DE4300390A1 - Preventing burning of plastics materials or plastics composites - by incorporating conventional flame retardant as microcapsules - Google Patents

Abstract

Ignition of plastics material and composites is prevented by adding flame retardant (I) in microencapsulated form into plastics compsn. (II) to be processed. Pref. (I) is tetrabromomethane, partially or fully brominated aliphatic cpd., other Br cpd. or other conventional flame retardant. Wall material of (I) microcapsules consists of polymeric thermoset and/or thermoplast and/or elastomer. Microcapsules have dia. 1-100 microns and are added as flowable material. Wt. ratio wall material to encapsulated (I) is 2:1-1:2. ADVANTAGE - Microencapsulated (I) are highly effective flame extinguishing agents, so limiting fire damage, and are relatively environmentally friendly; undesirable chemical reactions between (I) and (II), or permeation, absorption or adsorption of (I) which can lead to deterioration of properties are avoided. Highly active low mol. (I) with high vapour pressure can be use

Description

The invention relates to a method for preventing fire Ignition of plastic and plastic composite parts with simultaneous improvement of the fire extinguishing behavior by the Use of specially designed chemical compounds as Flame retardants in the structure of the construction or Functional materials.

In addition to the many advantages of using plastic on all ge offer the technology, is a particular disadvantage of flammability note this material group. This can not only irreparable damage caused by thermal factors exposures, but also the exposure to poisons. The possible formation of toxins of all hazard classes through the use of aromatic, halogenated, (iso-) cy anized and highly polymerized systems, including Ingredients, mapped out. The enthalpies of education are during a fire run through thermal and kinetic Given sizes.

To organic plastics u. a. also on the behavior in the above To be able to characterize the senses, it is international practice the component approval program of "Underwriters ′ Laboratories (UL) Component Recognition Program" to use for this. The relevant points from this need the Er wahnung:

• 1. (TI Temperature Index) temperature index,
  it represents the maximum temperature (0 ° C) up to or below which the material can be used with very little risk of failure due to thermal degradation.
• 2. (WWI Hot Wire Ignition) filament ignition,
  whereby test rods are wrapped with a resistance wire which is brought to a red glow. The seconds in which inflammation occurs are measured.
• 3. (UL 94 Flame Class-Vertical Burning Test) Flame level vertical fire test UL 94 V-0,
  This is a burning test on a laboratory scale of aged and unaged test specimens with ignition sources that are several times more effective.
• 4. (HAI High Amp Arc Ignition) Arc ignition high current, which is switched 40 × per min. Measured The number of arcing operations before ignition is increased dung.
• 5. (HVTR High Volt Track Rate) high voltage tracking resistance,
  In this test, an arc is drawn between the two electrodes under a voltage of 5200 V on the surface of the material. If the surface is carbonized, the electrodes are removed from each other at a certain speed and used as the measure mm / min.
• 6. (D 495 Arc Resistance) arc resistance,
  The "dry ASTM arc test method" is used. The frequency and current of the arc are increased every 60 s until the arc is no longer interrupted. The value to be reproduced represents the average number of s that are required before the rollover.
• 7. (CTI IEC Track) tracking resistance,
  The "wet ASTM arc test method" is used, in which the resistance of test specimens against the formation of creep marks or material removal is measured.

USA Underwriters ′ Laboratories UL Yellow Cards was released in March 1984 and is considered international User suggestions used, especially when there is a fire solutions seem possible.

The measurement of the thermal influence on the properties Changes in test specimens are described in DIN 53 446.

The fire trigger on an organic function or con structure system usually takes place at an ignition point by locally exceeding the ignition temperature. Be here the gaseous substances necessary for ignition (mostly radicals) exposed to the oxidizing agent (mostly air).

To this process initiated by thermal effects inhibit or delete almost all known plastics systems can be equipped with flame retardants, if their Areas of application require this.

Without going into an evaluation of the mechanisms of action some of the main flame retardant processes as characters State of the art listed:

• 1. increasing the proportion of inorganic atoms in the polymer,
• 2. mineral fiber and glass fiber filling of the polymer,
• 3. Use of special fillers, such as aluminum hydroxide Al (OH) ₃, Dawsonite NaAl (OH) ₂ CO ₃ , magnesium carbonate MgCO ₃ .H ₂ O, zinc borate Zn (BO ₂ ) ₂ .2H ₂ O, Na silicates,
• 4. post-chlorination, post-fluorination of polymers,
• 5. HT polymers with foreign atoms, such as P, As, B, S, Sb, Si and. a.,
• 6. Aramid fibers (aircraft textiles),
• 7. Use of poly (aryl) oxides, sulfides and sulfones.

In addition to the desired properties of flame protection are mostly undesirable side effects on other materials rameter the result, or it must be synthetically expensive (Hetero) polymers with lower flame retardant concentration ions are used.

