Mould release agent with corrosion inhibiting properties and method for casting cementitious compositions using the same

Abstract

The present invention relates to mould release agents comprising at least one oil and at least one corrosion inhibitor. The present invention also relates to methods for casting of cementitious compositions using the mould release agents comprising at least one oil and at least one corrosion inhibitor.

Description

Technical Field

[0001] The present invention relates to mould release agents with corrosion protection properties, especially for cementitious compositions.Background of the invention

[0002] It is known since long time to cast cementitious compositions such as concrete into formworks or moulds. Elements of desired shape can be manufactured thereby. One challenge is to prevent adhesion of the cementitious composition to the mould. A well-established technology is to use mould release agents for this purpose. Another challenge is the prevention of corrosion of metal moulds, especially steel moulds, when in contact with cementitious compositions. Due to their aggressive chemical nature, wet cementitious compositions frequently lead to corrosion of metal moulds. Corroded moulds cannot be reused and often must be discarded. Additionally, corrosion of moulds may strongly influence the surface appearance of cementitious materials cast and hardened therein. Especially with precast elements or fair-faced concrete, discoloration of the surface by corrosion of moulds is problematic and may lead to unusable elements.

[0003] It is known that corrosion inhibitors can be formulated into mould release agents used for concrete casting. For example DE 4418807 A1 (Henkel) discloses mould release agents comprising an aqueous emulsion of long-chain alcohol and corrosion inhibitor. Also, FR 2204678 (Oxydro) discloses water-based mould release agents comprising corrosion inhibitors. However, known mould release agents comprising corrosion inhibitors are typically water-based emulsions which are inherently instable and require suitable emulsifiers to increase shelf life.

[0004] It would be desirable to have available mould release agents with corrosion inhibiting properties and which are stable over longer periods of time.Summary of the invention

[0005] It is an object of the present invention to provide improved mould release agents with corrosion inhibiting properties. Specifically to prevent corrosion of metal moulds, especially steel moulds, used for casting of cementitious compositions. In particular, the mould release agents should have improved stability and therefore longer shelf life and can be produced by simple mixing.

[0006] It has surprisingly been found that certain corrosion inhibitors can be easily formulated in an oil phase and give particularly good mould release agents with corrosion inhibiting properties for metal moulds, especially steel moulds. The objective of the present invention is therefore solved as claimed in claim 1.

[0007] In particular, the shelf life of mould release agents of the present invention is more than one year, especially between two and three years. This means that a mould release agent of the present invention can be stored for more than one year, especially between two and three years, without significant change of performance. As a comparison, the shelf life of emulsion based mould release agents typically is one year or less.

[0008] Further aspects of the present invention are the subject matter of independent claims.

[0009] Preferred embodiments are the subject matter of dependent claims.Detailed Ways

[0010] In a first aspect the present invention relates to a mould release agent comprising a) at least one oil, b) at least one corrosion inhibitor selected from the group consisting of borates, sulfonates, carboxylates, phosphates, amines, amides, and imidazolines, each having at least one carbon chain with at least 5 carbon atoms, c) optionally antioxidants, pour point depressants, viscosity modifiers, wetting agents, defoamers, dispersants, anti-wear additives, and / or extreme pressure additives, wherein the mould release agent is essentially free from water.

[0011] Very preferably, the mould release agent is for casting of cementitious compositions, especially concrete.

[0012] The mold release agent of the present invention comprises at least one oil and is essentially free form water. The term "essentially free" within the present context means that the amount of water present is less than 1 w%, preferably less than 0.1 w%, especially less than 0.01 w%, relative to the total weight of the mold release agent. Preferably, the mold release agent is free from water.

[0013] It is particularly preferred, that the mould release agent of the present invention is in the form of a continuous phase. Especially, this means that the mould release agent of the present invention does not comprise and discontinuous phase. A mould release agent of the present invention very preferably is not in the form of an emulsion. Very preferably, the mold release agent of the present invention is in the form of a solution.

