JP5726735B2 - Expandable thermoplastic polymer blend - Google Patents

Description

  The present invention relates to an expandable thermoplastic polymer blend, pellets obtained from the polymer blend, a process for producing the polymer blend and a foam.

  Methods for producing expandable styrene polymers such as expandable polystyrene (EPS) by suspension polymerization have been known for some time. The disadvantage of this method is that a large amount of wastewater is generated and must be disposed of. The polymer needs to be dried to remove internal water. Also, suspension polymerization reactions generally broaden the bead size distribution, which necessitates the use of complex sieves on the various bead fractions.

  Expanded and expandable styrene polymers can also be produced by extrusion. In this case, the foaming agent is introduced, for example, by mixing into a polymer melt, conveyed through a die plate, and pelletized to obtain particulate or elongated pellets (Patent Document 1 (US-A-3817669), Patent Document 2 (GB-A-1062307), Patent Document 3 (EP-B0126459), Patent Document 4 (US-A-5000891)).

  Patent Document 5 (EP-A 668139) describes a method for producing expandable polystyrene pellets (EPS), in which a melt containing a foaming agent is produced using a static mixer in a dispersion, maintenance and cooling stage, and then A manufacturing method for pelletizing is described. Cooling the melt to a temperature several degrees above the freezing point requires a large amount of heat consumption.

  Various pelletization methods have been proposed for the purpose of substantially avoiding foaming after extrusion, and examples thereof include underwater pelletization (Patent Document 6 (EP-A305862)), spray mist (Patent Document 7 (WO03 / 053651)). )) Or nebulization (Patent Document 8 (US-A-6093750)).

  Critical factors to obtain ideal thermal insulation and good surface of the foam product are the number of cells and the cell structure formed during foaming of the expandable styrene polymer (EPS). EPS pellets produced by extrusion usually cannot be foamed to obtain a foam with an ideal cell structure.

  Patent Document 7 (WO94 / 25516), Patent Document 8 (EP-A682077), Patent Document 9 (DE-A19710442) and Patent Document 10 (EP-A0872513) describe foamable rubber-modified styrene polymers for elastic polystyrene foam. Have been described.

  Patent Document 11 (WO2005 / 06652) describes a molding foam molding having a density of 10 to 100 g / l obtained by fusing pre-foamed foam beads composed of foamable thermoplastic polymer pellets, Molded foam moldings comprising 5 to 100% by weight of styrene copolymer A), 0 to 95% by weight of polystyrene B), 0 to 95% by weight of thermoplastic polymer C) other than B) As well as a method for producing the foamable thermoplastic polymer pellets. For example, styrene-acrylonitrile copolymer (SAN) is described as styrene copolymer A).

US-A-3817669 GB-A-1062307 EP-B-0126459 US-A-5000891 EP-A668139 EP-A305862 WO94 / 25516 EP-A682077 DE-A 19710442 EP-A0872513 WO2005 / 066652

  When known blends are used with a relatively high content of rubber-modified styrene polymer, the product is usually simply a relatively dense foam. The object of the present invention is to make it possible to use such blends to provide low density foams which are easily obtained and have good processability.

  It has been found that when the underlying foamable thermoplastic polymer pellets comprise polyphenylene ether, the moldable foam and the molded bodies produced therefrom are obtained with particularly advantageous properties.

The present invention
Polystyrene P1,
An elastic block copolymer P2 composed of at least one aromatic vinyl monomer and at least one diene monomer;
Polyphenylene ether P3 (in the form of a material blended with foamable polystyrene if necessary),
Provided is a foamable thermoplastic polymer blend characterized in that the content of component P2 is more than 4.5% by mass with respect to the total of P1, P2 and P3.

  The present invention also provides polymer pellets obtained from the polymer blends of the present invention and methods of using the corresponding polymer pellets in moldable foams and moldable foam molded articles.

