EP2953999A1

EP2953999A1 - Rigid polystyrene foams

Info

Publication number: EP2953999A1
Application number: EP14702860.9A
Authority: EP
Inventors: Wilhelm Frohs; Werner Handl
Original assignee: SGL Carbon SE
Current assignee: FROHS, WILHELM
Priority date: 2013-02-05
Filing date: 2014-02-05
Publication date: 2015-12-16
Also published as: KR101782702B1; KR20150115879A; US20150337101A1; WO2014122190A1

Abstract

The present invention relates to rigid polystyrene foams containing thermally treated non-graphitic anthracite coke particles, mouldings containing such rigid polystyrene foams, and the use of such mouldings for heat insulation.

Description

Polvstyrolhartschaumstoffe

The present invention relates to polystyrene rigid foams comprising thermally pretreated, non-graphitic anthracite coke particles, shaped bodies containing these rigid polystyrene foams and the use of these shaped bodies for thermal insulation.

Polystyrene rigid foams have long been known and are used, inter alia, as thermal insulation materials in the form of boards in construction. The rigid polystyrene foam has a closed-cell structure, ie this foam consists to a few percent of solid polystyrene and predominantly of trapped air. This closed-cell structure leads to a low thermal conductivity, which gives the polystyrene foam the good suitability as a thermal insulation material. In this case, the density of the polystyrene foam, which is determined by the degree of foaming of the polystyrene particles, has a decisive influence on the thermal conductivity. The polystyrene foam thermal insulation boards used in the building industry have densities of 20 or 30 kg / m ³ , which corresponds to a thermal conductivity of 40 to 35 mW / mK. In order to use as little polystyrene as possible, ie to save material, polystyrene foam with a density of less than 20 kg / m ³ was also considered, but this polystyrene rigid foam has too high a thermal conductivity of more than 45 mW / mK. In order to provide polystyrene rigid foam sheets having densities of less than 30 kg / m ³ , preferably less than 20 kg / m ³ , which despite the low density mentioned have a lower, satisfactory thermal conductivity for use as an insulating material, it is known to add athermane materials to the polystyrene foam , Athermanous materials are materials that absorb the heat, in particular the heat due to infrared radiation. Accordingly, the addition of athermanous materials reduces the radiation permeability to polystyrene foam. As athermane materials which can be added to the polystyrene rigid foam, metal oxides, such as Al ₂ O ₃ or Fe ₂ O ₃ , non-metal oxides, such as SiO ₂ , metal powder, aluminum powder, carbon black, graphite, calcined petroleum coke, meta-anthracite, anthracite or organic Dyes or dye pigments proposed (EP 0620246, WO 97/45477, WO 98/51734, WO 00/43442, WO 2010/031537, DE 202010013 850, DE 202010013851). By adding these athermanous materials, it is possible to produce a rigid polystyrene foam having a density of less than 20 kg / m ³ and a thermal conductivity of less than 40 mW / mK, preferably less than 35 mW / mK. When using finely ground graphite or calcined petroleum coke as athermanes material, however, an energy-intensive grinding is necessary. Furthermore, it is difficult to disperse the, for example, ground graphite particles in the polystyrene matrix. In particular, when using anisotropic petroleum cokes, such as coke, the raw material costs represent an additional disadvantage. DE 202010013850 describes the use of carbonaceous athermanen materials, such as meta-anthracite or anthracite, which have both graphitic and turbostratic structures and thus in the class of graphitic Carbons belong (see IUPAC nomenclature). Due to the partially graphitic structure of these particles, the rigid polystyrene foams containing such athermal particles have an increased intrinsic heat conduction, which leads to an increased thermal conductivity value and thus a poorer thermal insulation.

It is therefore an object of the present invention to provide an alternative rigid polystyrene foam containing an athermanous material suitable for thermal insulation, which has a density of less than 40 kg / m ³ , preferably less than 20 kg / m ^3, and a lower thermal conductivity than 40 mW / mK, preferably less than 35 mW / mK. The athermane material added here is intended to permit a more energy-efficient grinding, the In addition, these milled particles can be dispersed well in a polystyrene matrix. In the context of the present invention, this object is achieved by a rigid polystyrene foam which contains thermally pretreated, non-graphitic anthracite coke particles. In this case, these Anthrazitkoksteilchen act as athermanes material. Anthracite coke particles, when used herein, mean thermally pretreated, non-graphitic anthracite coke particles.