All previous flame retardants have in common that they with their specific surface deposited in the plastic system Need to become. This gives you the opportunity to be unwanted chemical reactions, permeations, absorption and absorption may lead to an unwanted deterioration of the specific material parameters. It continues to have a disadvantage from that with the known "admixture technologies" not very much active but low molecular weight flame retardants with the here usual high steam pressures can be used, though only very low flame retardant concentrations in the polymeric materials would be necessary.

In summary, it can generally be stated that the material-related effect of flame protection at the expense of Properties of the basic material formulation goes.

The aim of the invention is that described Eliminate defects inherent in the prior art and reason additionally use material-compatible flame retardants that can also have a high internal vapor pressure and a high one Exercise effectiveness for the intended purpose.

According to the invention this object is achieved in that the known microencapsulation methods, e.g. B. from the through stationery technology (dye-leuco bases) and pharmacy (mi cro / nano encapsulation of active ingredients) for microparticulation of flame retardants is used, being used as capsule shells material is used in the one to be protected Plastic system is chemically and physically inert.  

Microencapsulation preferably involves substances which have free radical scavenger properties and thus chemically break off the radical chains which occur when plastic systems are ignited or burned. This quenching mechanism is considerably more effective than stopping the reaction due to flame suffocation due to water leakage from hydroxides and hydrates and / or CO ₂ emissions.

Is the retention of traditional flame retardants for Special applications offered, it is also in the area of Scope of property rights that these substances with the usual Processes microencapsulated can be used. In these Cases is based on the introduction of the chemical-physical Inert behavior referred to as a particular positive.

According to the invention, bromine compounds such as Tetrabromomethane, partially and fully brominated aliphates, brominated Microencapsulated wood oils, being used as an organic capsule material one is selected that with the host plastic harmonizes and does not affect the phase boundary stability. On the use of brominated diphenyl ether pointed out, although their use from the known Reasons should be excluded. Even with the planned Halogen substitution in extinguishing agents, e.g. B. by thermal activatable nitrogen oxide compounds, the Microencapsulated form of the flame retardant in the material structure be optimally effective.

Of the numerous processes for the production of microcapsules the following are relevant for the present application:

• - complex coacervation between positively and negatively charged Colloid polymers, the reaction conditions above pH Value and temperature settings are effected. (ARNEODO, C., BENOIT, J.-P., THIES, C .; S.T.C. Pharma 2, 303-306 (1986) BECHARDS, S., McMULLEN, J.N .; Pharm. 31, 91-98 (1986)),
• - polymerization to form various wall materials,  the capsule formation from internal diffusion processes dissolved monomers to the polar solvent. (HARMIA, T., SPEISER, P., KREUTER, J .; J. Microencapsulation, 3, 3-12 (1985)),
• - spray drying and similar processes, e.g. B. spray with Three-substance nozzle or enveloping by means of a rotating Disc according to DE 27 46 489 (April 19, 1979) and DD 2 39 951 (October 15, 1986).

The grain size of technical microparticles ranges from one gen 10 nm (pharmacy, flavors, etc.) up to a few mm (fertilizer tel, refractory additives u. a.) Capsule diameter. As a capsule mate rialien are used here by the biological Degradability up to firm or elastic high temperatures tur materials and generally from organic mate rialien exist, the micropar according to the specified procedures are ticulable.

Taking into account the mechanical and thermal influence kungen in plastics processing, e.g. B. Mixing, plastifi Ornamental, injection molding and pressing etc., must be realized capsule materials of the method according to the invention be set that meet the requirements of the processed Plastic correspond:

• 1. Mechanical resistance to external and internal pressure kungen,
• 2. thermal resistance to the processing parameters tern, the exposure of the capsules at Ent flame conditions must be preserved,
• 3. inert behavior towards the host material.

The usual monomers and prepolymers can be used for this known thermoset and thermoplastic families are used, so that in most applications the required compatibility must be guaranteed.  

From this, taking into account the production material leranzen of the construction and functional parts a grain band of 1 to 100 µm capsule diameter can be derived. Application drawn here is the mass ratio of casing material to Incapsulate 2: 1 to 1: 2.

The concentration of the flame retardant microcapsules in each Plastic type is u. a. according to those mentioned at the beginning UL test method and according to the expected thermal expo nated load and is in the size of 0.1 to 10 mass%.

The proposed method also leads to another surprising effect regarding environmental protection, because halogens, also bromine and bromine-containing compounds, as a relevant Kri be displayed. A plastic with a microparticle gated flame retardant only sets in the event of a fire so much incapsulate free that deletion occurs. After that The temperatures drop below the level that the further Expo nation would lead. One can at this point of a few apply process speak, the temperature being the controlled variable works.

In the event of damage (simplified), it can be assumed that the ignition of a plastic system takes place at a point where the ignition temperature is reached and an oxidizing agent (air, 21% O ₂ ) is present. It can also be assumed that the exposure of gases in critical mix with air causes the ignition. The subsequent combustion is a result of numerous reaction processes that take place analogously to the "RICE radical chain mechanisms". The cheapest way to extinguish this system is to block the occurrence of the radicals by means of suitable "radical scavengers" and thus to stop the chain reactions. As has been practiced for decades, the most effective way of doing this is through the easily atomizable bromine molecule (halogen fire extinguisher).

