Patent Description:
Polyamide resins are used in a wide range of fields such as electric components, electronic components, and automotive components due to good properties thereof in terms of heat resistance, abrasion resistance, chemical resistance and flame retardancy. Particularly, in the automobile industry, metal components have been replaced by plastic components to achieve weight reduction. In particular, peripheral components of an engine compartment (i.e., under-the-hood components) are exposed to a high temperature environment for a long period of time and are produced using polyamide resin compositions having good heat resistance.

Typically, organic antioxidants such as phenol or phosphite antioxidants are widely used in order to secure high heat resistance stability of a polyamide resin composition. However, there is a limitation in improvement in characteristics of retaining good properties at high temperature over a long period of time (long-term heat resistance stability). Copper halide heat stabilizers, such as a CuI/KI mixture, which is known to provide good long-term heat resistance stability at high temperature as compared with organic antioxidants, have been used. However, copper is likely to discolor or precipitate over time, thereby causing problems when used in electrical, electronic, and automotive components.

Therefore, there is a need for a polyamide resin composition which has good properties in terms of heat resistance, long-term heat resistance stability, mechanical properties, and appearance characteristics.

<CIT> refers to a thermoplastic melt-mixed composition including: a semicrystalline polyamide resin; a polyepoxy compound including at least two or more epoxy groups; the polyepoxy compound having a number average molecular weight of less than <NUM>; one or more carboxylic acid compounds selected from the group consisting of polyacids, acid alcohols and combinations of these, the carboxylic acid compounds have a number average molecular weight of less than <NUM>; and optionally, reinforcing agent; polymeric toughener; and further additives.

<CIT> refers to a polyamide composition containing : <NUM>-<NUM> parts by mass of an aliphatic polyamide constituted by a diamine and dicarboxylic acid; and <NUM>-<NUM> parts by mass of a semi-aromatic polyamide comprising a dicarboxylic acid unit containing at least <NUM> mol% isophthalic acid, and a diamine unit containing at least <NUM> mol% of a diamine comprising <NUM>-<NUM> carbon atoms; the polyamide composition having a tanδ peak temperature of at least <NUM>, and a weight-average molecular weight Mw of <NUM>,<NUM>≤Mw≤<NUM>,<NUM>.

The background technique of the present invention is disclosed in <CIT>.

It is an aspect of the present invention to provide a polyamide resin composition having good properties in terms of heat resistance and long-term heat resistance stability, and a molded article formed of the same.

One aspect of the present invention relates to a polyamide resin composition. The polyamide resin composition according to the invention includes:
<NUM> parts by weight of the aromatic polyamide; <NUM> parts by weight to <NUM> parts by weight of the aliphatic polyamide resin, relative to <NUM> parts by weight of the aromatic polyamide resin; <NUM> parts by weight to <NUM> parts by weight of the polyacrylic acid, relative to <NUM> parts by weight of the aromatic polyamide resin; and <NUM> parts by weight to <NUM> parts by weight of the glass fibers, relative to <NUM> parts by weight of the aromatic polyamide resin; wherein the polyacrylic acid has a weight average molecular weight of <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, as measured by gel permeation chromatography (GPC).

The aromatic polyamide resin may include at least two of a repeat unit represented by Formula <NUM>, a repeat unit represented by Formula <NUM>, and a repeat unit represented by Formula <NUM>:
<CHM>
<CHM>
<CHM>
where R<NUM> and R<NUM> are each independently a C<NUM> to C<NUM> hydrocarbon group or a halogen atom, R<NUM>, R<NUM> and R<NUM> are each independently a C<NUM> to C<NUM> linear or branched alkylene group, and n<NUM> and n<NUM> are each independently an integer of <NUM> to <NUM>.

The aromatic polyamide resin may include <NUM> mol% to <NUM> mol% of the repeat unit represented by Formula <NUM> and <NUM> mol% to <NUM> mol% of the repeat unit represented by Formula <NUM>.

