Polyurethane/polyurea-forming compositions

Details Polyurethane/polyurea-forming compositions Polyurethane/polyurea-forming compositions

2000-10-19

2002-04-09

Gorr, Rachel (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C252S182170

Reexamination Certificate

active

06369156

ABSTRACT:

This invention relates to a curative composition for the room temperature curing of polyisocyanates, a curable composition containing said curative composition, a process for the preparation of cured polyurethanes/polyurea and the polyurethane/polyurea castings obtained by said process.
Aromatic thioether groups containing amine curatives are well known, for instance from U.S. Pat. No. 5,962,619, and are widely used in the preparation of poly urethane/urea elastomers. One of the major problems is that the aromatic thioether groups containing amines are generally very smelly on their own and, since they are not very stable to atmospheric oxygen, they have the tendency to release some even more malodorous byproducts. However, unlike other widely used aromatic amine curatives like diaminodiphenyl methane (DDM)or 4,4′-methylenebis(2-chloroaniline) (MOCA), they are not carcinogenic and therefore safer to handle. Furthermore, the colour of thioether groups containing aromatic amines is easily affected by the presence of acidic species which cause an unacceptable darkening of the composition within a couple of weeks or even hours. Such acidic species can be generated by hydrolysis of aromatic phosphate ester plasticizers present in the composition. This problem could be avoided by using, for instance, phthalate plasticizers. However, unlike the latter, phosphate ester plasticizers have the advantage of being of low viscosity and much safer to handle and they do not need any hazard labels.
It has now been found that the problems delineated above can be solved by the addition of a small amount of an aldehyde or a compound which forms an aldehyde upon reaction with water to a curative mixture containing a thioether group containing aromatic amine and a non-volatile phosphate ester plasticizer. The novel curative compositions are suitable for room temperature curing of polyisocyanates and polyisocyanate prepolymers. The discoloration and the strong malodorous smell which usually appears during application of thioether group containing aromatic amines is prevented or neutralised, respectively.
Accordingly, the present invention relates to a curative composition comprising
(a) an aromatic polyamine containing at least one thioether group,
(b) a phosphate ester having a vapor pressure of less than 2000 mPa at 25° C.,
(c) an aldehyde or a compound which forms an aldehyde upon reaction with water.
Component (a) preferably is a compound of formula Ia or Ib
wherein R
1
and R
2
independently of one another denote C
1
-C
6
alkyl, n is an integer from 1 to 3, m is an integer from 0 to 3, with the proviso that m+n≦4, and X is a linear or branched C
1
-C
12
alkylene radical.
R
1
and R
2
in formula Ia can independently of one another be, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl and n-hexyl.
In the preferred compounds of formula Ia R
1
is methyl and n is 1 or 2. Further preferred compounds of formula Ia are those wherein R
2
is methyl and m is 0 or 1.
Particularly preferred components (a) are compounds of formula Ia wherein R
1
and R
2
denote methyl and compounds of formula Ib, wherein X denotes ethylene.
The most preferred compounds of formula Ia and Ib are 3,5-dimethylthio-2,4-toluenediamine, 3,5-dimethylthio-2,6-toluenediamine and 1,2-bis(2-aminophenylthio)ethane.
Component (b) is preferably a compound of formula IIa, IIb or IIc
wherein R
3
is hydrogen or unsubstituted or alkyl-substituted C
2
-C
6
alkyl, R
4
, R
5
, R
6
, independently from one another, are unsubstituted or alkyl substituted C
1
-C
5
alkyl and R
7
, R
8
and R
9
independently of one another are unsubstituted or alkyl-substituted C
1
-C
5
alkylene, and aromatic rings A, B and C independently of one another can have one or more alkyl substitutions.
Representative compounds falling with formula (IIa) are pentyl diphenyl phosphate, hexyl diphenyl phosphate, heptyl diphenyl phosphate, octyl diphenyl phosphate, nonyl diphenyl phosphate and C
