JPH0222020B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a new admixture for hydraulic cement, and more specifically, a novel polycarboxylic acid-based admixture for hydraulic cement that has excellent performance as a dispersant, water reducer, fluidizing agent, etc. Regarding admixtures. (Prior Art) Generally, when producing concrete, mortar, paste, etc. using cement, admixtures called dispersants, water reducers, or fluidizers are used. This admixture is expected to have the following effects. That is, (1) increasing the workability of unset cement mixtures; Also, if the workability is the same, the amount of water used will be reduced. (2) Since the amount of water used can be reduced, the strength after construction is increased as a result. Also, if the strength is the same, the amount of cement used can be reduced. (3) Increase watertightness. etc. Conventionally, such admixtures include lignin sulfonic acid, oxycarboxylic acid, β-naphthalene sulfonic acid, formalin condensate, melamine sulfonic acid/formalin condensate, and olefin-based admixtures.
α,β-unsaturated dicarboxylic acid copolymer system (hereinafter referred to as
Polycarboxylic acid admixtures (sometimes simply referred to as polycarboxylic acid-based admixtures) are known, and among them, polycarboxylic acid-based admixtures are known to exhibit good dispersion fluidity with a small amount added and also have excellent slump retention. Recently,
Research is being actively carried out (for example, the
-18215, 53-38095, JP-A-58-213663, etc.). (Problems to be Solved by the Invention) However, even such polycarboxylic acid admixtures cannot be said to satisfy the performance requirements for dispersion fluidity and slump retention, which have become increasingly sophisticated in recent years. Improvements were strongly desired. Therefore, the present inventors have conducted intensive studies to overcome these drawbacks, and have found that using a polycarboxylic acid with a specific composition with a small amount of high molecular weight moieties, compared to conventionally known polycarboxylic acid admixtures, The present inventors have discovered that a cement composition with good dispersion fluidity, excellent workability with significantly suppressed slump reduction, and a cured product with high strength can be obtained, and the present invention has been completed. (Means for Solving the Problems) Thus, according to the present invention, the number average molecular weight is 300
Contains as an active ingredient a copolymer or salt of 60 to 85 mol% of α, β-unsaturated dicarboxylic acid and 40 to 15 mol% of olefin, with a molecular weight of ~10,000 and a molecular weight of 20,000 or more controlled to 10% by weight or less. An admixture for hydraulic cement is provided. The copolymer used in the present invention comprises (a) 60 to 85 mol% of α,β-unsaturated dicarboxylic acid, preferably 5 to 80% by mole;
mol% and (b) olefin 40-15 mol%, preferably
Consists of 35 to 20 mol% and has a number average molecular weight of 300 to
10,000, preferably 1,000 to 8,000, and the high molecular weight portion having a molecular weight of 20,000 or more is controlled to 10% by weight or less, preferably 8% by weight or less of the total weight. Here, the number average molecular weight refers to high performance liquid chromatography (tetrahydrofuran solvent, measurement temperature 40°C).
It means the polystyrene equivalent measured by. Such a copolymer has a larger amount of α,β-unsaturated dicarboxylic acid units constituting the copolymer and a smaller content of high molecular weight moieties than conventionally known polycarboxylic acid cement admixtures. As a result, it has superior performance in terms of dispersion fluidity and slump retention, surpassing conventional technology. Copolymer composition, number average molecular weight or molecular weight
When the proportion of the high molecular weight portion of 20,000 or more is out of the above range, the effect of improving dispersion fluidity is small, the slump decreases over time is large, and the compressive strength of the cured product is poor. Among these, the sharper the molecular weight distribution, the better the performance.
Ratio of weight average molecular weight (Mw) to (Mw/
Mn) is preferably 2.0 or less, more preferably 1.9 or less. Specific examples of the component (a) constituting the copolymer include maleic acid, itaconic acid, citraconic acid, anhydrides thereof, and maleic anhydride is particularly industrially advantageous. On the other hand, specific examples of the component (b) include ethylene, propylene, isobutylene, butene-1, butene-2, pentene-1, pentene-2, 2-methylbutene-1, 2-methylbutene-2, 4-methyl Chain olefins such as pentene-1 and hexene-1, cyclobutene, cyclopentene,
Examples include cycloolefins such as cyclohexene, cycloheptene, cyclooctene, cyclopentadiene, dicyclopentadiene, 2-ethyl-5-norbornene, 2-cyano-5-norbornene, and 2-acetyl-5-norbornene, among which C Preferred are _4-6 chain olefins and _{C4 - C6} cycloolefins. Furthermore, vinyl monomers such as acrylic acid, vinyl acetate, methacrylic acid, methyl, methyl vinyl ether, acrylonitrile, ethylene sulfonic acid, etc. may be copolymerized within a range that does not essentially impair the effects of the present invention. Furthermore, some of the carboxyl groups and/or acid anhydride groups in the copolymer may be esterified or amidated before use. The method for producing the copolymer used in the present invention is not particularly limited, and any method may be used as long as a copolymer having the above-mentioned properties can be obtained. For example, an excessive amount of α with respect to olefin,
