USE OF A CEMENTITIOUS COMPOSITION AS A COATING FOR DISPOSABLE FOUNDRY CORES AND RELATIVE COATED CORE

Abstract

The use of a cementitious composition is described, as a coating for disposable foundry cores, said cementitious composition comprising at least one binder or hydraulic cement in a quantity ranging from 40% to 99.9% by weight with respect to the total weight of the cementitious composition; possibly one or more fillers in a quantity ranging from 0.1% to 60% by weight, with respect to the total weight of the cementitious composition, said filler preferably having a D99<100 m; at least one rheology modifying agent selected from cellulose, derivatives of cellulose such as methylhydroxyethylcellulose, vinyl acetate/versatate copolymers, polycarboxylate ether polymer, or a mixture thereof, in a quantity ranging from 0.1% to 5% by weight with respect to the total weight of the cementitious composition. A disposable foundry core is also described, having at least one coating layer based on said cementitious composition.

Claims

1. Use of a cementitious composition as a coating for disposable foundry cores, said cementitious composition comprising: at least one binder or hydraulic cement in a quantity ranging from 40% to 99.9% by weight, with respect to the total weight of the cementitious composition; optionally, one or more fillers in a quantity ranging from 0.1% to 60% by weight, with respect to the total weight of the cementitious composition; at least one rheology modifying agent selected from cellulose, derivatives of cellulose such as methylhydroxyethylcellulose, vinyl acetate/versatate copolymers, polycarboxylate ether polymer, or a mixture thereof, in a quantity ranging from 0.1% to 5% by weight, with respect to the total weight of the cementitious composition.

2. The use according to claim 1, wherein the binder or hydraulic cement is selected from Portland cement, sulfoaluminate cement and/or aluminous cement and/or rapid natural cement of the ciment prompt type, alone or mixed with each other and/or in a mixture with common cement, optionally containing additives or accelerated.

3. The use according to claim 1, wherein the binder or hydraulic cement is Portland cement type I with a strength class 42.5 or 52.5, with an ordinary (N) or high (R) initial strength class, according to the standard UNI EN 197-1:2011.

4. The use according to claim 1, wherein the binder or hydraulic cement is sulfoaluminate cement.

5. The use according to claim 1, wherein the filler is selected from the group consisting of limestone, siliceous and silico-calcareous fillers, including combinations thereof.

6. The use according to claim 1, wherein the rheology modifying agent is methylhydroxyethylcellulose.

7. The use according to claim 1, wherein the cementitious composition further comprises superfluidifying additives and/or other additives.

8. A disposable foundry core substantially consisting of sandy material and a core binder, characterized in that it is coated with one or more coating layers consisting of a cementitious composition comprising: at least one binder or hydraulic cement in a quantity ranging from 40% to 99.9% by weight, with respect to the total weight of the cementitious composition; optionally, one or more fillers in a quantity ranging from 0.1% to 60% by weight, with respect to the total weight of the cementitious composition; at least one rheology modifying agent selected from cellulose, derivatives of cellulose such as methylhydroxyethylcellulose, vinyl acetate/-versatate copolymers, polycarboxylate ether polymer, or a mixture thereof, in a quantity ranging from 0.1% to 5% by weight with respect to the total weight of the cementitious composition and water; said one or more coating layers having an overall thickness ranging from 0.15 mm to 1 mm.

9. (canceled)

10. The core according to claim 8, wherein the water/cementitious composition weight ratio ranges from 0.3 to 0.8.

11. The core according to claim 8, wherein the coating is applied to the core by brushing, airbrushing, by immersion in a coating bath, or by combinations thereof.

12. The use according to claim 1, wherein the binder or hydraulic cement is in a quantity ranging from 50% to 70% by weight, with respect to the total weight of the cementitious composition.

13. The use according to claim 1, wherein said one or more fillers are in a quantity ranging from 25% to 45% by weight, with respect to the total weight of the cementitious composition.

14. The use according to claim 1, wherein said one or more fillers have a D99<100 m.

15. The use according to claim 1, wherein said rheology modifying agent is in a quantity ranging from 0.1% to 3%, with respect to the total weight of the cementitious composition.

