Halogen-free polymer blend

Abstract

The invention concerns a halogen-free polymeric blend capable of ionic conductivity comprising either one or more polyether-based polymers or copolymers that have favorable structures to facilitate polymer chain segmental motion and ion hopping environment, selected from the group of polyether-block-polymers and polyether-based polyurethanes, or said polyether based polymers or copolymers together with one or more ionomers formed by neutralization of ethylene acid co-polymers, as well as one or more specific halogen-free ionic complexes or salts comprising a weakly coordinating anion and a cation of an alkali metal or alkaline earth metal. Further, the invention concerns the use of said blend and a plastic material containing said blend as an additive.

Claims

1. An extrudable halogen-free polymeric blend capable of humidity independent ionic charge conduction which consists of a polyether-polyamide block copolymer and an ionic complex or salt selected from sodium bis(oxalato)borate and potassium bis(oxalato)borate and wherein the ionic complex is present in the polymeric blend in an amount of 0.002-0.05 millimols/gram of the polymeric blend.

2. The polymeric blend according to claim 1 wherein the ionic complex or salt is potassium bis(oxalate)borate.

3. An extrudable halogen-free polymeric blend capable of humidity independent ionic charge conduction which consists of a polyether-polyamide block copolymer, 10-30% by mass of one or more ionomers formed by neutralization of polymers of a co- or terpolymer of ethylene and acrylic or methacrylic acid, and an ionic complex or salt selected from sodium bis(oxalato)borate and potassium bis(oxalato)borate, wherein the ionic complex or salt is present in the polymeric blend in an amount of 0.002-0.05 millimols/gram of the polymeric blend.

Description

DETAILED DESCRIPTION

(1) The present invention concerns a halogen-free polymeric blend capable of ionic conduction (i.e. an ionically conductive blend) comprising either one or more polyether based polymers or copolymers that have favorable structures to facilitate polymer chain segmental motion and ion hopping environment, selected from the group of polyether-block-polymers or polyether-based polyurethanes, or said polyether based polymers or copolymers together with one or more ionomers formed by neutralization of ethylene acid co-polymers.

(2) Examples of the polyether-block-polymers include polyether block amides, particularly made up of essentially equal portions of the polyether block and the polyamide, and polymers including a polyether block and a polyolefin block, and polymers including a polyether block and a polyester block, and polymers including a polyether block and an acrylate block.

(3) The polyether block is preferably selected from polyethylene oxides, most suitably being polyethylene glycol.

(4) The blend of the invention preferably contains this/these polyether based polymer(s) in an amount of 10-99% by mass, more preferably 10-80% by mass of the blend, even more preferably 25-70% by mass.

(5) The blend includes one or more specific halogen-free ionic complexes comprising a weakly coordinating anion and an alkali metal or alkaline earth metal cation, which forms a complex that is capable of dissociation in the above mentioned polymer structure.

(6) Said weakly coordinating anions are selected from the group of boron-centered complexes where the bidentate ligand is selected from the group of C2-C8 aliphatic or aromatic organic compounds containing at least two reactive groups selected from COOH and OH, or optionally from their salts.

(7) Exemplary anions include (malonato,oxalato)borate, bis(malonato)borate, bis(oxalato)borate, (glycolato,oxalato)borate, bis(glycolato)borate, (lactato,oxalato)borate, bis(lactato)borate, (oxalato,salicylato)borate, bis(salicylato)borate, (oxalato,tartrato)borate, bis(tartrato)borate, (oxalato,catecholato)borate, bis(catecholato)borate. Preferred options are the bis-anions. Even more preferably, the mentioned weakly coordinating anion is the bis-salt of oxalic and boric acid, i.e. the bis(oxalato)borate anion. Most suitably, the cation is selected from the group of alkali metals excluding lithium, preferably including sodium, potassium, rubidium and cesium, most preferably Na and K, as among others lithium salts generally are more toxic than, for instance, Na and K salts.

(8) In addition to the advantages mentioned above, these ionic complexes or salts have the further advantage of being inert towards the polymer types in question.

(9) The ionic complex or salt is preferably present in an amount of 0.002-0.05 millimols/gram of the polymer blend, particularly the final blend, more preferably less than 0.03 millimols/gram of the blend, including the host polymer. With the stated amounts added, a high ionic conductivity and excellent mechanical properties are obtained simultaneously.

(10) The term halogen-free is intended to mean a content of 0% added halogen. The essential components of the blend may contain traces of halogens, however, this halogen content remains below a detectable level (using conventional analytical procedures), most suitably below a content of 50 ppm.

