Claims:CLAIMS

We claim:
1. A crosslinkable flame retardant composition, comprising: a polyamide; a crosslinking agent, wherein the crosslinking agent comprises two or more groups capable of forming free radicals under beta or gamma radiation; and a flame retardant system comprising a halogenated flame retardant in combination with metal oxide flame retardant.
2. The compound of claim 1, wherein the polyamide is selected from the group consisting of polyamide -6, polyamide-6,6, polyamide -4, polyamide-4,6, polyamide-12, polyamide-6,10, polyamide-6,9, polyamide 11, polyamide 6,12, polyamide -9T, copolymer of polyamide -6,6 and polyamide -6, polyamide copolymers, polyamide blends and it’s combinations with the relative viscosity range between 1.8 to 6 in formic acid/sulfuric acid.
3. The composition of claim 1, wherein the polyamide is present in an amount of about 35 to about 95 percent by weight based on the total Weight of the composition.
4. The compound of claim 1, wherein the flame retardant system comprises halogenated alone or halogenated in combination with a metal oxide or a phosphinate or a nitrogen compound or any other halogen-free compounds.
5. The compound of claim 1, wherein the crosslinking agent comprises two or more unsaturated groups.
6. The compound of claim 1, wherein the crosslinking agent is a polyallylic compound or a polyol or a poly(meth)acrylate prepared from an aliphatic diol, triol, or tetraol containing 2-100 carbon atoms.

7. The compound of claim 1, further comprising up to about 60 percent by weight of filler.
8. The compound of claim 7, wherein the filler is glass fiber.
9. The compound of claim 1, wherein the compound is crosslinked with ionizing radiation to form a crosslinked compound.
10. The compound of claim 9, wherein the compound after crosslinking exhibits at least one of the following:

i) a rating of V0 according to UL-94 within the range of 0.8 to 3.2 millimeters thickness;
ii) a Glow Wire Flammability Index as measured according to lEC-60695-2-1 of 960°C or greater within the range of 0.8 to 3.2 millimeters thickness;
iii) a Glow Wire Ignition Temperature as measured according to lEC-60695-2-13 of 750°C. or greater within the range of 0.8 to 3.2 millimeters thickness;
iv) a comparative tracking index measured according to
lntemational Electrotechnical Commission standard
lEC-60112 of PLC 1 or PLC 0.
11. A flame retardant compound, comprising: a polyamide; 1 to about 20 percent by weight of a polyallylic compound or a polyol poly(meth)acrylate crosslinking agent; about 5 to about 60 percent by weight of glass fiber; and about 5 to about 25 percent by weight of a flame retardant system.

12. The compound of claim 11, wherein the polyamide comprises about 15 to about 50 percent by weight nylon-6; 1 to about 5 percent by weight of a crosslinking agent selected from the group consisting of triallylisocyanurate, triallylcyanurate, ethyleneglycol di(meth)acrylate and trimethylolpropane tri(meth)acrylate; about 15 to about 30 percent by weight of glass fiber; and about 10 to about 20 percent by weight of the flame retardant system; wherein all the amounts are based upon the total weight of the compound.
13. A method of forming a crosslinkable, flame retardant compound comprising: melt mixing of a polyamide, a crosslinking agent, wherein the crosslinking agent comprises two or more groups capable of forming free radicals under beta or gamma radiation; and a flame retardant system.
14. The method of claim 13, further comprising molding the intimate compound into an article and crosslinking the compound with ionizing radiation.
Digitally signed
Senthil Kumar B
Agent for the applicant
IN/PA-1549 , Description:
FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

Complete Specification
(See section 10 and rule 13)

1.Title of the Invention :

High Energy Radiated X- Polyamide Flame Retardant Compounds

2. Applicant Name : Formulated Polymers Limited

Nationality : Indian

Address : No.57-60, SIDCO Industrial Estate,
Thirumazhisai, Chennai 600 124, India

3. Preamble to the Description :

The following specification particularly describes the invention and the manner in which it is performed.

