WO2012089574A1

WO2012089574A1 - Foam board based on styrene polymer-polyolefin mixtures

Info

Publication number: WO2012089574A1
Application number: PCT/EP2011/073519
Authority: WO
Inventors: Holger RUCKDÄSCHEL; Jens Assmann; Carsten Schips; Klaus Hahn; Georg GRÄSSEL; Jürgen Lambert; Christof Zylla; Peter Merkel; Geert Janssens
Original assignee: Basf Se
Priority date: 2010-12-28
Filing date: 2011-12-21
Publication date: 2012-07-05
Also published as: TW201233525A

Abstract

A thermoplastic extruded foam board having a thickness in the range from 15 mm to 200 mm and cells having an average cell size in the range from 20 to 2000 µm, characterized in that the cell membranes have a fibrous structure having fibre diameters below 1500 nm, is suitable, for example, as insulation material, in particular in the building industry.

Description

Foam board based on styrene polymer-polyolefin blends Description

The invention relates to a thermoplastic extrusion foam board based on styrene polymers, polyolefins and solubilizers, a process for their preparation and the use of the plate, for example as insulating material in the construction industry.

Particle foams based on polyolefin / styrene polymer mixtures are known, for example, from WO-A 2008/125250. The production of particle and extrusion foams, however, has significant process-related differences. In the production of particle foams, propellant-laden granules - starting from temperatures below the softening point of the material system - are heated and expanded by the introduction of energy (i.d.R. water vapor) (= pre-foaming). The prefoaming process is typically in the range of minutes. Subsequently, the prefoamed granules are conditioned and finally welded in a mold by the re-entry of energy (usually water vapor) to form parts or blocks. Accordingly, the pattern formation of multiphase systems always begins at low temperatures, which in the specific case are below the melting point of the polyolefins.

In contrast, in the production of extrusion foams, the material is first completely melted or plasticized and impregnated with blowing agents at elevated pressures. After a possible cooling of the melt, the foaming is usually carried out by a rapid reduction in pressure (for example, by exit of the loaded melt from a nozzle into the surrounding atmosphere). The foaming and adjustment of the morphology takes place within fractions of seconds to seconds. The structure formation of multiphase systems also begins at temperatures that are in particular cases above the melting point of the polyolefins.

The different processing processes in the case of particle and extrusion foams as well as the different requirements with regard to further processing therefore do not allow conclusions to be drawn regarding the suitability of known particle foam systems as extruded foams.

US Pat. No. 5,225,451 describes an extrusion foam of polyethylene as a continuous phase, a styrene-butadiene rubber and 1 to 15% by weight of polystyrene. Japanese Patent Publication JP-A 2008-173923, JP-A 2000-204185, JP-A 2004-238413, JP-A 2003-183438, JP-A 2000-212356 disclose extruded foam films based on polystyrene / polyethylene blends Addition of a solubilizer described.

From JP-A 2001-310968 extrusion foam sheets of 70 to 40 parts by weight of polyethylene, 30 to 60 wt .-% of polystyrene and 2 to 15 wt .-% of a partially hydrogenated styrene-butadiene block copolymer are described.

Finally, JP-A 2008-274072 discloses an extrusion foam sheet of polystyrene, polyethylene, polypropylene and a styrene rubber system containing block copolymers having polystyrene blocks at both ends and a polybutadiene or polyisoprene block therebetween. The blowing agents used are preferably chemical blowing agents.

Although good results are already achieved with the systems described, there is still a wide range of improvements, for example with regard to resistance to solvents, elasticity, damping behavior and low water absorption.

The object was therefore to develop further extruded foam boards with an improved property profile, in particular with regard to the properties mentioned.

It has been found that by using styrene polymers, polyolefins and certain solubilizers extrusion foam plates are obtained with a fibrous cell membrane structure, which have a favorable property spectrum.

Major challenges in the production of extruded foams having such a structure and hence advantageous properties are: (i) adjustment of the desired properties during the foaming process, ranging from fractions of seconds to seconds, (ii) ensuring a sufficiently high closed cell count of over 80%, because the openness is usually promoted by the presence of additional phases in polystyrene foams.

The invention therefore relates to a thermoplastic extrusion foam sheet having a thickness in the range of 15 mm to 200 mm and cells having a mean cell size in the range of 20 to 2000 μηι, characterized in that the cell membranes have a fibrous structure with fiber diameters below 1500 nm , loading Preferably, the foam is formed from a polymer matrix which contains at least two incompatible thermoplastic polymers and at least one polymeric compatibilizer and which forms a continuous and a disperse phase, the continuous phase preferably containing one or more styrene polymers and the disperse phase containing at least two polyolefins, preferably in each case consists of these.