According to the invention, it has been recognized that polystyrene rigid foams comprising anthracite coke particles, preferably gas-calcined anthracite coke particles, have a density of less than 40 kg / m ³ , preferably less than 20 kg / m ³ , and a heat conductivity of less than 40 mW / mK, preferably less than 35 mW / mK ie it is possible to provide the desired thermal insulation properties. In addition, the anthracite coke particles can be grinded in a more energy-efficient manner in comparison with, for example, graphite particles (natural graphite or synthetic graphite), since the corresponding throughput is increased, with the proportion of unusable by-product (fine filter dust) being lower in comparison with graphite. Graphitic anthracite, which can be obtained by a temperature treatment at over 2200 ° C, represents a synthetic graphite. In addition, the ground Anthrazitkoksteilchen in the desired

Platelet shape are obtained. Furthermore, the anthracite coke particles can be better dispersed in the polystyrene matrix compared to graphite particles, since they are better wetted by the polystyrene matrix due to their surface properties and thus better dispersed. It has surprisingly been found that the Anthrazitkoksteilchen form less agglomerates and therefore to homogeneous dispersion requires less shear forces. This is particularly advantageous when incorporating the anthracite coke particles in the suspension and / or emulsion polymerization process. According to the present invention, the rigid polystyrene foam may be extruded polystyrene foam (XPS) or polystyrene foam (EPS).

A distinction of the rigid foams is carried out according to the manufacturing process. XPS is produced on extrusion lines as a continuous foam strand; In this case, polystyrene is melted in the extruder and after adding a blowing agent, such as CO2, continuously discharged through a slot die, which builds behind the slot die the foam strand. With this method, foams can be produced with a thickness between 20 and 200 mm. After passing through a cooling zone, with downstream machines, the foam strand is cut to the desired shape, ie into blocks, plates or shaped parts. This extruded polystyrene foam is a closed-cell foam that absorbs only small amounts of moisture and is resistant to aging. For example, XPS is sold under the name Styrodur® C or Styrofoam®. In the production of EPS polystyrene granules (polystyrene grit), in which the blowing agent is copolymerized pentane, pre-expanded at temperatures above 90 ° C. Due to the temperature, the blowing agent evaporates and inflates the thermoplastic base material up to 20 to 50 times to polystyrene foam particles. From these foam particles blocks or plates or molded parts are then prepared in discontinuous or continuous systems by a second hot steam treatment between 1 10 ° C and 120 ° C. EPS is a predominantly closed-cell insulation material with trapped air, whereby EPS consists of 98% air and is also moisture-resistant. For example, EPS is sold under the name Styropor®. Polystyrene useful for the present invention can be obtained by a suspension polymerization of, for example, styrene in the presence of anthracite coke particles. In this process, the styrene is polymerized in aqueous suspension in the presence of anthracite coke particles, and the addition of a propellant, such as pentane, occurs before, during or after the polymerization. In the emulsion polymerization, for example, styrene is emulsified in water, wherein emulsifiers are used for emulsion stabilization. The initiators used for the polymerization are water-soluble, the polymerization likewise taking place in the presence of anthracite coke particles.

Polymers which can be used in the processes described above are expandable styrene polymers, in particular homopolymers and copolymers of styrene, preferably glass-clear polystyrene (GPPS), impact polystyrene (HIPS), anionically polymerized polystyrene or impact polystyrene (A-IPS), styrene-alpha-methylstyrene copolymers, acrylonitrile-butadiene-styrene polymers (ABS), styrene-acrylonitrile (SAN) acrylonitrile-styrene-acrylic esters (ASA), methyl acrylate-butadiene-styrene (MBS) and methyl methacrylate-acrylonitrile. Preferably, the polystyrene has a weight average M _w in the range of 150,000 g / mol to 350,000 g / mol, more preferably from 150,000 g / mol to 300,000 g / mol, most preferably from 180,000 g / mol to 250,000 g / mol. The determination of the weight average M _w can take place via the gel permeation chromatography at room temperature, it being possible, for example, to use tetrahydrofuran as eluent.

