JP3486440B2 - Method for producing a gypsum-based cured product - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a gypsum-based cured product used for building materials and the like. [0002] Generally, gypsum-based building materials are used as paper-plastered gypsum boards, fiber gypsum board plates formed by a papermaking method, thick hollow plates formed by an extrusion method, a casting method, and a press molding method. Interior materials and surrounding materials are known. The gypsum used as the main raw material is hemihydrate gypsum, but when mixed with water, it sets in a short time (5 to 30 minutes), starts to harden, causing inconvenience during production and the performance of molded products. A drop occurs. Also, since many are based on mass production methods, a large amount of raw materials are weighed at once,
After mixing and making into a slurry, temporarily store in a batch, weigh the desired amount again, and mold it with a molding machine, or transfer the raw materials of the batch little by little to the molding machine and perform continuous molding. Manufactures compacts. [0003] Therefore, in a production system in which hemihydrate gypsum is used as a main raw material and a large amount of raw materials are prepared at once, a setting retarder is usually used to control the pot life of the raw material mixture. (JP-A-62-41748)
No.). [0004] Examples of the setting retarder for gypsum include glycerin, alcohols, phosphates, carboxylic acids, oxycarboxylic acids or salts thereof, and many others such as amino acid derivatives. However, when these setting retarders are used, the pot life of the raw material is prolonged, but the setting start time of the molded article is also increased,
It is necessary to leave (curing) the molded body for a long time (curing) until it can be handled (deboarding and demolding). For this reason, in most of the manufacturing methods, a take-off plate or a floor plate on which a molded body (green plate) immediately after molding is placed is required. However, it is necessary to place the raw plate on these until the curing is completed. Therefore, when the setting time of the molded body is long, the number of the take-up plates or floor plates is required, or a large space for curing is required, or when the take-up plates are collected and used in a line. However, there is a problem that not only requires a long line, resulting in low production efficiency, but also large capital investment costs. Further, when the molded product has a hollow cross section or a deformed product,
Since stacking cannot be performed during curing, a curing place and a curing line are required, and there is a disadvantage that the manufacturing equipment becomes large. Accordingly, an object of the present invention is to make it possible to carry out stripping and demolding in a short time by preserving the pot life of a raw material mixture for a required time and by accelerating the start of setting of a molded article, thereby improving production efficiency. It is an object of the present invention to provide a method for producing a gypsum-based cured product that can obtain an inexpensive and high-quality product by improving the cost and reducing the capital investment. That is, a first invention of the present invention is to provide a method for producing a gypsum-based cured product from a raw material mixture containing hemihydrate gypsum as a main raw material. The mixture is subjected to high shearing treatment immediately before molding, molded and cured, and then dried to obtain a gypsum-based cured product as a product. [0010] The production of the gypsum-based cured product in the present invention can be carried out by a conventionally known molding method, for example, a papermaking method, a press method, an extrusion molding method and the like. Raw materials can be used. For example, gypsum as a main raw material includes hemihydrate gypsum which is a hydratable gypsum. Auxiliary materials for supplementing the performance of molded articles as auxiliary raw materials, as fillers, for example, calcium carbonate powder, silica stone powder, mica, wollastonite, pearlite, shirasu balloon, clay minerals such as talc and the like are commonly used. No. In addition, as fiber for reinforcement,
Conventional materials such as cellulose pulp, organic synthetic fiber, glass fiber, carbon fiber and the like can be mentioned. Further, as a molding aid, a thickener such as methylcellulose, a water reducing agent, an antifoaming agent, a flocculant and the like can be selected and used according to a molding method. In addition, the addition ratio of these raw materials may be a conventional ratio of each molding method,
There is no particular limitation. Further, the water ratio of the raw material mixture may be set at a water ratio according to each molding method. In the present invention, a raw material mixture is prepared by adding the above-mentioned conventional setting retarder to these raw materials in an amount corresponding to the pot life of the raw material mixture required in each production method. If the raw material mixture containing the setting retarder is molded as it is, the setting time of the molded body is prolonged, and it takes a long time to remove the plate and remove the mold. Therefore, a reduction in production efficiency and a large capital investment are required. Therefore, the raw material mixture is molded immediately after molding after the effect of the setting retarder is attenuated and then molded to shorten the setting time, improve production efficiency, and enable production with simple equipment. It is. That is, when a setting retarder is used in combination with gypsum hemihydrate, the setting start time of the molded article is increased. In this case, the setting speed due to the setting is