WO2009037236A1

WO2009037236A1 - Flame-retardant polystyrene and impact-modified polystyrene

Info

Publication number: WO2009037236A1
Application number: PCT/EP2008/062270
Authority: WO
Inventors: Christian Schade; Maarten Staal; Piyada Charoensirisomboon
Original assignee: Basf Se
Priority date: 2007-09-18
Filing date: 2008-09-16
Publication date: 2009-03-26

Abstract

The invention relates to thermoplastic molding compositions comprising A) from 55 to 99% by weight of at least one polystyrene (PS), of an impact-modified polystyrene (HIPS), or of a mixture composed of PS and HIPS, B) from 1 to 45% by weight of a flame retardant comprising B1) an expandable graphite, B2) a phosphorus-comprising flame-retardant compound, and B3) a fluorine-comprising polymer, C) from 0 to 20% by weight of a block copolymer based on styrene and butadiene (SBC), and D) from 0 to 40% by weight of further additives, where the percentages by weight are in each case based on the total weight of components A) to D) and give a total of 100% by weight, wherein the average particle size D50 of the expandable graphite B1) is from 10 µm to 1000 µm (measured by the method mentioned in the description), and the proportion by weight of the fluorine-comprising polymer B3), based on the total weight of components A) to D), is from 0.01 to 0.5% by weight, and also to processes for the preparation of molding compositions of this type, to the use of molding compositions of this type for the production of moldings, of fibers, of foams, and of foils, and also to the resultant moldings, fibers, foams, and foils.

Description

Flame retardant polystyrene and impact modified polystyrene

description

The invention relates to thermoplastic molding compositions containing

A) 55 to 99% by weight of at least one polystyrene (PS), an impact-modified polystyrene (HIPS) or a mixture of PS and HIPS,

B) 1 to 45% by weight of a flame retardant containing B1) an expandable graphite,

B2) a phosphorus-containing flame retardant compound and B3) a fluorine-containing polymer,

C) 0 to 20% by weight of a block copolymer based on styrene and butadiene (SBC), and D) 0 to 40% by weight of further additives,

wherein the weight percentages are based on the total weight of components A) to

D) and together give 100% by weight,

Moreover, the present invention relates to processes for the preparation of such molding compositions, the use of such molding compositions for the production of moldings, fibers, foams and films as well as the moldings, fibers, foams and films obtainable in this case.

Expandable graphite, which is also referred to as expandable graphite, as a flame retardant in polystyrene (PS) or impact modified polystyrene (HIPS) use is known for example from WO 03/046071 A1. Moreover, according to this document as a further flame retardant component, a halogen-containing compound in amounts of 2 to 11%, calculated as halogen, is needed. For toxicological reasons, for example, it is desirable to avoid the use of halogenated flame retardants as much as possible.

Halogen-free flame-retardant styrene polymers containing expandable graphite and a phosphorus compound as flame retardant components are disclosed in WO 00/34367 and WO 00/34342. However, molding compositions based on such flame-retardant styrene polymers are in terms of their dripping behavior in case of fire in need of improvement.

WO 2005/103136 discloses flame-retardant styrene polymers which, in addition to expandable graphite and a phosphorus compound, contain a further co-additive which is intended to suppress the migration of the phosphorus-containing flame retardant to the polymer surface. Polycarbonate is explicitly mentioned as a co-additive. KR1996-0001006 discloses flame-retardant polystyrene wherein the flame retardant components include expandable graphite, a phosphorus compound, and Teflon. The mean particle size of the expandable graphite is 5 μm. The teflon added as an anti-dripping agent is used in amounts of from 1 to 5 percent by weight. The halogen-free flameproofed molding compositions obtained in this way have good heat resistance and impact resistance.

Object of the present invention was to find a flame retardant combination for polystyrene and impact modified polystyrene, which has an improved combination of flame retardant and mechanical properties over known systems.

Accordingly, the molding compositions defined above were found, it being essential to the invention that the expandable graphite B1) has an average particle size D50 between 10 μm and 1000 μm (measured by the method described in the example section), and the weight fraction of the fluorine-containing polymer B3) the total weight of components A) to D) is from 0.01 to 0.5% by weight.

The novel molding compositions based on polystyrene and impact-modified polystyrene exhibit. known systems an improved combination of flame retardant and mechanical properties.

The molding compositions according to the invention and the other processes and objects according to the invention are described below.

