DE102013224277A1 - Process for preparing antistatic, expandable, thermoplastic polymer particles - Google Patents

Abstract

A method of making antistatic, expandable, thermoplastic polymer particles by mixing and forming a polymer melt from components A) 45 to 97.8 wt%, preferably 55 to 78.1 wt% of a styrenic polymer, B1) 1 to 45 wt .-%, preferably 7 to 15 weight percent of a polyolefin with a determined by DSC at a heating rate of 10 ° C / minute melting point in the range of 105 to 140 ° C, B2) 0 to 25 wt .-%, preferably 5 to 10 weight percent a polyolefin with a melting point below 105 ° C., determined by means of DSC at a heating rate of 10 ° C./minute, C1) from 0.1 to 25% by weight, from 6 to 15% by weight of a styrene-butadiene or styrene-isoprene block copolymer, C2) 0.0 to 10 wt .-%, preferably 0.8 to 3 weight percent of a styrene-ethylene-butylene block copolymer, D) 1 to 15 wt .-%, preferably 3 to 10 weight percent of a blowing agent, E) 0 to 5 wt .-%, preferably 0.3 to 2 weight percent of a nucleating agent , and F) 0.1 to 5 wt .-%, preferably 1 to 3 wt .-% of an antistatic agent, wherein the sum of A) to F) gives 100 wt .-%, and extruding the polymer melt through a nozzle plate with subsequent Underwater granulation, the antistatic, expandable, thermoplastic polymer particles obtainable by the process and their processing into antistatic particle foam moldings.

Description

The present invention relates to a process for preparing antistatic, expandable, thermoplastic polymer particles and their processing into antistatic particle foam molded parts.

Antistatic packings made from particle foams (EPS, EPP, EPE and their copolymers and blends) are used to package high-quality electronic components. The antistatic equipment serves to avoid visually adverse dust deposits on the packaging and to protect the delicate electronics of the components, which could be damaged by undetached electrostatic charge. To meet the market requirements, a surface resistance at normal temperatures and humidities of less than 10 ¹² Ω, preferably less than 10 ¹⁰ Ω required.

Antistatic agents can be incorporated in the foam packages in various ways, for example by incorporation into the polymer matrix during manufacture by spraying onto the finished package (disadvantageous because handling of chemicals at the molding manufacturer, corrosion, easily washable and contaminating the parts to be packaged) or by application on the still unfoamed or already foamed granulate beads.

Customers in Asia require antistatic moldings for packaging electronic components. The previously customary method of coating raw material beads with antistatic agents after production does not achieve the required conductivities due to the low surface area of the still unfoamed beads.

The EP 0 774 484 A2 describes a process for equipping particle foam in which a) a dispersion consisting essentially of polyolefin particles and a liquid dispersion medium and a mixture of a volatile organic blowing agent and the additive to be introduced are placed in a pressure-resistant reactor, b) a heat treatment is carried out is, wherein the polyolefin particles are impregnated with the mixture, and then c) the dispersion is discharged through an opening in a low-pressure space, wherein the polymer particles are foamed. Here, the foaming particles are coated in a suspension vessel before foaming with antistatic agents.

The WO 2006/106121 A1 describes a process for preparing antistatic, expandable styrene polymers in which 0.05 to 6% by weight of an antistatic agent and a blowing agent are added to a styrene polymer melt and extruded through a die and granulated.

The JP-A 2011-213900 relates to the preparation of antistatic foam particles, the antistatic agent incorporated both in the expandable particles and added to the prefoamer.

The EP 0 114 503 B1 describes a process for producing antistatic cups in which the antistatic agent is added before or during the prefoaming of thermoplastic beads or in liquid form during the molding of the article.

It is an object of the present invention to provide a process for the antistatic finish of expandable thermoplastic particles that retains satisfactory antistatic properties even on attrition and after prefoaming and can be made into antistatic, low surface resistivity elastic particle foam moldings.