The aromatic polyamide resin may include <NUM> mol% to <NUM> mol% of the repeat unit represented by Formula <NUM>, <NUM> mol% to <NUM> mol% of the repeat unit represented by Formula <NUM>, and <NUM> mol% to <NUM> mol% of the repeat unit represented by Formula <NUM>.

The aliphatic polyamide resin may include at least one of polyamide <NUM>, polyamide <NUM>, polyamide <NUM>, polyamide <NUM>,<NUM>, polyamide <NUM>,<NUM>, polyamide <NUM>,<NUM>, polyamide <NUM>,<NUM>, polyamide <NUM>,<NUM>, and polyamide <NUM>,<NUM>.

The aliphatic polyamide resin and the polyacrylic acid be may present in a weight ratio of <NUM>:<NUM> to <NUM>:<NUM>.

The polyacrylic acid and the glass fibers may be present in a weight ratio of <NUM>:<NUM> to <NUM>:<NUM>,<NUM>.

The polyamide resin composition may have a heat deflection temperature (HDT) of <NUM> or higher, as measured at a heating rate of <NUM>/hr under a load of <NUM> kgf/cm<NUM> in accordance with ASTM D648.

The polyamide resin composition may have a tensile strength retention rate of <NUM>% or more, as calculated according to Equation <NUM>:.

Tensile strength retention rate (%) = (TS<NUM>/TS<NUM>)×<NUM>
where TS<NUM> denotes an initial tensile strength of a <NUM> thick specimen, as measured in accordance with ASTM D638 and TS<NUM> denotes a tensile strength of the specimen, as measured in accordance with ASTM D638 after the specimen is left in an oven at <NUM> or <NUM> for <NUM>,<NUM> hours.

Another aspect of the present invention relates to a molded article. The molded article is formed of the polyamide resin composition according to the invention.

A polyamide resin composition according to the present invention includes: (A) an aromatic polyamide resin; (B) an aliphatic polyamide resin; (C) a polyacrylic acid; and (D) glass fibers.

The aromatic polyamide resin according to the present invention serves to improve heat resistance, rigidity, and impact resistance of the polyamide resin composition. For example, the aromatic polyamide resin may include at least two of a repeat unit represented by Formula <NUM>, a repeat unit represented by Formula <NUM> and a repeat unit represented by Formula <NUM>, and may essentially include at least one of the repeat unit represented by Formula <NUM> and the repeat unit represented by Formula <NUM>. <CHM>
<CHM>
<CHM>.

In Formulas <NUM>, <NUM>, and <NUM>, R<NUM> and R<NUM> are each independently a C<NUM> to C<NUM> hydrocarbon group or a halogen atom; R<NUM>, R<NUM> and R<NUM> are each independently a C<NUM> to C<NUM> linear or branched alkylene group; and n<NUM> and n<NUM> are each independently an integer of <NUM> to <NUM>.

As used herein, the term C1 to C6 hydrocarbon group refers to a C1 to C6 alkyl group, a C2 to C6 alkenyl group, a C2 to C6 alkynyl group, and/or a C3 to C6 cycloalkyl group.

In some embodiments, the aromatic polyamide resin may include <NUM> mol% to <NUM> mol%, for example, <NUM> mol% to <NUM> mol%, of the repeat unit represented by Formula <NUM> and <NUM> mol% to <NUM> mol%, for example, <NUM> mol% to <NUM> mol%, of the repeat unit represented by Formula <NUM>.

In some embodiments, the aromatic polyamide resin can include the repeat unit represented by Formula <NUM> in an amount of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> mol% based on <NUM> mol% of the aromatic polyamide resin. Further, according to some embodiments, the repeat unit represented by Formula <NUM> can be present in an amount of from any of the foregoing amounts to any other of the foregoing amounts.

In some embodiments, the aromatic polyamide resin may include <NUM> mol% to <NUM> mol%, for example, <NUM> mol% to <NUM> mol%, of the repeat unit represented by Formula <NUM>, <NUM> mol% to <NUM> mol%, for example, <NUM> mol% to <NUM> mol%, of the repeat unit represented by Formula <NUM>, and <NUM> mol% to <NUM> mol%, for example, <NUM> mol% to <NUM> mol%, of the repeat unit represented by Formula <NUM>.

