EP2794739A1

EP2794739A1 - High-temperature peroxide-containing styrene polymer beads for seed polymerization

Info

Publication number: EP2794739A1
Application number: EP12806025.8A
Authority: EP
Inventors: Patrick Spies; Pascal Hesse; Bernhard Schmied; Libor SEDA; Rainer Ostermann; Frank Braun; Gregor Haverkemper; Uwe-Johannes Lehnen; Klaus Hahn; Jan Holoch
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2011-12-21
Filing date: 2012-12-17
Publication date: 2014-10-29
Also published as: US20150322182A1; BR112014015258A8; KR20140095584A; WO2013092466A1; MX2014007311A; BR112014015258A2; CN104011120A

Abstract

The invention relates to styrene polymer beads, characterized in that the styrene polymer beads contain 0.5 to 5 wt % of one or more high-temperature peroxides, wherein the high-temperature peroxides have a half-value period of one hour in the range of 110 to 160⁰C, measured in cumene.

Description

Description: The present invention relates to styrene polymer beads having a particle size in the range from 0.2 to 1.5 mm, the styrene polymer beads containing from 0.5 to 5% by weight of one or more high-temperature peroxides, and to processes for their styrene polymer beads Production and use as seed in suspension polymerization. The production of expandable polystyrene (EPS) by suspension polymerization is widespread. To stabilize the suspension, it is possible, for example, to use protective colloids, such as polyvinylpyrrolidone or so-called Pickering stabilizers, for example magnesium pyrophosphate, as described in EP-A 575 872. Bead size and bead size distribution can be controlled by the amount and dosage of the stabilizer.

The addition of graphite as an infrared absorber gives expandable styrene polymers, which can be processed into heat insulation materials with improved thermal insulation at low densities (US 6,130,265). The thermal conductivity is significantly reduced by reducing the infrared component. Similar improvements are possible with other IR absorbers such as carbon black, silicates, aluminum.

The polymerization in the presence of surface-active additives, such as particulate IR absorbers or flame retardants is often problematic because these additives can destabilize the suspension and lead to coagulation. WO 99/16817 and WO

03/033579 therefore propose, in the suspension polymerization in the presence of graphite particles, special peroxide initiators, such as tert-butyl peroxy-2-ethylhexanoate, which do not form benzoyl or benzyl radicals and use different peroxides with different decomposition temperatures. In general, by suspension polymerization, especially in the presence of

Graphite obtained EPS beads on a broad particle size distribution and large variations in the average particle sizes between different production approaches. This required subsequent screening to obtain products with marketable particle sizes. Usually, sieve fractions ranging from 0.8 to 2.0 mm are needed.

WO 00/61648 describes a multi-stage seed polymerization process for the preparation of polymer particles having an average particle size of at least 50 μm, in which an initiator diffuses into the seed and activates it. A process for the preparation of expandable styrene polymer particles from styrene, a

Methylstyrene and divinylbenzene by suspension polymerization in the presence of a seed of polystyrene is known, for example, from JP-A 2009-138146. As a rule, per- oxidinitatoren used as polymerization initiators both for the production of the seed and for the subsequent suspension polymerization.

Processes for the production of carbon black or graphite-containing, expandable polystyrene by seed polymerization are known, for example, from WO 2010/06631, US 2009/0030096 A1 or JP-A 62-13442. In this case, a minigranulate obtained by mixing graphite into a polystyrene melt and extruding and granulating is used as seed in a subsequent suspension polymerization. However, the particle size of the seed is limited by the minimum diameter of the perforated plate. Furthermore, temperature-sensitive additives, for example flame retardants, such as HBCD or peroxides, such as dicumyl peroxide, can not be incorporated into the seed without at least partial decomposition. Due to high melt viscosities and blockage of the perforated plate, the extrusion of granules with high graphite content is also problematic. The object of the present invention was to provide styrene polymer beads which contain one or more high-temperature peroxides so that they can be used as seed in a suspension polymerization without the further addition of peroxides. In particular, the Styrolpolymerisatperlen should be free of volatile blowing agents, but contain the usual auxiliaries, in particular particulate additives.

The object was achieved by the styrene polymer beads according to claim 1.

Preferred embodiments are given in the dependent claims. The styrene polymer beads according to the invention contain from 0.5 to 5% by weight, preferably from 1 to 4% by weight, of one or more high-temperature peroxides.

The styrene polymer beads preferably contain from 0.5 to 5% by weight, particularly preferably from 1 to 4% by weight, of dicumyl peroxide as high-temperature peroxide.

The Styrolpolymerisatperlen usually have a bead size in the range of 0.2 to 1, 5 mm, preferably 0.3 to 1, 3 mm. The bead size can be determined by screen analysis in which at least 94% of the screen fractions have a bead size of 0.2 to 1.5 mm, preferably 0.3 to 1.3 mm.

In addition to the high-temperature peroxide, the styrene polymer beads preferably contain 5 to 50% by weight of one or more particulate additives, in particular 5 to 50% by weight of carbon particles. The styrene polymer beads particularly preferably contain 5 to 50% by weight of graphite particles having an average particle size in the range from 1 to 50 μm. Particularly preferred styrene polymer beads contain 5 to 30 wt .-% graphite particles having an average particle size in the range of 1 to 50 μηη and 5 to 30 wt .-% of a brominated styrene polymer or brominated styrene-butadiene block copolymers as flame retardants. The styrene polymer beads preferably contain no blowing agent. This allows easy and safe transport. The propellant-free Styrolpolymerisatperlen are storage stable at room temperature for several months.

The styrene polymer beads of the invention can be prepared, for example, by a process comprising the steps: a) preparation of styrene polymer beads by a first suspension polymerization of an aqueous suspension containing styrene monomers and optionally particulate additives in the presence of a high-temperature peroxide,

b) separation of the styrene polymer beads,

c) optionally sieving out one or more sieve fractions of the styrene polymer beads.

In a preferred process for preparing the styrene polymer beads according to the invention, styrene monomers are polymerized in aqueous suspension in the presence of from 0.5 to 5% by weight of a high-temperature peroxide and from 0.1 to 3% by weight of a low-temperature superoxide at a maximum temperature of 130 ° C. wherein the suspension polymerization is carried out for less than 1.5 hours at a temperature in the range of 120-130 ° C. The styrene polymer beads according to the invention are particularly suitable as seed in the suspension polymerization.