  The moldable foam molded article of the present invention has a high solvent resistance, a high resistance to temperature changes, a high mechanical rigidity, a good foaming maintenance function, and a good workability.

In a preferred embodiment, the polymer blend comprises more than 4.5% P2 by weight based on the total of P1, P2 and P3. In a particularly preferred embodiment, the polymer blend is based on the whole of P1, P2 and P3:
93 to 41% by mass of P1,
5-45% by weight, in particular at least 5% by weight, preferably at least 10% by weight of P2,
2-14 mass% P3,
including.

  The polystyrene P1 used can be high-impact polystyrene (HIPS) or glass transparent polystyrene (GPPS) polymerized by the free radical method, anion-polymerized polystyrene (APS), or anion-polymerized high-impact polystyrene (AIPS), for example. Is included.

  In particularly preferred embodiments, for example, GPPS or high impact polystyrene (HIPS) or a mixture of GPPS and HIPS can be used.

  The elastic block copolymer P2 preferably forms at least one block A forming a hard phase and incorporating polymerized units of an aromatic vinyl monomer, and / or forming a first elastic (soft) phase and a diene. At least one block B containing monomers and at least one elastic block B / A forming a soft phase and incorporating polymerized units of an aromatic vinyl monomer and a diene, the glass transition temperature Tg of block A being 25 ° C. The glass transition temperature Tg of the blocks B and B / A is less than 25 ° C., and the volume ratio of the phase of the block A to the block B / A is 1 to 1. 40% by volume, and the mass proportion of diene is selected to be less than 50% by mass. Suitable block copolymers are described, for example, in Patent Document 12 (WO-A-95 / 35335).

  A method for obtaining this type of elastic block copolymer uses the above parameters to form a soft phase from a random copolymer of aromatic vinyl and diene; a random copolymer of aromatic vinyl compound and diene is: Obtained by polymerization in the presence of a polar co-solvent.

Preferred block copolymers can be represented, for example, by one of general formulas 1-11:
(1) (AB / A) n; (2) (AB / A) n-A; (3) B / A- (AB / A) n; (4) X-[(A -B / A) n] m + I; (5) X-[(B / AA) n] m + I; (6) X-[(AB / A) n-A] m + I; (7) X- [(B / A−A) n−B / A] m + I; (8) Y − [(A−B / A) n] m + I; (9) Y − [(B / A−A) n] m + I; (10) Y-[(AB / A) n-A] m + I; (11) Y-[(B / AA) n-B / A] m + I;
A is an aromatic vinyl block,
B / A is a soft phase, that is, a block composed of a random arrangement of diene units and aromatic vinyl units,
X is an n-functional initiator group;
Y is a group of m-functional coupling agent;
m and n are natural numbers of 1-10.

  Preferably, general formulas AB / AA, X-[-B / AA] 2, and Y-[-B / AA] 2 (the definitions of the abbreviations are as described above). Among them, it is one block copolymer, and the soft phase is particularly preferably a block (12) (B / A) 1- (B / A) 2; (13) (B / A) 1- (B / A) ) 2- (B / A) 1 or (14) (B / A) 1- (B / A) 2- (B / A) 3 further divided into block copolymers, each block B These aromatic vinyl / diene ratios at / A are different or vary continuously within the block within the limits (B / A) 1 (B / A) 2, and the glass transition temperature Tg of each sub-block. Is a block copolymer having a temperature of less than 250 ° C.

  Likewise preferred are block copolymers having a plurality of blocks B / A and / or A having different molar masses in each molecule.

  It is equally possible for block B to be present instead of block A consisting only of aromatic vinyl units, since the overall important element is simply to form an elastic block copolymer.

  Examples of such copolymer structures are (15) to (18): (15) B- (B / A); (16) (B / A) -B- (B / A); ) (B / A) 1-B- (B / A) 2; (18) B- (B / A) 1- (B / A) 2.

