WO2020025350A1

WO2020025350A1 - Fiber reinforced polyamide composition and molded part made thereof

Info

Publication number: WO2020025350A1
Application number: PCT/EP2019/069435
Authority: WO
Inventors: Chunxia SUN
Original assignee: Dsm Ip Assets B.V.
Priority date: 2018-08-03
Filing date: 2019-07-18
Publication date: 2020-02-06
Also published as: CN112533993A; TW202018011A

Abstract

The invention relates to a fiber reinforced polyamide composition and a molded part made thereof. The fiber reinforced polyamide composition comprises (A) 30 − 70 wt.% of a thermoplastic polyamide, (B) 10 − 60 wt.% of a fibrous reinforcing agent, and (C) 0.5 − 10 wt.% of a silicone-block-containing polymer.

Description

FIBER REINFORCED POLYAMIDE COMPOSITION AND MOLDED PART MADE

THEREOF

The present invention relates to a fiber reinforced polyamide composition comprising a thermoplastic polyamide, a fibrous reinforcing agent and a silicone-block-containing polymer. In a preferred embodiment the composition according to the invention comprises a flame retardant. The present invention also relates to a molded part made of the composition.

Fiber reinforced polyamide compositions comprising a thermoplastic polyamide and a reinforcing agent, as well as polyamide compositions comprising a thermoplastic polyamide, a reinforcing agent and a flame retardant, and molded parts made thereof are well known in the art, thereby employing the good properties, such as chemical and temperature resistance of the thermoplastic polyamide and mechanical strength and loadbearing properties of the fibrous reinforcing agent, and of the flame retardants imparting flame retardancy to molded parts, as required in many

applications.

Such reinforced polyamide compositions and reinforced flame retarded polyamide compositions can also pose problems of warpage. Warpage is the phenomenon of distortion of a molded part. It can occur directly after molding, or after ageing, or after annealing or after a heat treatment step, such as during a reflow soldering process. Molded parts are prone to warpage, in particular when the molded part has a long, extended shape in one direction or a wide extended shape in two directions, or a complex three-dimensional shape with thin parts. Reinforced polyamide compositions and the problem of warpage are described in several patent applications, including the following.

JP2001226579A is directed to a reinforced polyamide resin composition which is suitable in industrial products such as automobile components, electronic and electric parts, and industrial machine components. The molded products should have low warpage and excel in rigidity, strength, and heat resistance, and have durability resistance against antifreeze and resistance to vibrational fatigue. The solution proposed in JP2001226579A is a reinforced polyamide resin composition comprising (A) a polyamide, (B) an apatite compound and (C) an inorganic filler. The apatite compound must contain a phenolic solvent-insoluble organic substance.

US2010076137A is directed to a flame-retardant polyamide composition and a molded article produced from the composition. The molded article should be excellent in mechanical properties including stiffness, heat resistance and flame retardancy, and show low warpage during a reflow soldering process. The solution proposed in US2010076137A is a flame-retardant polyamide composition comprising 20 to 80 wt.% of a specific polyamide resin (A), 1 to 40 wt.% of a flame retardant (B), 5 to 60 wt.% of a glass fiber (C), and 0.5 to 5 wt.% of an auxiliary flame retardant (D). Preferably, the glass fiber (C) has a cross section having an aspect ratio of greater than 3.

JP10130494A is directed to a polyamide resin composition having high rigidity, low warpage, good surface smoothness and excellent appearance. The solution proposed in JP10130494A is a polyamide composition comprising 35 to 65wt.% of a mixed polyamide resin consisting of 50 to 95wt.% of a crystalline polyamide resin and 50 to 5wt.% of an amorphous polyamide resin, 10 to 60wt.% of a fibrous reinforcing agent and 5 to 55wt.% of a flat silicate. Preferred flat silicates include mica and talc.

JP2255764A also deals with the problem of reduction of warpage of a molded article produced by mixing (A) a crystalline polyamide (e.g. nylon 6 or nylon 46) with (B) a fibrous reinforcing material, meanwhile retaining heat- resistance, rigidity and impact strength of the molded article. JP2255764A suggests a method for preventing warpage of crystalline polyamide molded articles, by adding a specific amount (3-40 wt.%) of a specific amorphous copolymerized polyamide (C) to the resin composition.

The amorphous copolymerized polyamide (C) is derived from 50-10 mole % of isophthalic acid, 0-40 mole % of terephthalic acid, 45-5 mole % of hexamethylene diamine and 5-45 mole % of bis(4-amino-3-methylcyclohexyl)methane, [mole % based on the total acid content and the total diamine content] and preferably having a glass transition temperature of 100 ^°C or more and a relative viscosity of 1.2-3.