DESCRIPTION
Field of the invention
The present invention relates to the field of Chemistry. More particularly, the invention relates to Gamma irradiation of Polyamides for producing thin-walled mouldings for electrical and electronics industry.
Background of the invention
Cross-linked polyamide materials can be used as a cost effective replacement for thermosetting materials or high performance polymers. The compound can be used for articles and parts for electronics and electrical applications where the material should not melt during the application and thermoset cannot be used due to its inherent brittleness and where the thin-walled parts are required and which are not met by regular flame retardant polyamide compositions. Typical applications include contact holders in electrical contractors and switches. These applications often require the composition to possess properties such as high temperature stability under lower load, good flame retardant properties, good mechanical properties, and good electrical properties.
Objectives of the invention
The objective of the present invention is to provide a system and method of producing a thermoplastic compound and which can be then cross-linked by gamma irradiation.
Yet another object of the invention is to provide a suitable molecule, which can be mixed and compounded with polyamides and wherein this molecule does not react under heat and pressure, but opens up to reaction only when exposed to gamma radiation.
Detailed description of the invention
The cross-linkable flame retardant polyamide compound contains a polyamide resin characterized by the presence of an amide group (-CO-NH-) in both aromatic and aliphatic Polyamide resins including, Polyamide 6 a polymerization product of caprolactam; polyamide 66, a condensation product of adipic acid and 1,6 -diaminohexane, polyamide 46 a condensation product of adipic acid and 1,4-diaminobutane. Moreover adipic acid, other useful diacids for the preparation of polyamides include azelaic acid, sebacic acid, dodecane diacid, as well as terephthalic and isophthalicacids, and the like. Other useful diamines include m-xylyenediamine, di-(4-aminophenyl) methane, di-(4 aminocyclohexyl) methane; 2, 2-di-(4-aminophenyl) propane, 2, 2-di-(4 aminocyclohexyl) propane, among others. Copolymers of caprolactam with diacids and diamines are also included and other polyamides, such as polyamide 12, polyamide 11, polyamide 6 10, polyamide 6 9, polyamide 6 12, and other tough and super tough polyamides prepared by blending of toughening agent may also be included.
The amount of polyamide present in the crosslinkable polyamide flame retardant compound varies from 35 to 95 percent by weight, more particularly from 45 to 75 percent by weight and even more particularly from 60 to 70 percent by weight based on the total weight percent of the compound.
Crosslinkable flame retardant polyamide compound containing, a brominated or a halogen-free flame retardant based on a phosphinate metal salt and/or a diphosphinate metal salt, optionally in combination with a nitrogen compound show excellent radiation crosslinking in the presence of a crosslinking agent to provide crosslinked polymer compositions. The crosslinked polyamides exhibit excellent flame retardant, physical, and electrical properties suitable for a Wide range of applications. Exemplary uses for the crosslinked compositions include forming durable articles, structured products, and electrical and electronics components. One advantage realized by these crosslinked compounds is their ability to withstand short term, high thermal loading while maintaining excellent flame retardant and mechanical properties. The crosslinkable polyamide compound can be crosslinked by an ionizing radiation such as beta or gamma radiation.
The amount of flame retardant system present in the compound varies from 5 to 25 percent by weight, more particularly 10 to 20 percent by weight, even more particularly 15 to 18 percent by weight based on the total weight percent of the compound.
The crosslinkable polyamide flame retardant compound contains a crosslinking agent which is capable of forming the crosslinking network in the polyamide under beta or gamma irradiation. A Crosslinking agent can contain two or more unsaturated groups including olefin groups. Suitable unsaturated groups include acryloyl, methacryloyl, vinyl, allyl, and the like. Typical polyallylic compounds useful as crosslinking agents include those compounds comprising two or more allylic groups, for example, triallylisocyanurate (TAIC), triallylcyanurate (TAC), and the like, and its combinations. The crosslinking agents can include polyol poly(meth)acrylates, which are typically prepared from aliphatic diols, triols and/ or tetraols containing 2-100 carbon atoms.
Examples of suitable polyol poly(meth)acrylates include ethyleneglycol diacrylate, 1,6-hexanediol diacrylate,neopentylglycol di(meth)acrylate, ethyleneglycol dimethacrylate (EDMA), polyethyleneglycol di(meth)acrylates, polypropyleneglycol di(meth)acrylates, polybutyle neglycol di(meth)acrylates, 2,2-bis(4-(meth)acryloxyethoxyphenyl) propane, 2,2-bis(4-(meth)acryloxydiethoxyphenyl)propane, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate (TMPTA), di(trimethylolpropane) tetra(meth)acrylate, and the like, and combinations thereof. Also included are N,N'-alkylenebi sacrylamides.
The amount of crosslinking agent present in the crosslinkable polyamide flame retardant compound varies from 0.01 to 15 percent by weight, more particularly from 1 to 10 percent by weight, even more particularly from 2 to 8 percent by weight based on the total weight of the compound.
The composition may additionally contain filler, including fibrous filler and/or low aspect ratio filler. Suitable fibrous filler may be any conventional filler used in polymeric resins and having an aspect ratio greater than 1. Such fillers may exist in the form of whiskers, needles, rods, tubes, strands, elongated platelets, lamellar platelets, ellipsoids, micro fibers, nanofibers and nanotubes, elongated fullerenes, and the like, where such fillers exist in aggregate form and an aggregate having an aspect ratio greater than 1 will also be sufficient for the fibrous filler.
Suitable fibrous fillers include, glass fibers, such as E, A, C, ECR, R, S, D, and NE glasses and quartz, and the like may be used as the reinforcing filler. Other suitable glass fibers include milled glass fiber, chopped glass fiber, and long glass fiber. Other suitable inorganic fibrous fillers include those derived from blends comprising at least one of aluminum silicates, aluminum oxides, magnesium oxides, and calcium sulfate hemihydrate. Also included among fibrous fillers are single crystal fibers or “Whiskers” including silicon carbide, alumina, boron carbide, iron, nickel, or copper. Other suitable inorganic fibrous fillers include carbon fibers, stainless steel fibers, metal coated fibers, and the like.
The total amount of filler, fibrous, present in the composition may be about 0 to about 70 percent by weight, more particularly about 5 to about 60 percent by weight, or even more particularly about 15 to about 35 percent by weight based on the total weight of the compound.
Other customary additives may be added to the resin compound at the time of mixing of the resin in amounts as necessary which do not have any deleterious effect on physical properties, specifically the flame retardant properties. For example, coloring agents, heat-resistant agents, oxidation inhibitors, weather-proofing agents, lubricants, mold release agents, plasticizer, and fluidity enhancing agents, and the like, may be added.
When used, the coloring agent may be present in an amount of up to about 5 percent by weight based on the total weight of the compound, more particularly about 0.001 to about 2 percent by weight, and even more particularly about 0.01 to about 1 percent by weight.
The preparation of the compositions may be achieved by blending the ingredients under conditions for the formation of an intimate blend. Such conditions often include mixing in single or twin-screw type extruders or similar mixing devices which can apply a shear to the components.
All of the ingredients may be added initially to the processing system, or else certain additives may be pre-compounded with one or more of the primary components. The other ingredients may include some of the polymer used to prepare the composition, while the remaining portion of the polymer is fed through a port downstream. While separate extruders may be used in the processing, these compositions can also be prepared by using a single extruder having multiple feed ports along its length to accommodate the addition of the various components. It is often advantageous to apply a vacuum to the melt through at least one or more vent ports in the extruder to remove volatile impurities in the composition. Those of ordinary skill in the art Will be able to adjust blending times and temperatures, as well as component addition, without undue additional experimentation.
In one study, a method of forming a crosslinkable, flame retardant compound comprises blending polyamide or polyether, a crosslinking agent, and a flame retardant system to form and intimate blend wherein the flame retardant system comprises a metal phosphinate salt, a metal diphosphinate salt, or combination thereof; and optionally at least one nitrogen compound. The method can further comprise a molding step to mold the intimate blend into an article. Additionally, the molded article can be crosslinked.

