WO2012024709A1 - Flame-retardant, heat-insulating polymers and method for producing same - Google Patents

Abstract

The invention relates to flame-retardant, expandable polymers that contain at least one flameproofing agent and that contain one or more solids, which are composed of carbon atoms at more than 70 wt % and which in particular exist in the form of athermanous particles. According to the invention, said solid(s) has/have a sulfur content of 0.2 to 30 wt %, preferably 0.3 to 15 wt %, preferably 0.6 to 10 wt %, especially preferably 1.2 to 7 wt%, in the form of sulfur and/or sulfur compounds.

Description

 Flame-retardant, heat-insulating polymers and process for their preparation

The invention relates to flame-retardant expandable polymers according to the preamble of claim 1 and the production of polymer foam insulating bodies thereof.

 Foamed insulating materials produced from expandable polymers (for example from expandable styrene polymer particles (EPS)) or polymer extruded foams (for example styrene polymer extruded foams (XPS)) are known from the prior art.

 The expandable polymers are usually propellant-containing

Polymer particles, e.g. from polystyrene or cellulose acetate butyrate, which can be expanded by heating with steam (Vorschäumprozess) under multiplication of their volume and then by welding to arbitrarily shaped moldings, in particular to plates or blocks, can be processed.

 Several processes are known for the preparation of expandable polymers. By suspension polymerization, e.g. expandable polystyrene can be prepared by polymerization of styrene and gassing with a blowing agent.

 Furthermore, expandable or expanded polymers can be mechanically processed by extrusion of polymer melts and mixing of a blowing agent in the polymer melt and subsequent promotion through a nozzle plate to extruded granules (eg EPS granules), or by foaming directly after a nozzle into foamed sheets (XPS sheets) are processed.

 Furthermore, processes are known in which expandable styrene polymers are produced by means of static mixing elements, see, for example, EP 0 668 139 (Sulzer Chemtech AG).

 Preferred fields of application of such polymer foams are thermal insulation materials such as EPS, e.g. for building facades, cold stores or packaging materials.

The equipment of polymer foams with flame retardants is important for many areas. Regulations governing the use of expandable polystyrene (EPS) or expanded polystyrene (XPS) expanded polystyrene foam as insulating material for buildings, in most cases, require flame retardant equipment thereof. Polystyrene homo- and copolymers are made predominantly with halogen-containing, in particular brominated organic compounds such as hexabromocyclododecane (HBCD) or brominated styrene copolymer, flame retardant. As an alternative, there are many halogen-free flame retardants. Halogen-free flame retardants need However, to achieve the same flame retardancy of the halogen-containing flame retardants usually be used in significantly higher amounts.

 Flame-retardant styrenic polymers are usually added to support a mostly halogenated flame retardant, one or more thermal radical generators such as dicumyl or peroxides as a flame retardant synergist such as e.g. EP 0 374 812 A1 (BASF AG). Especially suitable are thermal free-radical formers with short half-lives at temperatures of 140 to 300 ° C, e.g. Dicumyl peroxide, di-t-butyl peroxide or t-butyl hydroperoxide.

 However, radicals which are formed in particular from peroxides and thermal radical formers, when using, for example, extruders or static mixers-in the interaction of high temperature and shear stress-lead to a particularly high degradation of the polymer chains. For this reason, the production of expandable polymer particles or extruded polymer foam boards, which contain a thermal radical generator as a synergist in addition to the actual flame retardant problematic.

 According to the publication WO 2006 007995 A1 (BASF AG), which describes a process for the preparation of flame-retardant, expandable polystyrene, a method is provided, which attempts to reduce the chain by a minimum residence time of, in particular less than, 15 min of To keep peroxide in the polymer melt low. This can e.g. can be achieved by the synergist is not promoted with the polymer melt over the entire extruder length, but added only within one of the end zones of the extruder, for example via pumps or side extruder.

 However, this approach requires a high expenditure on equipment and involves the risk of ultimately non-homogeneous mixing of the flame retardant synergist into the styrene polymer melt. Degradation by resulting radicals must still be mitigated by radical scavengers.

 In WO 2009 033200 A1 (Sunpor Kunststoff GMBH) this problem is solved by the use of stable free radicals from the group of organic nitroxyl radicals. These free radicals are relatively expensive.