[0014] According to embodiments, the mould release agent comprises at least one oil selected from the group consisting of vegetable oils, methyl esters of fatty acids, synthetic oils, preferably paraffinic oils, especially API group III mineral oils, and mixtures thereof. Preferably, the mould release agent of the present invention does not comprise any other oil.

[0015] According to preferred embodiments, the at least one oil is a mixture of methyl esters of vegetable oils and API group III mineral oils or is a mixture of methyl esters of fatty acids and API group III mineral oils. 1:1 mixtures by weight can be preferred, however, other mix ratios are also possible. Preferably, the mould release agent of the present invention does not comprise any other oil.

[0016] The at least one corrosion inhibitor is selected from the group consisting of borates, sulfonates, carboxylates, phosphates, amines, amides, and imidazolines, each having at least one carbon chain with at least 5 carbon atoms. This means that the at least one corrosion inhibitor is a molecule comprising a carbon chain with at least 5 carbon atoms and additionally comprising at least one of a borate, a sulfonate, a carboxylate, a phosphate, an amine, an amide, and an imidazoline group. In other words, corrosion inhibitors of the present invention comprise a carbon chain with at least 5 carbon atoms and at least one of a borate, a sulfonate, a carboxylate, a phosphate, an amine, an amide, and an imidazoline group bonded thereto. The borate, sulfonate, carboxylate, phosphate, amine, amide, and / or imidazoline groups can be bonded to the carbon chain via a linking group such as an ester or ether group or an aromatic moiety.

[0017] "Amines" within the context of corrosion inhibitors especially also comprise alkanolamines.

[0018] According to particularly preferred embodiments, the mould release agent of the present invention comprises at least one corrosion inhibitor selected from the group consisting of N-methyl-N-(1-oxo-9-octadecenyl)glycine, bis(C8-C10-alkyl)naphthalenesulphonate, isotridecyl phosphate, N,N-dimethylamide of tall-oil fatty acid, (tetrapropenyl)succinic acid, N-oleoylsarcosine, 2-(2-heptadec-8-enyl-2-imidazolin-1-yl)ethanol, rosin acids, resin acids, and / or reaction products of long-chain carboxylic acids with alkanolamine and boric acid, and mixtures thereof. Preferably, the mould release agent of the present invention does not comprise any other corrosion inhibitor.

[0019] Reaction products of long chain carboxylic acids with alkanolamine and boric acid are particularly preferred.

[0020] Suitable long chain carboxylic acids in particular are natural with 8 - 26 carbon atoms. Examples are tall oil, resin acids such as abietic acid, and fatty acids such as oleic acid, myristic acid, palmitic acid, stearic acid, linolic acid, and linolenic acid. It is possible and also preferred to use mixtures of fatty acids to produce the reaction product with alkanolamine and boric acid.

[0021] Very preferably, for the present context, a mixture of carboxylic acids having an average number of C atoms of between 16 - 26, preferably 18 C atoms, is used for the reaction with alkanolamine and boric acid.

[0022] A preferred alkanolamine useful for the reaction with long chain carboxylic acid and boric acid is diethanolamine.

[0023] Suitable reaction conditions for the reaction of long-chain carboxylic acids with alkanolamine and boric acid are for example as follows. The long chain carboxylic acid is reacted with diethanolamine in dry state in equimolar amounts at a temperature of 140 - 170 °C, preferably 150 - 155 °C, for 8h with formed water being distilled off. The resultant reaction product is reacted with boric acid in a molar ratio of from 3 - 0.9, preferably a molar ratio of 1. Preferred molar ratios depend on the OH-functionality of the alkanolamine used, a preferred ratio of 1 relates to difunctional alkanolamine such as diethanolamine. The reaction with boric acid can be carried out in solution with toluene or xylene as solvent for about 6h at refluxing temperature. Formed water is azeotropically distilled off upon completion of the reaction, the product solution is cooled, filtered, and the solvent is evaporated.

