Patent Application
20190367701
Fire and flame retardants are widely used as plastic additives for the safer use-in-service of the resulting plastic materials. For many applications such as wire and cable and electric and electronic applications the use of fire and flame retardants as part of the non-conducting insulation materials is mandatory.
There are many types of fire and flame retardants available. The most commonly used are the inorganic substances, the halogenated organic compounds, the organophosphorus compounds, or other organic substances.
Halogen-containing fire retarding additives are no longer fulfilling the conditions which are now demanded by various industry and governmental regulations. For example the polymer resins for e.g. electric and electronic applications have to comply with the RoHS15 and WEEE16 directives: 15: Directive 2002/95/EC on Restriction of certain hazardous Substances in Electric and Electronic Equipment 16 Directive 2002/96/EC on Waste of Electric and Electronic Equipment
The use of halogen-containing fire retardant additives or materials in plastics/polymers is also not allowed in the building and construction industries in Europe (Building European Union Construction Products Directive CE Marking 0123); nor in the transportation industry, such as railways (CEN/TS 45545), fire safety for sea vessels (ISO 5659-2 extended by ISO 21489) and in aircraft construction.
As an alternative to halogen containing flame retardants either
Mineral metal hydroxides are the most preferred of all non-halogen flame retardants. However, because of their low efficacy they need to be added in high dosages to meet the required properties to fulfill the regulations. High dosages make the processing difficult and less economical. Moreover the resulting plastic items show poor physical properties, and the disadvantage of energy wasting.
Intumescent systems, on the other hand, require lower dosages, but are susceptible to hydrolysis (instability towards water) and are, therefore, not desired for the electrical applications such as for the insulation of cables, electronics and building & construction. They do not meet ICE (IEV 212-01-01) E&E conformity of insulating materials over a longer period of time, due to the water pick-up. For example in Germany, the Deutsches Institut für Bautechnik (DIBIt) defines the standards for the intumescent systems to withstand the various environmental conditions, particularly the humidity.
The most commonly encountered problems are as following;
The fundamental issue of the most problems is the required high loadings of the flame & fire retardants, many times far exceeding even the weight of the basic polymers themselves. Hence, if the required ratio of polymer to fire and flame retardants in the compositions could be increased by reducing the loadings of the fire and flame retardants most of the said problems would be collectively resolved.
It has now been found that the use of the nitrogenous water-insoluble compounds, comprising or preferably consisting of an oligomer or a polymer of a 1, 3, 5-triazine derivative, and having the general formula I:
wherein
Compounds of formula I per se are described in the U.S. Pat. Nos. 4,504,610 and 8,202,924, and are used as fire retardants in combination with ammonium phosphate for so-called intumescence systems b) only. It has been assumed that the presence of phosphates as acid source for the fire resistant char formation is absolutely necessary (G Camino and R Delobel, Intumescence, Chapter 7, page 218-, in Fire Retardancy of polymeric materials edited by A. F. Grand and C. Wilkie; publisher Marcel Dekker Inc, New York 2000; ISBN 0-8247-8879-6).
Fire and flame retardants are as defined by the Phosporus, Inorganic & Nitrogen Flame Retardants Association (pinfa) and in “Non-Halogenated Flame Retardant Handbook, edited by A. B. Morgen & C. A. Wilkie; publisher Scrivener Publishing MA 01915-6106; 2014; ISBN 978-1-118-68624-9
An aspect of the invention, is therefore, polymer compositions containing fire and flame retardants and compounds of Formula I
wherein
Such compound is present in the composition in amounts from 0.1 to 10% by weight of the composition, preferably in amounts from 0.5 to 5% by weight.
As fire and flame retardants, phosphorus based flame retardants or inorganic flame retardants or nitrogen based flame retardants or halogen based flame retardants or N-alkoxy hindered amine radical generating fire and flame retardants can be used.
It has been found that the compounds of formula “I” surprisingly exhibit exceptional properties as fire retardant synergists by so-called “self-immolation” principle of fire retardancy, without the use of phosphates. In the event of a fire, compounds of formula “I” undergo a self-burning and charring process, thereby forming fire shields and nipping the fire in the bud. Table 1 below underlines such excessive char formation in the event of fire. Thus, there is a 15-20% more fire protecting char formation in case of samples containing compound of Formula II than in case of the samples not containing this compound.
The resulting polymer composites, such as EVA, containing such fire retardants according to this invention also release very low heat upon burning. Importantly, the smoke toxicity and corrosivity are also low because of low or no halogens in the fire retardants according to this invention. Table 2 and
Nano-clays and composites are also used as synergists for flame retardants. They are inorganic materials with the following advantages for the compounds of formula I:
Similarly, other inorganic compounds such as antimony oxides, and borate salts are also used as synergists for certain applications. However, their efficacy is low, as is to be expected of inorganic materials, alone due to their high density.
Organic synergists of high efficacy, as is to be expected due to their low density and better chemical relationship to the organic polymers, are few and far between.
