EP2307497A1

EP2307497A1 - Expandable thermoplastic polymer blend

Info

Publication number: EP2307497A1
Application number: EP09781151A
Authority: EP
Inventors: Carsten Schips; Klaus Hahn; Konrad Knoll; Holger Ruckdaeschel; Jens Assmann; Helmut Winterling
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2008-07-29
Filing date: 2009-07-28
Publication date: 2011-04-13
Also published as: JP5726735B2; WO2010012702A1; JP2011529514A; KR20110043723A

Abstract

The invention relates to an expandable thermoplastic polymer blend based on a polystyrene, on an elastic block copolymer and on a polyphenylene ether.

Description

Expandable thermoplastic polymer blend

description

The invention relates to an expandable thermoplastic polymer blend, to granules obtainable from the polymer blend, to a process for the preparation of the polymer blend and to foams.

Processes for the preparation of expandable styrene polymers such as expandable polystyrene (EPS) by suspension polymerization have been known for a long time. These methods have the disadvantage that large amounts of wastewater accumulate and must be disposed of. The polymers must be dried to remove internal water. In addition, the suspension polymerization usually leads to broad bead size distributions, which must be sieved consuming into various bead fractions.

Furthermore, expanded and expandable styrene polymers can be prepared by means of extrusion processes. Here, the propellant is e.g. is mixed into the polymer melt via an extruder, conveyed through a die plate and granulated to particle strands or strands (US-A-3,817,669, GB-A-1, 062,307, EP-B 0 126 459, US-A-5,000,891).

EP-A 668 139 describes a process for the production of expandable polystyrene granules (EPS) wherein the propellant-containing melt is produced by means of static mixing elements in a dispersing, holding and cooling step and then granulated. Due to the cooling of the melt to a few degrees above the solidification temperature, the removal of high amounts of heat is necessary.

In order to substantially prevent foaming after extrusion, various methods have been proposed for granulation, such as underwater granulation (EP-A 305 862), spray (WO 03/053651) or atomization (US Pat. No. 6,093,750).

In order to achieve optimum insulating properties and good surfaces of the foam body, the cell number and foam structure which occurs during expansion of the expandable styrene polymers (EPS) is of crucial importance. The EPS granules produced by extrusion often can not be foamed to form foams with optimum foam structure.

Expandable, rubber-modified styrene polymers for elastic polystyrene foams are described, for example, in WO 94/25516, EP-A 682 077, DE-A 197 10 442 and EP-A 0 872 513. In WO 2005/06652 are particle foam moldings having a density of 10 to 100 g / l, by welding prefoamed foam particles of expandable thermoplastic polymer granules containing 5 to 100 wt .-% of a styrene copolymer A), 0 to 95 parts by weight. % Polystyrene B) and 0 to 95% by weight of a thermoplastic polymer C) other than A) and B), and processes for producing the expandable thermoplastic polymer granules. As styrene copolymer A), for example, styrene-acrylonitrile copolymers (SAN) are described.

In the case of the known blend systems, only higher density foams are generally obtained at a higher content of rubber-modified styrene polymers. The object of the invention was to provide even with such blends low density foams with good accessibility and processability.

It has now been found that particle foams and moldings produced therefrom with particularly favorable properties are obtained when the underlying expandable, thermoplastic polymer granules comprise a polyphenylene ether.

The invention is an expandable thermoplastic polymer blend containing

a polystyrene P1

an elastic block copolymer P2 of at least one vinylaromatic

Monomers and at least one diene monomer

a polyphenylene ether P3 optionally as a compound together with a foamable polystyrene, wherein the component P2 to more than 4.5 wt .-%, based on the sum of P1, P2 and P3 is included.

The invention furthermore relates to polymer granules which are obtainable from the polymer blends according to the invention and to the use of the corresponding polymer granules for the production of particle foams and particle foam moldings.

Particulate foam moldings according to the invention have high solvent resistance, good temperature resistance, high mechanical rigidity, good propellant retention and good processability.

In a preferred embodiment, more than 4.5% by weight P2 are contained in the polymer blend based on the sum of P1, P2 and P3. In a particularly preferred Embodiment are contained in the polymer blend based on the sum of P1, P2 and P3:

93 to 41 wt .-% P1 5 to 45 wt .-% P2, in particular at least 5, preferably at least 10 wt .-% 2 to 14 wt .-% P3.

