Compositions of expandable vinyl aromatic polymers with an improved thermal insulation capacity, process for their preparation and expanded articles obtained therefrom

Abstract

Expandable vinyl aromatic polymers which comprise: a matrix obtained by polymerizing 50-100% by weight of one or more vinyl aromatic monomers and 0-50% by weight of at least one copolymer izable monomer; 1-10% by weight, calculated with respect to the polymer (a), of an expanding agent englobed in the polymeric matrix; 0.05-25% by weight, calculated with respect to the polymer (a), of a filler comprising coke with a surface area, measured according to ASTM D-3037/89, ranging from 5 to 50 m.sup.2/g.

Claims

1. A composition, comprising an expandable vinyl aromatic polymer comprising: (a) a polymeric matrix (a) obtained by polymerizing a base comprising 50-100% by weight of at least one vinyl aromatic monomer and 0-50% by weight of at least one co-polymerizable monomer; (b) 1-10% by weight, calculated with respect to the polymeric matrix (a), of an expandable agent (b) englobed in the polymeric matrix (a); and (c) 1-8% by weight, calculated with respect to the polymeric matrix (a), of at least one coke selected from the group consisting of a needle coke and a calcined coke, in particle form with an average diameter of particles ranging from 0.5 to 100 μm and with a surface area, measured according to ASTM D-3037/89 (BET), ranging from 5 to 50 m.sup.2/g; said at least one coke being homogeneously dispersed in the polymeric matrix (a); and wherein expanded articles derived from said composition have a density ranging from 5 to 50 g/l and a thermal conductivity more than 10% lower than the same expanded articles without added athermanous filler.

2. The composition according to claim 1, further comprising: from 0.1 to 8% by weight, with respect to the polymeric matrix (a), of a self-extinguishing brominated additive (d) comprising at least 30% by weight of bromine and 0.05 to 2% by weight, with respect to the polymeric matrix (a), of a synergic product comprising at least one labile C—C or O—O bond.

3. An expanded article having a density ranging from 5 to 50 g/l and a thermal conductivity ranging from 25 to 35 mW/mK, said article obtained from an expandable vinyl aromatic polymer comprising: (a) a polymeric matrix (a) obtained by polymerizing a base comprising 50-100% by weight of at least one vinyl aromatic monomer and 0-50% by weight of at least one co-polymerizable monomer; (b) 1-10% by weight, calculated with respect to the polymeric matrix (a), of an expandable agent (b) englobed in the polymeric matrix (a); and (c) 1-8% by weight, calculated with respect to the polymeric matrix (a), of at least one coke selected from the group consisting of a needle coke and a calcined coke, in particle form with an average diameter of particles ranging from 0.5 to 100 μm and with a surface area, measured according to ASTM D-3037/89 (BET), ranging from 5 to 50 m.sup.2/g; said at least one coke being homogeneously dispersed in the polymeric matrix (a), wherein said expanded article has a thermal conductivity more than 10% lower than the same expanded article without added athermanous filler.

4. The composition according to claim 1, wherein the expandable vinyl aromatic polymer is in the form of granules having a surface comprising at least one of an ionic surface active agent and a non-ionic surface active agent that comprises a condensate of ethylene oxide and propylene oxide.

5. The expanded article according to claim 3, wherein the expandable vinyl aromatic polymer is in the form of granules having a surface comprising at least one of an ionic and a non-ionic surface active agent that comprises a condensate of ethylene oxide and propylene oxide.

6. The composition of claim 1, which is in the form of granules, wherein the coke is homogenously dispersed in the granules.

7. The expanded article of claim 3, wherein the expandable vinyl aromatic polymer is in the form of granules, wherein the coke is homogenously dispersed in the granules.

8. The composition according to claim 1, wherein the coke has a surface area of from 5 to 20 m.sup.2/g.

9. The expanded article according to claim 3, wherein the coke has a surface area of from 5 to 20 m.sup.2/g.

10. The composition according to claim 1, which does not comprise graphite.

11. The expanded article according to claim 3, which does not comprise graphite.

12. The composition according to claim 1, comprising 4-8% by weight of the coke.

13. The expanded article according to claim 3, comprising 4-8% by weight of the coke.

14. The composition according to claim 1, in the form of thermally expandable pellets, wherein the coke is dispersed homogeneously in the pellets.

15. The composition according to claim 1, wherein expanded articles derived from said composition have a density ranging from 10 to 25 g/l and a thermal conductivity ranging from 25 to 35 mW/mK.

