UNSATURATED POLYESTER RESIN FOR ENGINEERED STONE COMPRISING FINE AND/OR POROUS PARTICLES

Abstract

The invention relates to an unsaturated polyester resin of low molecular weight which is useful for the preparation of engineered stone. When mixing the unsaturated polyester resin with a fine inorganic particulate material such as cristobalite, a formable composition is obtained that can be further processed and cured to finally yield engineered stone as composite material. The invention also relates to a method for the preparation of engineered stone as well as to the use of the unsaturated polyester resin for the preparation of engineered stone.

Claims

1. An unsaturated polyester resin component for the preparation of engineered stone, wherein the unsaturated polyester resin component has a weight average molecular weight of not more than about 2500 g/mol and is obtained by reacting a mixture comprising (i) a polycarboxylic acid component comprising at least 2 polycarboxylic acids wherein a first carboxylic acid is selected from the group consisting of unsaturated aliphatic polycarboxylic acids, anhydrides or esters thereof and a second polycarboxylic acid is selected from the group consisting of saturated aliphatic polycarboxylic acids, anhydrides or esters thereof; (ii) a polyfunctional alcohol component comprising at least one polyfunctional alcohol selected from the group consisting of saturated aliphatic polyfunctional alcohols and unsaturated aliphatic polyfunctional alcohols; (iii) optionally, a monocarboxylic acid component comprising at least one monocarboxylic acid selected from aromatic monocarboxylic acids, anhydrides or esters thereof; saturated aliphatic monocarboxylic acids, anhydrides or esters thereof; and unsaturated aliphatic monocarboxylic acids, anhydrides or esters thereof; and (iv) optionally, a monofunctional alcohol component comprising at least one monofunctional alcohol selected from aromatic monofunctional alcohols, saturated aliphatic monofunctional alcohols, and unsaturated aliphatic monofunctional alcohols; wherein the polycarboxylic acid component and/or the polyfunctional alcohol component and/or the monocarboxylic acid component and/or the monofunctional alcohol component comprises ethylenic unsaturation.

2. The unsaturated polyester resin component according to claim 1, wherein (i) the polycarboxylic acid component comprises fumaric acid and adipic acid; and (ii) the polyfunctional alcohol component comprises propylene glycol and diethylene glycol.

3. The unsaturated polyester resin component according to claim 1 or 2, which has a weight average molecular weight of not more than about 2000 g/mol; preferably not more than about 1500 g/mol; and/or a viscosity in the range of about 150 to about 400 mPas.

4. The unsaturated polyester resin component according to any of the preceding claims, wherein the molar content of the second polycarboxylic acid which is selected from the group consisting of saturated aliphatic polycarboxylic acids, anhydrides is not more than 13.5 mole.-% relative to the molar content of the polycarboxylic acid component.

5. The unsaturated polyester resin component according to any of the preceding claims, wherein the molar ratio of (saturated aliphatic polycarboxylic acids, anhydrides or esters thereof) to (unsaturated aliphatic polycarboxylic acids, anhydrides or esters thereof) in the polyester resin component is in the range of (0.5 to 1.5):(6.5-8.5).

6. The unsaturated polyester resin component according to any of the preceding claims, which has a viscosity in the range of about 400 to about 500 mPas at 100 C., preferably in the range of about 400 to about 450 mPas at 100 C.

7. The unsaturated polyester resin component according to any of the preceding claims, wherein the polycarboxylic acid component, preferably the unsaturated polyester resin component, does not comprise maleic acid or maleic acid anhydride.

8. The unsaturated polyester resin component according to any of the preceding claims, wherein (i) the polycarboxylic acid component comprises a mixture of an aromatic polycarboxylic acid, anhydride or ester thereof; with a saturated aliphatic polycarboxylic acid, anhydride or ester thereof; and with an unsaturated aliphatic polycarboxylic acid, anhydride or ester thereof; and/or (ii) the polyfunctional alcohol component comprises a mixture of at least two saturated aliphatic polyfunctional alcohols.