• A) 45 bis 97,8 Gew.-%, bevorzugt 55 bis 77,9 Gewichtsprozent eines Styrolpolymeren,
• B1) 1 bis 45 Gew.-%, bevorzugt 7 bis 15 Gewichtsprozent eines Polyolefins mit einem mittels DSC bei einer Aufheizrate von 10°C/Minute ermitteltem Schmelzpunkt im Bereich von 105 bis 140°C,
• B2) 0 bis 25 Gew.-%, bevorzugt 5 bis 10 Gewichtsprozent eines Polyolefins mit einem mittels DSC bei einer Aufheizrate von 10°C/Minute ermitteltem Schmelzpunkt unter 105°C,
• C1) 0,1 bis 25 Gew.-%, 6 bis 15 Gewichtsprozent eines Styrol-Butadien- oder Styrol-Isopren-Blockcopolymeren,
• C2) 0,0 bis 10 Gew.-%, bevorzugt 0,8 bis 3 Gewichtsprozent eines Styrol-Ethylen-Butylen-Blockcopolymeren,
• D) 1 bis 15 Gew.-%, bevorzugt 3 bis 10 Gewichtsprozent eines Treibmittels,
• E) 0 bis 5 Gew.-%, bevorzugt 0,3 bis 2 Gewichtsprozent eines Nukleierungsmittels, und
• F) 0,1 bis 5 Gew.-%, bevorzugt 1 bis 3 Gew.-% eines Antistatikum, wobei die Summe aus A) bis F) 100 Gew.-% ergibt, und

Extrudieren der Polymerschmelze durch eine Düsenplatte mit anschließender Unterwassergranulierung.The object has been achieved by a process for producing antistatic, expandable, thermoplastic polymer particles by mixing and forming a polymer melt from the components

• A) from 45 to 97.8% by weight, preferably from 55 to 77.9% by weight of a styrene polymer,
• B1) from 1 to 45% by weight, preferably from 7 to 15% by weight, of a polyolefin with a melting point in the range of from 105 to 140 ° C., determined by means of DSC at a heating rate of 10 ° C./minute,
• B2) from 0 to 25% by weight, preferably from 5 to 10% by weight, of a polyolefin with a melting point below 105 ° C. determined by means of DSC at a heating rate of 10 ° C./minute,
• C1) from 0.1 to 25% by weight, from 6 to 15% by weight of a styrene-butadiene or styrene-isoprene block copolymer,
• C2) from 0.0 to 10% by weight, preferably from 0.8 to 3% by weight, of a styrene-ethylene-butylene block copolymer,
• D) 1 to 15% by weight, preferably 3 to 10% by weight of a blowing agent,
• E) 0 to 5 wt .-%, preferably 0.3 to 2 weight percent of a nucleating agent, and
• F) 0.1 to 5 wt .-%, preferably 1 to 3 wt .-% of an antistatic agent, wherein the sum of A) to F) 100 wt .-% results, and

Extrusion of the polymer melt through a die plate followed by underwater granulation.

Particularly preferably, the expandable, thermoplastic polymer particles obtainable by the process according to the invention consist of the above-described components A) to F). In the foam particles, the blowing agent (component D) has essentially escaped after pre-foaming.

As styrene polymers A) standard (GPPS) or impact polystyrene (HIPS) or styrene-acrylonitrile copolymers (SAN) or acrylonitrile-butadiene-styrene copolymers (ABS) or mixtures thereof can be used. Particularly preferred are standard polystyrene types having weight average molecular weights in the range of 120,000 to 300,000 g / mol, in particular 190,000 to 280,000 g / mol, determined by gel permeation chromatography; and a melt volume rate MVR used (200 ° C / 5 kg) according to ISO 113 in the range of 1 to 10 cm ^3/10 min, for example PS 158 K, 168 N or 148 G of BASF SE. To improve the fusion of the foam particles in the processing for molding can easily flowing grades, for example Empera ^® 156L (Innovene) are added

As further components B) polyolefins B1) having a melting point in the range from 105 to 140 ° C. and polyolefins B2) having a melting point below 105 ° C. are used for the expandable thermoplastic polymer particles. The melting point is the melting peak determined by DSC (Dynamic Scanning Calorimetry) at a heating rate of 10 ° C./minute.

