INDUSTRIAL FAN OR BLOWER COMPRISING A FLAME-RETARDANT POLYAMIDE COMPOSITION

FIELD OF INVENTION

The present invention relates to a flame-retardant polyamide composition, a process for prepar ing the same and use thereof in industrial fan or blower.

BACKGROUND OF THE INVENTION

It is well-known in the art to produce flame-retardant polymer compositions for various applica tions. The requirement for various flame retardancy properties of the polymer composition vary depending on the intended final use of the polymer composition. For example, the requirements relating to heat release, smoke production, vertical flame propagation, smoke density, smoke acidity and melt viscosity may vary depending on the intended final use of the polymer composi tion. The requirements for other properties (e.g. mechanical properties such as stiffness and tensile strength) may also vary depending on the intended final use of the polymer composition. These properties may be affected by the additives that are included in the polymer composition to obtain the required flame-retardancy properties.

Polymer compositions, such as polyamide-based compositions blended with suitable flame-re tardants, are known in the art. These compositions typically employ polyamide 6 and/or polyam ide 66 and have been used for molding applications. Further, these compositions are known to have acceptable flame-retardant properties meeting the fire resistance requirements in accord ance with UL94 standard. In particular, the existing compositions are known to meet the flame- retardancy requirements of V-2 in accordance with the UL94 standard.

WO 2018/187638 A1 discloses a flame-retardant polymer composition comprising a polymer, a flame retardant, a high aspect ratio particulate material, and optionally a reinforcing material. This composition is disclosed to have a flame retardancy rating equal to or greater than V-2 when measured using the UL94 standard.

US 6,146,557 B1 relates to a fire-resistant composition having fire resistance as high as V-0 or more in a vertical flammability test in accordance with UL94 standard. The composition com prises 100 parts by weight of thermoplastic resin, 10 to 300 parts by weight of at least one flame-retardant selected from the group consisting of a nitrogen base flame retardant having no halogen atoms, a phosphorus base flame retardant having no halogen atoms and a nitrogen phosphorus base flame retardant having no halogen atoms, and 1 to 100 parts by weight of phyllosilicate hydrate.

EP 0,278,555 A1 discloses polyamide composition comprising a thermoplastic polyamide in an amount of at least 40 percent by weight of the composition, a flame-retardant consisting essentially of red phosphorus, said red phosphorus making upto 4 to 15 percent by weight of the composition, magnesium hydroxide in an amount of 5 to 40 percent by weight of the compo sition, and mineral reinforcing fibres in an amount of 5 to 50 percent by weight of the composi tion, the total amount of said flame retardant and said magnesium hydroxide being not more than 50 percent by weight of the composition. This composition is disclosed to have flame re- tardancy of V-0 according to UL94 standard.

The existing polymer compositions, particularly the polyamide-based compositions, have sev eral limitations. One such limitation is that the flame-retardancy of these compositions is not of the highest quality, i.e. these compositions meet the requirements of V-0, V-1 or V-2 in accord ance with UL94 standard. Further, these compositions do not provide for acceptable properties, such as but not limited to, tensile strength, %elongation, flexural strength and Charpy notch strength. Additionally, the presence of other ingredients, such as but not limited to, flame retard ants, for e.g. nitrogen based, and filler materials, for e.g. talc, render it difficult to process. More over, the existing polyamide compositions have not been disclosed to be used for industrial fans or blowers.

It was, therefore, an object of the present invention to provide a flame-retardant polyamide com position which can meet the highest quality of fire resistance, i.e. 5VA in accordance with UL94 standard, can be easily processed, and still showcase acceptable properties of tensile strength, %elongation, flexural strength and Charpy notch strength, thereby rendering it useful for making shaped articles, such as industrial fans or blowers.

SUMMARY OF THE INVENTION

Surprisingly, it has been found that the above-identified object is met by providing a flame-re tardant polyamide composition comprising, among others, a flame-retardant mixture having (i) 1.0 to 10.0 wt.% of red phosphorus, and (ii) 1.0 to 10.0 wt.% of magnesium hydroxide, based on the total weight of the flame retardant polyamide composition, wherein the weight ratio between (i) and (ii) in the flame retardant mixture is in between 1:5 to 5:1 , and wherein the flame-retard- ant composition has a viscosity number of at least 114 ml/g, determined according to ISO 307.

Accordingly, in one aspect, the presently claimed invention is directed to a flame-retardant poly amide composition comprising

(a) 20 wt.% to 60 wt.% of a polyamide having a viscosity number in between 90 ml/g to 350 ml/g determined according to ISO 307,

(b) 20 wt.% to 50 wt.% of a reinforcing agent,

(c) a flame-retardant mixture comprising (i) 1.0 to 10.0 wt.% of red phosphorus, and (ii) 1.0 to 10.0 wt.% of magnesium hydroxide, based on the total weight of the flame-retardant polyamide composition, wherein the weight ratio between (i) and (ii) in the flame-retardant mixture is in between 1:5 to 5:1,

(d) 0.1 wt.% to 10.0 wt.% of an impact modifier,

(e) 0.01 to 5.0 wt.% of a stabilizer, and

(f) 0.1 to 5.0 wt.% of a dispersing agent, wherein the flame-retardant polyamide composition has a viscosity number of at least 114 ml/g, determined according to ISO 307.

In another aspect, the presently claimed invention is directed to a process for preparing the above flame-retardant polyamide composition.

In yet another aspect, the presently claimed invention is directed to a shaped article comprising the above flame-retardant polyamide composition.

In still another aspect, the presently claimed invention is directed to an industrial fan or blower comprising the above flame-retardant polyamide composition.

DETAILED DESCRIPTION OF THE INVENTION

Before the present compositions and formulations of the invention are described, it is to be un derstood that this invention is not limited to particular compositions and formulations described, since such compositions and formulation may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the present inven tion will be limited only by the appended claims.

The terms "comprising", "comprises" and "comprised of as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of as used herein comprise the terms "consisting of, "consists" and "consists of".