9. The unsaturated polyester resin component according to any of the preceding claims, wherein (i) the weight content of the polycarboxylic acid component is within the range of about 5531 wt.-%; and/or (ii) the weight content of the polyfunctional alcohol component is within the range of about 3521 wt.-%; in each case relative to the total weight of the polycarboxylic acid component, the polyfunctional alcohol component, the optionally present monocarboxylic acid component, and the optionally present monofunctional alcohol component.

10. The unsaturated polyester resin component according to any of the preceding claims, wherein (i) the weight content of the polycarboxylic acid component is within the range of about 555 wt.-%; and/or (ii) the weight content of the polyfunctional alcohol component is within the range of about 356 wt.-%; in each case relative to the total weight of the polycarboxylic acid component, the polyfunctional alcohol component, the optionally present monocarboxylic acid component, and the optionally present monofunctional alcohol component.

11. The unsaturated polyester resin component according to any of the preceding claims, wherein (i) the polycarboxylic acid component comprises a mixture of at least one aromatic dicarboxylic acid, anhydride or ester thereof; with at least one saturated aliphatic dicarboxylic acid, anhydride or ester thereof; and with at least one unsaturated aliphatic dicarboxylic acid, anhydride or ester thereof; and/or (ii) the polyfunctional alcohol component comprises a mixture of at least two saturated aliphatic diols.

12. The unsaturated polyester resin component according to claim 11, wherein the molar content of the at least one aromatic dicarboxylic acid, anhydride or ester thereof is within the range of about 2523 mole.-%, based on all aromatic dicarboxylic acids, anhydrides or esters thereof; and/or the molar content of the at least one saturated aliphatic dicarboxylic acid, anhydride or ester thereof is within the range of; and about 12.510.5 mole.-%, based on all saturated aliphatic dicarboxylic acids, anhydrides or esters thereof; and/or the molar content of the at least one unsaturated aliphatic dicarboxylic acid, anhydride or ester thereof is within the range of about 6531 mole.-%, based on all saturated aliphatic dicarboxylic acids, anhydrides or esters thereof; in each case relative to the total molar content of (i) the polycarboxylic acid component.

13. The unsaturated polyester resin component according to claim 11, wherein the molar content of the at least one aromatic dicarboxylic acid, anhydride or ester thereof is within the range of about 253 mole.-%, based on all aromatic dicarboxylic acids, anhydrides or esters thereof; and/or the molar content of the at least one saturated aliphatic dicarboxylic acid, anhydride or ester thereof is within the range of; and about 12.51.5 mole.-%, based on all saturated aliphatic dicarboxylic acids, anhydrides or esters thereof; and/or the molar content of the at least one unsaturated aliphatic dicarboxylic acid, anhydride or ester thereof is within the range of about 655 mole.-%, based on all saturated aliphatic dicarboxylic acids, anhydrides or esters thereof; in each case relative to the total molar content of (i) the polycarboxylic acid component.

14. The unsaturated polyester resin component according to any of claims 11 to 13, wherein the at least one aromatic dicarboxylic acid, anhydride or ester thereof is selected from isophthalic acid, phthalic acid, and the anhydrides thereof; and/or the at least one saturated aliphatic dicarboxylic acid, anhydride or ester thereof is adipic acid or adipic acid anhydride; and/or the at least one unsaturated aliphatic dicarboxylic acid, anhydride or ester thereof is selected from maleic acid, fumaric acid and the anhydrides thereof; and/or the at least two saturated aliphatic diols are selected from the group consisting of propylene glycol, dipropylene glycol, ethylene glycol, and diethylene glycol.

15. The unsaturated polyester resin component according to any of claims 11 to 13, wherein the at least one aromatic dicarboxylic acid, anhydride or ester thereof is selected from isophthalic acid, phthalic acid, and the anhydrides thereof; and/or the at least one saturated aliphatic dicarboxylic acid, anhydride or ester thereof is adipic acid or adipic acid anhydride; and/or the at least one unsaturated aliphatic dicarboxylic acid, anhydride or ester thereof is fumaric acid and the anhydrides thereof; and/or the at least two saturated aliphatic diols are propylene glycol and diethylene glycol.