In the context of the invention it is preferred that the anthracite coke particles are homogeneously distributed in the rigid polystyrene foam. This homogeneous distribution of Anthrazitkoksteilchen in polystyrene foam, especially in poly- On the one hand, styrene particle foam (EPS) does not impair the fine cell structure of the styrene polymer particles, in particular of the expanded styrene polymer particles, and on the other hand results in improved thermal properties of the polymer rigid foam produced. Consequently, the anthracite coke particles do not interfere with nucleation in the production of, for example, EPS. This homogeneous distribution of Anthrazitkoksteilchen is also supported by the good dispersibility of these particles in the polystyrene matrix. Due to the surface properties of these anthracite coke particles, they can be wetted well by the polystyrene matrix, which, in the course of dispersion, ensures that the agglomerates are better divided, ie there are fewer agglomerates overall in the polystyrene matrix.

In a further preferred embodiment of the present invention, the Anthrazitkoksteilchen are platelet-shaped. On the one hand, the platelet form of the anthracite coke particles also does not impair the fine cell structure of the styrene polymer particles, in particular of the expanded styrene polymer particles. On the other hand, the platelets have a larger surface, for example compared to the spherical shape, as a result of which these platelets have a highly reflective effect on the incident infrared radiation. In yet another preferred embodiment of the present invention, the anthracite coke particles have an aspect ratio of greater than 2, preferably greater than 10, more preferably greater than 20. Advantageously, these aspect ratios are in the range of greater than 2 to 20, more preferably in the range of greater than 10 to 50, and most preferably in the range of greater than 20 to 100. In aspect ratio, the circle diameter (D) of the surface of the wafer is added to the thickness (T ) of the platelet, as shown in FIG.

With these aspect ratios, the incident infrared radiation is reflected particularly well. The good reflection of the infrared radiation requires that this radiation Development is only slightly absorbed, which means that, for example, moldings made of the polystyrene foam according to the invention do not strongly heat when exposed to sunlight and thus are not deformed. In the present invention, it is preferred that the Anthrazittkoksteilchen μιτι a diameter d ₅ o 0.2 to 20.0, more preferably μιτι 0.5 to 15.0, most preferably from 1, 0 to 10.0 μιτι , most preferably from 2.0 to 6.0 μιτι have. The d ₅₀ value indicates the average particle size, with 50% of the particles being smaller than the stated value.

The thermal treatment of anthracite is carried out on an industrial scale usually in gas-fired shaft furnaces or in electrically operated furnaces. This calcining technology is also referred to as gas-calcined anthracites (Gas Calcined Antracite, GCA) and electrically calcined anthracites (Electrically Calcined Anthracites, ECA). In the case of the gas-calcined anthracite, the temperature range at which the anthracite is treated gives a non-graphitic anthracite coke. In the case of an electrocalcination, if the temperature treatment takes place at below 2200 ° C., a non-graphitic anthracite coke is likewise obtained. When green anthracite is treated at temperatures above 2200 ° C, a graphitic carbon, i. an anthracite-based synthetic graphite.

The desired non-graphitic anthracite cokes can be made by the thermal treatment of green anthracite in a temperature range of greater than 500 ° C to 2200 ° C. When using thermally treated anthracite according to this invention, the thermal treatment takes the form of gas or electrocalcination, preferably in the form of gas calcination. The anthracite is in the gas calcination at temperatures in a range of 1200 ° C to 1500 ° C and in the electrocalcination at temperatures in a range from 1800 ° C to 2200 ° C, with the formation of graphitic regions not taking place. In the context of the invention, it is preferred that an anthracite coke which has been prepared by means of gas calcination is used. In general, the starting material is a green anthracite, ie a coal with the highest degree of coalification and a reflecting surface. Anthracites are fundamentally different from other types of coal due to their low volatile content (<10% by weight), density of approx. 1.3 to 1.4 g / cm ³ and carbon content of> 92% by weight. % marked. The energy content ranges from approx. 26 MJ / kg to 33 MJ / kg. The macerate content, ie the content of organic, rock-forming components, should have the following values:

Colinite content> 20%, preferably> 50%, Telinitgehalt <45%, preferably <20% and Vitrinitgehalt> 60%, preferably> 70%. Preferably, a high-quality anthracite is used for the present invention, having a content of volatile constituents of less than 5 wt .-% and a carbon content of at least 95 wt .-% after gas or Elektrkalzinierung. An anthracite, which has been subjected to either gas calcination at about 1250 ° C or electrocalcination at 1800 ° C to 2200 ° C, for example, can be characterized as follows:

Gas calcination Electrocalcination

Density [g / cm ¹³ ]> 1, 7, preferably> 1, 8> 1, 7, preferably> 1, 8

Sulfur [wt .-%] <7.0, preferably <5.0 <1, 0, preferably <0.5

Hydrogen content [% by weight] <0.2, preferably <0.15 <0.08, preferably <0.05

Ash [wt%] <8.0, preferably <5.0 <6.0, preferably <5.0 The anthracite coke according to the present invention preferably has a density of> 1, 8 g / cm ³ , preferably a sulfur content of <5.0 weight percent (wt .-%), preferably a hydrogen content of <0.15 wt .-% and preferably an ash content of <5.0% by weight.

In order to ensure the low thermal conductivity of the thermal insulation panels as well as the relatively energetically favorable particle preparation, it is essential that the anthracite coke particles are structurally in a completely non-graphitic state.

To demonstrate this non-graphitic structure and its demarcation to graphitic structures or partial graphitic structures, the X-ray fine structure analysis is applied in the form of a powder diffractometer in Bragg-Brentano arrangement and Cu _a radiation. A graphitic or partially graphitic structure is present if the three-dimensional interferences of the graphite lattice (100/101/102/1 10 and 1 12) are detectable in the X-ray diffractogram, as shown in Figure 2 (see Fitzer, Funk, Rozploch, 4th London International Carbon and Graphite Conference, 1974). The International Union of Pure and Applied Chemistry (IUPC) gives the following descriptions for the two terms "graphitic and non-graphitic carbon" (German translation, German Ceramic Society, Technical Committee Report No. 33, 3rd report of the working group "Carbon, terminology for the description of Carbon as a solid, W. Klose, K.-H. Köchling, C. Vogler, R-Wolf, 2009, ISBN 978-3-89958-770-8. Graphitic carbon:

Description:

Graphitic carbons are all carbon species that contain the element carbon in the allotropic form of graphite, regardless of existing structural defects.

Annotation:

The use of the term graphitic carbon is justified when a three-dimensional hexagonal crystalline long-range order in the material can be detected by diffraction methods, regardless of the volume fraction and the homogeneity of the distribution of such crystalline domains. If no three-dimensional long-range order is detectable, the term non-graphitic carbon should be used.

Non-graphitic carbon

Description:

Non-Graphitic Carbon Fibers are all types of solids consisting primarily of the element carbonaceous, with two-dimensional long-range ordering of carbon atoms in planar hexagonal networks. However, apart from the more or less parallel stacking, there is no measurable crystallographic order in the third direction (c direction). Annotation:

Thermal treatment converts some types of non-graphitic carbon into graphitic carbon, but not others (non-graphitizable carbon). Since (002) interference is easy to measure due to its high intensity, the average layer pitch available from it using the Bragg equation is often used for the first distinction between graphitic and non-graphitic carbons (Maire and Mehring (Proc Conf. On Carbon, Pergamon Press 1960, pp. 345-350). Accordingly, non-graphitic carbons have an average layer pitch of> 0.344 nm. From the layer spacings between 0.3354 nm and 0.344 nm, a degree of graphitization according to Maire and Mehring is often calculated Small graphitic volume fractions in a non-graphitic carbon environment are easily recognizable due to their increased X-ray intensity compared to a non-graphitic environment, as may be the case with blending of non-graphitic and graphitic carbons, other cases of which are catalytic graphitization effects such as the outbreak v on sulfur or the decomposition of metal carbides.

The athermanous particles used according to the invention are thermally pretreated, non-graphitic anthracite coke particles which are non-graphitic carbons. For the thermally pretreated, non-graphitic Anthrazitkoksteilchen used in the examples, an X-ray diffractogram results as shown in Fig. 3.