  In the present invention, styrene, α-methylstyrene, vinyltoluene and mixtures of these compounds are preferred aromatic vinyl compounds. Preferred dienes are butadiene and isoprene, as well as piperylene, 1-phenylbutadiene and mixtures of these compounds.

  A particularly preferred monomer combination is butadiene and styrene. All of the mass and volume values below are based on this combination; when using technical equivalents of styrene and butadiene, the values require a corresponding recalculation if necessary.

  The B / A block is composed of about 75 to 30% by mass of styrene and 25 to 70% by mass of butadiene. It is particularly preferred that the soft phase has a proportion of 35 to 70% butadiene and a proportion of 65 to 30% styrene.

  In the case of the styrene / butadiene monomer combination, the mass proportion of diene in the entire block copolymer is 15 to 65 mass%, and the mass proportion of the aromatic vinyl component is correspondingly 85 to 35 mass%. Particularly preferred is a butadiene-styrene block copolymer having a monomer composition of 25 to 60% by mass of a diene and 75 to 40% by mass of an aromatic vinyl compound.

  The block copolymer is preferably produced by anionic polymerization in a nonpolar solvent with the addition of a polar cosolvent. The solvent used preferably includes an aliphatic hydrocarbon such as cyclohexane or methylcyclohexane. Polar aprotic compounds such as ethers and tertiary amines are preferred as Lewis bases. Examples of particularly effective ethers are tetrahydrofuran and aliphatic polyethers such as diethylene glycol dimethyl ether. Listed tertiary amines are tributylamine and pyridine. A small amount, eg 0.5-5% by volume, of a polar cosolvent is added to the nonpolar solvent. Particularly preferred is 0.1 to 0.3% by volume of tetrahydrofuran. Experiments have shown that an amount of about 0.2% by volume is appropriate in many instances.

  Depending on the amount of Lewis base added and its structure, the copolymerization parameters and the proportion of 1,2 and 1,4 bonds of diene units are determined. For example, the polymer has 15-40% 1,2 bonds and 85-60% 1,4 bonds based on all diene units.

  The anionic polymerization reaction is preferably initiated by an organometallic compound. Preferred are alkali metal compounds, particularly lithium compounds. Examples of initiators are methyl lithium, ethyl lithium, propyl lithium, n-butyl lithium, sec-butyl lithium, and tert-butyl lithium. The organometallic compound is added as a solution dissolved in a chemically inert hydrocarbon. The amount added depends on the molecular weight of the desired polymer, but is generally in the range of 0.002 to 5 mol% with respect to the monomer.

  The polymerization temperature may be 0 to 130 ° C.

  Preferably the temperature range is 30-100 ° C.

  The volume fraction of the soft phase in the solid is critical to the mechanical properties.

  The volume ratio of the soft phase composed of the diene sequence and the aromatic vinyl sequence is 60 to 95%, preferably 70 to 90%, particularly preferably 80 to 90%. The block A produced from the aromatic vinyl monomer forms a hard phase, the volume proportion of which is 5 to 40%, preferably 10 to 30%, particularly preferably 10 to 20%.

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

  The proportion of the aromatic vinyl block can be measured by precipitation and weighing after osmium decomposition of the polydiene moiety.

  If the polymerization can always continue until completion, the phase ratio found in the polymer can be calculated from the amount of monomer used.

  In the present invention, the block copolymer is obtained from the volume percentage of the soft phase formed from the B / A block and the proportion of diene units in the soft phase (25 to 70% by weight for the styrene / butadiene combination). Clearly defined by the ratio

  The glass transition temperature (Tg) is affected by the random incorporation of the aromatic vinyl compound into the soft phase of the block copolymer and the use of a Lewis base during the polymerization reaction. Typical glass transition temperatures are -50 to + 250 ° C, preferably -50 to + 50 ° C.

  Here, the molar mass of the block A is generally 1000 to 200000, preferably 3000 to 80000 [g / mol]. The A blocks in a molecule may have different molar masses.