The invention therefore also provides a process for the preparation of expandable styrene polymers, wherein the styrene polymer beads according to the invention are used as seed in the suspension polymerization of styrene monomers and a blowing agent is added during or after the polymerization. This second suspension polymerization, referred to hereinafter as stage d), can be carried out in a separate process, for example after the styrene polymer beads have been transported to another production site: d) preparing an aqueous suspension of the styrene polymer beads and carrying out a second suspension polymerization in the presence of blowing agent and metering styrene monomer,

Expandable styrene polymers are understood as meaning blowing agent-containing styrene polymer beads. Suitable styrenic polymers are homopolymers or copolymers of styrene, styrene derivatives or copolymerizable ethylenically unsaturated monomers. These are obtained in stages a) and d) by suspension polymerization of styrene and the corresponding copolymerizable monomers, for example alkylstyrenes, divinylbenzene, 1,4-butanediol dimethacrylate, para-methyl-α-methylstyrene, α-methylstyrene or acrylonitrile, butadiene, acrylic esters or methacrylic acid esters educated. Particularly preferably, only styrene is used as the monomer in all polymerization stages.

The suspension polymerization of styrene is known per se. It is described in detail in the Plastics Handbook, Volume V, "Polystyrene", Carl Hanser Verlag, 1969, pages 679 to 688. In this case, in general styrene, optionally together with the above-mentioned comonomers, suspended in water and in the presence of polymerized organic or inorganic suspension stabilizers. The volume ratio of aqueous to organic phase is preferably between 0.5 and 1, 6, in particular between 1, 0 and 1, 4.

Stage a)

Suitable particulate additives are all additives which do not dissolve significantly in the styrene polymers. Preference is given as particulate additives IR absorbers such as metal oxides, z. As titanium dioxide or carbon particles used. As carbon particles, various natural or synthetic carbon blacks or graphites can be used. The carbon particles preferably contain at least 1, preferably at least 5% by weight of graphitic structures. Preferably, the carbon particles have an ash content, determined according to DIN 51903 of 0.005 to 15 wt .-%, preferably 0.01 to 10 wt .-% to. Particular preference is given to using particulate additives as graphite particles having an average particle size in the range from 1 to 50 μm.

The preferably used graphite preferably has an average particle size of from 1 to 50 μm, in particular from 2.5 to 12 μm, a bulk density of from 100 to 500 g / l and a specific surface area of from 5 to 20 m ² / g. It can be used natural graphite or ground synthetic graphite.

The proportion of the sum of all particulate additives is preferably in the range of 5 to 40 percent by weight, in particular 10 to 30 percent by weight, based on styrene polymer beads. Particular preference is exclusively given to using carbon particles, in particular graphite, as particulate additives.

10 to 30 wt .-%, based on Styrolpolymerisatperlen, graphite particles having an average particle size in the range of 1 to 50 μηη are used in step a) as particulate additives. Silane-modified carbon particles which are modified with silane, for example, at from 0.01 to 1% by weight, preferably from 0.1 to 0.5% by weight, based on the carbon particles, can also be used as carbon particles. The silane-modified carbon particles preferably have C3-C16 on their surface.

Alkylsilane or arylsilane groups, in particular C6-Ci2-alkylsilane groups or phenylsilane groups. In particular, alkyl or aryl silanes having 1 to 3 halogen atoms or methoxy groups on the silicon atom are suitable for modifying the carbon particles. Preference is given to using C 3 -C 16 -alkylsilanes, or arylsilanes, in particular octyltrichlorosilane, chloro (dodecyl) dimethylsilane, hexadecyltrimethoxysilane or phenyltrichlorosilane.

The modification with silanes leads to a hydrophobization of the surface of the carbon particles by silyl groups, so that the interfacial activity of the carbon particles which disturbs the suspension process is markedly reduced. The method known per se for hydrophobicizing hydrophilic surfaces by silane in the gas phase or in solvents, such as toluene, surprisingly also works with the relatively hydrophobic graphite in order to mask the remaining polar group. The surface modification of the carbon particles allows better compatibility with or even a connection to the polymer matrix. In addition to the particulate additives, the usual additives, for example flame retardants, nucleating agents, UV stabilizers, chain transfer agents, plasticizers, pigments and antioxidants can be added in step a).

In addition to the additives already mentioned above, the customary peroxide initiators and suspension stabilizers, such as protective colloids, inorganic pickering salts and anionic and nonionic surfactants, are particularly suitable for the suspension polymerization.

Halogen-containing or halogen-free flame retardants are preferably used as additives. Particularly suitable are organic, in particular aliphatic, cycloaliphatic and aromatic bromine compounds, such as hexabromocyclododecane (HBCD), Pentabrommonoch- lorcyclohexan, Pentabromphenylallylether or brominated styrenic polymers, such as styrene-butadiene block copolymers, which can be used alone or as a mixture. The flame retardants used are preferably exclusively brominated styrene polymers or brominated styrene-butadiene block copolymers.

The halogenated polymer used as flame retardant preferably has an average molecular weight in the range from 5,000 to 300,000, in particular 30,000 to 150,000, determined by gel permeation chromatography (GPC) in tetrahydrofuran over polystyrene standard. The halogenated polymer has a weight loss of 5 wt .-% at a temperature of 250 ° C or higher, preferably in the range of 270 to 370 ° C in the thermogravimetric analysis (TGA). The effect of the bromine-containing flame retardants can be improved by adding CC or OO-labile organic compounds. Examples of suitable flame retardant synergists are dicumyl and dicumyl peroxide. A preferred combination consists of 0.6 to 5 wt .-% of organic bromine compound and 0.1 to 1, 0 wt .-% of CC or OO-labile organic compound.

The plasticizers used in stage a) are generally 0.1-10% of white oil or hexamine dinch in order to improve the expandability of the end product.

To stabilize the aqueous suspension, a phosphate, preferably magnesium pyrophosphate or tricalcium phosphate, in amounts of from 0.3 to 5 wt .-%, based on water, are used. Magnesium pyrophosphate is particularly preferably used.

To stabilize the aqueous suspension in step a), in particular when using high proportions of a particulate additive, magnesium sulfate heptahydrate is added in addition to magnesium pyrophosphate. Preference is given to an addition of 0.05 to 1% by weight of magnesium sulfate heptahydrate, based on water. The addition of magnesium sulfate heptahydrate is particularly preferably also in the range from 0.1 to 0.5% by weight, based on the organic phase. The organic phase is composed of the monomers and optionally styrene polymers and non-water-soluble additives.