[0024] According to embodiments, the mould release agent of the present invention comprises or consists of a corrosion inhibitor which is a reaction product of a carboxylic acid or a mixture of carboxylic acids having an average of 16 - 26 C atoms, preferably 18 C atoms, with diethanolamine and boric acid.

[0025] Reaction products of long chain carboxylic acids with alkanolamine and boric acid typically are a complex mixture of compounds.

[0026] One preferred reaction product of long chain carboxylic acids with alkanolamine and boric acid is known under CAS number 91770-03-5.

[0027] According to embodiments, the mould release agent of the present invention comprises the corrosion inhibitor in an amount of 0.5 - 15 w%, preferably 1 - 10 w%, more preferably 2 - 5 w%, relative to the total weight of the mould release agent.

[0028] According to embodiments, the mould release agent of the present invention comprises or consists of, in each case relative to the total weight of the mould release agent, 0.5 - 15 w%, preferably 1 - 10 w%, more preferably 2 - 5 w%, of at least one corrosion inhibitor, 0.1 - 1 w% of antioxidants, pour point depressants, viscosity modifiers, wetting agents, defoamers, dispersants, anti-wear additives, and / or extreme pressure additives, and the rest to 100 w% of at least one oil, preferably a 1:1 by weight of methyl esters of vegetable oils and API group III mineral oils or is a mixture of methyl esters of fatty acids and API group III mineral oils.

[0029] A mould release agent of the present invention can be used for the treatment of metal moulds, especially steel moulds, for casting of cementitious compositions. Thereby, the mould release agent is applied to the metal mould. Application of the mould release agent can be done by pouring, painting, brushing, polishing, spraying, dipping, or other suitable means. A very preferred application is by spraying.

[0030] Moulds within the present context are compartments with an inner volume defined by impermeable surfaces and at least one opening for the casting of cementitious material. During casting the inner volume is filled with a cementitious composition, preferably a cementitious composition in a wet state. The cementitious composition is in close contact with the surfaces defining the inner volume after casting. The surfaces defining the inner volume come in contact with a cementitious composition during casting.

[0031] Moulds for the casting of cementitious compositions can be made of various materials. Typical materials are metal or wood. A metal mould within the present context can be made of any material but must have at least one surface defining the inner volume which is made of metal. A preferred metal is steel. The term "metal moulds" within the present context therefore encompasses steel moulds but also encompasses wooden moulds where at least one inner surface is covered by a metal, preferably steel.

[0032] In another aspect, the present invention relates to a metal mould, preferably a steel mould, for casting of cementitious compositions, comprising at least one surface of the metal mould to be in contact with a cementitious composition which is treated with a mould release agent as described above.

[0033] All features and embodiments as described above also apply to this aspect.

[0034] In another aspect, the present invention relates to a method for the casting of cementitious compositions comprising the steps of a) providing a metal mould, preferably a steel mould, b) applying a mould release agent comprising at least one oil and at least one corrosion inhibitor to at least one surface of the metal mould to be in contact with a cementitious composition, to prepare a treated metal mould, and c) casting a cementitious composition, preferably wet concrete, into the treated metal mould.

[0035] All features and embodiments as described above also apply to this aspect.

[0036] A cementitious composition within the present context comprises at least one cementitious binder. A cementitious binder for example is a cement according to standard EN 197-1:2011 or EN 197-5:2021.

[0037] According to embodiments, in a method of the present invention, the cementitious composition comprises a composite cement.

[0038] According to embodiments, in a method of the present invention, the composite cement comprises between 5 - 94 w%, preferably 20 - 79 w%, more preferably 35 - 64 w% of Portland cement and between 6 - 95 w%, preferably 21 - 80 w%, more preferably 36 - 65 w% of at least one supplementary cementitious composition, in each case relative to the total dry weight of the composite cement.

[0039] According to embodiments, in a method of the present invention, the composite cement comprises Portland cement and at least one supplementary cementitious composition selected from the group consisting of limestone, ground granulated blast furnace slag, basic oxygen furnace slag, silica fume, fly ash, burnt oil shale, natural pozzolane, calcined clay, and mixtures thereof.