As the polystyrene P1, radically polymerized glassy polystyrene (GPPS), impact modified polystyrene (HIPS), anionically polymerized polystyrene (A-PS) or, for example, anionic polymerized impact polystyrene (A-IPS) can be used.

In a particularly preferred embodiment, for example GPPS or an impact-modified polystyrene (HIPS) or a mixture of GPPS and HIPS can be used.

The elastic block copolymer P2 preferably contains at least one copolymerized units of a vinylaromatic monomer-containing, hard phase-forming block A and / or diene monomer-forming block B and at least one polymerized unit forming rubber-elastic (soft) phase a vinyl aromatic monomer and a diene-containing elastomeric, forming a soft phase block B / A, wherein the glass transition temperature Tg of the block A is above 25 ⁰ C and that of the blocks B and B / A below 25 ⁰ C and the phase volume ratio of block A to block B / A is selected so that the proportion of the hard phase in the total block copolymer 1-40% by volume and the proportion by weight of the diene is less than 50 wt .-%. Suitable block copolymers are, for. As described in WO-A-95/35335.

Such a rubber-elastic block copolymer is obtained by forming, within the above parameters, the soft phase from a random copolymer of a vinyl aromatic with a diene; Statistical Copolymerisa- te of vinyl aromatics and dienes is obtained by polymerization in the presence of a polar cosolvent.

A preferred block copolymer may, for. B. represented by one of the general formulas 1 to 11:

(1) (AB / A) n; (2) (AB / A) nA; (3) B / A (AB / A) n; (4) X - [(AB / A) n] m + I; (5) X - [(B / AA) n] m + I; (6) X - [(AB / A) n A] m + I; (7) X - [(B / AA) n B / A] m + I; (8) Y - [(AB / A) n] m + I; (9) Y - [(B / A-A) n] m + I; (10) Y - [(AB / A) n A] m + I; (11) Y - [(B / AA) n B / A] m + I; in which A for the vinyl aromatic block and

B / A stands for the soft phase, ie the block statistically composed of diene and vinylaromatic units,

X is the residue of an n-functional initiator,

Y is the residue of an m-functional coupling agent and

m and n mean natural numbers from 1 to 10.

Preference is given to a block copolymer of one of the general formulas AB / AA, X - [- B / A - A] 2 and Y - [- B / AA] 2 (meaning the abbreviations as above) and particularly preferably a block copolymer whose soft phase is divided into blocks (12) (B / A) 1- (B / A) 2; (13) (B / A) 1- (B / A) 2- (B / A) 1 or (14) (B / A) 1- (B / A) 2- (B / A) 3, the vinylaro - mat / diene ratio in the individual blocks B / A is different or continuously changes within a block in the limits (B / A) 1 (B / A) 2, the glass transition temperature Tg of each sub-block is below 250 ⁰ C.

A block copolymer comprising several blocks B / A and / or A of different molecular weights per molecule is also preferred.

It is also possible for a block B to be replaced by a block A, which is made up exclusively of vinylaromatic units, since, overall, all that matters is that a rubber-elastic block copolymer is formed. Such copolymers may, for. Have the structure (15) to (18) (15) B- (B / A); (16) (B / A) -B- (B / A); (17) (B / A) 1-B- (B / A) 2; (18) B- (B / A) 1- (B / A). 2

Preferred as a vinyl aromatic compound in the context of the invention are styrene and also α-methylstyrene and vinyltoluene and mixtures of these compounds. Preferred dienes are butadiene and isoprene, furthermore piperylene, 1-phenylbutadiene and mixtures of these compounds.

A particularly preferred monomer combination is butadiene and styrene. All of the following weights and volumes refer to this combination; if the technical equivalents of styrene and butadiene are used, it may be necessary to convert the information accordingly.

The B / A block is built up from about 75-30% by weight of styrene and 25-70% by weight of butadiene. More preferably, a soft block has a butadiene content of between 35 and 70% and a styrene content of between 65 and 30%. The proportion by weight of the diene in the entire block copolymer in the case of the monomer combination styrene / butadiene is 15-65% by weight, that of the vinylaromatic component corresponding to 85-35% by weight. Particular preference is given to butadiene-styrene block copolymers having a monomer composition of 25-60% by weight of diene and 75-40% by weight of vinylaromatic compound.

Preferably, the block copolymers are prepared by anionic polymerization in a nonpolar solvent with the addition of a polar cosolvent. The solvents used are preferably aliphatic hydrocarbons such as cyclohexane or methylcyclohexane.