The publication "Studies of degradation enhancement of polystyrene by flame retardant additives", Mark W. Beach et al., Polymer Degradation and Stability, Volume 93, Issue 9, September 2008, 1664-1673 discloses that yellow sulfur is used as a flame retardant synergist in Polystyrene foams can be used. The addition of elemental sulfur promotes the retreat of the polystyrene foam from the flame area by chain degradation. The use of sulfur or sulfur compounds as flame retardant synergists in halogenated or non-halogenated flame retardant systems in the processing of polymers with extruders or static mixers would be advantageous because sulfur, for example, under the usual conditions of producing expandable polystyrene granules, does not favor the degradation reactions of the polymer during extrusion.

 The major disadvantage, however, is that when processed with extruders or static mixers of sulfur and most sulfur compounds, small amounts of e.g. Mercaptans, sulfides, hydrogen sulfide, sulfur dioxide and similar substances that are extremely odor-intensive and smell unpleasant and / or strong pungent. These odors are also in, from the polymers thus produced molded foam bodies intense and make them virtually unsalable. The object of the invention is a body, in particular a

Shaped body of a foamed polymer such as polystyrene or cellulose acetate butyrate, in particular made of polystyrene foam particles or an extruded polystyrene foam board, which makes use of the advantages of sulfur and is substantially free of odor.

Surprisingly, the object was achieved by the use of sulfur-containing solids, consisting predominantly of atoms of the element carbon, in particular caused by natural Kohlenohlungsprozesse in the earth's crust and / or by artificially generated Kohlenohlungsprozesse natural or synthetic materials, mainly consisting of carbon atoms and a content of sulfur from 0.2 to 30 wt .-%, preferably from 0.3 to 15 wt .-%, preferably from 0.6 to 10 wt .-%, particularly preferably from 1, 2 to 7 wt .-%, based on the predominantly carbon-containing solid, in the form of sulfur and / or sulfur compounds, in, preferably halogenated or phosphate-containing, flame retardants polymers provided.

In this case, the sulfur and / or the sulfur compounds are contained in the solid itself or integrated or contained in the matrix of the solid or athermanic material. There is no mere admixture of sulfur and / or sulfur compounds to a polymer in which already contain sulfur-free solids or athermane materials or were added independently of the sulfur - this would lead to the mentioned odor nuisance. It has surprisingly been found that such a polymer or such a foam body due to the synergistic effect of sulfur has an improved flame retardancy, but still no disturbing odors occur, although this would be expected at such sulfur levels in any case.

For the use of solids, consisting predominantly of carbon atoms are preferably particles having a particle size in the range of 0.5 or 1 to 50 μι ^η , preferably from 1 to 30 μηη, more preferably from 1 to 10 μητι. Both isotropic and anisotropic solids are suitable. Platelet-shaped particles having a high aspect ratio are particularly preferred. These can preferably be produced in delaminating mills, for example in ball mills or air jet mills.

 The preferred amounts used are between 0.5 and 10 wt .-%, based on the weight of the polymer granules produced.

 Preferably, the athermanous particles or solids are homogeneously and evenly distributed in the polymer.

 The expandable polymers of the present invention include all thermoplastic, expandable thermoplastics, e.g. Polystyrene, cellulose acetobutyrate, polyethylene, polypropylene, polyethylene terephthalate, polylactic acid, and mixtures of various thermoplastics.

 The expandable polymers according to the invention are preferably expandable styrene polymers (EPS) or expandable styrene polymer granules (EPS) which are in particular homopolymers and copolymers of styrene, preferably glass-clear polystyrene (GPPS), impact polystyrene (HIPS), anionically polymerized polystyrene or impact polystyrene (A). IPS), styrene-alpha-methylstyrene copolymers, acrylonitrile-butadiene-styrene polymers (ABS), styrene-acrylonitrile (SAN) acrylonitrile-styrene-acrylic ester (ASA), methyl acrylate-butadiene-styrene (MBS), methyl methacrylate-acrylonitrile-butadiene- Styrene (MABS) polymers or mixtures thereof or with polyphenylene ether (PPE) exist. Especially for polystyrene, the need for high quality products is particularly high.

The abovementioned styrene polymers may be used to improve the mechanical properties or the thermal stability, if appropriate by using compatibilizers with thermoplastic polymers, such as polyamides (PA), polyolefins, such as polypropylene (PP) or polyethylene (PE), polyacrylates, such as polymethyl methacrylate (PMMA), polycarbonate ( PC), polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyether sulfones (PES), polyether ketones or polyether sulfides (PES), or mixtures thereof in U.S. Pat Generally in proportions of up to a maximum of 30 wt .-%, preferably in the range of 1 to 10 wt .-%, each based on the amount of polymer melt, blended.

