NO764292L - - Google Patents

Description

The easy combustibility of many thermoplastics is an obstacle to their wide spread, so that there has been no shortage of attempts to make such thermoplastics non-flammable. For this purpose, numerous substances are used to be mixed with the thermoplastics, then alone or together with other synergistically acting substances to achieve the desired flame retardant effect.

The majority of these so-called flame retardants contain in their molecules bound halogen, e.g. chlorine, but especially bromine. Compounds from the 5th group of the periodic table are preferably recommended as synergists, above all Sb2<0->5<<>

The flame retardants or flame retardant combinations are not without disadvantages. They are often poorly compatible with the thermoplastics and affect the surface of the objects made from them or even eventually diffuse out from the thermoplastics, i.e. they mostly form a chalky coating on the surface. This chalking occurs even faster at elevated temperatures and not only means a further deficiency, but often a serious danger, as in this way the flame protection agent is eventually lost and the objects designated as non-combustible lose this important property to the same extent.

It is also known that especially substances with a high bromine content, as they are desirable for achieving a usable flame protection, cannot be exposed to arbitrarily high temperatures during processing, as they then often begin to decompose and lead to the unusability of the mixtures.

The invention is based on the task of providing flame retardants which, neither when incorporated into plastics nor during further processing into molded bodies, for example by injection molding or extrusion, show decomposition phenomena at temperatures up to 300°C, at the same time are compatible with the plastic and also have a good flame retardant effect.

This task is solved by using oligomeric aryl esters with the general formula as flame retardants

wherein n = 3 to 22, preferably 7 to 15 and R means the iso- and/or terephthalic acid nucleus.

The object of the invention is consequently defined in claim 1.

The oligomers according to the invention are particularly suitable for flame-resistant finishing of molding compounds, which as a basic ingredient contain a high-molecular non-network-formed polycondensate, such as e.g. a high molecular weight linear polyester based on iso- and/or terephthalic acid or their esterifiable derivatives and diprimary glycols or glycol mixtures with 2 to 10 C atoms, e.g. 1,4-butanediol or 1,3-propanediol or a polycarbonate or a polyamide. The preferred polyesters are poly-tetramethylene terephthalate or polypropylene terephthalate, especially the former and the corresponding mixed polyesters, where part of the terephthalic acid is replaced by isophthalic acid, for example in the molar ratio TPS : IPS - 70 : 30 to 60 : 40.

In a preferred embodiment, the oligomer with formula I according to the invention is used as a flame retardant in the production of transparent molded bodies from transparent plastics.

Transparent plastics are e.g. amorphous polycarbonates or amorphous polyamides.

Preferred transparent polyamides are prepared

of terephthalic acid and/or isophthalic acid or their polyester-forming derivatives, preferably their mono- or dialkyl esters, preferably dimethyl terephthalate and C-alkyl substituted hexa-

methylenediamines, preferably 2,2,4- and/or 2,H,4-trimethyl-

in

hexamethylenediamine. The production of such polyamides is discussed

for example in US patent no. 3*150,117 resp. in British Patent No. 1,049,987.

If transparent shaped bodies are to be produced, apart from the flame protection agent according to the invention, no other additives that affect the transparency are used. Optionally, however, such aids can be added that do not affect the transparency, such as e.g. release aids, for example lactones, such as g-propiolactone, ybutyrolactone and the like and other common additives that improve the processing properties of the molding compounds while maintaining transparency.

Generally, the flame retardant property of the oligomer with formula I to be used according to the invention is so good that when using transparent amorphous polyamides resp. polycarbonates, the addition of a synergistic agent, such as e.g. compounds from the 5th group of the periodic table, e.g. antimony oxides or antimonates or also boron compounds, zinc oxides, phosphorus-containing substances and the like.

Good results are obtained with such flame retardants according to the invention which correspond to formula I, the residue R consisting of the isophthalic acid nucleus and the terephthalic acid nucleus. For example, for an amorphous polyamide of DMT and 2,2,4/2,4,4-tri-methylhexamethylenediamine (1 : 1), the viscosity number is 125 (DIN 53727, 0.5 wt.g solution in m-cresol at 25°C), sufficient with only 5 wt#, referred to the overall mixture of oligomeric aryl esters according to the invention (TPS : IPS = 50 : 50), to obtain, without synergistically acting addition, the highest step of sample 94 from Underwriters Laboratories , namely VO/VO (the 1st measurement takes place on newly produced molding compound, the 2nd measurement after 7 days of storage at 70°C). The porosity of the polyamide is thereby so good that the original transparency is completely retained.

