each basic face material. This partition wall is particularly suitable for use as a dry party wall, has satisfactory characteristic properties such as fire protecting properties, sound insulation properties, deformation-follow-up properties, out-of-plane flexural rigidity and hardness. The wall comprises gypsum based construction materials as the top end boards and thus the weight and wall thickness thereof can be reduced.

Abstract: Novel and improved paperboards useful for making gypsum wallboards, which are sized with a specific organopolysiloxane comprising mercaptoalkyl containing organosiloxane units and, optionally, methacryloxy-containing organosiloxane units in its molecular structure. The sizing compound is used in a relatively small amount and yet can exhibit an excellent effect within a very short time. The sized paperboards have adequately controllable moisture absorption as well as air permeability. They are used to cover or sandwitch a gypsum core to form a complete wallboard in a convenient and economical manner.

Abstract: A water repellent gypsum composition comprising a gypsum, and a paraffin emulsion prepared by emulsifying (a) paraffin hydrocarbon having a melting point of 40.degree.-80.degree. C and (b) an oxidized paraffin having an acid value of 10-70 at a ratio of from 97:3 to 50:50 by weight, respectively, in the presence of a water soluble alkali compound. Optionally, a polymer emulsion or solution may be added.