WO2007051723A2

WO2007051723A2 - Additives based on methyl guar for use in building compositions

Info

Publication number: WO2007051723A2
Application number: PCT/EP2006/067655
Authority: WO
Inventors: Mauro Tenconi; Moreno Gatto; Daniela Risica; Ugo Pfeiffer; Giuseppe Li Bassi
Original assignee: Lamberti Spa
Priority date: 2005-10-31
Filing date: 2006-10-23
Publication date: 2007-05-10
Also published as: ITVA20050059A1; WO2007051723A3

Abstract

The present invention refers to dry cementitious building compositions, such as ready-to-use cements, sand and cement mixtures, tile adhesives, stuccos based on cement and synthetic binders, fresh mortars, jointing compositions and the like, containing methyl guar having substitution degree higher than 1.5.

Description

ADDITIVES BASED ON METHYL GUAR FOR USE IN BUILDING COMPOSITIONS

Technical Field

[0001] The present invention relates to dry building cementitious compositions, such as ready-to-use cements, sand and cement mixtures, tile adhesives, stuccos based on cement and synthetic binders, fresh mortar compositions, jointing compositions, and the like, containing methyl guar having degree of substitution higher than 1.5; the invention also relates to the cementitious wet mortars that can be obtained from the aforesaid dry building cementitious compositions.

[0002] The dry building composition is usually made of cement mixed with a variable amount of sand; immediately prior to use, a proper amount of water is added to the composition, making it workable and allowing the spreading or the shaping of the obtained wet mortar.

[0003] The setting of wet mortar begins as soon as the building composition is admixed with water and it is a rather complex chemical process that leads to complex polymeric inorganic structures whose strong reciprocal interactions result in the formation of solid and strong masses.

[0004] In the setting process, many features are of importance and influence not only the speed at which setting occurs but also its final effectiveness, i.e. its solidity.

[0005] Among these features of fundamental importance are the content of water and the capability of the wet mortar to retain the proper amount of water during the whole setting process.

[0006] It is important that the wet mortar retains sufficient water until all the desired physical characteristics are obtained.

[0007] When considering tile mortars, for examples, the surfaces to which tiles are generally applied are porous and absorbent as such, and the porous and absorbent surfaces may absorb water from the wet mortar in the area of contact, thus creating defects in the setting which may at some point in time result in the separation of the tile from the surface to which it is attached.

[0008] One of the main problems encountered by the tile installer is a too rapid hardening of the wet mortar that prevents the adjustment of the tiles during their laying.

[0009] This problem is called "lack of open time" and/or "lack of adjustability time".

[0010] If, on the contrary, the content of water becomes excessive, even if only locally because of lack of homogeneity of the wet mortar or the surface, setting becomes too slow, due to a too flowing mixture. [0011] If this occurs, then the tile tends to slip down, dragged down by its own weight, and the resulting application becomes imprecise and difficult and working time grows longer.

[0012] Another issue in the handling of wet mortar is the fact that water in the mortar mixture acts as a lubricant for the solid particles when mortar is spread on the surface of the object to which it is to be applied.

[0013] The proper amount of water gives to the mixture the "pastiness" or "creaminess" suitable for a uniform, homogeneous and easy laying.

[0014] The rheological characteristics of the fresh wet mortar are very important and they depend on the kind and on the amount of the different components in the mixture.

[0015] The rheology of a mixture of sand, cement and water is not suitable for use as a wet mortar because of the lack of the above-mentioned characteristics, and more generally, because of its poor processing.

[0016] To overcome these problems additives are used in the formulation of mortars acting as retention aids and rheology modifiers.

[0017] These additives are generally synthetic or semi- synthetic polymers, i.e. chemically modified natural polymers, exhibiting the specific characteristic of bonding and coordinating a large amount of water once they are dissolved in water.

[0018] Nonionic cellulose ethers, such as methyl cellulose and hydroxyethyl cellulose, and guar derivatives having high molar substitution are the most relevant functional additives for building compositions, because they improve water retention, workability, consistency, open time, adhesion, setting time and air absorption.

[0019] Among these products, in particular, cellulose ethers are highly purified products whose preparation requires many sophisticated and complex steps. They are rather ex pensive products. Background Art

[0020] In literature many mixtures are described for use in cementitious building compositions.

[0021] In particular, in U.S. Pat. Nos. 4,487,864 and in 5,432,215 guar derivatives are cited among the natural products capable of increasing the viscosity of cementitious mortar, but it is taught to use them in combination with other rheology modifiers to reach the desired levels of viscosity and water retention; US 6,76,112 describes cementitious mortars additives containing at least a hydroxyalkyl guar derivative having a molar substitution higher than 0.7.