(11) According to a preferred embodiment of the invention, the blend comprises, in addition to the above components, as a filler polymer, a polymeric material selected from the group of polyamides, polyesters, polyacrylates, polymethyl methacrylates, polyester-based polyurethanes, as well as copolymers thereof.

(12) Thus, according to this embodiment of the invention, the present blend contains at least two different polymers with functional groups capable of coordination (e.g. ether, ester, amide, and other carbonyl groups), of which the first contains at least ether groups, and of which the second contains at least carbonyl groups. The blend also contains a salt or ion complex that may coordinate with said functional groups, providing a more stable blend. The ratio of the first polymer to the second polymer is preferably 10:90-90:10, more preferably 30:70-90:10, most preferably 50:50-70:30.

(13) As mentioned above, the blend possibly comprises, in addition to the first polymer and the optional second polymer, at least one ionomer, which preferably is a polymer of a co- or terpolymer of ethylene and acrylic or methacrylic acid, or any other known ionomer. The content of ionomer is preferably 1-50% by mass of the blend, more preferably 10-50% by mass, most preferably 10-30% by mass.

(14) The final compound i.e. a mixture of said ion conductive polymer blend that forms a co-continuous network also known as interpenetrated network (IPN) within the basic host polymer, may be converted into a film, a sheet, a molded product or an injection molded product with different extrusion conversion equipment. This mixture can be formed prior to the conversion in a separate extrusion process or during the conversion process.

(15) The melt index of the polymer blend according to the invention, measured at a temperature of 190 C. and with a weight of 2160 g, is typically 3-50 g/10 min. The melt index varies depending on the nature and properties of polymers used in the blend. The volume resistivity (ASTM D-257 or IEC60093) of the polymer blend is as low as 10.sup.5 ohm.Math.m. The water absorption of the polymer blend is typically less than 10% by mass/24 hours in immersion.

(16) The process according to the invention for preparing a static dissipative polymer blend comprises the mixing of components at an elevated temperature which is above the melting points of the polymeric components with suitable equipment such as twin screw extruder. The melt temperature is typically between 150 and 300 C. The salt is generally introduced into the blend either as is or as a mixture with other materials.

(17) In the following, the invention will be further illustrated using examples, which are not meant to limit the scope of the invention.

(18) As will be evidenced by the measurements below, the materials of the invention, characterized as being halogen free, show improved properties with respect to thermal stability and ionic conductivity, as well as generally polymeric compatibility, in comparison to other materials known in the art. Also the ionic conductivity is shown to be practically humidity independent giving a steady performance, a property which is of paramount importance for static dissipative materials to be used in varying ambient conditions.

Example 1

(19) 98 parts of a polyether block amide (made up of approx. 50 parts of polyethylene glycol and 50 parts of polyamide-12) and 2 parts of potassium bis-oxalatoborate were mixed together in a Werner-Pfleiderer twin-screw extruder at a temperature of 180 C. and subsequently granulated with underwater pelletizer to give polymer designated as Example 1 (abbreviated as Ex 1). The volume resistivity of the granulates, that were first dried for 3 h at 80 C. and then conditioned for 48 hours at 10 RH % and 20 C., was 110.sup.5. Thermal and electrical properties for Ex 1 granulates have been collected in Table 1 and 2.

Example 2

(20) 55 parts of a polyether block amide (made up of approx. 50 parts of polyethylene glycol and 50 parts of polyamide-12), 36 parts of a glycol-modified polyethylene terephthalate, 5 parts of a styrene methyl methacrylate copolymer and 4 parts of potassium bis-oxalatoborate were mixed together in a Werner-Pfleiderer twin-screw extruder at a temperature of 220 C. and subsequently granulated with underwater pelletizer to give polymer designated as Example 2 (Ex 2). The volume resistivity of the granulates, that were first dried for 3 h at 80 C. and then conditioned for 48 hours at 10 RH % and 20 C., was 210.sup.5. Thermal and electrical properties for Ex 2 granulates have been collected in Tables 1-3.

Comparative Example 1

(21) The same procedure as described in Example 1 was used except that potassium bis-oxalatoborate was replaced by sodium perchlorate monohydrate to give polymer designated as Comparative Example 1 (abbreviated as CE 1). The volume resistivity of the granulates, that were first dried for 3 h at 80 C. and then conditioned for 48 hours at 10 RH % and 20 C., was 110.sup.5. Thermal and electrical properties for CE 1 granulates have been collected in Table 1 and 2.