 Suitable propellants under normal conditions are gaseous or liquid hydrocarbons which have a boiling point below the softening point of the polymer. Typical representatives of these compounds are propane, butane, pentane, hexane and the isomers of these compounds. Also, water, nitrogen, halogenated blowing agents or carbon dioxide are useful as blowing agents. Furthermore, chemical blowing agents and blowing agents which - thermally or radiation-induced - release volatile components can be used.

 Furthermore, mixtures in the above amounts ranges with z. As hydrophobically modified or functionalized polymers or oligomers, rubbers such as polyacrylates or polydienes, z. As styrene-butadiene block copolymers or biodegradable aliphatic or aliphatic / aromatic copolyesters possible.

 Suitable compatibilizers are e.g. Maleic anhydride-modified

Styrene copolymers, polymers containing epoxy groups or organosilanes.

 As flame retardants in particular halogenated organic compounds having a bromine content greater than 50% by weight are used. Known examples thereof are hexabromocyclododecane, brominated styrene copolymers (for example styrene-butadiene copolymers) or pentabromo- nonchlorocyclohexane. Furthermore, all other halogenated, but also halogen-free flame retardants can be used. Possible representatives of these substances are, for example, red phosphorus, organic phosphorus compounds, e.g. DOP (9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide); DOPS-SH (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-thione or -10-sulfide), organic and inorganic N-compounds (e.g., ammonium polyphosphate), inorganic compounds, e.g. Magnesium hydroxide, aluminum hydroxide, water glass or expanded graphite.

 For the avoidance of doubt, it should be noted that any forms of formation of the novel polymers which may not be mentioned here, the production of the same, and the polymer foam bodies produced from the same arise from the claims.

The invention will now be illustrated, without limiting the inventive concept, by the following examples:

Example 1 :

A styrene polymer (SUNPOR EPS-STD: 6 wt% pentane, chain length Mw = 200,000 g / mol, non-uniformity Mw / Mn = 2.5) was in the catchment area of a Twin-screw extruder 4 wt .-% anthracite (containing 0.5 wt .-% sulfur), and 1, 4 wt.% HBCD, both based on the resulting EPS granules, admixed and the mixture in the extruder at 190 ° C. melted. The polymer melt thus obtained was conveyed through a die plate at a rate of 20 kg / h and granulated with a pressurized underwater granulator to form compact EPS granules.

The resulting granules were coated with customary for this purpose coating materials (glycerol or zinc stearates) to prevent sticking during the foaming and then prefoamed in a batch prefoamer to a density of about 15 kg / m ³ . The cell structure of the foam beads thus obtained was homogeneous. After an intermediate storage of 24 hours, blocks were made. From these blocks molded parts for a fire test according to DIN 4102 were produced.

The moldings produced in this way had a density of 15 kg / m ³ and the class B1 according to DIN 4102 could be achieved.

Example 2:

 The preparation of the granules and the processing into moldings was carried out analogously to Example 1 with the difference that 4 wt .-% petroleum coke (with a content of 1, 2 wt .-% sulfur), and 1, 2 wt.% HBCD were used.

The plates thus produced had a density of 15 kg / m ³ and class B1 according to DIN 4102 could be achieved.

Example 3:

 The preparation of the granules and the processing into moldings was carried out analogously to Example 1 with the difference that 4 wt .-% coal dust (with a content of 4.0 wt .-% sulfur), and 1, 2 wt.% HBCD were used.

The plates thus produced had a density of 15 kg / m ³ and class B1 according to DIN 4102 could be achieved.

Example 4 (comparative example)

 The preparation of the granules and the processing into moldings was carried out analogously to Example 1 with the difference that 4 wt .-% large-crystalline natural graphite (with a content of 0 wt .-% sulfur), and 1, 4 wt .-% HBCD were used.

The plates thus produced had a density of 15 kg / m ³ and class B1 according to DIN 4102 could not be achieved. The carbon solids used in Examples 1 to 4 had a particle size with a d ₅₀ less than 10 pm.

 The moldings produced according to Examples 1 to 3 could reach the thermal conductivity group (WLG) according to DIN 18164 and thus showed in comparison to EPS without these solids (WLG 040) a significantly improved thermal insulation property.

