Patent Description:
Aliphatic polyamides, e.g. those based on PA12, find their applications in a variety of industries.

For example, PA12 or similar polyamides can be used to make shoe outsoles. Due to its transparency, the design pattern & colour of the midsole can be seen through the polymer outsole by human eyes.

For this application, it is sometimes desired to have higher stiffness and higher impact strength, to meet requirements regarding mechanical strength and wear resistance. For such reason, glass fibers and impact modifiers are normally added to modify the polyamides. However, the transparency of the polyamides will normally be impaired. From the perspective of aesthetic, it is sometimes desired to keep the transparency when the polyamides are modified to improve the mechanical properties.

<CIT> has disclosed polyamide moulding compounds consisting of thermoplastic synthetic, fiber-shaped aggregates, particulate filler material and additives, wherein the thermoplastic synthetic can be a polyamide mixture (e.g. aliphatic polyamide and impact modifiers), and the fiber-shaped aggregates can be high-strength glass fibers (e.g. S-<NUM> and S-<NUM> glass fibers from AGY). <CIT> and <CIT> deal also with polyamide compositions comprising aliphatic polyamide and S glass fibers.

Therefore, transparent polyamide compositions with high mechanical strength are needed. The transparent composition should have a haze value of <NUM> or less (determined as described in the examples section).

One objective of the present disclosure is to provide a polyamide composition with high transparency and high mechanical strength without using polyolefinic impact modifier and without using core-shell modifier with butadiene core and methyl methacrylate shell.

This objective of the present disclosure is achieved by a polyamide composition comprising:.

Another objective of the present disclosure is to provide moulding material comprising the polyamide composition of the present disclosure.

A further objective of the present disclosure is to provide moulded articles produced from the moulding material, wherein preferably the moulded article is for use in one of the following sectors: electrical equipment, sports items, optical equipment, sanitary and hygiene items, household equipment, communications technology, automobile technology, energy and drive technology, mechanical engineering, and medical equipment.

A further objective of the present disclosure is to provide a shoe outsole comprising the polyamide composition of the present disclosure.

The following description is used merely for illustration but is not to restrict the scope of the disclosure.

By the term "aliphatic polyamide", the present disclosure refers to polyamides with its monomer units being aliphatic. The aliphatic polyamides do not include those produced from aromatic monomers, being aromatic diamine, aromatic dicarboxylic acid, or aromatic aminocarboxylic acid. The aliphatic monomers may be open-chain (linear, branched) or alicyclic. The aliphatic monomers may be saturated or unsaturated.

The aliphatic polyamide according to the present disclosure comprises has on average <NUM>-<NUM> carbon atoms in a plurality of monomer units. The aliphatic polyamide may be producible from a combination of diamine and dicarboxylic acid, from an ω-aminocarboxylic acid and/or the corresponding lactam. The monomer units are therefore the units which derive from lactam, ω-aminocarboxylic acid, diamine or dicarboxylic acid.

To ensure a high transparency, the aliphatic polyamide is semi-crystalline. Higher crystallinity of polyamide may reduce transparency significantly.

Suitable aliphatic polyamides further include copolyamides which, based on suitable comonomer selection, comply with the proviso that at least one monomer unit has <NUM> to <NUM> carbon atoms, the copolyamide composed of laurolactam, decanediamine and dodecanedioic acid (co-PA12/<NUM>). As another example, the copolyamide may be copolymer of laurolactam and <NUM>-aminodecanoic acid (co-PA12/<NUM>).

It will be appreciated that the polyamide employed herein may also be compounds of appropriate aliphatic polyamides, sufficient mutual compatibility being advantageous.

Within the aliphatic polyamide, at least one monomer unit has <NUM> to <NUM> carbon atoms. The following polyamides are suitable by way of example:.

Preferably, the at least one polyamide is selected from the group consisting of PA610, PA106, PA612, PA126, PA613, PA136, PA10, PA1010, PA1011, PA812, PA128, PA11, PA1111, PA1110, PA1012, PA1210, co-PA12/<NUM>, co-PA12/<NUM>, co-PA11/<NUM>, PA913, PA139, PA814, PA148, PA12, PA1212, PA1113, PA1311, PA1014, PA1410, PA915, PA159, PA816, PA168, PA13, PA1313, PA1214, PA1412, PA1115, PA1511, PA1016, PA1610, and combinations thereof.

More preferably, the at least one polyamide is selected from the group consisting of PA613, PA11, PA1012, PA1210, PA12, PA1014, PA1410, PA13, PA1214, PA1412, and combinations thereof.