In some embodiments, the aromatic polyamide resin can include the repeat unit represented by Formula <NUM> in an amount of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> mol% based on <NUM> mol% of the aromatic polyamide resin. Further, according to some embodiments, the repeat unit represented by Formula <NUM> can be present in an amount of from any of the foregoing amounts to any other of the foregoing amounts.

In some embodiments, the aromatic polyamide resin can include the repeat unit represented by Formula <NUM> in an amount of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> mol% based on <NUM> mol% of the aromatic polyamide resin. Further, according to some embodiments, the repeat unit represented by Formula <NUM> can be present in an amount of from any of the foregoing amounts to any other of the foregoing amounts.

Within these ranges, the polyamide resin composition can have good properties in terms of heat resistance, rigidity, and impact resistance.

Here, the aromatic polyamide resin may be prepared by reacting an aromatic dicarboxylic acid including an R<NUM>-substituted or unsubstituted terephthalic acid or an alkyl ester thereof and/or R<NUM>-substituted or unsubstituted isophthalic acid or an alkyl ester thereof and optionally including adipic acid with a C<NUM> to C<NUM> linear or branched alkylene group-containing aliphatic diamine (for example, <NUM>,<NUM>-hexanediamine (hexamethylenediamine (HMDA)), <NUM>,<NUM>-heptanediamine, <NUM>,<NUM>-octanediamine, <NUM>,<NUM>-nonanediamine, <NUM>,<NUM>-decanediamine, <NUM>,<NUM>-undecanediamine, and <NUM>,<NUM>-dodecanediamine) by a known polymerization method.

In some embodiments, the aromatic polyamide resin may have a glass transition temperature of <NUM> to <NUM>, for example, <NUM> to <NUM>, as measured by differential scanning calorimetry (DSC). Within this range, the polyamide resin composition can have good properties in terms of heat resistance, rigidity, and impact resistance.

In addition, the aromatic polyamide resin may have an intrinsic viscosity [η] of <NUM> dL/g to <NUM> dL/g, for example, <NUM> dL/g to <NUM> dL/g, as measured using an Ubbelohde viscometer at <NUM> after dissolving the aromatic polyamide resin in a strong (<NUM>%) sulfuric acid solution to a concentration of <NUM>/dL. Within this range, the polyamide resin composition can have good properties in terms of heat resistance, rigidity, and impact resistance.

The aliphatic polyamide resin according to the present invention serves to improve impact resistance and processability of the polyamide resin composition together with the aromatic polyamide resin, and may be any typical aliphatic polyamide resin known in the art.

In some embodiments, the aliphatic polyamide resin may include polyamide <NUM>, polyamide <NUM>, polyamide <NUM>, polyamide <NUM>, polyamide <NUM>, and polyamide <NUM>,<NUM>, polyamide <NUM>,<NUM>, polyamide <NUM>,<NUM>, and polyamide <NUM>,<NUM>, and combinations thereof.

In some embodiments, the aliphatic polyamide resin may have a relative viscosity [ηrel] of <NUM> to <NUM>, for example, <NUM> to <NUM>, as measured using an Ubbelohde viscometer at <NUM> after dissolving the aliphatic polyamide resin in a strong (<NUM>%) sulfuric acid solution to a concentration of <NUM>/dL. Within this range, the polyamide resin composition can have good properties in terms of heat resistance, processability, and impact resistance.

The aliphatic polyamide resin is present in an amount of <NUM> parts by weight to <NUM> parts by weight, for example, <NUM> parts by weight to <NUM> parts by weight, relative to <NUM> parts by weight of the aromatic polyamide resin. In some embodiments, the polyamide resin composition can include the aliphatic polyamide resin in an amount of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> parts by weight, based on <NUM> parts by weight of the aromatic polyamide resin. Further, according to some embodiments, the aliphatic polyamide resin can be present in an amount of from any of the foregoing amounts to any other of the foregoing amounts. Within this range, the polyamide resin composition can have good properties in terms of heat resistance, processability, and impact resistance.