In another study, the compounds are used to prepare molded articles such as for example, durable articles, structural products, and electrical and electronic components, and the like. The compound may be converted to articles using common thermoplastic processes such as film and sheet extrusion, injection molding, gas-assisted injection molding, extrusion molding, compression molding and blow molding. Film and sheet extrusion processes may include and are not limited to melt casting, blown film extrusion, and calendaring. Co-extrusion and lamination processes may be employed to form composite multi-layer films or sheets. Single or multiple layers of coatings may further be applied to the single or multi-layer substrates to impart additional properties such as scratch resistance, ultra violet light resistance, aesthetic appeal, and the like. Coatings may be applied through standard application techniques such as rolling, spraying, dipping, brushing, or flow-coating.

Also provided herein is a method of crosslinking the crosslinkable compound. Specifically, the compound is formed or molded into an article and the article is exposed to an appropriate condition(s) to provide crosslinking. In one embodiment, the composition is crosslinked by ionizing radiation. Typical ionizing radiations include beta radiation (high energy electron beam) and gamma radiation (photon emitted by a radioactive source, eg Cobalt 60 or Cesium137) at any dose sufficient to effect crosslinking. The polyamide compositions can be crosslinked at irradiation doses of about 66 to about 99 kilo gray (kGy).

In one study, the crosslinked compositions prepared into 0.8 to 3.2 millimeters (mm) thick test specimens, exhibit a flammability class rating according to UL-94 of at least V2, more specifically at least V1, and yet more specifically at least V0.

In another study, the crosslinked composition exhibits a comparative tracking index (CTI) measured according to International Electro technical Commission (IEC) standard IEC-60l 12/3” using a test specimen having a thickness of 4.0 mm of greater than about 400 Volts, specifically greater than about 500 Volts, more specifically greater than about 600 Volts, A tracking index of 400 to 599 Volts corresponds to class 1, and 600 Volts and greater is class 0.
In yet another study, the crosslinked compositions have a Glow Wire Flammability Index (GWFI) as measured according to IEC-60695-2-l of 960°C at a test specimen thickness within the range of 0.8 to 3.2 millimeters thickness.
In yet another study, the crosslinked compositions have a Glow Wire Ignition Temperature (GWIT) as measured according to IEC-60695-2-l3 of 750° C or greater at a test specimen thickness within the range of 0.8 to 3.2 millimeters, more specifically greater than about 800°C.
It should be clear that compound and articles made from the compound made by the method of this disclosure are within the scope of the invention.

Component Description
Polymer Polyamide 6 2.4 RV
Cross-linking agent Trially isocyanurate (TAIC)
Glass Fiber 249H
Flame Retardant1 BDS
Flame Retardant2` Phospinates/Nitrogen compound
Antioxidant Hindered phenol
Mold Release Glycerol mono Stearates

Description of Drawings
Fig 1 : Analysis of customer requirements
Fig 2 : Selection of polymer
Fig 3 : Selection of radiation source
Fig 4 : Electromagnetic radiation and its wavelength
Fig 5 : Degree of cross-linking vs radiation dosage
Fig 6 : Process overview

Digitally signed
Senthil Kumar B
Agent for the applicant
IN/PA-1549