Flame-retardant polymer composition

Abstract

The invention relates to a flame-proofed polymeric composition suitable for coating workpieces, containing a vinyl acetate-containing thermoplastic polymer and an unsaturated elastomer containing double bonds as polymeric components, wherein the polymeric components are present in the form of a homogeneous polymeric mixture, and a mixture matrix vulcanized exclusively by a sulphur or sulphur-containing crosslinking system is formed, wherein the sulphur crosslinking system extends across the entire matrix and permeates the matrix completely, andat least one flame retardant or a combination of flame retardants. The invention further relates to articles produced therefrom, and to composite elements coated with this composition and to a method for producing the same.

Claims

1. A flame-resistant polymer composition, comprising: a thermoplastic polymer containing vinyl acetate; an unsaturated elastomer containing double bonds; and at least one flame retardant or a combination of flame retardants, said thermoplastic polymer and said unsaturated elastomer intermixed to form a homogenous mixture, said homogenous mixture vulcanised exclusively with sulphur or a sulphur-containing crosslinking agent so that a continuous system of sulphur crosslinks extends uninterruptedly through an entirety of the mixture.

2. The composition of claim 1, wherein the thermoplastic polymer is non-crosslinked, and the unsaturated elastomer is at least partially crosslinked via the sulphur crosslinks, and wherein the mixture does not contain crosslinks except the sulphur crosslinks.

3. The composition of claim 1, wherein chains of the thermoplastic polymer and sulphur-crosslinked chains of the elastomer spatially overlap one another.

4. The composition of claim 1, wherein the sulphur crosslinks include polysulphide and mono-and di-sulphide bonds, wherein a content of the polysulphide bonds is between 40 and 50%, and a content of the mono- and di-sulphide bonds is between 50 and 60%, relative to a total crosslink density of the mixture.

5. The composition of claim 1, wherein the mixture is substantially monophasic.

6. The composition of claim 1, wherein in a vulcanised state the homogenous mixture has elastomeric properties at a range of 150-200 C.

7. The composition of claim 1, wherein in a vulcanized state the homogenous mixture has no melting peak measured by dynamic differential calorimetry in a temperature range of up to 200 C.

8. The composition of claim 1, wherein in a vulcanized state the homogenous mixture has a loss factor defined as a ratio of loss to storage modulus in dynamic shearing stress of tan <0.3 in a temperature range from room temperature up to 200 C.

9. The composition of claim 1, further comprising at least one of additives and excipients, said composition being produced by mixing the thermoplastic polymer and the unsaturated elastomer to form the homogeneous mixture, adding the sulphur or the sulphur-containing crosslinking agent, the flame retardants, and the additives and/or excipients, whilst strictly avoiding any crosslinking and/or vulcanisation, after adding the sulphur or the sulphur-containing crosslinking agent, moulding and vulcanizing the mixture, wherein the vulcanizing is performed in absence of shearing stress.

10. The composition of claim 1, produced by static vulcanisation, in the absence of shearing stress or dynamic vulcanisation.

11. The composition of claim 1, wherein the thermoplastic polymer and the unsaturated elastomer are free of halogen.

12. The composition of claim 1, wherein the thermoplastic polymer is a homopolymer, copolymer, or terpolymer of vinyl acetate.

13. The composition of claim 1, wherein the thermoplastic polymer has a melting point or a melting range beginning at less than 150 C.

14. The composition of claim 1, wherein the thermoplastic polymer has a vinyl acetate content of 40-75 wt %.

15. The composition of claim 1, wherein the unsaturated elastomer is a homopolymer, copolymer, or a terpolymer consisting of or containing diene monomer units.

16. The composition of claim 1, wherein the unsaturated elastomer is a rubber with an unsaturated side group or an ethylene-propylene-diene rubber (EPDM) containing non-conjugated diene monomer units, selected from the group of 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-cyclopentadiene, dicyclopentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 1,4-hexadiene, 1,4-cyclohexadiene, tetrahydroindene, methyl tetrahydroindene, ethylidene norbornene or 5-ethylidene-2-norbornene (ENB), 5-methylene-2-norbornene (MNB), 1,6 octadiene, 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 5-isolpropylidene-2-norbornene, 5-vinyl-norbornene (VNB), wherein the ethylene-propylene-diene rubber (EPDM) is a terpolymer consisting of ethylene, propylene, and 5-ethylidene-2-norbornene (ENB) or dicyclopentadiene (DCPD).

