Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1997-08-27
1998-09-15
Mosley, Terressa
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528182, 528183, 528193, 528207, 528208, C08G 6928
Patent
active
058079726
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is directed to the subject matter indicated in the patent claims. More particularly, the invention is directed to a new and improved polycaprolactam (PA-6) with novel chain regulation.
Low-viscosity to medium-viscosity polycaprolactam (PA-6) for the production of injection molding compounds or fibers is usually produced by polymerization of caprolactam upon co-employment of chain regulators, such as acetic acid or other monocarboxylic acids. The molecular weight of the PA-6 is set to the desired value in this way and the viscosity stability of the PA-6 melt during processing is assured at the same time. By low-viscosity to medium-viscosity PA-6 is meant herein extracted products, i.e. products largely freed of caprolactam having a relative solution viscosity from about 1.65 to about 1.95, as measured in a 0.5 weight percent solution in m-cresol at 20.degree. C.
In addition to requiring a high processing stability, the production of fibers requires a defined and constant amino end group concentration in order to assure a good dye affinity. In order to achieve good results in the coloring with, for example, acidic colorants soluble in PA-6, the amino end group concentration in the fibers should ideally amount to 40-50 meq/kg.
The conditions are different given the injection molding modifications of low-viscosity through medium-viscosity PA-6 insofar as there are a number of products here that can be produced with good quality only given significantly lower amino end group concentrations of 25-30 meq/kg of the PA-6 utilized.
The following products or, respectively, product groups are among those included among these PA-6 injection molding materials: whose (co)polyolefin component is grafted with unsaturated carboxylic acids or, respectively, carboxylic acid derivatives or is chemically modified in some other way. Typical modification agents are, for example, (meth)acrylic acid and the esters thereof or maleic anhydride. For example, ethylene/propylene/(diene)-copolymers (EPDM), linear low density polyethylene (LLDPE) or other types of polyethylene are employed as (co)polyolefins. employ PA-6 with comparatively high NH.sub.2 -group concentration for such blends; the possible gain in impact strength or, respectively, notch impact strength is then at the expense of the injection molding processability. In particular, an extension of the cycle times and, thus, an extension of the productivity must be accepted when processing such materials. In addition to this, problems arise given pigmented materials, these being expressed in the non-uniformity of the pigment dispersion at the surfaces of the finished parts. employing PA-6 having a comparatively low NH.sub.2 -group concentration (25-30 meq/kg). For example, these products, which are added to the PA-6 melt in extruders, include melamine, melamine cyanurate, melamine phosphate and comparable materials. combustion test of Underwriters Laboratories and classified according to the corresponding UL 94 standard. and the quality of the flame-retardant nitrogen compound must be very well matched to one another. An important quality feature of the PA-6 is thereby the aforementioned range of the NH.sub.2 -group concentration.
It proceeds from the above comments, that the demands made of low-viscosity and medium-viscosity PA-6 for fiber and injection molding purposes cannot be met without further ado with one and the same product with respect to the amino end group concentration. No teachings may be found in the patent literature and other pertinent sources as to how the contrary demands made of fiber and injection molding PA-6 can be achieved with a uniform product.
SUMMARY OF THE INVENTION
The object of the present invention is thus to offer low-viscosity to medium-viscosity PA-6 for fiber and injection molding purposes that equally meets the demands made of both applications.
The object underlying this invention is achieved by providing PA-6 with a novel chain regulator whose manufacture ensues by hydrolytic polymeriz
REFERENCES:
patent: 4720538 (1988-01-01), Bartmann
Liedloff Hanns-Jorg
Morf Ernst
Schmidt Gerhard
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