As Lewis bases polar aprotic compounds such as ethers and tertiary amines are preferred. Examples of particularly effective ethers are tetrahydrofuran and aliphatic polyethers such as diethylene glycol dimethyl ether. As tert. Amines are tributylamine and pyridine. The polar cosolvent is added to the nonpolar solvent in a small amount, e.g. B. from 0.5 to 5 vol% added. Tetrahydrofuran is particularly preferred in an amount of 0.1-0.3% by volume. Experience has shown that in most cases an amount of about 0.2% by volume is sufficient.

The dosage and structure of the Lewis base determine the copolymerization parameters and the proportion of 1, 2 or 1, 4 linkages of the diene units. The polymers have z. Example, a proportion of 15-40% of 1, 2-linkages and 85 - 60% of 1, 4-linkages based on all diene units.

The anionic polymerization is preferably initiated by means of organometallic compounds. Preference is given to compounds of the alkali metals, in particular of lithium. Examples of initiators are methyllithium, ethyllithium, propyllithium, n-butyllithium, sec. Butyllithium and tert. Butyl lithium. The organometallic compound is added as a solution in a chemically inert (inert) hydrocarbon. The dosage depends on the desired molecular weight of the polymer, but is usually in the range of 0.002 to 5 mol%, based on the monomers.

The polymerization temperature can be between 0 ⁰ C and 130 ⁰ C.

The temperature range is preferably between 30 ^° C. and 100 ^° C.

For the mechanical properties, the volume fraction of the soft phase in the solid is of crucial importance. Preferably, the volume fraction of the soft phase built up from diene and vinylaromatic sequences is 60-95, preferably 70-90 and particularly preferably 80-90% by volume. The blocks A formed from the vinylaromatic monomers form the hard phase, the volume fraction corresponding to 5-40, preferably 10-30 and particularly preferably 10-20% by volume.

The volume fraction of the two phases can be measured by contrasted electron microscopy or solid-state NMR spectroscopy.

The proportion of vinyl aromatic blocks can be determined after osmium degradation of the polydiene fraction by precipitation and precipitation.

The future phase ratio of a polymer can also be calculated from the monomer amounts used, if it is allowed to fully polymerize each time. For the purposes of the invention, the block copolymer is uniquely defined by the quotient of the volume fraction in percent of the soft phase formed from the B / A blocks and the proportion of diene units in the soft phase which is between 25 and 70% by weight for the combination styrene / butadiene. % lies.

The static incorporation of the vinyl aromatic compounds into the soft block of the block copolymer and the use of Lewis bases during the polymerization influences the glass transition temperature (Tg). A glass transition temperature between -50 ⁰ C and + 250 ° C, preferably from -50 ⁰ C to + 50 ° C is typical.

The molecular weight of the block A is i. a. between 1000 to 200,000, preferably between 3,000 and 80,000 [g / mol]. Within a molecule, A blocks can have different molecular weights.

The molecular weight of the block B / A is usually between 2,000 and 250,000 [g / mol], preferably between 5,000 and 150,000 [g / mol].

Like block A, block B / A can also assume different molecular weight values within a molecule.

Preferred polymer structures are AB / AA, X - [- B / AA] 2 and Y - [- B / AA] 2, where the random block B / A itself is again divided into blocks B1 / A1-B2 / A2-B3 / A3- ... can be divided. The statistical block preferably consists of 2 to 15 statistical sub-blocks, more preferably 3 to 10 sub-blocks. The division of the statistical block B / A into as many sub-blocks Bn / An offers the decisive advantage that even in the case of a composition gradient within a sub-block Bn / An, which is difficult to avoid under practical conditions in anionic polymerization. (see below), the overall B / A block behaves like a nearly perfect random polymer. It is therefore advisable to add less than the theoretical amount of Lewis base, which increases the proportion of 1, 4-diene linkages, lowers the glass transition temperature Tg and reduces the tendency of the polymer to cure. A larger or a smaller proportion of the sub-blocks can be equipped with a high diene content.

Preferably, the diene occupies a weight fraction of 25% to 70% relative to the total mass, including vinylaromatic compound. Subsequently, block A can be polymerized by adding the vinyl aromatic. Instead, required polymer blocks can also be linked together by the coupling reaction. In the case of bifunctional initiation, the B / A block is first established followed by the A block.

