DE3823988A1 - Insulating composition for producing an insulating layer for solid rocket propellants - Google Patents

Abstract

To produce a bubble-free insulating layer, use is made of an insulating composition comprising a curable mixture of polyols and polyisocyanates and also fillers and a zeolite.

Description

The invention relates to an insulating material for Production of an insulating layer for rocket-proof textile propellants or for lining combustion chambers; which is a curable mixture of at least one polyol and at least one polyisocyanate and at least one egg contains a filler.

To only burn off rocket solid propellants to allow the desired focal surfaces to take place Areas that should not participate in the erosion with an egg a well-adhering insulating layer. Wei The insulating layer also lends it to the fire any fuel present to provide some protection mechanical stress. For forehead burners, i.e. H. at the lateral surface and the top surface isolated The insulating layer also serves as propellants to the combustion chamber before the hot, when the To protect the fuel from the resulting gases.

The insulating layer is generally made of a hardenable ren binders, fillers and optionally catalyst ren and other auxiliaries. As curable Binder are mainly used polyols that deal with Polyisocyanates for polyurethane elastomers and resins implement, since it is with polyol binders and polyisocya nat hardeners are easily accessible materials, the the various demands of the missile con structure can be easily adjusted.

In the case of insulating layers for HTPB composite fuels as a binder usually the same binder as with fuel, thus hydroxyl-terminated polybutadiene (HTPB), used. In particular, carbon black is used as a filler improvement of the mechanical properties used.  

As a polyol binder for the insulating layers from doppelba sigen (DB) fuels are generally polyethylene lenglycol, polypropylene glycol, polycaprolactone or polyol, polytetramethylene glycol and mixtures thereof or similar polyhydroxyl compounds used implemented with di- or polyisocyanates as hardeners will. To increase the heat resistance, as fillers e.g. B. powdery or fibrous inert inorganic substances with low thermal conductivity or powdery endothermic decomposable substances, such as Acid amides added. To harden the Accelerate polyol / polyisocyanate mixture especially metal-containing organic catalysts used, for example organic mercury, lead or tin compounds, such as phenyl mercury oleate, Lead octoate or dibutyl tin dilaurate.

The curable is used to produce the insulating layer Insulating compound, for example, poured into the narrow gap sen or pressed between a mold and the Shell surface of the quicksat arranged in the casting mold zes is formed.

However, polyisocyanates react easily with the water from the air humidity according to the following schematic Equation:

The resulting carbon dioxide creates bubbles in the iso lierschicht, which are of appropriate size to Hinterbren or cause the engine to burst.  

To avoid the formation of CO ₂ , the polyols and the fillers must be thoroughly drained according to the prior art, the production of the insulating layer having to be carried out under anhydrous, air-conditioned conditions. Sharply dewatered polyols are, however, increasingly hygroscopic and require very rapid and proper work, which cannot always be guaranteed, particularly in an operational process.

The object of the invention is to blow the manufacture free insulation layers noticeably easier.

According to the invention, this is done by adding a zeolite reached to the insulating compound. The zeolite binds in the Raw materials present moisture as well as the damp action absorbed from the air by the insulating compound beers.

The zeolite should be as fine as possible, that is an average particle size of preferably 0.1 µm to 1 mm, in particular 1 to 50 µm (BET method).

In the manufacture of the insulating compound according to the invention is generally the polyol or the polyol mixture submitted and added to the filler, then if necessary, the curing catalyst is added sets and finally the hardener, i.e. the di and / or Polyisocyanate.

The zeolite is preferably added to the polyol or then the mixture of polyol and filler, in any case before adding the hardener.  

The zeolite can be added as a powder or paste. A paste, i.e. one with an organic liquid, like castor oil, pasted zeolite powder has the advantage partly that they are less hygroscopic and thus esp this is to be handled.

The zeolite must have a pore size such that it Is able to absorb water. The pore size of the Zeolites are usually at least 2 Ang flow, preferably 3 to 5 angstroms.

Sodium aluminosilicates have proven particularly suitable and sodium-potassium aluminosilicates of the zeolite A type grasslands.

The weight fraction of the zeolite is based on the insulating mass, preferably 0.5 to 10%, in particular 1 to 5%.

The ratio of the isocyanate groups of the polyisocyanate to the hydroxyl groups of the polyol (NCO / OH ratio) in the insulating compound is preferably 0.85 to 1.2: 1.0, especially 1.0: 1.0.

In addition to the polyol, the insulating compound can also have a diamine or polyamine, for example 4,4'-methylene-bis - (ortho-chloroaniline) or 3,3'-di-chlorobenzidine, the ready-to-pour insulating compound having 0 to 5% by weight .-% of the di- or polyamine may contain. The ratio of the isocyanate groups of the polyisocyanate to the hydroxyl groups of the polyol and the amine groups of the polyamine (NCO / (OH + NH ₂ ratio) is preferably from 0.85 to 1.2: 1.0, advantageously about 1.0: 1.0.

So less according to the present invention heavily dehydrated raw materials are used where through, for example, time and energy for drainage be saved and that for an extremely water precautions not necessary must be observed. The insulation according to the invention mass is also without higher humidity There is a risk of blistering. Eventually a security potential against unexpected and not certain moisture fluctuations in the off materials and the ambient air. The latter comes especially the demand for production security, d. H. consistent quality or minimum to the benefit of the committee.

The example below is for further explanation the invention.

It is a mixture of 48 parts by weight of a Polypro pylene glycols with an average molecular weight of approx. 4800 and 8 parts by weight of a polypropylene glycol with an average molecular weight of approximately 600 puts, which with 2 parts by weight of a zeolite A-Pul verse (Baylith L) and 30 parts by weight of a thermal soot. After stirring the mixture 0.25 parts by weight of phenyl mercury oleate Acceleration of the hardening reaction and 12 parts by weight Isophorone di-isocyanate added as a hardener and in Vacuum mixed in.

The mass obtained in this way is then applied to a solid propellant in a manner known per se, for example by casting, and is optionally cured at elevated temperature. The hardened mass is completely free of reaction bubbles caused by CO ₂ .

Claims (4)

1. Insulating composition for the production of an insulating layer for rocket propellants or for lining combustion chambers, which contains a curable mixture of at least one polyol and at least one poly isocyanate and at least one filler, characterized in that the composition contains a zeolite. 2. Insulating composition according to claim 1, characterized net that the zeolite is one for absorbing water has a suitable pore size. 3. Insulating composition according to claim 1 or 2, characterized ge indicates that the zeolite in a proportion of 0.5 to 10%, preferably 1 to 5% in the insulation mass is present.   4. Process for the production of the insulating compound according to egg nem of claims 1 to 3, characterized in that that the zeolite is added as a paste.