16. The composition according to claim 1, wherein extruded articles obtained from said composition have a density ranging from 20 to 40 g/l and a thermal conductivity ranging from 25 to 35 mW/mK.

17. The expanded article according to claim 3, having a density ranging from 20 to 40 g/l.

18. The expanded article according to claim 3, having a density ranging from 10 to 25 g/l.

19. The composition according to claim 1, wherein expanded articles obtained from said composition have a density from 10 to 25 g/l and a thermal conductivity ranging from 30.5 to 35 mW/mK.

20. The expanded article according to claim 3, having a density ranging from 10 to 25 g/l and a thermal conductivity ranging from 30.5 to 35 mW/mK.

21. A composition, comprising an expandable vinyl aromatic polymer comprising: (a) a polymeric matrix (a) obtained by polymerizing a base comprising at least one vinyl aromatic monomer selected from the group consisting of styrene and α-methylstyrene; (b) 1-10% by weight, calculated with respect to the polymeric matrix (a), of an expandable agent (b) englobed in the polymeric matrix (a); and (c) 1-8% by weight, calculated with respect to the polymeric matrix (a), of at least one coke selected from the group consisting of a needle coke and a calcined coke, in particle form with an average diameter of particles ranging from 0.5 to 100 μm and with a surface area, measured according to ASTM D-3037/89 (BET), ranging from 5 to 50 m.sup.2/g; said at least one coke being homogeneously dispersed in the polymeric matrix (a); and wherein expanded articles derived from said composition have a density ranging from 5 to 50 g/l and a thermal conductivity ranging from 25 to 35 mW/mK.

22. The composition according to claim 21, further comprising: from 0.1 to 8% by weight, with respect to the polymeric matrix (a), of a self-extinguishing brominated additive (d) comprising at least 30% by weight of bromine and 0.05 to 2% by weight, with respect to the polymeric matrix (a), of a synergic product comprising at least one labile C—C or O—O bond.

23. An expanded article having a density ranging from 5 to 50 g/l and a thermal conductivity ranging from 25 to 35 mW/mK, said article obtained from an expandable vinyl aromatic polymer comprising: (a) a polymeric matrix (a) obtained by polymerizing a base comprising at least one vinyl aromatic monomer selected from the group consisting of styrene and α-methylstyrene; (b) 1-10% by weight, calculated with respect to the polymeric matrix (a), of an expandable agent (b) englobed in the polymeric matrix (a); and (c) 1-8% by weight, calculated with respect to the polymeric matrix (a), of at least one coke selected from the group consisting of a needle coke and a calcined coke, in particle form with an average diameter of particles ranging from 0.5 to 100 μm and with a surface area, measured according to ASTM D-3037/89 (BET), ranging from 5 to 50 m.sup.2/g; said at least one coke being homogeneously dispersed in the polymeric matrix (a).

Description

EXAMPLE 1

(1) A mixture is charged into a closed and stirred container, consisting of 150 parts by weight of water, 0.2 parts of sodium pyrophosphate, 100 parts of styrene, 0.25 parts of tert-butylperoxy-2-ethylhexanoate, 0.25 parts of tert-butyl perbenzoate and 1 part of Calcinated Coke 4023 sold by the company Asbury Graphite Mills Inc. (USA), having a particle diameter MT50% of about 5 μm, a BET of about 20 m.sup.2/g. The mixture is heated under stirring to 90° C.

(2) After about 2 hours at 90° C., 4 parts of a solution of polyvinylpyrrolidone at 10% are added. The mixture is heated to 100° C., still under stirring, for a further 2 hours, 7 parts of a 70/30 mixture of n-pentane and i-pentane are added, the whole mixture is heated for a further 4 hours to 125° C., it is then cooled and the batch is discharged.

(3) The granules of expandable polymer thus produced are subsequently collected and washed with demineralized water containing 0.05% of a non-ionic surface-active agent consisting of a fatty alcohol condensed with ethylene oxide and propylene oxide, sold by Huntsman under the trade-name of Empilan 2638. The granules are then dried in a warm air flow, 0.02% of a non-ionic surface-active agent is added, consisting of a condensate of ethylene oxide and propylene oxide on a glycerine base, sold by Dow (Voranol CP4755) and they are subsequently screened separating a fraction with a diameter ranging from 1 to 1.5 mm.

(4) This fraction proved to represent 40%, 30% being the fraction between 0.5 and 1 mm, 15% the fraction between 0.2 and 0.5 mm, and 15% the gross fraction, between 1.5 and 3 mm.