Furthermore, the terms "first", "second", "third" or "(a)", "(b)", "(c)", "(d)" etc. and the like in the description and in the claims, are used for distinguishing between similar elements and not nec essarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illus trated herein. In case the terms "first", "second", "third" or “(A)”, “(B)” and “(C)” or "(a)", "(b)", "(c)", "(d)", "i", "ii" etc. relate to steps of a method or use or assay there is no time or time inter val coherence between the steps, that is, the steps may be carried out simultaneously or there may be time intervals of seconds, minutes, hours, days, weeks, months or even years between such steps, unless otherwise indicated in the application as set forth herein above or below. In the following passages, different aspects of the invention are defined in more detail. Each as pect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is in cluded in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment but may. Furthermore, the features, struc tures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some, but not other features included in other em bodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the appended claims, any of the claimed embodiments can be used in any combination.

Furthermore, the ranges defined throughout the specification include the end values as well, i.e. a range of 1 to 10 implies that both 1 and 10 are included in the range. For the avoidance of doubt, the applicant shall be entitled to any equivalents according to applicable law.

Flame-retardant polyamide composition

An aspect of the present invention is embodiment 1, directed to a flame-retardant polyamide composition comprising

(a) 20 wt.% to 60 wt.% of a polyamide having a viscosity number in between 90 ml/g to 350 ml/g, determined according to ISO 307,

(b) 20 wt.% to 50 wt.% of a reinforcing agent,

(c) a flame-retardant mixture comprising (i) 1.0 to 10.0 wt.% of red phosphorus, and (ii) 1.0 to 10.0 wt.% of magnesium hydroxide, based on the total weight of the flame-retardant poly amide composition, wherein the weight ratio between (i) and (ii) in the flame-retardant mixture is in between 1:5 to 5:1,

(d) 0.1 wt.% to 10.0 wt.% of an impact modifier,

(e) 0.01 to 5.0 wt.% of a stabilizer, and

(f) 0.1 to 5.0 wt.% of a dispersing agent, wherein the flame retardant polyamide composition has a viscosity number of at least 114 ml/g, determined according to ISO 307. In the present context, the phrases “composition” and “polyamide composition” are interchange ably used to refer to the flame-retardant polyamide composition of the embodiment 1.

In the present context, the phrase “ingredient” refers to (a), (b), (c), (d), (e), and (f) in the poly amide composition of the embodiment 1 , as described herein.

In the present context, the viscosity number is determined from a 0.5 wt.% solution of the poly amide composition in 96 wt.% sulfuric acid at 25°C, according to ISO 307.

In one embodiment, the viscosity number of the polyamide composition is required to be equal to or more than 114 ml/g. This is because a viscosity number of less than 114 ml/g tends to drip during the flame retardancy test, despite adding the flame retardants. This renders the composi tion unacceptable because dripping causes flame failure in the 5VA test.

In another embodiment, the flame-retardant polyamide composition in the embodiment 1 does not contain any talc or phyllosilicates, for e.g. phyllosilicate hydrate.

Polyamide

Suitable polyamides in the embodiment 1 have the viscosity number ranging between 90 ml/g to 350 ml/g, determined according to ISO 307. The polyamides are selected such that the viscosity number of the flame-retardant polyamide composition is at least 114 ml/g, as described herein.

In one embodiment, the viscosity number of the polyamide in embodiment 1 is in between 90 ml/g to 340 ml/g, or in between 100 ml/g to 340 ml/g, or in between 100 ml/g to 330 ml/g, or in between 100 ml/g to 320 ml/g, or in between 100 ml/g to 310 ml/g, or in between 100 ml/g to 300 ml/g. In other embodiment, it is in between 110 ml/g to 300 ml/g, or in between 110 ml/g to 290 ml/g, or in between 110 ml/g to 280 ml/g, or in between 110 ml/g to 280 ml/g, or in between 110 ml/g to 270 ml/g, or in between 120 ml/g to 270 ml/g, or in between 120 ml/g to 260 ml/g, or in between 120 ml/g to 250 ml/g, or in between 120 ml/g to 240 ml/g, or in between 120 ml/g to 230 ml/g, or in between 120 ml/g to 220 ml/g. In yet another embodiment, it is in between 130 ml/g to 220 ml/g, or in between 130 ml/g to 210 ml/g, or in between 140 ml/g to 210 ml/g, or in between 150 ml/g to 210 ml/g, or in between 150 ml/g to 210 ml/g, or in between 160 ml/g to 210 ml/g. In a further embodiment, it is in between 170 ml/g to 210 ml/g, or in between 180 ml/g to 210 ml/g.

In one embodiment, the polyamides in the embodiment 1 can be selected from aromatic and ali phatic polyamides. In another embodiment, the polyamide in the embodiment 1 comprises an aliphatic polyamide. In another embodiment, the polyamide in the embodiment 1 are, for example, derived from lac tams having 7 to 13 ring members or obtained by reaction of dicarboxylic acids with diamines. Examples of polyamides which are derived from lactams include polycaprolactam, polycaprylo- lactam, and/or polylaurolactam.

In yet another embodiment, the polyamides in the embodiment 1 also include those obtainable from w-aminoalkyl nitriles, such as but not limited to, aminocapronitrile, which leads to nylo-6. In addition, dinitriles can be reacted with diamine. For example, adiponitrile can be reacted with hexamethylenediamine to obtain nylon-6,6. The polymerization of nitriles is effected in the pres ence of water and is also known as direct polymerization.

When polyamides obtainable from dicarboxylic acids and diamines are used, dicarboxylalkanes (aliphatic dicarboxylic acids) having 6 to 36 carbon atoms, or 6 to 12 carbon atoms, or 6 to 10 carbon atoms can be employed. Aromatic dicarboxylic acids are also suitable. Examples of di carboxylic acids include adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and also terephthalic acid and/or isophthalic acid.

Suitable diamines include, for example, alkanediamines having 5 to 36 carbon atoms, or 6 to 12 carbon atoms, or 6 to 8 carbon atoms, and aromatic diamines, for example, m-xylylenediamine, di(4-aminophenyl)methane, di(4-aminocyclohexyl)methane, 2,2-di(4-aminophenyl)propane, 2,2- di(4-aminocyclohexyl)propane, and 1,5-diamino-2-methylpentane.

In other embodiment, the polyamide in the embodiment 1 may also include polyhexamethylene- dipamide, polyhexamethylenesebacamide, and polycaprolactam, and nylon-6/6,6, in particular having a proportion of caprolactam units in between 5 wt.% to 95 wt.%.

The non-exhaustive list which follows, comprises the aforementioned polyamides in the embodi ment 1.

