ITRM20070169A1 - POLYOLEPHIN FIBERS WITH ANTI-FIRE PROPERTIES AND RELATED PRODUCTION METHOD. - Google Patents

Description

DESCRIPTION

"Polyolefin fibers with flame retardant properties and related production method"

The present invention relates to polyolefin fibers with flame-retardant properties with very low halogen content and the related production method. More particularly, the invention relates to polyolefin fibers with homogeneous and reproducible flame resistance properties, containing a flame retardant composition uniformly dispersed in the mass of the polymeric fiber, obtained by spinning from melt while a composition of concentrate ( masterbatch) containing the flame-retardant active ingredients appropriately selected and proportioned, together with a portion of base polymer with specific properties.

As is known, in many applications it is necessary to impart flame resistance properties to polymeric products and products, so that the articles made with them can satisfy the safety criteria envisaged in each application sector. The methods for providing the various polymeric products with self-extinguishing properties, or in any case with reduced flammability, consist in including in the material or in the polymeric article special flame retardant additives, some of which have been known and used for this purpose for a very long time.

Apart from inorganic compounds based on magnesium or aluminum, (in particular, the relative hydroxides), which are required in the formulation, in order to carry out the required flame retardant action, very high altitudes, with a significant impact on the physical characteristics -mechanics of the polymer matrix and often incompatible with its processability, the flame retardant agents most widely used in the past as additives for thermoplastic polymers, which have established themselves for their effectiveness, are halogenated organic compounds (containing bromine or chlorine), such as brominated aromatic compounds (polybromodiphenyl oxide, brominated polystyrene, tetradecabromodiphenoxybenzene, and many others) or chlorinated cycloaliphatic compounds. Bismuth or antimony compounds can be associated with these, with synergistic functions, such as carbonate or basic carbonate of bismuth, antimony trioxide, trichloride or tribromide of bismuth or antimony.

The use of flame retardants based on halogenated compounds, despite their recognized effectiveness, entails on the one hand problems of corrosion for the equipment used for the production, and on the other hand the risk of producing toxic fumes upon combustion of the product. product that contains them. The ascertained danger of halogens upon combustion and the known environmental problems connected with the release of halogens into the atmosphere have led to a reduction in the use of these products, and their gradual replacement with other flame retardant agents, although low halogen content possible.

Agents with alternative flame-retardant properties, which are widely used in thermoplastic polymer compositions, are those based on nitrogen compounds, and specifically triazine derivatives. Among these, in particular, the melamine compounds, which are characterized by a molecule in which the three amino groups bonded to the three carbon atoms of the triazine ring are not substituted. The melamines and, more generally, the triazines, being basic, can be salified with one, two or three hydrobromide, hydrochloric, cyanhydric groups, and the like. The use of triazine compounds and, in particular, melamine compounds, halogenated or not, as flame-retardant agents is described, for example, in US patent 4028333 in the name of Lindvay (assignee Velsicol Chemical Corp.), published on 7 June 1977.

Other compounds widely used as flame retardants are phosphorus-based compounds, both organic and inorganic, such as phosphoric, polyphosphoric, pyrophosphoric, phosphorous acid derivatives, phosphoric esters, red phosphorus derivatives, organic phosphinates and the inorganic ones, the phosphine oxides, alone or in association with one or more of the other flame-retardant agents mentioned. In particular, the use of red phosphorus-based compounds in the production of plastics is widely exploited by virtue of its effectiveness and cost-effectiveness, particularly for molded items for electrical installations, and in several other sectors where red (or even black) of the resulting material is not a limitation.

One of the first examples of flame retardant formulations designed for thermoplastic polymers with the intention of reducing the overall content of halogens is described in US patent 4710528 in the name of Bertelli et al. (assignee Himont Ine.), relating to flame resistant thermoplastic compositions comprising, as flame retardant agents, adequate proportions of a brominated melamine compound (melamine hydrobromide), a compound of antimony or bismuth (for example antimony oxide or oxychloride , metallic bismuth or a salt thereof, oxygenated or not) and, optionally, small amounts of a compound promoting the formation of free radicals, such as 2,3-dimethyl-2,3-diphenylbutane or 2,3-dimethyl-2 , 3-diphenylhexane.

The polymeric compositions for which the problem of providing a treatment that confers reduced flammability arises include not only plastics that are mass-formed by molding, or by extrusion, for which the flame retardant additive is added in a suitable proportion in the polymeric mixture with which the final article is formed, but also materials with which fibers and yarns are made, to then obtain from these textile articles, upholstery materials, carpets, carpets, non-woven fabrics and felts of various kinds. In this case it is the fiber, both staple and yarn, which must be provided with the necessary flame-retardant properties. This is often done downstream of the spinning process, by providing the fibers with suitable fireproof coatings.

For example, US patent 6617382 in the name of Pirig et al. (assignee Clariant GmbH) describes a low halogen content flame retardant coating for fiber materials, based on the application on the fiber of a vinyl-based film-forming binder, together with polyphosphate melamine as a flame retardant agent.