 Surprisingly, no unpleasant odors could be detected on the moldings produced from Examples 1 to 3, in contrast to moldings in which sulfur in the same amounts was subsequently added as external flame retardant synergist.

Claims

claims: 1. Flame-retardant, at least one flame retardant-containing, expandable polymers containing one or more, consisting of more than 70 wt .-% of carbon atoms (s), in particular present in the form of athermanic particles, solid (s), characterized in that this content of sulfur is from 0.2 to 30% by weight, preferably from 0.3 to 15% by weight, preferably from 0.6 to 10% by weight, more preferably from 1, 2 to 7 wt .-%, in the form of sulfur and / or sulfur compounds (have). 2. Polymers according to claim 1, characterized in that at least one of the athermanous particles or carbon solids by natural Kohlenohlungsprozesse in the earth's crust and / or by artificially generated Kohlenohlungsprozesse natural and / or synthetic materials, mainly consisting or formed with or from Carbon atoms, is formed. 3. Polymers according to claim 1 or 2, characterized in that at least one of the athermanic particles or carbon solids meta-anthracite, anthracite, coal coke, green coke, petroleum coke, brown or hard coal is. 4. Polymers according to one of claims 1 to 3, characterized in that the dimensions of the particles of the solid (s) a d ₅₀ from 0.5 to 50 pm, preferably from 1 to 30 pm, more preferably from 1 to 10 pm. 5. Polymers according to one of claims 1 to 4, characterized in that the solid particles are platelet-shaped and have an aspect ratio of 2 to 50. 6. Polymers according to one of claims 1 to 5, characterized in that the melt of the polymer polystyrene and / or cellulose acetate butyrate in a Concentration of more than 50 wt .-% contains. 7. Polymers according to one of claims 1 to 6, characterized in that the flame retardant is an organic halogen compound, preferably having a halogen content of at least 50 wt .-%, or that as a flame retardant, a halogen-free flame retardant, optionally based on at least one phosphorus compound, is included. 8. Polymers according to one of claims 1 to 7, characterized in that at least one thermal radical generator is contained as Flammschutzsynergist. 9. A polymer according to any one of claims 1 to 8, characterized in that in addition infrared-insulating or the thermal insulation properties increasing materials, in particular graphite, electrographite, carbon black, metal oxide, non-metal oxide, metal powder, aluminum powder, carbon (carbon black, Books and Taylor structures containing carbon, carbon fibers, fullerenes), or organic dye, in particular in the form of pigments or mixtures of these materials are incorporated. 10. Polymers according to one of claims 1 to 9, characterized in that at least one blowing agent is contained. 11. A polymer according to any one of claims 1 to 10, characterized in that the / athermanen particles or solids are homogeneously and evenly distributed in the polymer. 12. Polymer foam body, made from expandable polymers according to one of claims 1 to 11. 13. Polymer foam body according to claim 12, characterized in that it reaches the WLG (heat conductivity group) 035, preferably WLG 032, according to DIN 18164. 14. A polymer foam body according to claim 12 or 13 having a density between 7 and 200 g / l and a predominantly closed-cell cell structure with more than 0.5 cells per mm ³ . 15. A process for the preparation of polymers according to any one of claims 1 to 11, characterized in that in the polymer melt as blowing agent, a gaseous or liquid hydrocarbon is introduced, or that a polymer or a polymer melt is used, in which or which such a blowing agent is already introduced. 16. A process for the preparation of flame-retardant expandable styrene polymers (EPS) according to one of claims 1 to 1 1, characterized  that at least one carbon solid and a blowing agent are mixed with a styrene polymer melt by means of a dynamic or static mixer and the mixture is then granulated, or  that at least one carbon solid is added by means of a dynamic or static mixer to still granular polystyrene polymer and then the mixture is melted, and then the melt, in particular with a blowing agent, impregnated and granulated, or  that at least one carbon solid is added by means of a dynamic or static mixer to still granular EPS, and then the mixture is melted and granulated, or  that the granulate preparation is effected by suspension polymerization of styrene in aqueous suspension in the presence of at least one carbon solid and at least one blowing agent, or  that the carbon solid is mixed with a styrene polymer melt by means of a dynamic or static mixer, the mixture is then granulated and impregnated in a further process step with a blowing agent. 17. The method according to claim 16, characterized in that the granules are prepared by means of underwater granulation at a water pressure of greater than 3 bar.