Table 1 :

X-ray data of the thermally pretreated, non-graphitic anthracite coke

(002), 2 theta half-width, Apparent crystal it- middle layer theta size in c-plane distance, c / 2,

Direction, Mean nm

Stack height, L _c , nm

25.28 4.45 180 0.3523 The X-ray diffractogram according to FIG. 3 shows only a broad (002) interference and the homologous (004) interference. Three-dimensional interference is not recognizable. Partial (002) interference in FIG. 4 also does not show a graphitized phase. The mean layer-plane distance from the angle of (002) interference is 0.3523 nm, well above the limit for graphitic carbons <0344 nm (see Table 1).

Temperature treatments of graphitizable carbons, such as anthracite, above 2200 ° C lead to the formation of graphitic regions. This also increases the thermal conductivity of these carbons, which is not desirable in this case. For an electrically calcined anthracite, which has been subjected to a temperature treatment of more than 2200 ° C., the following X-ray data results, for example:

2Theat = 26.52 °, c / 2 = 0.3361 nm, L _c = 1840 nm. This is an undesirable anthracite based synthetic graphite.

In yet another preferred embodiment of the present invention, the polystyrene foam comprises anthracite coke particles in an amount of from 0.5% to 10.0% by weight, preferably from 1.0% to 8.0% by weight. , particularly preferably from 2.0 wt .-% to 6.0 wt .-%, most preferably from 2.5 wt .-% to 4.5 wt .-% based on the amount of rigid foam.

The use of anthracite coke particles is further advantageous in that the particles are obtained after milling in the desired platelet form. For grinding jet mills can be selected from the group consisting of air, gas or steam jet mills. The preferred air jet mill used is a spiral jet or counter jet mill, particularly preferably a spiral jet or counter jet mill having an integrated air classifier. By using these mills become the accelerates the grinding particles so that the forces acting on the particles allow a direction-dependent crushing, ie it comes to tensile and frictional forces and particle collisions, which lead to a desired comminution of the particles and to a preferred particle shape.

If the rigid polystyrene foams are used as thermal insulation materials in the form of boards in construction, it is necessary that these insulating materials are difficult to incinerate, ie they pass the fire tests B1 and B2 according to DIN 4102. Thus, the polystyrene rigid foams according to the invention are not easy to incinerate and the required fire tests The rigid foams may additionally contain flame retardants. These flameproofing agents are organic halogen compounds, preferably organic bromine compounds, particularly preferably aliphatic, cycloaliphatic or aromatic bromine compounds, and / or phosphorus compounds. Particularly preferably, the organic bromine compounds are selected from the group consisting of hexabromocyclododecane, pentabromochlorocyclohexane or pentabromophenyl allyl ether and are used as phosphorus compounds 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide (DOP-O) or triphenyl phosphate (TPP) is particularly preferably used. In the polystyrene rigid foams according to the invention, the required amount of flame retardant can be reduced, ie the flame retardants are in the polystyrene foam in an amount of less than 2.0 wt .-%, preferably less than 1, 5 wt .-%, particularly preferably less than 1, 0 wt .-%, based on the amount of rigid foam before. Thus, the polystyrene foam according to the invention can be produced cheaper and more environmentally friendly, since less flame retardants, in particular less organic bromine compounds and / or phosphorus compounds are needed. A more cost-effective production of the polystyrene rigid foam according to the invention is also made possible by the rigid foam having a density of from 1 to 20 kg / m ³ , preferably from 5 to 20 kg / m ³ , particularly preferably from 10 to 20 kg / m ³ and especially preferably from 12 to 18 kg / m ³ . Here it comes to a material saving, since less polystyrene can be used.

The rigid polystyrene foam according to the invention has a thermal conductivity of from 20 mW / mK to 40 mW / mK, preferably from 25 mW / mK to 35 mW / mK. The present invention furthermore relates to a shaped body which contains a rigid polystyrene foam according to the invention and to the use of such a shaped body for thermal insulation. As a shaped body, for example, plates can be considered, which are used for thermal insulation, preferably in construction.

In the following the invention will be explained by means of examples, although these examples do not represent a limitation of the invention.

In comparison to these examples, polystyrene rigid foams which contain anthracite particles having graphitic structures as athermanous particles exhibit thermal conductivity values which are up to 2 W / m-K worse.