According to the patent application US 2006/0266986 in the name of Day et al. (transferee Rhodia Ine.), apply flame retardant agents on thermoplastic fibers, in addition to the problem of choosing the agent, which must avoid not only halogens but also red phosphorus, unsuitable for the textile sector both for the color and for the toxicity of the fumes that it can give off in combustion with polyamide materials, also involves the problem of the poor persistence of the agent applied on the fiber, and therefore the poor maintenance over time of the flame resistance properties. In fact, the textile articles made with coated fibers do not maintain the flame resistance properties unaltered if they are subjected to repeated washing, or undergo wear due to rubbing.

In order to reduce these drawbacks, the cited document proposes the application of suitable flame retardant agents, always as a coating, but in an intermediate process phase between spinning and obtaining the finished product, specifically in the "sizing" phase ( ensimaggio or finishing, usually consisting in the application of an antistatic and lubricating agent to the bundle of cooled fibers collected by the spinnerets). The products usable as flame-retardant agents in this case are selected from those already known and most successful as an alternative to halogenated flame-retardant agents.

Despite the existence of solutions such as those just mentioned for the production of fiber, thread and fabrics with reduced flammability starting from suitably coated thermoplastic polymeric materials, it is undeniable that providing the flame retardant agent directly in the mass of the polymer that is subjected to spinning offers durability guarantees of flame resistance properties that are not possible with a surface coating treatment of the fiber. Therefore, at least for certain applications, the provision of additives to be included in bulk in the polymer blend is a necessary choice. An example can be the production of yarns and fibers for carpets, upholstery, carpets and non-woven fabrics to be used, among other things, in the automotive industry, where it is required that the flame resistance properties of the materials remain unchanged. for years, despite the wear to which these articles are subjected.

A solution of the prior art that an attempt was made, in the context of the studies that led to the present invention, to apply to the field of fiber production, is described in the published international patent application. No. WO 2005/019330 of Diap S.r.l., relating to a flame retardant polymeric composition with a low halogen content containing, in addition to the polymeric material that constitutes the product,

♦ a triazine or a mixture of possibly halogenated triazines, ♦ a bismuth compound, possibly also halogenated, ♦ a compound chosen from the group consisting of red phosphorus, a phosphorus compound and an organic compound capable of forming free radicals.

The total of halogens contained in the formulation (which, as shown by the foregoing, may be present in the triazine, in the bismuth compound or in both) is never more than 1% by weight.

According to the description, such a flame-retardant formulation can be applied to a wide variety of thermoplastic polymers, including olefin polymers and copolymers (polyolefins) including, in particular, polypropylene, homopolymer or copolymer.

Another solution for a flame retardant additive with a reduced halogen content, which entails the benefit of lower environmental risks due to the absence of the bismuth compound and, moreover, the undoubted advantage of a considerable flame retardant efficacy even with a total colorability of the products, due to the absence of red phosphorus, is described in the published international patent application. No. WO 2007/010318 to Italmatch Chemicals S.p.A .. This describes flame retardant thermoplastic polymer compositions for molding, which contain:

♦ from 65% to 99.5% by weight of a polyolefin polymer, in particular polypropylene;

♦ from 0.1% to 35% of a synergistic mixture of a metal salt of hypophosphorous acid (H3P02, also known as phosphinic acid) and of a halogenated organic compound;

♦ from 0.5% to 10% by weight of other additives;

and optionally an inorganic filler.

In particular, the aforementioned synergistic mixture preferably contains aluminum or calcium hypophosphite, of formula (PH202) 3AI or (PH202) 2Ca respectively, and a brominated organic compound which can preferably be tetrabromo-bisphenol A-bis ( 2,3-dibromopropylether) or melamine hydrobromide, the two compounds (inorganic salt of phosphorus and brominated organic compound) being in a weight ratio between 6: 1 and 1: 6.

The two solutions mentioned last, although particularly suitable for the flame-retardant treatment of thermoplastic polymeric materials and, specifically, polyolefins, do not allow, applied as such, to obtain the same advantageous flame resistance properties in fiber materials, obtained by spinning . As is known, in melt spinning processes, the thermoplastic polymeric material, suitably with additives, is fed from an extruder, in a predetermined temperature range, to one by a series of spinnerets by means of as many volumetric pumps, and the bundles of filaments that emerge from the dies are collected by roller systems and cooled with cold air jets, solidifying. Depending on the type of process, the number of holes present in each spinneret, the distance between the spinneret and the collection system and the speed of the fibers emerging from the spinneret may vary, but in any case what is produced is a fiber that is then further treated and cut to give the staple, or a continuous thread, which also undergoes a series of specific treatments depending on the intended use and is then collected in reels.

The dosage of the appropriate additives in the polymeric blend, including the flame retardants but also other components, such as colors and pigments, dispersing additives and others, is carried out by first making one or more concentrated mixtures of said additives, which are called masterbatches. (or simply master), in which the additives are mixed together and with a small amount of polymer, and are extruded to form granules of homogenized products. The masterbatch granules are then fed in the appropriate proportions with a dispenser to the extruder head, to be adequately distributed in the mass of the polymer being spun.