AB polymers:

AA/BB polymers: PA PDA-T Phenyldiamine, terephthalic acid

In one embodiment, the polyamide in the embodiment 1 is selected from PA 6, PA 11 , PA 12, PA 66, PA 6.9, PA 6.10, and PA 6.12. In another embodiment, it is selected from PA 6, PA 11, PA 12, PA 66, and PA 6.9. In yet another embodiment, it is selected from PA 6, PA 12, and PA 66.

In a further embodiment, the polyamide in the embodiment 1 is selected from PA 6, PA 66, or a blend or a copolymer thereof. In still another embodiment, the polyamide in the embodiment 1 comprises PA 6.

Suitable amounts of the polyamide may be added to the composition in order to achieve the vis cosity number, as described herein. In one embodiment, the polyamide in the embodiment 1 is present in an amount in between 20 wt.% to 60 wt.%, based on the total weight of the composi tion. In another embodiment, it is present in an amount in between 20 wt.% to 60 wt.%, or in be tween 20 wt.% to 55 wt.%, or in between 25 wt.% to 55 wt.%. In yet another embodiment, it is present in an amount in between 25 wt.% to 50 wt.%, or in between 30 wt.% to 50 wt.%, or in between 30 wt.% to 45 wt.%. In still another embodiment, it is present in an amount in between 30 wt.% to 40 wt.%.

Reinforcing agent

The polyamide composition of the embodiment 1 also include reinforcing agents in suitable amounts. As is known in the art, the properties of the polyamide composition can be controlled using suitable reinforcing agents.

In one embodiment, the reinforcing agent in the embodiment 1 is selected from metal fiber, met- alized inorganic fiber, metalized synthetic fiber, glass fiber, carbon fiber, ceramic fiber, mineral fiber, basalt fiber, kenaf fiber, jute fiber, flax fiber, hemp fiber, cellulosic fiber, sisal fiber, and coir fiber. In another embodiment, it is selected from metalized synthetic fiber, glass fiber, carbon fi ber, ceramic fiber, mineral fiber, basalt fiber, kenaf fiber, and jute fiber. In yet another embodi ment, it is selected from glass fiber, carbon fiber, ceramic fiber, and mineral fiber. In a further embodiment, the reinforcing agent in the embodiment 1 is glass fiber.

For the purpose of the present invention, the reinforcing agent can be obtained in any shape and size. Further, the reinforcing agent can be subjected to suitable surface treating agent or sizing. For instance, the reinforcing agent can be subjected to surface treatment using coupling agents such as, but not limited to, a silane coupling agent, titanium coupling agent, aluminate coupling agent, urethane coupling agent and epoxy coupling agent. Any suitable techniques for surface treatment can be used for this purpose. For instance, any suitable coating process, such as but not limited to, dip coating and spray coating can be employed. In one embodiment, the urethane coupling agent comprises at least one urethane group. Suita ble urethane coupling agents for use with the reinforcing agents are known to the person skilled in the art, as for instance described in US pub. no. 2018/0282496. In one embodiment, the ure thane coupling agent comprises, for example, a reaction product of an isocyanate, such as but not limited to, m-xylylene diisocyanate (XDI), 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI) or isophorone diisocyanate (IPDI), and a polyester based polyol or a polyether-based polyol.

In another embodiment, the epoxy coupling agent comprises at least one epoxy group. Suitable epoxy coupling agents for use with reinforcing agents are known to the person skilled in the art, as for instance described in US pub. no. 2015/0247025 incorporated herein by reference. In one embodiment, the epoxy coupling agent is selected from aliphatic epoxy coupling agent, aro matic epoxy coupling agent or mixture thereof. Non-limiting example of aliphatic coupling agent includes a polyether polyepoxy compound having two or more epoxy groups in a molecule and/or polyol polyepoxy compound having two or more epoxy groups in a molecule. As aro matic coupling agent, a bisphenol A epoxy compound or a bisphenol F epoxy compound can be used.

Suitable amounts of these coupling agents, as described herein, are well known to the person skilled in the art. However, in one embodiment, the coupling agent can be present in an amount of 0.1 parts by mass to 10.0 parts by mass relative to 100 parts by mass of the reinforcing agent.

In one embodiment, the reinforcing agent in the embodiment 1 is present in between 20 wt.% to 50 wt.%, based on the total weight of the composition. In another embodiment, it is present in between 25 wt.% to 50 wt.%, or in between 25 wt.% to 45 wt.%. In yet another embodiment, it is present in between 30 wt.% to 45 wt.%, or in between 35 wt.% to 45 wt.%.

Flame-retardant mixture

The polyamide composition in the embodiment 1 comprises a flame-retardant mixture compris ing (i) 1.0 wt.% to 10.0 wt.% of red phosphorus, and (ii) 1.0 wt.% to 10.0 wt.% of magnesium hy droxide, based on the total weight of the flame-retardant polyamide composition, wherein the weight ratio between (i) and (ii) in the flame-retardant mixture is in between 1 :5 to 5:1.

In one embodiment, the red phosphorus in the embodiment 1 is present in between 1.0 wt.% to 9.5 wt.%, or in between 1.5 wt.% to 9.5 wt.%, or in between 1.5 wt.% to 9.0 wt.%. In another embodiment, it is present in between 2.0 wt.% to 9.0 wt.%, or in between 2.0 wt.% to 8.5 wt.%, or in between 2.5 wt.% to 8.5 wt.%. In yet another embodiment, it is present in between 2.5 wt.% to 8.0 wt.%, or in between 3.0 wt.% to 8.0 wt.%, or in between 3.0 wt.% to 7.5 wt.%. In still another embodiment, it is present in between 3.5 wt.% to 7.5 wt.%, or in between 3.5 wt.% to 7.0 wt.%, or in between 4.0 wt.% to 7.0 wt.%.