Contain the molding compositions of the invention

A) 55 to 99 wt .-%, preferably 59.5 to 94.5 wt .-%, particularly preferably 64 to 89 wt .-%, component A,

B) 1 to 45 wt .-%, preferably 5 to 40 wt .-%, particularly preferably 10 to 35 wt .-%, component B,

C) 0 to 20 wt .-%, preferably 0.5 to 15 wt .-%, particularly preferably 1 to 10 wt .-% component C, and D) 0 to 40 wt .-%, preferably 0 to 30 wt. %, more preferably 0 to 25% by weight of component D,

D) and together give 100 wt .-%.

The flame retardant component B) comprises in particular B1) from 20 to 79.99% by weight, preferably from 30 to 69.9% by weight, particularly preferably from 40 to 59.5% by weight, of component B1), B2) from 20 to 79.99% by weight %, preferably 30 to 69.9 wt .-%, particularly preferably 40 to 59.5 wt .-%, of component B2) and B3) 0.01 to 4 wt .-%, preferably 0.1 to 3 wt. -%, more preferably 0.5 to 2

% By weight of component B3),

wherein the weight percentages are based in each case on the total weight of the components B1) to B3) and together give 100% by weight.

It is essential to the invention that the expandable graphite B1) has an average particle size D50 between 10 μm and 1000 μm, preferably between 30 μm and 850 μm, particularly preferably between 200 μm and 700 μm (measured by the method described in the example section), and Polymer B3) based on the total weight of components A) to D) of 0.01 to 0.5 wt .-%, preferably from 0.1 to 0.45 wt .-%, particularly preferably from 0.2 to 0, 4 wt .-%, is.

Component A):

As component A) of the thermoplastic molding compositions it is possible in principle to use all polystyrenes known in the art and described in the literature and impact-modified polystyrenes or mixtures thereof. PS and HIPS and their preparation, structure and properties are described in detail in the literature, for example in A. Echte, F. Haaf, J. Hambrecht, Angew. Chem. (Int Ed. Engl.) 20 (1981) 344-361, or in Kunststoffhandbuch, Vol. 4, polystyrene, Carl Hanser Verlag, 1996.

Suitable PS is prepared by the method of anionic or radical polymerization. The influenceable by the polymerization non-uniformity of the polymer is of secondary importance. PS and HIPS whose toluene-soluble fraction has an average molecular weight Mw of from 50,000 to 500,000 g / mol and which are optionally also provided with additives, such as, for example, mineral oil, stabilizers, antistatic agents or waxes, are preferred.

The impact-resistant polystyrenes used can also be structurally modified by the use of specific polybutadiene rubbers, for example with a 1, 4-cis or 1, 4-trans proportion or 1, 2 and 1, 4 linkage fraction modified compared to conventional rubbers be. Further, instead of polybutadiene rubbers, other diene rubbers and elastomers of the ethylene-propylene-diene copolymer type (diene rubbers) and hydrogenated diene rubbers may also be used. Component B):

The thermoplastic molding compositions contain as component B) according to the invention containing a flame retardant mixture

B1) expandable graphite,

B2) a phosphorus-containing flame retardant compound and

B3) a fluorine-containing polymer.

The molding compositions according to the invention contain as component B1) known to the expert and described in the literature expandable graphite, so-called

Expandable graphite (heat or heat expandable graphite). This is usually derived from natural or artificial graphite.

The expandable graphite is obtainable, for example, by oxidation of natural and / or artificial graphite. As oxidation agents can be H2O2 or nitric acid in

Sulfuric acid can be used.

Furthermore, the expandable graphite may be reduced by reduction, e.g. be prepared with sodium naphthalenide in an aprotic organic solvent.

Due to its layered lattice structure, graphite is able to form special forms of intercalation compounds. In these so-called interstitial compounds are foreign atoms or molecules in z.T. Stoichiometric ratios have been included in the spaces between the carbon atoms.

The surface of the expanded graphite may be better for compatibility. the thermoplastic matrix may be coated with a coating agent, for example with silane sizes known to those skilled in the art.

In the event that the expandable graphite by o.g. Oxidation is obtained, it may be necessary to add an alkaline compound, since the expandable graphite (by containing acid) may otherwise cause corrosion of the molding compositions and / or storage and Herstellapparate such molding compounds. In particular, alkali metal compounds and Mg (OH) 2 or Al hydroxides can be added in amounts of up to 10, preferably up to 5 wt .-% (based on 100 wt .-% B1). The mixture is advantageously carried out before the components are compounded.