16. The unsaturated polyester resin component according to claim 14 or 15, wherein the molar ratio of (adipic acid or adipic acid anhydride) to (phthalic acid or phthalic acid anhydride) in the polyester resin component is in the range of (0.5 to 3):(1.5 to 3).

17. The unsaturated polyester resin component according to any of the preceding claims, which comprises (iv) a monofunctional alcohol component comprising at least one monofunctional alcohol selected from aromatic monofunctional alcohols, saturated aliphatic monofunctional alcohols, and unsaturated aliphatic monofunctional alcohols.

18. The unsaturated polyester resin component according claim 17, wherein the weight content of the monofunctional alcohol component is within the range of about 7.06.5 wt.-%, relative to the total weight of the polycarboxylic acid component, the polyfunctional alcohol component, the optionally present monocarboxylic acid component, and the optionally present monofunctional alcohol component.

19. The unsaturated polyester resin component according claim 17, wherein the weight content of the monofunctional alcohol component is within the range of about 7.02.0 wt.-%, relative to the total weight of the polycarboxylic acid component, the polyfunctional alcohol component, the optionally present monocarboxylic acid component, and the optionally present monofunctional alcohol component.

20. The unsaturated polyester resin component according to any of claims 17 to 19, wherein the monofunctional alcohol component comprises benzyl alcohol.

21. The unsaturated polyester resin component according to any of claims 17 to 20, wherein the molar content of the at least two saturated aliphatic diols is within the range of about 8811 mole.-%, based on all saturated aliphatic diols; and/or the molar content of the at least one monofunctional alcohol is within the range of about 1211 mole.-%, based on all monofunctional alcohols; in each case relative to the total molar content of (ii) the polyfunctional alcohol component and (iv) the monofunctional alcohol component.

22. The unsaturated polyester resin component according to any of claims 17 to 20, wherein the molar content of the at least two saturated aliphatic diols is within the range of about 882 mole.-%; based on all saturated aliphatic diols; and/or the molar content of the at least one monofunctional alcohol is within the range of about 122 mole.-%; based on all monofunctional alcohols; in each case relative to the total molar content of (ii) the polyfunctional alcohol component and (iv) the monofunctional alcohol component.

23. A prepromoted unsaturated polyester resin system for the preparation of engineered stone, which system comprises (i) a unsaturated polyester resin component according to any of claims 1 to 22; (ii) a metal catalyst capable of catalyzing curing of said unsaturated polyester resin component; (iii) a quaternary ammonium salt; and (iv) optionally, one or more additives selected from the group consisting of reactive diluents, accelerators, co-promoters, dispersing agents, UV absorbers, stabilizers, inhibitors and rheology modifiers.

24. The prepromoted unsaturated polyester resin system according to claim 23, wherein the metal catalyst comprises zinc or copper.

25. The prepromoted unsaturated polyester resin system according to claim 23 or 24, which is cobalt free.

26. The prepromoted unsaturated polyester resin system according to any of claims 23 to 25, wherein the quaternary ammonium salt is a benzyl-N,N,N-trialkylammonium salt or a N,N,N,N-tetraalkylammonium salt.

27. The prepromoted unsaturated polyester resin system according to any of claims 23 to 26, which comprises a reactive diluent selected from the group consisting of styrene, substituted styrene, mono-, di- and polyfunctional esters of monofunctional acids with alcohols or polyfunctional alcohols, mono-, di- and polyfunctional esters of unsaturated monofunctional alcohols with carboxylic acids or their derivatives.

28. The prepromoted unsaturated polyester resin system according to claim 27, wherein the reactive diluent comprises styrene.

29. The prepromoted unsaturated polyester resin system according to any of claims 23 to 28, wherein the content of reactive diluent is within the range of about 308 wt.-%, more preferably about 302 wt.-%, relative to the total weight of the prepromoted unsaturated polyester resin system.

