Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Treating polymer containing material or treating a solid...
Reexamination Certificate
2001-06-06
2002-09-17
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Treating polymer containing material or treating a solid...
Reexamination Certificate
active
06451963
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process for the coagulation of PU dispersions, the coagulation products thus obtained and the use of the coagulated PU dispersions.
Reactive or post-crosslinkable PU dispersions are suitable as PU dispersions for the process according to the invention. The processes according to the invention comprise the production of films, the coating of a wide variety of materials and the partial or complete impregnation of nonwoven, knitted or other fabrics for strengthening purposes.
The coagulates produced by the processes according to the invention are suitable for use e.g. in the areas of clothing, protective clothing, shoe upper and lining materials, protective gloves, bag and upholstery material, coating of metals, medical and sanitary articles etc.
The production of coated textile fabrics, such as e.g. synthetic leather, has been known for a long time. The coating agent is applied on to the substrate in one or more coats by the direct spread coating process or by the transfer coating process. The coated textile fabrics may be used for the production of outerwear, shoe upper and lining material, bag and upholstery material etc.
SUMMARY OF THE INVENTION
The production of for example, gloves with latex dispersions or in recent years, owing to the occurrence of latex allergies, with polyurethane dispersions is known, the use of polyurethane dispersions for coagulation in particular causing significant technical problems.
DETAILED DESCRIPTION OF THE INVENTION
In the production of high-quality coated textile fabrics, flexibility, tensile strength and softness play a decisive role in terms of the desired comfort, among other things, since stiff fabrics lack comfort.
If the bonding of fibre intersection points is not avoided in the production of flexible coated textile fabrics, flexibility is lost and there is a risk of destroying the bond between textile fibres and binder when subjected to bending strain.
The undesired bonding of fibre bundles and thread intersection points can be avoided by treating the textile fabric e.g. with aqueous dispersions of organic binders and then coagulating these. In this way, increased tensile strength and greater softness of the coated textile fabrics are achieved.
The following methods of coagulation are known:
bath coagulation, in which the substrate is coated with a binder dissolved in an organic solvent (e.g. DMF, DMAC. DMSO THF) and the product thus obtained is passed through a bath of a non-solvent (e.g. water) miscible with the solvent; the coagulation takes place as a result of the extraction of the solvent by the non-solvent. Disadvantages of this process lie particularly in the necessary and costly measures for the safe handling, recovery and re-use of the very large quantities of solvent.
evaporation coagulation, which is based on the use of a volatile solvent and a less volatile non-solvent for the binder; with gentle heating, the solvent preferably escapes first so that the binder coagulates as a result of the constantly increasing proportion of non-solvent; in addition to the use of large quantities of solvents which is again necessary, the enormous technical effort required and the very limited opportunities for optimisation, owing to the process parameters, are disadvantageous.
salt, acid or electrolyte coagulation takes place by immersing the coated substrate or, as in the case of gloves, the form first immersed in the dispersion, in a concentrated salt solution or in acidified water or similar, the binder coagulating as a result of the high electrolyte content; disadvantages of this process lie in the technical complexity and above all the large amount of polluted waste water arising.
the prepolymer method, in which a substrate coated with isocyanate prepolymer is immersed in water and then a polyurea is formed with a porous structure, with the release of CO
2
. The disadvantages include the very high reactivity of the formulations and the associated short processing times; and
coagulation by temperature increase, which is possible for non-post-crosslinkable binders adjusted to be heat sensitive and which often leads to unacceptable results.
In summary, the above-mentioned methods either involve long periods of time for the complete removal of solvents, considerable costs in separating and recovering solvents and on-solvents, the disposal of acid- or salt-laden waste water or they do not lead to results of acceptable quality in every case.
The object of the invention consisted in providing a novel process for aqueous coagulation and products suitable therefor without the disadvantages described. It should enable products of high quality to be achieved in a simple process, with the aid of an aqueous dispersion without or with only a small content of organic solvents and without the use of salt, acid or electrolyte baths.
Surprisingly, it was found that the coagulation according to the invention can be achieved by using aqueous. post-crosslinkable polyurethane dispersions.
The use of the term “polyurethane” also includes polyurethane-polyurea.
The invention therefore provides a process for the coagulation of post-crosslinkable dispersions which is characterised in that post-crosslinkable dispersions are precipitated by thermal treatment at 50 to 120° C., forming a stable, at least partly crosslinked polyurethane or gel.
The process according to the invention is preferably carried out at 75 to 98° C.
The process according to the invention for the coagulation of post-crosslinkable PU dispersions is characterised in that post-crosslinkable dispersions having a content of
a) blocked isocyanate groups (calculated as NCO=42) of 0.1 to 7.5 wt. %, preferably 0.9 to 2.0 wt. %, and
b) a content of at least one polyamine with at least two (cyclo)aliphatically bonded primary and/or secondary amino groups and/or hydroxyamine, the equivalent ratio of blocked isocyanate groups from a) to amino groups from b) being 1:0.5 to 1:1.5, preferably 1:0.7 to 1:1.2, particularly preferably 1:0.9 to 1:1.1,
are precipitated by thermal treatment at 50 to 120° C., preferably 75 to 98° C., forming a stable, at least partly crosslinked polyurethane or gel.
The invention further provides the coagulates produced in accordance with the process according to the invention.
In the process according to the invention for the coagulation of post-crosslinkable dispersions, post-crosslinkable dispersions are precipitated by thermal treatment at 50 to 120° C., forming a stable, at least partly crosslinked polyurethane or gel, characterised in that the dispersions used have
a) a content of blocked isocyanate groups (calculated as NCO=42) of 0.1 to 7.5 wt. %, and
b) a content of at least one polyamine and/or hydroxyamine with at least two (cyclo)aliphatically bonded primary and/or secondary amino groups, the equivalent ratio of blocked isocyanate groups from a) to amino groups from b) being 1:0.5 to 1:1.5,
preferably post-crosslinkable dispersions are precipitated by thermal treatment at 75 to 98° C., forming a stable, at least partly crosslinked polyurethane or gel, characterised in that the dispersions used have
a) a content of blocked isocyanate groups (calculated as NCO=42) of 0.25 to 5 wt. %, and
b) a content of at least one polyamine and/or hydroxyamine with at least two (cyclo)aliphatically bonded primary and/or secondary amino groups, the equivalent ratio of blocked isocyanate groups from a) to amino groups from b) being 1:0.7 to 1:1.2,
particularly preferably characterised in that post-crosslinkable PU dispersions are precipitated by thermal treatment at 75 to 98° C., forming a stable, at least partly crosslinked polyurethane or gel, further characterised in that the dispersions used have
a) a content of blocked isocyanate groups (calculated as NCO=42) of 0.7 to 2 wt. %, and
b) a content of at least one polyamine and/or hydroxyamine with at least two (cyclo)aliphatically bonded primary and/or secondary amino groups, the equivalent ratio of blocked isocyanate groups from a) to amino groups from
Bälz Werner
König Eberhard
Langel Rolf
Schütze Detlef-Ingo
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