Comparative Example 2

(22) The same procedure as described in Example 2 was used except that potassium bis-oxalatoborate was replaced by sodium perchlorate monohydrate to give polymer designated as Comparative Example 2 (CE 2). The volume resistivity of the granulates, that were first dried for 3 h at 80 C. and then conditioned for 48 hours at 10 RH % and 20 C., was 210.sup.5. Thermal and electrical properties for CE 2 granulates have been collected in Tables 1-3.

Comparative Example 3

(23) The same procedure as described in Example 2 was used except that potassium bis-oxalatoborate was replaced by potassium p-toluenesulphonate to give polymer designated as Comparative Example 3 (CE 3). The volume resistivity of the granulates, that were first dried for 3 h at 80 C. and then conditioned for 48 hours at 10 RH % and 20 C., was 110.sup.6. Thermal and electrical properties for CE 3 granulates have been collected in Tables 1-3.

(24) TABLE-US-00001 TABLE 1 Temp. at 1% Temp. at 2% Temp. at 5% Example weight loss* weight loss* weight loss* MFI.sup.# Ex 1 340 378 406 18.9 Ex 2 332 350 398 7.7 CE 1 317 337 362 25.7 CE 2 315 330 351 14.0 CE 3 380 392 407 6.8 *Temperature at depicted weight loss, measured with TGA at the rate of 10 C./min in nitrogen atmosphere; .sup.#Melt flow index measured with 2.16 kg load at 190 C.

(25) TABLE-US-00002 TABLE 2 Volume resistivity of granulates soaked in water* After After After After Example Original/m 1 d/m 2 d/m 4 d/m 7 d/m Ex 1 1 10.sup.5 2 10.sup.5 3 10.sup.5 3 10.sup.5 8 10.sup.5 Ex 2 2 10.sup.5 3 10.sup.5 4 10.sup.5 3 10.sup.5 4 10.sup.5 CE 1 1 10.sup.5 3 10.sup.5 3 10.sup.5 4 10.sup.5 4 10.sup.5 CE 2 2 10.sup.5 4 10.sup.5 4 10.sup.5 4 10.sup.5 5 10.sup.5 CE 3 1 10.sup.6 1 10.sup.6 1 10.sup.6 3 10.sup.6 4 10.sup.6 *All samples were dried for 3 hours at 80 C. and then conditioned for 48 hours at 10RH % and 20 C. prior to measurement.

(26) TABLE-US-00003 TABLE 3 Volume resistivity behavior of granulates stored first at high RH % and then at low RH %* After After After After After 2 d at 15 min at 2 h at 6 h at 55 h at 80RH %/ 10RH %/ 10RH %/ 10RH %/ 10RH %/ Example m m m m m Ex 2 9 10.sup.4 9 10.sup.4 1 10.sup.5 2 10.sup.5 3 10.sup.5 CE 2 2 10.sup.4 2 10.sup.4 4 10.sup.4 6 10.sup.4 2 10.sup.5 CE 3 8 10.sup.4 9 10.sup.4 2 10.sup.5 3 10.sup.5 9 10.sup.5 *All measurements at 20 C.

Examples 3 and 4 and Comparative Examples 4-6

(27) In order to evaluate the performance and properties of the dissipative materials of the invention, the materials of the examples above were converted into final products by sheet extrusion. The exemplary materials (masterbatches) were dry blended with the host polystyrene as depicted in Table 4 to give the final materials (Example Materials 3 and 4, and Comparative Example Materials 4-6). The electrical properties of the polystyrene sheets have been collected in Table 5 and 6.

(28) TABLE-US-00004 TABLE 4 Constituents Amount Polystyrene, amount Example Masterbatch (w-%) (w-%) Ex 3 Ex 1 30 70 Ex 4 Ex 2 30 70 CE 4 CE 1 30 70 CE 5 CE 2 30 70 CE 6 CE 3 30 70