The heat expansion of the expandable graphite with rapid heating from room temperature to 800 ^° C. (in the direction of the c-axis of the crystal) is preferably at least 100 ml / g, preferably at least 110 ml / g (so-called specific volume change). Essential for the suitability as a flame retardant is that the expandable graphite does not expand to a greater extent at temperatures below 270 ⁰ C, preferably below 280 ⁰ C. By this the expert understands that the expandable graphite at the temperatures mentioned in a period of 10 min Volume expansion of less than 20% experiences.

The coefficient of expansion (as specific core size) usually means the difference between the specific volume (ml / g) after heating and the specific volume at 20 ^° C. room temperature. This is generally measured by the following method: A quartz vessel is heated to 1000 ⁰ C in an electric melting furnace. 2 g of expandable graphite are quickly added to the quartz container and this 10 sec. Left in the furnace.

The weight of 100 ml of expanded graphite is measured to determine the so-called "loosely apparent specific gravity." The reciprocal then forms the specific volume at that temperature, and the specific volume at room temperature is measured at 20 ° C. (Expansion coefficient = specific volume after heating - specific volume at 20 ° C).

The mean particle size D ₅ o of the expanded graphite should preferably be in the above-mentioned ranges. If the mean particle sizes are lower, as a rule no sufficient flameproofing effect is achieved; If they are larger, usually the mechanical properties of the thermoplastic molding compositions are adversely affected.

The density of the expandable graphite is usually in the range of 0.4 to 2 g / cm ³ .

The phosphorus-containing compounds of component B2) are organic and inorganic phosphorus-containing compounds in which the phosphorus has the valence state -3 to +5. The term "level of oxidation" is understood to mean the term "oxidation state" as used in the textbook of inorganic chemistry by A.F. Hollemann and E. Wiberg, Walter des Gruyter and Co. (1964, 57th to 70th edition), pages 166 to 177, is reproduced. Phosphorus compounds of valence levels -3 to +5 are derived from phosphine (-3), diphosphine (-2), phosphine oxide (-1), elemental phosphorus (+0), hypophosphorous acid (+1), phosphorous acid (+3 ), Hypophosphoric acid (+4) and phosphoric acid (+5).

From the large number of phosphorus compounds suitable as component B2), in particular the inorganic or organic phosphates, phosphites, phosphonates, phosphate esters, red phosphorus and triphenylphosphine oxide, only a few examples are mentioned. Examples of phosphorus compounds of the phosphine class which have the valence state -3 are aromatic phosphines, such as triphenylphosphine, tritolylphosphine, trinonylphosphine, trinaphthylphosphine and trisnonylphenylphosphine, among others. Triphenylphosphine is particularly suitable.

Examples of phosphorus compounds of the diphosphine class which have the valence state -2 are tetraphenyldiphosphine, tetranaphthyldiphosphine and the like. Particularly suitable is tetranaphthyldiphosphine.

Phosphorus compounds of valence state -1 are derived from the phosphine oxide.

Suitable phosphine oxides of the general formula I.

R ¹

wherein R ¹ , R ² and R ³ in formula I mean the same or different alkyl, aryl, alkylaryl or cycloalkyl groups having 8 to 40 carbon atoms.

Examples of phosphine oxides are triphenylphosphine oxide, tritolylphosphine oxide, trisynylphenylphosphine oxide, tricyclohexylphosphine oxide, tris (n-butyl) phosphine oxide, tris (n-hexyl) phosphine oxide, tris (n-octyl) phosphine oxide, tris (cyanoethyl) - phosphine oxide, benzyl bis (cyclohexyl) phosphine oxide, benzyl bisphenyl phosphine oxide, phenyl bis (n-hexyl) phosphine oxide. Also preferred are oxidized reaction products of phosphine with aldehydes, especially from t-butylphosphine with glyoxal. Particular preference is given to using triphenylphosphine oxide, tricyclohexlyphosphine oxide, tris (n-octyl) phosphine oxide and tris (cyanoethyl) phosphine oxide, in particular triphenylphosphine oxide.

Also suitable is triphenylphosphine sulfide and its derivatives of phosphine oxides as described above.

Phosphorus of the valence state +0 is the elemental phosphorus. Eligible are red and black phosphorus. Preference is given to red phosphorus.