By applying the normal procedure described above for the production of polyolefin fibers and setting the goal of making a fiber with reliable flame resistance characteristics, it has been found, in the context of the studies connected with the present invention, that even using flame retardant compositions such as those proposed in the last two documents mentioned, it is not possible to obtain a fiber that gives homogeneous and almost constant results in terms of flame resistance. It was considered, analyzing the production system, that the difficulty of using active ingredients at an industrial level that confer flame-retardant properties to the fibers are mainly due to the following three aspects.

1) The process of spinning from molten polymer requires the use of filters upstream of the die which are particularly severe, with mesh sizes 15-20 μιτι, to avoid clogging of the die holes. The presence of inorganic particles, or organic but with melting points higher than the process temperatures (250-290 ° C) tends to clog the filters, exposing the plant to frequent stops for filter replacement and therefore to significant production losses. 2) The polymer system plus additives cannot guarantee the uniformity and regularity of the spinning if it is not extremely homogeneous, and this leads to breakages of the fiber emerging from the supply chain and further production problems.

3) The fibers, which have diameters of the order of a few microns or tens of microns, have a high surface / volume ratio, so that an imperfect and non-uniform distribution of the active principles inevitably leads to results, in terms of resistance to flame, extremely variable and inhomogeneous, with fiber sections with good flame resistance and fiber sections with very poor resistance. In terms of product quality for safety purposes, these results qualify the product as unreliable, and therefore unacceptable.

In light of the foregoing, it has been found, according to the present invention, that the three critical points reported above can be overcome by starting from the best flame retardant formulation tested so far, represented by the additive composition described in the patent application WO 2007/010318, and providing by one part to reduce the particle size of the active ingredients used, with an upper limit of 10-15 μιτι, and on the other to replace a portion (preferably around 25-50%) of the polymer used in the masterbatch with a polymer of similar chemical nature but with a very high Melt Index (preferably higher than 400 dg / min). As is known, the "melt index" (or "M.F.I.", melt flow index, or melt flow rate) represents a melt flow rate of the polymer, and is normally measured according to the ASTM D-1238 standard, as grams of polymer extruded in 10 min. through a standard orifice under a constant load of 2.16 kg at 230 ° C. A polypropylene homopolymer or random copolymer, of the type used for the production of polypropylene fiber for spinning from melt ("long spinning" or "short spinning") has an MFI between 1.5 and 60 g / 10 min., Which corresponds to an intrinsic viscosity of 2.5-0.9 dl / g. The most common quality of polypropylene, with which polyolefin fibers are made which are then used for the production of flame resistant products, such as semi-finished products for the automotive industry, has a Melt Index around 25 dg / min.

On the basis of what is found according to the invention, the same formulation of flame-retardant agents which for the production of polyolefin fibers gives unacceptable results, with fiber sections having the required resistance and practically flammable fiber sections, proves to be adequate and reliable when in the masterbatch an adequate amount of polymer with characteristics different from that which will make up the fiber is included, with a very high fluidity index.

Therefore, the specific object of the present invention is a flame retardant polyolefin fiber with a reduced halogen content containing a flame-retardant masterbatch composition comprising in turn:

a) one or more metal salts of hypophosphorous acid;

b) one or more halogenated triazines;

c) a polyolefin polymer having a Melt Flow Index (MFI) not lower than 100 dg / min;

d) a polyolefin polymer having a Melt Flow Index (MFI) between 2 and 60 dg / min;

the maximum particle size of said one or more metal salts of hypophosphorous acid not exceeding 15 μιτι,

the composition of flame-retardant masterbatches being added to the polymer which constitutes the mass of the polyolefin fiber in such quantity as to result in a fiber containing:

A) from 0.1% to 2% by weight of said one or more metal salts of hypophosphorous acid;

B) from 0.02% to 0.75% by weight of said one or more halogenated triazines;

C) from 0.1% to 3.5% by weight of said polyolefin polymer having MFI of not less than 100 dg / min;

D) from 0.4% to 4.25% by weight of said polyolefin polymer having MFI between 2 and 60 dg / min.

Preferably, the flame-retardant masterbatch composition may further comprise:

e) one or more free radical generating compounds, i.e. compounds capable of promoting the formation of free radicals of the type known in the prior art, such as 2,3-dimethyl-2,3-diphenylhexane and 2,3- dimethyl-2,3-diphenylbutane or bis-cumyl, so that the resulting fiber contains up to 0.25% by weight, and preferably between 0.005% and 0.1% by weight, of said one or more compounds free radical generators.

Again according to some preferred solutions of the invention, the composition of flame-retardant masterbatches also includes:

f) one or more dispersing compounds, which may be one or more of the compounds conventionally used for this purpose, such as for example metal salts of stearic acid (calcium, zinc, zirconium stearate, etc.), paraffin waxes, waxes polyethylene, so that the resulting fiber contains up to 0.25% by weight, and preferably between 0.002% and 0.025% by weight, of said one or more dispersing compounds.

According to the invention, the polyolefin polymer d) present in the flame-retardant masterbatch composition is the same polymer that constitutes the mass of the polyolefin fiber, and is endowed with a fluidity index of ordinary level for a polyolefin for melt spinning ("short spinning" or "long spinning"). Preferably it is polypropylene homopolymer or propylene copolymerized with ethylene, pentene, hexene and / or other α-olefins, but any polyolefin mixture suitable for the spinning process in question can be used.