The magnesium pyrophosphate is preferably prepared immediately prior to the polymerization by combining highly concentrated solutions of pyrophosphate and magnesium ions, using the stoichiometric amount of a magnesium salt required for the precipitation of Mg2P2Ü7. The magnesium salt may be in solid form or in aqueous solution. In a preferred embodiment, the magnesium pyrophosphate is prepared by combining aqueous solutions of sodium pyrophosphate (Na ₄ P ₂ O 7) and magnesium sulfate (MgSO ₄ 7H ₂ O). The magnesium salt is added in at least the stoichiometrically required amount, preferably in a stoichiometric amount. For the process according to the invention, it is favorable if there is no excess of alkali pyrophosphate.

In the process according to the invention are preferably sulfonate-containing

Emulsifiers, called extender used. These extenders include, for example, sodium dodecyl benzene sulfonate, long chain alkyl sulfonates, vinyl sulfonate, diisobutyl naphthalene sulfonate. The extenders used are preferably alkali metal salts of dodecylbenzenesulfonic acid and / or alkali metal salts of a mixture of C 12 -C 17 -alkylsulfonic acids. A particularly suitable mixture of C 12 -C 17 -alkyl sulfonates consists predominantly of secondary sodium alkyl sulfonates having the average chain length C 15. Such a mixture is called E30 sold by Leuna Tenside GmbH. The extenders increase the ability to stabilize the suspension in the presence of sparingly soluble inorganic compounds.

The extenders are usually in amounts between 0.5 and 15, preferably 2 to

10 wt .-%, based on magnesium pyrophosphate used.

To increase the stability of the suspension during the polymerization, it may be necessary, in particular before metering the extender, depending on the type of stirrer and reactor used, to increase the stirrer speed. The average power input is preferably above 0.2 kg kg reactor charge.

If the mean particle diameter of the styrene polymer beads becomes too small, the amount of extender used can be reduced or the stirrer speed can be lowered after extender dosing so that the average power input assumes a value of less than 0.2 W / kg.

It has been shown that it is favorable for the stability of the suspension if, at the beginning of the suspension polymerization, a solution of polystyrene (or a corresponding styrene copolymer) in styrene (or the mixture of styrene with comonomers) is present. Preference is given to starting from a 0.5 to 30, in particular 3 to 20 wt .-% solution of polystyrene in styrene. In this case, it is possible to dissolve fresh polystyrene in monomers, but it is expedient to use so-called edge fractions which are separated off as too large or too small beads in the separation of the bead spectrum occurring in the production of expandable polystyrene. Particular preference is given to using edge fractions from step a) which have been separated off in step c).

In addition to the customary peroxides in stage a), preference is given to using at least one high-temperature peroxide. A high-temperature peroxide is a peroxide which in Cumene has a half-life of 1 hour in the range from 110 to 160 ° C., preferably in the range from 120 to 140 ° C., particularly preferably in the range from 125 to 135 ° C. Examples of suitable peroxides are di-tert-amyl peroxides, tert-butyl peroxybenzoate, di (tert-butylperoxyisopropyl) benzenes, 2,5-dimethyl-2,5-di (tert-butylperoxy) hexanes and dicumyl peroxide. Dicumyl peroxide is particularly preferably used as high-temperature peroxide. The at least one high-temperature peroxide in stage a) is generally in amounts of at least 0.5 wt .-%, preferably in the range of 1, 1 to 5.0 wt .-%, particularly preferably in the range of 1, 3 bis 4 wt .-%, based on Styrolpolymerisatperlen used.

5 to 50% by weight of graphite and 0.5 to 5% by weight of dicumyl peroxide, each based on styrene polymer beads, are particularly preferably used in step a), and the suspension polymerization in step a) is less than 1.5 h at one temperature carried out in the range of 120-130 ° C, in this way to obtain a Präpolymierisat which sufficiently undecomposed Contains dicumyl peroxide, and a suspension polymerization in step d) without the addition of other peroxides allows. In addition, it can also act as a flame retardant synergist in the expandable styrene polymer. The high-temperature peroxide in the styrene polymer beads is preferably present in amounts of from 50 to 100% by weight, more preferably in amounts of from 60 to 80% by weight, of the amount used in undecomposed form. This remaining high-temperature peroxide may act as the sole polymerization initiator in the main polymerization (step d).

The invention therefore also relates to styrene polymer beads which contain 5 to 50% by weight of graphite .-%, preferably 10 to 30% by weight and 0.5 to 5% by weight, preferably 1 to 4% by weight of dicumyl peroxide, in each case based on styrene polymer beads.

Stage b) The styrene polymer beads obtained are first isolated from the aqueous phase. Subsequently, the styrene polymer beads may be used directly or by partitioning and selecting a particle size fraction (step c) in a main polymerization (step d).

Stage c)

In optional step c), the styrene polymer beads are divided into fractions of different particle size and one or more fractions are selected for subsequent steps. As a rule, the fractionation takes place by sieving out one or more sieve fractions. By suitably selecting the sieving of the styrene polymer beads, the bead size of the expandable styrene polymer can be controlled in a targeted manner. Preferably, in stage c), a sieve fraction of the styrene polymer beads having a bead size in the range from 0.2 to 1.5 mm, preferably in the range from 0.3 to 1.3 mm, is screened off.

Stage d)

In step d) at least one second suspension polymerization is carried out. This means that the process can be carried out in two or more stages. For example, steps b) to d) can be carried out several times, wherein at least one suspension polymerization is carried out in the presence of blowing agent and with metering of further styrene monomers. However, the process according to the invention is preferably carried out in two stages with a single execution of stages a), b), c) and d).

In the at least second suspension polymerization, the one or more fractions of the prepolymer beads separated in step b) or selected in step c) are initially introduced in aqueous suspension. In contrast to the suspension polymerization in stage a), in which generally the entire amount of styrene monomer is initially charged, the styrene monomer is preferably added continuously in stage d). As a rule, from 10 to 60% by weight, preferably from 15 to 35% by weight, particularly preferably from 25 to 35% by weight, based on expandable styrene polymer, of styrene polymer beads are initially introduced into the aqueous phase and the remaining part is used as monomers, especially preferably added continuously as styrene monomer. Before starting the polymerization, the styrene polymer beads may first be allowed to swell below the polymerization temperature with an organic peroxide, such as tert-butyl peroxy-2-ethylhexanoate. Furthermore, it has proved to be advantageous to meter a portion of the styrene monomer to be metered or a white oil also already below the polymerization temperature.