Phosphorus compounds of the "oxidation state" +1 are, for example, hypophosphites of purely organic nature, for example organic hypophosphites, such as cellulose hypophosphite esters, esters of hypophosphorous acids with diols, for example of 1,10-dodecyldiol. Also substituted phosphinic acids and their anhydrides, such as diphenylphosphinic can be used. Further suitable are diphenylphosphinic acid, di-p-tolylphosphinic acid, di-cresylphosphinic anhydride, but also compounds such as hydroquinone, ethylene glycol, propylene glycol bis (diphenylphosphinic) - esters, inter alia, in question. Also suitable are aryl (alkyl) phosphinic acid amides, such as, for example, diphenylphosphinic acid dimethylamide and sulfonamidoaryl (alkyl) phosphinic acid derivatives, for example p-tolylsulfonamidodiphenylphosphinic acid. Hydroquinone and ethylene glycol bis (diphenylphosphinic) esters and the bis-diphenylphosphinate of hydroquinone are preferably used.

Phosphorus compounds of the oxidation state +3 are derived from the phosphorous acid. Suitable are cyclic phosphonates derived from pentaerythritol, neopentyl glycol or catechol, e.g. Compounds according to formula II

where R is a Ci to C4 alkyl radical, preferably methyl, x = 0 or 1 (ammonium gard ^® P 45 from Albright & Wilson).

Further, +3 valence phosphorous is in triaryl (alkyl) phosphites, e.g. Triphenyl phosphite, tris (4-decylphenyl) phosphite, tris (2,4-di-tert-butylphenyl) phosphite or phenyldidecyl phosphite and the like. contain. But there are also diphosphites, such. Propylene glycol-1, 2-bis (diphosphite) or cyclic phosphites derived from pentaerythritol, neopentyl glycol or catechol, in question.

Particularly preferred are methyl neopentyl glycol phosphonate and phosphite and dimethyl pentaerythritol diphosphonate and phosphite.

As phosphorus compounds of the oxidation state +4, especially hypodiphosphates, such as. Tetraphenyl hypodiphosphate or Bisneopentylhypodiphosphat into consideration.

Suitable phosphorus compounds of the oxidation state +5 are, in particular, alkyl- and aryl-substituted phosphates. Examples are phenylbisdodecylphosphate, phenylethylhydrogenphosphate, phenylbis (3,5,5-trimethylhexyl) phosphate, ethyldiphenylphosphate, 2-ethylhexyldi (tolyl) phosphate, diphenylhydrogenphosphate, bis (2-ethylhexyl) -p-tolylphosphate, tritolylphosphate, bis (2-ethylhexyl) phenyl phosphate, di (nonyl) phenyl phosphate, phenylmethyl hydrogen phosphate, di (dodecyl) p-tolyl phosphate, p-tolyl bis (2,5,5-trimethylhexyl) phosphate or 2-ethylhexyldiphenyl phosphate. Particularly suitable are phosphorus compounds in which each radical is an aryloxy radical. Especially suitable is triphenyl phosphate and resorcinol bis (diphenyl phosphate) and its nucleus-substituted derivatives of general formula III (RDP):

in which the substituents in formula III have the following meanings:

R ⁴ -R ^{7 is} an aromatic radical having 6 to 20 C atoms, preferably a phenyl radical which may be substituted by alkyl groups having 1 to 4 C atoms, preferably methyl,

R ^{8 is} a divalent phenol radical, preferred

and n an average value between 0.1 to 100, preferably 0.5 to 50, in particular 0.8 to 10 and very particularly 1 to 5.

The commercially available products under the trademark RPD Fyroflex ^® or Fyrol ^® -RDP (Akzo) and CR-S 733 (Daihachi) are due to the manufacturing process, mixtures of about 85% RDP (n = 1) of about 2, 5% triphenyl phosphate and about 12.5% oligomeric portions in which the degree of oligomerization is usually less than 10.

Furthermore, cyclic phosphates can also be used. Particularly suitable here is diphenylpentaerythritol diphosphate and phenylneopentyl phosphate.

In addition to the above-mentioned low molecular weight phosphorus compounds are still oligomeric and polymeric phosphorus compounds in question.

Such polymeric, halogen-free organic phosphorus compounds containing phosphorus in the polymer chain are formed, for example, in the preparation of pentacyclic, unsaturated phosphine dihalides, as described, for example, in DE-A 20 36 173. The molecular weight measured by vapor pressure osmometry in di methylformamide, the Polyphospholinoxide should be in the range of 500 to 7000, preferably in the range of 700 to 2000.

The phosphorus here has the oxidation state -1.

Further, inorganic coordination polymers of aryl (alkyl) phosphinic acids such as e.g. Poly-ß-sodium (l) -methylphenylphosphinat be used. Their preparation is given in DE-A 31 40 520. The phosphorus has the oxidation number +1.