The polyacrylic acid according to the present invention serves to improve long-term heat resistance stability and appearance characteristics of the polyamide resin composition together with the aliphatic polyamide resin and the like, and may be a polyacrylic acid used in typical thermoplastic resin compositions.

The polyacrylic acid has a weight average molecular weight of <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, for example, <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, as measured by gel permeation chromatography (GPC). Within this range, the polyamide resin composition can have good properties in terms of long-term heat resistance stability and appearance characteristics.

The polyacrylic acid is present in an amount of <NUM> parts by weight to <NUM> parts by weight, for example, <NUM> parts by weight to <NUM> parts by weight, relative to <NUM> parts by weight of the aromatic polyamide resin. In some embodiments, the polyamide resin composition can include the polyacrylic acid in an amount of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> parts by weight, based on <NUM> parts by weight of the aromatic polyamide resin. Further, according to some embodiments, the polyacrylic acid can be present in an amount of from any of the foregoing amounts to any other of the foregoing amounts. Within this range, the polyamide resin composition can have good properties in terms of long-term heat resistance stability and appearance characteristics.

In some embodiments, the aliphatic polyamide resin and the polyacrylic acid may be present a weight ratio of <NUM>:<NUM> to <NUM>:<NUM>, for example, <NUM>:<NUM> to <NUM>:<NUM>. In some embodiments, the aliphatic polyamide resin and the polyacrylic acid may be present a weight ratio of <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>:<NUM>, <NUM>: <NUM>, or <NUM>:<NUM>. Within this range, the polyamide resin composition can have good properties in terms of heat resistance, long-term heat resistance stability, processability, and appearance characteristics.

The glass fibers according to the present invention serve to improve rigidity, impact resistance, and heat resistance of the polyamide resin composition, and may be glass fibers used in typical thermoplastic resin compositions.

In some embodiments, the glass fibers may have various shapes, such as fibrous, particulate, rod, needle, flake, and amorphous shapes, and may have various cross-sectional shapes, such as circular, elliptical, and rectangular cross-sectional shapes. For example, it is desirable in terms of mechanical properties that the glass fibers have circular and/or rectangular cross-sections.

In some embodiments, the glass fibers having a circular cross-section may have a cross-sectional diameter of <NUM> to <NUM> and a pre-processing length of <NUM> to <NUM>, and the glass fibers having a rectangular cross-section may have a cross-sectional aspect ratio of <NUM> to <NUM> and a pre-processing length of <NUM> to <NUM>. Within these ranges, the polyamide resin composition can have improved properties in terms of rigidity and processability.

The glass fibers are present in an amount of <NUM> parts by weight to <NUM> parts by weight, for example, <NUM> parts by weight to <NUM> parts by weight, relative to <NUM> parts by weight of the aromatic polyamide resin. In some embodiments, the polyamide resin composition can include the glass fibers in an amount of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> parts by weight, relative to <NUM> parts by weight of the aromatic polyamide resin. Further, according to some embodiments, the glass fibers can be present in an amount of from any of the foregoing amounts to any other of the foregoing amounts. Within this range, the polyamide resin composition can have good properties in terms of rigidity, impact resistance, and heat resistance.

In some embodiments, the polyacrylic acid and the glass fibers may be present in a weight ratio of <NUM>:<NUM> to <NUM>:<NUM>,<NUM>, for example, <NUM>: <NUM> to <NUM>:<NUM>. Within this range, the polyamide resin composition can have good properties in terms of rigidity, long-term heat resistance stability, appearance characteristics, impact resistance, and heat resistance.

In one embodiment, the polyamide resin composition may include a typical additive known in the art, as needed, without altering the effects of the present invention. Examples of the additive may include a flame retardant, an antioxidant, a lubricant, a release agent, a nucleating agent, an antistatic agent, a colorant, and mixtures thereof, without being limited thereto. In the polyamide resin composition, the additive may be present in an amount of <NUM> parts by weight to <NUM> parts by weight, for example, <NUM> parts by weight to <NUM> parts by weight, relative to <NUM> parts by weight of the aromatic polyamide resin.