In particular, the foam is formed from

A) from 45 to 97.8% by weight of one or more styrene polymers,

B1) from 1 to 25% by weight of one or more polyolefins having a melting point in the range from 105 to 140 ° C,

B2) 1 to 25 wt .-% of one or more polyolefins having a melting point below 105 ° C,

C1) 0, 1 to 20 wt .-% of at least one butadiene and / or isoprene-containing

styrene block copolymer,

C2) 0, 1 to 10 wt .-% of at least one ethylene, butylene and / or propylene-containing styrene block copolymer. The invention further provides a process for producing the extrusion foam sheet according to the invention, comprising: a) heating a mixture of at least two incompatible thermoplastic polymers and one or more polymeric compatibilizers to form a polymer melt having a continuous and a disperse phase, b) the polymer melt with 1 to 12 parts by weight (based on the polymer in the polymer melt (P), which has 100 mass fractions) of a physical blowing agent and c) the foamable polymer melt is foamed into a region of lower pressure to a foam sheet, preferably the temperature of the die lip the slot nozzle is 120 to 170 ° C, the temperature of the polymer melt in the range of 50 to 160 ° C and the pressure in front of the nozzle is greater than 50 bar.

The invention likewise relates to the use of the foam sheets according to the invention as insulating material, structural foam, core material for composite applications, material for energy absorption and / or as material for packaging applications. The foam sheet according to the invention usually shows a progressive pressure behavior, a good damping behavior and a good ductility. It has good insulation properties, good solvent resistance and good heat resistance. It thus combines three important properties in one material and thus makes it possible to use this material universally in a wide variety of applications where the use of different materials specially adapted to the respective application was previously necessary. The foam board according to the invention is accessible without the use of blowing agents that are problematic from an environmental point of view or with respect to the fire protection regulations. In addition, it offers good insulation and mechanical properties at the same time high solvent and heat resistance in spite of low density compared to the extrusion foams of the prior art. The foam sheet according to the invention preferably has a cuboidal basic structure, the thickness being defined as the shortest edge (height). The upper limit of the thickness is preferably 200 mm. The lower limit for the thickness is preferably 15 mm, particularly preferably 20 mm, in particular 25 mm. The foam board according to the invention preferably has cells of average cell size in the range from 20 to 1000 μm, in particular from 50 to 500 μm, the mean cell size being defined in accordance with ASTM D3576-04.

The cell walls have a fibrous structure, as exemplified in FIG. The figure shows an electron micrograph (REM) of Schaumsteg with cell wall. An ESB (energy-selective-backscattered-electron) detector was used (high voltage 1.00 kV). Bright areas are polystyrene, dark areas PE soft phase with clearly recognizable fibril structure. The mean fiber diameters are below 1500 nm, preferably in the range from 10 to 1000 nm, particularly preferably 10 to 500 nm, in particular 20 to 250 nm. The length of the fibrous structure is at least 5 times the average diameter, preferably at least 10 times average diameter, more preferably at least 20 times the mean diameter. The average fiber diameter is determined according to the invention by evaluation of microscopic images of the foam structure (scanning electron microscopy). At least three microscopic images of the cell walls are evaluated. The fibrous appearing structures are analyzed for diameter at least four different positions and the number average is formed. The foam sheet according to the invention is preferably closed-cell, which means according to the invention that the cells, measured according to DIN ISO 4590, are closed to at least 80, in particular to 90 to 100%. The density of the foam board according to the invention is preferably in the range from 20 to 150 g / l, more preferably from 25 to 120 g / l, in particular from 30 to 80 g / l. The cell count is preferably 0.5 to 30 cells, in particular 1 to 20 cells per mm.

In general, the extrusion foam of the invention is formed from a polymer matrix containing a continuous, styrene polymer-rich phase and a discontinuous polyolefin-rich phase.

"Formed from a polymer matrix" means according to the invention that the polymer matrix is the structuring element. The foam can contain other additives besides polymer matrix and blowing agent. All data in% by weight for individual polymers, unless stated otherwise, refer to the entire polymer matrix (= 100% by weight) without additives.

The polymer matrix preferably contains (and consists in particular of)

A) from 45 to 97.8% by weight of at least one styrenic polymer,

B1) from 1 to 25% by weight of at least one polyolefin having a melting point in the range from 105 to 140 ° C,

B2) 1 to 25 wt .-% of at least one polyolefin having a melting point below 105 ° C,

C1) 0, 1 to 25 wt .-% of at least one butadiene and / or isoprene-containing

styrene block copolymer,

C2) 0, 1 to 10 wt .-% of at least one ethylene, butylene, and / or propylene-containing styrene block copolymer.

The polymer matrix preferably contains from 55.0 to 89.9% by weight of one or more styrene polymers.

According to the invention, the term styrene polymer comprises polymers based on styrene and further comonomers, for example, alpha-methylstyrene, acrylonitrile, methyl methacrylate; the minimum styrene content of the styrenic polymer is 90% by weight.

As styrene polymers, preference is given to glassy polystyrene (GPPS), anionically polymerized polystyrene, styrene-α-methylstyrene copolymers, styrene-acrylonitrile copolymers (SAN), acrylonitrile-alpha-methylstyrene copolymers (AMSAN) or mixtures thereof with polyphenylene ether (PPE ) used. In addition, impact modified varieties can thereof, for example, high-impact polystyrene (HIPS), impact polystyrene (A-IPS), acrylonitrile-butadiene-styrene polymers (ABS), methyl acrylate-butadiene-styrene (MBS), acrylonitrile-styrene-acrylic ester (ASA), methyl methacrylate-acrylonitrile Butadiene-styrene (MABS) polymers or mixtures thereof with polyphenylene ether (PPE).