Furthermore, such halogen-free polymeric phosphorus compounds may be prepared by the reaction of a phosphonic acid chloride, such as a phosphonic acid chloride. Phenyl, methyl, propyl, styryl and vinylphosphonic dichloride with bifunctional phenols, e.g. Hydroquinone, resorcinol, 2,3,5-trimethylhydroquinone, bisphenol-A, tetramethylbiphenol-A arise.

Further halogen-free polymeric phosphorus compounds which may be present in the molding compositions according to the invention are prepared by reaction of phosphorus oxytrichloride or phosphoric ester dichlorides with a mixture of mono-, bi- and trifunctional phenols and compounds carrying other hydroxyl groups (see Houben-Weyl-Chem. Müller, Thieme-Verlag Stuttgart, Organic Phosphorus Compounds Part II (1963)). Furthermore, polymeric phosphonates can be prepared by transesterification reactions of phosphonic acid esters with bifunctional phenols (cf., DE-A 29 25 208) or by reactions of phosphonic acid esters with diamines or diamides or hydrazides (cf., US Patent 4,403,075). In question is also the inorganic poly (ammonium phosphate).

It is also possible oligomeric pentaerythritol phosphites, phosphates and phosphonates in accordance with EP-B 8 486, as mobile Antiblaze ^® 19 (registered trademark of Mobil Oil), is used (see formulas IV and V.):

O O

- O-P-R-P-O M.V

R 'K

where the substituents in the formulas IV and V have the following meanings: R ¹ , R ^{2 is} hydrogen, C 1 - to C ₆ -alkyl which optionally contains one hydroxyl group, preferably C 1 - to C ₄ -alkyl, linear or branched, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl; phenyl; wherein preferably at least one radical R ¹ or R ² , in particular R ¹ and R ^{2 is} hydrogen;

R ^{3 is} C 1 -C 4 -alkylene, linear or branched, eg methylene, ethylene, n-

Propylene, iso-propylene, n-butylene, tert-butylene, n-pentylene, n-octylene, n-dodecylene;

Arylene, e.g. Phenylene, naphthylene; Alkylarylene, e.g. Methyl-phenylene, ethyl-phenylene, tert-butyl-phenylene, methyl-naphthylene, ethyl-naphthylene, tert-butyl-naphthylene; Arylalkylene, e.g. Phenylmethylene, phenylethylene, phenylpropylene, phenylbutylene;

M is an alkaline earth, alkali metal, Al, Zn, Fe, boron;

m is an integer of 1 to 3;

n is an integer of 1 and 3 and

x 1 or 2.

Particular preference is given to compounds of the formula IV in which R ¹ and R ^{2 are} hydrogen, where M is preferably Ca, Zn or Al and calcium phosphinate is very particularly preferred as compound.

Such products are commercially available e.g. available as calcium phosphinate.

Suitable salts of the formula IV or V in which only one radical R ¹ or R ^{2 is} hydrogen are, for example, salts of phenylphosphinic acid, their Na and / or Ca salts being preferred.

Further preferred salts have a hydroxyl-containing alkyl radical R ¹ and / or R ² . These are obtainable, for example, by hydroxymethylation. Preferred compounds are Ca, Zn and Al salts.

The mean particle size D ₅ o (measured by the method described in the example section) of component B2) is preferably less than 10 μm, preferably less than 7 μm and in particular less than 5 μm. The Dio value is preferably less than 4 μm, in particular 3 μm and very particularly preferably less than 2 μm. Preferred dgo values are less than 40 μm and in particular less than 30 μm and very particularly preferably less than 20 μm.

Preference is furthermore given to phosphorus compounds of the general formula VI:

where the substituents in formula VI have the following meanings:

R ¹ to R ²⁰ independently of one another hydrogen, a linear or branched alkyl group up to 6 C atoms

an average of 0.5 to 50 and

X is a single bond, C = O, S, SO ₂ , C (CH ₂ ) ₂

Preferred compounds B2) are those of the formula VI in which R ¹ to R ²⁰ independently of one another are hydrogen and / or a methyl radical. In the event that R ¹ to R ²⁰ independently of one another are methyl, such compounds are preferred in which the radicals R ¹ , R ⁵ , R ⁶ , R ¹⁰ , R ¹¹ , R ¹⁵ , R ¹⁶ , R ²⁰ in ortho Position to the oxygen of the phosphate group represent at least one methyl radical. Preference is furthermore given to compounds B2) in which one methyl group is present per aromatic ring, preferably in the ortho position, and the other radicals are hydrogen.