(5) 0.20 of glyceryl monostearate and 0.1% of zinc stearate are then added to the fraction of 1 to 1.5 mm.

(6) The product is pre-expanded with vapour at a temperature of 100° C., left to age for 1 day and used for the moulding of blocks (having dimensions of 1040×1030×550 mm).

(7) The blocks were then cut to prepare flat sheets on which the thermal conductivity is measured. The thermal conductivity, measured after 5 days of residence in an oven at 70° C., was 35.0 mW/mK whereas that of a sheet having the same density (17 g/l) prepared with a traditional reference product (EXTIR A-5000) was equal to 40 mW/mK.

COMPARATIVE EXAMPLE 1

(8) The same procedure is adopted as in Example 1 with the exception that the coke is substituted with carbon black N990 produced by Concarb (USA). This carbon has a diameter of the primary particles of about 230 nm and a surface area (BET) of about 12 m.sup.2/g.

(9) The sheet obtained has a thermal conductivity of 36.5 mW/mK.

EXAMPLE 2

(10) A mixture is charged into a closed and stirred container, consisting of 150 parts by weight of water, 0.2 parts of sodium tricalcium phosphate, 100 parts of styrene, 0.25 parts of tert-butylperoxy-2-ethylhexanoate, 0.25 parts of tert-butylperbenzoate, 0.01 parts of sodium metabisulphite and 2 parts of the coke used in example 1. The mixture is heated under stirring to 90° C.

(11) After about 2 hours at 90° C., the mixture is heated for a further 2 hours to 100° C., 7 parts of a 70/30 mixture of n-pentane and i-pentane are added, the mixture is heated for a further 4 hours to 125° C., it is then cooled and discharged.

(12) The granules of expandable polymer thus produced are processed as in example 1, separating the fraction with a diameter ranging from 1 to 1.5 mm.

(13) This fraction proved to represent 60%, 25% being the fraction from 0.5 to 1 mm, 5% the fraction from 0.2 to 0.5 mm, and 10% the gross fraction, from 1.5 to 3 mm.

(14) 0.2% of glyceryl monostearate and 0.1% of zinc stearate are added to the fraction of 1 to 1.5 mm.

(15) The expansion and moulding were effected as described in example 1. The thermal conductivity proved to be 34.5 mW/mK.

EXAMPLE 3

(16) A mixture is charged into a closed and stirred container, consisting of 150 parts by weight of water, 0.2 parts of sodium tricalcium phosphate, 100 parts of styrene, 0.30 parts of tert-butylperoxy-2-ethylhexanoate, 0.25 parts of tert-butylperbenzoate, 0.01 parts of sodium metabisulphite and 4 parts of the coke used in example 1. The mixture is heated under stirring to 90° C.

(17) After about 2 hours at 90° C., the mixture is heated for a further 2 hours to 100° C., 7 parts of a 70/30 mixture of n-pentane and i-pentane are added, the mixture is heated for a further 4 hours to 125° C., it is then cooled and discharged.

(18) The granules of expandable polymer thus produced are processed as in example 1, separating the fraction with a diameter ranging from 1 to 1.5 mm.

(19) This fraction proved to represent 60%, 25% being the fraction from 0.5 to 1 mm, 5% the fraction from 0.2 to 0.5 mm, and 10% the gross fraction, from 1.5 to 3 mm.

(20) 0.2% of glyceryl monostearate and 0.1% of zinc stearate are added to the fraction of 1 to 1.5 mm.

(21) The expansion and moulding were effected as described in example 1. The thermal conductivity proved to be 33 mW/mK.

EXAMPLE 4

(22) Example 2 was repeated substituting the Calcinated Coke 4023 with the type Needle Coke 4727 sold by Asbury Graphite Mills Inc. (USA) having a particle diameter MT50% of about 6 microns, a BET of about 11 m.sup.2/g. The thermal conductivity proved to be 34 mW/mK at 17 g/l.

EXAMPLE 5

(23) Example 4 was repeated adding, in addition to 2% of coke 4727, 2% of Carbon Black N990, produced by Concarb (USA). The thermal conductivity proved to be 32.5 mW/mK at 17 g/l.

EXAMPLE 6

(24) Example 3 was repeated adding 1.5% of hexabromocyclododecane, Saytex HP900 sold by Albmarle and 0.3% of dicumyl peroxide to make the product fireproof. The fraction of 1 to 1.5 mm is then processed as in Example 1. The sheets are put in an oven at 70° C. for 2 days to remove the residual pentane. Test samples are then collected (9 cm×19 cm×2 cm) for the fire behaviour test according to the regulation DIN 4102. The test samples pass the test. The thermal conductivity remains unvaried.