30. A formable composition for the preparation of engineered stone comprising (A) a prepromoted unsaturated polyester resin system according to any of claims 23 to 29; (B) an inorganic particulate material; and (C) a peroxide component.

31. The formable composition according to claim 30, wherein the inorganic particulate material comprises silicon dioxide.

32. The formable composition according to claim 31, wherein the silicon dioxide is present as quartz and/or cristobalite.

33. The formable composition according to any of claims 30 to 32, wherein the silicon dioxide has an average particle size of not more than about 0.25 m.

34. The formable composition according to any of claims 30 to 33, wherein the peroxide component is selected from the group consisting of is cumene hydroperoxide, methyl isobutyl ketone and peroxide and tert-butyl peroxibenzoate.

35. The formable composition according to claim 34, wherein the peroxide component is tert-butyl peroxibenzoate.

36. The formable composition according to any of claims 30 to 35, which is cobalt free.

37. The formable composition according to any of claims 30 to 37, wherein the weight content of the prepromoted unsaturated polyester resin system is about 0.1 wt.-% to about 30 wt.-%, relative to the total weight of the formable composition; and/or wherein the weight content of the inorganic particulate material is about 70 wt.-% to about 99.9 wt.-%, relative to the total weight of the formable composition.

38. The formable composition according to any of claims 30 to 37, wherein the weight content of the inorganic particulate material is within the range of about 905 wt.-%, relative to the total weight of the formable composition.

39. The formable composition according to any of claims 30 to 38, wherein the weight content of the prepromoted unsaturated polyester resin system is not more than about 15 wt.-%, relative to the total weight of the formable composition.

40. The formable composition according to any of claims 30 to 38, wherein the weight content of the prepromoted unsaturated polyester resin system is not more than about 12.5 wt.-%, relative to the total weight of the formable composition.

41. A method for the preparation of a unsaturated polyester resin component according to any of claims 1 to 22 comprising the step of reacting a mixture comprising (i) a polycarboxylic acid component; (ii) a polyfunctional alcohol component; (iii) optionally, a monocarboxylic acid component; and (iv) optionally, a monofunctional alcohol component; wherein the polycarboxylic acid component and/or the polyfunctional alcohol component and/or the monocarboxylic acid component and/or the monofunctional alcohol component comprises ethylenic unsaturation.

42. A method for the preparation of a prepromoted unsaturated polyester resin system according to any of claims 23 to 29 comprising the step of mixing (i) a unsaturated polyester resin component according to any of claims 1 to 22; (ii) a metal catalyst capable of catalyzing curing of said unsaturated polyester resin component; (iii) a quaternary ammonium salt; and (iv) optionally, one or more additives selected from the group consisting of reactive diluents, accelerators, co-promoters, dispersing agents, UV absorbers, stabilizers, inhibitors and rheology modifiers.

43. A method for the preparation of a formable composition for the preparation of engineered stone according to any of claims 30 to 40 comprising the step of mixing (A) a prepromoted unsaturated polyester resin system according to any of claims 23 to 29; (B) an inorganic particulate material; and (C) a peroxide component.

44. A method for the preparation of engineered stone comprising the steps of (a) providing a formable composition according to any of claims 30 to 40; (b) forming the composition prepared in step (a) into a desired shape; and (c) allowing the composition formed in step (b) to cure.

45. Engineered stone obtainable by the method according to claim 44.

46. The engineered stone according to claim 45, which has a flexural strength within the range of about 10510 MPa.

47. The engineered stone according to claim 45 or 46, which has an impact resistance within the range of about 113.0 J/m.

48. Use of a unsaturated polyester resin component according to any of claims 1 to 22 for the preparation of engineered stone.

49. Use of a prepromoted unsaturated polyester resin system according to any of claims 23 to 29 for the preparation of engineered stone.