In the present context, magnesium hydroxide in the embodiment 1 is used as a flame-retardant synergist and may be surface treated with a conventionally known surface treating agent, if re quired. The amount of the surface treating agent per 100 parts by weight of the magnesium hy droxide is in between 0.1 to 10 parts by weight. The surface treating agent may include higher fatty acids such as oleic acid and stearic acid, alkali metal salts of these higher fatty acids, silane coupling agents such as vinylethoxysilane, vinyl-tris(2-methoxy)silane, gamma-methacry- loxypropyltrimethoxysilane, gamma-aminopropyltrimethoxysilane, beta-(3,4-epoxycyclo- hexyl)ethyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane, and gamma-mercapto- propyltrimethoxysilane, titanate-containing coupling agents such as isopropyltriisostearoyl titan- ate, isopropyltris(dioctylpyrophosphate)titanate, isopropyltri(N-aminoethyl-aminoethyl)titanate and iso-propyltridecylbenzenesulfonyl titanate, aluminum containing coupling agents such as acetoalkoxyaluminum diisopropyllate, and partially esterified products of orthophosphoric acid such as mono- or diestots from orthophosphoric acid and stearyl alcohol and partially esterified products from orthophosphoric acid or an alkali metal salt.

In one embodiment, the magnesium hydroxide in the embodiment 1 may be a powdered solid material, which may be coated or uncoated, as described above. The magnesium hydroxide is used in synergistic amounts, such that the weight ratio between red phosphorus (i) and magne sium hydroxide (ii) in the flame-retardant mixture is in between 1 :5 to 5:1. In another embodi ment, the ratio is in between 1 :4 to 5:1, or in between 1:4 to 4:1 , or in between 1 :3 to 4:1. In yet another embodiment, the weight ratio is in between 1:3 to 3:1, or in between 1 :2 to 3:1 , or in be tween 1 :2 to 2:1.

In another embodiment, the magnesium hydroxide in the embodiment 1 is present in an amount in between 1.0 wt.% to 9.5 wt.%, or in between 1.5 wt.% to 9.5 wt.%, or in between 1.5 wt.% to 9.0 wt.%. In another embodiment, it is present in between 2.0 wt.% to 9.0 wt.%, or in between 2.0 wt.% to 8.5 wt.%, or in between 2.5 wt.% to 8.5 wt.%. In yet another embodiment, it is pre sent in between 2.5 wt.% to 8.0 wt.%, or in between 3.0 wt.% to 8.0 wt.%, or in between 3.0 wt.% to 7.5 wt.%. In still another embodiment, it is present in between 3.5 wt.% to 7.5 wt.%, or in between 3.5 wt.% to 7.0 wt.%, or in between 4.0 wt.% to 7.0 wt.%.

In one embodiment, the composition of the embodiment 1 does not contain other flame retard ants, in particular the halogenated or non-halogenated nitrogen-based flame retardants.

Impact modifier Impact modifiers often also termed rubber or elastomeric polymer, for use in the present inven tion are, for instance, described in US 2014/03203631 A1 and US 2008/0070023 A1. Suitable impact modifiers are selected from (i) ethylene polymers and copolymers grafted with carboxylic acid, an anhydride thereof, maleimide or an epoxy compound; and (ii) olefin or acrylic acid or anhydride terpolymers and ionomers.

In the ethylene polymers and copolymers grafted with carboxylic acid, anhydride thereof, malei mide or epoxy compound, the carboxylic acid or anhydride thereof is selected from maleic acid, fumaric acid, itaconic acid, acrylic acid, crotonic acid, a C1 to C4 alkyl half ester of maleic acid and their anhydrides or derivatives, including maleic anhydride. Also, olefinic rubbers can also be used as suitable impact modifiers.

In one embodiment, the impact modifiers in the embodiment 1 are ethylene copolymers grafted with a carboxylic acid or any anhydride thereof, such as an ethylene copolymer grafter with ma leic anhydride. In other embodiment, the impact modifiers include maleic anhydride grafted eth ylene propylene diene terpolymer (EPDM) (maleic anhydride in between 2 wt.-% to 6 wt.-%); ethylene propylene grafted with maleic anhydride (maleic anhydride in between 0.5 wt.-% to 6 wt.-%); maleic anhydride grafted low density polyethylene (maleic anhydride in between 0.2 wt- % to 6 wt.-%); and ethylene butyl acrylate grafted with maleic anhydride (maleic anhydride in between 0.2 wt.-% to 6 wt.-%).

The olefin or acrylic acid or anhydride terpolymer and ionomer impact modifiers have polymer ized in-chain units derived from the monomers comprising: (a) ethylene, butylene, propylene and combinations thereof; (b) in between 2 wt.-% to 25 wt.-% of an acid selected from acrylic acid, methacrylic acid, and mixtures thereof; and (c) 0.1 wt.-% to 15 wt.-% of a dicarboxylic acid monomer selected from maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic an hydride, a C1 to C4 alkyl half ester of maleic acid, and a mixture of these dicarboxylic acid mon omers. In one embodiment, the terpolymer is an ethylene/methacrylic acid/maleic anhydride ionomer (in between 0.5 wt.-% to 12 wt.-% maleic anhydride). The ionomer can be formed by neutralization of carboxylic acid units in the terpolymer with metal ions selected from zinc, mag nesium, manganese and mixtures thereof, alone or in combination with sodium or lithium ions. The terpolymer may further include up to 40 wt.-% of C1 to C8 alkyl acrylate monomer units.

In one embodiment, the impact modifier in the embodiment 1 is present in between 0.1 wt.% to 10.0 wt.%, based on the total weight of the polyamide composition. In another embodiment, it is present in between 0.1 wt.% to 9.0 wt.%, or in between 0.2 wt.% to 9.0 wt.%, or in between 0.2 wt.% to 8.0 wt.%. In still another embodiment, it is present in between 0.3 wt.% to 8.0 wt.%, or in between 0.3 wt.% to 7.0 wt.%, or in between 0.4 wt.% to 7.0 wt.%. In yet another embodi ment, it is present in between 0.4 wt.% to 6.0 wt.%, or in between 0.5 wt.% to 6.0 wt.%, or in between 0.5 wt.% to 5.0 wt.%, or in between 0.5 wt.% to 4.0 wt.%. In a further embodiment, it is present in between 0.5 wt.% to 3.0 wt.%, or in between 0.5 wt.% to 2.0 wt.%.

Stabilizers

In the present context, stabilizers in the embodiment 1 include antioxidants and heat stabilizers.

Stabilizers include, such as but not limited to, organic stabilizers such as phosphorus stabilizers, hindered phenol stabilizers, hindered amine stabilizers, oxanilide stabilizers, organic sulfur sta bilizers and secondary aromatic amine stabilizers; and inorganic stabilizers such as copper compounds and halides.