As far as the applicant knows, the use of methyl guar derivatives, and more specifically, the use of methyl guar derivatives having a degree of substitution higher than 1.5 as rheology modifiers and retention aids in cementitious building com- positions was never suggested.

[0022] The guar derivatives are semi-synthetic derivatives, which due to their low production cost are desirable as replacements for other products now in use.

[0023] Guar, or guar gum, is a polysaccharide belonging to the family of galactomannans and is extracted from a leguminosae, "Cyamopsis Tetragonolobus", that grows in the semi-dry region of tropical countries, particularly in India and in Pakistan.

[0024] The polysaccharide molecule of guar consists of a main linear chain of poly- mannose bearing branches of galactose units in a molar ratio of about 2: 1.

[0025] The guar commercially available generally have a molecular weight of from about 200,000 to about 500,000 daltons.

[0026] Guar alkyl derivatives, and more particularly methyl guar, are described in the literature, such as in US 4,169,945, CA 2,053,569 and in EP 235513, where a process for the preparation of alkyl guar derivatives useful in gypsum formulations is described; in this patent, it is reported that the described process does not result in the realisation of guar derivative which are utilisable as additives for cementitious compositions and that satisfactory results in gypsum formulations are obtained by using methyl guar having degree of substitution from 0.3 to 1.5; in the above-mentioned patent, only methyl guar having degree of substitution of 0.45 and 1.0 are exemplified. Disclosure of Invention

[0027] Surprisingly it has now been found that methyl guar derivatives having degree of substitution (DS) higher than 1.5 are particularly useful as additives for cementitious compositions, acting as excellent retention aids and improving the workability and consistency of the cementitious composition.

[0028] Dry building cementitious compositions containing from 0.05 to 2% by weight of methyl guar having methyl degree of substitution higher than 1.5, preferably from 1.7 to 3 are therefore a fundamental object of the present invention.

[0029] In the present text, with the expression "cementitious compositions" we mean compositions containing at least 10% by weight of cement.

[0030] Preferably, the dry building compositions of the invention contain from 50 to 85% of sand and from 15 to 50% by weight of cement.

[0031] The methyl guar useful for the realisation of the invention may be prepared by any of the methods which are described in the literature, such as by reaction of guar with an halo- alkyl compound, preferably with a iodo- or chloro- alkyl compound, or with other alkylating agents, such as dimethylsulfate, in the presence of stechiometric amounts of a strong base, such as an alkaline metal hydroxide, and preferably in the presence of sodium hydroxide.

[0032] Preferably, the methyl guar is purified by treatment with glyoxal, according to methods well known in the art.

[0033] In the present text, with the expression "methyl guar" we mean both guar derivatives which are only substituted with methyl groups and also guar derivatives which are substituted with methyl groups and hydroxyalkyl groups , such as hy- droxypropyl and hydroxyethyl.

[0034] The degree of substitution of the methyl guar of the invention, which at the most can be 3, is experimentally determined by NMR.

[0035] The dry building cementitious compositions of the invention may

[0036] contain one or more additives usually employed in the field, such as accelerators, (for example calcium formate), thickening agents (such as starch or starch derivatives or polyacrylamide or other synthetic thickeners, strong inorganic bases, such as calcium hydroxide or oxide, or sodium hydroxide and polymeric binders.

[0037] Examples of utilisable polymeric binders are vinyl polymers and copolymers in the form or dispersible powders, such as vinylacetate-ethylene copolymers.

[0038] The dry building cementitious compositions of the invention may further contain other rheology modifiers, such as hydroxypropyl guar, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, ethyl hydroxyethyl cellulose, hydroxybutyl methyl cellulose, hydroxyethyl hydroxypropyl cellulose.

[0039] The cementitious wet mortars that are prepared by gradually adding the above described dry cementitiuos compositions to water and by admixing are a further object of the present invention.

[0040] The correct amount of water is the one that makes it possible to obtain the cementitious wet mortar in the form of a slurry possessing a good workability and consistency.

[0041] Normally this amount ranges from 10 to 45, preferably from 15 to 30, parts by weight of water per 100 parts by weight of dry building composition.

[0042] Although methyl guar having substitution lower than 1.5 does not impart to cementitious compositions the desired performances, methyl guar having substitution higher than 1.5 revealed themselves to be perfectly suited as retention aids and rheology modifiers for building cementitious compositions, as it is exemplified here below. Example 1

[0043] Preparation of methyl guar having DS 1.7

[0044] 500 g of guar flour are charged into the reactor and, without stirring, two vacuum/N ₂ washing steps are operated.