50. Use of a formable composition according to any of claims 30 to 40 for the preparation of engineered stone.

Description

EXAMPLE 1

[0209] An unsaturated polyester resin was prepared from the following monomers and subsequently mixed with styrene (reactive diluent):

TABLE-US-00004 parts per weight comparative inventive monopropylene glycol 26 28 diethylene glycol 0 3 benzyl alcohol 0 6 adipic acid 0 6.7 phthalic acid anhydride 31 15 maleic acid 11 0 fumaric acid 0 28 styrene 37 22 weight average M.sub.w [g/mole] 2000

[0210] The preparation of the unsaturated polyester resin component comprised the steps of [0211] (a) mixing and heating the monopropylene glycol (PG), diethylene glycol (DEG), adipic acid (AA), phthalic anhydride (PAN), and potassium acetate; and [0212] (b) adding benzyl alcohol, fumaric acid and an inhibitor to the mixture obtained in step (a).

[0213] Stone slabs (thickness 2 cm) having the following composition were manufactured from the comparative and the inventive unsaturated polyester resin:

TABLE-US-00005 comparative inventive Resin % 14 12 Cristobalite filler 45 micron % 28 30 Cristobalite filler 45 micron % 58 58

[0214] The mechanical properties of the obtained stone slabs were investigated and the results are summarized in the table here below:

TABLE-US-00006 comparative inventive Flexural strength [MPa] 60 105 Bending yes no Impact resistance [J/m] 6 11

[0215] It becomes clear from the above comparative data that the unsaturated polyester resin according to the invention provides engineered stone having superior properties compared to engineered stone manufactured from conventional unsaturated polyester resins.

EXAMPLE 2 (COMPARATIVE) AND EXAMPLE 3 (COMPARATIVE)

[0216] Two unsaturated polyester resin were prepared from the following monomers:

TABLE-US-00007 example 2 example 3 (comparative) (comparative) component [g] [mol] [g] [mol] propylene glycol 400.00 5.26 390.10 5.13 diethylene glycol 39.00 0.37 40.28 0.38 inhibitor solution 25% HQ 0.06 phosphoric acid 0.05 phthalic anhydride 474.00 3.20 229.64 1.55 benzyl alcohol 81.47 0.75 maleic acid anhydride 177.00 1.81 350.74 3.58 inhibitor solution 25% HQ 0.06 0.132 Total 1090.17 10.64 1092.35 11.40 Distillate 90.17 92.35 Plastic 1000.00 1092.35

[0217] Synthesis of resin example 2 (comparative): propylene glycol, diethylene glycol, hydroquinone solution, phosphoric acid, phthalic anhydride and maleic anhydride were charged to a reactor equipped with a thermocouple, a mechanical stirrer, a fractionating column, a distillation head, a condenser and nitrogen sparge. Agitation was started as soon as a sufficient quantity of material was in the reactor. The reactor was sparged with nitrogen and heated to a temperature of 2055 C., while maintaining the column top temperature at 1002 C. Sampling for acid number and Brookfield CAP viscosity (first at 125 C. and later at 150 C., cone#3) was started as soon as a reactor temperature of greater than 2005 C. was reached. When the acid number was 85-100 vacuum was applied and increased gradually. The reaction mixture was heated at 2055 C. under vacuum until Brookfield CAP viscosity (at 150 C., cone#3) of 2.2-2.6 P and an acid number of 30-40 mgKOH/g (100% solids) were reached. Then the vacuum was released and the reaction mixture was cooled to a temperature of 190-200 C. and the rest of hydroquinone solution added.

[0218] Synthesis of resin example 3 (comparative): propylene glycol, diethylene glycol, phthalic anhydride, benzyl alcohol, maleic anhydride and hydroquinone solution were charged to a reactor equipped with a thermocouple, a mechanical stirrer, a fractionating column, a distillation head, a condenser and nitrogen sparge. Agitation was started as soon as a sufficient quantity of material was in the reactor. The reactor was sparged with nitrogen and heated to a temperature of 205-210 C., while maintaining the column top temperature at 1002 C. Sampling for acid number and Brookfield CAP viscosity (at 100 C., cone#3) was started as soon as reactor reached top temperature. When the acid number was 60-65 vacuum was applied and increased gradually. The reaction mixture was heated at 205-210 C. under vacuum until Brookfield CAP viscosity (at 100 C., cone#3) of 4.5-5.0 P and an acid number of 41-45 mgKOH/g (100% solids) were reached. Then the vacuum was released and the reaction mixture was cooled to a temperature of 1855 C.