The content of polyamide in the polyamide composition is preferably <NUM>-<NUM> wt. %, more preferably <NUM>-<NUM> wt %, still preferably <NUM>-<NUM> wt. %, even more preferably <NUM>-<NUM> wt. When the content of polyamide is too high, e.g., more than <NUM> wt. %, the glass fiber is in a weight percentage less than <NUM> %. Thus, the polyamide composition may suffer from a weak mechanical strength and therefore it may fail to meet some requirements on mechanical properties. When the content of polyamide is too low, e.g., less than <NUM> wt. %, the glass fiber is in a high concentration. The resultant composition may suffer from high brittleness and low transparency.

The content of glass fiber is preferably <NUM>-<NUM> wt. %, more preferably <NUM>-<NUM> wt. %, still preferably <NUM>-<NUM> wt. %, even more preferably <NUM>-<NUM> wt-%. In cases in which the content of glass fiber is too high, e.g., more than <NUM> wt. %, the blend may suffer from significant haze, as well as an increased brittleness.

More preferably, the S glass fiber does not comprise B<NUM>O<NUM> and/or TiO<NUM>. And particularly preferably, the S glass fiber does not comprise further oxides.

Preferably, the S glass fiber comprises <NUM>-<NUM> wt. % SiO<NUM>, <NUM>-<NUM> wt. % Al<NUM>O<NUM>, <NUM>-<NUM> wt. % MgO, <NUM>-<NUM> wt. % CaO, <NUM>-<NUM> wt. % Na<NUM>O+K<NUM>O, and <NUM>-<NUM> wt. % Fe<NUM>O<NUM>, based on the total weight of the glass fiber. Compared to traditional glass, the S glass fiber contains lower content of calcium oxide and alkali oxides, but much higher content of magnesium oxide.

The polyamide composition according to the present disclosure contains neither polyolefinic impact modifier nor core-shell modifier with butadiene core and methyl methacrylate shell as described above. As known in the art, maleic anhydride-modified ethylene-propylene-diene terpolymer (EPDM), polyolefins, styrene block copolymers (SBCs), and core-shell modifier with butadiene core and methyl methacrylate shell are available for impact modification of polyamides and polyesters. The present disclosure avoids usage of such impact modifiers and achieves a polyamide composition with both high mechanical strength and high transparency.

The polyolefinic impact modifiers include, without limitation to, maleic anhydride modified EPDM, maleic anhydride grafted ethylene/propylene rubber, polypropylene, polyethylene, copolymers produced through copolymerization involving ethylene, propylene, butylene, butadiene, styrene, etc..

In order to maintain high transparency, it is preferable that:
the difference in the refractive indices between the polyamide component according to a) and the S glass fiber according to b) at room temperature is less than <NUM>, measured according to DIN EN ISO <NUM>:<NUM> by method A.

These refractive indices are determined to DIN EN ISO <NUM>:<NUM> by method A (Zeiss Abbe model A instrument, Schott KL <NUM> B lamp, white cold light source). However, for a particle size in the lower range, for instance below <NUM> and in particular below <NUM>, a high transparency is retained even at a relatively high difference in the refractive indices.

Preferably, the polyamide is transparent with a haze not greater than <NUM>%, more preferably not greater than <NUM>%, measured according to ASTM D1003 on injection moulded test specimens of <NUM> in thickness.

The polyamide composition according to the invention may comprise as constituents, in addition to the components according to a) and b), further additives preferably selected from flame retardants, stabilizers, plasticizers, fillers, nanoparticles, antistats, dyes, pigments, mould-release agents or flow assistants, with an total amount not greater than <NUM> wt. %, preferably not greater than <NUM> wt. % based on the total weight of the polyamide composition.

Preferably, the polyamide composition according to the invention consists of the above specified constituents.

The polyamide composition may be produced by melt mixing on suitable kneaders or compounding machines, discharging and comminution. A multiphase system is concerned here where the modifier is present in the polyamide matrix in finely disperse form. The melt mixing is realized according to conventional method in a kneading assembly, discharge generally in the form of a strand/extrudate and comminution generally by pelletizing, crushing, or grinding.

The polyamide composition may be used as major component of a moulding material. However, the moulding material may include one or more minor components, without departing from the scope of the disclosure, as appreciated by those skilled in the art.

The moulding material may be processed into moulded articles by melting and moulding by processes known to those skilled in the art such as selective laser sintering, composite filament fabrication, selective heat sintering, fusion deposition modelling, fused filament fabrication, injection moulding, extrusion, pressing, or rolling.

