WO2005101976A2

WO2005101976A2 - Fire retarded polyolefin compositions

Info

Publication number: WO2005101976A2
Application number: PCT/IL2005/000430
Authority: WO
Inventors: Grigory I. Titelman; Samuel Bron
Original assignee: Bromine Compounds Ltd.
Priority date: 2004-04-22
Filing date: 2005-04-21
Publication date: 2005-11-03
Also published as: IL161593A0; WO2005101976A3

Abstract

A fire-retarded polymer composition, where the polymer is selected from the group comprising polyolefin polymers and copolymers, comprises heat expandable graphite (HEG) and at least one nitrogen-containing fire-retardant (N-FR), optionally comprising metal hydroxide additives.

Description

Fire Retarded Polyolefin Compositions

Field of the Invention

The present invention relates to a composition consisting of fire-retarded

polyolefin polymers and copolymers, having excellent fire retardancy, no

corrosive gas and significantly reduced smoke emission on burning and

essentially no migration of the fire-retardant on the surface of the

polymer. In particular, the present invention relates to a halogen-free,

antimony-free and phosphorous-free, nitrogen-containing fire-retarded

composition comprising polyolefin polymers and copolymers. Polyolefin

polymers and copolymers include, inter alia, low density polyethylene

[LDPE], high density polyethylene [HDPE], linear low density

polyethylene [LLDPE], ethylene vinyl acetate copolymer [EVA], homo-

polypropylene [PP], block copolymer of propylene and ethylene, random

copolymer of propylene and ethylene.

Background of the Invention

It is desirable that polyolefin polymers and copolymers be flame-retarded

to prevent fire accident or fire spreading when used in various

applications, such as enclosures and internal small parts of electric,

electronic and office automation apparatus, sewage pipes and pipe fittings,

automotive, wire and cable industry, building materials, etc. Many

polyolefin polymer and copolymer materials for such uses are even required to be fire-retarded by legislation. Known fire-retardant additives,

used in polyolefin polymer and copolymer materials include halogen-

containing fire-retardants, phosphorous- or phosphorous/nitrogen-

containing compounds and metal hydroxides. These additives, however,

have disadvantages.

The halogen-containing fire-retardants, which impart a higher level of fire

retardancy (for example, UL-94 N-0, V-1 or V-2) at relatively small

loadings, generate a large amount of soot or smoke upon burning.

Usually, polymer materials comprising halogen-containing fire-retardants

require synergistic additives such as antimony oxide, which is a toxic

material. Furthermore, the halogen-containing fire-retardants may emit

more or less acidic substances and antimony derivatives at the time of fire,

which may produce adverse effects on human health or apparatus in the

vicinity of a fire site.

Phosphorous- or phosphorous/nitrogen-containing fire-retardants, such as

red phosphorous, ammonium polyp hosphate [APP], melamine phosphate

[MP] or pyrophosphate [MPP] are effective in rather high amounts, and

only in combinations with other additives such as carbonization agents,

blowing agents, etc. Furthermore, these fire-retardants generate soot or

smoke on burning and emit acidic substances at the time of fire, which

produce adverse effects on human health or apparatus in the vicinity of a fire site. Additionally, the phosphorous-based fire-retardants are known for their tendency to migrate to the polymer surface during the service life

of the product containing them.

Metal hydroxide containing fire-retardants, such as aluminum tri-hydrate [ATH] or magnesium hydroxide [MH], used for halogen-free, antimony-free

and phosphorous-free fire-retarded polyolefin polymer and copolymer

compositions, are effective but in very high amounts. Furthermore, metal

hydroxide fire-retardants have adverse effects on the properties of the fire- retarded polymer composition.

Consequently, there is a demand for halogen-free, antimony-free and phosphorous-free fire-retarded polyolefin polymer and copolymer

compositions, possessing highly effective fire retardancy, emit less or no

smoke and less or no corrosive gas, all these while using a smaller amount

of fire-retardant additive. A promising way to satisfy these requirements

is the use of a nitrogen-containing fire-retardant. Consequently,

techniques have been developed and disclosed in which both heat

expandable graphite (HEG) and nitrogen type fire-retardant are used in

combination with carbonization agents and phosphorous-containing fire-

retardant to yield flame retardancy in PE and PP. Patents of Sumitomo Bakelite Co. (Japan) disclose both fire-retarded

polyolefin polymer compositions (JP 1997,059439, JP 1997,137008, JP

1997,111059, JP 1997,316257) and styrene polymer compositions (JP

1997,208768, JP 1997,151378). These fire-retarded polymer compositions contain phenol or cresol novolak resin as carbonization agent, a

phosphorous-containing fire-retardant (red phosphorous, APP, MP) as

acidic catalyst for the carbonization agent, HEG, and optionally, melamine

cyanurate as nitrogen-containing fire-retardant.

