JPH0114191B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Field of Application> The present invention is directed to cement powders containing ligninsulfonate as the main component, especially those with low molecular weight and ligninsulfonate with reduced sugar content as the main component, by means of fractional recovery, etc. This invention relates to a cement dispersant that has good workability and does not have a setting retarding effect. <Prior Art> Generally, when producing concrete, cement mortar, cement paste, etc., a cement dispersant is used to improve the fluidity and workability of a binder such as cement. Examples of such cement dispersants include those containing lignin sulfonate as the main component, those containing β-naphthalenesulfonic acid formalin condensate as the main component, and those containing formalin high condensate of melamine having sulfonic acid residues as the main component. There are things to do. A cement dispersant containing lignin sulfonate as a main component is hereinafter referred to as a lignin-based dispersant. Conventionally, lignin-based dispersants have been made by reducing the reducing sugar content by fermenting sulfite pulp wastewater with yeast or alcohol, or by adding slaked lime to the wastewater to convert ligninsulfonic acid into an insoluble basic salt.
It is manufactured by methods such as separating and recovering the sugars in the waste liquid, or heating the waste liquid in the presence of slaked lime to render the sugars harmless to the hardening of concrete. <Problems to be Solved by the Invention> However, such lignin-based dispersants have poor short-term strength, so they can be improved by using them in combination with calcium chloride, sodium sulfate, amines, etc. As a result, there are drawbacks such as corrosion of reinforcing bars and precipitation of crystals in winter. In addition, conventional lignin-based dispersants have air-entraining properties,
Since it has curing retardation and false setting properties, it is not possible to reduce the amount of water used by using it in large quantities. The present invention aims to solve the drawbacks of these lignin-based dispersants, and includes, for example,
Cement that contains a cement dispersant with a specific molecular weight and a specific sugar content that has been separated and collected as the main component, has excellent dispersibility, is easy to work with, and has no hardening retardation. It is intended to provide a dispersant. <Means for Solving the Problems> The present invention contains a lignin sulfonate as a main component, and the lignin sulfonate has a molecular weight of 2000 or less and a molecular weight of 25% by weight or less.
10,000 or more is a cement dispersant characterized by having a sugar content of 40% by weight or more and a sugar content of 1.5% by weight or less. The present invention will be explained in more detail below. The cement dispersant of the present invention can be recovered by adding slaked lime to the above-mentioned ligninsulfonic acid-containing liquid and replacing the ligninsulfonic acid with an insoluble basic salt, or by adding a polycation and recovering it as an insoluble composite. Alternatively, saccharides and low-molecular-weight substances can be recovered by separating them into oil using a solvent, or by ultrafiltration. In particular, when recovering by ultrafiltration, it is an advantageous method because not only the polymer lignin can be recovered individually without using additives, but also the sugar can be recovered at the same time. The present invention uses a lignin sulfonate recovered by the above-mentioned appropriate method as a main component, but for cement dispersion, lignin sulfonate with a molecular weight of 2000 or less is 25% by weight or less,
The content is 40% by weight or more with a molecular weight of 10,000 or more, and the sugar content is 1.5% by weight or less. The reason for this limitation in the present invention is that the molecular weight distribution of lignin sulfonate that has been subjected to various polymerization treatments is measured using gel permeation chromatography (GPC) using a hydrophilically treated silica gel, and the sample is When separated, it was found that low molecular weight substances with a molecular weight of 2000 or less caused air entrainment, low dispersibility, and curing retardation;
This is based on the test result that anything less than 10,000 causes low dispersion. Furthermore, if the sugar content is greater than 1.5% by weight, curing will be delayed, resulting in insufficient short-term strength development. The cement dispersant of the present invention can also be used in combination with water reducing agents, retarders, hardening accelerators, AE agents, swelling agents, etc. that have been commonly used in cement-based binders. <Examples> The present invention will be explained below with reference to Examples, but the present invention is not limited thereto. Note that all parts and percentages in each example are expressed on a weight basis. Example 1 Using a mortar mixer, at a temperature of 20°C, the cement dispersant shown in Table 1 was dissolved in 270 parts of water, and then 600 parts of ordinary Portland cement was dissolved.
1,200 parts of river sand were added in this order to obtain a kneaded mortar. The table flow of the mortar was measured, and thereafter the table flow was measured every 20 minutes while stirring with a mortar mixer. Note that mortar was separately kneaded under the same mixing conditions to prepare specimens (4 x 4 x 16 (cm)) with different air content and compressive strength at the time of kneading. These conditions and results are shown in Table 2.

【table】

[Table] From the Examples and Comparative Examples, the cement dispersant of the present invention has higher dispersion performance than conventional cement dispersants, has less air entrainment, and shows no retardation in compressive strength. Example 2 The same procedure as Example 1 was carried out except that the amount added to the cement was changed. The conditions and results are shown in Table 3.

[Table] Even when 0.5% of the product of the present invention is added to cement, it does not have any negative effects such as false setting, has high dispersion performance, and has small changes in flow over time. Further, it does not show any retardation in compressive strength. Example 3 Using the cement dispersants shown in Table 1 and the by-product filtrate repeatedly ultrafiltered with cement dispersant symbols D to F, they were mixed to form cement dispersants G to O with the compositions shown in Table 4. I got it. The same procedure as in Example 2 was carried out except that the cement dispersant shown in Table 4 was used. The results are shown in Table 5. The cement dispersants used are as follows. Mixture of GB and F Mixture of HF and ultrafiltrate I. and JE and K L Mixture of MB and F Mixture of NB and F Mixture of OD, E and ultrafiltrate

【table】

【table】

[Table] <Effects of the Invention> As is clear from the above description, the cement dispersant of the present invention has high dispersion performance, small changes in flow over time, and good air entrainment and retardation of compressive strength. It is a well-balanced cement dispersant with little to no effect. In addition, in the case of comparative examples outside the scope of the present invention, due to their functions, the balance as a cement dispersant is disrupted, such as poor dispersibility, change in flow over time, large air entrainment, and a decrease in initial compressive strength and compressive strength. .

Claims (1)

[Claims] 1 Contains lignin sulfonate as a main component, and the lignin sulfonate contains 25% by weight or less of molecules with a molecular weight of 2,000 or less, and a molecular weight of 10,000 or less.
Contains 40% or more by weight of the following, and has a sugar content of
A cement dispersant characterized by a content of 1.5% by weight or less.