For the process according to the invention 1 to 45 weight percent, in particular 7 to 15 wt .-% of a polyolefin B1) are used. As the polyolefin B1) is preferably a homo- or copolymer of ethylene and / or propylene having a density in the range of 0.91 to 0.98 g / L (determined according to ASTM D792 ), in particular polyethylene used. In particular injection molding grades come into consideration as polypropylenes. As polyethylenes commercially available homopolymers of ethylene, such as LDPE (injection molded types), LLD, -HD, or copolymers of ethylene and propylene (eg. B Moplen ^® RP220 and RP320 Moplen ^® Basell or Versify ^® grades of Dow) , Ethylene and vinyl acetate (EVA), ethylene acrylate (EA) or ethylene-butylene acrylate (EBA) in question. The melt volume index MVI (190 ° C / 2.16 kg) of the polyethylenes is usually in the range of 0.5 to 40 g / 10 min, the density in the range of 0.91 to 0.95 g / cm ³ . In addition, mixtures may polyisobutene (PIB) (z. B. ^® Oppanol B150, BASF company files) can be used. Particularly preferred is LLDPE having a melting point in the range of 110 to 125 ° C and a density in the range of 0.92 to 0.94 g / L used.

Also suitable as component B1) are olefin block copolymers which are composed of a polyolefin block PB1 (hard block) and a polyolefin block PB2 (soft block), as described, for example, in US Pat WO 2006/099631 are described. The polyolefin block PB1 preferably consists of 95 to 100% by weight of ethylene. The PB2 block is preferably composed of ethylene and α-olefin, where as α-olefins styrene, propylene, 1-butene, 1-hexene, 1-octene, 4-methyl-1-pentene, norbornene, 1-decene, 1, 5-hexadiene or mixtures thereof. Preferred as the PB2 block is an ethylene-α-olefin copolymer block having 5 to 60 wt% α-olefin, especially an ethylene-octene copolymer block. Preference is given to multiblock copolymers of the formula (PB1-PB2) n, where n is an integer between 1 and 100. The blocks PB1 and PB2 essentially form a linear chain and are preferably distributed alternately or statistically. The proportion of the PB2 blocks is preferably 40 to 60 wt .-%, based on the olefin block copolymer. Particularly preferred are olefin block copolymers with alternating, hard PB1 blocks and soft, elastomeric PB2 blocks that are commercially available under the name INFUSE ^®.

With a lower proportion of polyolefin B1), the blowing agent retention capacity increases significantly. Thus, the shelf life and the processability of the expandable thermoplastic polymer particles are significantly improved. In the range of 4 to 20 wt .-% polyolefin is obtained expandable thermoplastic polymer particles having a long shelf life, without worsening the elastic properties of the particle foam produced therefrom. This manifests itself, for example, in a lower demolding _remainder ε _rest in the range of 25 to 35%.

As polyolefin B2) for the preparation of the expandable thermoplastic polymer particles 0 to 25 weight percent, in particular 1 to 10 wt .-% of a polyolefin B2) having a melting point below 105 ° Ceingesetzt. The polyolefin B2) preferably has a density in the range of 0.86 to 0.90 g / L (determined by ASTM D792 ) on. For this purpose, in particular thermoplastic elastomers based on olefins (TPO) are suitable. Particularly preferred are ethylene-octene copolymers, which are commercially available, for example, under the name ^Engage® 8411 from Dow. Expandable, thermoplastic polymer particles containing the component B2) show a significant improvement in the bending work and tear resistance after processing into foam moldings.

For specific adjustment of the desired morphology, compatibilizers (components C) are used according to the invention. A further improvement in compatibility is achieved by using a mixture of styrene-butadiene or styrene-isoprene block copolymers as component C1) and styrene-ethylene-butylene block copolymers (SEBS) as component C2).

As component C1) 0.1 to 25 weight percent, in particular 6 to 15 wt .-% of a styrene-butadiene or styrene-isoprene block copolymers are used.