A patent of Nippon Kasei Chemicals (JP 03041164) discloses fire-retarded

polyethylene [PE] compositions containing metal hydroxide, oxide and/or

carbonate as fire-retardant and HEG. A paper of Z. Li and B. Qu

published in Polymer Degradation and Stability 81 (2003), pp 401-408,

describes fire-retarded ethylene vinyl acetate [EVA] compositions. These

fire-retarded polymer compositions contain magnesium hydroxide [MH] as

fire-retardant and HEG. A patent application of Bayer Polymers LLC, US

2003/0125447 Al, discloses fire-retarded EVA compositions containing

HEG and a mineral filler (metal oxides, hydroxides and/or carbonate),

which optionally may contain additives including phosphorous- or

halogen-containing fire retardants.

The present invention provides a highly effective fire-retardant polyolefin

polymer and copolymer which emit no corrosive gases and less smoke on burning compared to halogen-containing flame -retardants and/or

phosphorous-based flame-retardants. The fire retardancy of said olefin-

containing polymer and copolymer is based solely on the presence and

activity of HEG and nitrogen-containing fire-retardant (N-FR). Optionally, a highly effective fire-retardant polyolefin polymer and copolymer

composition which emit no corrosive gases and less smoke on burning may

be achieved when nitrogen-containing FR and metal hydroxide are present

in a fire-retarded polymer composition but in amounts significantly lower

that those either conventionally used or known in the state of the art.

It is the object of the present invention to provide a fire-retarded polyolefin

polymer and copolymer, which possesses excellent fire retardancy

properties (emits less corrosive gas and less smoke on burning) applying

halogen-free, antimony-free and phosphorous-free fire-retarded

additive (s).

It is a further object of the present invention to provide a fire-retarded

polyolefin polymer and copolymer, which possesses excellent fire

retardancy properties, applying a nitrogen-containing fire-retarded

additive (s). It is still a further object of present invention to provide a fire-retarded

polyolefin polymer and copolymer, which possesses excellent fire

retardancy properties, applying HEG and N-FR as additives.

It is yet a further object of present invention to provide a fire-retarded

polyolefin polymer and copolymer, which possesses excellent fire

retardancy properties, applying HEG and N-FR and, optionally, metal

hydroxide, as additives.

It is yet a further object of present invention to provide a fire-retarded

olefin-containing polymer composition, wherein the olefin-containing

polymer is selected from the group consisting of polyolefin polymers and

copolymers.

Other purposes and advantages of the present invention will appear as the

description proceeds.

Summary of Invention

The present invention provides a fire-retarded polymer composition

comprising heat expandable graphite (HEG) and at least one nitrogen-

containing fire-retardant (N-FR), and optionally, metal hydroxide, as

additives, wherein the polymer component of said composition is

selected from the group consisting of polyolefin polymer(s) and

copolymer (s). Description of the Invention

The applicant has surprisingly found that a combination of heat

expandable graphite (HEG) and nitrogen-containing fire-retardant(s)

imparts highly effective fire retardancy to a composition of polyolefin

polymer(s) and copolymer(s).

More particularly, a high level of fire retardancy of polyolefin polymer and

copolymer is accomplished when using a fire-retardant combination

consisting of nitrogen-containing fire-retardant(s) (referred to herein as N-

FR) and HEG. Optionally, N-FR and metal hydroxide may be present in a

fire-retarded polymer composition but in amounts significantly lower that

those either conventionally used or known in the state of the art. No

additional, conventionally used FRs, such as carbonization agent and

phosphorous or phosphorous/nitrogen containing compounds, are

incorporated into the polyolefin polymer(s) and copolymer(s).

The invention, therefore, provides a fire-retarded composition comprising:

(a) One or more polymers selected from the group consisting of polyolefin polymer, copolymer and/or alloy thereof;

(b) Heat expandable graphite (HEG);

(c) Nitrogen-containing fire-retardant(s)(N-FR); and optionally

(d) Metal hydroxide. The N-FR may be a single component or a mixture of components of the

same category. The heat expandable graphite should preferably be able to

change its specific volume by expanding 50 times or more on shock heating

from room temperature to 700°C. Metal hydroxide may be a single component or a mixture of components of the same category.

The invention therefore provides a fire-retarded olefin polymer(s) and co¬

polymers) composition comprising:

Component A: a polyolefin polymer and copolymer, preferably LDPE,

HDPE, LLDPE, EVA, PP, random and block co-PP, at a percent weight

which balances to 100% by weight the following fire-retarded combination;

Component B: 6 to 19% (preferably 8% to 10%) by weight of heat

expandable graphite;

Component C: up to 30% (preferably 15% to 25%) by weight of nitrogen-

containing fire-retardant, preferably melamine, cyanuric acid or melamine

cyanurate, and optionally;

Component D: up to 25% (preferably 10% to 20%) by weight of metal

hydroxide, preferably aluminum tri-hydrate or magnesium hydroxide.