JP2014152322A aims to provide a polyamide resin composition having a high degree of fire retardancy (UL standard 94: V-0 with thickness of 0.8 mm), and excellent mechanical properties, toughness and low warpage. The solution put forward in JP2014152322A is a flame-retardant polyamide resin composition with a specific flame retardant combination containing 10-70 mass % of a polyamide resin (A), 1-40 mass % of organic phosphinate (B), 0.1-15.0 mass percent of a melamine polyphosphate-based compound (C), 0.1-30 mass percent of a phosphazene-based compound (D), and 10-60 mass percent of a fiber reinforced material (E).

US2010227122A describes portable electronic devices and suitable polyamide resin compositions compounded with a glass fiber. In US2010227122A it is mentioned that these devices are becoming thinner and lighter in weight in recent years, and therefore polyamide resin compositions suited as a material for use therein are required to have particularly excellent strength and low warpage. The polyamide resin composition according to the solution provided by US2010227122A, comprises (A) 60 to 34 wt.% of a polyamide resin, (B) a glass fiber having an elongated cross- section with an aspect ratio of 2.5 or more, and optionally (C) a glass fiber having a circular cross-section with a diameter of 3 to 30 (micrometer), wherein the ratio (by weight) of the component (B) to the component (C) is 3:7 to 10:0, and the amount of (B), or (B) and (C), is 40 to 66 wt.%, and wherein the polyamide composition shows a tensile strength of 200 MPa or higher.

W008120703A1 provides a solution for a glass fiber reinforced polyamide resin composition that simultaneously has good mechanical properties, low warpage and satisfactory weld strength that is suitable for formation of a thin molding, such as a chassis or housing of electronic equipment. The composition comprises 30 to 80 mass % of polyamide resin of 1.5 to 4.0 relative viscosity, 20 to 70 mass % of flat glass fiber with a flat section of 1.5 to 10 major diameter/minor diameter ratio, and an organic compound having at least two glycidyl groups or acid anhydride groups in each molecule, mixed in an amount of 0.05 to 4.0 parts by mass relative to 100 parts by mass of polyamide resin.

In view of the above there is an evident need for fiber reinforced polyamide compositions suited for producing molded parts with low warpage.

The aim of the present invention is therefore to provide a fiber reinforced polyamide composition, and a molded part made thereof having low warpage.

This aim has been achieved with the reinforced polyamide composition, and with the molded part according to the present invention.

The reinforced polyamide composition according to the invention, comprises (A) a thermoplastic polyamide, (B) a fibrous reinforcing agent, and (C) a silicone-block-containing polymer.

In a first preferred embodiment thereof, the composition comprises as a further component (D) a flame retardant.

In a second preferred embodiment thereof, the fibrous reinforcing agent comprises non-circular glass fibers, In a third preferred embodiment, the composition comprises (A) the thermoplastic polyamide, (B) the fibrous reinforcing agent comprising non-circular glass fibers, (C) the silicone-block-containing polymer and (D) the flame retardant.

In a fourth preferred embodiment, the reinforced polyamide composition according to the invention comprises less than 50 wt.% of the

thermoplastic polyamide (A), and 0.5 - 10 wt.% of the silicone-block-containing polymer (C), relative to the total weight of the composition. Such low polyamide content can be combined with a high content in fibrous reinforcing agent and fillers.

In a further embodiment of the invention, the molded part is made of the composition according to the invention, or any of the above preferred embodiments thereof.

The effect of the composition according to the invention, comprising the silicone-block-containing polymer (C), is that the molded part made thereof shows less warpage, compared to a molded part made of a similar composition not comprising the silicone-block-containing polymer. This effect is most emphasized in molded parts comprising an extended section with a large length/width ratio, and in molded parts subjected to heat treatment, such as in reflow soldering processes.

Silicones, also known as polysiloxanes and more precisely called polymerized siloxanes, consist of an inorganic silicon-oxygen backbone chain, which is a chain of alternating silicon atoms and oxygen atoms ( -Si-O-Si-O-Si-O-···), constructed from inorganic-organic monomers with organic side groups attached to the silicon atoms. These silicon atoms are tetravalent. Thus, silicones are polymers made up of repeating units of siloxane, combined with carbon, hydrogen, and sometimes other elements. Silicones have in general the chemical formula -[R2SiO]_n-. In this formula, n is the degree of polymerization and each R can independently be an alkyl group, a haloalkyl group, an aralkyl group, an alkenyl group, an aryl group or an aryl group substituted with an alkyl group, an alkoxy group, or a halogen atom.