[0040] Very preferably, a cementitious composition of the present invention comprises a composite cement of the type CEM II, CEM III, CEM IV, CEM V, or CEM VI according to standard EN 197-1:2011 or EN 197-5:2021.

[0041] A cementitious composition within the present context further comprises at least one aggregate. Typical aggregates are for example rock, crushed stone, gravel, slag, sand, especially quartz sand, river sand and / or manufactured sand, recycled concrete, glass, expanded glass, hollow glass beads, glass ceramics, volcanic rock, pumice, perlite, vermiculite, quarry wastes, raw, fired or fused earth or clay, porcelain, electrofused or sintered abrasives, firing support, silica xerogels. Aggregates useful for the present invention can have any shape and size typically encountered for such aggregates. Especially preferred aggregates are sand and / or gravel.

[0042] A cementitious composition of the present invention may additionally comprise fine filers such as finely ground limestone or dolomite. A cementitious composition may also comprise additives and / or admixtures as defined in standard EN 206:2021 and standard EN 934-2:2012. Very preferably, at least one plasticizing or superplasticizing admixture is present.

[0043] A cementitious composition may be in dry form or in wet form. Dry form means that the cementitious composition is in the form of a free flowing powder. Wet form means that the cementitious composition is mixed with water. Preferably, the cementitious composition is in a wet form. The amount of water present in a wet cementitious composition can be between 20 - 60 w% relative to the total dry weight of cementitious binder present.

[0044] A very preferred cementitious composition within the present context is wet concrete.

[0045] According to embodiments, in a method of the present invention, the mould release agent is in the form of a continuous phase.

[0046] According to embodiments, in a method of the present invention, the mould release agent comprises an oil selected from the group consisting of vegetable oils, methyl esters of fatty acids, synthetic oils, preferably paraffinic oils, especially API group III mineral oils, and mixtures thereof, and comprises a corrosion inhibitor selected from the group consisting of N-methyl-N-(1-oxo-9-octadecenyl)glycine, bis(C8-C10-alkyl)naphthalenesulphonate, isotridecyl phosphate, N,N-dimethylamide of tall-oil fatty acid, (tetrapropenyl)succinic acid, N-oleoylsarcosine, 2-(2-heptadec-8-enyl-2-imidazolin-1-yl)ethanol, rosin acids, resin acids, and / or reaction products of long-chain carboxylic acids with alkanolamine and boric acid, and mixtures thereof.

[0047] The mould release agent is preferably applied by spraying. Application in an amount of mould release agent of between of 10 - 100 ml per m 2< of surface of the mould is preferred. If lower amounts are applied the positive effects on demoulding and / or corrosion inhibition cannot be achieved. If higher amounts are applied, the aesthetic appeal of the demoulded cementitious composition may be negatively affected and cost increase.

[0048] It is possible that a method of the present invention additionally comprises a step of hardening the cast cementitious composition.

[0049] Hardening of the cementitious composition starts by the addition of water and proceeds with time. Mechanical strength, especially compressive strength, is developed thereby. Hardening of the cementitious composition is done in the mould. Demoulding of the hardened cementitious composition is possible when a certain mechanical strength has been reached. This can be the case after a few hours or days. Hardening can be done under various conditions. For example, hardening can be done at room temperature and normal pressure. It is also possible to harden at elevated temperatures such as 40 °C or higher. Steam hardening is also possible.

[0050] In another aspect, the present invention relates to an element made of cementitious composition, especially a hardened concrete element, obtainable by a method as described above.

[0051] In particular, the element can be a precast element such as a concrete pipe, a stair, a partitioner, a frame, a slab, a sleeper, or a bridge element. Likewise, the element can be part of a building such as a wall. Especially, the element is a fair-faced concrete element.Examples Example 1

[0052] In a first set of examples, the effectiveness of different mould release agents to prevent corrosion of steel moulds used for casting of cementitious compositions was tested.