(29) TABLE-US-00005 TABLE 5 Resistance behavior of sheet soaked in water* Original After 1 d After 2 d Example SR/ MD/ TD/ SR/ MD/ TD/ SR/ MD/ TD/ Ex 3 4 10.sup.7 8 10.sup.7 9 10.sup.7 2 10.sup.10 5 10.sup.10 7 10.sup.10 .sup.# .sup.# .sup.# Ex 4 3 10.sup.8 4 10.sup.8 2 10.sup.9 1 10.sup.9 2 10.sup.9 5 10.sup.9 1 10.sup.9 2 10.sup.9 5 10.sup.9 CE 4 4 10.sup.7 6 10.sup.7 8 10.sup.7 1 10.sup.10 3 10.sup.10 4 10.sup.10 .sup.# .sup.# .sup.# CE 5 1 10.sup.8 2 10.sup.8 5 10.sup.8 5 10.sup.8 1 10.sup.9 3 10.sup.9 2 10.sup.9 5 10.sup.9 1 10.sup.10 CE 6 2 10.sup.9 4 10.sup.9 2 10.sup.10 3 10.sup.10 6 10.sup.10 2 10.sup.11 6 10.sup.10 1 10.sup.11 4 10.sup.11 After 5 d After 7 d Example SR/ MD/ TD/ SR/ MD/ TD/ Ex 3 2 10.sup.10 4 10.sup.10 5 10.sup.10 3 10.sup.10 7 10.sup.10 7 10.sup.10 Ex 4 2 10.sup.9 5 10.sup.9 1 10.sup.10 5 10.sup.9 7 10.sup.9 2 10.sup.10 CE 4 2 10.sup.10 4 10.sup.10 4 10.sup.10 4 10.sup.10 6 10.sup.10 8 10.sup.10 CE 5 7 10.sup.9 2 10.sup.10 5 10.sup.10 5 10.sup.10 1 10.sup.11 2 10.sup.11 CE 6 8 10.sup.10 2 10.sup.11 4 10.sup.11 3 10.sup.11 5 10.sup.11 6 10.sup.11 *All samples were dried for 3 hours at 80 C. and then conditioned for 48 hours at 10RH % and 20 C. prior to measurement; SR surface resistance, measured with ring probe (IEC61340-2-3); MD resistance in machine direction, measured with bar probe (ANSI ESD D-257); TD resistance in transverse direction, measured with bar probe (ANSI ESD D-257). .sup.#Not measured.

(30) TABLE-US-00006 TABLE 6 Resistance behavior of sheet stored first at high RH % and then at low RH %* Example SR/ MD/ TD/ SR/ MD/ TD/ SR/ MD/ TD/ After 2 d at After 15 min at After 1 h at 80RH % 10RH % 10RH % Ex 3 6 10.sup.6 2 10.sup.7 3 10.sup.7 4 10.sup.7 8 10.sup.7 9 10.sup.7 8 10.sup.7 2 10.sup.8 2 10.sup.8 Ex 4 5 10.sup.7 8 10.sup.7 1 10.sup.8 2 10.sup.8 2 10.sup.8 4 10.sup.8 3 10.sup.8 3 10.sup.8 1 10.sup.9 CE 4 9 10.sup.5 2 10.sup.6 3 10.sup.6 7 10.sup.6 1 10.sup.7 2 10.sup.7 4 10.sup.7 7 10.sup.7 9 10.sup.7 CE 5 1 10.sup.6 3 10.sup.6 5 10.sup.6 7 10.sup.6 1 10.sup.7 2 10.sup.7 1 10.sup.7 3 10.sup.7 4 10.sup.7 CE 6 2 10.sup.6 4 10.sup.6 1 10.sup.7 3 10.sup.7 3 10.sup.7 4 10.sup.7 1 10.sup.8 1 10.sup.8 3 10.sup.8 After 2 h at After 6 h at After 55 h at 10RH % 10RH % 10RH % Ex 3 8 10.sup.7 1 10.sup.8 2 10.sup.8 8 10.sup.7 1 10.sup.8 2 10.sup.8 8 10.sup.7 2 10.sup.8 2 10.sup.8 Ex 4 4 10.sup.8 5 10.sup.8 3 10.sup.9 4 10.sup.8 4 10.sup.8 2 10.sup.9 6 10.sup.8 7 10.sup.8 4 10.sup.9 CE 4 4 10.sup.7 7 10.sup.7 1 10.sup.8 4 10.sup.7 6 10.sup.7 1 10.sup.8 5 10.sup.7 9 10.sup.7 1 10.sup.8 CE 5 3 10.sup.7 5 10.sup.7 8 10.sup.7 9 10.sup.7 1 10.sup.8 3 10.sup.8 2 10.sup.8 2 10.sup.8 6 10.sup.8 CE 6 4 10.sup.8 4 10.sup.8 2 10.sup.9 9 10.sup.8 7 10.sup.8 5 10.sup.9 2 10.sup.9 1 10.sup.9 .sup.1 10.sup.10 *All measurements at 20 C.; SR surface resistance, measured with ring probe (IEC61340-2-3); MD resistance in machine direction, measured with bar probe (ANSI ESD D-257); TD resistance in transverse direction, measured with bar probe (ANSI ESD D-257).

(31) The electrical conductivity of the polymer blend according to the invention can be improved further, for example, with commercial antistatic compounds, softeners or other small-molecular hygroscopic compounds.

(32) While the present invention has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this invention may be made without departing from the spirit and scope of the present invention.