The base polyolefin polymer can be of the type obtained with the conventional Ziegler-Natta catalysts, or it can be obtained with a metocene (metallocene) catalyst.

As already noted, the best performance of the composition according to the invention in the spinning of polyolefin fibers is obtained when the inorganic compound is ground in such a way as to bring its maximum particle size in the range between 10 and 15 μιτι, preferably less than 10 μιτι.

According to some preferred embodiments of the invention, the weight ratio between said one or more metal salts of hypophosphorous acid and said one or more halogenated triazines is between 1: 6 and 6: 1. Said one or more halogenated triazines preferably consist of melamine hydrobromide, while the one or more metal salts of hypophosphorous acid preferably consist of calcium hypophosphite. In the latter case, the preferred weight ratio between calcium hypophosphite and melamine hydrobromide is 4.5: 1.

Still according to some specific embodiments of the invention, the polyolefin polymer c) present in the flame-retardant masterbatch co-composition has MFI of not less than 400 dg / min, the optimal choice being that in which a share equal to 15-50% by weight of said masterbatch is made up of a polyolefin polymer with MFI between 800 and 1000 dg / min.

In turn, said polyolefin polymer d) present in the flame-retardant masterbatch composition, which is normally the same with which the mass of the fiber is made, preferably has an MFI comprised between 20 and 30 dg / min.

The flame-retardant masterbatch composition is added to the polymer which constitutes the mass of the fiber generally in a proportion of between 2 and 5% by weight, and preferably in a proportion of 3% by weight.

According to a different aspect, the invention also relates to a flame-retardant masterbatch for making flame retardant polyolefin fiber as defined above. This is usually obtained in granules by extrusion, starting from the compositions described above, and can be marketed as such to be used as a suitable flame retardant additive in polyolefin melt spinning.

Another specific object of the invention are also flame-resistant polyolefin fibers, both in staple and yarn, obtainable by spun spinning with the use of a flame-retardant masterbatch such as the one defined above. These fibers can be used for various applications where reliable flame resistance properties are required, such as for example the production of fabrics, rugs or carpets starting from flame retardant yarn, or non-woven fabrics starting from flame retardant staple according to the 'invention.

According to current practice, in the production of staple fiber the flame-retardant master is added with a dispenser at the predetermined percentage to the base polymer. In the case of colored fibers, the color master is added with another dispenser. Everything goes into the extruder where the melting and mixing of the components takes place (base polymer, flame retardant master and, for colored fibers, color master).

The thermal profiles of the extruder are in the range of 190-280 ° C and the temperature of the spinning head (die) is in the range of 200-280 ° C. The polymeric composition is spun passing through the die holes and is collected with special rollers. The spinning speed is in the range 50-150 m / min in the case of a "short spinning" process in one phase, or in the range 500-2500 m / min in the case of a "long spinning" process. The spinning phase is followed by a stretching of the formed fiber, to impart toughness to the fiber, which is carried out by passing the fiber between two series of rollers which rotate at different speeds. The stretching ratio is given by the ratio of the speeds of the two series of rollers.

In the production of the staple, the kerning phase follows, which has the purpose of imparting a wavy shape to the fiber, necessary to allow subsequent processing in carding, for the realization of the finished products (woven-non-woven). After kerning, the fiber is cut to give the flock, with a length of the cut that can vary, depending on the applications, from 40 to 120 mm.

In continuous yarn spinning, the dosing phase of the master (flame retardant and color master) and that of extrusion are as above. The spinning and drawing process takes place in a single phase: the spinning speed is 500-1500 m / min, then the yarn passes over other rollers that rotate at a speed of 1500-4000 m / min and is collected in reels. The yarn thus obtained is continuous and smooth, and can also be used as it is for some applications (belts, handles for bags, belts for backpacks, etc.).

For the production of carpets and rugs, the yarn is voluminized (bulk continuous filament or BCF), passing it into metal chambers (jets) that have a temperature of 140-1 65 ° C with compressed air or steam. This treatment leads to a shrinkage and swelling (bulking) of the yarn, and the resulting product can be used as it is or can undergo further processing for particular applications still in the field of carpets, such as twisting and heat setting.

For the production of fabrics (such as fabrics for chairs, armchairs and upholstery) the smooth yarn is instead treated with texturing processes or taslanization processes, in which it undergoes twists that serve to impart undulations and elasticity.

According to a further aspect, the present invention relates to a process for the production of a flame-retardant polyolefin fiber with a reduced halogen content, in which said fiber is obtained by spinning a polyolefin polymer from melt, by means of an operation of extrusion through a spinneret, at the head of which a composition of flame-retardant masterbatch as defined above is dosed in a proportion between 2% and 5% by weight, and preferably 3%.