[0053] First, a cement electrolyte suspension was prepared by suspending a CEM III / A, 52.5 L CE PM-ES CP1 NF in water at 25 w%, followed by filtering the suspension to obtain an electrolyte solution. The electrolyte solution had a conductivity of 11850 µS / cm.

[0054] Next, the mould release agents (MRA) were prepared by dissolving the respective corrosion inhibitors in the amounts indicated in below table 1 in a 1:1 mixture of methyl ester of fatty acid and of paraffinic oil of API group III.

[0055] MRA prepared were spry applied on steel plates (pre-heated to 40°C) in an amount of 12.5 ml / m 2< . Then, droplets of the electrolyte solution were placed on top of the treated steel plates. After 24 hours at 23°C, the remaining droplets were wiped of and the steel surface was visually inspected for signs of corrosion according to the following scheme: 1: no signs of corrosion, 2: light, localized corrosion without penetration, 3: light, extended corrosion without penetration, 4: severe, localized corrosion with penetration, 5: severe, extended corrosion with penetration.

[0056] The below table 1 shows the results of corrosion test obtained. Table 1: MRA prepared (all numbers in w% relative to the total weight of MRA)Test Reaction product of a mixture of carboxylic acids having an average of 18 C atoms with diethanolamine and boric acid*Isotridecyl phosphateCalcium bis(C8-C10-alkyl) naphthalene sulphonate**Result of corrosion test1 00052 10013 20014 50015 100016 150017 01018 02019 050110 0100211 0150112 001313 002314 005115 0010116 00151* CAS number 91770-03-5 **CAS number 939-717-7

[0057] Test 1 is a comparative example not according to the present invention. For test 1 no corrosion inhibitor has been dissolved in the API group III mineral oil and the pure oil has been used as MRA. Severe, extended, and penetrating corrosion resulted. Corrosion was mitigated by the use of mould release agents according to the present invention as shown in tests 2-16.Example 2

[0058] For example 2 the bottom plates of a steel mould was sprayed with a mould release agent according to the invention comprising 2 w% of the reaction product of a mixture of carboxylic acids having an average of 18 C atoms with diethanolamine and boric acid in API group III mineral oil in an amount of 12.5 ml / m 2< . As a reference, a second steel mould was sprayed with the pure API group III mineral oil in the same amount.

[0059] A cementitious composition was prepared comprising 145 kg / m 3< of CEM III / A 52.5 L, 45 kg / m 3< of sand (0-4 mm), 1.31 kg / m 3< of a polycarboxylate ether based superplasticizer, and 65 kg / m 3< of water.

[0060] The cementitious composition was cast into the respective sprayed steel mould and left for hardening for 24 h at 40°C. Subsequently, the hardened cementitious composition was demoulded and the bottom plates of the steel moulds were visually inspected for signs of corrosion.

[0061] This test was replicated three times with the following results. ▪ Demoulding was easily possible in all cases without adhesion of the cementitious material to the mould and without material breakage or material transfer. ▪ Bottom plate sprayed with pure API group III mineral oil (not according to the invention): average of 127 corrosion spots per m 2< . ▪ Bottom plate sprayed with MRA according to the invention: average of 13 spots per m 2< .

[0062] It is thus shown that a composition of the present invention is effective as a mould release agent and efficiently reduces the corrosion of moulds for cementitious compositions.

Claims

1. A mould release agent comprising a) at least one oil, b) at least one corrosion inhibitor selected from the group consisting of borates, sulfonates, carboxylates, phosphates, amines, amides, and imidazolines, each having at least one carbon chain with at least 5 carbon atoms, c) optionally antioxidants, pour point depressants, viscosity modifiers, wetting agents, defoamers, dispersants, anti-wear additives, and / or extreme pressure additives, wherein the mould release agent is essentially free from water.

