USE OF A GEOPOLYMER WITH SUPERABSORBENT POLYMER

Abstract

The present invention relates to a composite material including at least one superabsorbent polymer in a geopolymer matrix as a material for 3D printing.

Claims

1- Use of a composite material including at least one superabsorbent polymer in a geopolymer matrix as a material for 3D printing.

2- Use according to claim 1, characterised in that said superabsorbent polymer is chosen in the group constituted by: polymers resulting from polymerisation with partial cross-linking of water-soluble ethylenic unsaturated monomers, such as acrylic, methacrylic or vinylic monomers, in particular, cross-linked and neutralised poly(meth)acrylates; and salts, in particular, alkaline salts such as sodium or potassium salts of these polymers; starches grafted by polyacrylates; acrylamide/acrylic acid copolymers, typically in salt-form, in particular, alkaline salts such as sodium or potassium salts; acrylamide/acrylic acid grafted starches, typically in salt-form, particularly alkaline salts, and in particular, sodium or potassium salts; salts, particularly alkaline salts, and in particular, sodium or potassium salts of, carboxymethylcellulose; salts, particularly alkaline salts, and in particular, sodium or potassium salts of, cross-linked polyaspartic acids; salts, particularly alkaline salts, and in particular, sodium or potassium salts of, cross-linked polyglumatic acids and their mixtures.

3- Use according to claim 1, characterised in that said superabsorbent polymer is a sodium or potassium poly(meth)acrylate.

4- Use according to any one of the claim 1, characterised in that said composite material is prepared from a formulation including: an alumino-silicate source; an activation solution and at least one superabsorbent polymer.

5- Use according to any one of the claim 1, characterised in that said composite material is prepared by a preparation method consisting of mixing together the different formulation elements, such as defined in claim 4.

6- Use according to any one of the claim 1, characterised in that said composite material is prepared by a preparation method consisting of: a) preparing an activation solution including at least one superabsorbent polymer, b) adding at least one alumino-silicate source to the solution obtained in step (a), c) subjecting the mixture obtained in step (b) to conditions enabling the hardening of the geopolymer.

7- Use according to any one of the claim 1, characterised in that said composite material is prepared by a preparation method consisting of: a) adding at least one alumino-silicate source to an activation solution, b) adding at least one superabsorbent polymer to the mixture obtained in step (a), c) subjecting the mixture obtained in step (b) to conditions enabling the hardening of the geopolymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0131] FIGS. 1A to 1E are photographs taken under an optical microscope of sodium polyacrylate (Aquakeep) in different environments: in the dry state (FIG. 1A), 0.2% by mass of Aquakeep in water (FIG. 1B), 0.2% by mass of Aquakeep in an activation solution (FIG. 1C), 0.5% by mass of Aquakeep in an activation solution (FIG. 1D) and 1% by mass of Aquakeep in an activation solution (FIG. 1E).

[0132] FIG. 2 presents the impact of the Aquakeep concentration on the rheology of the activation solution.

[0133] FIGS. 3A and 3B respectively present the impact of the Aquakeep concentration on the elasticity and on the setting time. In FIG. 3A, Gref corresponds to the measurement carried on a reference geopolymer without Aquakeep and G0.2%, G0.5% and G1% respectively correspond to the measurements on the geopolymers including 0.2%, 0.5% and 1% by mass of Aquakeep. In FIG. 3B, tan d ref corresponds to the measurement carried out on a reference geopolymer without Aquakeep and tan d 0.2%, tan d 0.5% and tan d 1% respectively correspond to the measurements on the geopolymers including 0.2%, 0.5% and 1% by mass of Aquakeep.

[0134] FIGS. 4A and 4B respectively present the impact of the geopolymerisation time (30 minutes t30, 1 hour 30 minutes t1h30, 1 hour 50 minutes t1h50 and 2 hours 30 minutes t2h30) on the stress according to the shearing rate and on the viscosity according to the shearing rate, the caption 0.5% SA corresponding to one single activation solution containing 0.5% of sodium polyacrylate.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0135] I. Materials Used and Choice of Formulation.

[0136] In all the examples below, the alumino-silicate source used is metakaolin. The metakaolin used is Pieri Premix MK (Grace Construction Products), of which the composition determined by fluorescence X is recorded in Table 1. The specific surface area of this material, measured by the Brunauer-Emmet-Teller method, is equal to 19.9 m.sup.2/g and the average diameter of the particles (d.sub.50), determined by laser granulometry, is equal to 5.9 m.