17. The composition of claim 1, wherein the unsaturated elastomer is a rubber with an unsaturated main chain, wherein the unsaturated elastomer is partially hydrated and has a degree of hydration of 94-97%, and, prior to crosslinking, has a residual double bond content of 3-6% in the main chain relative to the initial double bond content in the main chain.

18. The composition of claim 1, wherein the sulphur that forms the sulphur crosslinks is contained in the composition in an amount of 0.3-2 phr (parts per hundred rubber) relative to a total amount of polymer components.

19. The composition of claim 18, wherein the sulphur is contained in an amount of at least 0.5 phr relative to a total amount of the polymer components.

20. The composition of claim 1, wherein the thermoplastic polymer is non-crosslinked and is present in an amount of 5-15 wt %, and the unsaturated elastomer is present in an amount of 20-40 wt %, relative in each case to the total weight of the composition.

21. The composition of claim 1, wherein the thermoplastic polymer mixture is non-crosslinked ethylene vinyl acetate (EVA) and the sulphur-crosslinked ethylene-propylene-diene rubber (EPDM) at a ratio of 40-20 wt % EVA to 60-80 wt % EPDM.

22. The composition of claim 1, further comprising at least one polyolefin selected from the group consisting of polyethylene and polypropylene.

23. The composition of claim 1, wherein the flame retardant(s) is/are present in an amount of 50-80 wt %, relative to the overall composition.

24. The composition of claim 1, further comprising at least one of magnesium hydroxide (MDH), aluminium hydroxide (ATH), and zinc borate.

25. The composition of claim 1, wherein the polymer containing vinyl acetate is present in an amount of 5-15 wt %, the unsaturated elastomer is present in an amount of 20-40 wt %, the flame retardant or flame retardants is/are present in an amount of 50-80 wt %, the remainder being excipient and additives.

26. The composition of claim 1, having a hardness of 50-75, Shore A, and/or an ultimate elongation of 200-600% and/or a tear resistance of >7 N/mm.

27. A method for producing a flame-resistant composition, comprising the steps in the order of: mixing a thermoplastic polymer containing vinyl acetate, an unsaturated elastomer, a crosslinking agent, a flame retardant, and additives and excipients into a homogeneous mixture whilst avoiding crosslinking and/or vulcanisation, moulding the mixture, and vulcanizing the mixture during or at the end of moulding, as a static, non-dynamic vulcanisation that avoids shearing exclusively with sulphur or a sulphur-containing crosslinking agent so that a continuous system of sulphur crosslinks extends uninterruptedly through an entirety of the mixture.

28. The method of claim 27, wherein the mixing is carried out at a temperature of no more than 125 C.

29. The method of claim 27, wherein the moulding is carried out at a temperature of no more than 130 C.

30. The method claim 27, wherein the vulcanisation occurs at a temperature of no more than 200 C. and at a pressure of 100-200 bar.

31. A flame-retardant article comprising a composition comprising a thermoplastic polymer containing vinyl acetate, an unsaturated elastomer containing double bonds, and at least one flame retardant or a combination of flame retardants, said thermoplastic polymer and said unsaturated elastomer intermixed to form a homogenous mixture, said homogenous mixture vulcanised exclusively with sulphur or a sulphur-containing crosslinking agent so that a continuous system of sulphur crosslinks extends uninterruptedly through an entirety of the mixture.

32. An elastic flame-retardant composite element, suited for vibration damping and suspension, said elastic flame-retardant composite element having a base, with at least a portion of an outer surface of the base having a coating made of a composition as set forth in claim 1.

33. The composite element of claim 32, wherein the base is made primarily of rubber.

34. The composite element of claim 32, wherein the coating is fixedly and inseparately attached to the base and is applied to the base by one of manufacture, extrusion, pressing, spraying, and subsequent coextrusion.

35. The composite element of claim 32, wherein the coating has a thickness of less than 10 mm.

36. The composite element of claim 32, wherein the coating has a weight percentage of 1-20 wt % of the elastic composite element.

37. The composite element of claim 32, wherein the base has a reinforcement selected from the group consisting of fibres, glass fibres, polymer fibres, CFK fibres, GFK fibres, and a fabric.

38. An article, comprising the composite element of claim 32, wherein the article is a spring element, damping element, gasket, hose, mat, moulding, protective clothing, or elastomer profile.

39. The flame-resistant polymer composition of claim 2, wherein the sulfur crosslinks include at least one of mono-, di-, and polysulphide bonds.

40. The flame-resistant polymer composition of claim 5, wherein the polymer mixture is free of elastomer particles or rubber domains with a mean diameter of more than 0.5 microns.