It is also possible to admix polymer recyclates of said thermoplastic polymers, in particular styrene polymers and expandable styrene polymers (EPS), in amounts which do not substantially impair their properties, as a rule in amounts of not more than 50% by weight, in particular in amounts of from 1 to 20% by weight .-% (based on the component A).

Preference is given to polystyrene. Standard polystyrene types are particularly preferred having weight average molecular weights ranging from 120,000 to 300,000 g / mol and a melt volume rate MVR (200 ° C / 5 kg) according to ISO 1 13 in the range of 1 to 10 cm ^3/10 min. for example PS 158 K, 168 N or 148 G of Styrolution GmbH.

As further constituents, the polymer matrix generally contains a polyolefin component B consisting of one or more thermoplastic polyolefins which are incompatible with component A. Preferably, the polyolefin component B is made

B1) 1 to 25 wt .-% (based on the polymer matrix) of one or more polyolefins having a melting point in the range of 105 to 140 ° C and

B2) 1 to 25 wt .-% (based on the polymer matrix) of one or more polyolefins having a melting point below 105 ° C,

The polymer B1) used is preferably a homo- or copolymer of ethene, in particular in combination with propene. Homopolymers used are commercially available polyethylenes, such as PE-LD, PE-LLD, PE-HD. Suitable copolymers include the following systems are suitable: copolymers of ethene and propene (for example Moplen ^® RP220 and RP320 Moplen ^® Basell), copolymers of ethene and vinyl acetate (EVA), copolymers of ethylene and acrylates (EA, such as Surlyn ^® grades 1901 and 2601 (from DuPont) or copolymers of ethylene, butene and acrylates EBA, including Lucofin ^® 1400 HN, 1400 HM from the Lucobit AG). The melt volume index MVI (190 ° C / 2.6 kg) of the polyethylenes is usually in the range of 0.5 to 40 g / 10 min, the density in the range of 0.86 to 0.97 g / cm ³ , preferably in the range from 0.91 to 0.95 g / cm ³ . In addition, mixtures with polyisobutylene (OIB) (eg Oppanol B150 ^® of BASF SE) are used. The polymer B2) used is preferably a copolymer of ethene, for example ethene and octene (EOC, eg ^Engage® , Dow).

The proportion of component B1) in the polymer matrix is preferably 2 to 25% by weight, particularly preferably 5 to 20% by weight. In a preferred embodiment, the proportion of component B2) is from 2 to 25 wt .-%, particularly preferably 5 to 20 wt .-%.

For targeted adjustment of the desired morphology usually at least two different compatibilizers (component C) in amounts of from 0.2 to 35 wt .-%, preferably 0.2 to 5 wt .-%, based on the polymer matrix used.

The compatibilizers lead to improved adhesion between the polyolefin-rich and the polystyrene-rich phase and improve the elasticity of the foam even in small quantities compared to conventional EPS foams.

The component C) preferably consists of

C1) 0, 1 to 25 wt .-% (based on the polymer matrix) of at least one butadiene and / or styrene-isoprene-containing styrene block copolymer and

C2) 0, 1 to 10 wt .-% (based on the polymer matrix) of at least one ethylene, butylene and / or propylene-containing styrene block copolymer.

According to the invention, butadiene-, isoprene-, ethylene-, butylene- or propylene-containing styrene block copolymer means a polymer obtainable by polymerization of these monomers, the polymer then having the corresponding saturated or partially unsaturated structures.

Suitable components (C1) are, for example, unhydrogenated or partially hydrogenated styrene-butadiene or styrene-isoprene block copolymers. The total styrene content is preferably in the range of 40 to 80 wt .-%, particularly preferably in the range of 50 to 70 wt .-% (based on C1).

Suitable styrene-butadiene block copolymers which consist of at least two polystyrene blocks S and at least one styrene-butadiene copolymer block S / B are, for example, star-branched block copolymers, as described in EP-A 0 654 488. The block copolymers used are characterized in that they have at least one hard block having a glass transition temperature of at least 80 ° C. and at least one soft block having a glass transition temperature of at most -20 ° C. The glass transition temperatures of the different blocks are determined according to ASTM D 5026-01 at a frequency of 1 Hz as the maximum of the loss modulus.

Furthermore, block copolymers having at least two hard blocks Si and S ₂ of vinylaromatic monomers having at least one intermediate random soft block B / S of vinylaromatic monomers and diene are suitable, the proportion of hard blocks being more than 40% by weight, based on the total block copolymer and the 1,2-vinyl content in soft block B / S is below 20%, as described in WO 00/58380. Also suitable as compatibilizer (C1) are linear styrene-butadiene block copolymers of the general structure S (S / B) -S with one or more blocks which are located between the two S blocks and have a static styrene / butadiene distribution (S. / B) _r on _d om suitable. Such block copolymers are obtainable by anionic polymerization in a nonpolar solvent with the addition of a polar cosolvent or a potassium salt, as described, for example, in WO 95/35335 and WO 97/40079.