The polyphenylene ethers P3 used generally have a molecular weight (weight average M _w ) in the range from 10,000 to 80,000 g / mol, preferably from 20,000 to 60,000 g / mol. This corresponds to a reduced specific viscosity (i "| _r ed) of 0.2 to 0.9 dl / g, preferably of 0.35 to 0.8 and in particular from 0.45 to 0.6, measured in 0.5 % by weight solution in chloroform at 25 ° C. according to DIN 53 726. A particularly suitable material system is the product Noryl 8890C marketed by GE Plastics (SABIC).

Particularly preferred polyphenylene ethers have recurring units of the formula

(-Ar-R ₁ R ₂ R ₃ R ₄ -O-)

in which mean

Ar is an aryl radical

R 1, R ₂ , R ₃ and R ₄ are each independently monovalent substituents, in particular hydrogen, halide, in particular chlorine and bromine, alkyl, in particular straight-chain alkyl groups having 1 to 18 C atoms, for example methyl, ethyl, lauryl, stearyl; Alkoxy, in particular methoxy and ethoxy

Both homopolymers with a single recurring unit of the formula given above and copolymers by combining two or more recurring units can be used. Suitable polyphenylene ethers are preferably prepared by oxidative coupling of o-position disubstituted phenols. As examples of substituents are halogen atoms such as chlorine or bromine and alkyl radicals having 1 to 4 carbon atoms, which preferably do not have an alpha-terminal tertiary hydrogen atom, for. For example, methyl, ethyl, propyl or butyl radicals. The alkyl radicals may in turn be substituted by halogen atoms such as chlorine or bromine or by a hydroxyl group. Further examples of possible substituents are alkoxy radicals, preferably having up to 4 carbon atoms or phenyl radicals optionally substituted by halogen atoms and / or alkyl groups. Also suitable are copolymers of various phenols such. B. Copolymers of 2,6-dimethylphenol and 2,3,6-trimethylphenol. Of course, mixtures of different polyphenylene ethers can be used.

Preferably, such polyphenylene ethers are used which are compatible with vinyl aromatic polymers, i. H. wholly or largely soluble in these polymers (see A. Noshay, Block Copolymers, pp. 8-10, Academic Press, 1977 and O. Olabisi, Polymer-Polymer Miscibility, 1979, p.117-189).

Examples of polyphenylene ethers are poly (2,6-dilauryl-1,4-phenylene ether), poly (2,6-diphenyl-1,4-phenylene ether), P o I y (2, 6-dimethoxy-1, 4-phenylene ether ), Poly (2,6-diethoxy-1,4-phenylene ether), poly (2-methoxy-6-ethoxy-1,4-phenylene ether), poly (2-ethyl-6-stearyloxy-1,4-phenylene ether) , Poly (2,6-di-chloro-1, 4-phenylene ether), poly (2-methyl-6-phenyl-1, 4-phenylene ether, poly (2,6-dibenzyl-1, 4-phenylene) ether , Poly (2-ethoxy-1,4-phenylene ether), poly (2-chloro-1,4-phenylene ether), poly (2,5-dibromo-1,4-phenylene ether). Polyphenylene ethers are preferably used in which the substituents are alkyl radicals having 1 to 4 carbon atoms, such as poly (2,6-dimethyl-1, 4-phenylene ether), poly (2,6-diethyl-1,4-phenylene ether), poly (2-methyl-6 -ethyl-1, 4-phenylene ether), poly (2-methyl-6-propyl-1,4-phenylene ether), poly (2,6-di-propyl-1,4-phenylene ether) and poly (2-ethyl- 6-propyl-1,4-phenylene ether).

In addition to homopolymers by reaction of a single phenol, copolymers can be prepared by the reaction of two or more different phenols. PPE copolymers can be prepared from any of the above polyphenylene ethers by the addition of trialkylphenols such as 2,3,6-trimethylphenol. Furthermore, graft copolymers of polyphenylene ether and vinylaromatic polymers such as styrene, α-methylstyrene, vinyltoluene and chlorostyrene are suitable.

In addition to the polymers P1 and P2, it is also possible for at least one polymer P4 different from P1 and P2 to be present. As polymer P4 z. Acrylonitrile-styrene-acrylic esters (ASA), polyamide (PA), polyolefins such as polypropylene (PP) or polyethylenes (PE), polyacrylates such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyesters such as polyethylene terephthalate (PET ) or polybutylene terephthalate (PBT), lyethersulfone (PES), polyether ketones (PEK) or polyether sulfides (PES) or mixtures thereof. Preference is given to polyamide (PA).