1
-C
3
alkyl substituted compounds thereof, such as isodecyl diphenyl phosphate (Santicizer 148) and 2-ethylhexyl diphenyl phosphate (Santicizer 141, Solutia) and Santicizer 2148 (Solutia). Representative compounds falling with formula (IIb) are triphenyl phosphate and tricresyl phosphate. Representative compounds falling with formula (IIc) are tris(methoxymethyl)phosphate, tris(ethoxymethyl)phosphate, tris(propoxymethyl)phosphate, tris(butoxymethyl)phosphate, tris(pentoxymethyl)phosphate; tris(2-methoxyethyl)phosphate, tris(2-ethoxyethyl)phosphate, tris(2-propoxyethyl)phosphate, tris(2-butoxyethyl)phosphate, tris(2-pentoxyethyl)phosphate; tris(methoxypropyl)phosphate, tris(ethoxypropyl)phosphate, tris(propoxypropyl)phosphate, tris(butoxypropyl)phosphate, tris(pentoxypropyl)phosphate; tris(methoxybutyl)phosphate, tris(ethoxybutyl)phosphate, tris(propoxybutyl)phosphate, tris(butoxybutyl)phosphate, tris(pentoxybutyl)phosphate; tris(methoxypentyl)phosphate, tris(ethoxypentyl)phosphate, tris(propoxypentyl)phosphate, tris(butoxypentyl)phosphate and tris(pentoxypentyl)phosphate.
Tributoxyethyl phosphate and isodecyl diphenyl phosphate are especially preferred as component (b).
Basically, any aldehyde or any compound which forms an aldehyde upon reaction with water can be employed as component (c).
Examples for suitable aldehydes are formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, benzaldehyde, furfuraldehyde and citral. Compounds which form aldehydes upon reaction with water are primarily cyclic aminals like oxazolidines and oxazines.
In a preferred embodiment of the invention, component (c) is paraformaldehyde, benzaldehyde, citral, furfuraldehyde or an oxazolidine derivative.
Component (c) is preferably a compound of formula IIIa or IIIb
wherein R
10
denotes a monovalent organic radical containing 1 to 20 carbon atoms, R
11
is hydrogen or an unsubstituted or halogen substituted C
1
-C
12
alkyl, C
1
-C
12
alkoxy, C
1
-C
12
alkoxyalkyl, C
5
-C
14
aryl or C
6
-C
20
aralkyl and Y is a bivalent organic radical containing 1 to 30 carbon atoms.
More preferably, component (c) is a compound of formula IIIa wherein R
10
denotes an unsubstituted or halogen substituted C
1
-C
12
alkyl, C
1
-C
12
alkoxyalkyl, C
5
-C
14
aryl or C
6
-C
20
aralkyl and R
11
is hydrogen or C
1
-C
12
alkyl, or component (c) is a compound of formula IIb wherein Y is unsubstituted or halogen substituted C
1
-C
20
alkylene, —CH
2
CH
2
—[OCH
2
CH
2
]
k
—, —CH(CH
3
)CH
2
—[OCH(CH
3
)CH
2
]
k
— —CH
2
CH
2
—[OCH
2
CH
2
]
p
—OCOO—[CH
2
CH
2
O]
p
—CH
2
CH
2
— or —[CH
2
CH
2
]
p
—OCOO—[CH
2
CH
2
]
p
—, wherein k and p denote an integer from 1 to 10.
Oxazolidines according to formulae IIIa and IIIb are known and partly commercially available, like for instance the Incozol® series supplied by ICL.
The compounds of formula IIIa1 and IIIb1
wherein R
11
is C
1
-C
12
alkyl and Q denotes C
2
-C
8
alkylene, are particularly preferred.
The most preferred oxazolidine is the compound of formula IIIb2, wherein Q is ethylene and R
11
is isopropyl (commercially available as Incozol® LV).
In the curative compositions according to the invention the relative amounts of components (a), (b) and (c) can vary within wide ranges. The weight ratio of components (a):(b) is preferably 0.5-10.0:1, more preferably 0.7-5.0:1 and most preferably 0.9-1.5:1. The amount of component (c) is preferably 0.01-10.0% by weight, more preferably 0.05-5% by weight and most preferably 0.1-2.0% by weight, based on the total composition (a)+(b)+(c).
Customary additives, like fillers, stabilizers, dyes, and pigments can also be incorporated in the curative compositions.
Small amounts of essential oils like pine oil can be added to give the curative compositions an agreeable odor.
In a preferred embodiment, the curative compositions additionally contain a polyether- and/or polyester-polyol.
The curative compositions according to the invention are useful for the room temperature curing of any types of isocyanate group containing monomer

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