JPH028988B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for preventing the efflorescence phenomenon of cement mortar, and more specifically, to a method for preventing the efflorescence phenomenon in cement mortar. The present invention therefore relates to a method for preventing efflorescence of cement mortar. [Prior Art] Mortar efflorescence is a phenomenon in which when mortar absorbs moisture from the outside, calcium carbonate dissolves and leaks out to the outside, and white calcium carbonate crystals precipitate again. Efflorescence occurs when tiles or other decorative materials are applied to mortar exterior walls, and the white crystals significantly impair the aesthetic appearance. Exterior walls with efflorescence can be cleaned using dilute hydrochloric acid, etc.
Calcium carbonate is dissolved and removed, but white crystals begin to precipitate again soon afterward, and countermeasures to this problem are extremely difficult, and no satisfactory solution has been found to date. [Problems to be Solved by the Invention] An object of the present invention is to provide a method for effectively preventing the occurrence of efflorescence itself in cement mortar. [Means for Solving the Problems] The method for preventing the efflorescence phenomenon of cement mortar of the present invention is to prevent the efflorescence phenomenon of cement mortar by adding 0.5 parts by weight or more (in terms of solid content) to cement mortar based on 100 parts by weight of cement in the cement mortar. ), and the high molecular weight atactic polypropylene aqueous emulsion composition has an average molecular weight of about 3,000 to about 30,000 and contains substantially atactic polypropylene; It is made by dispersing in water a homogeneous kneaded product consisting of 0.03 to 0.5 parts by weight of partially saponified polyvinyl alcohol per 1 part by weight of polypropylene and about 0.05 to 2 parts by weight of water per 1 part by weight of the partially saponified polyvinyl alcohol. It is characterized by In place of the high molecular weight atactic polypropylene aqueous emulsion composition used in the above-described method, a dispersion of substantially atactic polypropylene having an average molecular weight of about 3,000 to about 30,000, 0.03 to 0.5 part by weight per part by weight of the atactic polypropylene. About 0.05 to 2 parts by weight of water per 1 part by weight of the atactic agent and the dispersant are kneaded while applying a shearing force, and the resulting homogeneous kneaded product is mixed with water and about 0.5 to 2.0 parts by weight per 1 part by weight of the above-mentioned atactic polypropylene. A material mixed with asphalt may also be used. The main focus of the method of the present invention is to make the mortar itself watertight and prevent dissolution of calcium carbonate. Any cement mortar that causes efflorescence when used as is is subject to the present invention. The high molecular weight atactic polypropylene composition used in cement mortar has an average molecular weight of approximately 3000.
~30,000 and substantially attic polypropylene, from 0.03 per part by weight of the polypropylene
It is prepared by dispersing in water a homogeneous kneaded product consisting of 0.5 part by weight of partially saponified polyvinyl alcohol and about 0.05 to 2 parts by weight of water per 1 part by weight of the partially saponified polyvinyl alcohol. As used herein, "substantially atactic polypropylene" refers to a mixture containing atactic polypropylene as a main component and a small amount of low molecular weight polypropylene having a stereospecific structure such as isotactic or syndiotactic. , which is usually obtained during stereospecific catalyzed polymerization of polypropylene by extracting the polymerized product with a solvent such as n-heptane. The amount of partially saponified polyvinyl alcohol added to the atactic polypropylene is 0.03 to 0.5 part by weight, preferably 0.05 to 0.3 part by weight, per 1 part by weight of the atactic polypropylene. The partially saponified polyvinyl alcohol which is considered to act as an emulsifier for atactic polypropylene preferably has a degree of saponification of 70 to 98%, particularly 80 to 97%. The amount of water mixed mainly depends on the amount of partially saponified polyvinyl alcohol used, but it is usually about 1 part by weight of partially saponified polyvinyl alcohol.
It is used in a range of 0.05 to 2 parts by weight, preferably about 0.1 to 2 parts by weight. The best emulsion can be obtained by kneading with approximately the same weight to 1.5 times the amount of water as the partially saponified polyvinyl alcohol. Note that the stability of the emulsion produced is further improved by using a small amount of petroleum resin in combination with atactic polypropylene, partially saponified polyvinyl alcohol, and water. As the petroleum resin, either one whose main raw material is cyclopentadiene or one whose main raw material is a higher olefinic hydrocarbon can be used, but one that is solid at room temperature is preferable. The amount of petroleum resin blended is preferably about 0.05 to about 0.2 parts by weight per 1 part by weight of high molecular weight atactic polypropylene. In addition to the partially saponified polyvinyl alcohol, small amounts of commonly used dispersants, such as anionic activators such as sodium oleate and sodium stearate, and nonionic activators such as polyoxyethylene alkyl phenol ether, may also be used. Asphalt may also be added to the above-described high molecular weight atactic polypropylene aqueous emulsion composition. Asphalt as used here refers to a bitumen whose main component is a hydrocarbon oil component called medium, petrolene, or marten, a protective substance called asphalt resin, and colloidal particulate or ultrafine particulate carbon, and is natural asphalt. It may also be petroleum asphalt. Generally, the melting point will be in the range of about 60°C to about 160°C. The amount of asphalt added to the high molecular weight atactic polymer is per 1 part by weight of the former.
It is 0.5 to 2.0 parts by weight, preferably 0.7 to 1.5 parts by weight. If the ratio of asphalt to high molecular weight atactic polypropylene is too high, the stability of the emulsion will be impaired. In order to produce an emulsion-like composition, first, high molecular weight atactic polypropylene, partially saponified polyvinyl alcohol, water, and, if necessary, a petroleum resin are sufficiently and uniformly kneaded. As the kneading means, any conventionally known method may be used, such as a kneader or a Banbury mixer. There is no particular restriction on the order in which the substances to be kneaded are added, but the above three or four substances may be added to the kneader at the same time, or a paste or putty-like mixture of water-soluble polymer and water may be prepared in advance. This is preferably kneaded with atactic polypropylene. In order to achieve uniform kneading more effectively, kneading is preferably carried out under heating. When asphalt is added, an aqueous emulsion of high molecular weight atactic polypropylene is first prepared and mixed with heat-melted asphalt and water. The homogeneously kneaded material thus obtained is then uniformly mixed with a large amount of water to immediately form a stable emulsion, thereby forming an emulsion-like composition of high molecular weight atactic polypropylene. In order to improve the stability of the composition at low temperatures, it is desirable to lower the temperature and uniformly mix the kneaded material and water at approximately room temperature. The resulting aqueous emulsion is very stable and changes little with temperature changes, long-term standing and dilution with water. Generally, it is desirable that the concentration of the high molecular weight atactic polymer in the aqueous emulsion be about 30 to 60% by weight. The amount of high molecular weight atactic polypropylene aqueous emulsion composition mixed into cement mortar is as follows:
It is sufficient that the emulsion is 0.5 part by weight or more (in terms of solid content), and usually 1 to 3 parts by weight is mixed in consideration of the effect on various properties of the mortar. The emulsion is mixed in when mixing mortar in a batcher at a ready-mixed concrete factory.
There are two methods: mixing the emulsion at the same time, or putting the emulsion into a truck agitator for transporting raw mortar and kneading it at high speed for about 3 minutes, or putting the emulsion into a mortar mixer used at construction sites and kneading it. All of them can be adopted. [Effects of the Invention] According to the method of the present invention, the high molecular weight atactic polypropylene composition is filled into the voids of the mortar, making it watertight, making it difficult for the mortar to absorb moisture, and preventing the efflorescence phenomenon caused by the elution of calcium carbonate. Prevented. Furthermore, the drying shrinkage rate of the mortar is reduced, making it difficult for the mortar to crack. [Example] The present invention will be specifically described below with reference to Examples. Examples 1 and 2, Comparative Example 1 The following compounds Atactic polypropylene (average molecular weight approx.
21000) 1000g petroleum resin 60# (manufactured by Toho Plastics) 95g polyvinyl alcohol (degree of saponification 88%) (Nippon Gosei PVA217) 150g water 150g was kneaded for 20 minutes at an internal temperature of 90℃ in a pressurized kneader. Next, add and mix 300g of water at 60℃,
Add more cold water and mix for 10 minutes to reduce the solids content.
A 50% by weight emulsion-like composition was obtained. The above emulsion-like composition was blended into cement mortar in the ratio (B) shown in Table 1 below, and the water absorption ratio and water permeability ratio of the cured product were tested (Example 1). The results are shown in Table 1. For comparison, ordinary mortar (A) without the emulsion-like composition was similarly tested (Comparative Example 1). The results are shown in Table 1. In addition, the above emulsion composition (at 60°C)
Asphalt at 150° C. was gradually added (blending ratio: 1.4 parts by weight of asphalt per 1 part by weight of atactic polypropylene in the emulsion), and after the addition was completed, stirring was carried out for about 10 minutes to obtain an asphalt-containing aqueous emulsion composition. A similar test (C) in which this composition was blended with cement mortar was conducted (Example 2). The results are shown in Table 1.