41. The flame-resistant polymer composition of claim 9, wherein the sulphur or sulphur containing crosslinking agent is added at a temperature of no more than 110 C.

42. The flame-resistant polymer composition of claim 11, wherein the composition is free of halogen.

43. The flame-resistant polymer composition of claim 12, wherein the polymer containing vinyl acetate is selected from the group consisting of polyvinyl acetate (PVAc) and ethylene vinyl acetate (EVA).

44. The flame-resistant polymer composition of claim 15, wherein the unsaturated elastomer is a terpolymer consisting of ethylene, propylene, and diene.

45. The flame-resistant polymer composition of claim 44, wherein the diene has a content of at least 2-12 wt % relative to the terpolymer.

46. The flame-resistant polymer composition of claim 24, wherein the flame retardants are solid and powdery or crystalline.

47. The composition of claim 4, wherein the content of the polysulphide bonds is 45%, and the content of the mono- and di-sulphide bonds is 55%, relative to the total crosslink density of the mixture.

48. The composition of claim 1, wherein the thermoplastic polymer has a melting point or a melting range beginning at less than 100 C.

49. The composition of claim 17, wherein the unsaturated elastomer is a partially hydrated acrylonitrile butadiene rubber (HNBR).

50. The composition of claim 20, wherein the thermoplastic polymer is present in an amount of 7-12 wt %, and the unsaturated elastomer is present in an amount of 20-30 wt %, relative in each case to the total weight of the composition.

51. The composition of claim 21, wherein the ratio is approximately 20-30 wt % EVA to 70-80 wt % EPDM.

52. The composition of claim 22, wherein the polyethylene is LLDPE.

53. The composition of claim 1, wherein the flame retardant(s) is/are present in an amount of 60-70 wt %, relative to the overall composition.

54. The composition of claim 1, having a hardness of 55-65, Shore A, and/or an ultimate elongation of 350-600% and/or a tear resistance of >9 N/mm.

55. The method of claim 27, wherein the mixing is carried out at a temperature of 50-110 C.

56. The method of claim 27, wherein the moulding is carried out at a temperature of 70-100 C.

57. The method claim 27, wherein the vulcanisation occurs at a temperature which is higher than a temperature during mixing or moulding.

58. The method claim 30, wherein the vulcanisation occurs at a temperature of 130-170 C.

59. The composite element of claim 33, wherein the rubber is selected from the group consisting of polybutadiene rubber, styrene butadiene rubber, acrylonitrile rubber, ethylene-propylene-diene rubber, sponge rubber, any mixture thereof, and natural rubber.

60. The composite element of claim 32, wherein the coating has a thickness of 1-5 mm.

61. The composite element of claim 32, wherein the coating has a weight percentage of 2-16 wt % of the elastic composite element.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The composite element 1 according to the invention is described in greater detail below based on exemplary embodiments shown schematically in the drawings by way of example only and without limitation.

(2) FIG. 1 shows a schematic cross-section of a composite spring as a first embodiment of an elastic composite element according to the invention.

(3) FIG. 2 shows, in a representation similar to FIG. 1, a schematic cross-section of a composite element consisting of a buffer or socket;

(4) FIG. 3 shows a schematic cross-section of a composite element consisting of a bellows;

(5) FIG. 4 shows a schematic cross-section of a rolling lobe of an air spring as a composite element;

(6) FIG. 5 shows a schematic cross-section of a flat store of a secondary spring as a composite element;

(7) FIG. 6 shows a schematic cross-section of a buffer as a composite element;

(8) FIG. 7 shows a schematic cross-section of a socket or guide bushing as a composite element;

(9) FIG. 8 also shows a schematic cross-section of a bearing or bush as a composite element;

(10) FIGS. 9 and 10 each show a schematic cross-section of various embodiments of a buffer or sealing element as a composite element;

(11) FIG. 11 shows a schematic cross-section of a deep tension spring or auxiliary spring as a composite element;

(12) FIG. 12 shows a schematic cross-section of a layer spring or auxiliary spring as a composite element;

(13) FIGS. 13 and 14 each show a schematic cross-section of various embodiments of a hollow spring as a composite element;

(14) FIG. 15 shows a schematic cross-section of a buffer or auxiliary spring as a composite element;

(15) FIG. 16 shows a schematic partial cross-section of a hose as a composite element.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(16) In the drawings, a wide variety of embodiments of elastic composite elements 1 is shown, each of which consists of a base 2 consisting primarily of rubber, whereby the composite element 1 can withstand dynamic stress. Additionally, the composite elements 1 shown in the drawings each have the flame-retardant or fire-resistant coating 4 according to the invention on at least part of their outer surfaces 3, which is arranged, in particular, on areas facing the outside of the respective composite element 1. Examples of material compositions for the various configurations of bases 2 are provided after a description of the drawings.