With a silicone-block-containing polymer is herein understood a polymer that comprises at least a silicon block, i.e. polydiorganosiloxane block with an inorganic silicon-oxygen backbone chain. Herein the silicone-block-containing polymer may comprise one silicon block end-capped with mono-radical or mono-valent groups, as represented by Formula (I), or comprise more than one silicon block alternated with bi-radical or divalent groups, and end-capped with mono-radical groups, as

represented by Formula (II): X[R₂SiO]nY (I)

X([R₂SiO]nZ)x[R₂SiO]nY (II)

Herein X and Y represent mono-radical groups, functioning as end- groups, and Z represents a bi-radical group, functioning as alternating group. Herein X and Y can be different or can be the same. Herein Z can be polymer block of a chemical composition different from the polydiorganosiloxane block, or a residual part of a chain extender. In general, chain extenders are low molecular weight bifunctional compounds bearing functional groups capable of reacting with functional end-groups of a polymer. Instead of, or next to two functional components acting as a chain extender, the silicone-block-containing polymers may also comprise components with a higher functionality acting as a branching agent. Such branching agents are suitably used in small amounts to prevent cross-linking.

Silicone-block-containing polymers suitable for use in the

compositions can differ widely in chemistry and structure and include linear silicone- block-containing polymers as well as polydiorganosiloxane block copolymers. The silicone-block-containing polymer may have a molecular weight varying over a wide range. Suitably, the silicone-block-containing polymer has a weight average molecular weight (Mw) greater than 5,000 g/mol, or greater than 10,000 g/mol, and even greater than 25, 000. The Mw of the silicone-block-containing polymer can be as large as 100,000 g/mol, and even larger. The silicone-block-containing polymer may also comprise polysiloxane blocks have a degree of polymerization (n) varying over a wide range. Suitably, (n) is of least 3, preferably at least 5, or even more preferably at least 10. (n) suitably has a value of about 25, or about 50 or about 100, or about 200. (n) can be as high as about 300 or even higher. Preferably, (n) is in the range of 5 - 300.

Correspondingly, the polysiloxane blocks suitably have a weight average molecular weight (Mw) of at least about 500, preferably at least about 1000, for example about 2000, about 5,000, or about 10,000 or about 20,000, and suitably is up to 60,000, or even above.

The silicone-block-containing polymer used in the fiber reinforced polyamide composition according to the invention comprises at least a silicon block consisting of polysiloxane [represented by the chemical formula -[R₂SiO]_n-]; it may also comprise other polymeric building blocks or polymeric units. As a result, the content of polysiloxane in the silicone-block-containing polymer may vary. Suitably, at least 20 wt.%, preferably at least 40 wt.%, more preferably at least 60 wt.%, of the silicone- block-containing polymer consists of polysiloxane. The amount of polysiloxane in the silicone-block-containing polymer can be, for example, 30 wt.%, or 50 wt.%, or may be as high as 75 wt.% or 90 wt.% or even higher.

The silicone-block-containing polymer used in the composition according to the invention is melt processable. The silicone-block-containing polymer generally has a glass transition temperature (Tg) far below 0^°C and may well be as low as around minus 125 ^°C. However, the physical state may vary as different polymer blocks can be added, or that the silicon block is part of a segmented block copolymer or is functionalized with end groups. The physical state may vary from liquid to thick liquid, to waxy solid or even solid material, depending on molecular weight of the polymer and the glass transition temperature (Tg) or the melt temperature (Tm) of the other blocks. Preferably, the silicone-block-containing polymer employed in the preparation of the composition according to the invention is a waxy solid material or a solid material at room temperature.

The silicone-block-containing polymer in the composition according to the invention, and in the molded part made thereof, suitably are linear silicone-block- containing polymers comprising mono-radical end-groups bearing a functional group capable of reacting with the polyamide. This has the advantage of a better compatibility with the polyamide. Suitably, the copolymer comprises end-groups functionalized with a group selected from amine groups [the polymer suitably comprising alkylamine groups], hydroxyl groups [the polymer suitably comprising alkyl-alcohols], epoxy groups and carboxylic acids groups.

The silicone-block-containing polymer in the composition according to the invention, and in the molded part made thereof, suitably is a polydiorganosiloxane polyamide block copolymer, a polydiorganosiloxane polyurethane block copolymer, a polydiorganosiloxane polyether block copolymer, a polydiorganosiloxane polyester block copolymer, or a polydiorganosiloxane polycarbonate block copolymer. Herein the polydiorganosiloxane block copolymer suitably is a tri-block copolymer comprising one polydiorganosiloxane block end-capped with respectively polyamide blocks, or polyurethane blocks, or polyether blocks, or polyester blocks, or polycarbonate block. Preferably, the silicone-block-containing polymer comprises at least a

polydiorganosiloxane polyester block copolymer. Eventually, the silicone-block- containing polymer comprises at least a polydiorganosiloxane polyester tri-block copolymer. More particularly, the polydiorganosiloxane polyester tri-block copolymer may comprises polyester blocks comprising OH functional end-groups. In the silicone-block-containing polymer in the composition according to the invention, the silicon-oxygen back bone may comprise different substituents R, where R is an organic group; for example, an alkyl group, (for example, methyl, ethyl), or a phenyl or a substituted phenyl group, or an aralkyl group, or combinations thereof.