The component A may consist of a single polyolefin polymer or a copolymer

or being a mixture of polyolefin polymer(s) and/or copolymer(s). The olefin-containing polymers and copolymers used in the present invention are produced from a olefin-type monomer or co-monomers,

including ethylene, propylene, butadiene, hexadiene and octadiene, linear

or branched, and where the double bonds may be conjugated or not

conjugated and in different positions on the unit monomer chain. The

olefin-containing polymers and copolymers include, inter alia,

homopolymers of ethylene (hereinafter referred to as "LDPE", "HDPE",

"LLDPE"] or propylene (hereinafter referred to as "PP"), rubber modified

high-impact polypropylene (block co-polymer of propylene and ethylene or

ethylene-propylene rubber hereinafter referred to as "block co-PP"),

random propylene and ethylene copolymers (hereinafter referred to as

"random co-PP"), ethylene vinyl acetate copolymers (hereinafter referred

to as "EVA").

The component B of the fire-retarded olefin polymer and copolymer

composition of the present invention is heat expandable graphite which is

well-known in the art, and it is further described by Titelman, G.I.,

Gelman, V.N., Isaev, Yu.V and Novikov, Yu.N., in Material Science

Forum, Vols. 91-93, 213-218, (1992) and in US Patent 6,017,987.

The HEG decomposes thermally under fire into a char of expanded

graphite, providing a thermally insulating or otherwise protective barrier,

which resists further oxidation. The heat expandable graphite is derived from natural graphite or artificial

graphite, and upon rapid heating from room temperature to high

temperature it expands in the c-axis direction of the crystal (by a process so-called exfoliation or expansion). In addition to expanding in the c-axis

direction of the crystal, the heat expandable graphite expands a little in

the a-axis and the b-axis directions as well. The exfoliation degree, or the

expandability of HEG depends on the rate of removing the volatile

compounds during rapid heating. The expandability value in the present

invention relates to the ratio of the specific volume obtained following

rapid heating to a temperature of 500-700°C, to the specific volume at

room temperature. A specific volume change of HEG in the present

invention is preferably not less than 50 times for that range of

temperature change (room temperature to 500-700°C). Such an

expandability is preferred because a HEG having a specific volume

increase by at least 50 times during rapid heating from room temperature

to 700°C, has been found to produce a much higher degree of fire

retardancy compared to a graphite that is heat expandable but has a

specific volume increase of less than 50 times in the aforesaid heating

conditions.

During rapid heating of HEG from room temperature to 700°C, a weight

loss is usually recorded. 10% to 35% (preferably 15% to 32%) weight loss of

HEG is usually due to volatile compounds removed in the aforesaid heating conditions at the volume expandability of 50 times and more. A HEG grade having a weight loss of less than 10%, during rapid heating,

provides a specific volume increase of less than 50 times. A HEG grade

having a weight loss of more than 35%, during rapid heating, provides less

amount of a char of expanded graphite, and consequently the fire

retardancy of polymer composition may be achieved only at higher loading

of HEG.

The carbon content of heat expandable graphite that exhibits under

aforesaid heating conditions a volume expandability of 50 times or higher,

should be 65% to 87% (preferably 67.5% to 85%) by weight for serving as a

good carbonaceous barrier and for providing a high level of fire retardancy

in combination with N-containing flame-retardants.

The HEG having a carbon content of more than 87%, provides during

rapid heating a specific volume increase of less than 50 times. Decreasing

the carbon content in HEG to less than 65% under the aforesaid heating

conditions, provides less amount of a char of expanded graphite, and

consequently the fire retardancy of the polymer composition may be

achieved only at higher loading of HEG.

During rapid heating of HEG from room temperature to a rather lower

temperature (such as about 500°C) a specific volume change of HEG in the present invention should be more than 50 and less than 100 times. A HEG grade having a too-high specific volume increase at a rather lower

temperature (such as about 500°C) provides too fast expansion of HEG

under burning and consequently the fire retardancy of polymer composition may be achieved only at higher loading of HEG.

The heat expandable graphite used in the present invention can be produced

in different processes and the choice of the process is not critical. It can be

obtained, for example, by an oxidation treatment of natural graphite or

artificial graphite. The oxidation is conducted, for example, by treatment

with an oxidizing agent such as hydrogen peroxide, nitric acid or another

oxidizing agent in sulfuric acid. Common conventional methods are

described in US Patent 3,404,061, or in SU Patents 1,657,473 and 1,657,474.

Also, the graphite can be anodically oxidized in an aqueous acidic or

aqueous salt electrolyte as described in US Patent 4,350,576. In practice,

most commercial grades of the heat expandable graphite are usually

manufactured via an acidic technology.

The heat expandable graphite, which is produced by oxidation in sulfuric

acid or a similar process as described above, can be slightly acidic

depending on the process conditions. When the heat expandable graphite

is acidic, a corrosion of the apparatus for production of the polymeric

composition may occur. For preventing such corrosion heat expandable graphite should be neutralized with a basic material (alkaline substance,

ammonium hydroxide, etc.).

The particle size of the heat expandable graphite used in the present invention affects the expandability degree of the HEG and, in turn, the

fire retardancy of the resulting polymer composition.