In a particularly preferred embodiment, the polymer blend contains one or more blowing agents in a homogeneous distribution in a proportion of 2 to 12 wt .-%, preferably 3 to 9 wt .-%, based on the blowing agent-containing polymer melt. Suitable blowing agents are the physical blowing agents commonly used in EPS, such as aliphatic hydrocarbons having 2 to 7 carbon atoms, alcohols, ketones, ethers, esters or halogenated hydrocarbons. Preference is given to using isobutane, n-butane, isopentane, n-pentane. Ethane, acetone, methylal (dimethoxymethane) and methyl formate are preferred as co-propellants.

The invention further relates to a process for the preparation of polymer blends by a) mixing the components P1, P2 and P3 b) melting, preferably in an extruder c) degassing d) optionally mixing in a blowing agent and optionally additives e) cooling f) discharge through a G. Granulating, preferably through a 0.65 mm perforated plate in an underwater bath at 10-15 bar underwater pressure.

To prepare the expandable polymer granules according to the invention, the blowing agent is mixed into the polymer melt. The process comprises the stages a) melt production, b) mixing c) cooling d) conveying and e) granulation. Each of these stages can be carried out by the apparatuses or apparatus combinations known in plastics processing. For mixing, static or dynamic mixers are suitable, for example extruders. The polymer melt can be taken directly from a polymerization reactor or produced directly in the mixing extruder or a separate melt extruder by melting polymer granules. The cooling of the melt can be done in the mixing units or in separate coolers. For example, the pressurized underwater granulation, granulation with rotating knives and cooling by spray misting of tempering liquids or sputtering granulation are suitable for the granulation. For carrying out the method suitable apparatus arrangements are for. B .:

a) Polymerization Reactor - Static Mixer / Cooler Granulator b) Polymerization Reactor - Extruder - Granulator c) Extruder - Static Mixer - Granulator d) Extruder - Granulator Furthermore, the arrangement page extruder for the introduction of additives, for. B. of solids or thermally sensitive additives. The propellant-containing polymer melt is usually supported at a temperature in the range of 140 to 300 ⁰ C, preferably in the range of 160 to 240 ⁰ C plate through the nozzle. Cooling down to the range of the glass transition temperature is not necessary.

The nozzle plate is heated at least to the temperature of the propellant-containing polymer melt. Preferably, the temperature of the nozzle plate is in the range of 20 to 100 ⁰ C above the temperature of the propellant-containing polymer melt. This prevents polymer deposits in the nozzles and ensures trouble-free granulation.

In order to obtain marketable granule sizes, the diameter (D) of the nozzle bores at the nozzle exit should be in the range of 0.2 to 1.5 mm, preferably in the range of 0.3 to 1.2 mm, particularly preferably in the range of 0.3 to 0.8 mm. Thus, even after strand expansion granulate sizes under 2 mm, in particular in the range 0.4 to 1, 4 mm set specifically.

The strand expansion can be influenced by the geometry of the die, apart from the molecular weight distribution. The nozzle plate preferably has bores with a ratio L / D of at least 2, the length (L) designating the nozzle region whose diameter corresponds at most to the diameter (D) at the nozzle exit. Preferably, the ratio L / D is in the range of 3 to 20.

In general, the diameter (E) of the holes at the nozzle inlet of the nozzle plate should be at least twice as large as the diameter (D) at the nozzle outlet.

An embodiment of the nozzle plate has bores with conical inlet and an inlet angle α less than 180 °, preferably in the range of 30 to 120 °. In a further embodiment, the nozzle plate has bores with conical outlet and an outlet angle ß smaller than 90 °, preferably in the range of 15 to 45 °. In order to produce targeted granule size distributions of the styrene polymers, the nozzle plate can be equipped with bores of different exit diameter (D). The various embodiments of the nozzle geometry can also be combined.

To improve the processability, the finished expandable polymer granules can be coated by glycerol esters, antistatic agents or anticaking agents. To improve the foamability, finely divided internal water droplets can be introduced into the polymer matrix. This can be done for example by the addition of water in the molten polymer matrix. The addition of the water can be done locally before, with or after the propellant dosage. A homogeneous distribution of the water can be achieved by means of dynamic or static mixers.

As a rule, from 0 to 2, preferably from 0.05 to 1.5,% by weight of water, based on the total polymer component, is sufficient.