The specific characteristics of the invention, as well as the advantages of the same and the relative operating methods, will be more evident with reference to the detailed description presented by way of example below, together with the results of the experiments carried out on it and comparative data with solutions. according to the prior art. The commercial products used in the examples below were the following:

■ calcium hypophosphite and melamine hydrobromide already premixed in a 4.5: 1 ratio and having a maximum particle size not exceeding 15 μιτι, produced by Italmatch Chemicals S.p.A. under the trade name PHOSLITE B630C,

■ 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) manufactured by Akzo Nobel under the trade name PERKADOX 30

■ polypropylene produced by Basell of the following qualities:

MFI 25: Moplen HF 500R from Ziegler-Natta catalyst MFI 800: Moplen HF 568 X from Ziegler-Natta catalyst MFI 1000: Metocene X50128 from metallocene catalyst MFI 35: Moplen HP 561 S from Ziegler-Natta catalyst. The fiber produced is subjected to an evaluation of the flame resistance properties with the measurement of the Low Oxygen Index (LOI) according to the ASTM D2863 standard, in which the material to be tested is burned like the wick of a candle, in a vertical position. The measurement is carried out by placing the material to be evaluated under a glass bell, in which a suitably proportioned mixture of oxygen and nitrogen is made to flow. The top of the sample is lit and the percentage of oxygen with respect to nitrogen is then continuously varied, reducing it to the point that the material is no longer able to feed the flame. The value that is determined as LOI is equivalent to a percentage of oxygen in the nitrogen / oxygen mixture, and is just below the critical value. It is evident from the above that a LOI value of 18 indicates that the sample is flammable, while values of at least 24 indicate good flame resistance.

EXAMPLE 1

Flame retardant polypropylene staple fiber Composition of the master:

calcium hypophosphite 18.40% melamine hydrobromide 4.09% polypropylene MFI 25 dg / min 59.32% polypropylene MFI 1000 dg / min 16.64% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 1 , 30% dispersant zinc stearate 0.25% A masterbatch with the percentage composition and above indicated, for a total of about 150 kg, was mixed in a 600 liter turbomix. The process parameters used for the preparation of the master were the following:

speed of the dispenser: 35 rpm

extruder temperatures (° C): 170 (power supply) - 170 - 180 - 185 -180 - 180 - 190 - 195 (head)

speed: 350-400 rpm

capacity: 85-100 kg / h.

The master thus obtained, in granules, was added in a percentage of 3% by weight with an in-line dispenser to the base polymer, consisting of polypropylene MFI 25.

Spinning conditions:

Thermal profiles in extruder (° C): 210 - 215 - 220 - 225 - 230 - 230 - 230 -230

spinning heads temperature: 230 ° C

quenching air temperature: 16 -18 ° C

die flow rate (g / min hole): 0.041

collection rollers speed: 31 - 33 m / min

ironing rollers speed: 125 m / min

stretching ratio: 4.03

fiber count produced: 3.3 dtex

crimping: 6 waves / cm

cut: 60 mm

Composition% of the components of the master flame retardant (FR) on the fiber:

calcium hypophosphite 0.552%

melamine hydrobromide 0.123%

polypropylene MFI 25 dg / min 1,779%

polypropylene MFI 1000 dg / min 0.499%

2,3-Dimethyl-2,3-diphenylbutane (bis-cumyl) 0.039%

0.008% zinc stearate dispersant 5 tons of staple fiber were thus produced. There were no clogging of the filters, and the spinning was regular.

10 samples per ton were taken from production, for a total of 50 samples, for flame resistance measurements. This was evaluated by determining the Low Oxygen Index (LOI) according to the ASTM D2863 standard, as described above.

Results obtained: 100% constant values, LOI 25-26.

EXAMPLE 2

Flame retardant polypropylene staple fiber Composition of the master:

calcium hypophosphite 19.40% melamine hydrobromide 4.31% polypropylene MFI 25 dg / min 37.37% polypropylene MFI 1000 dg / min 37.37% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 1 , 30% dispersant zinc stearate 0.25% A masterbatch with the percentage composition and above indicated, for a total of about 150 kg, was prepared in granules by extrusion as in Example 1 and was then added, in a percentage of 3% by weight, in the same way as in Example 1, to the base polymer at MFI 25.

The spinning conditions were the same as in Example 1.

Composition% of the components of the master flame retardant (FR) on the fiber

calcium hypophosphite 0.582% melamine hydrobromide 0.129% polypropylene MFI 25 dg / min 1.121% polypropylene MFI 1000 dg / min 1.121% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 0.039% dispersant zinc stearate 0.008% Also in this case 5 tons of staple fiber were produced, from which samples were taken for flame resistance measurements. In the production there were no clogging of the filters, and the spinning was regular.

The flame retardant properties detected on the samples correspond to 100% constant values, with LOI 25-26.

EXAMPLE 3

Flame retardant polypropylene staple fiber, black color

The flame retardant masterbatch was the same as in Example 1, obtained with the same procedure.

The conditions and materials of the spinning phase were the same as in Example 1 with the only difference that a share equal to 2.5% by weight of carbon black master was also added with a dispenser.

The results of the test, both in terms of carrying out the spinning process and in terms of flame resistance properties of the products obtained, were the same as in Example 1 (LOI between 25 and 26 for all specimens).