In step d), if appropriate, the particulate additives and additives described for step a) can be used.

To stabilize the second suspension polymerization, a phosphate, preferably magnesium pyrophosphate or tricalcium phosphate, is likewise used. Magnesium pyrophosphate is generally initially charged at the beginning of the polymerization and in stage d) generally in a concentration of between 0.03 and 2.0% by weight, preferably between 0.05 and 0.5% by weight and more preferably between 0 and 0 , 1 and 0.2 wt .-%, based on the aqueous phase used.

Furthermore, an extender is likewise introduced into the aqueous phase before the beginning of the polymerization in stage d). The extenders are usually used in amounts of between 0.5 and 15, preferably 2 to 10 wt .-%, based on magnesium pyrophosphate. The blowing agents used are usually aliphatic hydrocarbons having 3 to 10, preferably 4 to 6 carbon atoms, for example n-pentane, iso-pentane or mixtures thereof. The blowing agent is added in the usual amounts of from 1 to 10% by weight, preferably from 3 to 8% by weight, based on the weight of the styrene polymers present in the expandable styrene polymer.

The styrene polymer beads are usually used in a proportion in the range from 10 to 60% by weight, preferably in the range from 20 to 40% by weight, based on expandable styrene polymer, in the aqueous phase. The metering of styrene monomer in stage d) is generally carried out continuously, preferably over a period in the range from 1 to 5 hours. It has proven to be advantageous to dose 5 to 15 wt .-% of the styrene monomer to be metered already in the heating phase at temperatures below 100 ° C in the reactor. The polymerization in stage d) is preferably carried out at least partially at a temperature in the range from 1 to 130 ° C. Preferably, in step d) no peroxidic initiator is added. In particular, the use of a conventional low-temperature initiator such as tert-butyl peroxy-2-ethylhexanoate can be dispensed with if the styrene polymer beads as described above contain a high-temperature initiator, for example dicumyl peroxide. This has the advantage that the polymerization in stage d) can be carried out at temperatures above 120 ° C., which allows a shorter polymerization time. In addition, it is easier to achieve a homogeneous distribution of graphite between the core and the edge regions of the bead polymer, since at temperatures above 120 ° C, the diffusion of styrene into the center of the bead is greatly accelerated. Post-dosing of dicumyl peroxide at the beginning of the main polymerization is problematic because dicumyl peroxide is incompletely taken up by the styrene polymer beads and partially decomposes under the typical polymerization conditions to cumyl hydroperoxide, which leads in the water phase to a parallel emulsion polymerization. As a result, in this case, a very strong formation of white, graphite-free secondary polymer occurs.

The expandable styrene polymer beads obtained by the processes can be coated with the usual coating agents, for example metal stearates, glycerol esters and finely divided silicates. The propellant-containing styrene polymer particles produced in step d) generally have a diameter between 0.2 and 4 mm, preferably between 0.7 and 2.5 mm. They can be prefoamed by conventional methods, for example with steam, into foam particles with a diameter of between 0.1 and 2 cm and a bulk density of between 5 and 100 kg / m ³ .

The prefoamed particles can then be foamed by conventional methods to foam moldings having a density of 5 to 100 kg / m ³

The expandable styrene polymers obtained by the processes can be made into polystyrene foams having densities of from 5 to 35 g / l, preferably from 8 to 25 g / l and especially from 10 to 15 g / l. For this purpose, the expandable particles are prefoamed. This is usually done by heating the particles with water vapor in so-called pre-expanders.

The pre-expanded particles are then welded into shaped bodies. For this purpose, the pre-expanded particles are filled in non-gas-tight molds and subjected to steam. After cooling, the moldings can be removed.

The foams produced from the expandable styrene polymers are characterized by excellent thermal insulation. This effect is particularly evident at low densities. The thermal conductivity is so low that it meets the requirements of the heat conductivity class 035 (according to DIN 18164, Part 1 Tab. 4). The embodiment of the suspension polymerization of the process is characterized by a significantly increased stability of the suspension without phase inversion. The improved stability of the suspension leads to a safer and more efficient process. Due to the lower amount of stabilizer and better control of the bead size distribution is achieved. The internal water content of the resulting expandable styrene polymers can be significantly reduced.

The process makes it possible to increase the yield of the fractions having a desired and marketable bead size distribution of, in particular, graphite-containing expandable styrene polymers. If a screening of the styrene polymer bead is dispensed with, narrower particle size distributions, ie. achieve higher yield of value fraction compared to a classical suspension polymerization in the presence of graphite.

EXAMPLES Unless stated otherwise, the following starting materials were used for the examples:

Graphite: Graphite UF 99.5 from Graphitwerke Kropfmühl KG

VE-Waser: demineralized water

HBCD hexabromocyclododecane

Br-SBC brominated styrene-butadiene diblock copolymer (M _w 56.0000, styrene block content

37%, 1, 2-vinyl content 72%, TGA weight loss 5% at 238 ° C), prepared according to Example 8 of WO 2007/058736

Trigonox 21S tert-butyl-peroxy-2-ethylhexanoate

Winog 70 mineral oil

PS 158K polystyrene PS 158K from Styrolution GmbH

Emulsifier K30 Blend of linear alkyl sulfonates (Ci ₅ H ₃ o.9 (S0 ₃ Na) i .i, HLB 1 1 -12), 1% by weight aqueous solution

The bead size distribution was determined by sieve analysis (standard 1) and evaluated as grain size KG and relative fraction (R).

The β value is defined as follows and is based on the Rosin, Rammler, Sterling, Bennet distribution; β = arctane (1 / n) ^* 180 n; with n =

sieve: mesh size of the respective sieve bottom, d ': average particle diameter at 63% by weight of the integral particle size distribution according to Rosin, Rammler, Sterling, Bennet.

