RU2075463C1 - Process for preparing film-forming additive for concrete - Google Patents

Abstract

FIELD: preparation of water dispersible film-forming additives to upkeep fresh concrete of highways and aerodromes; hydraulic engineering; monolith house building; geliothermal, induction, infrared and electric heating of freshly mold at precast concrete and reinforced concrete structures. SUBSTANCE: predetermined amounts of aqueous suspension of paraffin containing and auxiliary components in water containing higher fatty acids are heated to 70-90 C. The whole is homogenized and mixed with aqueous solution of alkaline components heated to the same temperature. Dispersion with concentration of 30-60% is prepared, then mixed with aqueous solution of C₁₀-C₂₁-fatty acid soaps, the ratio of component being as follows, wt.-%: 30-60-% aqueous paraffin-containing dispersion, 60-85; 30-20-% aqueous solution of C₁₀-C₂₁ fatty acid soaps, 15-40. EFFECT: more efficient preparation process. 8 tbl

Description

 The invention relates to construction production and can be used for the preparation of water-dispersed film-forming additives for concrete care of freshly laid cement-concrete coatings of roads and airfields, lining of irrigation canals, industrial sites in hydraulic engineering and monolithic housing construction, during the construction of embankments and bridges, with energy-saving methods of heat treatment / instead of steaming / prefabricated concrete and reinforced concrete products and structures, including solar thermal processing, hot-air warming by natural gas combustion products or hot air or utilized flue gases, or thermal waters, or dead steam, as well as infrared, electric induction and electric heating, heat-free curing in heat-insulating forms, for hydrophobization, to reduce water absorption, increase water resistance, frost resistance and corrosion resistance of products and structures made of concrete, foam and expanded clay concrete, gypsum and other building materials.

A known method of preparing a film-forming additive for concrete by heating the calculated amounts of paraffin wax, mineral oils and water with high fatty acids to a temperature of 83 88 ^o C, their homogenization and mixing with cyanuric acid ethyl ester as an emulsifier [1]
There is another method for preparing a film-forming additive for concrete, in which the calculated amount of an aqueous dispersion of paraffin-containing and auxiliary components in water with higher fatty acids is heated to a temperature of 70 90 ^o C, homogenized and mixed with an aqueous solution of alkaline components heated to the same temperature [2 ]
A disadvantage of the known methods is the high viscosity of the prepared additive, which makes it difficult or impossible to transport and use it, especially at low positive ambient temperatures in the autumn-spring period of the construction of roads, airfields, etc. Due to the thixotropic properties and the tendency to hardening of alkaline soaps of higher fatty acids, which are an emulsifier of a film-forming additive, the latter, after 3 to 5 days after preparation, turns into a viscous liquid, and at low temperatures into a non-flowing paste. The decrease in the concentration of additives is less than 23 wt. allowing to reduce its viscosity, is unacceptable, as a result of a sharp decrease in the water-holding ability of the additive.

 The introduction of the plasticizer in the additive due to the thixotropy of its properties gives only a temporary effect of reducing viscosity and also reduces the aggregative stability of the additive, i.e., leads to its separation. An additional dilution of the additive with water leads to the same effect. At the same time, the water-holding ability of the additive is significantly reduced when caring for concrete.

The spray equipment / machines of the DS-105 / type existing in road-building organizations is not capable of working with film-forming additives of such viscosity. Therefore, it is necessary either to heat the additive to a temperature of 33-40 ^o C, which is a difficult task in the field, or to dilute the additive with water, deliberately reducing its protective ability and increasing its consumption when caring for concrete. An increase in the consumption of additives leads to an extension of the time required to form a moisture-protective film on concrete up to several days and to a disruption in the work schedule when cutting, for example, expansion joints of the runway web, roads, etc.

 The technical result of this method is the elimination of thixotropy and a decrease in the viscosity of the film-forming additive while maintaining its water-holding ability.

To achieve a technical result in a method of preparing a film-forming additive for concrete, in which the calculated amounts of an aqueous dispersion of paraffin-containing and auxiliary components are heated in water with higher fatty acids at a temperature of 70 90 ^o C, they are homogenized and mixed with an aqueous solution of alkaline components heated to the same temperature , the dispersion is prepared in a concentration of 30-60% and then mixed with an aqueous solution of soaps of fatty acids of fractions C ₁₀ -C ₂₁ at a ratio of their wt.

30 60% aqueous paraffin dispersion 60 85
3 20% aqueous solution of soaps of fatty acids of fractions C ₁₀ -C ₂₁ 15 40.

 The temperature of preparation of the additive is set taking into account the melting temperature of paraffin-containing components in higher fatty acids.

