Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-06-09
2002-02-19
Cooney, Jr., John M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S507000, C524S589000, C524S591000, C524S839000, C525S124000, C525S127000, C525S128000, C525S453000, C525S454000, C525S455000, C525S457000, C525S458000, C528S045000, C528S052000
Reexamination Certificate
active
06348548
ABSTRACT:
The invention relates to a method for manufacturing and the use of storage-stable, latent-reactive layers and powders of essentially aqueous dispersions, suspensions or solutions which contain surface-deactivated polyisocyanates and isocyanate-reactive polymers.
JP 09 188, 735 describes a mixture, storage-stable at room temperature, of dispersed functional polymers with a polyisocyanate. A predispersion consisting of polyisocyanate, of polymer stabiliser and of a hydrophobic fluid (as a dispersion agent) is emulsified in a further aqueous solution or dispersion of an isocyanate-reactive polymer with the aid of an o/w emulsifier and protective colloid. After the application and the evaporation of the water the polyisocyanate reacts spontaneously under cross-linking with the functional groups of the polymer.
In DE 31 12 054, DE 32 28 723 and DE 32 28 724 powder-like, fine-particled, solid polyisocyanates with particle diameters up to 150 &mgr;m are surface deactivated. By way of the surface coating the polyisocyanates retain their isocyanate content and their reactivity, and form a stable single component system also in water or aqueous solvents.
In DE 32 28 724 and DE 32 30 757 surface-deactivated, powder-like diisocyanates with polyols and aqueous dispersion polymers which contain functional groups are combined to a storage-stable reactive paste. By heating this water-containing paste to 140° C., i.e. above the reaction temperature of the polyisocyanate, the two components cross-link and a slightly foamed elastic coating is obtained.
A method for manufacturing stable dispersions of fine-particled surface-deactivated isocyanate is described in DE 35 17 333. The resulting stable dispersions are suitable as cross-linking agents.
A use of the aqueous dispersions of surface-deactivated, solid, fine-particled polyisocyanates as cross-linkers in textile pigment printing pastes and liquors is disclosed in DE 35 29 530. Subsequent to the application procedure the textile pigment, printing pastes and liquors are fixed on the tissue with hot air or steam.
A disadvantage of these systems described in these documents is however that the working steps of application and curing or cross-linking may not be separated, which would appear to be desirable with a multitude of uses for economical reasons as well as logistical reasons.
Thus a substrate which carries a storage-stable, latent-reactive layer or powder would open the possibility of being deposited at the location at which the suitable apparatus are present, of being stored for a predeterminable time duration and subsequently of being transported to the location at which the processing into further intermediate products or into the end product is effected.
Storage-stable, latent-reactive masses or layers are described in WO 93/25599. These consists of isocyanate-functional polymers which have a melting point of over 40° C. and of surface-deactivated polyisocyanates. For manufacturing the mixture, the components are melted on at temperatures which lie considerably above the softening point of the polymer. The expense with regard to the apparatus for the manufacture and the application of these masses, together with the energy costs are considerable. Furthermore in these systems for reasons of stability and processing only surface-deactivated polyisocyanates may be used which have a cross-linking temperature of over 80° C. Furthermore a directed and controlled inhomogeneous mixing of the components is the subject-matter of the application. This however demands complicated working steps.
It is the object of the present invention to manufacture storage-stable, latent-reactive, largely dry layers or powder with which also deactivated polyisocyanates with reaction temperatures below 80° C. may be applied, which from the point of view of environment protection behave advantageously and additionally may be inexpensively produced.
According to the invention this is achieved by the characterising part of the independent claims.
Storage-stable, latent-reactive layers or powder may accordingly be manufactured by the use of an essentially aqueous dispersion which contains at least one surface-deactivated polyisocyanate and at least one dispersed or dissolved polymer reactive with isocyanate.
Furthermore a method for the manufacture of storage-stable, latent-reactive layers or powders is the subject-matter of the invention, in which
a) an essentially aqueous dispersion or solution of at least one polymer reactive with respect to isocyanates and
b) at least one surface-deactivated, solid, fine-particled polyisocyanate essentially suspended in water are mixed,
c) this mixture selectively is deposited onto a substrate in a predeterminable layer thickness and
d) the water of the mixture is removed below the reaction temperature of the isocyanate,
so that the essentially dry and water-free layers or masses obtained by way of this, at reaction temperatures below the reaction temperature of polyisocyanate and polymer are storage-stable and latent-reactive.
Surprisingly it has been found out that the removal of the water and the drying of the mixture in the temperature region selectively may be effected at
i) room temperature up to the softening temperature of the functional polymer or
ii) above the softening temperature of the polymer
as long as the reaction temperature of the surface-deactivated polyisocyanate in none of the two case is exceeded. Independently of whether the drying is effected after i) or ii) the surface-deactivated solid, fine-particled polyisocyanates after the drying are distributed or embedded unchanged and unreacted in the largely water-free polymer or in the essentially water-free layer or powder. The dispersion, suspension or solution of polymer and suspended deactivated isocyanate blends into a continuous phase of uncross-linked polmers in which the unreacted surface-deactivated, fine-particled isocyanates are suspended.
In the case i) there results a water-free, dry, latent-reactive film or a latent-reactive powder, which at room temperature or at a slightly increased temperature is capable of storage. The ability of the surface-deactivated isocyanates to react with the functional groups of the polymers remains.
In the case ii) after the vapourisation of the water there results a melted system. As an example there serves the adhesing of a laminate of foils. Also in this phase the surface-deactivated isocyanates are unchanged and retain their reactivity. The adhesing is based firstly on the thermoplastic properties of the polymers.
In both cases the system cross-links and it becomes unmeltable and insoluble only on exceeding the reaction temperature of the surface-deactivated isocyanate. This is effected after a predeterminable time duration.
In certain cases a short-lived exceeding of the reaction temperature is sufficient in order to trigger the cross-linking reaction. The reaction or thickening temperatures of the deactivated polyisocyanates should with this have temperatures in the region of 30° C. to 180° C., preferably lie in the region between 40° C. and 150° C.
Thickening or reaction temperatures describe the temperature at which the surface-deactivating layer of the isocyanate dissolves or is destroyed in another manner. The polyisocyanate is set free and dissolved in the polymer. The end curing is effected by diffusion and reaction of the polyisocyanate with the functional groups of the polymer under a viscosity increase and cross-linking. The thickening and reaction temperature according to the type of surface-deactivated polyisocyanate lies above or below the softening temperature of the polymer.
The stability of the unreacted system, the reaction temperature and the course of the reaction are determined by the type of the polyisocyanate, by the type and the quantity of the surface stabiliser, by the solubility parameter of the functional polymer as well as by catalysers, softeners and other auxiliary means. These are largely described in the above mentioned patents.
Furthermore the processing steps of the substrate car
Bayer AG
Cooney Jr. John M.
Shoemaker and Mattare
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