Preparation of a Mg2P207 suspension:

For the following examples, a freshly prepared amorphous magnesium pyrophosphate precipitate (MPP suspension) was used as the Pickering stabilizer. For the preparation of the Mg2P2Ü7 suspension, in each case 931.8 g of sodium pyrophosphate (Na ₄ P207, Giulini) dissolved in 32 kg of water at room temperature (25 ° C). With stirring, a solution of 1728 g of magnesium sulfate heptahydrad (Epsom salt, MgS0 ₄ × 7H ₂ O) in 7.5 kg of demineralized water was added to this solution and then stirred for 5 minutes. An aqueous suspension of magnesium pyrophosphate (MPP) was formed.

Comparative Experiment 1 (analogous to Example 1 from US 6,130,265):

To prepare the organic phase, 2.30 kg of polystyrene PS 158 K, 54 g of dicumyl peroxide (Perkadox BC-FF, AkzoNobel) and 24.5 g of 75% dibenzoyl peroxide (Lucidol 75, AkzoNobel) in 15, 3 kg of styrene dissolved and 176 g of graphite (UF99.5, Fa. Kropfmühl AG) suspended in the mixture.

In a pressure-resistant 50 l stirred tank with paddle stirrer, 20 l of demineralized water were initially charged and 2.87 kg of the freshly prepared Mg 2 P 2 O 7 suspension described above were added with stirring at 150 rpm. The stirred tank was equipped with a paddle stirrer, which was operated at a constant stirrer speed of 150 rpm during the entire experiment. This corresponds to an average power input of 0.143 W / kg for the stirrers and boiler dimensions used. The suspension was heated to 80 ° C. in the course of 1.2 hours and then to 134 ° C. over 4.5 hours. 140 minutes after reaching 80 ° C., 63.2 g of a 2% strength solution of the emulsifier E30 (prepared from E30-40 from Leuna Tenside GmbH, 40% by weight of a mixture of C 12 -C 17 -alkyl sulfonates in water) were added. , After a further 30 minutes, 1.17 kg of pentane-S (from Haltermann / Exxon) were metered in. Finally, polymerization was carried out at a final temperature of 134.degree.

The resulting expandable polystyrene beads were decanted off and dried to remove the internal water and coated with a coating of glycerol monostearate, glycerol tristate and precipitated silica. The EPS beads have a content of dicumyl peroxide of 0.2% by weight and have the following sieve distribution:

KG [mm] R [%]

2.50 0.0

2,00 0,1

1, 60 0.9

1, 40 2.6

1, 25 4.9

1, 00 19.6

0.90 12.2

0.63 35.1

0,50 1 1, 4

0.40 5.6 0.20 6.0

<0,20 1, 5

Comparative Experiment 2 (analogously to Example 3 from US Pat. No. 6,130,265): Comparative Experiment 1 was repeated with the difference that 636 g of graphite (4% by weight) were added to the organic phase.

KG [mm] R [%]

3.15 0.7

2.50 0.4

2,00 0,8

1, 60 2.3

1, 25 8.3

1, 00 16.6

0.80 22.5

0.63 20,7

0.50 1 1, 0

0.40 5.5

0.20 7.3

<0.20 4.0

Example 1: Stage a)

Preparation of the Styrene Polymer Beads To produce the organic phase, 2.80 kg of EPS from Comparative Example 2, 756 g of hexabromocyclododecane (Chemtura), 9.00 g of tert-butyl peroxy-2-ethylhexanoate (Trigonox 21 S, AkzoNobel), 182 g Dicumyl peroxide (Perkadox BC-FF, AkzoNobel), 18.0 g of dicetyl peroxydicarbonate (Perkadox 24-FL, AkzoNobel) and 420 g of white oil (Winog 70) dissolved in 14.0 kg of styrene and 2.10 kg of graphite (UF99 .5, Fa. Kropfmühl AG) suspended in the mixture.

In a pressure-resistant 50 l stirred tank with paddle stirrer, 15 l of demineralized water were initially introduced and 5.22 kg of the above-described, freshly prepared Mg 2 P 2 O 7 suspension were added with stirring at 240 rpm. The stirred tank was equipped with a paddle stirrer which was operated at a constant stirrer speed of 240 rpm throughout the experiment. This corresponds to an average power input of 0.579 W / kg for the stirrers used and boiler dimensions. The suspension was heated to 95 ° C. in the course of 1.5 hours and then to 127 ° C. over 4.2 hours. 100 minutes after reaching 80 ° C., 240 g of a 2% strength solution of the emulsifier E30 (prepared from E30-40 from Leuna Tenside GmbH, mixture of C 12 -C 17 -alkylsulfonates) were metered in. Finally, it was polymerized at a final temperature of 127 ° C.

The styrene polymer beads had an internal water content of 5.23% and an average diameter of 0.8 mm. Stage b)

The resulting styrene polymer beads were filtered through a suction filter (pore size 40 μηη) and dried to remove the surface water.

Stage d) main polymerization

600 g of demineralized water, 200 g of MPP suspension and 18.8 g of a 1% solution of the emulsifier E30 (manufactured from E30-40, Leuna Tenside GmbH) were placed in a 2 l stirred tank and then 250 g of the styrene polymer beads were introduced, with stirring 3.50 g of tert-butyl peroxy-2-ethylhexanoate (Trigonox 21 S, AkzoNobel) were added dropwise to the suspension within 1 minute. The kettle was sealed and 50 g of styrene was metered into the kettle over a period of 10 minutes. After reaching a temperature of 90 ° C, a further 533 g of styrene were added within 95 minutes. Subsequently, the reaction mixture was heated to 130.degree. From a temperature of 120 ° C., 67 g of pentane-S (from Haltermann / Exxon Co.) were added over a period of 40 minutes. For complete monomer conversion was polymerized with stirring for a further 2 hours at a temperature of 130 ° C. The propellant-containing polystyrene beads obtained were decanted off, dried by internal water and coated with a coating composition of glycerol monostearate, glycerol tristearate and precipitated silica. The resulting EPS beads showed the following bead size distribution

> 2.5 mm 0.5 g 0.07%

1, 4-2.5 mm 84.4 g 1 1, 20%

0.8-1.4 mm 493.3 g 65.46%

0.4-0.8 mm 107.4 g 14.25%

0-0.4 mm 68 9 9.02%

Example 2a: Example 1 was repeated with the difference that the Styrolpolymerisatperlen was screened through a sieve from Fritsch (Analysette 18). In the subsequent main polymerization, a sieve cut between 0.4 mm and 1, 25 mm was used.