Thus it has now been found that the compounds of Formula I are also suitable as synergists of halogen containing flame retardants in place of antimony oxides. Antimony oxides are no more desired as flame retardant synergists because of their potential toxicity.
For engineering polymers such as polyamides and polyesters, dialkyl phosphinates such as aluminium diethylphosphinate, with synergists, are commonly used as fire retardants. This chemistry increases corrosion in processing equipment and lowers mechanical properties (compounding world, December 2012). It has now been found that the compounds for Formula I combined with such dialkyl phosphinates do not cause such corrosion and degradation of the mechanical properties of the resulting polymer formulations.
It has also been found that compounds of I are also suitable as synergists for N-alkoxy hindered amine radical generating fire retardants such as Flamestab NOR of BASF, besides alleviating their deficiencies such as low heat stability.
The tests are done with the samples and have the purpose to give an assessment about the combustion behaviour under cone calorimeter conditions.
The ISO 5660 norm defines cone calorimeter parameters driving. During the cone calorimeter test, the materials are subjected to a heat flux of 50 kW/m2.
The samples are ignited by a spark created by an electrical device. Combustion products are aspirated in a duct, where they are analyzed.
Heat Release Rate (HRR [kW/m2) curve is obtained from measuring the oxygen percentage that is consumed during the combustion. HRR is one of the most used parameters to evaluate the burning behavior.
Other important factors are:
Flame Out (FO [s])
Peak of Heat Release Rate (pkHRR [kW/m2])
All tests are performed three times to check repeatability. All parameters are reported with their experimental deviation, calculated as (maximum value−minimum value)/2.
Surface temperature measurements were performed during cone calorimeter tests, using K-type 0.5 mm stainless steel sheathed thermocouple. Thermocouple was carefully placed and supported to keep contact with the upper surface of the sample throughout the experiment.
The temperature of the sample bottom layer was measured inserting a K-type 1 mm stainless steel sheathed thermocouple parallel to the specimen's surface between the polymer specimen and the aluminium foil.
The following examples illustrate certain embodiments of the invention.
The following materials were used
Formula II (Example 3 compound Ma of the U.S. Pat. No. 8,202,924)
The materials were dry-blended in the required proportions and extruded using a twin screw co-rotating extruder Leistriz 18-40D.
The resulting granulates were pressed to samples of 100 mm×100 mm×6 mm size and subjected to the cone calorimeter test as described above
Study on combustion behaviour and fire performance of polypropylene (PP) based composites
The following materials were used
The materials were dry-blended in the required proportions and extruded using a twin screw co-rotating extruder Leistriz 18-40D.
The resulting granulates were pressed to samples of 100 mm×100 mm×6 mm size and subjected to the cone calorimeter test as described above
With the calculation of reduction of heat release rate normalized by the content of polypropylene (PP), it can be clearly seen that compound of formula II could help to reduce the heat release rate of polypropylene (PP). The Heat Release Rate (HRR) and the peak Heat Release Rate (PkHRR) are reduced by 66.1 to 81.1%, a measure of the intensity of heat generated in the event of fire (Table 5).
Samples containing MDH performed better compared to CaCO3 containing composites. Moreover, the increased weights of the residues formed at the end of the cone test normalized by the content of non-combustible inorganic materials clearly indicate much slower or in-complete burning in the presence of the compound of Formula II (Table 4), and hence the better fire retardancy.
The foregoing results are illustrated on
Combination with Phosphinates
Combination with Halogenated Flame Retardants
Combination with NOR (N-Alkoxy Hindered Amines) Technology
Polyester Fibres in Combination with Compound of Formula III
The compound (CAS 63562-33-4) was obtained from Hongwei New Materials Technology Co. Ltd, PR China.
The process of making flame retarded polyester with compound II and Compound of formula III is briefly described as follows:
7.2 kgs of ethylene glycol and 10 kgs of dimethyl terephthalate are subjected to a transesterification process at temperatures between 170° C. and 220° C. in the presence of 2.3 g of Mn(OCOCH3).H2O to give the terephthalic acid-glycol ester pre-condensate.
500 g of the compound of Formula III and 3.5 g of Sb2O3 are then added at 220° C. The reaction vessel is now evacuated to a pressure of 1 mm Hg and heated to 250° C. (reaction mixture temperature) followed by polycondensation at 0.2 mm Hg and 275° C. until a relative viscosity of 1.85 is obtained. To the resulting polymer melt are now added 150 g of the compound of Formula II and stirred for 15 minutes.
Thereafter, the polymer is spun into the filaments following the usual process of making polyester fibre filaments.
The burning characteristics of flame retarded polyester are assessed by the common methods like Self Ignition Temperature (DIN 51794), Ignition Temperature (DIN 51794), Limiting Oxygen Index (LOI), Small Burner Test (DIN 53906).
The resisting fire-retarded polyester shows the following characteristics
| Number | Date | Country | Kind |
|---|---|---|---|
| 14003216.0 | Sep 2014 | EP | regional |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15668901 | Aug 2017 | US |
| Child | 16540745 | US | |
| Parent | 14842893 | Sep 2015 | US |
| Child | 15668901 | US |