Amorphous polycarbonates also behave analogously. The oligomeric esters used according to the invention can, for example, be prepared by interfacial polycondensation of tetrabromobisphenol A and the dichloride of iso- and/or terephthalic acid. The end groups of the formed ester can be closed by adding suitable monofunctional substances for suspension, such as e.g. tribromophenol, without there being any change in the first step according to the invention of the oligomeric aryl ester, Expedient leads.

the polycondensation is carried out so that products with a melting range of over 250°C, preferably over 300°C, corresponding to a molecular weight of 4000 to 15000, preferably 5000 to 10000,

measured by gel chromatography.

As flame retardants, the oligomeric esters according to the invention are suitable, especially for such thermoplastics which require a high processing temperature, in the production of mixtures and in the further processing into shaped bodies. Due to the high thermal resistance, the oligomeric aryl ester according to the invention is particularly applicable for the production of such flame-protected molding compounds to be processed into molded bodies, which are exposed to relatively high thermal permanent loads during use, such as, for example, when they are used in electrical engineering.

In order to obtain a degree of compatibility of the flame retardant according to the invention with the thermoplastics used, flame-resistant prepared sprayed strips of the thermoplastic with dimensions 127 x 12.7 x 1.6 mm, e.g. heated for 7 days in air at 70°C or 150°C, without even trace chalking being observed. Even after 28 days of storage at 150°C

the samples have not lost anything in their flame protection and still show the value VO in the test according to UL 94. If you weigh the sample in a fresh state after 28 days of storage at 150°C, you only find weight losses between 0.2 and 0.4$, further proof that the flame retardant also remains in the thermoplastic under extreme conditions and they are guaranteed permanent flame protection.

In principle, the thermoplastics used can also

be modified additives. In particular, reinforcing agents or fillers such as glass fibres, whiskers, asbestos, talc, chalk and similar substances may be mixed in, which in a known manner improve certain properties of the thermoplastics and are mixed in usual concentrations. The flame retardants according to the invention are also particularly suitable for flame fixing glass fiber reinforced polytetramethylene terephthalates or polytrimethylene terephthalates. With such molding compounds, it is appropriate to also use a synergistic agent, e.g. antimony trioxide, for example in amounts from 2 to 6% by weight, referred to the overall mixture. The floc protection agents can be added separately from the other additives or also

together with them to the basic components.

The composition of the flame retardant and possibly other additives can optionally be carried out using a twin-screw extruder (Werner and Pfleiderer ZDSK 28) with a kneading and mixing zone.

For example, when composing poly-tetramethylene terephthalate red, you work at the following temperatures: Zone 1 (absorption zone) 220°C, zone 2 (240°C, zone 3 250°C, zone 4 250°C, zone 5 250°C, zone 6 ( nozzle) 230°C.

Depending on the softening ranges for the plastics used according to the invention, the temperature in the mixing tools corresponding to the requirements may possibly be below 220°C or also above 250°C, for example at 280°C.

The UL 94 test (Underwriters Laboratories, USA) is carried out as follows:

A specimen (5 inches long, \ inch wide,

1/8 to 1/16 inch thick) flame treated vertically in a protective box from below with defined burner flame for 10 seconds. The fire classes VO, VI and VII are then determined as follows:

VO: No afterburning time over 10 seconds, mean value of the afterburning time not over 5 seconds, afterglow not over 30 seconds.

V I: No afterburning time more than 30 seconds, mean value not more than 25 seconds, afterglow not more than 60 seconds.

V II: As soon as under the above conditions of dripping parts the waste ignites.

Not passed:

Burn time over 30 seconds, average value over

25 seconds. The flame treatment is carried out at the extinguished end yet another time.

The examination is carried out on samples that have been stored for 48 hours under 50% humidity at 23°C and is repeated on samples that have been stored for 168 hours at 70°C.