For example, styrene-butadiene or styrene-isoprene block copolymers are suitable for this purpose. The total diene content is preferably in the range from 20 to 60% by weight, particularly preferably in the range from 30 to 50% by weight, the total styrene content is correspondingly preferably in the range from 40 to 80% by weight, particularly preferably in the region of 50 to 70% by weight.

Preferred compatibilizers 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 partially hydrogenated or unhydrogenated. These are, for example, under the name Styroflex® ^® 2G66, Styrolux ^® 3G55, Styroclear ^® GH62, Kraton ^® D 1101, Kraton ^® D 1155, Tuftec ^® H1043 or Europren ^® SOL T6414 commercially. These are SBS block copolymers with sharp transitions between B and S blocks.

As component C2) 0 to 10 weight percent, in particular 0.8 to 3 wt .-% of a styrene-ethylene-butylene block copolymer (SEBS) are used. Suitable styrene-ethylene-butylene block copolymers (SEBS) are, for example, those obtainable by hydrogenation of the olefinic double bonds of the block copolymers C1). Suitable styrene-ethylene-butylene block copolymers are, for example, the commercially available ^Kraton® G types, in particular ^Kraton® G 1650.

Furthermore, further additives, such as nucleating agents, plasticizers, halogen-containing or halogen-free flame retardants, soluble and insoluble inorganic and / or organic dyes and pigments, fillers or Cotreibmittel can be added in amounts that do not affect the domain formation and resulting foam structure of the multiphase polymer mixture.

As propellant (component D) in the inventive method 1 to 15 weight percent, preferably 3 to 10 weight percent, based on the sum of all components A) to E), a physical blowing agent. The propellants may be gaseous or liquid at room temperature (20 to 30 ° C) and atmospheric pressure. They should have a boiling point below the softening temperature of the polymer blend, usually in the range of -40 to 80 ° C, preferably in the range of -10 to 40 ° C. Suitable blowing agents are, for example, halogenated or halogen-free aliphatic hydrocarbons, alcohols, ketones or ethers. Suitable aliphatic propellants are, for example, aliphatic C ₃ to C ₈ hydrocarbons, such as n-propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, neopentane, cycloaliphatic hydrocarbons, such as cyclobutane and cyclopentane, halogenated hydrocarbons such as methyl chloride, ethyl chloride, methylene chloride, trichlorofluoromethane, dichlorofluoromethane, dichlorodifluoromethane, chlorodifluoromethane, dichlorotetrafluoroethane, and mixtures thereof. The halogen-free blowing agents are preferably isobutane, n-butane, isopentane, n-pentane, neopentane, cyclopentane and mixtures thereof.

Suitable co-propellants are those having a lower selectivity of solubility for the domain-forming phase, for example, gases such as CO ₂ , N ₂ , fluorocarbons or noble gases. These are preferably used in amounts of 0 to 10 wt .-%, based on the expandable thermoplastic polymer particles.

As component E) 0 to 5 weight percent, preferably 0.3 to 2 weight percent of a nucleating agent or nucleating agent, for example talcum used.

Antistatic agents F) are suitable for the antistatic treatment of expandable, thermoplastic particles known antistatic agents. The antistatic agents may be used singly or in mixture. Preference is given to using quaternary ammonium salts as antistatic agents.

The particle foam may, in addition to the antistatic agents, also be provided with other specific additives, for example, effective over the gas phase, corrosion inhibitors

To improve processability, the finished, expandable thermoplastic polymer particles may be coated by glycerol ester or anticaking agent.

Preferably, the resulting round or oval particles are foamed to a diameter in the range of 0.2 to 10 mm. Their bulk density is preferably in the range of 10 to 100 kg / m ³ .

The prefoamed, thermoplastic foam particles obtainable by the process according to the invention can be used for the production of antistatic particle foam moldings.

The expandable, thermoplastic polymer particles can be prefoamed by means of hot air or steam to foam particles having a density in the range of 10 to 100 kg / m ³ , preferably in the range of 15 to 80 kg / m ³ and then welded in a closed mold into foam moldings.