Phosphite compounds include, for example, distearylpentaerythritol diphosphite, di- nonylphenylpentaerythritol diphosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4- ethylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-isopropylphenyl)pentaerythritol di phosphite, bis(2,4,6-tri-t-butylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-sec-bu- tylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-t-octylphenyl)pentaerythritol diphos phite, and bis(2,4-dicumylphenyl)pentaerythritol diphosphate.

Hindered phenol stabilizers include, for example, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxy- phenyl)propionate, 1 ,6-hexanediol bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], pentaeryth- ritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 3,9-bis[1,1-dimethyl-2-^-(3-t-butyl-4- hydroxy-5-methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxa spiro[5,5]undecane, triethylene glycol bis[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate], 3,5-di-t-butyl-4-hydroxybenzyl phosphonate diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)be nzene, 2,2-thiodiethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)prop ionate], tris(3,5-di-t-butyl-4-hy- droxybenzyl)isocyanurate, and N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxyhydrocinnamide ). Hindered amine stabilizers include, for example, well-known hindered amine compounds having a 2,2,6,6-tetramethylpiperidine skeleton. Specific examples of hindered amine compounds in clude 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6-tetramethylpiperidine, 4- acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-phenylacetoxy-2,2,6,6-tetramethylpiperidine, 4-ben- zoyloxy-2,2,6,6-tetramethylpiperidine, 4-methoxy-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-

2,2,6,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2,6,6-tetramethylpiperidine, 4-benzyloxy-

2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6-tetramethylpiperidine, 4-ethylcarbamoyloxy-

2,2,6,6-tetramethylpiperidine, 4-cyclohexylcarbamoyloxy-2,2,6,6-tetramethylpiperidine, 4-phe- nylcarbamoyloxy-2,2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4-piperidyl)carbonate, bis(2,2,6,6-tetramethyl-4-piperidyl)oxalate, bis(2,2,6,6-tetramethyl-4-piperidyl)malonate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)adipate, bis(2,2,6,6-tetramethyl-4-piperidyl)terephthalate, 1,2-bis(2,2,6,6-tetramethyl-4- piperidyloxy)ethane, a,a'-bis(2,2,6,6-tetramethyl-4-piperidyloxy)-p-xylene, bis(2,2,6,6-tetrame- thyl-4-piperidyltolylene)-2, 4-dicarbamate, bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylene-1,6- dicarba mate, tris(2,2,6,6-tetramethyl-4-piperidyl)benzene-1,3,5-tricarbox y late, tri s (2 , 2 , 6 , 6-tetra- methyl-4-piperidyl)benzene-1,3,4-tricarboxy late, 1-[2-{3-(3,5-di-t-butyl-4-hydroxyphenyl)propio- nyloxy}butyl]-4 -[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-te t ramethylpiperidine, the condensation product of 1,2,3,4-butanetetracarboxylic acid and 1,2,2,6,6-pentamethyl-4-pi- peridinol and b,b,b',b'-tetramethyl-3,9-[2,4,8,10-tetraoxaspiro(5,5)undeca ne]diethanol, the poly condensation product of dimethyl succinate and 1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetra- methylpiperidine, and 1,3-benzenedicarboxamide-N,N'-bis(2,2,6,6-tetramethyl-4-pipe ridyl).

Amine antioxidants refer to amine compounds other than the hindered amine stabilizers men tioned above, and include, for example, the reaction products of N-phenylbenzeneamine with 2,4,4-trimethylpentene, N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylene- diamine, N-phenyl-N'-(1 ,3-dimethylbutyl)-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylene- diamine, polymerized 1,2-dihydro-2,2,4-trimethylquinoline, and 6-ethoxy-1,2-dihydro-2,2,4-tri- methylquinoline.

Oxanilide stabilizers include 4,4'-dioctyloxyoxanilide, 2,2'-diethoxyoxanilide, 2,2'-dioctyloxy-5,5'- di-tert-butoxanilide, 2,2'-didodecyloxy-5,5'-di-tert-butoxanilide, 2-ethoxy-2'-ethyloxanilide, N,N'- bis(3-dimethylaminopropyl)oxanilide, 2-ethoxy-5-tert-butyl-2'-ethoxanilide and mixtures thereof with 2-ethoxy-2'-ethyl-5,4'-di-tert-butoxanilide, mixtures of o- and p-methoxy-disubstituted oxani- lides, mixtures of o- and p-ethoxy-disubstituted oxanilides.

Organic sulfur stabilizers include, for example, organic thioate compounds such as didodecyl thiodipropionate, ditetradecyl thiodipropionate, dioctadecyl thiodipropionate, pentaerythritol tetrakis(3-dodecylthiopropionate) and thiobis(N-phenyl^-naphthylamine); mercaptobenzimidaz- ole compounds such as 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, 2-mercap- tomethylbenzimidazole and metal salts of 2-mercaptobenzimidazole; dithiocarbamate com pounds such as metal salts of diethyldithiocarbamic acid and metal salts of dibutyldithiocar- bamic acid; and thiourea compounds such as 1,3-bis(dimethylaminopropyl)-2-thiourea and tributylthiourea; as well as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, nickel dibutyl dithiocarbamate, nickel isopropyl xanthate, and trilauryl trithiophosphite.

Secondary aromatic amine stabilizers preferably include compounds having a diphenylamine skeleton, compounds having a phenylnaphthylamine skeleton and compounds having a dinaph- thylamine skeleton. Specifically, compounds having a diphenylamine skeleton include p,p'-dial- kyldiphenylamine (wherein the alkyl group contains 8 to 14 carbon atoms), octylated diphenyla mine, 4,4'-bis(a,a-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonylamide)diphenylamine, N,N'-diphenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl-N'- (1 ,3-dimethylbutyl)-p-phenylenediamine and N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)- p-phenylenedi amine; compounds having a phenylnaphthylamine skeleton include N-phenyl-1- naphthylamine and N,N'-di-2-naphtyl-p-phenylenediamine; and compounds having a dinaphthyl- amine skeleton include 2, 2'-dinaphthylamine, 1 ,2'-dinaphthylamine and 1 ,T-dinaphthylamine.