EXAMPLE 4

Flame retardant polypropylene staple fiber

In this case the part of the high melt index polymer in the masterbatch was made up of polypropylene at MFI 800 dg / min.

Composition of the master:

calcium hypophosphite 19.40%

melamine hydrobromide 4.31%

polypropylene MFI 25 dg / min 56.10%

polypropylene MFI 800 dg / min 18.64%

2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 1.30%

0.25% zinc stearate dispersant

The master, made as in Example 1, was added at 3% to the base polymer at MFI 25, and the spinning conditions were the same as in Example 1.

Composition% of the components of the master flame retardant (FR) on the fiber:

calcium hypophosphite 0.582%

melamine hydrobromide 0.129%

polypropylene MFI 25 dg / min 1.683%

polypropylene MFI 800 dg / min 0.559%

2,3-Dimethyl-2,3-diphenylbutane (bis-cumyl) 0.039%

dispersant zinc stearate 0.008%

The results, both in terms of carrying out the spinning process and in terms of LOI, were the same as in Example 1 (LOI between 25 and 26 for all specimens).

EXAMPLE 5

Polypropylene staple fiber - Comparison

In the comparison test carried out, the proportions and the choice of components, as well as all the procedures, were the same as in Example 1, except for the fact that there was no high MFI master share.

Composition of the master:

calcium hypophosphite 18.40%

melamine hydrobromide 4.09%

polypropylene MFI 25 dg / min 75.96%

2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 1.30%

0.25% zinc stearate dispersant

The master, prepared under the same conditions as in the previous cases, was added at 3% to the base polymer at MFI 25. The spinning conditions were the same as in the previous cases.

Composition% of the components of the master flame retardant (FR) on the fiber:

calcium hypophosphite 0.552%

melamine hydrobromide 0.123%

polypropylene MFI 25 dg / min 2.279%

2,3-dimethyl-2,3 diphenylbutane (bis-cumyl) 0.039%

dispersant zinc stearate 0.008%

The flame retardant properties of the fiber obtained, in terms of Low Oxygen Index, were the following: LOI on 50 specimens: 12 with LOI 25, 29 with LOI 18 (the fiber burns), 7 with LOI 21, 8 with LOI 19, 9 with LOI 23.

Therefore the results have been variable, and the fiber is not suitable as a flame resistant fiber.

EXAMPLE 6

Continuous flame retardant polypropylene thread

In this case, voluminized continuous yarn was produced, with a master composition equal to that of Example 1, and identical master production methods.

Master composition:

calcium hypophosphite 19.40%

melamine hydrobromide 4.31%

polypropylene MFI 25 dg / min 56.10%

polypropylene MFI 1000 dg / min 18.64%

2,3-dimethyl-2,3 diphenylbutane (bis-cumyl) 1.30%

0.25% zinc stearate dispersant

The master, prepared under the same conditions as the previous cases, was added at 3% to the base polymer at MFI 25, with an in-line dispenser. In this case, a blue color master was also added, also at 3% by weight.

Spinning conditions:

Thermal profiles in etrusor: (° C): 220 - 225 - 230 - 230 - 235 - 235 - 235 -235

spinning heads temperature: 235 ° C

quenching air temperature: 16 -18 ° C

die flow rate (g / min hole): 2.0 g

collection rollers speed: 540 m / min

ironing rollers speed: 1860 m / min

stretching ratio: 3.4

single filament count: 13 dtex

voluminization: jet temperature: 160 ° C - jet air pressure: 7.5 bar Composition% of the components of the master flame retardant (FR) on the fiber:

calcium hypophosphite 0.582% melamine hydrobromide 0.129% polypropylene MFI 25 dg / min 1, 683% polypropylene MFI 1000 dg / min 0.559% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 0.039% dispersant zinc stearate 0.008 % 200 spools of 5 kg each were produced with a continuous yarn spinning process for a total of 1000 kg of voluminized yarn.

50 wire samples from this production were analyzed to determine the LOI according to ASTM D2863.

Results obtained: 100% constant values, LOI 25-26.

EXAMPLE 7

Continuous polypropylene wire - Comparison In the comparison test carried out, the proportions and the choice of components, as well as all the procedures, were the same as in Example 6, except for the fact that there was no high MFI master share.

Composition of the master:

calcium hypophosphite 19.40% melamine hydrobromide 4.31% polypropylene MFI 25 dg / min 74.74% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 1,30% dispersant zinc stearate 0,25 % Composition% of the components of the master flame retardant (FR) on the fiber:

calcium hypophosphite 0.582% melamine hydrobromide 0.129% polypropylene MFI 25 dg / min 2.242% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 0.039% dispersant zinc stearate 0.008% Also in this case were produced, with a continuous yarn spinning process, 200 spools of 5 kg each for a total of 1000 kg of bulked yarn, and 50 yarn samples from this production were analyzed to determine the LOI.

The results obtained have been extremely variable, and the resulting wire is not acceptable as a flame resistance. Results: 6 samples with LOI 26, 15 samples with LOI 18 (the thread burns), 22 samples with LOI 21, 7 samples with LOI 23.