Particular preference is given as substituents SO ₂ and S, and very particularly preferably C (CH ₂ ) ₂ for X in the above formula (VI).

n in the above formula (VI) is preferably 0.5 to 5, in particular 0.7 to 2 and in particular << 1 as the average value.

The indication of n as an average value results from the preparation of the compounds listed above, so that the degree of oligomerization is usually less than 10 and small amounts (usually <5 wt .-%) of triphenyl phosphate are included, this being different from batch to batch. Such compounds B2) are commercially available as CR-741 from Daihachi.

As component B3), the molding compositions contain a fluorine-containing polymer. Preference is given to fluorine-containing ethylene polymers. These are polymers of ethylene with a fluorine content of 55 to 76 wt .-%, preferably 70 to 76 parts by weight.

%.

Examples of these are polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymers or tetrafluoroethylene copolymers with smaller proportions (generally up to 50% by weight) of copolymerizable ethylenically unsaturated monomers. These are e.g. by Schildknecht in "Vinyl and Related Polymers", Wiley-Verlag, 1952, pages 484 to 494 and by Wall in "Fluoropolymers" (Wiley Interscience, 1972).

These fluorine-containing ethylene polymers are homogeneously distributed in the molding compositions and preferably have an average particle size D ₅ o in the range of 0.05 to 10 .mu.m, in particular from 0.1 to 5 .mu.m. These small particle sizes can be achieved particularly preferably by using aqueous dispersions of fluorine-containing ethylene polymers and their incorporation into a polymer melt.

Component C):

As component C), in principle all block copolymers based on styrene and butadiene (SBC) known to the person skilled in the art and described in the literature are suitable. Preference is given to using thermoplastic elastomers based on styrene (S-TPE), in particular those having an elongation at break of more than 300%, particularly preferably more than 500%, in particular more than 500% to 600% (these and all others in this application tensile elongations and tensile strengths are determined in the tensile test according to ISO 527-2: 1996 on test specimens of type 1 BA (Annex A of the cited standard: "small specimens")).

Particularly preferred are mixed as SBC or S-TPE, a linear or star-shaped styrene-butadiene block copolymer with external polystyrene blocks S and, between these, styrene-butadiene copolymer blocks with a random styrene / butadiene distribution (S / B) _ra NDOM or (with a styrene S / B) _tap Erzu (eg Styrolux ^® or especially Styroflex ^® of BASF Aktiengesellschaft, K-Resin ^® of CPC; further components C) are marketed under the brand names Cariflex ^®, Kraton ^®, Tufprene ^®, A- Saflex ^®). The total butadiene content of component C) is preferably in the range from 15 to 50% by weight, more preferably in the range from 25 to 40% by weight, the total styrene content is correspondingly preferably in the range from 50 to 85% by weight, more preferably in the range of 60 to 75 wt .-%.

Preferably, the styrene-butadiene block (S / B) consists of 30 to 75% by weight of styrene and 25 to 70% by weight of butadiene. Particularly preferably, a block (S / B) has a butadiene content of 35 to 70 wt .-% and a styrene content of 30 to 65 wt .-%.

The proportion of polystyrene blocks S is preferably in the range from 5 to 40% by weight, in particular in the range from 25 to 35% by weight, based on the total block copolymer. The proportion of the copolymer blocks S / B is preferably in the range of 60 to 95 wt .-%, in particular in the range of 65 to 75 wt .-%.

Especially preferred are linear styrene-butadiene block copolymers of the general structure S- (S / B) -S lying with one or more, between the two S blocks, a random styrene / butadiene distribution having blocks (S / B) _ra NDOM , Such block copolymers are obtainable by anionic polymerization in a nonpolar solvent with the addition of a polar cosolvent or a potassium salt, as described, for example, in WO 95/35335 and WO 97/40079, respectively.

The vinyl content is understood to be the relative proportion of 1,2-linkages of the diene units, based on the sum of the 1,2-, 1,4-cis and 1,4-trans linkages. The 1,2-vinyl content in the styrene-butadiene copolymer block (S / B) is preferably below 20%, in particular in the range from 10 to 18%, particularly preferably in the range from 12 to 16%.

The unsaturated components, in particular those derived from butadiene, the S-TPE and SBC which can be used as component C) can also be completely or partially hydrogenated. In the case of (partially) hydrogenated components C), the proportion of 1,2-linkages of the diene unit before the hydrogenation step can also be up to 60%.

