Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From aldehyde or derivative thereof as reactant
Reexamination Certificate
1999-10-19
2001-04-10
Szekely, Peter A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From aldehyde or derivative thereof as reactant
C524S817000, C524S818000, C524S819000, C524S843000, C528S290000, C528S487000, C528S488000, C528S490000, C528S494000, C528S503000
Reexamination Certificate
active
06214965
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for preparing an aqueous solution of sulfonated melamine-formaldehyde resin, and a cement composition in which the solution and a setting retarder are added to a concrete, a mortar, a cement paste or the like.
2. Description of the Related Art
An aqueous solution of sulfonated melamine-formaldehyde resin has conventionally been used as a dispersant for cement for the purpose of increasing fluidity of a cement composition such as a concrete or a mortar, or decreasing a unit amount of water thereby increasing strength and durability.
Some proposals relating to the improvement in a process for preparing such a water reducing agent have been disclosed.
JP-A-55-7590 discloses a melamine-urea formaldehyde condensate modified with an aromatic aminosulfonic acid. Further, its molar ratio is defined such that the aromatic aminosulfonic acid to the total of melamine and urea is (0.2-1.0):1.0, and the molar ratio of melamine to urea is defined 0.75:0.25 to 0.30:0.70.
JP-B-1-40850 discloses a process for preparing an aqueous solution of melamine/aldehyde resin, which comprises: step (a) of reacting 1 mole of melamine, 3.5-6 moles of formaldehyde and 0.5-1 moles of a compound 1 (wherein the compound 1 is at least one member selected from the group consisting of a sulfite of an alkali metal, a sulfite of an alkaline earth metal, a sulfate of an alkali metal, a sulfate of an alkaline earth metal, aminosulfonic acid, amino acid, aminodicarboxylic acid, hydroxycarboxylic acid, hydroxycarboxylic acid lactone, sulfanilic acid and sulfamic acid) in an alkaline medium having a pH of 9.0-13.0 in which water is present, at a temperature of 75-90° C.; step (b) of reacting the mixture obtained in the step (a) with 0.1-3 moles, per mole of melamine used in the step (a), of a compound 2 (wherein the compound 2 is at least one member selected from the group consisting of amino acid, aminocarboxylic acid, aminodicarboxylic acid, carboxylic acid, hydroxycarboxylic acid, hydroxycarboxylic acid lactone, sulfamic acid, sulfanilic acid, aminosulfonic acid, polyhydroxycarboxylic acid and polyhydroxycarboxylic acid lactone at a pH of 5.5-6.5 and a temperature of 75-90° C.; step (c) of adding a basic compound 3 (wherein the basic compound 3 is at least one member selected from the group consisting of an amine, a polyamine, an oxide of an alkali metal, a hydroxide of an alkaline metal, ammonium hydroxide, an oxide of an alkaline earth metal, monoethanol amine, diethanol amine, triethanol amine, a basic salt of a transition metal and a basic salt of zinc or aluminum) to the resin solution obtained in the step (b) to adjust a pH of the solution to 8.0-13.0, and then cooling the solution obtained in the step (c).
DE 441197 discloses a process for preparing an aqueous solution of sulfonated melamine-formaldehyde resin by adjusting the ratio of melamine, sulfanilic acid and formaldehyde to 1:1.1-1.5:3.3-3.6, adjusting a pH of a mixed solution to 5.0-7.0, heating the solution at 50-90° C., and adjusting a viscosity to 10-60 cSt (80° C.).
Conventional water reducing agents comprising a sulfonated melamine-formaldehyde resin as a main component have had the defect in that time for retaining fluidity of a cement composition is short, that is, the fluidity lowers with the passage of time. For this reason, the water reducing agent is mainly used in a concrete secondary product factory, it is used as a fluidizing agent in a ready-mixed concrete, and it is not well used in a ready-mixed concrete production plant. In particular, this tendency is strong in Japan.
In JP-A-55-7590, JP-B-1-40850 and DE 441197, it is difficult to prevent decrease of the fluidity, and it is therefore difficult to use in the ready mixed concrete production plant.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above conventional problems.