TABLE-US-00001 TABLE 1 Chemical composition of the metakaolin used. Mass % SiO.sub.2 Al.sub.2O.sub.3 CaO.sub.3 Fe.sub.2O.sub.3 TiO.sub.2 K.sub.2O Na.sub.2O MgO P.sub.2O.sub.5 Metakaolin 54.40 38.40 0.10 1.27 1.60 0.62 <0.20 <0.20 /

[0137] In all the examples below, the compensating cations and mineralisation agents retained are alkaline hydroxides, inserted in the form of NaOH granules (Prolabo, Rectapur, 98%).

[0138] A sodium silicate like Betol 39T (Woellner) is also implemented in all the examples below.

[0139] Finally, the superabsorbent polymer implemented in all the examples below is a sodium polyacrylate (PaaNa) commercialised under the brand Aquakeep 10SH-NF (SUMIMOTO SEIKA). FIG. 1 presents a series of photographs of the Aquakeep taken under optical microscope in different environments. In the dry state, the latter is presented in the form of agglomerates of spherical beads, of which the average diameter is 25 m (data from the supplier) (FIG. 1A). During the addition of 0.2% of Aquakeep in the water, it swells by absorbing water (FIG. 1B). FIGS. 1C, 1D and 1E present the impact of the Aquakeep content in a geopolymer activation solution (basic alkaline silicate solution). The more the Aquakeep concentration is high, the more the size of the nodules decreases, certainly because of an absorption of a weaker solution, but also because of a depolymerisation of the cross-linked network.

[0140] The geopolymer formulation that conforms with the present invention, used in the examples, is given in Table 2 below:

TABLE-US-00002 TABLE 2 Geopolymer formulation used. Composition: mass (g) Quantity of Aquakeep (g) Geo-SAP Metakaolin = 60.02 0.279 -> 0.2% by mass NaOH = 11.8 0.699 -> 0.5% by mass Alkaline silicate = 58.61 1.397 -> 1% by mass Water = 9.32

[0141] II. Preparation and Characterisation of the Geopolymer that Conforms with the Present Invention.

[0142] II.1. Preparation of the Activation Solution Containing Aquakeep.

[0143] The alkaline silicate solution is prepared at room temperature, then Aquakeep is added to this activation solution using a magnetic stirrer. This solution gels by swelling the cross-linked polymers, due to the absorption of a certain quantity of saline solution, the degree of gelling increasing with the Aquakeep concentration.

[0144] The activation solutions containing Aquakeep have been characterised rheologically (FIG. 2) and it is observed that for a 0.2% Aquakeep concentration, the solution behaves like a Newtonian fluid, whereas for a 0.5% or 1% Aquakeep concentration, a gelled solution appears (G>G) with a flow threshold.

[0145] For a 0.5% Aquakeep concentration, the threshold is around equal to 4 Pa and, for a 1% Aquakeep concentration, the threshold is equal to around 45 Pa. These flow curves can be perfectly defined by a Herschel-Bulkley-type law.

[0146] II.2. Addition of Metakaolin and Characterisation of the Reopolymer Obtained.

[0147] When the initial solution (activation solution+Aquakeep) is ready, the metakaolin is added to it, at room temperature, by relatively sustained stirring for a duration of around 10 minutes and the geopolymerisation reactions take place. The geopolymer is formed around SAP grains and the material obtained is left to harden.

[0148] Elastic Module and Setting Time

[0149] FIG. 3A presents the development of the elastic module (G) over time and according to the Aquakeep content. When the concentration increases, the elasticity increases because of the interactions between the PaaNa nodules and the setting time decreases (maximum on Tan delta in FIG. 3B), since sodium is added in the solution, and therefore the Si/Na ratio decreases. The elasticity increases by more than two decades, only with an addition of 1% by Aquakeep mass.

[0150] Rheological Flow Behaviour

[0151] The rheological flow behaviour has also been determined in order to obtain the development of the flow threshold and the viscosity with the shearing rate.

[0152] FIG. 4A enables to determine the flow threshold (plateau which is drawn at a low shearing rate). It thus goes from 4 Pa for the activation solution to around 15-20 Pa at the end of 2 hours 30 minutes of geopolymerisation. It must be noted that the rheological behaviour differs a little from that of the activation solution.

[0153] It would appear that the relaxation time, characteristic of the geopolymer paste with Aquakeep is longer, and that consequently, the stress plateau appears at a low shearing rate. This characteristic is truly found in the development of viscosity where a Newtonian plateau is drawn at a high shearing rate (FIG. 4B). Another useful characteristic is the shear-thinning characteristic (decrease of viscosity with the shearing rate) of the mixture which is beneficial for injection methods.

[0154] Adhesion Properties

[0155] Concerning the increase of adhesion properties, observation at laboratory-level enable this increase to be observed.

[0156] Indeed, the act of adding sodium polyacrylate (PaaNa) enables a better affinity with plastic pots wherein the mixtures are produced.

REFERENCES

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