  The molar mass of block B / A is 2000-250,000 [g / mol] normally, and a preferable value is 5000-150,000 [g / mol].

  The block B / A, like the block A, may have different molar mass values in one molecule.

  Preferred polymer structures are AB / AA, X-[-B / AA] 2, and Y-[-B / AA] 2, where the random block B / A is itself May have subdivisions into blocks B1 / A1-B2 / A2-B3 / A3 -...). The random block is preferably composed of 2 to 15 random sub-blocks, particularly preferably 3 to 10 sub-blocks. Dividing the random block B / A into the maximum number of random blocks Bn / An has the following decisive advantages. That is, the entire B / A block behaves as a virtually complete random polymer, even with sub-block Bn / An composition gradients that are difficult to avoid in anionic polymerization under industrial conditions. It is therefore clearly possible to add less than the theoretical amount of Lewis base, which increases the 1,4-diene bonds, lowers the glass transition temperature Tg, and reduces the sensitivity of the polymer to crosslinking. Some of the sub-blocks may have a high diene fraction.

  The mass ratio formed by the diene is preferably 25 to 70% with respect to the total mass including the aromatic vinyl. Block A can then be polymerized to that material by the addition of aromatic vinyl. Alternatively, the required polymer blocks can be linked together using a coupling reaction. In the case of a bifunctional initiator, the B / A block is formed first and then the A block is formed.

The molar mass (mass average Mw) of the polyphenylene ether P3 used is generally 10,000 to 80000 g / mol, preferably 20000 to 60000 g / mol. This is 0.2-0.9 dl / g, preferably 0.35-0.8, in particular 0.45-0.6, as measured with a 0.5% strength by weight chloroform solution at 25 ° C. according to DIN 53726. This corresponds to the reduced specific viscosity (η _red ). A particularly suitable material system is the product Noryl 8890C sold by GE Plastics (SABIC).

Particularly preferred polyphenylene ethers are those of the formula (—Ar—R ₁ R ₂ R ₃ R ₄ —O—)
(However,
Ar is an aryl group,
R ₁ , R ₂ , R ₃ and R ₄ are, independently of one another, monovalent substituents, in particular hydrogen, halide, in particular chlorine and bromine, alkyl, in particular linear chains having 1 to 18 carbon atoms. Alkyl groups such as methyl, ethyl, lauryl, stearyl; alkoxy, especially methoxy and ethoxy. )
It has a repeating unit represented by

  A homopolymer having a single repeating unit of the above formula can be used, and a copolymer using a combination of two or more repeating units can also be used.

  Suitable polyphenylene ethers are preferably prepared by oxidative coupling of o-2 substituted phenols. Examples of substituents are halogen atoms such as chlorine or bromine, alkyl groups having 1 to 4 carbon atoms (preferably not having a tertiary hydrogen atom at the α-position), for example, methyl, ethyl, propyl Or it is a butyl group. Similarly, the alkyl group may have a substituent by a halogen atom such as chlorine or bromine or a hydroxyl group. Other examples of substituents are alkoxy groups, preferably alkoxy groups having 4 or less carbon atoms, or phenyl groups optionally substituted by halogen atoms and / or alkyl groups. Various phenolic copolymers are equally suitable, an example being a copolymer of 2,6-dimethylphenol and 2,3,6-trimethylphenol. Of course, mixtures of various polyphenylene ethers can also be used.

  Preference is given to using polyphenylene ethers which are compatible with aromatic vinyl polymers, ie completely or very substantially soluble in these polymers (A. Noshay, Block Copolymers 8-10, Academic Press, 1977 and Polymer-Polymer Miscibility, 1979, 117-189).