2,00 mm 0,23 g 0,76

1, 60 mm 1, 49 g 4.90

1, 25 mm 13.29 g 43.69

1, 00 mm 10.38 g 34.12

0.80 mm 2.46 g 8.09

0.63 mm 2.38 g 7.82

0.50 mm 0.17 g 0.56

0.40 mm 0.02 g 0.07

<0.40 mm <0.02 g <0.01

Example 2b

Example 2a was repeated with the difference that 2.92 g of dicumyl peroxide dissolved in 5 g of styrene were metered into the cold reactor within 2 minutes in the main polymerization before the start of the heating phase. From the dried polymer the following sieve distribution could be obtained:

> 2.5 mm 0.5 g 0.06

1, 4-2.5 mm 73.5 g 9.34

0.8-1, 4 mm 571, 6 g 72.65

0.4-0.8 mm 92.5 g 1 1, 76

0-0.4 mm 48.7 g 6.19 white graphite-free polymer

Example 3

Example 1 was repeated with the difference that the Styrolpolymerisatperlen was screened through a sieve from Fritsch (Analysette 18) (step c). In the subsequent main polymerization, a sieve cut between 0.5 mm and 1, 25 mm was used.

Example 4

Example 2 was repeated using instead of white oil 420 g 1, 2-

Cyclohexanedicarbonsäurediisononylester (Hexamoll Dinch, BASF SE) were used. The internal water content of the styrene polymer beads was 4.76%. In the subsequent main polymerization, a sieve cut between 0.4 mm and 1, 25 mm was used. Example 5

Example 2 was repeated using 420 g of alkyl sulfonic acid ester of phenol (ASE) (Mesamoll 2, Lanxess AG) instead of white oil. The internal water content of the styrene polymer beads was 3.16%. In the subsequent main polymerization, a sieve cut between 0.4 mm and 1, 25 mm was used.

Example 6

Example 2 was repeated using instead of HBCD 1, 06 kg brominated styrene-butadiene block copolymer (Br-SBS) were used. The internal water content of the styrene polymer beads was 2.56%. In the subsequent main polymerization, a sieve cut between 0.4 mm and 1, 25 mm was used.

Example 7:

Stage a)

Preparation of styrene polymer beads

2.80 kg of EPS from Comparative Example 2, 756 g of hexabromocyclododecane (Chemtura), 9.00 g of tert-butyl peroxy-2-ethylhexanoate (Trigonox 21 s, AkzoNobel), 350 g of dicumyl peroxide (Perkadox BC-FF, AkzoNobel), 18.0 g of dicetyl peroxydicarbonate (Perkadox 24-FL, AkzoNobel) and 420 g of white oil (Winog 70) dissolved in 14.0 kg of styrene and 2.10 kg of graphite (UF99. 5, Kropfmühl AG) suspended in the mixture.

In a pressure-resistant 50 l stirred tank with paddle stirrer, 15 l of demineralized water were initially introduced and 5.22 kg of the above-described, freshly prepared Mg 2 P 2 O 7 suspension were added with stirring at 240 rpm. The stirred tank was equipped with a paddle stirrer which was operated at a constant stirrer speed of 240 rpm throughout the experiment. This corresponded to an average power input of 0.579 W / kg for the stirrer used and boiler dimensions. The suspension was heated to 95 ° C. in the course of 1.5 hours and then to 125 ° C. in the course of 4.2 hours. 100 minutes after reaching 80 ° C., 240 g of a 2% strength solution of the emulsifier E30 (prepared from E30-40 from Leuna Tenside GmbH, mixture of C 12 -C 17 -alkylsulfonates). Finally, polymerization was carried out at a final temperature of 125.degree.

Stage b) The resulting styrene polymer beads were decanted and dried to remove the surface water and sieved.

Stage c)

In the subsequent main polymerization a sieve cut between 0.4 mm and 1, 25 mm was used.

Stage d) main polymerization

596 g demineralized water, 196 g MPP suspension and 18.5 g of a 1% strength solution of the emulsifier E30 (prepared from E30-40, Leuna Tenside GmbH.) Were mixed in a 2.4 l stirred tank (crossbar stirrer, 360 rpm) ) and then charged 245 g of sieved Styrolpolymerisatperlen. The kettle was sealed, charged with nitrogen (0.5 bar) and metered at room temperature within 6 minutes 30 g of styrene in the kettle. The reactor was heated to 125 ° C. in the course of 61 minutes and a further 557 g of styrene were metered in over the course of 105 minutes. Subsequently, 65 g of pentane-S (from Haltermann / Exxon) were added over a period of 40 minutes. For complete monomer conversion was polymerized with stirring for a further 2 hours at a temperature of 130 ° C and then cooled to room temperature.

The propellant-containing polystyrene beads obtained were decanted off, dried by internal water and coated with a coating composition of glycerol monostearate, glycerol tristearate and precipitated silica. The resulting EPS beads showed the following bead size distribution.

2.00 mm 0.85

1, 60 mm 0.95

1, 40 mm 1, 4

1, 25 mm 15.96

1, 00 mm 40.33

0.80 mm 33.72

0.63 mm 5.44

0.50 mm 0.8

0.40 mm 0.14

0.20 mm 0.01

During the trial, samples are taken. With the polymer beads obtained after separation of the aqueous phase, a residual monomer determination was carried out by means of HPLC and molecular weight determination by means of GPC. The residual monomer content at the end of the polymerization was 0.22% by weight. Weight average molecular weight: M _w 247900, number average molecular weight: M _n 77610 and polydispersity: D = 3.19. Example 8:

Stage a)

Preparation of styrene polymer beads

For the preparation of the organic phase were 52.3 kg EPS according to Comparative Example 2, 18.8 kg Hexabromocyclododecan (Fa. Chemtura), 224 g of tert-butyl peroxy-2-ethylhexanoate (Trigonox 21 s, Fa. AkzoNobel), 8.71 kg dicumyl peroxide (Perkadox BC-FF, AkzoNobel), 437 g of dicetyl peroxydicarbonate (Perkadox 24-FL, AkzoNobel) and 10.4 kg of white oil (Winog 70) dissolved in 328.2 kg kg of styrene and 52.3 kg of graphite (UF99.5, Fa. Kropfmühl AG) suspended in the mixture.