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

Preferred compatibilizers (C1) are styrene-butadiene-styrene (SBS) triblock copolymers having a butadiene content of from 20 to 60% by weight, preferably from 30 to 50% by weight, which may be hydrogenated or unhydrogenated. These are for example under the name Styroflex ^® 2G66, Styrolux ^® 3G55, Styroclear ^® GH62, Kraton ^® D 1 101, Kraton ^® G 1650, Kraton ^® D 1 155, Tuftec ^® H 1043 or Europren ^® SOL 6414 commercially. These are SBS block copolymers with sharp transitions between B and S blocks.

An improvement in compatibility can also be achieved by Teilhydrieren of butadiene, such as Kraton ^® G types. As the component (C2) is styrene-ethylene-butylene block copolymers, for example, linear triblock copolymers / butylene blocks are based on styrene and ethylene (SE / BS), as, under the designation Kraton ^® G1654 from Kraton Polymers GmbH, Eschborn Germany are available. Also suitable are styrene-ethylene / propylene-styrene block copolymers (SEPS), as sold for example under the name Septon ^® 2063 from Kuraray Co. Ltd., Tokyo, Japan.

Particularly preferred as components A) to C) of the polymer matrix are the following materials:

Particularly preferred as component A) is polystyrene.

Particularly preferred as component B1) is polyethylene.

Particularly preferred as component B2) is an ethylene-octene copolymer.

Particularly preferred as component C1) is a styrene-butadiene block copolymer.

Particularly preferred as component C2) is a styrene-ethylene / butylene block copolymer.

The polymer matrix particularly preferably consists of the particularly preferred components.

The polymer matrix preferably contains the stated components in the following proportions: 75 to 95% by weight of component A);

From 2 to 14% by weight of component B1);

From 2 to 14% by weight of component B2);

0.4 to 6 wt .-% of component C1) and

0.4 to 2.5% by weight of component C2).

In a preferred embodiment, the sum of components B1) and B2) is> 15% by weight, wherein the proportion of component B1) must be greater than the proportion of component B2). The extruded foam sheet according to the invention contains, in addition to the polymer matrix, a blowing agent component (T).

The blowing agent component (T) comprises (and preferably consists of (b1) 100-15% by weight, preferably 85-15% by weight, particularly preferably 75-15% by weight, (based on (T)) C0 ₂ ,

(b2) 0-85% by weight, preferably 15-75% by weight, particularly preferably 25-75% by weight, based on T, of one or more, preferably one or two, in particular one, co- Blowing agents from the group of CrC ₄ alcohols, and C

C ₄ -carbonyl compounds, preferably C ₂ -C ₄ -carbonyl compounds, in particular C ₃ -C ₄ -ketones and formates, and

(b3) 0 to 10% by weight, preferably 0 to 5% by weight, particularly preferably 0 to 2% by weight of water (in each case based on T).

(b4) 0 to 10 wt .-%, preferably 0 to 5 wt .-% nitrogen (based on T).

The blowing agent component (T) used is preferably mixtures of CO 2 and one or two co-blowing agents. Particularly preferred are binary mixtures. Preferred alcohols are methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methylpropanol and tert-butanol. Particularly preferred is ethanol.

CrC ₄ -Carbonyl compounds are ketones, aldehydes, carboxylic esters carboxylic acid amides having 1 to 4 carbon atoms.

Suitable ketones are acetone and methyl ethyl ketone, preferred formates are methyl formate, ethyl formate, n-propyl formate and i-propyl formate. Preference is given to acetone.

In the co-propellants b2) and in the carbon dioxide b1) water b3) may be contained. Water enters the blowing agent component T mainly through the use of technical alcohols and ketones. In a preferred embodiment, a blowing agent component T is used which has a water content b3) of not more than 10% by weight, preferably not more than 5% by weight, more preferably not more than 4% by weight and especially preferably not more than 2% by weight (in each case based on (T).

In a further preferred embodiment, the blowing agent component is substantially anhydrous. Particular preference is given to mixtures of carbon dioxide and ethanol, carbon dioxide and acetone, carbon dioxide and methyl formate, and also carbon dioxide and mixtures of ethanol and acetone in the abovementioned mixing ratios.

The blowing agent component T is added to the polymer melt in a proportion of a total of 1 to 12 parts by mass, preferably 1 to 8 and particularly preferably 1 to 5 parts by mass (in each case based on the polymer matrix P, which has 100 parts by mass). A suitable composition of the blowing agent component T contains from 15 to 100% by weight of component b1) and from 0 to 85% by weight of component b2). Preferably, the proportion of component b1) based on P less than 6 parts by mass and the proportion of component b2) based on P less than 2 parts by mass and the total content of components b1) and b2) based on P less than 8 parts by mass. More preferably, the proportion of component b1) based on P less than 4.5 parts by mass and the proportion of component b2) based on P less than 4 parts by mass. Propellant levels based on the polymer matrix are the initial levels achieved in the production of the extrusion foam panels. It is known to the person skilled in the art that these values decrease due to outdiffusion of the blowing agent from the finished foam board. In one embodiment, the polymer matrix P contains additives, ie auxiliaries and / or additives. Suitable auxiliaries and additives are known to the person skilled in the art.