  Examples of polyphenylene ether are poly (2,6-dilauryl-1,4-phenylene ether), poly (2,6-diphenyl-1,4-phenylene ether), poly (2,6-dimethoxy-1,4-phenylene ether). Phenylene ether), poly (2,6-diethoxy-1,4-phenylene ether), poly (2-methoxy-6-ethoxy-1,4-phenylene ether), poly (2-ethyl-6-stearyloxy-1) , 4-phenylene ether), poly (2,6-di-chloro-1,4-phenylene ether), poly (2-methyl-6-phenyl-1,4-phenylene ether), poly (2,6-dibenzyl) -1,4-phenylene ether), poly (2-ethoxy-1,4-phenylene ether), poly (2-chloro-1,4-phenylene ether), poly ( , 5-dibromo-1,4-phenylene ether). It is preferable to use polyphenylene ether whose substituent is an alkyl group having 1 to 4 carbon atoms. Examples thereof include poly (2,6-dimethyl-1,4-phenylene ether), poly (2,6 -Diethyl-1,4-phenylene ether), poly (2-methyl-6-ethyl-1,4-phenylene ether), poly (2-methyl-6-propyl-1,4-phenylene ether), poly (2 , 6-dipropyl-1,4-phenylene ether) and poly (2-ethyl-6-propyl-1,4-phenylene ether).

  Homopolymers can be produced by reaction of each phenol, and copolymers can be produced by reaction of two or more different phenols. PPE copolymers can be made from one of the polyphenylene ethers described above by the addition of a trialkylphenol such as 2,3,6-trimethylphenol. A graft copolymer composed of polyphenylene ether and an aromatic vinyl polymer such as styrene, α-methylstyrene, vinyltoluene and chlorostyrene is also suitable.

  In addition to the polymers P1 and P2, the material may contain at least one polymer P4 in addition to P1 and P2. Examples of polymers P4 that can be used are acrylonitrile-styrene-acrylate (ASA), polyamide (PA), polyolefins such as polypropylene (PP) and polyethylene (PE), polyacrylates such as polymethyl methacrylate (PMMA), polycarbonate (PC ), Polyesters such as polyethylene terephthalate (PET) or polybutylene terephthalate (PBT), polyethersulfone (PES), polyetherketone (PEK), or polyether sulfide (PES), or mixtures thereof. Polyamide (PA) is preferred.

  In a particularly preferred embodiment, the polymer blend comprises one or more uniformly distributed blowing agents in a total proportion of 2 to 12% by weight, preferably 3 to 9% by weight, based on the polymer melt containing the blowing agent. . Suitable blowing agents are the physical blowing agents usually used in EPS, for example aliphatic hydrocarbons having 2 to 7 carbon atoms, alcohols, ketones, ethers, esters or halogenated hydrocarbons. Preference is given to using isobutane, n-butane, isopentane or n-pentane. Suitable co-blowing agents are ethanol, acetone, methylal (dimethoxymethane) and methyl formate.

The present invention further includes
a) mixing components P1, P2 and P3;
b) a step of melting, preferably in an extruder,
c) liquefying step;
d) if necessary, mixing and introducing a foaming agent and optionally additives;
e) cooling step;
f) discharging through the die plate; and
g) optionally pelletizing at a water pressure of 10-15 bar in a water bath, preferably with a 0.65 mm pelletizing die;
Provides a method for producing a polymer blend.

  In order to produce the expandable polymer pellets of the present invention, the blowing agent is introduced by mixing into the polymer melt. The method includes the following steps: a) producing a melt, b) mixing, c) cooling, d) conveying, and e) pelletizing. Each of these steps can be performed using a known device or combination of devices in plastic processing. Suitable equipment for introduction by mixing is a static or dynamic mixer, for example an extruder. The polymer melt can be used directly from the polymerization reactor, can be produced directly in a mixing extruder, or can be produced in a separate melt extruder by melting the polymer pellets. The cooling of the melt may take place in mixing assemblies or separate chillers. Examples of pelletizers that can be used are pressurized water pelletizers, pelletizers equipped with rotating blades and cooling means for spraying mist of temperature control liquid, or pelletizers comprising atomizing means.