[0219] The thus obtained comparative resins had the following properties:

TABLE-US-00008 Molecular weight example 2 example 3 and viscosity data: (comparative) (comparative) Mn [g/mol] 1563 1023 Mw [g/mol] 2726 1705 Mp [g/mol] 2306 1278 Pdi 1.74 1.67 Viscosity (mPas) 220-260 @ 150 C. 450-500 @ 100 C. AV 30-40 41-45

[0220] After synthesis the comparative resins were mixed with styrene (reactive diluent) and other additives:

TABLE-US-00009 example 2 example 3 (comparative) (comparative) component [g] wt.-% [g] wt.-% styrene 519.92 34 450.00 29 copper naphthenate 8% 0.05 in styrene hydroquinone 25% 0.18 0.30 in PGMME solution further additives 2.30 sum additives 522.45 450.30

[0221] Dilution of resin example 2 (comparative): resin was dropped slowly to a thin tank, which was charged beforehand with styrene (519.92 g), copper naphthenate 8% in styrene solution (0.05 g), and hydroquinone 25% in propylene glycol monomethyl ether (PGMME) solution (0.18 g). During drop, thin tank temperature was maintained at maximum 855 C. Mixing and cooling of the thin tank was continued until temperature was decreased below 40 C. The final resin was adjusted with additional additives.

[0222] Dilution of resin example 3 (comparative): resin was dropped slowly to a thin tank, which was charged beforehand with styrene (450 g), and hydroquinone 25% in propylene glycol monomethyl ether (PGMME) solution (0.3 g). During drop, thin tank temperature was maintained at maximum 805 C. Mixing and cooling of the thin tank was continued until temperature was decreased below 40 C. The final resin was adjusted with additional additives.

EXAMPLE 4 (INVENTIVE)

[0223] An unsaturated polyester resin was prepared from the following monomers:

TABLE-US-00010 inventive example 4 component g mol wt.-% mol.-% propylene glycol 384.59 5.06 33.10 44.75 diethylene glycol 38.24 0.36 3.29 3.19 phthalic anhydride 198.66 1.34 17.10 11.87 adipic acid 90.03 0.62 7.75 5.45 potassium acetate 0.05 benzyl alcohol 77.94 0.72 6.71 6.38 maleic acid anhydride fumaric acid 371.87 3.21 32.01 28.35 inhibitor solution 0.39 25% HQ Total 1161.77 11.31 Distillate 161.77 Plastic 1000.00

[0224] The unsaturated polyester resin of example 4 was prepared in two steps. The first step comprised the reaction of the following monomers:

TABLE-US-00011 component [g] [mol] propylene glycol 384.59 5.06 diethylene glycol 38.24 0.36 phthalic anhydride 198.66 1.34 adipic acid 90.03 0.62 potassium acetate 0.05

[0225] Propylene glycol, diethylene glycol, phthalic anhydride, adipic acid and potassium acetate were charged to a reactor equipped with a thermocouple, a mechanical stirrer, a fractionating column, a distillation head, a condenser and nitrogen sparge. Agitation was started as soon as a sufficient quantity of material was in the reactor. The reactor was sparged with nitrogen and slowly heated to a temperature of 205-210 C. First water distillate/exotherm was observed at a reaction temperature of 165-175 C. and the temperature of the water distillate at the column top was maintained at 1002 C. As soon as exotherm was subsided the reaction temperature was further increased until the acid number of the product was about 75-85 (100% solids) and the reactor temperature was greater than 180 C. The reaction mixture was cooled to 150-170 C.