The moulded articles may be in used in one of the following sectors: electrical equipment, sports items, optical equipment, sanitary and hygiene items, household equipment, communications technology, automobile technology, energy and drive technology, mechanical engineering, or medical equipment. The moulded articles may fulfil flammability requirements of the relevant industries.

The disclosure is illustrated by way of example and comparative examples hereinbelow.

The following materials were employed in the reference, the examples (A1 through A6) and the comparative examples (B through H):.

Melt mixtures were produced on a Coperion ZSK-26mc co-rotating twin screw extruder, discharged, pelletized to obtain the polyamide compositions according to the recipe indicated in Table <NUM>, wherein the polyamides with/without impact modifier were dry blended and fed into the main port of extruder and then mixed at <NUM>, and the glass fibers were fed via a side feeder into the extruder.

The polyamide compositions in pellet form were processed on an injection moulding machine Engel VC <NUM>/<NUM> (melt temperature <NUM>; mould temperature <NUM>) to prepare specimens for mechanical performance tests.

Tensile modulus of elasticity, tensile stress at yield, tensile stress at break and elongation at break were determined by Zwick Z020 materials testing system according to ISO <NUM>, on ISO tensile specimens, type 1A, <NUM>×<NUM>×<NUM> at a temperature (<NUM>±<NUM>)°C, relative humidity (<NUM>±<NUM>)%.

Notched impact strength was determined by CEAST Resil Impactor <NUM>, according to ISO <NUM>/1eA (Charpy) on tensile specimens ISO <NUM> type 1A which were cut off two ends, <NUM>×<NUM>×<NUM> at a temperature (<NUM>±<NUM>)°C, relative humidity (<NUM>±<NUM>)%.

Hardness (shore D) was determined by Time group shore D hardness tester TH210, according to ISO <NUM>, on tensile specimens ISO <NUM> type 1A <NUM>×<NUM>×<NUM> at a temperature (<NUM>±<NUM>)°C, relative humidity (<NUM>±<NUM>)%.

The polyamide compositions in pellet form were further processed on an injection moulding machine Engel VC <NUM>/<NUM> (melt temperature <NUM>; mould temperature <NUM>) to prepare specimens for haze value test.

Haze value was determined at <NUM>, by Spectrophotometer CM-3600d from KONICA MINOLTA according to ASTM D1003 (CIE C illuminant) on a <NUM>-thickness plate of size <NUM>×<NUM>, and haze value was stated in percentage.

Ross flex test was determined by Lab Tech LAB-F2000 cold ross flexing tester, on ross flex specimens <NUM>×<NUM>×<NUM>, in bending degree <NUM>°-<NUM>°-<NUM>° for <NUM>,<NUM> turns, at a temperature (<NUM>±<NUM>)°C, relative humidity (<NUM>±<NUM>)%. Crack means hairline crack in the specimen's surface. Break means total break of the specimen.

The overall results are shown in Table <NUM> and <NUM>.

The inventive compounds A1 to A4 comprising S glass fiber as from <NUM> % to <NUM> % have high mechanical strength and a low haze value. They all passed the ross flex test.

Claim 1:
A polyamide composition, comprising:
a) <NUM>-<NUM> wt. % of at least one aliphatic polyamide, wherein at least one monomer unit has <NUM> to <NUM> carbon atoms, and wherein the aliphatic polyamide is semi-crystalline; and
b) <NUM>-<NUM> wt. % of an S glass fiber,
the wt. % of a) and b) being based on a total weight of the polyamide composition, wherein the polyamide composition comprises
neither polyolefinic impact modifier, comprising
<NUM> to <NUM> wt% of ethene-based monomer units,
<NUM> to <NUM> wt% of monomer units based on a <NUM>-alkene with <NUM> to <NUM> carbon atoms,
<NUM> to <NUM> wt% of monomer units based on another olefin, and
<NUM> to <NUM> wt% of monomer units based on an aliphatically unsaturated dicarboxylic acid anhydride,
based on the total weight of the polyolefinic copolymer impact modifier,
nor core-shell modifier which comprises the following:
a core which comprises <NUM> to <NUM> wt% of butadiene units and <NUM> to <NUM> wt% of styrene units, each based on the total weight of the core, wherein the core makes up <NUM> to <NUM> wt% of the core-shell modifier; and
a shell which comprises <NUM> to <NUM> wt% of methyl methacrylate units and <NUM> to <NUM> wt% of modifying monomer units, each based on the total weight of the shell, wherein the shell makes up <NUM> to <NUM> wt% of the core-shell modifier.