Inorganic stabilizers include copper compounds and halides. Copper compounds are copper salts of various inorganic or organic acids excluding the halides described below. Copper may be either cuprous or cupric, and specific examples of copper salts include copper chloride, cop per bromide, copper iodide, copper phosphate, copper stearate as well as natural minerals such as hydrotalcite, stichitite and pyrolite.

In one embodiment, the stabilizer in the embodiment 1 is present in between 0.01 wt.% to 5.0 wt.%, based on the total weight of the composition. In another embodiment, it is present in be tween 0.01 wt.% to 4.0 wt.%, or in between 0.01 wt.% to 3.0 wt.%, or in between 0.01 wt.% to 2.0 wt.%.

Dispersing agent

The polyamide composition of the embodiment 1 also comprises the dispersing agent, which is added for the purpose of preventing coagulation, if any, in the flame-retardant mixture. In one embodiment, the dispersing agent in the embodiment 1 is selected from carboxylic amide-base wax, metal salt of higher fatty acid, and higher fatty acid ester compound.

The carboxylic amide-base wax may be exemplified by compounds obtained by dehydration re action between higher aliphatic monocarboxylic acid and/or polybasic acid and diamine. The higher aliphatic monocarboxylic acid is preferably saturated aliphatic monocarboxylic acid and hydroxycarboxylic acid having 16 or more carbon atoms, and is exemplified by palmitic acid, stearic acid, behenic acid, montanic acid, and 12-hydroxystearic acid. The polybasic acid is a dibasic or higher carboxylic acid and may be exemplified by aliphatic dicarboxylic acids such as maronic acid, succinic acid, adipic acid, sebacic acid, pimelic acid, and azelaic acid; aromatic dicarboxylic acids such as phthalic acid, and terephthalic acid; and alicyclic dicarboxylic acids such as cyclohexyl dicarboxylic acid and cyclohexyl succinic acid. The diamine may be exempli fied by ethylene diamine, 1,3-diaminopropane, 1,4-diaminobutane, hexamethylenediamine, m- xylylene diamine, tolylene diamine, p-xylylene diamine, phenylene diamine, and isophorone dia mine.

The carboxylic amide-base wax is preferably a compound obtained by a polycondensation reac tion among stearic acid, sebacic acid and ethylene diamine. For example, a compound obtained by a polycondensation reaction among 2 mol of stearic acid, 1 mol of sebacic acid, and 2 mol of ethylene diamine. The metal salt of higher fatty acid may be exemplified by metal salt of the above-described higher aliphatic monocarboxylic acid. For instance, calcium stearate, barium stearate, magne sium stearate, aluminum stearate, zinc stearate, and calcium montanite may be used in the em bodiment 1. The higher fatty acid ester compound may be exemplified by ester compound formed between the above-described higher aliphatic monocarboxylic acid and alcohol, and more specifically, stearyl stearate, glycerin stearate, and pentaerythritol stearate.

In one embodiment, the dispersing agent is present in an amount in between 0.1 wt.% to 5.0 wt.%, based on the total weight of the composition. In another embodiment, it is present in be tween 0.1 wt.% to 4.5 wt.%, or in between 0.1 wt.% to 4.0 wt.%, or in between 0.1 wt.% to 3.5 wt.%. In yet another embodiment, it is present in between 0.1 wt.% to 3.0 wt.%, or in between 0.1 wt.% to 2.5 wt.%, or in between 0.1 wt.% to 2.0 wt.%.

Additives

In one embodiment, the polyamide composition in the embodiment 1 further comprises addi tives. Suitable additives include, such as but not limited to, dyes, pigments, UV absorbers, an tistats, fungistats, bacteriostats, and IR absorbing materials.

Other additives may also be added to the polyamide composition. These include anti-dripping agents; copper-, phosphorus- or sulfur-containing thermal stabilizers; weatherability modifier; foaming agents; lubricants; plasticizers; fluidity modifiers; organic fillers; and nucleating agents.

Suitable amounts of these additives may be used in the present invention. In one embodiment, the polyamide composition in the embodiment 1 is present in an amount in between 0.1 wt.% to 10 wt.%, based on the total weight of the polyamide composition.

The ingredients and additives, as described herein, are selected such that the viscosity number of the composition is in between 114 ml/g to 300 ml/g, determined according to ISO 307. In one embodiment, the viscosity number of the composition in the embodiment 1 is in between 114 ml/g to 290 ml/g, determined according to ISO 307. In another embodiment, it is in between 114 ml/g to 280 ml/g, or in between 114 ml/g to 270 ml/g, or in between 114 ml/g to 260 ml/g. In yet another embodiment, it is in between 114 ml/g to 250 ml/g, or in between 114 ml/g to 240 ml/g, or in between 114 ml/g to 230 ml/g. In a further embodiment, it is in between 114 ml/g to 220 ml/g, or in between 114 ml/g to 210 ml/g, or in between 114 ml/g to 200 ml/g.

The synergistic amounts of the ingredients and additives, as described herein, results in the pol yamide composition meeting the highest quality of fire resistance, i.e. 5VA ratings in accordance with UL94 standard. The flammability test method is determined using the Underwriters Labora tories test method UL94. The standard determines the material’s tendency to either extinguish or spread the flame once the specimen has been ignited. Tests are generally conducted on a 5" ^c 1/2" specimen of the minimum approved thickness. For 5VA rating, test is performed on both bar and plaque specimens, and the flame ignition source is approximately five times as severe as that used for testing the other materials. The composition meets 5VA rating if the burning stops within 60 seconds on a vertical specimen, with no drips and plaque specimen not devel oping holes.

Further, the composition of the present invention can be easily processed, and still showcase acceptable properties of tensile strength, %elongation, flexural strength and Charpy notch strength, thereby rendering it useful for making shaped articles, such as industrial fans or blow ers.

Process

Another aspect of the present invention is embodiment 2, directed to a process for preparing the flame-retardant polyamide composition of the embodiment 1. The process of embodiment 2 comprises at least the step of compounding the ingredients and optionally the additives, as de scribed herein. Compounding per se is a technique which is well known to the person skilled in the art of polymer processing and manufacture and consists of preparing plastic formulations by mixing and/or blending the ingredients and optionally the additives of the embodiment 1 in a molten state. In one embodiment, mixing is carried out at a rotational speed ranging between 200 rpm to 320 rpm. It is understood in the art that compounding is distinct from blending or mixing processes conducted at temperatures below that at which the ingredients become mol ten. Compounding may, for example, be used to form a masterbatch composition. Compound ing may, for example, involve adding a masterbatch composition to a polymer to form a further polymer composition.