An example of a suitable device arrangement for performing the method is:
a) Polymerization reactor-static mixer / cooler-pelletizer b) Polymerization reactor-extruder-pelletizer c) Extruder-static mixer-pelletizer d) Extruder-pelletizer.

  This arrangement may also have an auxiliary extruder for introducing additives such as solid or heat sensitive additives.

  The temperature of the melt when the polymer melt containing the blowing agent is conveyed through the die plate is generally 140 to 300 ° C, preferably 160 to 240 ° C. Cooling to the glass transition temperature range is not necessary.

  The die plate is heated to the temperature of the polystyrene melt containing at least the blowing agent. The temperature of the die plate is preferably 20 to 100 ° C. higher than the temperature of the polymer melt containing the foaming agent. This avoids polymer deposition in the die and ensures a problem-free pelletization.

  In order to obtain a marketable pellet size, the diameter (D) of the die hole in the discharge part from the die is 0.2 to 1.5 mm, preferably 0.3 to 1.2 mm, particularly preferably 0.3 to Should be in the range of 0.8 mm. Even after the die swell, this makes it possible to control the setting of pellets having a size of less than 2 mm, particularly 0.4 to 1.4 mm.

  Die swell is affected not only by molecular weight distribution but also by die shape. The die plate preferably has a hole with an L / D ratio of at least 2 (however, the length (L) indicates the area of the die that is the diameter (D) at the die discharge portion at most). . The L / D ratio is preferably 3-20.

  The diameter (E) of the hole at the entrance to the die in the die plate should generally be at least twice as large as the diameter (D) at the exit from the die.

  The die plate has, for example, a conical injection portion and a hole having an injection angle α (preferably 30 to 120 °) smaller than 180 °. In another embodiment, the die plate has a conical discharge and a hole with a discharge angle β (preferably 15-45 °) less than 90 °. In order to obtain a controlled pellet size distribution in the styrene polymer, the die plate may be provided with holes of different discharge diameters (D). Various die-shaped embodiments may be combined with each other.

  In order to improve processability, the resulting foamable polymer pellets may be coated with glycerol esters, antistatic agents or anticoagulants.

  In order to improve foamability, fine droplets of internal water may be introduced into the polymer matrix. This can be done, for example, by adding water to the molten polymer matrix. Water can be added before, with or after the addition of the blowing agent. A dynamic or static mixer can be used to disperse the water uniformly.

  A sufficient amount of water is generally 0-2% by weight, preferably 0.05-1.5% by weight, based on the total polymer component.

  A foam having a sufficient number of cells and having a uniform foam structure is formed by foaming expandable polymer pellets having internal water in the form of internal water droplets having a diameter of 0.5-15 μm, at least 90%. Is done.

  The amount of foaming agent and water to be added is at most 125, preferably 25 to 100, when the expansion capacity α (defined by the bulk density before foaming / bulk density after foaming) of the foamable polymer pellets is at most. select.

  The bulk density of the expandable polymer pellets of the present invention is usually at most 700 g / l, preferably 590-660 g / l. If a filler is used, the bulk density may be 590-1200 g / l, depending on the nature and amount of the filler.

  Other materials that can be added to the polymer melt include additives, nucleating agents, fillers, plasticizers, flame retardants, and soluble and insoluble inorganic and / or organic dyes and pigments, such as IR absorption Agents such as carbon black, graphite or aluminum powders, which may be added together or spatially separated, for example using a mixer or an auxiliary extruder.

  In a preferred embodiment, 0.01 to 30% by weight, preferably 1 to 5% by weight of dyes and pigments are added. It is advantageous to use dispersants such as organosiloxanes, epoxidized polymers or maleic anhydride-grafted styrene polymers, especially in the case of polar pigments, in order to distribute the pigment uniformly and finely in the styrene polymer. It is. Preferred plasticizers are mineral oils, low molecular weight styrene polymers or phthalates, which can be used in an amount of 0.05 to 10% by weight, based on the styrene polymer.