In the silicone-block-containing polymer in the composition according to the invention, the silicon carbon backbone is bearing substituent groups R, wherein R is an organic group such as an alkyl group, (for example, methyl, ethyl), or a phenyl or a substituted phenyl group, or an aralkyl group, or combinations thereof. Preferably, R comprises at least methyl groups.

Suitably, the silicone-block-containing polymer comprises at least a polydimethylsiloxane block, i.e. a block represented by the formula -[(Me)2SiO]_n-, or a polydiethylsiloxane block, or a polydiphenylsiloxane block, or any combination thereof, or any copolymer thereof, and preferably at least a polydimethylsiloxane block.

The silicone-block-containing polymer is suitably present in the composition according to the invention in an amount of 0.5 - 10 wt.%, preferably 1 - 8 wt.%, and more preferably 2 - 4 wt.%, relative to the total weight of the composition.

The thermoplastic polyamide in the composition according to the invention can be any thermoplastic polyamide usable for making molded parts.

Suitably, the thermoplastic polyamide comprises a semi-crystalline semi-aromatic polyamide, an amorphous semi-aromatic polyamide or an aliphatic polyamide, or any combination thereof.

Suitably the aliphatic polyamide is a polylactam [represented by the nomenclature polyamide X or PA-X, wherein X is an integer, representing a

polymerized lactam and the number of carbon therein] or a AABB type polyamide based on aliphatic diamine and aliphatic dicarboxylic acid [represented by the nomenclature polyamide XY or PA-XY, wherein X and Y are integers and X represent the diamine and Y represents the aliphatic dicarboxylic acid].

Examples of aliphatic polyamides are PA-6, PA-11 , PA-12, PA-66, PA-6/66, PA-46 and PA-410, and any copolymers thereof.

Examples of amorphous semi-aromatic polyamides are PA-6I/6T, PA-

MXDI, PA-MACT and PA-DT, and any copolymers thereof. Herein 6 represents hexamethylenediamine, I represent isophthalic acid, T represent terephthalic acid,

MXD represents mefa-xylylenediamine, MAC represents 3,3’-dimethyl-4,4’- diaminocyclohexylmethane and D represents 2-methyl-pentamethylenediamine. Suitably, the semi-crystalline semi-aromatic polyamide is a AABB type polyamide based on aliphatic diamine(s) and aromatic dicarboxylic acid(s)

[represented by the nomenclature polyamide XZ or PA-XZ] or based on aliphatic diamine(s), aliphatic dicarboxylic acid(s) and aromatic dicarboxylic acid(s) [represented by the nomenclature polyamide XY/XZ or PA-XY/XZ, or polyamide XZ/XY or PA- XZ/XY]]. Herein X is an integer and represents the diamine, Y represents the aliphatic dicarboxylic acid and Z represents the aromatic dicarboxylic acid.

Suitably, the semi-crystalline semi-aromatic polyamide is based on an aromatic dicarboxylic acid selected from terephthalic acid, naphthalene dicarboxylic acid and biphenyl dicarboxylic acid, or a combination thereof, optionally combined with isophthalic acid or an aliphatic dicarboxylic acid. The semi-crystalline semi-aromatic polyamide suitably is based on a diamine selected from linear aliphatic diamines, branched aliphatic diamines, cycloaliphatic diamines, arylalkyl diamines, and aromatic diamines. The linear aliphatic diamines suitably aw-alkyldiamines with 4-18 carbon atoms, for example 1 ,4-butanediamine, 1 ,6-hexamethylenediamine, 1 ,7- heptamethylenediamine, 1 ,8-diaminooctane, 1 ,9-diaminononane, 1 ,10-decanediamne and 1 ,12-dodecanediamine. Examples of branched aliphatic diamines are 2,2,4- trimethylhexanediamine, 2,4,4-trimethylhexanediamine, 2-methylpentanediamine and 2-methyloctanediamine. Examples of cycloaliphatic diamines are isophoronediamine and 1 ,4-dimethylcyclohexane. Examples of arylalkyl diamines are metaxylylenediamine and paraxylylenediamine.

Examples of semi-crystalline semi-aromatic polyamides are PA-6T/6I, PA-6T/66, PA-6T/10T, PA-4T/6T, PA-8T, PA-9T, PA-10T, PA-11T and PA-12T, and any copolymers thereof. Herein 6 in the position of X in the sequence of XY represents hexamethylenediamine, 6 in the position of Y in the sequence of XY represents adipic acid, 4 represents 1 ,4-butanediamine, 8 represents 1 ,8-diaminooctane, 9 represents 1 ,9-diaminononane, 10 represents 1 ,10-decanediamine, 11 represents 1 ,11- undecanediamine, 12 represents 1 ,12-dodecanediamine, MXD represents

metaxylylenediamine, D represents 2-methylpentamethylenediamine, I represents isophthalic acid, and T represents terephthalic acid.