2. The mould release agent as claimed in claim 1, characterized in that it is in the form of a continuous phase.

3. The mould release agent as claimed in any of the previous claims, characterized in that the at least one oil is selected from the group consisting of vegetable oils, methyl esters of fatty acids, synthetic oils, preferably paraffinic oils, especially API group III mineral oils, and mixtures thereof.

4. The mould release agent as claimed in any of the previous claims, characterized in that the corrosion inhibitor is selected from the group consisting of N-methyl-N-(1-oxo-9-octadecenyl)glycine, bis(C8-C10-alkyl)naphthalenesulphonate, isotridecyl phosphate, N,N-dimethylamide of tall-oil fatty acid, (tetrapropenyl)succinic acid, N-oleoylsarcosine, 2-(2-heptadec-8-enyl-2-imidazolin-1-yl)ethanol, rosin acids, resin acids, and / or reaction products of long-chain carboxylic acids with alkanolamine and boric acid, and mixtures thereof.

5. The mould release agent as claimed in any of claims 1 - 3, characterized in that the corrosion inhibitor comprises or consists of a reaction product of a carboxylic acid or a mixture of carboxylic acids having an average of 16 - 26 C atoms, preferably 18 C atoms, with diethanolamine and boric acid.

6. The mould release agent as claimed in any of the previous claims, characterized in that the corrosion inhibitor is comprised in an amount of 0.5 - 15 w%, preferably 1 - 10 w%, more preferably 2 - 5 w%, relative to the total weight of the mould release agent.

7. A metal mould, preferably a steel mould, for casting of cementitious compositions, comprising at least one surface of the metal mould to be in contact with a cementitious composition which is treated with a mould release agent as claimed in any of claims 1 - 6.

8. A method for the casting of cementitious compositions comprising the steps of a) providing a metal mould, preferably a steel mould, b) applying a mould release agent comprising an oil and at least one corrosion inhibitor to at least one surface of the metal mould to be in contact with a cementitious composition, to prepare a treated metal mould, and c) casting a cementitious composition, preferably wet concrete, into the treated metal mould.

9. The method as claimed in claim 8, characterized in that the mould release agent is in the form of a continuous phase.

10. The method as claimed in any of claims 8-9, characterized in that the mould release agent comprises an oil selected from the group consisting of vegetable oils, methyl esters of fatty acids, synthetic oils, preferably paraffinic oils, especially API group III mineral oils, and mixtures thereof, and comprises a corrosion inhibitor selected from the group consisting of N-methyl-N-(1-oxo-9-octadecenyl)glycine, bis(C8-C10-alkyl)naphthalenesulphonate, isotridecyl phosphate, N,N-dimethylamide of tall-oil fatty acid, (tetrapropenyl)succinic acid, N-oleoylsarcosine, 2-(2-heptadec-8-enyl-2-imidazolin-1-yl)ethanol, rosin acids, resin acids, and / or reaction products of long-chain carboxylic acids with alkanolamine and boric acid, and mixtures thereof.

11. The method as claimed in any of claims 8 - 10, characterized in that the cementitious composition comprises a composite cement.

12. The method as claimed in claim 11, characterized in that the composite cement comprises between 5 - 94 w%, preferably 20 - 79 w%, more preferably 35 - 64 w% of Portland cement and between 6 - 95 w%, preferably 21 - 80 w%, more preferably 36 - 65 w% of at least one supplementary cementitious composition, in each case relative to the total dry weight of the composite cement.

13. The method as claimed in any of claims 11 - 12, characterized in that the composite cement comprises Portland cement and at least one supplementary cementitious composition selected from the group consisting of limestone, ground granulated blast furnace slag, basic oxygen furnace slag, silica fume, fly ash, burnt oil shale, natural pozzolane, calcined clay, and mixtures thereof.

14. The method as claimed in any of claims 8 - 13, additionally comprising a step of hardening the cast cementitious composition.

15. An element made of cementitious composition, especially a hardened concrete element, obtainable by a method as claimed in any of claims 8 - 14.

Images