[0226] The second step comprised the reaction of the following components:

TABLE-US-00012 component [g] [mol] benzyl alcohol 77.94 0.72 fumaric acid 371.87 3.21 hydroquinone 25% in PGMME solution 0.39

[0227] Benzyl alcohol, fumaric acid and hydroquinone 25% in propylene glycol monomethyl ether (PGMME) solution were added to the reactor containing the reaction product of step 1. The reaction mixture was heated to a temperature of 205-210 C. as fast as possible, while maintaining the column top temperature at 1002 C. Sampling for acid number and Brookfield CAP viscosity (at 100 C., cone#3 or #4) was started as soon as a reactor temperature of greater than 180 C. was reached. When the acid number was smaller 70 and/or the column top temperature dropped below 80 C., vacuum was applied and increased gradually. The reaction mixture was heated at 205-210 C. under vacuum until Brookfield CAP viscosity (at 100 C., cone#3 or #4) of 4,0-4,5 P and an acid number of 27-37 mgKOH/g (100% solids) were reached. Then the vacuum was released and the reaction mixture was cooled to a temperature of 1805 C.

[0228] The thus obtained inventive polyester resins had the following properties:

TABLE-US-00013 Molecular weight and viscosity inventive data example 4 Mn [g/mol] 1047 Mw [g/mol] 2000 Mp [g/mol] 1663 Pdi 1.91 Viscosity (mPas) @ 100 C. 400-450 AV 27-37

[0229] After synthesis the inventive polyester resins were mixed with styrene (reactive diluent) and other additives:

TABLE-US-00014 inventive example 5 component [g] wt.-% styrene 423.00 29 hydroquinone 25% in PGMME solution 0.10 further additives 15.22 sum additives 438.32

[0230] The thus obtained resin was diluted in styrene. The resin was dropped slowly to a thin tank, which was charged beforehand with styrene (423 g, 10.46 mol) and hydroquinone 25% in propylene glycol monomethyl ether (PGMME) solution (0,098 g). During drop, thin tank temperature was maintained at maximum 805 C. Mixing and cooling of the thin tank was continued until temperature was decreased below 35 C. The final resin was adjusted with additional additives.

EXAMPLES 5 TO 9 (COMPARATIVE), AND EXAMPLES 10 TO 13 (INVENTIVE)

[0231] Stone slabs were manufactured from the comparative polyester resins of examples 2 and 3 and the inventive unsaturated polyester resin of example 4. The mechanical properties of the obtained stone slabs were investigated. The compositions of the stone slabs and the mechanical properties of the stone slabs are summarized in the table here below:

TABLE-US-00015 Example comp. 5 comp. 6 comp. 7 comp. 8 comp. 9 inv. 10 inv. 11 inv. 12 inv. 13 Resin of example 2 (comp.) of example 3 (comp.) of example 4 (inv.) Molecular weight 2726 g/mol 1705 g/mol 2000 g/mol Resin [wt.-%] 10 12 14 10 12 10 12 14 12 Cristobalite Filler 30 30 30 30 30 30 45 microns [wt.-%] 0.1-0.4 Cristobalite 58 56 58 56 58 [wt.-%] Quartz Filler 30 30 30 45 Microns [wt.-%] 0.1-0.3 Quartz [wt.-%] 35 35 35 58 0.3-0.6 Quartz [wt.-%] 25 25 25 SUM 100 100 100 100 100 100 100 100 100 TiO.sub.2 on resin [wt.-%] 10 10 10 10 10 10 10 10 10 Cobalt (6%) on resin 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 0.20 [wt.-%] TBPB on Resin [wt.-%] 2 2 2 2 2 2 2 2 2 Memo silane on resin 2 2 2 2 2 2 2 2 2 [wt.-%] Slab prepared from comp. 5 comp. 6 comp. 7 inv. 8 inv. 9 inv. 10 inv. 11 inv. 12 inv. 13 Slab thicknes [cm] 2 2 2 2 2 2 2 2 2 Flexural Strength [MPa] 65 60 75 55 65 70 95 100 105 Wetting good dry/mass good bad, good bad, good good good not uniform too wet too wet Bending no no yes yes no no no some no Cracks no no no yes yes yes no some no Impact Resistance [J/m] 5 5 5 3 4 6 9.5 9 11 UV after 1000 h QUV A 7.9 8 8.2 7 6.8 7 6.8 db

