Yoshino Gypsum Co., Ltd.

Hirokuni Tani

Seigo Ishibashi

Tatsukazu Kimura

Norio Tsuno

Kenichiro Osawa

Ushio Sudo

Wataru Nakamura

A mixer has a circular housing defining a mixing area for mixing and kneading of a gypsum slurry. A rotary disc is positioned in the housing and rotated in a predetermined rotational direction. A rotary driving shaft cointegrally connected with the rotary disc and a plurality of scrapers are positioned in the mixing area. A slurry discharge port is provided on an annular wall of the housing for feeding the gypsum slurry of the mixing area onto a sheet of paper for gypsum board liner. An opening of the slurry discharge port is divided into a plurality of narrow openings, so that fluid resistance on the gypsum slurry flowing out of the mixing area is increased. An annular basal part rotates integrally with the rotary disc and an inner end portion of the scraper is fixed to the annular basal part.

Mixer and mixing method for gypsum slurry

A plaster board including a plaster core having a front surface, a back surface, two opposite side surfaces and two opposite end surfaces and a covering base paper covering the front surface, back surface, and two opposite side surfaces, which core includes high-density hard edge parts including the two opposite side surfaces, at least one high-density part including the front or back surface, and having a density substantially equal to densities of the high-density hard edge parts, and a central low-density part having a density less than the densities of the high-density hard edge parts and the high-density part and being inscribed in the high-density hard edge parts and the high-density part, wherein each of the high-density hard edge parts is formed so as not to be present in the nailing area along longitudinal directions of the board in which a nail for fixing the board is driven.

Gypsum board

There is provided a lightweight plaster board having a cellular porous plaster core, excellent in adhesion to a covering base paper for a plaster board, free from dry-out in side edge parts of the plaster board, and with no disadvantage in workability for driving a nail into the plaster board. The plaster board includes a plaster core having a front surface, a back surface, and four side surfaces, and at least one covering base paper that covers the front surface, the back surface, and the at least two opposite side surfaces of the plaster core. The plaster core includes one or more hard edge parts each including one of the side surfaces covered with the covering base paper, one or more high-density parts including the front surface or the back surface, not including the side surface covered with the covering base paper, and having a density substantially equal to the density of the hard edge part, and a low-density part having a density less than the densities of the hard edge part and the high-density part and contacting with the hard edge part and the high-density part. The hard edge part does not include a position in which a nail is driven.

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Imabari, Japan

Hirokuni Tani