The heat expandable graphite of a preferred particle size distribution

contains up to 25%, more preferably from 1% to 25%, by weight particles

passing through a 75-mesh sieve. The HEG containing more than 25% by

weight particles passing through a 75-mesh sieve, will not provide the

required increase in specific volume and consequently, will not provide the

sufficient fire retardancy. The heat expandable graphite containing the

above particles at a content which is lower than 1% by weight may slightly

impair the mechanical properties of the resulting polymer composition.

The dimensions of the largest particles of HEG, beyond 75-mesh, should

be as known in the art in order to avoid the deterioration of the properties

of the polymer composition. In a preferred embodiment, the surface of the

heat expandable graphite particles may be surface-treated with a coupling

agent such as a silane -coupling agent, or a titanate-coupling agent in

order to prevent the adverse effects of larger particles on the properties of

the fire-retarded polymer composition. A coupling agent can be separately

added to the composition as well. Component C in the present invention may be either any commonly used

nitrogen-containing fire-retardant or a triazine-based FR compound. A

suitable nitrogen-containing fire-retardant may be, for example:

(a) Melamine {l,3,5-triazine-2,4,6-triamine, C₃H₆N₆ [108-78-1]} and related triazine-based compounds such as, for example, melam {(N- 4,6-diamino-l,3,5-triazine-2-yl)-l,3,5-triazine-2,4,6-triamine, CβHgNn [3576-88-3]}, melem {2,5,8-triamino-l,3,4,6,7,9,9b- heptaazaphenalene, CβHβNio [1502-47-2]}, benzoguanamine {2,4- diamino-6-phenyl-l,3,5-triazine, C9H9N5 [91-76-9]} and acetoguanamine {2,4-diamino-6-methyl-l,3,5-triazine, C₄H Ns [542- 02-9]}.

(b) Cyanuric acid {l,3,5-triazine-2,4,6-triol, C3H3N3O3 [108-80-5]} and related triazine-based compounds such as, for example, ammeline {l,3,5-triazine-2,4-diamine-6-ol, C3H5N5O [645-92-1]}, ammelide {l,3,5-triazine-2-amine-4,6-diol, C₃H N O₂ [645-93-2]}, melamine cyanurate {cyanuric acid, compound with melamine [37640-57-6]}.

(c) In addition to (tri) substituted isocyanurates or cyanurates other nitrogen-containing compounds may serve as component C, such as , for example: non-cyclic precursors of cyanuric acid biuret {NH₂- C(=O)NH-C(=O)-NH₂, [108-19-1]} or triuret {NH₂-C(=O)-NH-C(=O)- NH-C(=O)-NH₂, [556-99-0]}; guanidine -based compounds such as guanidine carbonate {[NH₂-C(=NH)-NH₂]₂CO₃, [593-85-1]} and guanidine nitrate { NH₂-C(=NH)-NH₂NO₃, [506-93-4]}.

The numbers in square brackets are Chemical Abstracts Registry

Numbers.

According to the present invention said Component C may consist of a

single N-FR material or it may consist of a mixture of two or more

different nitrogen-containing fire-retardants as herein before mentioned

that may be suitable for obtaining the desired properties of the polyolefin

polymer, copolymer and/or alloy thereof. Furthermore, said component C

may be a mixture comprising at least one nitrogen-containing fire-

retardant and halogen-free and phosphorous-free fire- retardants of other

types.

Component D in the present invention may be any commonly used metal

hydroxide fire-retardant. The addition of small amounts of such metal

hydroxides have beneficial effects in reducing smoke, improving specific

mechanical properties (e.g. impact strength) and allowing to reduce the

loading of other FR additives. A suitable metal hydroxide fire-retardant

may be, for example, aluminum tri-hydrate [ATH] and magnesium

hydroxide. According to a preferred embodiment of the present invention said

Component D may consist of a single metal hydroxide or it may consist of

a mixture of two or more different metal hydroxide fire-retardants as

herein before mentioned that may be suitable for obtaining the desired

properties of the polyolefin polymer and copolymer. Furthermore, said

component D may be a mixture comprising at least one metal hydroxide

fire-retardant and halogen-free and phosphorous-free fire-retardants of

other types. In a preferred embodiment, the surface of the metal hydroxide

particles may be surface-treated with a coupling agent such as a silane

coupling agent, or a fatty acid coupling agent in order to prevent/reduce

the adverse effects metal hydroxide may have on the properties of the fire-

retarded polymer composition. A coupling agent can be separately added

to the composition as well.

According to another preferred embodiment of the present invention,

Component B and Component C are used together in the amount from

20% to 40% (preferably 23% to 33%) by weight in a composition containing

one or more polyolefin polymer(s) and/or copolymer(s) (Component A) in an

amount balancing the composition to 100 wt %.

With a total amount of less than 23 wt % of Components B and C together,

the polymer composition exhibits still flame retardancy (a relatively high

LOI value) although it has not been classified any more in UL-94 terms. On the other hand, an increase of the total amount of Components B and

C to more than 40 wt % in the composition does not lead practically to a

further increase in fire retardancy but may deteriorate the properties of

the polymer composition.

