Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Patent
1980-06-04
1983-03-22
Cockeram, H. S.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
149 194, 523180, C08G 1862, C08G 1848
Patent
active
043776787
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to binders for polydiene, particularly polybutadiene composite propellants.
BACKGROUND ART
Binders in which the crosslinks are formed by subjecting a hydroxyl terminated polybutadiene and diisocyanate to urethane reaction have been disclosed as the binder for polybutadiene composite propellant, particularly propellant using a small amount of binder. Hydroxyl terminated polybutadiene used for such binder is represented by R-45 made by ARCO Chemical Co. Ltd. in U.S.A. and is a polymer having a functional group number of 2.2-2.5 and a number average molecular weight of 2,000-3,000, which is produced by radical reaction. In view of this functional group number value, it is apparent the structure of the nominally bifunctional polymer contains a relatively large amount of polymer having three or more functional groups, so that the content of the polymer having three or more functional groups in the above described hydroxyl terminated polybutadiene varies and therefore even if the amount of diisocyanate added is adjusted depending upon this variation when producing the binder, the physical properties of the produced binder are uneven and the reliability when using for production of propellant as the binder is adversely affected thereby. Furthermore, the formation of the crosslink upon curing of the binder is relatively rapid due to the above described cause and the reaction rate with diisocyanate is rapid because the above described functional groups are primary, so that the pot life in propellant formation is short. When a plasticizer is used in order to obviate this problem, the specific impulse of the propellant is deteriorated.
DISCLOSURE OF INVENTION
An object of the present invention is to obviate the above described defect and to improve the physical properties (elongation, tensile strength, Young's modulus) of the binder for propellant using a small amount of binder.
The essential feature of the first aspect of the present invention consists in that a polydiene glycol having a hydroxyl group number of 1.8-2.1 and a number average molecular weight of 1,000-5,000 is used as the polydiene glycol and the molecular weights and the mole amounts of a trifunctional crosslinking agent, a diisocyanate of curing agent and a bifunctional chain extender are selected depending upon the above described hydroxyl group number and molecular weight respectively to set the average molecular weight between the crosslinks obtained in the above described reaction to the value which provides good physical properties. The composition of the binder in each production lot is determined in order to obtain the above described set molecular weight, whereby the reliably good physical properties of the binder can be surely obtained. Further, the pot life of the composite propellant slurry using the binder is prolonged by using a polydiene glycol wherein the hydroxyl groups are converted into the secondary or tertiary hydroxyl groups. The essential feature of the second aspect of the present invention consists in that the number average molecular weight of the polydiene glycol is limited to 1,000-3,500 in the above described composition and a diene polymer having a functional group number of less than 1, preferably 0 is added to the above described composition whereby the amount of a plasticizer added is reduced or the addition is not necessary and the above described high reliability and the moldability are maintained.
The preferable average molecular weight between the crosslinks is 7,000-15,000, particularly 8,000-10,000.
Polydiene glycols to be used in the present invention include polybutadiene glycol, polyisoprene glycol and the like. Particularly polybutadiene glycol (referred to as "HTPB" hereinafter) is preferable and in the present application, the invention will be explained with respect to HTPB hereinafter.
A typical process for producing HTPB in the present invention comprises polymerizing butadiene in an organic solvent by using a dilithium compound as a catalyst, treatin
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Fukuma Daizo
Harada Kunihiro
Shirota Kensho
Suzuki Shigeru
Cockeram H. S.
Japan Synthetic Rubber Co. Ltd.
Nissan Motor Company Ltd.
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