Component D):

The thermoplastic molding compositions may contain one or more additives other than components A), B) and C) as component D). In principle, all plastic additives known to the person skilled in the art and described in the literature are suitable. Plastic additives for the purposes of the present invention are, for example, stabilizers and antioxidants, agents against heat decomposition and decomposition by ultraviolet light, lubricants and mold release agents, dyes and pigments and plasticizers and fibers, for example glass fibers or carbon fibers. Oxidation retarders and heat stabilizers that can be added to the thermoplastic molding composition according to the invention are, for. B. halides of metals of Group I of the Periodic Table, z. For example, sodium, potassium, lithium halides. Furthermore, zinc fluoride and zinc chloride can be used. Further, sterically hindered phenols, hydroquinones, substituted members of this group, secondary aromatic amines, optionally in conjunction with phosphorus-containing acids or their salts, and mixtures of these compounds, preferably in concentrations up to 1 wt .-%, based on the weight of the thermoplastic molding compositions, can be used.

Examples of UV stabilizers are various substituted resorcinols, salicylates, benzotriazoles and benzophenones, which are generally used in amounts of up to 2 wt .-%, based on the weight of the thermoplastic molding compositions.

Lubricants and mold release agents, which can generally be added in amounts of up to 1% by weight, based on the weight of the thermoplastic molding compositions, are stearic acid, stearyl alcohol, stearic acid alkyl esters and amides and esters of pentaerythritol with long-chain fatty acids. There may also be salts of calcium, zinc or aluminum of stearic acid and dialkyl ketones, eg. B. distearyl ketone used. Zinc, magnesium and calcium stearates and N, N'-ethylene-bis-stearamide are particularly suitable according to the invention.

As glass fibers, it is possible to use in the novel molding materials all glass fibers known to the person skilled in the art and described in the literature (see, for example, Milewski, JV, Katz, HS "Handbook of Reinforcements for Plastics", p. 233 et seq., Van Nostrand Reinholt Company Inc., 1987).

manufacturing:

The thermoplastic molding compositions according to the invention can be prepared by processes known per se, in which mixing the starting components in conventional mixing devices such as screw extruders, Brabender mills or Banbury mills and then extruded. After extrusion, the extrudate can be cooled and comminuted. It is also possible to premix individual components and then to add the remaining starting materials individually and / or likewise mixed. The mixing temperatures are usually 200 to 280 ⁰ C.

According to a preferred procedure, components B) and C) can be premixed in a first step. Preferably, the premixing of the entire component B) with at least part of the component C) in melt on a screw extruder. The premixed components B) and C) can either be formulated and granulated, for example, but they can also be used directly as Melt, for example, on the same extruder, in a subsequent second step with component A) and optionally D) melt blended. This premix of the flame retardant mixture with the block copolymers based on styrene and butadiene (SBC) leads ggü. the simultaneous mixing of all components to improved mechanical properties of the thermoplastic molding compositions according to the invention.

The molding compositions according to the invention are suitable for the production of fibers, films, moldings and foams of any kind. Fibers, films, moldings and foams containing the molding compositions according to the invention can be used, for example, as household articles, electronic components, medical devices, automotive components and building materials.

The invention will be explained in more detail below with reference to examples.

Examples:

measurement methods:

Particle size D ₅ o [μm]: The average particle size and the particle size distribution of the expanded graphite B1) were determined from the integral volume distribution. The mean particle sizes are in all cases the volume average of the particle sizes, as determined by means of laser light diffraction on a Malvern Mastersizer 2000 on dry powder. Laser light diffraction provides the integral distribution of the particle diameter of a sample. From this it can be seen how many percent of the particles have a diameter equal to or smaller than a certain size. The average particle diameter, which is also referred to as the D ₅ o value of the integral volume distribution, is defined as the particle diameter at which 50% by weight of the particles have a smaller diameter than the diameter corresponding to the D ₅ o value , Likewise, then 50 wt .-% of the particles have a larger diameter than the D ₅ o value.

Notched impact strength ak [kJ / m ² ]:

The notched impact strength ak was determined according to ISO 179 IeA (F) at 23 ° C.

Young's modulus [MPa]: The stiffness as modulus of elasticity (modulus of elasticity) was determined in the tensile test at a tensile speed of 1 mm / min at 23 ° C according to ISO 527.

Flowability MVR [ml / 10 min]: The melt volume rate MVR 200/5 according to DIN EN ISO 1133 was determined as a measure of the flowability.