In a preferred embodiment, at least one nucleating agent is added to the polymer matrix P. As nucleating agents, finely divided, inorganic solids such as talc, metal oxides, silicates or polyethylene waxes in amounts of generally 0.1 to 10 parts by mass, preferably 0.1 to 3 parts by mass, particularly preferably 1 to 1.5 mass parts, based on 100 parts by mass P, be used. The mean particle diameter of the nucleating agent is generally in the range from 0.01 to 100 μm, preferably from 1 to 60 μm. A particularly preferred nucleating agent is talc, for example from Luzenac Pharma. The nucleating agent may be added by methods known to those skilled in the art.

If desired, one or more additives such as nucleating agents, fillers (for example mineral fillers such as glass fibers), plasticizers, flame retardants, IR absorbers such as carbon black or graphite, aluminum powder and titanium dioxide, soluble and insoluble dyes and pigments may be added. Preferred additives are graphite and carbon black. Particularly preferably, graphite is added in amounts of generally 0.05 to 25 parts by mass, more preferably in amounts of 2 to 8 parts by mass, based on 100 parts by mass of P. Suitable particle sizes for the graphite used are in the range of 1 to 50 μηι, preferably in the range of 2 to 10 μηι. Due to fire safety regulations in the construction industry and other industries, one or more flame retardants are preferably added. Suitable flame retardants are, for example, bromine and / or phosphorus compounds such as tetrabromobisphenol A, brominated polystyrene oligomers, brominated styrene-butadiene copolymers, tetrabromobisphenol A diallyl ether, expandable graphite, red phosphorus, triphenyl phosphate and 9,10-dihydro-9-oxa-10. phosphaphenanthrene-10-oxide. Another suitable flame retardant is, for example, hexabromocyclododecane (HBCD), in particular the industrial products which essentially contain the α, β and γ isomers and preferably an addition of dicumyl (2,3-dimethyl-2,3-diphenylbutane) as synergists contain.

Particularly preferred for thermal insulation is the addition of graphite, carbon black, aluminum powder or an IR dye (e.g., indoaniline dyes, oxonol dyes or anthraquinone dyes).

In general, the dyes and pigments are added in amounts ranging from 0.01 to 30 parts by mass, preferably in the range from 1 to 5 parts by mass, based on 100 parts by mass (P). For the homogeneous and microdispersed distribution of the pigments in the polymer melt, it may be expedient in particular for polar pigments to use a dispersing aid, e.g. Organosilane, epoxy group-containing polymers or maleic anhydride-grafted styrenic polymers to use.

The total amount of additives is generally 0 to 30 parts by mass, preferably 0 to 20 parts by mass, based on the polymers (P), which have 100 parts by mass.

In a preferred embodiment, the total amount of additives is 0.5 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, based on the polymers (P), which have 100 parts by mass.

In a further embodiment, the foam sheet according to the invention contains no additives.

The extrusion foam sheet according to the invention is obtainable by

(a) heating a polymer component P which is formed from a mixture of at least two incompatible thermoplastic polymers and one or more polymeric compatibilizers, preferably a mixture of one or more styrene polymers, one or more polyolefins and one or more polymeric compatibilizers, more preferably A) from 45 to 97.8% by weight of one or more styrene polymers,

B2) from 1 to 25% by weight of one or more polyolefins having a melting point below 105 ° C.,

C1) 0, 1 to 20 wt .-% of at least one butadiene and / or isoprene-containing styrene block copolymer,

C2) 0.1 to 10% by weight of at least one ethylene, butylene and / or propylene-containing styrene block copolymer,

(b) introducing from 1 to 12 parts by mass (based on 100 parts by mass P) of a blowing agent component T, containing b1) 15 to 100% by weight (based on T) carbon dioxide and b2) 0 to 85% by weight (based on T ) one or more co-blowing agents selected from the group consisting of CC ₄ alcohols and CC ₄ - carbonyl compounds in the polymer melt to form a foamable melt,

Extrusion of the foamable melt into a region of lower pressure with foaming to the extrusion foam, (d) optionally adding additives to the polymer component P or in at least one of the steps a), b) and / or c).

In step (a) of the process, the polymer component P is heated to obtain a polymer melt. In the context of the invention, the formation of a polymer melt is understood to mean a plasticization of the polymer component P in a broader sense, i. the conversion of the solid components of the polymer component P into a deformable or flowable state. For this it is necessary that the polymer component P is heated to a temperature above the melting or glass transition temperature. Suitable temperatures are generally at least 140.degree. C., preferably 150 to 260.degree. C., particularly preferably 160 to 220.degree.

The heating of the polymer component P (step (a) of the process of the invention) may be accomplished by any means known in the art, such as by means of an extruder or a mixer (eg, a kneader). Preference is given to the use of Aufschmelzextrudern (primary extruders). Step (a) of the invention The process according to the invention can be carried out continuously or batchwise, with a continuous procedure being preferred.

Step (b) of the process according to the invention comprises introducing the above-described blowing agent component T into the polymer melt prepared in step (a) to form a foamable melt.