16. The use according to claim 1, wherein the binder or hydraulic cement is taken from the group consisting of CEM I 52.5R, CEM I 52.5N, sulfoaluminate cement, aluminous cement and combinations thereof.

17. The use according to claim 7, wherein the superfluidifying additives are acrylic-based polycarboxylates.

18. The use according to claim 7, wherein the further additives are taken from the group consisting of lignosulfonates, naphthalene sulfonates, melamine, vinyl compounds and combinations thereof.

19. The core according to claim 8, wherein the binder or hydraulic cement is in a quantity ranging from 50% to 70% by weight, with respect to the total weight of the cementitious composition.

20. The core according to claim 8, wherein said one or more fillers, when used, are in a quantity ranging from 25% to 45% by weight, with respect to the total weight of the cementitious composition.

21. The core according to claim 8, wherein said one or more fillers, when used, have a D99<100 m.

22. The core according to claim 8, wherein said rheology modifying agent is in a quantity ranging from 0.1% to 3%, with respect to the total weight of the cementitious composition.

Description

EXAMPLE 1

[0080] Various tests were carried out, applying the formulation of the cementitious composition indicated in Table 1, mixed with water in the following weight ratios:

[0081] 1 part of cementitious composition, 0.55 parts of water.

[0082] The coating was applied on an inorganic core produced according to the CORDIS method as previously described, applying said coating either by brushing or by spraying with an airbrush.

[0083] These cores are destined for the production of aluminium end-products produced with the jet technology at both low pressure at 1.2 bar and by casting at atmospheric pressure.

[0084] Test Nr.1.1a

[0085] Low-pressure aluminium jet at 1.2 bar, using non-coated inorganic cores and coated inorganic cores according to Example 1.

[0086] Type of piece: parts of car chassis

[0087] Application: Brush

[0088] Application thickness: 400 m50 m (one layer)

[0089] Pieces obtained using non-coated cores: 2

[0090] Pieces obtained using coated cores: 2

[0091] Curing period: 7 days

[0092] Test Result

[0093] Pieces obtained using non-coated cores: [0094] unsatisfactory finish due to the penetration of molten aluminium into the inorganic core; [0095] weight of the piece 30% higher with respect to the project weight due to the aluminium penetrated into the core; the excess metal causes a cost increase and a degradation in the performances, as the weight is a production specification.

[0096] Pieces obtained using coated cores: [0097] satisfactory finish, indicating an adequate impermeability of the inorganic core to molten aluminium; [0098] weight of the piece equal to the project weight with consequent compliance in terms of cost and performances.

[0099] Test Nr.1.1b

[0100] Low-pressure aluminium jet at 1.2 bar, using non-coated inorganic cores and coated inorganic cores according to Example 1.

[0101] Type of piece: parts of car chassis

[0102] Application: Airbrush (nozzle diameter: 1.9 mm, air pressure: 5 bar)

[0103] Application thickness: 300 m50 m (4 layers)

[0104] Pieces obtained using non-coated cores: 4

[0105] Pieces obtained using coated cores: 4

[0106] Curing period: 2 days

[0107] Test Result

[0108] Pieces obtained using non-coated cores: [0109] unsatisfactory finish due to the penetration of molten aluminium into the inorganic core; [0110] weight of the piece 30% higher with respect to the project weight due to the aluminium penetrated into the core; the excess metal causes a cost increase and a degradation in the performances, as the weight is a production specification.

[0111] Pieces obtained using coated cores: [0112] satisfactory finish, indicating an adequate impermeability of the inorganic core to molten aluminium; [0113] weight of the piece equal to the project weight with consequent compliance in terms of cost and performances.

[0114] Test Nr.1.2a

[0115] Aluminium jet by casting at atmospheric pressure, using non-coated inorganic cores and coated inorganic cores according to Example 1.

[0116] Type of piece: brake calipers

[0117] Application: Brush

[0118] Application thickness: 410 m50 m (one layer)

[0119] Pieces obtained using non-coated cores: 3

[0120] Pieces obtained using coated cores: 3

[0121] Curing period: 7 days

[0122] Test Result

[0123] Pieces obtained using non-coated cores: [0124] satisfactory finish, difficulty in handling and storing the cores due to the tendency of losing mechanical strength following moisture absorption.

[0125] Pieces obtained using coated cores: [0126] satisfactory finish, better handling and longer storage possibilities due to protection against environmental moisture offered by the coating.