(17) FIG. 1 shows a schematic cross-section of a composite spring as a composite element 1, whereby a metallic spring element 5 is arranged in a base 2. In exposed areas, or areas of the surface 3 facing the outside, a flame-retardant or fire-resistant coating 4 with the characteristics according to the invention is additionally provided.

(18) In the buffer or socket composite element 1 schematically shown in FIG. 2, a base 2, which, in turn, consists of an elastic material, primarily rubber, is also provided over areas of its surface 3 with the coating 4.

(19) In the bellows shown in FIG. 3 as a composite element 1, it can be seen that substantially its entire outward surface 3 has the coating 4, whereby the base of the bellows is designated 2.

(20) Likewise, in FIG. 4, which shows a bellows of a rolling lobe of an air spring, it can be seen that the base 2 has the coating 4 on its entire outer surface 3.

(21) In the flat store schematically shown in FIG. 5 as a composite element 1, it can also be seen that the base 2 substantially has the coating 4 according to the invention substantially over its entire surface.

(22) In the case of the buffer or bearing shown schematically in FIG. 6, on the other hand, a coating 4 is provided only in some areas on the elastic base 2.

(23) In the case of the socket or guide bushing of FIG. 7, it can be seen, in turn, that the base 2 has the coating 4 on substantially its entire outward surface 3, whereby an insert 6 is additionally provided.

(24) Likewise, in the case of the socket shown in FIG. 8, the base 2 has the coating 4 on its entire outward surface 3, whereby another insert 6 is additionally provided.

(25) FIGS. 9 and 10 show different embodiments of a buffer as a composite element 1, whereby both in the configuration of FIG. 9 and in the configuration of FIG. 10, the base 2 is covered with a coating 4.

(26) In the case of the deep tension spring or auxiliary spring shown in FIG. 11, a base 2 is at least partially provided with the coating 4.

(27) The layer spring or auxiliary spring shown in FIG. 12 is similar, whereby the bases 2 each have a coating 4.

(28) In the schematic representations of FIGS. 13 and 14, it can be seen that various embodiments of a base 2 each have a coating 4 substantially on the entire outward surface 3.

(29) The primary spring or auxiliary spring shown in FIG. 15 is similar, whereby the bases 2 each have a coating 4.

(30) Additionally, FIG. 16 schematically shows a partial area of an elastic hose as a composite element 1, whereby the elastic base 2 is provided with the coating 4 for fire safety purposes.

(31) In addition to the uses for an elastic composite element 1 shown in the drawings as a spring element, damping element, a shock absorber element, hose, or bearing element, an element consisting of a base 1 and the flame-retardant or fire-resistant coating 4 according to the invention may also be used as a gasket, moulding, mat, or protective clothing, e.g., protective gloves.

(32) Examples for the Base 2 of the Composite Element 1:

(33) To form the base 2, which primarily consists of rubber, for various purposes, a number of exemplary formulations are listed below for appropriate material properties, whereby the percentages refer to weight unless otherwise stated.

(34) TABLE-US-00004 GK 1 GK 2 GK 3 50 ShA 60 ShA 70 ShA Natural rubber 57 51 48 Filler and reinforcer 33 41 45 Plasticiser 1.5 0.7 0.2 Accelerant and Crosslinking agent 2.5 2.2 2.0 (sulphur) Anti-aging agent 1 0.9 0.8 Activator 3 2.5 2.4 Processing aid 2 1.7 1.6

(35) TABLE-US-00005 GK 4 GK 5 GK 6 55 ShA 60 ShA 65 ShA Acryl-nitrile-butadiene rubber 58 53 48 Carbon black (Filler and reinforcer) 20 27 34 Plasticiser 15 12 10 Accelerants + 2.50 2.50 2.50 Crosslinking agent (sulphur donor) Activator 2.50 2.50 2.50 Processing aid 2 3 3

(36) TABLE-US-00006 GK7 65 ShA Natural rubber 25 Styrene-butadiene rubber 15 Bromobutyl 10 Fillers 42 Accelerants 1.0 Crosslinking agents 1.5 Activators 3.50 Processing aid 2

(37) In the tables above, various examples GK 1-GK 7 are listed for bases 2 with various Shore hardnesses A.