In one embodiment, the polyamide composition in the embodiment 2 may, for example, be ex truded. For example, compounding may be carried out using a screw, e.g. a twin screw. For ex ample, compounding may be carried out using a multi roll mill, for example a two-roll mill. For example, compounding may be carried out using co-kneader or internal mixer. The methods disclosed herein may, for example, include compression molding or injection molding. The in gredients and optionally the additives may be premixed and fed from a single hopper. The re sulting melt may, for example, be cooled, for example in water bath, and then pelletized.

Further, the polyamide composition in the embodiment 1 or 2 may, for example, be shaped into a desired form or article. Shaping of the polyamide composition may, for example, involve heat ing the composition to soften it. The polyamide composition of the embodiment 1 or 2 may, for example, be shaped by molding (e.g. compression molding, injection molding, stretch blow molding, injection blow molding, overmolding), extrusion, casting, or thermoforming. In one embodiment, the compounding in the embodiment 2 is carried out a temperature ranging between 220°C to 350°C.

Shaped article

Another aspect of the present invention is embodiment 3, directed to a shaped article compris ing the polyamide composition of the embodiment 1 or as obtained from embodiment 2. As the name suggests, the shaped article is any article obtained using the polyamide composition and shaped appropriately.

In one embodiment, the shaped article in the embodiment 3 is an industrial fan or blower. Industrial fan or blower

Yet another aspect of the present invention is embodiment 4, directed to an industrial fan or blower comprising the polyamide composition of the embodiment 1 or as obtained from embodi ment 2.

Industrial fans or blowers are machines whose primary function is to provide and accommodate a large flow of air or gas to various parts of a building or other structures, for e.g. manufacturing sites. This is achieved by rotating a number of blades, connected to a hub and shaft, and driven by a motor or turbine. The flow rates of these mechanical fans range from approximately 200 cubic feet (5.7 m ³ ) to 2,000,000 cubic feet (57,000 m ³ ) per minute. A blower is another name for a fan that operates where the resistance to the flow is primarily on the downstream side of the fan. There are many uses for the continuous flow of air or gas that industrial fans generate, in cluding, such as but not limited to, combustion, ventilation, aeration, particulate transport, ex haust, cooling, air-cleaning, and drying, to name a few. The industries served include, for e.g., electrical power production, pollution control, metal manufacturing and processing, cement pro duction, mining, petrochemical, food processing, cryogenics, and clean rooms.

Due to the high temperature operation of these industrial fans or blowers, it is pertinent that the material of construction is appropriately selected, more importantly having very high flame-re- tardancy. Accordingly, the present invention polyamide composition of the embodiment 1 or 2 may be employed for this purpose.

Illustrative embodiments of the present invention are listed below, but do not restrict the present invention. In particular, the present invention also encompasses those embodiments that result from the dependency references and hence combinations specified hereinafter. More particu larly, in the case of naming of a range of embodiments hereinafter, for example the expression "The process according to any of embodiments 1 to 4", should be understood such that any combination of the embodiments within this range is explicitly disclosed to the person skilled in the art, meaning that the expression should be regarded as being synonymous to "The process according to any of embodiments 1, 2, 3 and 4":

I. A flame-retardant polyamide composition comprising:

(a) 20 wt.% to 60 wt.% of a polyamide having a viscosity number in between 90 ml/g to 350 ml/g determined according to ISO 307,

(b) 20 wt.% to 50 wt.% of a reinforcing agent,

(c) a flame-retardant mixture comprising (i) 1.0 wt.% to 10.0 wt.% of red phosphorus, and (ii) 1.0 wt.% to 10.0 wt.% of magnesium hydroxide, based on the total weight of the flame-retardant polyamide composition, wherein the weight ratio between (i) and (ii) in the flame-retardant mixture is in between 1:5 to 5:1,

(d) 0.1 wt.% to 10.0 wt.% of an impact modifier,

(e) 0.01 wt.% to 5.0 wt.% of a stabilizer, and

(f) 0.1 wt.% to 5.0 wt.% of a dispersing agent, wherein the flame-retardant polyamide composition has a viscosity number of at least 114 ml/g, determined according to ISO 307.

II. The composition according to embodiment I, wherein the polyamide has a viscosity num ber in between 150 ml/g to 210 ml/g determined according to ISO 307.

III. The composition according to embodiment I or II, wherein the polyamide comprises an ali phatic polyamide.

IV. The composition according to one or more of embodiments I to III, wherein the polyamide is selected from polyamide 6, polyamide 66, or a blend or a copolymer thereof.

V. The composition according to one or more of embodiments I to IV, wherein the polyamide comprises polyamide 6.

VI. The composition according to one or more of embodiments I to V, wherein the amount of the polyamide is in between 30 wt.% to 40 wt.%, based on the total weight of the flame- retardant polyamide composition.

VII. The composition according to one or more of embodiments I to VI, wherein the reinforcing agent is selected from metal fiber, metalized inorganic fiber, metalized synthetic fiber, glass fiber, carbon fiber, ceramic fiber, mineral fiber, basalt fiber, kenaf fiber, jute fiber, flax fiber, hemp fiber, cellulosic fiber, sisal fiber and coir fiber.

VIII. The composition according to one or more of embodiments I to VII, wherein the reinforc ing agent is glass fiber. IX. The composition according to one or more of embodiments I to VIII, wherein the reinforc ing agent is subjected to a surface treatment agent.

X. The composition according to embodiment IX, wherein the surface treatment agent is a coupling agent comprising one or more of a silane coupling agent, titanium coupling agent, aluminate coupling agent, urethane coupling agent and epoxy coupling agent.

XI. The composition according to one or more of embodiments I to X, wherein the amount of the reinforcing agent is in between 35 wt.% to 45 wt.%, based on the total weight of the flame-retardant polyamide composition.

XII. The composition according to one or more of embodiments I to XI, wherein the weight ra tio between (i) and (ii) is in between 1:2 to 2:1.

XIII. The composition according to one or more of embodiments I to XII, wherein the amount of the impact modifier is in between 0.1 wt.% to 5.0 wt.%, based on the total weight of the flame-retardant polyamide composition.

