DE2244543B2 - Tri- (2,3-dibromopropyl) isocyanate, process for its production and its use as a flame-retardant additive for polymers - Google Patents

Description

Many plastics are flammable if they do not contain any flame-retardant additives; in particular this applies to polyolefins, polystyrene, polymethacrylates, polyvinyl acetate, polyvinyl acetate, polyamides, unsaturated Polyester resins and especially for polyurethanes. Some plastics are less light flammable and extinguish when an external flame is removed, e.g. B. polyvinyl chloride, polycarbonates and Epoxy resins; only very few plastics are incombustible at all, e.g. B. fluoroplastics, such as polytetrafluoroethylene.

When burning plastics, a distinction is generally made between two phases, namely

1. Elimination of volatile pyrolysis products when the plastic is heated and

2. Inflammation of the pyrolysis products and their own continued burning.

A number of flame-retardant additives for plastics are known. The flame retardant effect of the Additions can either affect the pyrolysis (phase 1) in favor of the formation more severe flammable volatile products or through the formation of a protective charcoal coating based, or the flame retardant itself supplies gaseous products, which the burning process (Phase 2) suffocate or inhibit by breaking off radical chain reactions. This the latter mechanism is assumed in particular for halogen-containing flame-retardant additives.

The previously known flame retardant additives fo ^r plastics belong substantially to one of the following three groups:

1. Inorganic additives

These are usually solid substances that are insoluble in organic media, which is why Tend to settle in liquid organic media. The most famous middle! of this type is antimony trioxide, the effect of which is usually increased synergistically by chlorine-containing additives. Further Inorganic additives are antimony trichloride and also ammonium phosphate, boric acid and ammonium sulfamate and dicyandiamide. In addition to the insolubility, there is another disadvantage of these additives to see that they are usually the transparency of plastics degrade.

2. Organic phosphorus compounds

These compounds have long been known as plasticizers in plastics technology, whereby it has been shown that they are also flame retardant Have properties. For many areas of application, e.g. for the production of rigid foams, however, the softening effect is not desirable. In addition, there are many organic ίο Phosphates tend to exude.

3. Organic halogen compounds

In this group, a distinction must be made between inert additives and reactive additives.

a) Inert additives

These include chlorinated paraffins and liquid chlorinated diphenyls as well as solid perchlorinated diphenyls. Furthermore, the use of Diels-Adler adducts of hexachlorocyclopentadiene known. Some of the compounds have a plasticizing effect Effect; in addition, many are insoluble in common organic media.

b) Reactive additives

Occasionally it is desirable to be flame retardant Polymerize monomers into the polymer. Reactive additives are used for this purpose Use which due to more responsive

Double bonds or reactive groups are able to take part in the polymerization. Examples are tetrabromobisphenol A (for epoxy resins) as well as HET acid anhydride and tetrabromophthalic anhydride ! for unsaturated polyester resins). The use

The availability of these additives is limited to special polymers.

There is a significant need for new flame retardant additives for polymers which are distinguished from the previously known means in that they

1. Are soluble in organic media and are thereby let it be distributed completely homogeneously without the risk of settling,

2. are chemically non-reactive and therefore very diverse Polymers can be added without the risk of undesired Participation in the polymerization reaction exists, and

3. Do not have plasticizing properties, ^D "so that they have the physical properties of the

Do not change the treated polymers.

It has surprisingly been found that tri- (2,3-dibromopropyl) isocyanurate is an additive for polymers with an excellent flame-retardant effect, which at the same time has the aforementioned properties has, namely is soluble in many organic media, low chemical reactivity, in particular also has no reactive hydrogen atoms and which has no plasticizing properties Has.

Compared to the flame retardant 1,3,5-tris- (1,2-dibromopropionyl) -hexahydro-s-triazine known from DT-AS 1 182 810 it is more accessible. It is obtained by bromination on an industrial scale Scale triallyl isocyanurate accessible from allyl chloride and sodium cyanate, while the establishment of the known connection a multiple

requires a step process, namely the conversion of acrylonitrile into acrylamide, the condensation of the amide with formaldehyde and the brorination of the 1,3,5-tris- (acryloyl) -hexahydro-s-triazine obtained. It is also thermally stable in a surprising and desirable manner than the known flame retardants, it decomposes only at about 21O ⁰ C, while the known compound turns brown already at 160 ⁰ C with evolution of gas.

The tri- (2,3-dibromopropyl) isocyanurate, which has the following structural formula

CH ₁ CHBrCR ₁ Br

, N

OC CO

! ι

BrH ₂ CBrHCH ₂ C - NN - CK ₁ CHBrCH ₁ Br

can be obtained by bromination of triallyl isocyanurate. In vinegar, the usual solvent for Brominations, the reaction can only be carried out with difficulty, since both the reaction product as Partially brominated intermediate compounds also precipitate insoluble, and higher-boiling solvents such as Carbon tetrachloride or chloroform have proven to be less suitable than the yields at reaction temperatures above 50 ° C drop sharply. According to the invention, the reaction guided so that the temperature does not exceed 50 ° C during the bromination; particularly preferred Therefore, methylene chloride is used as a solvent.