The blowing agent component T can be introduced into a molten polymer component P by any method known to those skilled in the art. For example, extruders or mixers (e.g., kneaders) are suitable. In a preferred embodiment, the propellant is mixed with the molten polymer component P under elevated pressure. The pressure must be so high that substantially prevents foaming of the molten polymer material and a homogeneous distribution of the blowing agent component T in the molten polymer component P is achieved. Suitable pressures are 50 to 500 bar (absolute), preferably 100 to 300 bar (absolute), more preferably 150 to 250 bar (absolute). The temperature in step (b) of the process according to the invention must be selected such that the polymeric material is in the molten state. For this it is necessary that the polymer component P is heated to a temperature above the melting or glass transition temperature. Suitable temperatures are generally at least 140 ° C, preferably 150 to 260 ° C, particularly preferably 160 to 220 ° C.

The blowing agent can be added in the melt extruder (primary extruder) or in a downstream step.

In a preferred embodiment, the production of the foamable polymer melt is carried out in XPS extruders known to the person skilled in the art, for example via a tandem structure consisting of a melting extruder (primary extruder) and a cooling extruder (secondary extruder). The process can be carried out continuously and batchwise, wherein the polymer component P is melted in the primary extruder (step (a)) and the addition of the blowing agent (step (b)) to form a foamable melt also takes place in the primary extruder.

Thereafter, the foamable melt provided with blowing agent in the secondary extruder is cooled to a suitable temperature for foaming of 50 to 160 ° C, preferably to a temperature of 80 to 140 ° C.

In one embodiment, additives, ie auxiliaries and / or additives, are added to the polymer component P before the process and / or in at least one of the steps a), b) and / or c) are carried out. Suitable auxiliaries and additives are those described above. Step (c) of the process of the invention comprises foaming the foamable melt to obtain an extrusion foam. The melt is to promote by a suitable device, such as a nozzle plate. The nozzle plate is heated at least to the temperature of the blowing agent-containing polymer melt. Preferably, the temperature of the nozzle plate is 50 to 180 ° C. More preferably, the temperature of the nozzle plate is 120 to 170 ° C.

The blowing agent-containing polymer melt is transferred through the nozzle plate in a region in which a lower pressure prevails than in the region in which the foamable melt is held prior to extrusion through the nozzle plate. The lower pressure may be superatmospheric or subatmospheric. Preferably, the extrusion is in a region of atmospheric pressure.

Step (c) is also conducted at a temperature at which the polymeric material to be foamed is in a molten state, generally at temperatures of 50 to 160 ° C, preferably 80 to 140 ° C, more preferably 110 to 140 ° C , Characterized in that the blowing agent-containing polymer melt is transferred in step (c) in a region in which a lower pressure prevails, the blowing agent is converted into the gaseous state. Due to the large volume increase, the polymer melt is expanded and foamed. In a variant of the process according to the invention, first of all a masterbatch of the components A, B, C and, if appropriate, auxiliaries and additives is prepared, which is mixed with further styrene polymer before or during step a) of the process. The geometric shape of the cross section of the extruded foam sheet obtainable by the process according to the invention is essentially determined by the choice of the nozzle plate and, if necessary, by suitable downstream devices such as plate calibrations, roller conveyors or strip drawers and is freely selectable. The extrusion foam sheets obtainable by the process according to the invention preferably have a rectangular cross section. The thickness of the extrusion foams is determined by the height of the Düsenplattenschlit- zes. The width of the extrusion foams is determined by the width of the nozzle plate slot. The length of the extruded foam parts is determined in a subsequent step by known to those skilled in the art such as bonding, welding, sawing and cutting. In particular, Preferred are extrusion foam sheet having a geometry in which the dimension of the thickness (height) is small compared with the dimension of the width and the dimension of the length of the molding. The invention also provides the use of the extrusion foam sheets according to the invention as insulating material in particular in the construction industry, underground and above ground, eg for foundations, walls, floors and roofs. Preference is likewise given to use as structural foam, in particular for lightweight construction applications and as core material for composite applications.

The invention further relates to the use of the material for energy absorption, for example in the automotive industry for automotive applications, and in the packaging industry for packaging applications, such as electronic goods or food.

The invention is further illustrated by the following examples without being limited thereto.

Examples

General working instructions

The foam boards according to the invention were produced on a tandem extrusion line. The polymers used were continuously fed together with talc to a melt-down extruder. The total throughput of the polymers was 12 kg / h. The propellants (C0 ₂ , ethanol) were fed continuously through an injection opening introduced into the melting extruder. The propellant-containing melt was cooled in a subsequent cooling extruder and extruded through a slot die (width 25 mm, height 0.8 mm). The intumescent melt was withdrawn without calibration via a roller belt. The extruded cross sections had a height of about 15 mm and a width of about 80 mm at a typical density of 45 g / l.

Polystyrene 158K (Styrolution GmbH) was used as the reference polymer in the production of the foam board and was usually processed to densities of approx. 45 g / l on the tandem extrusion line. The processing-related density range extended over 25 to 150 g / l.

For the production of the foam board according to the invention, three different ways were chosen (for composition of the materials and masterbatch, see Tables 1 and 2): V1) addition of a degassed, previously pentane-containing masterbatch to polystyrene V2) processing of different masterbatches with and without addition of further PS,

V3) Production of the blends on the extruder in one step.