EXAMPLE 7

(25) 78 parts of polystyrene N1782 produced by Polimeri Europa; 2 parts of ethylene-bis-stereamide; 20 parts of Calcinated Coke 4023 used in Example 1, are mixed in a twin-screw extruder. The extruded product is used as master-batch, in the production of the expandable compositions of the present invention illustrated hereunder.

(26) 89.8 parts of ethylbenzene, 730.0 parts of styrene, 56.2 parts of α-methylstyrene and 0.2 parts of divinylbenzene are fed to a stirred reactor.

(27) 123.8 parts of the master-batch prepared as indicated above are fed into the reactor and dissolved (total: 1,000 parts). The reaction is carried out at 125° C. with an average residence time of 2 hours. The fluid composition at the outlet is then fed to a second reactor where the reaction is completed at 135° C. with an average residence time of 2 hours.

(28) The resulting composition, which is hereafter referred to as “Composition (A)”, having a conversion of 72%, is heated to 240° C. and subsequently fed to the devolatilizer to remove the solvent and residual monomer. It is characterized by a glass transition temperature of 104° C., a melt flow index (MFI 200° C., 5 kg) of 8 g/10′, a molecular weight Mw of 200,000 g/mol and a Mw/Mn ratio of 2.8, wherein Mw is the weight average molecular weight and Mn is the number average molecular weight.

(29) Composition (A) is fed, from the devolatilizer, to a heat exchanger to lower its temperature to 170° C.

(30) 120.7 parts of polystyrene N2982 produced by Polimeri Europa, 24.2 parts of BR-E 5300 (stabilized hexabromocyclododecane, sold by Chemtura) and 5.1 parts of Perkadox 30® (2,3-dimethyl-2,3-dihpenylbutane, sold by Akzo Nobel) for a total of 150 parts, are fed to a second twin-screw extruder. A gear pump increases the feeding pressure of this molten additive to 260 barg. 47 parts of a mixture of n-pentane (75%) and iso-pentane (25%) are then pressurized and injected into the feeding of the additive. The mixing is completed with the use of static mixers, at a temperature of about 190° C. The composition thus obtained is described hereunder as “Composition (B)”.

(31) Composition (B) is added to 850 parts of Composition (A) coming from the heat exchanger. The ingredients are then mixed by means of static mixing elements for a calculated average residence time of 7 minutes. The composition is then distributed to the die, where it is extruded through a number of holes having a diameter of 0.5 mm, immediately cooled with a jet of water and cut with a series of rotating knives (according to the method described in U.S. Pat. No. 7,320,585).

(32) The pressure in the granulation chamber is 5 barg and the shear rate is selected so as to obtain granules having an average diameter of 1.2 mm. The water is used as a cooling spray liquid and nitrogen is used as carrier gas.

(33) The resulting granules are dried with a centrifugal drier and then covered with a coating. The coating is prepared by adding to the granules 3 parts of glyceryl monostearate, 1 part of zinc stearate and 0.2 parts of glycerine per 1,000 parts of dried granules. The additives of the coating are mixed with the granulate by means of a continuous screw mixer.

(34) The expansion of the granules and moulding were effected as described in Example 1. The thermal conductivity proved to be 32.0 mW/mK.

(35) Some of the sheets, obtained as described in Example 1, are put in an oven at 70° C. for 2 days. Test samples are then collected (9 cm×19 cm×2 cm) for the fire behaviour test according to the regulation DIN 4102. The test samples pass the test.

EXAMPLE 8

(36) 68 parts of polystyrene N1782; 2 parts of ethylene-bis-stereamide; 30 parts of Needle Coke 4727 are mixed in a twin-screw extruder. The extruded product, hereafter referred to as composition “C”, is used as master-batch, in the production of the expandable compositions of the present invention.

(37) 89.8 parts of ethylbenzene, 853.8 parts of styrene, 56.4 parts of α-methylstyrene (total: 1,000 parts) are fed to a stirred reactor.

(38) The reaction is carried out at 125° C. with an average residence time of 2 hours. The outgoing fluid composition is then fed to a second reactor where the reaction is completed at 135° C. with an average residence time of 2 hours.