In a preferred embodiment of the invention, the thermoplastic polyamide comprises a semi-crystalline polyamide with a melting point of at least 260 ^°C, more preferably at least 270 ^°C, still more preferably at least 280 ^°C. The advantage thereof is that the composition is better able to withstand elevated temperatures such as applied in a lead-free soldering process for SMT (surface mount technology) applications, while retaining a low warpage.

Herein, the melting temperature (Tm) is measured by the DSC method according to ISO-11357-1/3, 201 1 , on pre-dried samples in an N₂ atmosphere with heating and cooling rate of 20°C/min. Herein Tm has been calculated from the peak value of the highest melting peak in the first heating cycle.

The amount of polyamide in the composition according to the invention may vary over a wide range, and may be as low as, for example, about 20 wt.% or as high as, for example, about 80 wt.%. The polyamide is more suitably present in an amount of 30 - 70 wt.%, preferably 30 - 60 wt.%, and more preferably 40 - 60 wt.%. Herein the weight percentages (wt.%) are relative to the total weight of the composition.

The composition according to the invention comprises a fibrous reinforcing agent.

With fibers are herein understood elongated bodies or elongated particulates having an aspect ratio of length (L) over width (W) of at least 10. This in contrast with fillers, which are understood to be particulates having an aspect ratio of length (L) over width (W) of less than 10.

The fibrous reinforcing agent in the thermoplastic polymer composition according to the invention may comprise, for example, fibers selected from the group consisting of glass fibers, carbon fibers, metal fibers and mineral fibers. Preferably, the composition comprises at least glass fibers or carbon fibers, or a combination thereof. The glass fibers can, for example, be selected from A-glass, C- glass, D-glass, E-glass, H-glass, M-glass, R-glass and S-glass, or any mixtures thereof. Preference is given to glass fibers made of E-glass, or glass fibers from mixtures with E-glass and S-glass fibers.

The fibers may be round, i.e. having a circular cross-section, or non- circular, for example having a flat, oval, elliptical, oblong or rectangular cross-section. Among the glass fibers, flat glass fibers are particularly preferable.

Round or circular glass fibers suitably have a diameter of 5 to 20 pm, preferably from 5 to 15 pm and particularly preferably from 6 to 12 pm. The carbon fibers suitably have a diameter of 3 to 15 pm, preferably 4 to 12 pm, particularly preferably 4 to 10 pm.

The non-circular glass fibers suitably have a cross section with a width-over-thickness aspect ratio W/T of at least 1.5, preferably at least 2, and more preferably in the range of 2.5 - 6. Herein W represents the width, i.e. the largest dimension of the cross section and T represents the thickness, i.e. the smallest dimension of the cross section. Herein the cross-sectional dimensions width (W) and thickness (T) are measured on a cross-section of the fibers perpendicular to the length direction of the cross section.

The advantage of the composition comprising non-circular glass fibers is that the warpage of elongated molded parts made of the composition is further reduced.

The composition may contain long fibers (LFT fibers), chopped fibers (short fibers) or milled fibers, or any combination thereof. The chopped or short fibers suitably have a fiber length of 1 to 25 mm, preferably 1.5 to 20 mm, more preferably 2 to 12 mm and most preferably 2 to 8 mm.

Preferably, the composition comprises a combination of glass fibers and carbon fibers. Such a combination provides an optimum balance in mechanical properties, costs and weight reduction. Suitably, the fibers consist of 30 - 70 wt.% glass fibers and 70 - 30 wt.% of carbon fibers.

Also preferably, the composition comprises at least non-circular glass fibers. Suitably, the composition comprises non-circular glass fibers and either circular glass fibers or carbon fibers, or a combination thereof. In a preferred embodiment, the fibers consist of 30 - 70 wt.% flat glass fibers and 70 - 30 wt.% of circular glass fibers or carbon fibers or a combination thereof.

The amount of fibrous reinforcing agent in the composition according to the invention may vary over a wide range, and may be as low as, for example, about 5 wt.% or as high as, for example, about 65 wt.%. The fibrous reinforcing agent is more suitably present in an amount of 10 - 60 wt.%, preferably 20 - 60 wt.%, and more preferably 30 - 50 wt.%. Herein the weight percentages (wt.%) are relative to the total weight of the composition.

The composition according to the invention suitably comprises:

(A) 30 - 70 wt.% of the thermoplastic polyamide;

(B) 10 - 60 wt.% of the fibrous reinforcing agent; and

(C) 0.5 - 10 wt.% of the silicone-block-containing polymer;

wherein the weight percentages (wt.%) are relative to the total weight of the

composition.