There were obtained closed-cell foam sheets with densities of 25-150 g / l, which had a smooth shiny foam skin surface. As a rule, materials with a density of 40 to 45 g / l were produced.

If the process parameters are not selected correctly and / or in the case of systems without block copolymers / phase mediators, there is an increased off-set of the systems listed under V4. These include u.a. the correct choice of melt and die temperatures in the extrusion, the compatibilization of the polyolefins B) by sufficiently high levels of C) and a sufficiently high nozzle pressure, which is above the saturation pressure of the blowing agent (typically> 50 bar).

Subsequently, specimens were cut out of the foam sheets obtained in experiments with masterbatch No. 2, and the modulus of elasticity according to ISO 844 and the progressive damping behavior over ISO 3386-1 at 10% and 50% compressive stress were determined. The solvent resistance was determined at 20 ° C. with purified puriss solvents by completely immersing test specimens measuring 50 by 50 mm in the solvent and completely wetting the foam sample with the solvent. The bending properties were qualitatively determined on the basis of the slightly different foam geometries. The foam extrudate with foaming skin was subjected to a three-point bending load and the maximum deflection was evaluated comparatively until fracture. The results of the tests are shown in the following tables. Starting Materials:

Component A

A) polystyrene (having a melt viscosity index MVI 200 ° C / 5kg) of 2.9 cm ^3/10 min (PS 158K Styrolution GmbH, Mw = 280,000 g / mol, viscosity number VN

98 ml / g)

Component B: B1) Polyethylene LLDPE (LL6201 XV, Exxon Mobile, density 0.926 g / l, MVI = 50 g / 10 min, melting point 123 ° C) B2) ethylene-octene copolymer (Dow Engage® 8402, density 0.902 g / l, MVI = 30 g / 10 min, melting point 94 ° C.)

Component C:

C1) Styroflex® 2G66, thermoplastic elastic styrene-butadiene block copolymer (S-TPE) from Styrolution GmbH

C2) Kraton G 1654, styrene-ethylene-butylene block copolymer from Kraton Polymers LLC

Component D:

D1) Talc (Talc IT Extra)

V1) Addition of a degassed, previously pentane-containing masterbatch to polystyrene

In process variant V1, a pentane-containing masterbatch was first degassed and subsequently foamed on the tandem foam extrusion plant with and without the addition of PS. The material composition is given in Table 1. The composition is given in parts by weight, all polymers add up to 100 parts by weight, the blowing agent and the nucleating agent (component D.1) behave additively. In all cases, 35 parts by weight of C0 ₂ and 2.5 parts by weight of ethanol were used for the foam processing.

Table 1: Composition of the degassed masterbatch No. 1

Masterbatch no.

1

Component A1) (parts by weight) 77.0

Component B1) (parts by weight) 10.2

Component B2) (parts by weight) 9.4

Component C1) (parts by weight) 1, 7

Component C2) (parts by weight) 1, 7

Component D1) (parts by weight) 0.4 Table 2 Composition of the foams

Table 3: Printing properties of the foams

Pressure modulus according to ISO 381

Compressive strengths at different compressions in DIN 3386-1

Closed cell according to DIN ISO

It turns out that even slight additions of the masterbatch 1 cause a significant improvement in the damping behavior. The increase in compressive strength between 10 and 50% compression at blends from 25 parts by weight of the masterbatch is much more pronounced than with pure PS, which shows almost no increase (inelastic deformation of the pure PS foam). Table 4 Bending properties of the foams

qualitative assessment of flexibility ('++' = very good, '+' = good, 'o' = medium, '-' = low, '- very low)

Table 5 Chemical resistance of the foams

***** Assessment of chemical resistance ('++' = very good - does not dissolve after 24 h, '+' = good - dissolves partially within 24 h, 'o' = medium - dissolves within 1 h ) ,, '-' = low - dissolves within 10 min, '- -' = very low - dissolves immediately) V2) Processing of different masterbatches with and without the addition of additional PS

In process variant V2, a masterbatch was first prepared, which was subsequently foamed on the tandem foam extrusion plant. The material composition is given in Table 6. The composition is given in parts by weight, all polymers add up to 100 parts by weight, the blowing agent and the nucleating agent (component D.1) behave additively. In all cases 3.5 parts by weight of C0 ₂ and 2.5 weight portions of ethanol (Table 7) were used for foam processing. Table 6 Composition of Masterbatches Nos. 2 to 4

Masterbatch no.

Table 7 Composition of the foams

Table 8 Bending properties of the foams

qualitative assessment of flexibility ('++' = very good, '+' = good, 'o' = medium, '-' = low, '- -' = very low) Table 9 Chemical resistance of the foams

Assessment of chemical resistance C ++ '= very good - does not dissolve after 24 h,' + '= good - dissolves partially within 24 h,' o '= medium - dissolves within 1 h)' '-' = low - dissolves within 10 min, '- -' = very low - dissolves immediately)

V3) Production of the blends on the extruder in one step

In process variant V3 all materials were premixed and added together to the meltdown extruder, compounded and then foamed directly on the tandem foam extrusion line. The material composition is given in Table 10. The composition is given in parts by weight, all polymers add up to 100 parts by weight, the blowing agent and the nucleating agent (component D.1) behave additively. In all cases, 3 parts by weight of C0 ₂ and 2.5 parts by weight of ethanol were used for foam processing (Table 1 1). Table 10 Composition of Masterbatch No. 5

Masterbatch no.