Expandable polymer granules containing at least 90% of the internal water in the form of

Inner water droplets with a diameter in the range of 0.5 to 15 microns form during foaming foams with sufficient cell count and homogeneous foam structure.

The added amount of blowing agent and water is chosen so that the expandable polymer granules have an expansion capacity α, defined as bulk density before foaming / bulk density, after foaming at most 125, preferably 25 to 100.

The expandable polymer granules according to the invention generally have one

Bulk density of at most 700 g / l preferably in the range of 590 to 660 g / l. When using fillers, depending on the type and amount of the filler, bulk densities in the range of 590 to 1200 g / l may occur.

Further, the polymer melt may contain additives, nucleating agents, fillers, plasticizers, flame retardants, soluble and insoluble inorganic and / or organic dyes and pigments, e.g. IR absorbers such as carbon black, graphite or aluminum powder together or spatially separated, e.g. be added via mixer or side extruder.

In a preferred embodiment, the dyes and pigments are added in amounts ranging from 0.01 to 30, preferably in the range of 1 to 5 wt .-%. For the homogeneous and microdispersed distribution of the pigments in the styrene polymer, it may be expedient, in particular in the case of polar pigments, to use a dispersing assistant, eg. B organosilanes, epoxy group-containing polymers or maleic anhydride grafted styrene polymers to use. Preferred plasticizers are mineral oils, low molecular weight styrene polymers, phthalates, which can be used in amounts of 0.05 to 10 wt .-%, based on the styrene polymer.

The expandable, thermoplastic polymer granules according to the invention are prefoamed in a first step preferably by means of hot air or steam to foam particles having a density in the range of 10 to 250 g / l and in a second step in a closed mold welded to the particle foam moldings according to the invention.

The invention is explained in more detail by the examples, without thereby limiting them.

Examples:

As starting materials were selected:

Component A: Polyphenylene Ether Noryl 8890C (GE Plastics)

Component B1: Impact-modified polystyrene (HIPS) 486 M (BASF SE),

Mw / Mn = 3.31, molecular weight 195,000

Component B2: polystyrene (GPPS), molecular weight 261,000 Mw / Mn = 3.46 Component C: elastic block copolymer based on butadiene / styrene,

Molecular weight 130,000; Mw / Mn = 1, 3, composition 35%

Butadiene / 65% polystyrene pentane S 20% iso-pentane, 80% by weight n-pentane

example 1

In a twin-screw extruder from Leistritz ZSK 18, 12.5 wt .-% component C with 80.1 wt .-% component B1 at 220 - 240 ⁰ C melted. Subsequently, the polymer melt was loaded with 5.6 wt .-% pentane S, based on the polymer matrix. Thereafter, the polymer melt was homogenized in two static mixers and cooled to 180 ⁰ C. 1, 7 wt .-% talc (HP 320, Omyarbarb), based on the polymer matrix, as nucleating agent in the form of a batch was added to the propellant-laden main melt stream via a side extruder. After homogenization by means of two further static mixers, the melt was extruded through a heated perforated plate (4 holes with 0.65 mm bore and 280 ^° C. perforated plate temperature). The polymer strand was chopped off by means Unterwassergra- nulierung (12 bar water pressure, water temperature 45 ⁰ C), so that a blowing agent minipellets laden with narrow particle size distribution (d '= 1, 2 mm) was obtained.

Example 2

In a twin-screw extruder from Leistritz ZSK 18, 12.5 wt .-% component C with 80.1 wt .-% component B2 at 220 - 240 ⁰ C melted. Subsequently, the polymer melt was loaded with 5.6 wt .-% pentane S, based on the polymer matrix. Thereafter, the polymer melt was homogenized in two static mixers and cooled to 180 ⁰ C. 1.7% by weight talcum (HP 320, Omya) was added to the propellant-laden main melt stream via a side extruder. Carb), based on the polymer matrix, added as a nucleating agent in the form of a batch. After homogenization by means of two further static mixers, the melt was extruded through a heated perforated plate (4 holes with 0.65 mm bore and 280 ^° C. perforated plate temperature). The polymer strand was chopped off by means Unterwassergra- nulierung (12 bar water pressure, water temperature 45 ⁰ C), so that a blowing agent minipellets laden with narrow particle size distribution (d '= 1, 2 mm) was obtained.