(38) The exemplary embodiments according to GK 1, 2, and 3 are highly elastic rubber materials for use in a dynamic or highly dynamic application, e.g., as primary and secondary springs, as shown, e.g., in FIG. 1, FIG. 5, FIG. 6, FIG. 12, or FIG. 15. The base 2 of the elastic elements according to GK 4, 5, and 6 are characterised in particular by high resistance to external contamination such as mineral oil, and can be used, e.g., in combination with sockets or bearings, as is the case for the exemplary embodiments according to FIG. 7, 8, or FIG. 11. In example 7, a base 2 of an elastic composite element 2 with good energy-absorbent properties is provided, whereby such material properties can be used, in particular, for the hollow springs shown in FIGS. 13 and 14.

(39) Method for Producing a Composite Element 1 according to the invention: The production of the flame-resistant, dynamic stress resistant composite element 1 may be carried out by various methods known to persons skilled in the art. The required thickness of the coating 4 may be obtained by calendering or extrusion or direct injection (IM) or pressing (TM, CM) onto the base 2 to be coated.

(40) The coating 4 may be applied in various pressing methods.

(41) On the one hand, the protective layer mixture of the composition may be directly applied by the roller mill by assembly to a preform of the rubber mixture, produced by extrusion (e.g., Barwell) or by strip cutting. Then, the semi-finished product may be jointly vulcanised by compression moulding. Alternatively, a pre-vulcanised or vulcanised article may, after appropriate pretreatment of the surface 3, e.g., washing with solvents and/or roughening and any adhesive coating, may be coated or sprayed with the not yet vulcanised composition or coating 4 according to the invention, which can be vulcanised onto the article or base 2 to be protected.

(42) Flat products, with or without strengthening inserts, may have, e.g. calendering webs of the flame retardant mixture according to the invention applied to them and vulcanised under pressure in presses or autoclaves. When producing, e.g., hoses or profiles by extrusion, the flame-retardant mixture according to the invention may be continuously applied by means of a second extruder to the extruded core or base 2 to be protected and vulcanised together with it.

(43) The advantageous sulphur crosslinking system, like all other methods, allows he vulcanisation speeds of the base 2 and the protective mixture applied to be adjusted such that optimal covulcanisation, and thus an optimal bond, can be obtained. At the same time, all continuous vulcanisation lines commonly used in extrusion may be used, e.g., UHF, HL, IR, salt bath.

(44) Vulcanisation occurs at a temperature of less than 200 C., preferably 130-170 C. The vulcanisation times depend on the production method and the geometry of the component. In the case of joint covulcanisation, the vulcanisation characteristics of the core material used also determine the heating conditions, which are known to persons skilled in the art.

(45) Example of Production of a Composite Element 1

(46) In the example below, an elastic bearing having the dimensions 10010050 mm is produced as a composite element 1. The core mixture of the base 2 is a natural rubber mixture having the following properties when vulcanised:

(47) Hardness: 60 Shore A (DIN ISO 7619-1)

(48) Tensile strength: 18 N/mm2 (DIN 53504)

(49) Ultimate elongation: 470 A, (DIN 53504)

(50) Spring stiffness: 1702 N/mm

(51) The spring stiffness is determined on a universal testing machine between two planoparallel pressure plates. The spring stiffness determination is preceded by five deflections up to a pitch of 20 mm at a speed of 200 mm/min. The spring stiffness is determined in the linear range between 5 and 10 mm pitch.

(52) The core mixture is prevulcanised, and the finished core or base 2 has the dimensions 929242 mm. The moulding and prevulcanisation occur at a temperature of 155 C., a heating time of 40 min, and a pressure of 200 bar in the CM method in the electrically heated press. The demoulded core is cleaned with acetone, and the protective layer (exemplary formulation 1) is applied on all sides of the base 2 in a thickness of 4 mm. The final moulding and vulcanisation of the composite are carried out by the CM method at a temperature of 155 C., a heating time of 15 min, and a pressure of 200 bar. After vulcanisation, the composite element 1 is cooled at room temperature, and the excess was mechanically removed. The spring stiffness is termined on the composite bearing consisting of core material and exemplary mixture 1 (see conditions for core material).

(53) The spring stiffness of the composite element 1 is 1680 N/mm, only slightly below the spring stiffness of the base 2. Additionally, within CEN TS 45545-2, the heat release rate of the component according to ISO 5660-1 with ARHE=66 kW/m2 is determined.