XIV. The composition according to one or more of embodiments I to XIII, wherein the amount of the stabilizer is in between 0.01 wt.% to 2.0 wt.%, based on the total weight of the flame-retardant polyamide composition.

XV. The composition according to one or more of embodiments I to XIV, wherein the amount of the dispersing agent is in between 0.1 wt.% to 2.0 wt.%, based on the total weight of the flame-retardant polyamide composition.

XVI. The composition according to one or more of embodiments I to XV, wherein the flame-re tardant polyamide composition has a viscosity number in between 114 ml/g to 300 ml/g, determined according to ISO 307.

XVII. The composition according to one or more of embodiments I to XVI further comprising ad ditives.

XVIII. The composition according to embodiment XVII, wherein the additive is selected from dyes, pigments, UV absorbers, antistats, fungistats, bacteriostats, and IR absorbing mate rials.

XIX. The composition according to embodiment XVII or XVIII, wherein the amount of additive is in between 0.1 wt.% to 10 wt.%, based on the total weight of the flame-retardant polyam ide composition. XX. The composition according to one or more of embodiments I to XVIII, wherein the flame- retardant polyamide composition meets the fire resistance requirements of 5VA in accord ance with UL94 standard.

XXI. A process for preparing a flame-retardant polyamide composition according to one or more of embodiments I to XX, said process comprising at least the step of compounding:

(a) 20 wt.% to 60 wt.% of a polyamide having a viscosity number in between 90 ml/g to 350 ml/g determined according to ISO 307,

(b) 20 wt.% to 50 wt.% of a reinforcing agent,

(c) a flame-retardant mixture comprising (i) 1.0 to 10.0 wt.% of red phosphorus, and (ii) 1.0 to 10.0 wt.% of magnesium hydroxide, based on the total weight of the flame- retardant polyamide composition, wherein the weight ratio between (i) and (ii) in the flame-retardant mixture is in between 1:5 to 5:1,

(d) 0.1 wt.% to 10.0 wt.% of an impact modifier,

(e) 0.01 to 5.0 wt.% of a stabilizer, and

(f) 0.1 to 5.0 wt.% of a dispersing agent, and obtaining the flame-retardant polyamide composition having a viscosity number of at least 114 ml/g, determined according to ISO 307.

XXII. The process according to embodiment XXI, wherein the compounding is carried out at a temperature in between 220°C to 350°C.

XXIII. A shaped article comprising a flame-retardant polyamide composition according to one or more of embodiments I to XX or as obtained from the process according to embodiment XXI or XXII.

XXIV. The shaped article according to embodiment XXIII, wherein the shaped article is an indus trial fan or blower.

XXV. A shaped article comprising a flame-retardant polyamide comprising:

(a) 20 wt.% to 60 wt.% of a polyamide having a viscosity number in between 90 ml/g to 350 ml/g determined according to ISO 307,

(b) 20 wt.% to 50 wt.% of a reinforcing agent,

(c) a flame-retardant mixture comprising (i) 1.0 wt.% to 10.0 wt.% of red phosphorus, and (ii) 1.0 wt.% to 10.0 wt.% of magnesium hydroxide, based on the total weight of the flame-retardant polyamide composition, wherein the weight ratio between (i) and (ii) in the flame-retardant mixture is in between 1:5 to 5:1,

(d) 0.1 wt.% to 10.0 wt.% of an impact modifier,

(e) 0.01 wt.% to 5.0 wt.% of a stabilizer, and

(f) 0.1 wt.% to 5.0 wt.% of a dispersing agent, wherein the flame-retardant polyamide composition has a viscosity number of at least 114 ml/g, determined according to ISO 307 and the shaped article is an industrial fan or blower. XXVI. An industrial fan or blower comprising a flame-retardant polyamide composition according to one or more of embodiments I to XX or as obtained from the process according to em bodiment XXI or XXII.

XXVII. An industrial fan or blower comprising a flame-retardant polyamide composition compris ing: (a) 20 wt.% to 60 wt.% of a polyamide having a viscosity number in between 90 ml/g to

350 ml/g determined according to ISO 307,

(b) 20 wt.% to 50 wt.% of a reinforcing agent,

(c) a flame-retardant mixture comprising (i) 1.0 wt.% to 10.0 wt.% of red phosphorus, and (ii) 1.0 wt.% to 10.0 wt.% of magnesium hydroxide, based on the total weight of the flame-retardant polyamide composition, wherein the weight ratio between (i) and (ii) in the flame-retardant mixture is in between 1:5 to 5:1,

(d) 0.1 wt.% to 10.0 wt.% of an impact modifier,

(e) 0.01 wt.% to 5.0 wt.% of a stabilizer, and

(f) 0.1 wt.% to 5.0 wt.% of a dispersing agent, wherein the flame-retardant polyamide composition has a viscosity number of at least 114 ml/g, determined according to ISO 307.

EXAMPLES

The presently claimed invention is illustrated by the non-restrictive examples which are as fol lows:

Raw materials

Standard methods

General synthesis of flame-retardant polyamide composition

The details about the inventive and comparative polyamide composition is summarized in Table 1 below. All amounts in wt.%.

Table 1: inventive and comparative polyamide compositions n.d. = not determined

Polyamide compositions, both inventive and comparative, were extruded using WP 25mm la boratory twin-screw extruder at the above-mentioned process conditions. Another comparative example (Comp. Ex. 2) having Ultramid ^® B3G8 BK (polyamide 6 with 40% glass fiber) was used, but without containing the flame-retardant mixture according to the invention.

Mechanical testing and UL94 flame retardancy ISO type A bar samples having dimensions of 10.0 mm ^c 4.0 mm were prepared and tested for their mechanical properties in accordance with the respective standards. Additionally, samples having thickness of 2.0 mm were prepared and tested for flame retardance as per UL94 stand ard. The test results are summarized in Table 2 below.

Table 2: test results for inventive and comparative samples

It can be observed that the inventive polyamide compositions meet the flammability require ments of 5VA in accordance with UL94 standards, while the comparative formulations contain- ing red phosphorus alone (see Comp. Ex. 1) and not containing any flame retardant (see Comp. Ex. 2) in accordance with the present invention, did not meet the said requirements. Moreover, the inventive polyamide compositions have properties similar to the comparative formulations, which renders them suitable for the desired applications, in particular for industrial fan or blower.