In a preferred embodiment of the invention, the composition comprises a flame retardant (component (D)), next to the polyamide (A), the fibrous reinforcing agent (B) and the silicon-block-containing polymer (C). Many applications require molded parts that are flame retardant, have high mechanical strength and are dimensionally stable, after molding and even when going through temperature variations such as in reflow soldering processes. However, where flame retardancy can be achieved by adding sufficient flame retardant and high mechanical strength by adding sufficient fibrous reinforcing agent, while the content in polymer is reduced, this typically results in decreased warpage. With the presence of the silicon-block- containing polymer (C) in the composition according to the invention, the occurrence of warpage directly after molding, as well as after a heat treatment step as in a reflow soldering process, is further reduced.

The flame retardant in the composition according to the invention may be a halogen containing flame retardant, or a halogen-free flame retardant, or a combination thereof. Preferably, flame retardant comprises, or even better fully consists of a halogen-free flame retardant. Suitably, the halogen-free flame retardant, is a nitrogen (N), or phosphorous (P), or nitrogen (N) and phosphorous (P) containing halogen free flame retardant. More preferably, halogen-free flame retardant comprises, or even better fully consists of a metal phosphinate or a metal diphosphinate, or a combination thereof, or polymers thereof, herein together also referred to as metal salts of (di)phosphinic acids.

Suitable metal salts of (di)phosphinic acids that can be used in the composition according to the present invention are, for example, a phosphinate of the formula (III), a diphosphinate of the formula (IV),

or polymers of these wherein R1 and R2 are identical or different or are C1 - C6 alkyl, linear or branched, and/or aryl; R3 is C1 - C10-alkylene, linear or branched, C6 - C10 -arylene, -alkylarylene or -arylalkylene; M is one or more of calcium ions, magnesium ions, aluminum ions and zinc ions, m is 2 to 3; n is 1 or 3; x is 1 or 2. R1 and R2 may be identical or different and are preferably methyl, ethyl, n-propyl, isopropyl, n-butyl, tent-butyl, n-pentyl and/or phenyl. R3 is preferably methylene, ethylene, n-propylene, isopropylene, n-butylene, tert-butylene, n-pentylene, n-octylene, n-dodecylene, or phenylene or naphthylene, or methylphenylene, ethylphenylene, tert-butylphenylene, methylnaphthylene, ethylnaphthylene or tert-butylnaphthylene, or phenylmethylene, phenylethylene, phenylpropylene or phenylbutylene. M is preferably aluminum ions or zinc ions. These compounds are disclosed in U.S. Pat. No. 6,255,371 , which is hereby incorporated herein by reference.

Preferably the flame retardant (D) comprises an aluminum

(di)phosphinate. Suitable examples thereof are methylethyl(di)phosphinate and/or aluminum diethyl(di)phosphinate.

The flame retardant (D) is suitably present in an amount in the range of at least 5 wt.% and/or at most 30 wt.%, more particular at least 5 wt.% and/or at most 25 wt.%. Herein the weight percentages (wt.%) are relative to the total weight of the flame retardant polyamide composition. Preferably, the flame retardant (D) is present in an amount in the range of 5 - 25 wt.%, preferably 7.5 - 20 wt.% relative to the total weight of the composition. The amount of the metal (di)phosphinate comprised by the composition, if used as flame retardant, is suitably in the range of 5 - 25 wt.%, preferably 7.5 - 20 wt.%, relative to the total weight of the composition.

In a preferred embodiment of the invention, the composition comprises:

(D) 30 - 70 wt.% of the thermoplastic polyamide;

(E) 20 - 60 wt.% of the fibrous reinforcing agent;

(F) 0.5 - 10 wt.% of the silicone-block-containing polymer; and

(G) 5 - 25 wt.% of the flame retardant;

wherein the weight percentages (wt.%) are relative to the total weight of the composition.

In a more preferred embodiment, the composition comprises:

(A) 30 - 60 wt.% of the thermoplastic polyamide;

(B) 30 - 60 wt.% of the fibrous reinforcing agent;

(C) 1 - 8 wt.% of the silicone-block-containing polymer; and

(D) 7.5 - 20 wt.% of the flame retardant; and

The polyamide composition of the present invention may optionally comprise further components, such as other polymers and inorganic fillers , as well as additives selected from, for example, acid scavengers, impact modifiers, plasticizers, stabilizers [for example, thermal stabilizers, oxidative stabilizers, UV light stabilizers and chemical stabilizers], processing aids [for example, mold release agents and nucleating agents], solid lubricants, colorants [for example, carbon black, other pigments, dyes], nanoclays, etc. An impact modifier is advantageously included to further improve impact resistance e.g. for parts and housings for electronic devices.