The expandable, thermoplastic particles may also contain other additives, nucleating agents, plasticizers, halogen-containing or halogen-free flame retardants, soluble and insoluble inorganic and / or organic dyes and pigments or fillers in conventional amounts.

The expandable or prefoamed thermoplastic particles can additionally be coated with one or more volatile corrosion inhibitors during or after the prefoaming, foamed into foam particles and sintered in a proportioning machine.

The inventive method is characterized in that the antistatic agents need not be applied in a separate process step to the expandable or pre-coated particles and can not be washed off during pre-foaming. They do not disturb the Vorschäumprozess and also not corrosive.

The particle foam moldings produced by the process according to the invention exhibit a balanced ratio of elasticity and stiffness, which lie between those of expandable polystyrene (EPS) foams and polypropylene particle foams (EPP). The foam parts meet the required resistance values of less than 10E10 ohms. They can be used for the packaging of higher quality electronic components such as televisions, computers or electronic components such as microchips.

Examples

Starting Materials:

• Component A: polystyrene having a melt viscosity index MVI (200 ° C / 5kg) of 2.9 cm ^3/10 min (PS 158K from BASF SE, Mw = 280,000 g / mol, viscosity number VN 98 ml / g)

Component B: B1: Polyethylene LLDPE (LL1201 XV, Exxon Mobile, density 0.925 g / L, MVI = 0.7 g / 10 min, melting point 123 ° C) B2: Polyethylene, ethylene-octene copolymer (Engage ^® 8411 from Dow, density 0.880 g / L, MVI = 18 g / 10 min, melting point 72 ° C) Component C: C1: Styrolux 3G55 ^®, BASF SE styrene-butadiene block copolymer, C2: Kraton G 1650, styrene-ethylene-butylene block copolymer from Kraton Polymers LLC Component D: D Propellant mixture of iso-pentane and n-pentane, unless otherwise noted pentane S (20 wt .-% iso-pentane, 80 wt .-% of n-pentane) was used.

• Component E: Talc (HP 320, Omyacarb)

Component F) Larostat ^® 905 Antistatic agent (BASF SE) Neostatic ^® HB 15 5 Antistatic agent (Peter H. Urdahl GmbH)

Preparation of a PS / PE Polymer Blend

In a twin-screw extruder Leitritz ZE 40 were
76.9 parts by weight of the components A,
7.5 parts by weight of components B1,
4.7 parts by weight of components B2,
1.6 parts by weight of the components C1,
0.9 parts by weight of the components C2 melted at 240-260 ° C / 140 bar and with
1.9 parts by weight of talc as nucleating agent (component E).

Examples 1-4:

Subsequently, according to the amounts shown in Table 1, the antistatic agent (component F) was added to the polymer melt and pentane S (20% iso-pentane, 80% n-pentane) as blowing agent (component D) pressed and homogeneously mixed in the two static mixers Incorporated polymer melt. Thereafter, the temperature was reduced to 180 ° -195 ° C via a condenser. After further homogenization via two further static mixers, the polymer melt was pressed at 50 kg / h through a tempered to 240-260 ° C perforated plate at 200-220 bar (0.6 mm hole diameter with 7 nests x 7 holes or 0.4 mm Hole diameter with 7 nests x 10 holes). The polymer strand was beaten off by means of underwater granulation (11-10 bar underwater pressure at 40 ° C.-50 ° C. water temperature), so that a propellant-laden minigranulate having a narrow particle size distribution (d = 1.1 mm at 0.6 mm hole diameter and 0.8 mm at 0.4 mm hole diameter).

To clean the perforated plates, a high-pressure cleaner was used. In order not to damage the platelets or the solder between the platelets, the procedure was as described below. The perforated plate covered with the product was first connected to a Marlotherm heating circuit and melted out. Thereafter, the remaining product residues in the microchannels are cleaned with the high-pressure cleaner. The cleaning of the main channel (rear, nozzle diameter 0.8 mm) was carried out at an operating pressure of 800 to max. 1000 bar and a water volume of 40-50 l / min. The cleaning of the cutting surface / microchannels from the front (nozzle: 0.25 mm diameter) was carried out at an operating pressure of max 1700bar and a water volume of 4l / min. The advantage of the high-pressure cleaning compared to the previous cleaning in the solvent bath is a better degree of cleaning of the microchannels and less residual product. As a result, the fine fraction in the finished product is lower and the service life of the perforated plate is increased.