Viscosity number VN [ml / g]:

The viscosity number VN was determined at 23 ⁰ C using a solution of 0.5% by weight solution of the polymer in dimethylformamide JE weiligen according to DIN 53,726th

Afterburning times t1 and t2 [s]:

In the fire test based on UL 94, vertical burning standard, the first afterburning time t1 was measured on bars with a thickness of 1.6 mm after a first flame duration of 10 seconds and the second afterburning time t2 was measured immediately after a second flame duration of 10 seconds ,

Heat resistance, Vicat B, [ ⁰ C]:

The heat resistance was determined as Vicat softening temperature on standard small bars at a heating rate of 50 K / hour and a force of 49.05 N according to DIN 53460, method B.

feedstocks

Components or experiments preceded by "V-" are not inventive and are for comparison.

PS or H I PS component A):

The following components A were used: a-l: an impact-modified polystyrene (HIPS) having a polybutadiene content of 7.7% by weight, a flowability MVR of 9.4 ml / 10 min and a heat deflection temperature of 88 ° C.

Flame retardant component B): As component B1) was used:

b1-l: expanded graphite Nord- ^Min® 503 from Nordmann, Rassmann, GmbH, containing 8 wt .-% sulfuric acid, with a mean particle size D ₅ o of 465 microns, a free expansion (starting at about 300 ⁰ C) of at least 150 ml / g and a bulk density of 0.5 g / ml at 20 ^° C.

As component B2) was used:

b2-l: Disflammol ^® TP, a triphenyl Lanxess Aktiengesellschaft.

As component B3) was used:

b3-l: polytetrafluoroethylene PTFE TE-3893, ^Teflon® dispersion from the company CH Erbslöh.

Preparation of the molding compositions and moldings:

The components A) to D) (respective parts by weight of s. Table 1) were in a Zweischnecke- extruder ZSK30 of Fa for determining the products listed in Table 1 mechanical properties. Werner & Pfleiderer injection molded at 220 ⁰ C homogenized and standard moldings.

To determine the fire properties listed in Table 1, the components A) to D) (respective parts by weight see Table 1) were homogenized on a DSM Midiextruder and with an injection molding attachment at 220 ° C melt temperature and 60 ° C mold surface temperature to test specimens according to UL 94, vertical burning standard, extruded with a thickness of 1, 6 mm.

Table 1: Composition and properties of the molding compositions (prefixed V: for comparison, nb: not determined)

calculated as a solid

Average of 10 individual measurements

The examples show that the molding compositions according to the invention based on polystyrene and impact-modified polystyrene compared to. known systems have an improved combination of flame retardant and mechanical properties.

Claims

claims

1. Thermoplastic molding compositions containing

B) 1 to 45 wt .-% of a flame retardant containing

B1) an expandable graphite,

C) 0 to 20 wt .-% of a block copolymer based on styrene and butadiene (SBC), and

D) 0 to 40% by weight of further additives,

where the weight percentages are based on the total weight of the components

A) to D) and together give 100% by weight,

characterized in that the expandable graphite B1) has an average particle size D ₅ O between 10 μm and 1000 μm (measured according to the method mentioned in the description), and

the proportion by weight of the fluorine-containing polymer B3) based on the total weight of components A) to D) is from 0.01 to 0.5% by weight.

2. Thermoplastic molding compositions according to claim 1 containing

59.5 to 94.5 wt .-% of component A), 5 to 40 wt .-% of component B), 0.5 to 15 wt .-% of component C) and 0 to 30 wt .-% of the component D)

wherein the weight percentages are based on the total weight of components A) to D) and together give 100 wt .-%.

3. Thermoplastic molding compositions according to claims 1 or 2 comprising,

From 20 to 79.99% by weight of component B1), from 20 to 79.99% by weight of component B2) and from 0.01 to 4% by weight of component B3),

4. Thermoplastic molding compositions according to claims 1 to 3, comprising as component B2) at least one compound selected from inorganic or organic phosphates, phosphites, phosphonates, phosphate esters, tern phosphorus and triphenylphosphine oxide.

5. Thermoplastic molding compositions according to claims 1 to 4, comprising as component B3) a fluorinated ethylene polymer.

6. Thermoplastic molding compositions according to claims 1 to 5, comprising as component C) a thermoplastic elastomer based on styrene (S-TPE).

7. A process for the preparation of the thermoplastic molding compositions according to claims 2 to 6, characterized in that in a first step, the components B) and C) are premixed, and in a subsequent second step, this premix with component A) is melt blended.

8. Use of the thermoplastic molding compositions according to claims 1 to 6 for the production of fibers, films, moldings and foams.

9. fibers, films, moldings and foams obtainable from the thermoplastic molding compositions according to claims 1 to 6.