suppressed, and a longer time is required until the setting is completed. Therefore, long-term curing is required before the molded body can be handled. However, a compact having a short setting start time tends to have a high curing speed and a short time until it can be handled. In the present invention, in order to utilize this property of the gypsum-based cured product, the effect of the setting retarder is artificially attenuated immediately before molding the raw material mixture containing the setting retarder, and the time during which the cured product can be handled (e.g. (Type) is shortened. The first invention of the present invention focuses on the fact that it is thought that the action of a setting retarder is to coat the particle surfaces of the granules and suppress hydration, and this action is destroyed by mechanical force. This is achieved by disturbing the coating and at the same time destroying the powder particles or a part thereof to produce a new powder particle surface, suppressing the effect of the curing retarder and promoting the start of setting. It is. Since the raw material mixture used in the first invention of the present invention is subjected to high shearing force, any of the above-mentioned known raw materials which is broken under high shearing force and loses its effect, for example, glass fiber And pearlite are not preferred. Therefore, it is necessary to refrain from using these raw materials or to set the addition amount in consideration of destruction. As a device for applying a high shearing force, a known pulverizer, mixer or pump may be selected in consideration of the properties of the raw material, processing efficiency and processing capacity. Preferably, a rotary compression type pulverizer, a disk friction type pulverizer or an Erich-type mixer is used. In the first invention of the present invention, for example, when a Nara-type pulverizer is used, the raw material mixture is passed once (processed), so that the setting time can be significantly reduced. Since the time required for this treatment is only a few seconds, the effect is tremendous as compared with the case where mixing is continued with a normal stirrer having a low shearing force (such as a propeller type or an omni mixer). The method for forming the raw material mixture subjected to the high shearing force treatment is not particularly limited, and any known means such as a papermaking method, a press method, and an extrusion method can be used. Further, since the molded article obtained by the first invention of the present invention immediately starts to set, it does not require a long curing time as in the conventional method, and then undergoes a drying step to obtain a product. can do. Embodiment 1 In this embodiment, a first invention of the present invention will be described. β
-An omni-mixer is prepared by adding 60% by weight of gypsum hemihydrate and 40% by weight of calcium carbonate powder to 1% by weight of acrylic synthetic fiber and 0.1% by weight of amino acid-based setting retarder. Perform dry mixing for 1 minute at
Water (tap water) was added at 50% by weight and wet-mixed for another 2 minutes to obtain a raw material mixture (slurry). Next, the obtained raw material mixture was fractionated into three sections, and one section was placed in a mold as it was and subjected to dehydration press molding (molding pressure: 50 kg / cm ² ) to obtain a molded product of 8 cm × 15 cm × 1 cm. The obtained molded article is cured by leaving it indoors for one day, then demolded and dried at 40 ° C. for 3 days.
(Comparative product). For the other two sections, pass them through the Nara mill one or three times before molding (3
After performing a high shearing force treatment, the mixture was placed in a mold and subjected to dehydration press molding (molding pressure 50 kg / cm ² ) to 8 cm ×
A molded product of 15 cm × 1 cm was obtained. The obtained molded product is
After standing for a period of time, the product was deplated and dried at 40 ° C. for 3 days to obtain a product (the product of the present invention). The properties of the obtained comparative product and the product of the present invention are shown in the following table. Table 1 Setting start time (min) of molded product Bulk specific gravity Flexural strength (kg / cm ² ) Comparative product 63 1.78 175 Invention product 32 1.75 170 Invention product 28 1.73 166 According to this embodiment, the raw material mixture containing the setting retarder is subjected to a high shearing treatment immediately before molding, and then the molded product obtained by molding has a significantly reduced setting start time. It was confirmed that it was possible to produce a gypsum-based cured product without requiring long-term curing for 24 hours. [0027] [0028] [0029] [0030] [0031] [0032] According to the first shot light of the method of the present invention, the molding while maintaining the pot life of the raw material mixture By shortening the setting time of the body, it is possible to improve the productivity and simplify the manufacturing equipment, and it is possible to manufacture an inexpensive and high-quality gypsum-based hardened body.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-53-82832 (JP, A) JP-A-54-36325 (JP, A) JP-A-53-128620 (JP, A) JP-A-57-128 3749 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) E04C 2/04 Practical file (PATOLIS) Patent file (PATOLIS)

Claims (1)

(57) [Claim 1] In a method for producing a gypsum-based cured product from a raw material mixture mainly containing hemihydrate gypsum, a raw material mixture containing a setting retarder is subjected to high shearing force immediately before molding. A method for producing a gypsum-based cured product, which comprises molding, curing, and then drying after treatment to obtain a gypsum-based cured product as a product.