Examples include a method in which β-unsaturated dicarboxylic acid is charged and radical polymerized, and then the high molecular weight portion is removed by ultrafiltration, and a method in which the high molecular weight portion is extracted and separated using a solvent. If the produced copolymer itself is water-soluble, it can be used as is, but usually some or all of the carboxyl groups and/or acid anhydride groups present in the copolymer are monovalent or It is used by converting it into a salt with polyvalent cations to increase its water-solubilizing ability. Specific examples of such salts include salts of alkali metals or alkaline earth metals such as sodium, potassium, magnesium, calcium, barium, etc., ammonium salts, amine salts such as trimethylamine, triethylamine, triethanolamine, etc., and salts of these salts. Examples include complex salts, among which alkali metal salts are preferred from the viewpoint of economy, safety, and dispersibility. Further, its usage form is not particularly limited, and it can be used in the form of an aqueous solution or a powdered solid form, and can be used alone or in combination with other cement admixtures. Cement admixtures that can be used in combination include conventional cement dispersants, air entraining agents,
Examples include cement wetting and dispersing agents, waterproofing agents, strength enhancers, hardening accelerators, setting accelerators, and setting retarders. The amount of the cement admixture of the present invention may be appropriately selected depending on the required performance, but it is usually used in a proportion of 0.01 to 3% by weight, preferably 0.05 to 1% by weight, based on the solid content of cement. Ru. As the amount used decreases, the effect of improving workability decreases, and on the other hand, if it increases excessively, it may adversely affect the hardening of cement. Furthermore, the timing of addition to the cement mixture can be selected as appropriate depending on the intended use. Specific methods include, for example, mixing it in the cement in advance, adding it at the same time when mixing the concrete mixture, adding it after adding water or other admixtures and starting stirring, and mixing the mixture in advance. An example is a method in which the additive is added after a suitable interval. Among these, remarkable effects are shown when used in a method of simultaneous addition during kneading. The types of cement to which the hard cement admixture of the present invention can be applied are not particularly limited, and specific examples thereof include ordinary Portland cement, early strength Portland cement, moderate heat Portland cement, alumina cement, fly ashes cement, and blast furnace cement. , silica cement, slag cement, various mixed cements, etc. (Effects of the Invention) Thus, according to the present invention, it is possible to obtain a cement composition with good dispersion fluidity of cement and good workability in which slump reduction is significantly suppressed, and a highly cured product can be obtained. (Example) The present invention will be described in more detail with reference to Examples below. Note that parts and percentages in Examples and Reference Examples are based on weight unless otherwise specified. Reference Example 1 1 A mixture of 98 parts of maleic anhydride, 110 parts of the _C5 olefin mixture shown in Table 1, 4 parts of benzoyl peroxide, and 400 parts of benzene was heated under a nitrogen atmosphere in an autoclave at 70 to 75°C. The mixture was heated and stirred for an hour to react. After the polymerization reaction was completed, the precipitated copolymer was collected by filtration and dried to obtain a _C5 olefinic acid copolymer (I). Next, the composition, number average molecular weight, weight average molecular weight, and content of a high molecular weight portion having a molecular weight of 20,000 or more of this copolymer were measured. The results are shown in Table 2. Table 1 iso-pentane approx. 16% n-pentane approx. 15% 2-methylbutene-1 approx. 42% pentene-1 approx. 27% Isoprene 0.1% or less Reference example 2 98 parts of maleic anhydride and the _C5 olefin shown in Table 1 Reference Example 1 except that 76 parts of the mixture was used.
A copolymer () was obtained in the same manner as above. Its properties are shown in Table 2. Reference Example 3 The copolymer () obtained in Reference Example 2 was subjected to ultrafiltration using a membrane with a separation limit molecular weight of 20,000 to obtain a copolymer () from which high molecular weight portions were removed. Its properties are shown in Table 2. Reference Example 4 A copolymer was produced in the same manner as in Reference Example 1, except that 98 parts of maleic anhydride and 26 parts of the _C5 olefin mixture shown in Table 1 were used, and then a copolymer was produced in the same manner as in Reference Example 3, except that 98 parts of maleic anhydride and 26 parts of the C5 olefin mixture shown in Table 1 were used. A copolymer () was obtained by filtration. Its properties are shown in Table 2. Reference Example 5 The copolymer () obtained in Reference Example 1 was ultrafiltered in the same manner as in Reference Example 3 to obtain a copolymer ().
I got it. Its properties are shown in Table 2.