Fillers that may be used are all particulate fillers known to those skilled in the art. These include, in particular, particulate fillers selected from the group consisting of minerals, talc, mica, dolomite, silicates, quartz, wollastonite, kaolin, silicic acids, magnesium carbonate, magnesium hydroxide, chalk, ground glass, glass flakes, metal flakes, metal-coated particles, ground carbon fibers, ground mineral fibers, ground glass fibers, ground or precipitated calcium carbonate, lime, feldspar, barium sulfate, permanent magnetic or magnetizable metals or alloys, glass beads, hollow glass beads, hollow spherical silicate fillers and mixtures thereof.

The composition according to the invention suitably comprises at least one further component (E). The at least one further component (E) is suitably present in an amount in the range of 0.01 - 40 wt.%, preferably 0.05 - 25 wt.%, relative to the total weight of the composition.

According a preferred embodiment, the composition consists of

(A) 30 - 70 wt.% of the thermoplastic polyamide;

(B) 20 - 60 wt.% of the fibrous reinforcing agent;

(C) 0.5 - 10 wt.% of the silicone-block-containing polymer;

(D) 0 - 25 wt.% of the flame retardant; and

(E) 0.01 - 40 wt.% of at least one further component;

wherein the weight percentages (wt.%) are relative to the total weight of the

composition.

In a more preferred embodiment, the composition comprises:

(A) 30 - 60 wt.% of the thermoplastic polyamide;

(B) 30 - 60 wt.% of the fibrous reinforcing agent;

(C) 1 - 8 wt.% of the silicone-block-containing polymer;

(D) 5 - 20 wt.% of the flame retardant; and

(E) 0.05 - 25 wt.% of at least one further component;

wherein the weight percentages (wt.%) are relative to the total weight of the

composition. Suitably, the at least one further component herein is one or more of the inorganic fillers and additives mentioned above.

The invention also relates to a molded made of the composition according to the present invention or any of the particular or preferred embodiments thereof as described above.

The composition according to the invention is suitably used for molded parts, being for example, a connector for an electronic device (e.g. a DDR connector), or a frame for an electronic device (e.g. C-frames) or a part of frame for an electronic device, or an engine part (e.g. a crank shaft cover).

The molded part according to the invention suitably comprises an extended section, wherein the extended section has a length (L) and a width (W) with a length / width ratio (L/W) of at least 5, preferably at least 10, and/or a width (W) and a thickness (T) with a width / thickness ratio (W/T) of at least 10, preferably at least 20. The invention is further illustrated with the following Examples and

Comparative Experiments.

Materials

Polyamide PA-6T/4T/66 copolymer, Tm = 325^°C, VN=75ml/g

Glass fibers Standard grade for polyamides, chopped fibers, round, diameter

10 pm (micrometer)

Flame retardant Aluminium diethylphosphinate (Exolit OP1230)

Silicone-block-containing polymer

Polyesterpolysiloxane block copolymer, comprising about 35 wt.% of polydimethylsiloxane (PDMS) blocks.

Additive package: Standard stabilizer and mold release agent

Compounding

Flame retardant polyamide compositions of Example I and

Comparative Experiment A were prepared on a twin-screw extruder. The temperature of the extruded melt was typically about 350 °C, so well above 325 °C of the melting temperature of the polyamide. After the melt compounding the resulting melt was extruded into strands, cooled, and cut into granules. The compositions and test results have been summarized in Table 1. Injection molding

The flame retardant polyamide compositions were injection molded into appropriate test molds to form test bars conforming ISO 527 type 1A using a standard injection molding machine. The settings were such that the melts of the compositions reached a temperature of about 340 °C. For the mechanical testing, test bars with a thickness of 4 mm were made. For the UL 94 burning test, test bars of 0.4 mm thickness were made. The test bars were used to measure the flame retarding properties and mechanical properties of the compounds, the results of which have been reported in Table I.

For the warpage test, a mold with a mold cavity for making

connectors was used. For the injection molding the same conditions as mentioned above for the ISO 527 type 1 A test bars were used, and injection gate was at one end of the part. The molded products comprised an extended part having the following dimensions: length about 140 mm, width about 6 mm, height about 5 mm.

Test methods

Viscosity number

Viscosity number (VN) was determined in 96% sulphuric acid solution with a concentration of 0.5g/dl_ by the method according to ISO 307: 2007-05 (E).

Mechanical properties

The mechanical properties (tensile modulus [MPa], tensile strength [MPa], elongation at break [%]) were measured in a tensile test according to ISO 527 at 23°C and 5 mm/min.

Flame retardancv

Flame retardancy was determined according Underwriters

Laboratories test method UL 94, using 0.4 mm test bars, conditioned for 48 hours at 23°C, 50% relative humidity, respectively for 168 hours at 70°C.