According to a preferred embodiment of the present invention, Component

B, Component C and Component D are used together in the amount from

26% to 50% (preferably 30% to 40%) by weight in a composition containing

one or more polyolefin polymer(s) and/or copolymer(s) (Component A) in an

amount balancing the composition to 100 wt %.

With a total amount of Components B, C and D together, of less than 26

wt %, the polymer composition exhibits still flame retardancy (a relatively

high LOI value) although it has not been classified any more in UL-94

terms. On the other hand, an increase of total amount of Components B

and C to more than 50 wt % in composition does not lead practically to a

further increase in fire retardancy but may deteriorate the properties of

the polymer composition.

The polymer composition may contain other types of additives such as

colorants, antioxidants, light stabilizers, light absorbing agents,

processing additives, coupling agents and lubricants, blowing agents, anti-

dripping agents, cross-linking agents, and fillers. The above -de scribed fire retardation technique of the present invention produces a polymer material having excellent fire retardancy, no emission

of corrosive gases and less smoke on burning.

Detailed Description of Preferred Embodiments

The present invention will be further illustrated below more with reference to specific examples which are not intended to limit the

invention in any way.

Non-limitative examples of Components A, B, C and D are set forth below:

Component A:

(Al) PP homo-polymer (Capilene; G86E, Carmel Olefins)

(A2) PP co-polymer (Capilene; SG50, Carmel Olefins)

(A3) LDPE (Ipethine 320, Carmel Olefins)

(A4) EVA (ELVAX 3175 LG, DU PONT)

Component B:

Commercially available grades used in the following examples are:

(Bl) Heat expandable graphite (GREP-EG, Tosoh)

(B2) Heat expandable graphite (GRAFGuard 220-80N, UCAR Carbon)

(B3) Heat expandable graphite synthesized by applicant

(B4) Heat expandable graphite synthesized by applicant The properties of components Bl to B4 are shown in Table 1.

Table 1

Component C:

(CI) Melamine cyanurate (Aldrich catalog #C9,545-51)

(C2) Cyanuric acid (Aldrich catalog #M265-9)

(C3) Melamine (Melapur MC-15, D₉₈<15μm, DSM,)

(C4) Melamine cyanurate (Melapur MC-50, D₉₈<50μm, DSM, )

The nitrogen-containing FR (Component C) can be used either as a

powder, or as a previously melt mixed in polyolefin polymer (master

batching). Component D:

(Dl) Magnesium hydroxide (FR-20, DSBG)

(D2) Aluminum tri-hydrate (SF4-25, Baco)

In order to compare the composition of the present invention with

conventional compositions or compositions known in the art, comparative

examples (Ref.) were prepared and hereinafter provided.

Examples 1-40 and Comparative Examples Ref. 1-5

Either PP or PE or EVA were used as Component A. Various amounts of

(B), (C) and (D) as shown in Tables 2-6, were admixed with the Component

A in a granulated form. Mixing was done in a Brabender mixer of 55 cm³

volume capacity at 50 rotations per minute for a desired time and at a

desired temperature, specific for each polymer (190°C for PP and PE,

165°C for EVA). Specimens of 3.2 mm thickness were prepared by

compression molding in a hot press at 200°C (PP, PE) and at 165°C (EVA),

cooling to room temperature and cutting to standard test specimens.

The flammability was tested by limiting oxygen index (hereinafter

referred to as "LOI") method, according to ASTM D-2863 and by UL-94

test (Underwriters Laboratories) with bottom ignition by a standard

burner flame for two successive 10-second intervals. Five test-pieces of each composition were tested and the burning time, given in each

example, are averages of all five tested pieces.

Table 2 demonstrates in the Comparative examples marked as Refs. 1, 2

and 3, that the fire-retarded polymer compositions show a high fire

retardancy (V-0, V-1 rating and high LOI value for PP and PE; very high

LOI value for EVA) at 60%-62% by weight of magnesium hydroxide

content (Component Dl). In the Comparative Examples marked as Refs. 4

and 5 the single use of Component D at 35%-40% by weight resulted in

very low fire retardancy (NR rating according to the UL-94 burning test

and low LOI value 21.0-21.2 %0₂).

Table 2 Comparative Example

achieved

Additive: antioxidant (0.3%) or antioxidant (0.3%) and lubricant (0.2%)

Tables 3 and 4 summarize the fire-retarded polyolefin based compositions,

with a high level of fire retardancy (V-0 or V-1). A total amount of fire- retardant combination containing Components B and C in a loading range from 20 to 40 wt % is used for polyolefins (Tables 3-4). Examples 1-11 (Table 3) and Examples 12-24 (Table 4) clearly show the effect of fire-

retardant synergism obtained when a combination of Components B and C

is applied. A LOI increase and a burning time decrease are measured for all fire-retarded PP, PE and EVA compositions.