Example 3

In a twin-screw extruder from Leistritz ZSK 18 were 20.6 wt .-% component C with 72.0 wt .-% component B2 at 220 - 240 ⁰ C melted. Subsequently, the polymer melt was loaded with 5.6 wt .-% pentane S, based on the polymer matrix. Thereafter, the polymer melt was homogenized and mixers in two static micro cooled to 180 ⁰ C. 1, 7 wt .-% talc (HP 320, Omyarbarb), based on the polymer matrix, as nucleating agent in the form of a batch was added to the propellant-laden main melt stream via a side extruder. After homogenization by means of two further static mixers, the melt was extruded through a heated perforated plate (4 holes with 0.65 mm bore and 280 ^° C. perforated plate temperature). The polymer strand was chopped off by means Unterwassergra- nulierung (12 bar water pressure, water temperature 45 ⁰ C), so that a blowing agent minipellets laden with narrow particle size distribution (d '= 1, 2 mm) was obtained.

Example 4

In a twin-screw extruder from Leistritz ZSK 18, 20.6% by weight of component C were mixed with 72.0% by weight of polystyrene batch, 3.9% by weight of component A and 68.1% by weight of component B2 at 220 ° C. - 240 ⁰ C melted. Subsequently, the polymer melt was loaded with 5.6 wt .-% pentane S, based on the polymer matrix. Thereafter, the polymer melt was homogenized in two static mixers and cooled to 180 ⁰ C. 1, 7 wt .-% talc (HP 320, Omyacarb), based on the polymer matrix, as a nucleating agent in the form of a batch was added to the propellant-laden main melt stream via a side extruder. After homogenization by means of two further static mixers, the melt was extruded through a heated perforated plate (4 holes with 0.65 mm bore and 280 ^° C. perforated plate temperature). The polymer strand was chopped off by means of underwater pelletization (underwater pressure = 12 bar, water temperature 45 ⁰ C), so that a blowing agent minipellets laden with narrow particle size distribution (d '= 1, 2 mm) was obtained. Starting from the minigranules obtained according to Examples 1 to 4, foams were produced as described below: By prefoaming the particle granules at densities of from 35 to 20 g / l at a pressure of 0.1 bar and, after 12-24 hours of intermediate storage time at a pressure of 1.0 bar, in the automatic molding machine, they were filled with foam into test plates.

The foams obtained in this way have the following properties:

example table

From the comparison of the foam 4 according to the invention with the foams 1 to 3 it can be seen that the invention makes it possible to achieve low foam densities with a high proportion of the elastomer component C.

Claims

claims

1. Expandable thermoplastic polymer blend containing

a polystyrene P1

an elastic block copolymer P2 of at least one vinylaromatic monomer and at least one diene monomer

a polyphenylene ether P3, optionally as a compound together with a foamable polystyrene,

wherein the component P2 to more than 4.5 wt .-%, based on the sum of P1, P2 and P3 is included.

2. Expandable thermoplastic polymer blend according to claim 1, characterized in that a blowing agent is contained.

3. Polymer blend according to at least one of the preceding claims, characterized in that, based on the sum of P1, P2 and P3 are included

93 to 41 wt .-% P1 5 to 45 wt .-% P2, in particular at least 5, preferably at least

10% by weight 2 to 14% by weight P3.

4. Polymer blend according to at least one of the preceding claims, characterized in that in addition at least one additional polymer P4 and, if necessary, conventional additives are contained.

5. A polymer blend according to at least one of the preceding claims, characterized in that P2 contains polymerized units of a vinyl aromatic monomers having a hard phase-forming block A and polymerized units of a vinyl aromatic monomer and a diene-containing elastomeric, a soft phase-forming block B / A contains.

6. The polymer blend according to claim 5, characterized in that the glass transition temperature is Tg of block A is above 25 ⁰ C and the block B / A at 25 ⁰ C and is selected the phase volume ratio of block A to block B / A so that the proportion of hard phase in the entire block copolymer 1 to 40 vol .-% and the

Weight content of the diene is less than 50 wt .-%.

7. polymer granules containing a polymer blend according to at least one of the preceding claims.

8. A process for the preparation of polymer blend according to claim 6 by a) mixing the components P1, P2 and P3 according to claim 1 b) melting preferably in an extruder c) degassing d) mixing in a blowing agent and optionally additives e) cooling f) discharge granulate through a nozzle plate g)

9. Particle foam moldings obtainable by welding polymer granules according to claim 7.

10. Use of the particle foam moldings according to claim 9 as packaging material.