378.0 kg of demineralized water were introduced into a 1 m ³ technical circulation vessel with crossbar stirrer and 171.1 kg of a freshly prepared Mg2P207 suspension and 828 g of magnesium sulphate ^* heptahydrate (bitter salt) were prepared with stirring at 240 rpm. submitted and added the organic phase from the batch kettle. It was first set a stirrer speed of 68 U / min (corresponding to an average power input of 0.29 W / kg).

The suspension was heated to 95 ° C. in the course of 1.5 hours and then to 125 ° C. within 4.2 hours. 89 minutes after reaching 80 ° C., 4.00 kg of a 2% strength solution of the emulsifier E30 (prepared from E30-40 from Leuna Tenside GmbH, mixture of C12-C17 sodium alkyl sulfonates) were metered in. After the emulsifier was metered, the stirrer speed was lowered to 42 rpm (this corresponds to an average power input of 0.070 W / kg). Finally, it was polymerized at a final temperature of 125 ° C.

Stage b)

The resulting prepolymer is isolated by means of a Siebschleuder from Siebtechnik (type Contourbex H 320) (sieve 0.2 mm), antistatically equipped with 200 ppm emulsifier E30 via a screw conveyor and heated by a flash dryer (average temperature: 70 ° C.). surface water dried. The resulting styrene polymer beads had an internal water content of 7.56% and a content of dicumyl peroxide of 1, 44 wt .-%.

Stage c) Screening

The styrene polymer beads were prescreened with a sieve cut between 0.4 mm and 1.25 mm.

Stage d) main polymerization

534 g demineralized water, 178 g MPP suspension and 17.2 g of a 1% solution of the emulsifier E30 (manufactured from E30-40, Leuna Tenside GmbH.) Were mixed in a 2.4 l stirred tank (crossbar stirrer, 360 rpm) ) submitted. Subsequently, 236.9 g of the sieved styrene polymer beads were charged. The kettle was closed, exposed to nitrogen (0.5 bar) and at room temperature, 31.4 g of styrene were metered in within 6 minutes. The contents of the reactor were heated to a temperature of 125 ° C. in the course of 61 minutes, then an additional 522.6 g of styrene were metered in over the course of 105 minutes. Thereafter, 63 g of pentane-S (from Haltermann / Exxon) were added over a period of 40 minutes. A temperature of 125 ° C. was maintained for a further 95 minutes, then the reactor contents were heated to 130 ° C. within 30 minutes and polymerized for a further 30 minutes at 130 ° C.

The propellant-containing polystyrene beads obtained were decanted off, dried by internal water and coated with a coating composition of glycerol monostearate, glycerol tristearate and precipitated silica. The resulting EPS beads showed the bead size distribution summarized in Table 3.

During the trial, samples are taken. With the polymer beads obtained after the separation of the aqueous phase, a residual monomer determination was carried out by means of HPLC and molecular weight determination by means of GPC. The residual monomer content at the end of the polymerization was 0.18% by weight. Weight average molecular weight: Mw 251610, number average molecular weight: Mn 84841 and polydispersity: D = 2.97.

Example 9:

Stage a) Preparation of the styrene polymer beads

To prepare the organic phase, 420 g of styrene polymer beads from Example 8, 219 g of hexabromocyclododecane (Chemtura), 1.80 g of tert-butyl peroxy-2-ethylhexanoate (Trigonox 21 s, AkzoNobel), 108 g of dicumyl peroxide (Perkadox BC-FF, AkzoNobel) and 3.5 g of dicetyl peroxydicarbonate (Perkadox 24-FL, AkzoNobel) dissolved in 2.80 kg of styrene and suspended 588 g of graphite (UF99.5, Fa. Kropfmühl AG) in the mixture.

The organic phase was dissolved in 3.04 l of demineralized water with 1.60 kg of MPP suspension and 7.90 g of magnesium sulfate heptahydrad (epsom salt) (from Kali and salt) in a 10 l stirred tank (blade stirrer, 300 rpm, corresponds to an average power input of 0.584 W / kg) introduced. The suspension was heated to 95 ° C. within 1.5 hours and then to 125 ° C. within 4.20 hours. 85 minutes after reaching 80 ° C., 37 g of a 2% strength solution of the emulsifier E30 (from Leuna Tenside GmbH) were metered in. Finally, it was polymerized at a final temperature of 125 ° C.

Stage b)

The resulting styrene polymer beads were decanted off and dried by surface water.

Stage c) Screening: The styrene polymer beads were prescreened with a wire cut between 0.45 mm and 1.00 mm

Stage d) main polymerization

534 g demineralized water, 178 g MPP suspension and 17.2 g of a 1% solution of the emulsifier E30 (manufactured from E30-40, Leuna Tenside GmbH.) Were mixed in a 2.4 l stirred tank (crossbar stirrer, 360 rpm) ) submitted. Subsequently, 181 g of the sieved styrene polymer beads were charged. The kettle was sealed, charged with nitrogen (0.5 bar) and at room temperature 27.3 g of styrene were metered in within 6 minutes. The reactor content was heated to a temperature of 125 ° C. over the course of 61 minutes, then a further 577 g of styrene were metered in over the course of 105 minutes. 150 minutes after reaching 125 ° C., 63 g of pentane-S (from Haltermann / Exxon Co.) were added over a period of 40 minutes. At a temperature of 130 ° C, the polymerization was terminated. The propellant-containing polystyrene beads obtained were decanted off, dried by internal water and coated with a coating composition of glycerol monostearate, glycerol tristearate and precipitated silica. The resulting EPS beads showed the bead size distribution summarized in Table 3. During the trial, samples are taken. With the polymer beads obtained after separation of the aqueous phase, a residual monomer determination was carried out by means of HPLC and molecular weight determination by means of GPC. The residual monomer content at the end of the polymerization was 0.31% by weight. Weight average molecular weight: M _w 202310, number average molecular weight: M _n 70665 and polydispersity: D = 2.86.

Example 10

Stage a) Preparation of the Styrene Polymer Beads 2.1 kg of EPS (prepared according to Comparative Example 2), 892 g of Br-SBC, 9.00 g of tert-butyl peroxy-2-ethylhexanoate (Trigonox 21 s, Fa. AkzoNobel), 365 g of dicumyl peroxide (Perkadox BC-FF, AkzoNobel), 18.0 g of dicetyl peroxydicarbonate (Perkadox 24-FL, AkzoNobel) and 420 g of white oil (Winog 70) dissolved in 14.0 kg of styrene and 2, 17 kg of graphite (UF99.5, Fa. Kropfmühl AG) suspended in the mixture.