5

Component A1) (parts by weight) 76.8

Component B1) (parts by weight) 5.0

Component B2) (parts by weight) 14.6

Component C1) (parts by weight) 1, 8

Component C2) (parts by weight) 1, 8

Component D1) (parts by weight) 0.5 Table 1 1 Composition of the foams

Table 12 Bending properties of the foams

qualitative assessment of flexibility C ++ '= very good,' + '= good,' o '= medium,' - 'ring,' - - '= very low)

Table 13 Chemical resistance of the foams

V4) further comparative examples

In the comparative examples listed in V4, a pentane-containing masterbatch was first degassed and subsequently foamed on the tandem foam extrusion plant with or without addition of PS. The material compositions are given in Table 1. The composition is given in parts by weight, all polymers add up to 100 parts by weight, the blowing agent and the nucleating agent (component D1) behave additively. In all cases used for the foam processing 3.5 parts by weight C0 ₂ and 2.5 parts by weight of ethanol.

Table 14 Composition of Degassed Masterbatches # 1 and # 6

Table 15 Composition of the foams

Table 16 Openness of the foams

*** Closed cell according to DIN ISO Comparative Examples V2 and V3 are taken from US 6,093,752 and WO 98/58991. It turns out that both the correct choice of material composition and the corresponding process parameters are important.

Claims

claims

Thermoplastic extrusion foam board with a thickness in the range of 15 mm to 200 mm and cells with a mean cell size in the range of 20 to 2000 μηι, characterized in that the cell membranes have a fibrous structure with fiber diameters below 1500 nm.

An extrusion foam sheet according to claim 1, wherein the foam is formed from a polymer matrix containing at least two incompatible thermoplastic polymers and at least one polymeric compatibilizer and forming a continuous and a disperse phase and preferably wherein the continuous phase comprises one or more styrenic polymers and the disperse phase or more polyolefins.

An extrusion foam sheet according to claim 1 or 2, wherein the foam comprises a polymer matrix containing

A) from 45 to 97.8% by weight of one or more styrene polymers,

C1) 0.1 to 20% by weight of at least one butadiene and / or isoprene-containing styrene block copolymer,

C2) contains 0.1 to 10 wt .-% of at least one ethylene, butylene and / or propylene-containing styrene block .. ..

An extrusion foam sheet according to claim 3, wherein the polymer matrix is composed of components A) to C2).

5. extrusion foam sheet according to claim 3 or 4, wherein the proportion of component B2) 2 to 25 wt .-% (based on the polymer matrix).

6. An extrusion foam sheet according to any one of claims 1 to 5, which has a density in the range of 20 to 150 g / l.

7. extrusion foam sheet according to any one of claims 1 to 6, wherein the cells measured according to DIN ISO 4590 are at least 80% closed.

An extrusion foam sheet according to any one of claims 2 to 7, wherein the average diameter of the dispersed phase is in the range of 1 to 1500 nm.

9. A process for producing the extrusion foam sheet according to any one of claims 1 to 8, comprising heating a mixture of at least two incompatible thermoplastic polymers and one or more polymeric compatibilizers to form a polymer melt having a continuous and a disperse phase, the polymer melt having 1 to 12 Parts by weight (based on the sum of the polymers in the polymer melt) of a physical blowing agent impregnated and the foamable polymer melt foamed into a region of lower pressure to a foam sheet extruded, preferably wherein the temperature of the die lip of the slot nozzle is greater than 120 ° C, the temperature of Polymer melt in the range of 50 to 160 ° C and the pressure in front of the nozzle is greater than 50 bar. 10. The method according to claim 9, wherein a masterbatch is used to prepare the polymer blend.

1 1. A method according to claim 9 or 10, wherein one or more of the polymers used are recyclates.

12. The method according to any one of claims 9 to 1 1, wherein the physical blowing agent (T) of

(b1) 100-15% by weight, preferably 85-15% by weight, particularly preferably 75-15% by weight, (based on (T)) C0 ₂ ,

(b2) 0-85% by weight, preferably 15-75% by weight, particularly preferably 25-75% by weight, based on T, of one or more, preferably one or two, in particular one, Propellants from the group of CC ₄ - alcohols, and CC ₄ -carbonyl compounds, preferably C ₂ -C ₄ -

Carbonyl compounds, in particular C ₃ -C ₄ ketones and formates, and (b3) 0 to 10 wt .-%, preferably 0 to 5 wt .-%, particularly preferably 0 to 0.2 wt .-% water (in each case based on T).

13. The method according to claim 12, wherein the blowing agent used is a mixture of carbon dioxide and ethanol, carbon dioxide and acetone, carbon dioxide and methyl formate or carbon dioxide, ethanol and acetone.

Use of an extrusion foam sheet according to any one of claims 1 to 8 as an insulating material, structural foam material, composite core material, energy absorption material and / or packaging application material.

15. Use according to claim 14 in the construction industry, automotive industry and packaging industry.