Warpage

Warpage was measured on the products directly after molding and after running through a reflow temperature profile. For the reflow test a standard Sony profile with peak temperature of 260°C was used. The molded parts were placed on a flat surface on the side with the 6 mm width, thus contacting the surface at at least two points. These contact points were identified and used as reference points. The part was turned on one of its 5 mm sides. A reference line was drawn through the reference points with the help of a laser beam. Six points evenly distributed over the length of the molded part were selected and the distance of the six selected points from the reference line were recorded. The average and the standard deviation of the six measurements were calculated.

The results for the molded part made with the compositions of Example I and Comparative A are reported in Table 1.

Table 1. Composition and test results for Example I (EX-I) and Comparative

Experiment (CE-A).

The results show that the composition according to the invention (Example I) results in a molded product exhibiting less warpage, both as molded and after the reflow test, than the corresponding composition of Comparative Experiment A not comprising a silicone-block-containing polymer. Apart from a higher average warpage for CE-A, also the standard deviation for the warpage of CE-A is higher. This is an indication that deformation in the molded part of CE-A is also more irregular than for the molded part of EX-1.

Claims

CLAIMS l. Fiber reinforced polyamide composition comprising (A) a thermoplastic

polyamide, (B) a fibrous reinforcing agent, and (C) a silicone-block-containing polymer.

2. Fiber reinforced polyamide composition according to claim 1 , further comprising (D) a flame retardant.

3. Fiber reinforced polyamide composition according to claim 1 or 2, wherein the silicone-block-containing polymer comprises a silicone block represented by the chemical formula -[R2SiO]_n-, having a degree of polymerization (n) of in the range of 5 - 300.

4. Fiber reinforced polyamide composition according to any of claims 1-3, wherein at least 20 wt.% of the silicone-block-containing polymer consists of polysiloxane.

5. Composition according to any of claims 1-4, wherein the silicone-block- containing polymer comprises a functionalized polydiorganosiloxane -polymer, preferably comprising end-groups functionalized with a group selected from amine groups, hydroxyl groups, epoxy groups and carboxylic acid groups, or a polydiorganosiloxane block copolymer, preferably comprising a

polydiorganosiloxane polyamide block copolymer, a polydiorganosiloxane polyurethane block copolymer, a polydiorganosiloxane polyether block copolymer, a polydiorganosiloxane polyester block copolymer, or a

polydiorganosiloxane polycarbonate block copolymer.

6. Composition according to any of the claims above, wherein thermoplastic

polyamide comprises a semi-crystalline semi-aromatic polyamide, an amorphous semi-aromatic polyamide or a semi-crystalline aliphatic polyamide, or any combination thereof.

7. Composition according to any of the claims above, wherein thermoplastic

polyamide comprises a semi-crystalline polyamide with a melting point of at least 270^°C.

8. Composition according to any of the claims above, wherein the fibrous

reinforcing agent comprises glass fibers, preferably comprising non-circular glass fibers having a cross section with a width-over-thickness aspect ratio W/T of at least 1.5.

9. Composition according to any of the claims above, wherein flame retardant comprises a halogen free flame retardant, preferably a nitrogen (N), or phosphorous (P), or nitrogen (N) and phosphorous (P) containing halogen free flame retardant, preferably comprising a metal phosphinate or a metal diphosphinate, or a combination thereof.

10. Composition according to any of the claims above, comprising

(A) 30 - 70 wt.% of the thermoplastic polyamide;

(B) 20 - 60 wt.% of the fibrous reinforcing agent;

(C) 0.5 - 10 wt.% of the silicone-block-containing polymer;

(D) 5 - 25 wt.% of the flame retardant; and

11. Composition according to any of the claims above, comprising at least one further component in an amount in the range of 0.01 - 40 wt.%, preferably 0.05 - 25 wt.%, relative to the total weight of the composition.

12. Composition according to any of the claims above, wherein the composition consists of:

(A) 30 - 70 wt.% of the thermoplastic polyamide;

(B) 20 - 60 wt.% of the fibrous reinforcing agent;

(C) 0.5 - 10 wt.% of the silicone-block-containing polymer;

(D) 0 - 25 wt.% of the flame retardant; and

(E) 0.01 - 40 wt.% of at least one further component;

13. Composition according to any of the claims above, wherein the composition comprises less than 50 wt.% of the thermoplastic polyamide (A), and 0.5 - 10 wt.% of the silicone-block-containing polymer (C), relative to the total weight of the composition.

14. Molded part, wherein the molded part is made of a composition according to any of the claims above.

15. Molded part according to claim 18, being a connector for an electronic device, or a frame for an electronic device, or a part of a frame for an electronic device, or an engine part.

16. Molded part according to claim 18 or 19, comprising an extended section, wherein the extended section has a length and a width with a ratio of length / width of at least 5, preferably at least 10, and/or a width and a thickness with a ratio of width / thickness of at least 10, preferably at least 20.