Table 3

ΝR - no rating indicates that no UL-94 rating (V-0, V-1 or V-2) was achieved

Additive: antioxidant (0.3%) and lubricant (0.2%)

Examples 1-11 (Table 3) summarize the fire-retarded PP or PE based

compositions, with a high level of fire retardancy (V-0 or V-1). A total

amount of fire-retardant combination containing Components B and C in a

loading range from 30 to 40 wt % (preferably 33-35 wt %) is used for PP or

PE based fire-retardant compositions. Examples 1, 2, 8 and 10 (Table 3)

demonstrate that a high level of fire retardancy (UL-94 rating V-0 or V-1,

high LOI) can be achieved when the content of Component B in the fire- retarded composition is 8 to 15 wt % while the content of Component C is

loaded at 15 to 30 wt % to balance the total amount of the fire-retardant

combination (Components B + C) in the polymer composition to 30-40 wt %.

Examples 10 and 11 demonstrate that when the content of Components B

and C in the composition is 15 wt %, (and, correspondingly, total amount of

fire-retardants 30 wt %) the LOI value increases to 24.0% - 25.7%, but with

no UL-94 rating. The highest level of fire retardancy is achieved when the

amount of fire-retardant combination (Components B + C) in the polymer

composition is 33-35 wt %, wherein the content of Component B is 8-10 wt

% and the content of Component C is 25 wt %.

Examples 2-4 clearly demonstrate that fire-retardant combinations

containing Components B and C provide a high level of fire retardancy

independently on polymer type (homo-PP, co-PP or PE).

Examples 2 and 5-7 demonstrate that any of the used types of heat

expandable graphite (Component B) may be used successfully to impart

flame retardancy to the tested polymers and copolymers. Example 5 demonstrates that the HEG grade having a too-high specific volume

increase at a rather lower temperature (such as about 500°C) provides too

fast expansion of HEG under burning and consequently results in an

increased value of LOI of the fire-retarded polymer composition to 25.0 %O₂, however with no UL-94 rating as compared to HEG with a specific volume increase of 50-100 times in the aforesaid heating conditions (Examples 2, 6 and 7).

Table 4

achieved

Additive: antioxidant (0.3%)

Examples 12-24 (Table 4) summarize the fire-retarded EVA based

compositions, with a high level of fire retardancy (V-0 or V-1, high LOI). A

total amount of fire-retardant combination containing Components B and

C in a loading range from 20 to 30 wt % (preferably 23-25 wt %) is used for

EVA based fire-retardant compositions. Examples 12, 15 and 21-24 (Table

4) demonstrate that a high level of fire retardancy (UL-94 rating V-0 or V-

1, high LOI) can be achieved when the content of Component B in the fire-

retarded composition is 6 to 19 wt % while the content of Component C is loaded at 1 to 20 wt % to balance the total amount of the fire-retardant combination (Components B + C) in the polymer composition to 20-30 wt

%. Examples 22-24 demonstrate that when a total amount of fire-

retardants is less than 23 wt % and the content of Components B in the

composition is 6 to 10 wt % and Component C is 10 to 15 wt %, the LOI

values increase to 27.0%-27.4%, but with no UL-94 rating. Only at 19 wt % content of Component B in the composition and a total amount of fire-

retardant of 20 wt %, a high level of fire retradancy can be achieved (V-0

rating and high LOI value), but the electrically insulating properties of

EVA may be affected. The highest level of fire retardancy is achieved

when the amount of fire-retardant combination (Components B + C) in the

polymer composition is 23-25 wt %, wherein the content of Component B is

8-10 wt % and the content of Component C is 15 wt %.

Examples 12-14 clearly demonstrate that fire-retardant combination

containing Components B and C provide a high level of fire retardancy to

polymer composition independent of the molecular structure of the used

nitrogen-containing fire-retardant (Component C). Examples 15 and 16

clearly demonstrate that a high level of fire retardancy can be achieved

independent of particles size of the used nitrogen-containing fire-retardant

(Component C). Examples 15 and 17-20 demonstrate that any of the used types of heat expandable graphite (Component B) may be used successfully to impart

flame retardancy to the tested polymers and copolymers. Examples 17 and

18 demonstrate that the HEG grade having a too-high specific volume

increase at a rather lower temperature (such as, about 500°C) provides a

too fast expansion of HEG under burning and consequently it results in

increasing the value of LOI to 27.0 %0₂, but without providing the

required UL-94 rating to the fire-retarded polymer composition as

compared to a HEG with a specific volume increase of 50-100 times in the

aforesaid heating conditions (Examples 15, 19 and 20) and may provide

the required high fire retardancy (both V-0 and LOI 29.0%) of the polymer

composition only at a higher loading of HEG (15 wt %) and a higher total

amount of fire-retardant combination (30 wt %).