In one embodiment, the polyamide resin composition may be prepared in pellet form by mixing the aforementioned components, followed by melt-extrusion in a typical twin-screw extruder at <NUM> to <NUM>, for example, <NUM> to <NUM>.

In some embodiments, the polyamide resin composition may have a heat deflection temperature (HDT) of <NUM> or higher, for example, <NUM> to <NUM>, as measured at a heating rate of <NUM>/hr under a load of <NUM> kgf/cm<NUM> in accordance with ASTM D648.

In some embodiments, the polyamide resin composition may have a tensile strength retention rate of <NUM>% or more, for example, <NUM>% to <NUM>%, as calculated according to Equation <NUM>. <MAT> where TS<NUM> denotes an initial tensile strength of a <NUM> thick specimen, as measured in accordance with ASTM D638 and TS<NUM> denotes a tensile strength of the specimen, as measured in accordance with ASTM D638 after the specimen is left in an oven at <NUM> for <NUM>,<NUM> hours.

In some embodiments, the polyamide resin composition may have a notched Izod impact strength of <NUM> kgf. cm/cm or higher, for example <NUM> kgf. cm/cm to <NUM> kgf. cm/cm, as measured on an <NUM>/<NUM>" thick specimen in accordance with ASTM D256.

A molded article according to the invention is formed of the polyamide resin composition set forth above. For example, the molded article may be manufactured using the polyamide resin composition by a known molding method, such as injection molding, double injection molding, blowing, extrusion, and thermoforming. The molded article may be easily formed by those skilled in the art to which the present invention pertains.

In some embodiments, the molded article may be used in various fields to which highly heat-resistant nylon is applied. In addition, since the molded article has good properties in terms of heat resistance, rigidity, hydrolysis resistance, moisture resistance, processability and balance therebetween and is usable for a long period of time at a high temperature of <NUM> or higher, the molded article is particularly useful as a material for an under-the-hood (UTH) component of an automobile engine compartment, which requires such physical properties.

Next, the present invention will be described in more detail with reference to some examples. It should be understood that these examples are provided for illustration only and are not to be in any way construed as limiting the present invention.

Details of components used in Examples and Comparative Examples are as follows:.

The aforementioned components were mixed in amounts as listed in Tables <NUM> and <NUM>. Then, the mixture was subjected to melt-extrusion in a twin-screw extruder (L/D: <NUM>, Φ: <NUM>) at a barrel temperature of <NUM>, thereby preparing a polyamide resin composition in pellet form. The prepared pellets were dried at <NUM> for <NUM> to <NUM> hours and then were subjected to injection molding using an injection machine under conditions of a cylinder temperature of <NUM> and a mold temperature of <NUM>, thereby preparing a specimen. The prepared specimen was evaluated as to the following properties. Results are shown in Tables <NUM> and <NUM>.

From the results shown in Tables <NUM> and <NUM>, it can be seen that the polyamide resin compositions according to the present invention (Examples <NUM> to <NUM>) had good properties in terms of heat resistance (heat deflection temperature), long-term heat resistance stability (tensile strength retention rate and blistering), impact resistance (notched Izod impact strength), and appearance characteristics (blistering).

Claim 1:
A polyamide resin composition comprising:
<NUM> parts by weight of an aromatic polyamide resin;
<NUM> parts by weight to <NUM> parts by weight of an aliphatic polyamide resin, relative to <NUM> parts by weight of the aromatic polyamide resin;
<NUM> parts by weight to <NUM> parts by weight of a polyacrylic acid, relative to <NUM> parts by weight of the aromatic polyamide resin; and
<NUM> parts by weight to <NUM> parts by weight of glass fibers, relative to <NUM> parts by weight of the aromatic polyamide resin,
wherein the polyacrylic acid has a weight average molecular weight of <NUM>,<NUM>/mol to <NUM>,<NUM>/mol, as measured by gel permeation chromatography (GPC).