[0045] The guar flour is heated to 40⁰C , while vigorously stirring.

[0046] 200 g of t-butanol, pre-heated at 40 ⁰C, are added, the mixture is stirred for 10 minutes and 650 g of 50% sodium hydroxide are charged. [0047] Still under inert atmosphere, the mixture is stirred for 30 minutes. 500 ml of iodomethane are charged, washing the line with 50 g of t-butanol. [0048] The mixture is heated to 70⁰C and left reacting at this temperature for 2 hours; after cooling down to 40⁰C, 80% acetic acid is added to pH 4.5-5 and stirred for 15 minutes. [0049] A mixture of 125 g of glyoxal in 200 g of t-butanol is then charged, the mixture is heated to 50⁰C and left reacting for 30 minutes.

[0050] T-butanol is removed by distilling it off at 70⁰C for about 20 minutes. [0051] When the distillation is ended, the reaction mixture is cooled down to 30⁰C, the product is washed with 5 parts of water at ambient temperature, dried at 65⁰C for about

10 minutes and milled until a product 100% passing through a 100 mesh screen is obtained.

[0052] The degree of substitution is determined by NMR. [0053] DS=1.7 [0054] Example 2 (comparative) [0055] Preparation of a methyl hydroxypropyl guar having methyl DS 0.7 and hdroxypropyl molar substitution (MS) 2.0. [0056] 600 g of guar flour are charged into the reactor and without stirring two vacuum/N₂ washing steps are operated.

[0057] The guar flour is heated to 40⁰C , while vigorously stirring. [0058] 200 g of t-butanol, pre-heated at 40 ⁰C, are added, the mixture is stirred for 10 minutes and a mixture made of 50 g of 50% sodium hydroxide and 100 g of water are charged.

[0059] Still under inert atmosphere, the mixture is stirred for 30 minutes. [0060] 350 g of propylene oxide are gradually added at pressure not higher than 3.5 and maintaining the temperature at 70-75⁰C for Ih and 10'. [0061] 500 ml of iodomethane mixed with 50 of t-butanol are charged. [0062] The mixture is heated to 70⁰C and left reacting at this temperature for 2 hours; after cooling down to 40⁰C, 510 g of 50% sodium hydroxide are added and stirred for about

20 minutes. [0063] 400 ml of iodomethane are charged, washing the line with 100 g of t-butanol. The mixture is heated to 70⁰C and left reacting at this temperature for 2 hours [0064] A mixture of 150 g of glyoxal in 240 g of t-butanol is then charged, the mixture is heated to 50⁰C and left reacting for 30 minutes.

[0065] T-butanol is removed by distilling it off at 70⁰C for about 20 minutes. [0066] When the distillation is ended, the reaction mixture is cooled down to 30⁰C and 100 g of 80% acetic acid are added, stirring for about 20 minutes at 40⁰C. [0067] The product is cooled down to 30⁰C, washed with 5 parts of water at ambient temperature, dried at 65⁰C for about 10 minutes and milled until a product 100% passing through a 100 mesh screen is obtained.

[0068] The DS and MS are determined by NMR. [0069] DS=0.7 [0070] MS=2.0 [0071] APPLICATION TESTS [0072] A cementitious composition (Base Composition) is prepared by combining the following ingredients (parts by weights):

[0073] Dolomite carbonate (0- 0.1 mm) 32.7 [0074] Dolomite carbonate (0.1- 0.4 mm) 19.7 [0075] Dolomite carbonate (0.4- 0.9 mm) 14.8 [0076] Dolomite carbonate (0.9- 1.2 mm) 14.8 [0077] Portland Cement 42.5 15 [0078] Lime 3 [0079] Three cementitious building compositions are prepared by adding to three portions of Base Composition 0.12% by weight of a rheology modifier and homogenising, as reported in Table 1.

[0080]

Table 1

[0081] (1) Comparative [0082] (2) Esacol HS 20 (from Lamberti SpA) [0083] [0084] The building compositions of Table 1 are evaluated by measuring their water retention, consistency, specific gravity, time to obtain a homogeneous ready to use wet compound and workability, according to the methods here below described.

[0085] All test are performed at standard conditions (23⁰C and 50% r.h.) [0086] For the application tests, 100 parts by weight of the dry compostions are added to 21 parts by weight of water and the wet mortar is mixed until uniform consistency.