(39) The resulting composition, hereafter referred to as “Composition D”, having a conversion of 72%, is heated to 240° C. and subsequently fed to the devolatilizer to remove the solvent and residual monomer. The composition is fed, from the devolatilizer, to a heat exchanger to lower its temperature to 170° C.

(40) 120.7 parts of polystyrene N2982, 24.2 parts of BR-E 5300 (stabilized hexabromocyclododecane, sold by Chemtura), 5.1 parts of Perkadox 30® (2,3-dimethyl-2,3-dihpenylbutane, sold by Akzo Nobel) and 133.3 parts of composition C indicated above, for a total of 283.3 parts, are fed to a second twin-screw extruder. A gear pump increases the feeding pressure of this molten additive to 260 barg. 47 parts of a mixture of n-pentane (75%) and iso-pentane (25%) are then pressurized and injected into the feeding of the additive. The mixing is completed with static mixers, at a temperature of about 190° C.

(41) The composition thus mixed is added to 716.7 parts of Composition (D) coming from the heat exchanger. The ingredients are then mixed by means of static mixing elements for a calculated average residence time of 7 minutes. The composition is then distributed to the die, where it is extruded through a number of holes having a diameter of 0.7 mm, immediately cooled with a jet of water and cut with a series of rotating knives as in Example 7, so as, however, to obtain granules having an average diameter of 1.4 mm.

(42) The resulting granules are dried with a centrifugal drier and then covered with a coating, as described in previous Example 7.

(43) The empty fraction f proved to be 7.7%, whereas the average diameter of the cavities, observed with the help of an optical microscope, is 15-60 μm.

(44) The expansion of the granules and moulding were effected as described in Example 1. The thermal conductivity proved to be 31 mW/mK.

(45) Some of the sheets, obtained as described in Example 1, are put in an oven at 70° C. for 2 days. Test samples are then collected (9 cm×19 cm×2 cm) for the fire behaviour test according to the regulation DIN 4102. The test samples pass the test.

EXAMPLE 9

(46) 926.5 parts of polystyrene N1782, 40 parts of Needle Coke 4727, 10 parts of HTP2 talc produced by Imi Fabi, 4 parts of Perkadox 30 and 19.5 parts of BR-E 5300 (total: 1,000 parts) are mixed in a twin-screw extruder.

(47) The mixture thus obtained is brought to a pressure of 250 bar by means of a gear pump.

(48) 95 parts of the molten composition thus obtained are mixed with 5 parts of a mixture of n-pentane (75%) and iso-pentane (25%).

(49) The resulting product is brought to a temperature of 160° C.; it is then granulated, dried and covered with a coating under the conditions described in Example 8.

(50) The empty fraction proved to be 6.5%.

(51) The expansion of the granules and moulding were effected as described in Example 1. The thermal conductivity proved to be 30.8 mW/mK.

(52) Some of the sheets, obtained as described in Example 1, are put in an oven at 70° C. for 2 days. Test samples are then collected (9 cm×19 cm×2 cm) for the fire behaviour test according to the regulation DIN 4102. The test samples pass the test.

EXAMPLE 10

(53) Example 7 was repeated increasing the concentration of coke 4023 from 123.8 parts to 247.6 parts. As in Example 7, the 247.6 parts of concentrate are fed to the reactor and dissolved (total: 1,000 parts). The thermal conductivity proved to be 30.5 mW/mK.

EXAMPLE 11

(54) A mixture (A) consisting of 98 parts of polystyrene N1782 and 2 parts of Calcinated Coke 4023 of Example 1 is fed in continuous to a system of two extruders in series.

(55) The temperature inside the first extruder is 220° C. to allow the polystyrene to melt and mix it with the additives.

(56) 2 parts of ethyl alcohol and 4 parts of carbon dioxide as expanding agent with respect to 100 parts of the mixture (A) are fed to the mixture thus obtained.

(57) The polymeric melt comprising the expansion system is homogenized and cooled to 120° C. and extruded through a die having a rectangular transversal section and dimensions of 300 mm×1.5 mm.

(58) A continuous sheet having a thickness of 120 mm is obtained. The density of the sheet is 35 g/l, the average size of the cells (substantially spherical) inside the sheet is about 500 μm. The thermal conductivity proved to be 34 mW/mK.

COMPARATIVE EXAMPLE 11

(59) The same procedure is repeated as in Example 11 with the exception that no athermanous agent is incorporated.

(60) The sheet obtained has a density of 35 g/l and an average size of the cells inside again of about 500 μm. The thermal conductivity proved to be 38 mW/mK.