The propellant-containing granules were prefoamed in an EPS prefoamer to foam beads with a density of about 26 g / L and processed in an EPS molding machine at an overpressure of 0.7-1.1 bar to form parts.

Comparative Experiments V1-V3

Example 1 was repeated with the difference that the antistatic agent was not added to the polymer melt, but was applied to the propellant-containing PS / PE granules as a coating.

Production of the moldings:

The foam beads were processed after 24 hours storage in a molding machine (Erlenbach) to disk-shaped moldings (diameter: 300 mm, height 50 mm). The density of the packaging molded parts was about 26 kg / m ³ .

The plates were stored for 24 hours at 60 ° C in a drying oven and then for 24 hours in a climatic chamber at 25 ° C and 60% rel. Humidity. Subsequently, the surface resistance [Ω] at 25 ° C and 60% rel. Humidity measured at 10 V and the average of 5 measurements distributed across the disk. Table 1 Ex. Polymer blend [% by weight] Pentane [% by weight] Antistatic [% by weight] method Conductivity molded part [ohm] Dense molded part [g / l] V1 95 5 0 10E11 25 V2 94 5 1.0 (Neostatic) Coating before pre-foamer 10E11 26 V3 94 5 1.0 (Larostat) Coating before pre-foamer 10E11 26 1 94.5 5 0.5 (Neostatic) einkompoundiert 10E10 25 2 94.2 5 0.8 (Neostatic) einkompoundiert 10E10 26 3 93.5 5 1.5 (Neostatic) einkompoundiert 10E7 26 4 93.5 5 1.5 (Larostat) einkompoundiert 10E8 26

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0774484 A2 [0005]
• WO 2006/106121 A1 [0006]
• JP 2011-213900 A [0007]
• EP 0114503 B1 [0008]
• WO 2006/099631 [0015]

Cited non-patent literature

• ASTM D792 [0014]
• ASTM D792 [0017]

Claims (4)

A process for making antistatic, expandable, thermoplastic polymer particles by mixing and forming a polymer melt from the components A) from 45 to 97.8% by weight, preferably from 55 to 77.9% by weight of a styrene polymer, B1) from 1 to 45% by weight, preferably from 7 to 15% by weight, of a polyolefin with a melting point in the range of from 105 to 140 ° C., determined by means of DSC at a heating rate of 10 ° C./minute, B2) from 0 to 25% by weight, preferably from 5 to 10% by weight, of a polyolefin with a melting point below 105 ° C. determined by means of DSC at a heating rate of 10 ° C./minute, C1) from 0.1 to 25% by weight, from 6 to 15% by weight of a styrene-butadiene or styrene-isoprene block copolymer, C2) from 0.0 to 10% by weight, preferably from 0.8 to 3% by weight, of a styrene-ethylene-butylene block copolymer, D) 1 to 15% by weight, preferably 3 to 10% by weight of a blowing agent, E) 0 to 5 wt .-%, preferably 0.3 to 2 weight percent of a nucleating agent, and F) 0.1 to 5 wt .-%, preferably 1 to 3 wt .-% of an antistatic agent, wherein the sum of A) to F) 100 wt .-% results, and Extrusion of the polymer melt through a die plate followed by underwater granulation. A method according to claim 1, characterized in that one uses a quaternary ammonium salt as an antistatic agent. Antistatic, expandable thermoplastic polymer particles obtainable by the process according to claim 1 or 2. A process for the preparation of antistatic particle foam moldings, characterized in that antistatic, expandable thermoplastic polymer particles according to claim 3 prefoamed with hot air or water vapor to foam particles, and welded in a molding machine.