[Table] Measure the depth of penetration.
Mortar of the above blend B was applied to the concrete exterior wall, and tiles were pasted on top. Three years have passed, but no efflorescence has been observed.

Claims (1)

[Claims] 1. A cement mortar is blended with 0.5 parts by weight or more (in terms of solid content) of a high molecular weight atactic polypropylene aqueous emulsion composition based on 100 parts by weight of cement in the cement mortar. and the high molecular weight atactic polypropylene aqueous emulsion composition comprises substantially atactic polypropylene having an average molecular weight of about 3,000 to about 30,000, 0.03 to 0.5 parts by weight of partially saponified polyvinyl alcohol per 1 part by weight of the polypropylene, and A method for preventing efflorescence in cement mortar, comprising dispersing in water a homogeneous kneaded material consisting of about 0.05 to 2 parts by weight of water per 1 part by weight of the partially saponified polyvinyl alcohol. 2. A high molecular weight atactic polypropylene aqueous emulsion composition of 0.5 parts by weight or more (in terms of solid content) is blended into the cement mortar based on 100 parts by weight of cement in the cement mortar, and The molecular weight atactic polypropylene aqueous emulsion composition comprises a substantially atactic polypropylene having an average molecular weight of from about 3,000 to about 30,000, from 0.03 to 0.5 parts by weight of a dispersant per part by weight of the atactic polypropylene, and per part by weight of the dispersant. Approximately 0.05 to 2 parts by weight of water is kneaded while applying a shearing force, and the resulting homogeneous kneaded product is mixed with water and the above-mentioned atactic polypropylene 1.
A method for preventing efflorescence in cement mortar, characterized in that it is mixed with asphalt in an amount of 0.5 to 2.0 parts by weight.