【table】

[Mortar test]

Prepare cement mortar with the following composition and JIS-
A mortar test was conducted according to R-5201 (the amount of admixture added was adjusted so that the target flow was 230 mm±5 mm). The amount of air entrainment was measured according to JIS-A-1116. The mortar temperature is 20℃±2℃, and the temperature during underwater curing for compressive strength measurement is 20℃±2.
℃.

【table】

【table】

[Concrete test]

After mixing cement, water, aggregate and hydraulic cement admixture according to the following, mixer 90
After kneading for seconds, the slump and air amount were measured, and after 30 and 60 minutes, the mixture was kneaded again and the slump and air amount were measured. A sample for compressive strength measurement was taken after 60 minutes. The amount of admixture added was adjusted so that the target slump immediately after kneading was a slump of 20±1 cm. The measurement method is JIS A1101 for slump, JIS A1122 for air volume, and JIS A1122 for compressive strength.
Compliant with JIS A1108. In addition, the concrete temperature is 20
℃±2℃, and samples for compressive strength measurement were cured in water at 20±2℃. Concrete mix (with admixture added) Cement: 450Kg/m ³ Asano ordinary Portland cement Coarse aggregate: 1006Kg/m ³ Ome crushed stone (maximum particle size 25mm) Fine aggregate: 747Kg/m ³ River sand from Oigawa Water: 162Kg/m m ³ (Total amount with admixture) Hydraulic cement admixture: As shown in Table 4 Water/cement ratio = 36% Fine aggregate ratio = 43%

[Table] *1 Same as Table 3
It can be seen that the product of the present invention exhibits sufficient water reduction properties when added in a small amount compared to the conventional product, and also far exceeds the conventional product in terms of slump retention. Example 4 Copolymers (), (), and () used in Example 3 were evaluated for general concrete formulation using the following concrete formulation.
The results are shown in Table 5. Concrete mix Cement: 300Kg/m ³ Asano ordinary Portland cement Coarse aggregate: 1012Kg/m ³ Ome crushed stone (maximum particle size 25mm) Fine aggregate: 815Kg/m ³ River sand from Oigawa Water: 166.0Kg/m ³ (with admixture Hydraulic cement admixture: As shown in Table 5 Water/cement ratio: 55.3% Fine aggregate ratio: 44.6% Target slump: 10 ± 1 cm Target air volume: 4.5 ± 0.5% (air volume adjustment Vinzol: Mt. Soukagakusha)

[Table] From Table 5, it can be seen that even in concrete formulations for general use, it shows good performance with a lower additive amount than conventional products. Example 5 Copolymer of 65 mol% maleic anhydride and 35% cyclopentene synthesized according to Reference Example 3 (number average molecular weight 2800, weight average molecular weight 4800, molecular weight
An experiment was carried out according to Example 1, except that a sodium salt having a polymer content of 20,000 or more (3%) was used. As a result, almost the same results as the experiment number of Example 1 were obtained.

Claims (1)

[Claims] 1 Number average molecular weight is 300 to 10,000, molecular weight is 20,000
Contains as an active ingredient a copolymer of 60 to 85 mol% of α,β-unsaturated dicarboxylic acid and 40 to 15 mol% of olefin, or a salt thereof, in which the above-mentioned high molecular weight portion is controlled to 10% by weight or less. A hydraulic cement admixture characterized by: