Energetic copolyurethane thermoplastic elastomers

Details Energetic copolyurethane thermoplastic elastomers Energetic copolyurethane thermoplastic elastomers

2000-03-02

2002-11-12

Gorr, Rachel (Department: 1711)

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...

C149S019400, C149S019600, C149S122000

Reexamination Certificate

active

06479614

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a thermoplastic elastomer, and is particularly concerned with an energetic thermoplastic elastomer having urethane moieties as its thermoplastic A segments.
BACKGROUND OF THE INVENTION
Thermoplastic elastomers typically consist of copolymer chains having monomers A and B distributed throughout the chains as ABA or AB, where the A is the hard segment providing the thermoplastic characteristic and B is the soft segment providing the elastomeric behavior to the polymer. Conventionally , the A segment is formed by a crystalline homopolymer and the soft segment is formed by an amorphous homopolymer.
Thermoplastic elastomers of the type ABA are usually obtained by polymerization the soft B segment followed by the addition of the hard A segment, which is crystallisable. To achieve this type of copolymerization, monomers of both types should have similar reactivity to provide a copolymer of controlled structure with suitable adjustable mechanical properties. A good example of this type of technology is the preparation of 3-azidomethyl-3-methyloxetane and 3.3-bis(azidomethyl)oxetane (AMMO/BAMO) energetic thermoplastic elastomer described in U.S. Pat. No. 4,707,540 to Manser et al. and U.S. Pat. No. 4,952,644 to Wardle et al. In this energetic thermoplastic elastomer (ETPE), the thermoplastic part is obtained by the crystallization of the BAMO polymer. Manser et al. also described the use of these AMMO/BAMO energetic homopolymers as prepolymers in making thermoset binders for use in propellants. To obtain the thermoset binders, Manser et al. would typically cure the AMMO/BAMO prepolymers with a triol and diisocyanate to form a chemically cross-linked matrix to obtain the desired binder.
In the case of copolymers of the type AB, the thermoplastic elastomers are usually obtained by mixing monomers that have compatible reactive ending groups. U.S. Pat. No. 4,806,613 to Wardle describes such a method of synthesis. Similarly to Manser et al., Wardle also uses BAMO as the crystalline hard segment. For this, he end capped both the A and B homopolymers with toluene diisocyanate (TDI) leaving at each end an unreacted isocyanate, mixing both homopolymers and joined them by using a small chain extender. Alternatively, Wardle used a block linking technique consisting of reacting the B block with phosgene or a diisocyanate followed by the addition of the A block to form the thermoplastic elastomer. Once again, the crystalline homopolymer BAMO which is an expensive starting material is required to form the hard segment of the thermoplastic elastomer.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an energetic thermoplastic elastomer that is inexpensive to produce by avoiding the use a crystalline homopolymer to form the A segment.
In accordance with one aspect of the present invention, there is provided a thermoplastic elastomer comprising copolymer chains having urethane moieties physically bonded to one another by hydrogen bonds to yield the hard segment of the thermoplastic elastomer.
More specifically, the thermoplastic elastomer of the present invention have copolymer chains, which may be represented by the formulae:
HO—P—(U—P)
n
—OH  (I)
wherein P is selected from the group consisting of
where the
R
1
groups are the same and selected from the group consisting of —CH
2
N
3
and —CH
2
ONO
2
;
R
2
is selected from the group consisting of —OCH
2
CH
2
O—, —OCH
2
CH
2
CH
2
O— and —OCH
2
CH
2
CH
2
CH
2
O—; and o and p are each ≧1; and
 where the
R
3
groups are the same and selected from the group consisting of —CH
2
N
3
or —CH
2
ONO
2
when R
4
are —CH
3
; or R
3
and R
4
are both —CH
2
N
3
R
5
is selected from the group consisting of —OCH
2
CH
2
O—, —OCH
2
CH
2
CH
2
O— and —OCH
2
CH
2
CH
2
CH
2
O—; and q and r are both ≧1
U is selected from the group consisting of
 and n is 1 to 100;
wherein the A block is provided by said U moieties and the B block is provided by the P moieties.
Preferably, P has a molecular weight ranging from about 500 to about 10,000.
In accordance with another aspect of the present invention, the thermoplastic elastomer further comprises a chain extender such as
or —OCH
2
—(CH
2
)n—CH
2
O— where n is 0 to 8.
In the presence of a chain extender, the copolymer chains of the thermoplastic elastomer of the present invention may further be described with the following structure:
HO—P—(U—(C—U)
a
—P)
b
—U—P—OH  (II)
wherein P, U and C, which is the chain extender, are defined above; a is 1 to 100 and b is 1 to 100.
Alternatively, the copolymer chains may have the following structure:
HO—P—U—(C—U)
x
—(P—U)
y
—(C—U)
z
—P—OH  (III)
wherein P, U and C are defined as above; and x, y and z are each 1 to 100.
The thermoplastic elastomer of the present invention is produced by drying a dihydroxyl terminated telechelic energetic prepopolymer having a functionality of two or less, and polymerizing the dried energetic prepolymer with a diisocyanate at a NCO/OH ratio ranging from about 0.7 to about 1.2, and preferably about one, under dried conditions. The use of dried reactants couple with providing a dried environment, i.e. avoiding the presence of water, during the polymerization step prevent the formation of undesired covalent bonds between the growing chains (chemical crosslinkings). This may be further prevented by purifying the diisocyanate prior to its use.
Preferably, the reaction is performed in the presence of a suitable catalyst such as dibutyltin dilaurate, which is added to the prepolymer prior to drying the latter to ensure its perfect dispersion in the prepolymer.
Suitable prepolymers are glycidyl azide polymer, 3-azidomethyl-3-methyloxethane, 3-nitratomethyl-3-methyloxetane, 3,3-bis(azidomethyl)oxetane and glycidyl nitrate that have molecular weights ranging from about 500 to about 10,000.
Suitable diisocyanates are 4,4′ methylenebis-phenyl isocyanate, toluene diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate.
Chain extenders such as 2,4-pentanediol, 1,3-propanediol, 1,4-butanediol or a diol having the formula: HO—CH
2
—(CH)n—CH
2
—OH where n is 0 to 8 may be added to vary the thermoplastic content of the copolymer and the mechanical properties of the thermoplastic elastomer.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides an energetic thermoplastic elastomer (ETPE) having linear copolymer chains having the formulae:
HO—P—(U—P)
n
—OH  (I)
wherein the macromonomers P are derived from energetic dihydroxyl terminated telechelic polymers having a functionality of two or less such as poly glycidyl azide polymer (GAP), poly 3-azidomethyl-3-methyloxetane (AMMO), poly bis 3,3-azidomethyloxetane (BAMO), poly 3-nitratomethyl-3-methyloxetane (NIMMO) and poly glycidyl nitrate (GLYN), with poly GAP being the most preferred compound.
U are components of diisocyanates such as 4,4′ methylenebis-phenyl isocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HMDI) and isophorone diisocyanate (IPDI).
The energetic thermoplastic elastomer of the present invention may further include a chain extender. Suitable chain extenders are:
and —OCH
2
—(CH
2
)n—CH
2
O— where n is 0 to 8.
In the present invention, the chain extenders serve a dual purpose. As usual, these chain extenders can be used to increase the molecular weight of the copolymers, but unlike conventional chain extenders, they are also used to increase the hard segment in the energetic thermoplastic elastomer.
The energetic copolymer (I) of the present invention is obtained by polymerizing a dihydroxyl terminated telechelic energetic polymer having a functionality of two or less such as poly glycidyl azide polymer, poly 3-azidomethyl-3-methyloxethane, poly 3-nitratomethyl-3-methyloxetane and poly glycidyl nitrate with a diisocyanate such as 4,4′ methylenebis-phenyl isocyanate, toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate at a NCO/OH ratio ranging from about 0.7 to about 1.

Affiliated with

Also associated with

Rating

Energetic copolyurethane thermoplastic elastomers does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Energetic copolyurethane thermoplastic elastomers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Energetic copolyurethane thermoplastic elastomers will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2926670