EXAMPLE 8

Flame retardant polypropylene fiber in staple A polypropylene fiber was made in the same manner as in Example 1, but with a lower proportion of flame retardant components. Composition of the master:

calcium hypophosphite 14.89% melamine hydrobromide 3.31% polypropylene MFI 25 dg / min 62.21% polypropylene MFI 1000 dg / min 18.64% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 0 , 70% dispersant zinc stearate 0.25%

The master, prepared as in Example 1, was added at 3% by weight to the base polymer, consisting of polypropylene with MFI 25 dg / min, and everything was spun as in Example 1.

Composition% of the components of the master flame retardant (FR) on the fiber:

calcium hypophosphite 0.447% melamine hydrobromide 0.099% polypropylene MFI 25 dg / min 1, 866% polypropylene MFI 1000 dg / min 0.559% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 0.021% dispersant zinc stearate 0.008 % Of the 5 tons of fiber produced, as in Example 1, 50 samples were taken, in the same way, to determine the LOI according to the ASTM D2863 standard.

Results obtained: 100% constant values, LOI 25.

EXAMPLE 9

Polypropylene staple fiber - Comparison In the comparison test carried out, the proportions and the choice of components, as well as all the procedures, were the same as in Example 8, except for the fact that there was no MFI master share.

Composition of the master:

calcium hypophosphite 14.89% melamine hydrobromide 3.31% polypropylene MFI 25 dg / min 80.85% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 0.70% dispersant zinc stearate 0.25 %

The master, prepared as in Example 8, was added at 3% by weight to the base polymer, consisting of polypropylene with MFI 25 dg / min, and the whole was spun as in Example 8.

Composition% of the components of the master flame retardant (FR) on the fiber:

calcium hypophosphite 0.447% melamine hydrobromide 0.099% polypropylene MFI 25 dg / min 2.425% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 0.021% dispersant zinc stearate 0.008% Also in this case of the 5 tons of fiber produced, 50 samples were taken, in the same way as in the previous examples, to determine the LOI value.

Results: 8 samples with LOI 25, 23 samples with LOI 18 (the fiber burns), 12 samples with LOI 19, 7 samples with LOI 19. Therefore, the results are inconsistent and the fiber is not suitable as flame retardant.

EXAMPLE 10

Polypropylene staple fiber - Comparison

In this case, a master was tested in which there is no high MFI polypropylene and instead of PP at MFI 25 dg / min there is a PP at MFI 35 dg / min.

Composition of the master:

calcium hypophosphite 19.40% melamine hydrobromide 4.31% polypropylene MFI 35 dg / min 74.74% (Basell Moplen HP 561 S ground granule powder)

2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 1.30% dispersant zinc stearate 0.25%

The master, prepared as in Example 1, was added at 3% by weight to the base polymer, consisting of polypropylene with MFI 35 dg / min, and everything was spun as in Example 1.

Composition% of the components of the master flame retardant (FR) on the fiber:

calcium hypophosphite 0.582% melamine hydrobromide 0.129% polypropylene MFI 35 dg / min 2.242% (Basell Moplen HP 561 S ground granule powder)

2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 0.039% dispersant zinc stearate 0.008% Also in this case, of the 5 tons of fiber produced, 50 samples were taken, in the same way as in the previous examples, for determine the value of LOI.

Results: 11 samples with LOI 26, 15 samples with LOI 18 (the staple burns), 22 samples with LOI 21, 2 samples with LOI 19. The values are inconsistent and the fiber is not suitable as flame retardant.

EXAMPLE 11

Flame retardant polypropylene fiber in staple A polypropylene fiber was made in the same way as in Example 1, but with a lower proportion of PP with high MFI in the master.

Composition of the master:

calcium hypophosphite 19.40% melamine hydrobromide 4.31% polypropylene MFI 25 dg / min 66.26% polypropylene MFI 1000 dg / min 8.48% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 1 , 30% dispersant zinc stearate 0.25%

The master, prepared as in Example 1, was added at 3% by weight to the base polymer, consisting of polypropylene with MFI 25 dg / min, and everything was spun as in Example 1.

Composition% of the components of the master flame retardant (FR) on the fiber:

calcium hypophosphite 0.447% melamine hydrobromide 0.099% polypropylene MFI 25 dg / min 1, 988% polypropylene MFI 1000 dg / min 0.254% 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl) 0.021% dispersant zinc stearate 0.008 % Of the 5 tons of fiber produced, as in Example 1, 50 samples were taken, in the same way, to determine the LOI according to the ASTM D2863 standard.

The results obtained still consist of 100% constant values, with LOI 25-26.

The present invention has been described with reference to some of its specific embodiments, but it is to be understood that variations or modifications may be made to it by those skilled in the art without thereby departing from the relative scope of protection.