Table 5 Examples of compositions containing metal hydroxide and

Additive: antioxidant (0.3%) and lubricant (0.2%) Examples 25-32 (Table 5) summarize the fire-retarded PP or PE based

compositions containing the fire-retardant combination of Components B,

C and D that allows to reduce the content of Component C and of Component D, while providing a high level of fire retardancy of the

polymer material (V-0 or V-1). A total amount of fire-retardant

combination containing Components B, C and D in a loading range from

30 to 50 wt % (preferably 40-45 wt %) is used for PP or PE based fire-

retardant compositions. Examples 25-27 and 29-32 (Table 5) demonstrate that a high level of fire retardancy (UL-94 rating V-0 or V-1, high LOI)

can be achieved when the content of Component B in the fire-retarded

composition is 6 to 10 wt % while the content of Component C is loaded at

12 to 20 wt % and the content of Component D is loaded at 10 to 25 wt %

to balance the total amount of the fire-retardant combination (Components

B + C + D) in the polymer composition to 30-50 wt %. Example 31 and 32

demonstrate that when a total content of fire-retardants of less than 33 wt

% and the composition consists of 8 wt % of Components B, 12 wt % of

Component C and 10 wt % of Component D (Example 31), a high level of

fire retardancy can still be achieved, while remaining at the same total

amount of the fire-retardant combination. When the composition of the

fire-retardants contains Components B at 6 wt %, Component C at 14 wt

% and Component D at 10 wt % (Example 32), the LOI value increases to

24.4 %O2 but without providing the required UL-94 rating. The highest

level of fire retardancy is achieved when the amount of fire-retardant combination (Components B + C + D) in the polymer composition is 40-45

wt %, wherein the content of Component B is 10 wt %, the content of

Component C is 15-20 wt % and' the content of Component D is 10 to 20 wt

%.

Examples 27 and 28 clearly demonstrate that fire-retardant combination

containing Components B, C and D provide a high level of fire retardancy

independent of the molecular structure of metal hydroxide (Component D).

Table 6 Examples of compositions containing metal hydroxide and reduced content of Component C

achieved Additive: antioxidant (0.3%)

Examples 33-40 (Table 6) summarize the fire-retarded EVA based

compositions containing the fire-retardant combination of Components B,

C and D that allows to reduce the content of Component C and of

Component D, while providing a high level of fire retardancy of the polymer material (V-0 or V-1, high LOI). A total amount of fire-retardant

combination containing Components B, C and D in a loading range from

24 to 40 wt % (preferably 30-35 wt %) is used for EVA based fire-retardant

compositions. Examples 33, 36, 37, 39 and 40 (Table 6) demonstrate that a

high level of fire retardancy (UL-94 rating V-0 or V-1, high LOI) can be

achieved when the content of Component B in the fire-retarded

composition is 6 to 10 wt % while Component C is loaded at 8 wt % to 10

wt% and the content of Component D is 10 to 20 wt% to balance the total

amount of the fire-retardant combination (Components B + C + D) in the

polymer composition to 24-40 wt %. Example 40 demonstrates that when

the total amount of fire-retardants is less than 26 wt % and the content of

Components B is 6 wt %, Component C is 8 wt % and Component D is 10

wt %, the LOI value increases to of 27.6%, but without providing the

required UL-94 rating. The highest level of fire retardancy is achieved

when the amount of fire-retardant combination (Components B + C + D) in

the polymer composition is 30-35 wt %, wherein the content of Component

B is 10 wt %, the content of Component C is 10 wt % and the content of

Component D is 10 wt %.

Examples 33-35 clearly demonstrate that fire-retardant combination

containing Components B, C and D provide a high level of fire retardancy

to polymer composition independent of the molecular structure of the used

nitrogen-containing fire-retardant (Component C). Examples 37 and 38 clearly demonstrate that fire-retardant combination containing Components B, C and D provide a high level of fire retardancy

independent of molecular structure of metal hydroxide (Component D).

All the above description and examples have been provided for the purpose

of illustration and are not meant to limit the invention in any way. As will

be apparent to a skilled person, the invention can be carried out in many

variations, using different materials and methods, all without exceeding

the scope of the invention.

Claims

1. A fire-retarded polymer composition comprising heat expandable graphite (HEG) and at least one nitrogen-containing fire-retardant (N-FR).

2. A fire-retarded polymer composition according to claim 1, further comprising metal hydroxide additives.

3. A fire-retarded polymer composition according to claim 2, wherein the metal hydroxide additives selected from aluminum trihydrate, [ATH] and magnesium hydroxide and their mixtures.

4. A fire-retarded polymer composition according to claim 1, wherein the polymer is selected from the group comprising polyolefin polymers and copolymers.

5. A fire-retarded polymer composition according to claim 1, wherein the olefin-containing polymers and copolymers are selected from homopolymers of ethylene [LDPE, HDPE, LLDPE] or propylene [PP], rubber modified high-impact polypropylene block co-polymer of propylene and ethylene or ethylene-propylene rubber [block co- PP], random propylene and ethylene copolymers (random co-PP), ethylene vinyl acetate copolymers (EVA).

6. A fire-retarded polymer composition according to claim 1, wherein the polymer consists of a mixture comprising at least one polyolefin polymer and/or at least one polyolefin copolymer.

7. A fire-retarded polymer composition according to claim 1, wherein the heat expandable graphite is obtainable by any conventional route from a natural graphite or artificial graphite.