Tri- (2,3-dibromopropyl) isocyanurate can be added to numerous polymers and has been found to be useful at the same time as an excellent flame retardant Middle. The amounts used depend on the respective chemical composition of the polymer as well as its physical state. Usually amounts range from about 2 to 15, especially 5 to 10 percent by weight, based on the polymer, in order to achieve self-extinguishing properties.

The flame retardant according to the invention is particularly suitable for polyurethanes, in particular also rigid foams made of polyurethane, as it does not have a plasticizing effect. Particularly noteworthy is that the compound dissolves easily and without reaction in aromatic isocyanates. The additional amount for Polyurethanes is usually around 10 percent by weight, but are sufficient, for. B. with closed pore Foam amounts of as little as 8 percent by weight to achieve self-extinguishing properties.

Phenolic resins are widely used for the impregnation of various substrates. For example, papers for air filters in motor vehicles are impregnated with phenolic resins. For For such impregnation resins, a non-plasticizing soluble additive is particularly valuable; Tri- (2,3-dibromopropyl) isocyanurate has proven to be extremely suitable. In this case, the additional amount is strongly dependent on the flammability of the substrate to be impregnated and must therefore in individual cases can be determined empirically.

Tri- (2,3-dibromopropyl) isocyanurate dissolves in lower monomeric acrylates and methacrylates and can therefore form acrylic resins before they polymerize can be added. The additive remains clear in the polymers and has no plasticizing effect solved.

In the production of foams from poly-

For technological reasons, iQ styrene has to be flame-retardant Additives are added before the polymerization, but must not take part in the polymerization and should not sweat out of the end product or soften it. All these conditions are met by tri- (2,3-dibromopropyl) isocyanurate, which is another An essential advantage is that the compound is soluble in monomeric styrene.

Also for use as a flame retardant

In addition to being added to epoxy resin compositions, the solubility of the compound according to the invention, in addition to the lack of a plasticizer effect, is particularly positive. The compound can be dissolved both in the epoxy resin and in the hardener and added in this form. There is only a certain incompatibility with amine-based hardeners. To achieve self-releasing properties, as little as 5 percent by weight of the compound according to the invention can be sufficient.

Tri- (2,3-dibromopropyl) isocyanurate can also be mixed with other flame-retardant additives, especially antimony trioxide are used. The following are intended to explain the invention in more detail Examples serve.

example 1

Preparation of tri- (2,3-jibromopropyl) isocyanurate

249 g (1 mol) technical triallyl isocyanurate (content at least 97 Vo) were together with 150 ml Methylene chloride into a one equipped with a dropping funnel, stirrer and highly effective reflux condenser Given a round bottom flask. The addition funnel was filled with 481 g of bromine (3.009 moles) and 150 ml of methylene chloride loaded. With constant mechanical stirring, the bromine solution became within 90 minutes added to the submitted triallyl isocyanurate. The reaction started immediately (discoloration), and that Methylene chloride boiled after a few minutes. The reaction was finished as a slight one yellow-brown bromine color persisted for at least 10 minutes.

For working up, the reaction mixture was mixed with 500 ml of petroleum ether (boiling range 60 to 90 ° C.) and cooled while stirring. The reaction product co-crystallized as a white fine powder weak yellow tint. After cooling to 8 ° C. overnight to complete the crystallization was sucked off sharply without rewashing. The filter cake was then washed with 500 ml of methanol rubbed in and sucked off again. After washing several times with distilled water, the 80 ° C air-dried. The solvent used can be in a known manner by distillation reconditioned and reused. The yield of tri- (2,3-dibromopropyl) isocyanurate was between 9f) nnri for different approaches

95% of theory, The compound was obtained as a white dust fine crystalline powder whose melting point is at 110 ⁰ C. Decomposition occurs at 200 ^° C. with discoloration and the release of HBr.

The compound is easily soluble in methylene chloride, esters, ketones and aromatic hydrocarbons, It is very sparingly soluble in aliphatic hydrocarbons and alcohols and is insoluble in water.

Example 2

A rigid polyurethane foam with self-extinguishing properties was made by reacting diphenylmetban-4,4'-diisocyanate and a branched polyester made from adipic acid, phthalic acid and triol, the diisocyanate being 8 percent by weight (based on the finished polymer) of tri- (2,3-dibromopropyl isocyanurate) were added before the polyaddition. The manufacture of the hard tree took place in a manner known per se, a rigid foam S was obtained, which was found in the ASTM test as proved self-extinguishing. The physical properties of the rigid foam matched those of one untreated foam.

Example 3

A flexible polyurethane foam made from toluene diisocyanate and a linear polyether was produced analogously produced on the basis of propylene oxide / ethylene oxide in a manner known per se, with 8 percent by weight (based on the finished polymer) tri- (2,3-dibromopropyl) isocyanurate were added. The foam was self-extinguishing.

Claims (4)

Patent claims: 1. Tri- (2,3-dibromopropyl) isocyanuric. 2. Process for the preparation of tri- (2,3-dtbromopropyl) isocyanurate, characterized in that triallyl isocyanurate is reacted ^{with equimolar amounts of bromine at temperatures up to 50 2} C in an inert organic solvent. 3. The method according to claim 2, characterized in that the organic solvent Methylene chloride used. 4. Use of tri- (2,3-dibromopropyl) isocyanurate as a flame-retardant additive to polymers, especially polyurethanes.