Low melting components of slop-vox, soft and liquid paraffins, depending on the type of emulsifier, are dispersed in water at the following temperatures:
at 60 70 ^o C in soaps of bottoms of synthetic fatty acids / FFA / / t _pl. = 45 50 ^o C / or in soaps of fatty wool acids;
at 75 80 ^o C in small stearic acid / t _PL = 69 ^o C /.

High-melting components of petrolate and ceresin are dispersed at a temperature of 80 90 ^o C, depending on their melting temperature.

For the preparation of a film-forming water-dispersed additive, the following products are used as components:
paraffin-containing: liquid petroleum paraffins C ₁₀ -C ₂₄ with t _pl. ≅15 ^o C, soft C ₂₁ -C ₂₄ with t _pl. 14 - 32 ^o C, solid C ₁₈ -C ₃₅ with t _pl. 42 64 ^o C, ceresin C ₃₆ -C ₅₅ with t _pl. 57 80 ^o C, petrolatum with t _pl. 53 65 ^o C, ozokerite t _mp 65 95 ^o C, slop vox, distillate and filtrate deoiling a slack wax / paraffin mixture with mineral oil and petrolatum additive / s pour point of 25 42 ^o C:
auxiliary: drying oils, alkyd resins, higher fatty alcohols;
higher fatty acids; fractions C ₂₁ -C ₃₁ .

Synthetic fatty acids: fractions C ₂₁ -C ₂₅ , bottoms FFA / C ₂₅ -C ₃₁ /, wool fatty acids, stearic acid / C ₁₈ /;
alkaline components: potassium oxide or sodium hydrate, potash / K ₂ CO ₃ /, soda ash / Na ₂ CO ₃ /, aqueous ammonia, Triethanolamine, diethylethanolamine, morpholine;
alkaline soaps of low and medium molecular weight synthetic fatty acids, fractions C ₁₀ -C ₂₁ , including fractions C ₁₀ -C ₁₃ , or C ₁₂ -C ₁₆ , or C ₁₄ -C ₁₆ , or C ₁₀ -C ₁₆ , or C ₁₀ -C ₂₁ , or alkaline soaps of bottoms of fatty acids of the fraction (C ₁₀ -C ₂₀ ) of stocks of vegetable oils. Soaps are prepared by saponification of C ₁₀ -C ₂₁ fatty acids with an aqueous solution of an alkaline component or mixtures thereof.

 Specific examples of the method, the rheological and water-holding properties of the film-forming additives are given in examples 1 to 3, and the formulations of the initial paraffin-containing dispersions and alkaline soaps are given in table. 1 and 2, respectively.

The nominal viscosity (η, c) of additives is determined by GOST 8420 74 on a B3-4 viscometer at temperatures of 20 ^o C and 5 ^o C, and the water-holding ability of additives according to the American standard ASTM C-156-91 by determining the specific moisture loss ΔW, g / cm ² / concrete through a film coating after 72 hours of heating in a climate chamber at a temperature at 40 ^o C, relative humidity 30% and its speed V _b 5 7 m / s. Samples - tiles with an open surface modulus M _n 20 m ^{-1 were} formed from a cement-sand mixture / 1: 3 / s W / D 0.4 and immediately after finishing their upper surface they were covered with a film-forming additive using a KRP-6 pneumatic spray gun. Additive consumption was 250 g / m ² of concrete surface. According to ASTS C156-91, the permissible moisture loss of concrete protected by a film-forming additive should not exceed the ΔW≅ value of 0.055 g / cm ² .
Example 1

 By a known method of preparation, film-forming additives, the composition of which is presented in table. one.

Additive N 1 is prepared by heating in a paddle mixer to a temperature of 75
80 ^o C a mixture of paraffin-containing components and higher fatty acids, consisting of the calculated amount of petrolatum, slop wax and fatty acids of wool fat. After melting, the mixture is homogenized with melt stirring for 5 minutes. A hot / 75 80 ^° C / soda ash solution, previously prepared by dissolving the soda in 50% of the calculated amount of water, is poured into the obtained melt and the mixture is stirred for 5 minutes. The remaining amount of water is added to it with stirring and the dispersion is treated for 10 minutes in a paddle mixer at n ≅ 100 rpm. After cooling the dispersion to a temperature of 20-30 ^o C it is mixed with the estimated amount of plasticizer and divinyl styrene latex. An increase in the mixing time of the dispersion to 1–2 h at various stages of its preparation, as well as the introduction of an aqueous soda solution in the melt, previously prepared by dissolving soda in 100% of the calculated amount of water, does not significantly affect the viscosity and thixotropic properties of the paraffin-containing additive.

