Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2001-10-10
2003-05-06
Truong, Duc (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S332000, C528S337000, C528S044000, C528S052000, C528S075000, C528S083000
Reexamination Certificate
active
06559274
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to compositions based on monoaspartic acid esters and polyaspartic acid esters, a process for their production, and their use as reactive components for polyisocyanates in two-component polyurethane systems.
Two-component (2K) coating agents that contain as binder a polyisocyanate component in combination with a component reactive with respect to isocyanate groups, in particular a polyhydroxyl component, have been known for a long time. They are suitable for the production of high-quality coatings that are hard, elastic and resistant to abrasion and solvents, and that in particular can also be formulated to resist weathering.
In the field of 2K-polyurethane coating technology, specific ester group-containing secondary polyamines have recently become established that are in particular suitable, in combination with lacquer polyisocyanates, as binders in low-solvent or solvent-free high-solid coating compositions and that permit a rapid hardening of the coatings at low temperatures.
These secondary polyamines are the so-called polyaspartic acid esters such as are described for example in EP-A 0 403 921. Their use alone or mixed with further components reactive with respect to isocyanate groups in 2K-PUR coating agents is described for example in EP-A 0 403 921, EP-A 0 639 628, EP-A 0 667 362, EP-A 0 689 881, U.S. Pat. No. 5,214,086, EP-A 0 699 696, EP-A 0 596 360, EP-A 0 893 458, DE-A 19 701 835 and U.S. Pat. No. 5,243,012.
The synthesis of polyaspartic acid esters is carried out by the addition of primary amines to an activated carbon double bond of vinylogous carbonyl compounds, as contained for example in maleic or fumaric acid esters and which is described in detail in the relevant literature (Houben Weyl, Meth. d. Org. Chemie Vol. 11/1, 272 (1957); Usp. Khim. 1969, 38,1933).
It has been found that this reaction sometimes does not go to completion during the synthesis (for example after 24 hours while stirring at 60° C.). The conversion rate of the reaction depends decisively on the type of primary polyamines used. The degree of conversion (measured on the basis of the concentrations of free, unreacted maleic and fumaric acid esters) after 1 day with 1,5-diamino-2-methylpentane is 90 to 93%. In contrast to this the degree of conversion when using a cycloaliphatic polyamine with sterically hindered amino groups (for example 4,4′-diamino-3,3′-dimethyldicyclohexylmethane) is only 77%. A complete or almost complete conversion is sometimes achieved only after several months.
These incompletely reacted products contain unreacted primary amino groups and possibly also free primary polyamines as well as the corresponding amount of unreacted maleic or fumaric acid esters. As a result, after the production of the products the latter continue to react during subsequent storage and accordingly the viscosity of the reaction mixture rises constantly until complete conversion has been attained. In addition, the reactivity of the product with respect to isocyanates decreases with the reduction in the concentration of primary amino groups. It is therefore sometimes not possible to ensure the establishment of a reproducible pot life.
Various solutions to the problem have already been described in the prior art, which however still do not provide ultimately satisfactory results.
It is possible to extend the reaction time or increase the reaction temperature. The first solution is often excluded for economic reasons. Increasing the reaction temperature to for example 80° C. or even 100° C. leads in turn to a increase in the color number of the product.
EP-A 0 667 362 and U.S. Pat. No. 5,243,012 describe extending the pot life of 2K-PUR binders based on polyisocyanates and polyaspartic acid esters by adding zeolites and/or organotin(IV) compounds. These measures are however only ameliorative and sometimes adversely affect other properties, and may for example lead to a turbidity of the lacquer or accelerate the NCO/OH reaction in the binder.
U.S. Pat. No. 5,821,326 describes how the reaction to produce monoaspartic acid and polyaspartic acid esters can be catalyzed by five-membered aromatic ring compounds. Although the catalysts used do indeed permit a more rapid conversion of the components, nevertheless in none of the quoted examples had a complete conversion of the reaction mixture been achieved within a reaction time of four days at 60° C. During the subsequent storage of the product mixture the viscosity of the product rises on account of the incomplete reaction.
In U.S. Pat. No. 5,216,170 the excess fumaric acid ester is removed by means of distillation and thus withdrawn from the reaction. This process is however time-consuming and energy-intensive and therefore does not provide a basis for a technically feasible process.
Accordingly, it is an object of the present invention to provide monoaspartic acid ester and polyaspartic acid ester systems that have an improved viscosity stability and thus storage stability without the quality of the resulting binders and/or coatings being adversely affected.
This object may be achieved by a thiol compound to an incompletely reacted reaction mixture, which during storage leads to a significantly lower rise in viscosity of the product and moreover the end product does not suffer from malodorous side effects due to the thiol compounds that are used. The effect of adding the thiol compound is that the unreacted portion of the vinylogous carbonyl compound is no longer available to undergo further reaction with the primary amines.
SUMMARY OF THE INVENTION
The present invention relates to a composition containing monoaspartic acid esters and polyaspartic acid esters of formula (I),
X—[NH—CH(CH
2
—COOR
2
)—COOR
1
]
m
(I)
in which
X represents an m-valent organic radical obtained by removing the primary amino group or groups from a corresponding monoamine or polyamine in the molecular weight range from 60 to 6000 containing (cyclo)aliphatically or araliphatically bound primary amino groups,
R
1
and R
2
represent identical or different organic radicals, and
m represents an integer ≧1,
as well as an addition product prepared from a compound of formula (II) (component A),
R
1
OOC—CH═CH—COOR
2
(II)
wherein the radicals R
1
and R
2
have the aforementioned meanings,
and a thiol compound of the formula (III) (component B),
[HS]
n
—R
3
(III)
in which
R
3
represents an n-valent organic radical optionally containing one or more heteroatoms, which may also contain other functional groups that are reactive or inert with respect to isocyanates, and
n represents an integer ≧1 and ≦4.
The compositions according to the invention are products having improved viscosity stability.
DETAILED DESCRIPTION OF THE INVENTION
The present invention also relates to a composition containing monoaspartic acid esters and polyaspartic acid esters of formula (I),
X—[NH—CH(CH
2
—COOR
2
)—COOR
1
]
m
(I)
in which
X represents an m-valent organic radical containing one or more heteroatoms, obtained by removing the primary amino group or groups from a corresponding monoamine or polyamine in the molecular weight range from 60 to 6000 containing (cyclo)aliphatically or araliphatically bound primary amino groups, which may contain further functional groups that are reactive with respect to isocyanate groups and/or are inert at temperatures up to
R
1
and R
2
represent identical or different alkyl radicals each having 1 to 18 carbon atoms and more particularly preferably represent identical or different alkyl radicals each having 1 to 8 carbon atoms, and
m represents an integer ≧2 and more preferably =2,
as well as an addition product prepared from a compound of formula (II) (component A),
R
1
OOC—CH═CH—COOR
2
(II)
wherein the radical R
1
and R
2
have the aforementioned meanings,
and a thiol compound of the formula (III) (component B),
[HS]
n
—R
3
(III)
in which
R
3
represents a
Gertzmann Rolf
Groth Stefan
Schmalstieg Lutz
Gil Joseph C.
Roy Thomas W.
Truong Duc
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