The reduced viscosity is calculated according to the following

formula:

where n is the viscosity of the solvent (60 parts by weight phenol + 80 parts by weight 1,1,2,2-tetrachloroethane).

no = viscosity of the solution and

c = concentration of the solution (1 g/100 cm^)

(measured at 25°C).

Example 1.

Preparation of the brominated polyaryl ester based on tetrabromobisphenol A 6g iso-/terephthalic acid dichloride.

54.4 g (0.1 mol) tetrabromobisphenol A and 8 g

(0.2 mol) of sodium hydroxide is dissolved in 120 ml of water while salt is formed. With vigorous stirring, the solution of 10.15 g (0.05 mol) isophthalic acid dichloride and 10.15 g (0.05 mol) terephthalic acid dichloride in 15 ml chloroform is added at once. During the self-heating of the mixture, a stirrable polyarylester suspension forms. After the end of the reaction, the mixture is stirred for a further 3 hours at room temperature and then filtered off and washed first with methanol, then with chlorine-free water.

After drying at 150°C, 65>3g of powdery, colorless polyaryl ester are obtained. The dividend is 97$. The product dissolves in chlorinated aliphatic hydrocarbons to clear solutions without residue. The reduced specific viscosity is equal to 0.13-The reduced specific viscosity ri spec. became

c

calculated according to the following formula: ri spec..=. t..-..t

t = solution transit time, t = solvent transit time, c = solution concentration 1 g/100 cm 3, measured at 25°C in chloroform.

Example 2.

86 parts PTMT (poly-tetramethylene terephthalate, ed. viscosity 1.36 dl/g). 10 parts oligomeric tetrabromobisphenol-A terephthalic acid ester, molecular weight 7000,

4 parts Sbj<O>^

are mixed with each other and extruded on a twin-screw extruder with mixing zone and kneading block at temperatures of 250 - 270°C into a strand of 3 mm diameter. The string is chopped into granules and the granules are sprayed in an injection molding machine into test specimens of 127 x 12.7 x 1.6 mm.

Example 3-

56 shares PTMT as example 1,

30 pieces of commercial 5-mm glass fiber board,

10 parts oligomeric ester of tetrabromobisphenol A

and a mixture of 50 mol% iso- and 50 mol% terephthalic acid, molecular weight 8200,

4 parts Sb2<0>3

mixed and processed on a single-screw extruder into a string of 3 mm diameter, which is then chopped into granules. Samples are made from the granulate as in example 1.

Example 4.

95 parts amorphous polyamide, commercially available under the designation "Trogamid T", viscosity number (DIN 53727) = 125, 5 parts oligomeric ester corresponding to example 2, however additionally produced with tribromophenol as end-group closure,

mixed and extruded at temperatures of 260 - 280°C as above, chopped into granules and sprayed into test specimens according to example 1. The test specimens have the same good transparency as the pure "Trogamid T".

Example 5»

92 parts polycarbonate, commercially available under the name "Macrolon" 3000, 8 parts oligomeric ester according to example 3, processed according to example 1 at 250 - 270°C into test specimens. The test specimens have an unchanged transparency compared to the pure polycarbonate.

The specimens formed according to examples 2-5 are subjected to the fire test according to UL 94 both in a fresh state and after 7 days of storage at 70°C. In addition, the specimens according to examples 2 and 3 were heated in air for 28 days at 150°C, because on the thus pre-treated samples to assess weight loss, the nature of the surface and any diffusion of flame retardant.

The results are listed in the following table.

Claims (6)

1. Oligomeric flame retardants of the general formula wherein n = 3 to 22, preferably 7 to 15 and R means the iso- and/or terephthalic acid nucleus. 2. Plastic molding compounds, containing as flame retardant oligomers of formula I in amounts from 3 to 20, fo±? gradually 5 to 15% by weight as well as possibly common additives. 3- Molding compounds according to claim 2, characterized in that transparent polyamides are used as plastics, which contain residues of cerephthalic acid and residues of C-alkyl substituted hexamethylenediamines or transparent polycarbonates. 4. Molding compounds_according to claim 2, characterized in that thermoplastic linear high molecular weight polyesters are used as plastics. 5. Molding compounds according to claim 4, characterized in that polypropylene terephthalate or preferably polytetramethylene terephthalate is used as plastic. 6. Molding compounds according to claims 2 to 5, characterized by an additional content of synergistically acting substances.