Additive N 2 / table 1/ is prepared by heating to 70–85 ^° C a mixture of petrolatum, slop-wax, still bottoms FFA and FFA fractions C ₁₀ -C ₁₆ in a mixer until the mixture is completely melted. The melt is homogenized with stirring for 30 minutes. A hot / 75 80 ^o C / solution of triethanolamine, preliminarily prepared by dissolving triethanolamine in 50% of the calculated amount of water, is poured into the obtained melt and the mixture is stirred for 1 2 hours to saponify the bottom residue of FFA fraction C ₁₀ -C ₁₆ . The remaining amount of water with potassium hydroxide or sodium hydroxide dissolved in it is added to the mixture and the mixture is stirred for 30 minutes until the fatty acids are completely saponified.

 The finished paraffin-containing additive is poured into a storage tank. Changing the order of introduction into the mixture of alkaline components (first caustic alkalis, and then triethanolamine) or their combined introduction into the mixture does not significantly affect the viscosity and ticostropic properties of the finished paraffin-containing additive. In the same known manner, additives N 3 - 6 are prepared.

Additives N 3 and 6, containing low melting components, distillate gach and soft paraffin, are prepared at a temperature of 60 ^o C, additive N 4 containing high melting ceresin, at a temperature of 90 ^o C, additive N 5, with hard paraffin at a temperature of 70 75 ^o C. Excipient - film former drying oil, in additives N 4 and 5 are introduced with stirring into the melt before saponification of higher fatty acids. The properties of the synthesized additives are given in table. 4. All additives prepared in a known manner do not meet the rheological properties presented to the finished film-forming additives for concrete care.

The compositions and characteristics of film-forming additives made by this method are given in table. 3 8. An aqueous solution of alkaline soap of fatty acids of fraction C ₁₀ -C ₂₁ is introduced either during the preparation of paraffin-containing additives after saponification of high molecular weight fatty acids of fraction C ₂₁ -C ₂₅ and their bottoms, or into the finished dispersion. The thinning and anti-xotropic effect of these soaps is achieved in this way only if the soaps are introduced after dispersion of the paraffin-containing components. The introduction of these soaps into the melt of a mixture of paraffin-containing components with fatty acids of the C ₂₁ -C ₂₅ fraction and from bottoms or during the saponification of these acids when dispersing paraffins does not dilute the prepared dispersion. The reason for this phenomenon may be the polymerization of low molecular soap at elevated temperatures for emulsification of paraffins in water.

 Separate administration of the soap / fatty acid components, and then the alkaline water component, or vice versa / into the additive prepared by the known method, also does not remove the thixotropy of the paraffin-containing additive and its gelation during storage.

 In this example, additives are prepared according to this method with a transcendental and minimum soap content / N 1m and 3m /. The formulations of these compositions are given in table. 3, and their properties in table. 4.

As can be seen from the data table. 4, the complex requirements for viscosity / η 25 s at 20 ^o C and +5 ^o C / and water-holding capacity / DW 0,055 g / cm ² / meet the composition N 9, 16 16. A number of compositions containing an exorbitant amount of components do not meet this requirements either in viscosity / N 18 /, or in water-holding capacity / N 10, 17 /, or simultaneously for both of these indicators / N 7, 8, 11 /. An overdose of soap reduces the protective properties of the additive, and an insufficient amount of soap does not provide the necessary dilution of the additive and the removal of the thixotropic effect.

 Example 2

 According to this method, set forth in example 1, paraffin-containing additives with a transcendental and average soap content / N 3m and 4m / are prepared. The formulations of these compositions are given in table. 5, and their properties in table. 6.

According to the table. 5 and 6, additives N 20 22, 24 27 made by this method have the required viscosity η25 and water-holding ability ΔW ≅ 0.055 g / cm ² .
Example 3

 According to this method, set forth in example 1, paraffin-containing additives are prepared with a transcendental and maximum soap content / N 5m and 6m /. The formulation of these compositions are given in table. 7, and their properties in table. eight.

 According to the table. 7 and 8, additives N 32, 34 38 made by this method meet the requirements of viscosity and water retention capacity.

 The paraffin-containing additive for concrete care synthesized by this method, in its physical and technical characteristics, corresponds to or surpasses the similar properties of foreign analogues, and at a cost significantly less.

Claims (1)

A method of preparing a film-forming additive for concrete, in which the calculated amounts of an aqueous dispersion of paraffin-containing and auxiliary components in water with higher fatty acids are heated to a temperature of 70 90 ^° C, they are homogenized and mixed with an aqueous solution of alkaline components heated to the same temperature, characterized in that the dispersion is prepared with a concentration of 30-60% and then mixed with an aqueous solution of soap acids of fatty fraction C _{1 0} -C _{2 1} at their ratio, wt. 30 60% aqueous paraffin dispersion 60 85
3 20% aqueous solution of soaps of fatty acids of the fraction C _{1 0} -C _{2 1} 15 40 _t

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