Claims (24)

CLAIMS 1. Extremely low halogen content flame retardant polyolefin fiber containing a flame retardant masterbatch composition comprising in turn: a) one or more metal salts of hypophosphorous acid; b) one or more halogenated triazines; c) a polyolefin polymer having a Melt Flow Index (MFI) not lower than 100 dg / min; d) a polyolefin polymer having a Melt Flow Index (MFI) between 2 and 60 dg / min; the maximum particle size of said one or more metal salts of hypophosphorous acid not exceeding 15 μιτι, the composition of flame-retardant masterbatches being added to the polymer which constitutes the mass of the polyolefin fiber in such quantity as to result in a fiber containing: A) from 0.1% to 2% by weight of said one or more metal salts of hypophosphorous acid; B) from 0.02% to 0.75% by weight of said one or more halogenated triazines; C) from 0.1% to 3.5% by weight of said polyolefin polymer having MFI of not less than 100 dg / min; D) from 0.4% to 4.25% by weight of said polyolefin polymer having MFI between 2 and 60 dg / min. 2. A flame retardant polyolefin fiber according to claim 1, wherein said flame retardant masterbatch composition further comprises: e) a free radical generating compound, and said resulting fiber contains up to 0.25% by weight of said free radical generating compound. 3. Flame retardant polyolefin fiber according to claims 1 or 2, wherein said flame retardant masterbatch composition further comprises: f) a dispersing compound, and said resulting fiber contains 0.002% to 0.025% by weight of said dispersant compound. 4. Flame retardant polyolefin fiber according to any one of claims 1-3, wherein said flame-retardant masterbatch composition is contained in a proportion comprised between 2% and 5% by weight and in turn comprises: a) from 5% to 40% by weight of one or more metal salts of hypophosphorous acid; b) from 1% to 15% by weight of one or more halogenated triazines; c) from 5% to 70% by weight of a polyolefin polymer having a Melt Flow Index (MFI) not lower than 100 dg / min; d) from 20% to 85% by weight of a polyolefin polymer having a Melt Flow Index (MFI) between 2 and 60 dg / min; e) from 0 to 5% by weight of a free radical generating compound. 5. Flame retardant polyolefin fiber according to any one of claims 1-4, wherein said polyolefin polymer d) present in the flame-retardant masterbatch co-composition is the same polymer which constitutes the mass of said polyolefin fiber. 6. A flame retardant polyolefin fiber according to claim 5, wherein said polyolefin polymer is polypropylene homopolymer or propylene copolymerized with ethylene, pentene, hexene and / or other aolefins. 7. Flame retardant polyolefin fiber according to claims 5 or 6, wherein said polyolefin polymer is obtained with a Ziegler-Natta catalyst or is obtained with a metallocene catalyst. 8. Flame retardant polyolefin fiber according to any one of claims 1-7, wherein the weight ratio between said one or more metal salts of hypophosphorous acid and said one or more halogenated triazines is comprised between 1: 6 and 6: 1. 9. Flame retardant polyolefin fiber according to any one of claims 1-8, wherein said one or more halogenated triazines consist of melamine hydrobromide. 10. Flame retardant polyolefin fiber according to any one of claims 1-9, wherein said one or more metal salts of hypophosphorous acid consist of calcium hypophosphite. 11. A flame retardant polyolefin fiber according to claim 10, wherein the weight ratio between said calcium hypophosphite and said melamine hydrobromide is equal to 4.5: 1. 12. Flame retardant polyolefin fiber according to any one of claims 1-11, wherein said polyolefin polymer c) present in the flame-retardant masterbatch composition has MFI of not less than 400 dg / min. 13. Flame retardant polyolefin fiber according to claim 12, wherein said polyolefin polymer c) present in the flame-retardant masterbatch composition has MFI comprised between 800 and 1000 dg / min. 14 Flame retardant polyolefin fiber according to any one of claims 1-13, wherein said polyolefin polymer d) present in the flame-retardant masterbatch composition has MFI comprised between 20 and 30 dg / min. 15. Flame retardant polyolefin fiber according to any one of claims 1-14, wherein said flame-retardant masterbatch composition is contained in a proportion of 3% by weight. 16. A flame retardant polyolefin fiber according to any one of claims 2-15, wherein said free radical generating compound is 2,3-dimethyl-2,3-diphenylbutane (bis-cumyl). 17. Flame retardant polyolefin fiber according to each of claims 3-16, in which said dispersing compound is selected from metal salts of steraric acid, paraffin waxes and polyethylene waxes. 18. A flame retardant polyolefin fiber according to claim 17 wherein said dispersing compound is zinc stearate. 19. Flame retardant masterbatch for making flame retardant polyolefin fiber as defined in each of claims 1-18. 20. Fireproof masterbatch according to claim 19 obtainable in granules by extrusion. 21. Flame retardant polyolefin fiber in staple or yarn, obtainable by melt spinning with the use of a flame retardant masterbatch as defined in claims 1-18. 22. Fabrics, non-woven fabrics, carpets and carpets produced with the flame retardant polyolefin fiber as defined in claims 1-18 23. Process for the production of a flame-retardant polyolefin fiber with a very low halogen content, in which said fiber is obtained by spinning a polyolefin polymer from melt, by means of an extrusion operation through a spinneret, to the head of which it is dosed, in proportion comprised between 2% and 5% by weight, a flame-retardant masterbatch composition as defined in claims 1-18. 24. Process according to claim 23, wherein said flame-retardant masterbatch composition is dosed at 3% by weight.