The organic phase was introduced into 15 l of demineralized water containing 5.22 kg of MPP suspension in a 50 l stirred tank (paddle stirrer, 240 rpm, corresponding to an average power input of 0.579 W / kg). The suspension was heated to 95 ° C. in the course of 1.5 hours and then to 125 ° C. within 4.20 hours. 100 (+/- 5 min) minutes after reaching 80 ° C., 240 g of a 2% strength solution of the emulsifier E30 (prepared from E30-40 from Leuna Tenside GmbH) were metered in. Finally, it was polymerized at a final temperature of 125 ° C. Stage b)

The obtained Styrolpolymerisatperlen were decanted off and dried by surface water by flash drying. The styrene polymer beads had a viscosity number VZ of 74.6, which corresponds to a weight-average molecular weight of about 200,000 g / mol. The residual water content was 1.48 wt .-% and the residual monomer content 0.02 wt .-%. The EPS beads had the following bead distribution:

KG [mm] R [%]

3.15 0.0

2.50 0.1

2,00 0,2

1, 60 0.2

1, 25 5.3

1, 00 6.1

0.80 26.5

0.63 28.8

0,50 17,1

0.40 6.7

0.20 7.4

<0,20 1, 6

d ^' (calc.) = 0.81

ß (calc.) = 16.0 step c) Screening

The styrene polymer beads were prescreened with a wire cut between 0.4 mm and 1, 12 mm and then used in the main polymerization.

Stage d) main polymerization

In a 10 l stirred tank (crossbar stirrer, 170 rev / min) 3.24 kg of demineralized water were initially charged, which 1, 08 kg MPP suspension and 51 g of 2% solution of the emulsifier E30 (prepared from E30-40, Leuna surfactants GmbH). Then, 1.44 kg of the sieved styrene polymer beads were charged. The kettle was sealed, charged with nitrogen (0.5 bar) and at room temperature 320 ml of styrene were metered in within 10 minutes. The contents of the reactor were heated to a temperature of 125 ° C. within 137 minutes, then a further 3.39 l of styrene were metered in within 87 minutes. 27 minutes after reaching 125 ° C., 307 g of pentane-S (from Haltermann / Exxon Co.) are added over a period of 60 minutes. 1 10 minutes after reaching 125 ° C, the temperature is increased within one hour to 135 ° C and polymerized at this temperature (residual monomer content <1000 ppm). The propellant-containing polystyrene beads obtained were decanted off, dried by internal water and coated with a coating composition of glycerol monostearate, glycerol tristearate and precipitated silica. The weight-average molecular weight was M _w : 338200 g / mol. The EPS beads obtained showed the following bead size distribution.

KG [mm] R [%]

3.15 0.0

2.50 0.0

2,00 0,0

1.60 1.8

1.25 31.0

1.00 37.1

0.90 11.4

0.63 17.7

0.50 0.9

0.40 0.0

0.20 0.0

0.00 0.0

d ^' (calc.) = 1.23

ß (calc.) = 10.7

Table 1. Screen distribution of the styrene polymer beads

Table 2: Screen distribution of EPS beads

Grain size Example 3 Example 4 Example 5 Example 6

> 2.5 mm 0.01% 0.06% 0.07% 4.07%

1.4-2.5 mm 21.03% 14.28% 9.92% 24.06%

0.8-1.4 mm 78.37% 71.67% 77.13% 61.56%

0,4-0,8 mm 0,39% 12,45% 12,48% 10,05%

0-0.4 mm 0.20% 1.54% 0.4% 0.26% Table 3: Screen distribution of the EPS beads

Grain size Example 7 Example 8 Example 9

> 2.5 mm 0.26%

2.0-2.5 mm 0.85% 0.38%

1,6-2,0 mm 0,95% 0,29% 2,60%

1.4-1.6 mm 1.4% 6.49% 5.62%

1.25 - 1.4 mm 15.96% 16.84% 10.52%

1,0 - 1,25 mm 40,33% 38,12% 36,11%

0,8-1 mm 33,72% 24,93% 30,82%

0.63-0.8 mm 5.44% 13.08% 10.82%

0.5-0.63 mm 0.8% 0.85% 1.79%

0.4-0.5 mm 0.14% 0.13% 0.62%

0.2-0.4 mm 0.01% 0.12% 0.28%

> 0.2 mm 0.09% 0.16% d '(calculated) 1, 15 mm 1.146 mm (calculated) 10.72 10.88

Claims

claims

Styrene polymer beads, characterized in that the Styrolpolymerisatperlen contain 0.5 to 5 wt .-% of one or more high-temperature peroxides, wherein the high-temperature peroxides have a half-life of 1 hour in the range of 1 10 to 160 ° C, measured in Cumene.

Styrene polymer beads according to claim 1, characterized in that they contain 0.5 to 5 wt .-% dicumyl peroxide as high-temperature peroxide.

Styrene polymer beads according to claim 1 or 2, characterized in that they contain 5 to 50 wt .-% of one or more particulate additives.

Styrene polymer beads according to claim 3, characterized in that they contain 5 to 50 wt .-% of carbon particles as particulate additives.

Styrene polymer beads according to any one of claims 1 to 4, characterized in that they contain 5 to 50 wt .-% graphite particles having an average particle size in the range of 1 to 50 μηη.

Styrene polymer beads according to any one of claims 1 to 5, characterized in that they contain 5 to 30 wt .-% graphite particles having an average particle size in the range of 1 to 50 μηη and 5 to 30 wt .-% of an organic bromine compound as a flame retardant.

Styrene polymer beads according to any one of claims 1 to 6, characterized in that they contain no blowing agent.

A process for preparing styrene polymer beads according to claim 1, characterized in that styrene monomers in aqueous suspension in the presence of 0.5 to 5 wt .-% of a high-temperature peroxide and 0.1 to 3 wt .-% of a low-temperature peroxide at a maximum temperature of 130 ° C is polymerized, wherein the suspension polymerization is carried out for less than 1, 5 h at a temperature in the range of 120-130 ° C.

Use of the styrene polymer beads according to one of claims 1 to 7 as seed in the suspension polymerization.

Process for the preparation of expandable styrene polymers, characterized in that styrene polymer beads according to any one of claims 1-7 are used as seed in the suspension polymerization of styrene monomers and during or after the polymerization a blowing agent is added.