  The foamable thermoplastic polymer pellets of the present invention are pre-foamed in the first stage, preferably with warm air or fluid, to obtain foam beads having a density of 10 to 250 g / l, and in the second stage in a closed mold. By fusing, the moldable foam molded product of the present invention is obtained.

  The present invention will be further described with reference to examples, but is not limited thereto.

Selected starting materials are:
Component A: Noryl 8890C polyphenylene ether (GE Plastics)
Component B1: 486M high impact polystyrene (HIPS) (BASF SE), Mw / Mn = 3.31, molecular weight 195000,
Component B2: Polystyrene (GPPS), molecular weight 261000, Mw / Mn = 3.46
Component C: Elastic block copolymer based on butadiene / styrene, molecular weight 130000; Mw / Mn = 1.3, constituting butadiene 35% / polystyrene 65%
Pentane S: 20% isopentane, 80% by weight n-pentane

Example 1
In a Leistritz ZSK18 twin screw extruder, 12.5% by weight of component C and 80.1% by weight of component B1 were melted at 220-240 ° C. 5.6% by weight of pentane S based on the polymer matrix was then placed in the polymer melt. The polymer melt was then homogenized in two static mixers and cooled to 180 ° C. By means of an auxiliary extruder, 1.7% by weight of talc (HP320, Omycarb), based on the polymer matrix, was added as a nucleating agent in the form of a masterbatch to the main melt stream containing the blowing agent. After homogenization with two further static mixers, the melt was extruded through a heated pelletizing die (4 holes with an internal diameter of 0.65 mm with a pelletizing die at 280 ° C.). The polymer strand was cut with an underwater pelletizer (water pressure 12 bar, water temperature 45 ° C.) to obtain mini-pellets containing a blowing agent and having a narrow particle size distribution (d ′ = 1.2 mm).

Example 2
In a Leistritz ZSK18 twin screw extruder, 12.5% by weight of component C was melted with 80.1% by weight of component B2 at 220-240 ° C. 5.6% by weight of pentane S based on the polymer matrix was then placed in the polymer melt. The polymer melt was then homogenized in two static mixers and cooled to 180 ° C. By means of an auxiliary extruder, 1.7% by weight of talc (HP320, Omycarb), based on the polymer matrix, was added as a nucleating agent in the form of a masterbatch to the main melt stream containing the blowing agent. After homogenization with two further static mixers, the melt was extruded through a heated pelletizing die (4 holes with an internal diameter of 0.65 mm with a pelletizing die at 280 ° C.). The polymer strand was cut with an underwater pelletizer (water pressure 12 bar, water temperature 45 ° C.) to obtain mini-pellets containing a blowing agent and having a narrow particle size distribution (d ′ = 1.2 mm).

Example 3
In a ZSK18 twin screw extruder manufactured by Leistritz, 20.6% by mass of component C and 72.0% by mass of component B2 were melted at 220-240 ° C. 5.6% by weight of pentane S based on the polymer matrix was then placed in the polymer melt. The polymer melt was then homogenized in two static mixers and cooled to 180 ° C. By means of an auxiliary extruder, 1.7% by weight of talc (HP320, Omycarb), based on the polymer matrix, was added as a nucleating agent in the form of a masterbatch to the main melt stream containing the blowing agent. After homogenization with two further static mixers, the melt was extruded through a heated pelletizing die (4 holes with an internal diameter of 0.65 mm with a pelletizing die at 280 ° C.). The polymer strand was cut with an underwater pelletizer (water pressure 12 bar, water temperature 45 ° C.) to obtain mini-pellets containing a blowing agent and having a narrow particle size distribution (d ′ = 1.2 mm).