[0087] [0088] Determination of water retention - Vacuum Method: [0089] Materials and instruments:

1. Chronometer

2. Technical balance with at least a double decimal digit

3. Filter paper (black ribbon) diameter 90mm

4. Buckner funnel about 100 mm diameter ( about n 97 holes with 2,5 mm diameter).

5. Vacuum flask.

6. Vacuum pump. [0090] Procedure

1. Put the buckner on the vacuum flask and apply vacuum.

2. Place the filter paper into the buckner and wet it with water.

3. Set the vacuum pump going for at least 2 minutes, to get rid of the water in excess.

4. Remove vacuum, weigh the buckner with the filter paper and record the weight.

5. Fill the buckner with about 300 g wet mortar uniformly, trying to avoid air bubbles entrapping.

6. Record the whole system weight (buckner + wet mortar).

7. Put on the funnel with the rest of apparatus.

8. Filter it under vacuum of 800 millibar.

9. Every 5 minutes, weigh the system again, and record the resulting weight, as rapidly and accurately as possible. Repeat this operation four times for a total of 20 minutes.

[0091] Calculating and reporting results

[0092] After the test the following values can be noted:

[0093] P_τ: weight of the funnel with filter paper.

[0094] P_L: weight of the funnel with the wet mortar.

[0095] P_{L I};P_{L 2};P_{L 3};P_{L 4}: weights of the funnel after 5,10,15,20 minutes.

[0096] W₀: % of water used to prepare the mortar.

[0097] The wet mortar weight used for the test is given by:

[0099] The percentage of water in the wet mortar is obtained as follows:

[0100] W _TEST = P_O X W_OZ IOO

[0101] Q is the water quantity lost after the tests and is obtained from:

₁

[0103] Time 2 Q₂= P_L - P_{L 2}

3

[0105] Time 4 Q₄= PL - PL₄ [0106] The percentage of water retained is obtained as follows:

[0107] W_R = [ (W _TEST - Q ) / W _TEST] X 100

[0108] For each measurement time (Time 1, 2, 3, 4, etc) the value Q₁, Q₂, Q₃, Q₄ etc. is used. [0109]

[0110] Determination of consistency :

[0111] Materials and instruments

1. Shock table

2. Iron cone ( h= 60mm, lower diam. = 100mm , upper diam. = 60mm)

3. 200 mm calliper [0112] Pocedure

1. Put the cone on the shock table centre

2. Fill up the container wet mortar and pay attention to avoid air bubbles entrap ping by using the suitable pestle.

3. Remove the cone and use the calliper to measure the diameter, which is the average of two perpendicular diameters, of the resulting cake.

4. Repeat the determination after every 5 shocks.

5. The diameter determination is usually determined after 5, 10 and 15 shocks [0113] The flow is expressed in mm and it corresponds to the average diameter measured after the shocks. [0114]

[0115] Determination of specific gravity :

[0116] Materials and instruments

1. Technical balance with at least a double decimal digit

2. Density bottle: container with a known volume [0117] Procedure

1. Set the density bottle.

2. Fill up the container with wet mortar and pay attention to avoid air bubbles entrapping. Then weigh the instrument again.

[0118] Specific gravity is the ratio between the material net weight and the known volume of density bottle.

[0119] Specific gravity is expressed in Kg/1. [0120]

[0121] Determination of time to obtain a homogeneous fresh wet mortar:

[0122] Materials and instruments

1. Chronometer

2. A two speed Hobart machine [0123] Procedure [0124] The test is performed with a Hobart machine, at the lowest speed , on a minimum quantity of 1000 g of dry cementitious composition that are added to the proper amount of water in 15 seconds. [0125] Mixing is performed until homogeneity is reached: all fractions, aggregates, additives and liquids must be homogeneously distributed in the wet mortar, that must be plastic and flowing, free of rupture zones. [0126] The time in seconds starting from the beginning of the addition of the dry composition is recorded. [0127] [0128] Determination of workability: [0129] Workability is determined practically. In Table 2 (***) means good workability, (****) means very good workability.

[0130] The results of the application tests are reported in Table 2. [0131] [0132] [0133]

Table 2

Claims

[0001] Dry cementitious building compositions containing from 0.05 to 2% by weight of a methyl guar having methyl degree of substitution higher than 1.5. [0002] Dry cementitious building compositions according to claim 1., wherein the degree of substitution is from 1.7 to 3. [0003] Dry cementitious building compositions according to claim 1. or 2., containing from 50 to 85% by weight of sand and from 15 to 50% of cement. [0004] Cementitious wet mortars prepared by admixing the dry composition of any of claims from 1. to 3. with from 10 to 45 parts by weight of water each 100 parts by weight of dry composition . [0005] Cementitious wet mortars according to claim 4., prepared with from 15 to 30 parts by weight of water.