Examples:

Example 1 :

Polystyrene having a molecular weight of 220,000 g / mol was in an extruder together with 3.5 wt .-% gas calcined Anthrazitkoksteilchen, prepared on a jet mill, with a mean particle diameter d ₅ o of 3.5 μιτι and an aspect ratio of 20 and with 0.8 wt .-% Hexabromcyclododecan and 0.1 wt .-% dicumyl melted, mixed with 6.5 wt .-% pentane and cooled to about 120 ° C. The mixture thus obtained was discharged through a perforated nozzle to endless strands cooled over a cooling bath and granulated by means of a strand granulator to individual pieces. The cylindrical granules had a diameter of about 0.8 mm and a length of about 10.0 mm. The granules were then foamed to a density of 15 kg / m ³ . After conditioning for 24 hours, blocks were pressed and cut into 50 mm thick slabs using hot wire. The plates thus produced had an average thermal conductivity of 32 mW / mK.

Example 2:

In an aqueous suspension polymerization process according to the known prior art, based on the styrene components, 4% by weight of gas-calcined anthracite coke particles prepared on a spiral jet mill having an average particle diameter of 3.0 μm and an aspect ratio of 45 were mixed in and together with 1.5 parts by weight .-% hexabromocyclododecane as a flame retardant and pentane polymerized peroxide as a foaming agent. The beads obtained after separation of the aqueous phase had a mean diameter of 0.8 mm. After foaming the beads with water vapor to plates with a density of 14.5 kg / m ³ , a thermal conductivity of 33 mW / mK could be determined.

Example 3:

In a continuous extruder is polystyrene having a molecular weight of 220,000 g / mol together with 1, 0 wt .-% hexabromocyclododecane and 0.2 wt .-% dicumyl and 3.5 wt .-% gas calcined Anthrazitkoksteilchen, prepared on an opposed jet mill, melted with a mean particle diameter of 4.0 μιτι and an aspect ratio of 35. The foaming was made directly in the extruder to the final density. The polystyrene foam was discharged endlessly via a slot die and cooled. The moldings had a density of 14 kg / m ³ and a thermal conductivity of 31 mW / mK.

Claims

Claims: 1. Polystyrene foam,

characterized in that

this rigid foam contains thermally pretreated, non-graphitic anthracite coke particles.

2. Polystyrolhartschaumstoff according to claim 1,

characterized in that

the rigid foam is extruded polystyrene rigid foam (XPS) or polystyrene particle foam (EPS).

3. rigid polystyrene foam according to claim 1 or 2,

characterized in that

a homogeneous distribution of Anthrazikokstteilchen in rigid foam is present.

4. rigid polystyrene foam according to claim 3,

characterized in that

the anthracite coke particles are platelet-shaped.

5. polystyrene hartschau material according to claim 4,

characterized in that

the anthracite coke particles have an aspect ratio greater than 2.

6. polystyrene hartschau material according to claim 5,

characterized in that

the Anthrazitkoksteilchen have a diameter d ₅₀ from 0.2 to 20 μιτι.

7. polystyrene hartschau material according to claim 6,

characterized in that

the anthracite coke is present either as a gas or as an electrocalcined anthracite.

8. Polystyrolhartschaumstoff according to claim 7,

characterized in that

the anthracite coke particles in an amount of 0.5 wt .-% to 10 wt .-%, based on the amount of rigid foam, is included.

9. rigid polystyrene foam according to claim 8,

characterized in that

the anthracite coke particles were milled in jet mills selected from the group consisting of air, gas or steam jet mills.

10. rigid polystyrene foam according to claim 9,

characterized in that

the air jet mill represents a spiral jet or counter jet mill.

11. polystyrene hartschau material according to claim 10,

characterized in that

the rigid foam may additionally contain flame retardants.

12. rigid polystyrene foam according to claim 11,

characterized in that

the flame retardants are organic halogen compounds and / or phosphorus compounds.

13. polystyrene hartschau material according to claim 12,

characterized in that

the rigid foam has a density of 1 to 20 kg / m ³ and a thermal conductivity of 20 mW / mK to 40 mW / mK.

14. molded body,

characterized in that

it contains a polystyrene hard foam according to any one of claims 1 to 13.

15. Use of a shaped body according to claim 15 for thermal insulation.