Example 4
In a Leskrit ZSK18 twin screw extruder at 220-240 ° C., 20.6% by weight of component C, 3.9% by weight of component A and 68.1% by weight of B2 72.0% by weight of polystyrene. Melted with masterbatch. 5.6% by weight of pentane S based on the polymer matrix was then placed in the polymer melt. The polymer melt was then homogenized in two static mixers and cooled to 180 ° C. By means of an auxiliary extruder, 1.7% by weight of talc (HP320, Omycarb), based on the polymer matrix, was added as a nucleating agent in the form of a masterbatch to the main melt stream containing the blowing agent. After homogenization with two further static mixers, the melt was extruded through a heated pelletizing die (4 holes with an internal diameter of 0.65 mm with a pelletizing die at 280 ° C.). The polymer strand was cut with an underwater pelletizer (water pressure 12 bar, water temperature 45 ° C.) to obtain mini-pellets containing a blowing agent and having a narrow particle size distribution (d ′ = 1.2 mm).

The mini-pellets obtained from Examples 1-4 were used as starting materials for the following foam production:
The pellets were pre-foamed at a gauge pressure of 0.1 bar to a density of 35-20 g / L, and after 12 to 24 hours of intermediate storage, foaming was completed in an automatic molding machine at a gauge pressure of 1.0 bar. Obtained.

  The properties of the resulting foam are as follows:

  Comparing foam 4 of the present invention with foams 1-3, a low foam density with a high proportion of elastic component C can be obtained according to the present invention.

Claims (9)

Polystyrene P1,
An elastic block copolymer P2 composed of at least one aromatic vinyl monomer and at least one diene monomer;
Polyphenylene ether P3,
Including
For all of P1, P2 and P3,
93 to 41% by mass of P1,
5-45 wt% P2, and 2-14 wt% P3,
A foamable thermoplastic polymer blend characterized by comprising:   The foamable thermoplastic polymer blend of claim 1 comprising a foaming agent.   The polymer blend according to claim 1 or 2, comprising at least 10% by mass of P2, based on the total of P1, P2 and P3.   4. The polymer blend according to any one of claims 1 to 3, further comprising at least one further polymer P4.   P2 includes a block A that forms a hard phase and incorporates polymerized units of an aromatic vinyl monomer, and an elastic block B / A that forms a soft phase and incorporates polymerized units of an aromatic vinyl monomer and a diene The polymer blend according to any one of claims 1 to 4.   The glass transition temperature Tg of the block A exceeds 25 ° C., the glass transition temperature Tg of the block B / A is less than 25 ° C., the volume ratio of the block A phase to the block B / A is 6. The polymer blend according to claim 5, wherein the polymer blend is selected so as to be 1 to 40% by volume with respect to the whole polymer and that the mass ratio of diene is less than 50% by mass.   A pelletized polymeric material comprising the polymer blend of any one of claims 1-6. a) mixing the components P1, P2 and P3 of claim 1;
b) melting in an extruder;
c) liquefying step;
d) mixing and introducing the blowing agent;
e) cooling step;
f) discharging through the die plate;
g) pelletizing step;
A process for producing a polymer blend according to claim 6 comprising :
Using P1, P2 and P3 as a whole, 93 to 41% by mass of P1, 5 to 45% by mass of P2, and 2 to 14% by mass of P3,
P2 includes a block A that forms a hard phase and incorporates polymerized units of an aromatic vinyl monomer, and an elastic block B / A that forms a soft phase and incorporates polymerized units of an aromatic vinyl monomer and a diene ,
The glass transition temperature Tg of the block A exceeds 25 ° C., the glass transition temperature Tg of the block B / A is less than 25 ° C., the volume ratio of the block A phase to the block B / A is The method selected so that it may be 1-40 volume% with respect to the whole polymer, and the mass ratio of diene may be less than 50 mass% .   A moldable foam molded article obtained by fusing the polymer pellets of claim 7.