[0232] The following table shows the common industrial standard for mechanical properties of engineered stone slabs:

TABLE-US-00016 industrial standard slab thickness [cm] 2 Flexural Strength [MPa] >45 wetting good Bending no cracks no Impact Resistance [J/m] >4 UV after 1000 h QUV A db <10 slab thickness [cm]

[0233] Accelerated weathering (QUV) simulates damaging effects of long term outdoor exposure of materials. The test was carried out according to ASTM method G 154 (QUV A). Stone slabs were exposed to varying conditions: ultraviolet radiation, moisture and heat. In the test, UV radiation (UV cycle: 8 h 60 C.) and water vapor (condensation cycle: 4 h 50 C.) conditions are alternated. Overall exposure time was 1000 h. The degree of color change due to weathering and UV-exposure is measured with the value db. The value db is related to yellowing of the stone slabs, wherein an increase of the db-value or a positive db-value indicates that the change is to a more (darker) yellow color of the artificial stone slabs and a decrease of the db-value or a negative db-value indicates a change to a more blue color of the artificial stone slabs.

[0234] The experimental data shows that the unsaturated polyester resin according to the invention provides engineered stone having superior properties compared to engineered stone manufactured from conventional unsaturated polyester resins with respect to changes in color. Whereas the stone slabs manufactured from conventional unsaturated polyester resins had db-values around 8 the slabs prepared from the inventive polyester resin had db-values around 7, i.e. showed less yellowing.

[0235] The above comparative data illustrates that the unsaturated polyester resin according to the invention provides engineered stone having superior properties compared to engineered stone manufactured from conventional unsaturated polyester resins. The engineered stone slabs prepared from the inventive unsaturated polyester resins showed improved mechanical properties compared to stone slabs prepared from unsaturated polyester resin having a molecular weight of more than about 2500 g/mol.

[0236] The experimental data illustrates that resins comprising fumaric acid and a saturated polycarboxylic acid such as adipic acid show improved mechanical properties. The resins employed in the manufacture of the stone slabs of comparative examples 5 to 9 did not comprise fumaric acid or a saturated polycarboxylic acid. The stone slabs prepared therefrom showed a flexural strength of up to 75 MPa and an impact resistance of up to 5 J/m. The resins employed in inventive examples 10 to 13 comprised fumaric acid and a saturated polycarboxylic acid. In contrast thereto, the stone slabs prepared from the inventive resins showed a flexural strength of up to 105 MPa and an impact resistance of up to 11 J/m.

[0237] Further, the stone slabs of comparative examples 8 and 9 had cracks. Said stone slabs were prepared from resins comprising a rather high content of maleic acid anhydride and a rather low content of diethylene glycol. Without wishing to be bound to any scientific theory, the cracks in the engineered stone slabs may be caused by the reactivity of the reactive double bonds of the maleic acid anhydride and also by the low content of diethylene glycol.

[0238] Further, the experimental data illustrates that the inventive unsaturated polyester resins show improved properties when employed with cristobalite fillers in the manufacture of engineered stone slabs compared to conventional resins which show poor properties when employed with cristobalite fillers.

[0239] The engineered stone slabs of comparative examples 6 and 9 and of inventive example 13 have the same content of resin and cristobalite fillers. Whereas the slabs of comparative examples 6 and 9 showed poor wetting properties or cracks in the stone slabs, the slabs prepared from the inventive resin in example 13 showed good wetting properties, did not bend and had no cracks.

[0240] Further, the stone slabs prepared from the inventive resin with cristobalite had considerably better mechanical properties. The flexural strength of the stone slab of example 13 was 105 MPa compared to only 60 MPa and 65 Mpa, respectively, of the stone slabs of comparative examples 6 and 9. Furthermore, the impact resistance was higher (inventive: 11 J/m vs. comparative: 5 J/m).