One object of the present invention is to provide a process for preparing an aqueous solution of a water reducing agent using a sulfanilic acid modified melamine-formaldehyde resin which has high performance as a water reducing agent and prevents fluidity of a concrete from lowering with the passage of time, without time-extending for complete setting and entraining air.
Another object of the present invention is to provide a cement composition in which an aqueous solution of sulfonated melamine-formaldehyde resin (for example, a sulfanilic acid modified melamine-formaldehyde resin, or a melamine-formaldehyde resin modified with other sulfonating agents) and a setting retarder are added to a concrete, a mortar, a cement paste or the like.
A first aspect of the present invention is a process for preparing an aqueous solution of melamine-formaldehyde resin modified with sulfanilic acid, which comprises the following step (A), step (B) and step (C):
Step (A): a step of adjusting an aqueous solution containing melamine (a), formaldehyde (b), sulfanilic acid (c) and an alkali substance (d) to (a):(b):(c)=1:2.5-3.5:0.5-1.5 in molar ratio and its pH to 8.0-13.5, and thereafter heating the aqueous solution at 50-90° C. to conduct the reaction until free sulfanilic acid decreases to 40-90 mol % of the amount of sulfanilic acid charged;
Step (B): a step of adding an inorganic acid to the reaction liquid obtained in the step (A) to adjust its pH to 6.0-8.0, and thereafter heating the reaction liquid at 50-90° C. to conduct the reaction until free sulfanilic acid decreases to 20-60 mol % of the amount of sulfanilic acid charged;
Step (C): a step of adjusting a pH of the reaction liquid obtained in step (B) to 7.0-13.5.
A second aspect of the present invention is a cement composition comprising the aqueous solution of melamine-formaldehyde resin modified with sulfanilic acid, prepared by the process in the first aspect.
A third aspect of the present invention is a cement composition comprising the following component (I) and component (II):
Component (I): an aqueous solution of sulfonated melamine-formaldehyde resin obtained by a series of steps comprising of reacting (i) melamine, (ii) formaldehyde and (iii) a compound selected from the group consisting of a sulfate, a sulfite, a bisulfate, a bisulfite, a pyrosulfate, a pyrosulfite, sulfamic acid and sulfanilic acid in alkaline medium, conducting a condensation reaction by adding an acid, and then adding an alkali; and
Component (II): a setting retarder.
A fourth aspect of the present invention is the cement composition as described in the third aspect, wherein sulfanilic acid is used as the compound (iii) in the production of component (I).
A fifth aspect of the present invention is the cement composition as described in the third aspect, wherein the compound (I) is an aqueous solution of melamine-formaldehyde resin modified with sulfanilic acid that is produced in the process as described in the first aspect.
A sixth aspect of the present invention is the cement composition as described any one of the third to fifth aspects, wherein the setting retarder of component (II) is aliphatic carboxylic acid, oxycarboxylic acid, oxycarboxylate, dicarboxylic acid, dicarboxylate, ketocarboxylic acid, ketocarboxylate, ligninsulfonate, sugar, hexafluorosilicate, cellulose ether, alkylaminophosphoric acid compound or their mixtures.
A seventh aspect of the present invention is the cement composition as described any one of the third to fifth aspects, wherein the setting retarder of component (II) is oxycarboxylate, lignin sulfonate, hexafluorosilicate or their mixtures.
PRACTICAL EMBODIMENT OF THE INVENTION
The melamine, formaldehyde and sulfanilic acid used in the step (A) in the first aspect of the present invention can be general industrial products, and can be commercially available. Examples of the industrial products of formaldehyde include formalin and paraformaldehyde. Examples of the preferable alkali that is added for pH adjustment include sodium hydroxide and potassium hydroxide.
In step (A), an amino group-containing compound other than melamine, s
Nakayama Keisuke
Sudoh Yuhji
Sugiyama Takaichi
Uchida Jun
Nissan Chemical Industries Ltd.
Oliff & Berridg,e PLC
Szekely Peter A.
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