Above a temperature determined by the capsule material the encapsulate is preferably in the form of bromine compound  gene exposed. Because the burning of plastic materials through pyrolytic reactions usually initiated, acts here the "RICE'sche radical chain mechanism" with the expire the oxidation reactions. The radicals that occur are identified by the halogen phase was terminated and the fire extinguished. Here is also the reason why bromine and thermal according to the invention easily cleavable bromine compounds in microencapsulated form as new principle of action of flame retardants can be used should.

The economic expenses for the integration of mikroverkap rarely flame retardants in plastics and plastic composites materials is slightly above the conventional process point, at least as long as no large-scale production of these substances he follows. The high effectiveness of the flame extinguishing behavior and there with the damage limitation, combined with a relatively high Environmental friendliness, let the introduction of the process in are considered necessary for almost all applications.

Embodiment 1. Manufacture of microencapsulated flame retardants

Comprehensive references can be found in the following citations remove:

• 1) SLIWKA, W., microencapsulation, Angew. Chemistry, 87, 556-567 (1975),
• 2) ULLMANN: Encyclopedia of Technical Chemistry, Vol. 16, 675 ff.,
• 3) BORNSCHEIN, M., MELEGARI, P., BISMARCK, C., KEIPERT, S., Phar Mazie 44, 585-593 (1989),
• 4) JP 01 54 081 (89 54 081), (1.3.1989),
• 5) DIETRICH, K., BONATZ, E., et al., Acta Polymerica, 40, 325-331 (1989). "Amino resin microcapsules".

The following example is mainly shown with the inclusion of 5):
Test quantities used:
45.0 g multi-brominated aliphatic (example: 2,2,3,3-tetra bromobutane, mp. 243 ° C)
180 ml water
9 ml PIAMID (50% solids content)
"Partially methylated and partially etherified melamine-formaldehyde resin"
6.3 ml 2n citric acid (pH buffer)
2.7 g polyethylene glycol 2000 (0.1% of the total mass).

The brominated aliphatic phase is dispersed with the water portion using a ULTRA-TURRAX at 60 ° C at a high power level (approx. 20 500 min ^-1 ) for approx. 10 min. Then, with continued vigorous stirring, the PIAMID solution and, after the dispersion, citric acid as a catalyst (acid curing) and polyethylene glycol are added to stabilize the dispersion. The intensive stirring is continued with the ULTRA-TURRAX for 10 min, whereby the consistency changes. The microparticulation process can be followed by slide swabs and their microscopy. Then the stirring speed is reduced to 500 to 600 min ^-1 and continued for 60 min at 60 ° C. This is followed by post-curing at room temperature for 4 hours. The microcapsules are separated from the liquid phase and washed.

The separation of the flame retardant microcapsules into free-flowing Material is carried out according to the usual procedures. in the In the case of a second or multiple coating, the wet one filtered capsule mass again analogous to the procedure above se used, under the appropriate conditions also or several wrappings also with another polymeric Ma material can be carried out. The "armor" against us desired interactions with the host material is here procedurally included.

2. Use of the flame retardant microcapsules

The use in organic surface protection agents and decoration ren is done with admixture as part of the usual preparation technologies of these substances according to the characteristics of the claims che 3 to 5.

3. Use of other flame retardants

The flame can be processed in a comparable manner protective agents contained in the HUMMEL / SCHOLL "Atlas of Polymer and Plastic Analysis "and VOGEL, H." Flame Retarding Art stoffen "(A. HÜTHIG-Verlag), who is used the provided the diphenyl compounds and others in the meantime Dangerous substance groups do not rule out the use. For further use are the groups of urea, gua nidin, melamine and dicyandiamide classes including theirs Metal and halogen compounds included.

Claims (6)

1. A method for preventing the ignition of plastic and plastic composite materials by the use of tetrabromomethane, partially and fully brominated aliphatic and other bromine compounds, and other conventional flame retardants, characterized in that these flame retardant groups are added in microencapsulated form to the plastic polymer to be processed . 2. The method according to claim 1, characterized in that the Shell material of the flame retardant microcapsules made of polymeric Duro plastics and / or thermoplastics and / or elastomers. 3. The method according to claims 1 and 2, characterized in net that the flame retardant microcapsules diameter between 1 and Have 100 microns and used as a free-flowing material the. 4. The method according to claims 1 to 3, characterized in net that the mass ratio of the casing material to the encapsulate is between 2: 1 and 1: 2. 5. The method according to claims 1 to 4, characterized in net that the flame retardant microcapsule concentrate in the plastics trations 0.1 to 10.0% by mass. 6. The method according to claims 1 to 5, characterized in net that the nitrogenous compounds of the urea, Guanidine, melamine and dicyandiamide compounds used will.