8. A fire-retarded polymer composition according to claim 7, wherein the heat expandable graphite is produced by oxidation of a natural graphite or artificial graphite in sulfuric acid or in nitric acid and is optionally neutralized with a basic material.

9. A fire-retarded polymer composition according to claim 7 or 8, wherein the heat expandable graphite has a weight loss of 10-35 wt % upon rapid heating from room temperature to 700°C.

10. A fire-retarded polymer composition according to any one the claims 7 to 9, wherein the heat expandable graphite has carbon content in the range of 65-87 wt %.

11. A fire-retarded polymer composition according to any one of claims 7 to 10, wherein the heat expandable graphite has a specific volume expansion of not less than 50 times upon rapid heating from room temperature to a temperature of 500-700°C.

12. A fire-retarded polymer composition according to any one of claims 7 to 11, wherein the heat expandable graphite has a particle size distribution such that no more than 25% by weight of graphite particles pass through a 75-mesh sieve.

13. A fire-retarded polymer composition according to any one of claims 7 to 12, wherein the heat expandable graphite particles are surface treated with a coupling agent.

14. A fire-retarded polymer composition according to claim 1, wherein the N-FR is a triazine ring-containing compound.

15. A fire-retarded polymer composition according to claim 14, wherein the triazine ring-containing compound is melamine or a melamine derivative.

16. A fire-retarded polymer composition according to claim 15, wherein the melamine derivative is selected from the group consisting of melam {(N-4,6-diamino-l,3,5-triazine-2-yl)-l,3,5-triazine-2,4,6-triamine}; melem {2,5,8-triamino-l,3,4,6,7,9,9b-heptaazaphenalene}; benzoguanamine {2,4-diamino-6-phenyl-l,3,5-triazine} and acetoguanamine {2,4-diamino-6-methyl-l,3,5-triazine}.

17. A fire-retarded polymer composition according to claim 14, wherein the triazine ring-containing compound is cyanuric acid or a cyanuric acid derivative.

18. A fire-retarded polymer composition according to claim 17, wherein the cyanuric acid derivative is selected from the group consisting of ammeline {l,3,5-triazine-2,4-diamine-6-ol}; ammelide {l,3,5-triazine-2- amine-4,6-diol}.

19. A fire-retarded polymer composition according to any one of claims 14, 15 or 17, wherein the melamine and cyanuric acid derivative is melamine cyanurate.

20 A fire-retarded polymer composition according to any one of claims 14 to 19, wherein the nitrogen-containing fire-retardant consists of a single compound or a mixture of compounds.

21. A fire-retarded polymer composition according to claim 2 or 3, wherein the metal hydroxide is a single metal hydroxide or a mixture of two or more different metal hydroxides.

22. A fire -retarded polymer composition according to any one of claims 2, 3 or 21, wherein said metal hydroxide is a mixture comprising at least one metal hydroxide fire-retardant and halogen-free and phosphorous-free fire-retardants of other types.

23. A fire-retarded polymer composition according to any one of claims 2, 3, 21 or 22, wherein the surface of the metal hydroxide particles is surface-treated with a coupling agent, said coupling agent preventing the adverse effects metal hydroxide may have on the properties of the fire-retarded polymer composition.

24. A fire-retarded polymer composition according to claim 23, wherein the coupling agent is selected from a silane-coupling agent, or a fatty acid-type of coupling agent.

25. A fire-retarded polymer composition according to claim 23 or 24, wherein said coupling agent is optionally separately added to the composition during processing.

26. A fire-retarded polymer composition according to claim 1, comprising:

(a) at least one polymer selected from the group consisting of a polyolefin polymer and copolymer at a percent weight which balances to 100% by weight the following fire-retardant combination;

(b) 6 to 19% (preferably 8% to 10% by weight) by weight of heat expandable graphite;

(c) up to 30% (preferably 15% to 25% by weight) by weight of nitrogen- containing fire-retardant (N-FR), and optionally;

(d) up to 25% (preferably 10% to 20% by weight) by weight of metal hydroxide.

27. A fire-retarded polymer according to claim 26, wherein the metal hydroxide is aluminum tri-hydrate or magnesium hydroxide.

28. A fire-retarded polymer composition according to claim 26 or 27, wherein the total amount of HEG and N-FR in said composition is from about 20 to about 40 wt %, preferably 23 to 33 wt %.

29. A fire-retarded polymer composition according to claim 26 or 27, wherein the total amount of HEG and N-FR and metal hydroxide in said composition is from about 25 to about 50 wt %, preferably 30 to 40 wt %.

30. A fire-retarded polymer composition according to claim 1, further comprising additives selected from the group consisting of colorants, antioxidants, light stabilizers, fight absorbing agents, process oils, coupling agents, lubricants, blowing agents, fillers and anti-dripping agents.

31. A fire-retarded polymer composition according to claim 23, comprising at least one coupling agent.

32. A fire-retarded polymer composition according to claim 1, substantially as described and exemplified.