[0127] Test Nr.1.2b

[0128] Aluminium jet by casting at atmospheric pressure, using non-coated inorganic cores and coated inorganic cores according to Example 1.

[0129] Type of piece: brake calipers

[0130] Application: Airbrush (nozzle diameter: 1.9 mm, air pressure: 5 bar)

[0131] Application thickness: 200 m50 m (two layers)

[0132] Pieces obtained using non-coated cores: 3

[0133] Pieces obtained using coated cores: 3

[0134] Curing period: 2 days

[0135] Test Result

[0136] Pieces obtained using non-coated cores: [0137] unsatisfactory finish;

[0138] Pieces obtained using coated cores: [0139] satisfactory finish.

[0140] Test Nr.1.2c

[0141] Aluminium jet by casting at atmospheric pressure, using non-coated inorganic cores and coated inorganic cores according to Example 1.

[0142] Type of piece: brake calipers

[0143] Application: Airbrush (nozzle diameter: 1.9 mm, air pressure: 5 bar)

[0144] Application thickness: 290 m50 m (four layers)

[0145] Pieces obtained using non-coated cores: 3

[0146] Pieces obtained using coated cores: 3

[0147] Curing period: 2 days

[0148] Test Result

[0149] Pieces obtained using non-coated cores: [0150] unsatisfactory finish;

[0151] Pieces obtained using coated cores: [0152] satisfactory finish.

EXAMPLE 2

[0153] Various tests were carried out, applying the formulation of the cementitious composition indicated in Table 2, mixed with water in the following weight ratios:

[0154] 1 part of cementitious composition, 0.65 parts of water.

[0155] The coating was applied on an inorganic core produced according to the CORDIS method as previously described, applying said coating by brushing.

[0156] These cores are destined for the production of aluminium end-products produced with the jet technology by casting at atmospheric pressure.

[0157] Test Nr.2.1

[0158] Aluminium jet by casting at atmospheric pressure, using non-coated inorganic cores and coated inorganic cores, as previously described.

[0159] Type of piece: engine bases

[0160] Application: Brush

[0161] Pieces obtained using non-coated cores: 20

[0162] Pieces obtained using coated cores: 20

[0163] Application thickness: 350 m50 m (one layer)

[0164] Curing period: [0165] Lot 1: 7 days [0166] Lot 2: 30 days

[0167] Test Result

[0168] Pieces obtained using non-coated cores: [0169] unsatisfactory finish due to a moderate penetration of molten aluminium into the inorganic core; [0170] weight of the piece 20% higher with respect to the project weight due to the aluminium penetrated in the core.

[0171] Pieces obtained using coated cores: [0172] satisfactory finish, indicating an adequate impermeability of the inorganic core of the CORDIS type to molten aluminium; [0173] weight of the piece equal to the project weight.

[0174] Characterization tests were carried out on the product to evaluate the effective capacity of not transferring water to the substrate. This feature is important as an excess supply of water to the substrate can cause a degradation of the performances. This property was assessed by measuring the water retention in compliance with the standard UNI EN 459-2:2010 (Building limesTest methods).

[0175] The results are indicated in Table 4 below.

TABLE-US-00004 TABLE 4 Examples Product Water retention 1 Composition of Table 1 96.25% 2 Composition of Table 2 96.15% Reference/comparison Interior pain 87.00%

[0176] The reference/comparison consists of an interior paint which is an acrylic-based breathable paint for plasters having the trade-name Sistema Colore, sold by Fassa Bortolo.

[0177] As is known, cementitious materials require prolonged curing times after the jet to allow the development of hydration reactions and enable them to be put into operation. The drying and curing times of the product were evaluated and the results are indicated in Table 5.

TABLE-US-00005 TABLE 5 Time necessary for Application handling the coated cores Application: Airbrush 15 minutes Application thickness: 200 m (two layers) Application: Airbrush 45 minutes Application thickness: 300 m (four layers)

[0178] The time necessary for handling the coated cores is a parameter having an important impact on the productivity of the melting process. In both of the examples of Table 5, the value measured is compatible with normal foundry processes; this time can also be regulated in relation to the layers of application of the coating. A time in the order of an hour is not industrially acceptable.