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
2002-04-25
2004-12-28
Woodward, Ana L. (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...
C525S09200D, C525S179000
Reexamination Certificate
active
06835774
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to compatibilizing agents for blends of chlorine containing polymers and carbonyl containing compounds such as polyamide having improved mechanical and thermal properties. The compatibilizing agents are block copolymers of lactones and lactams prepared by sequential bulk polymerization using a mixture of at least one anionic polymerization initiator and optionally at least one co-initiator. Various thermal performance modifiers and impact modifiers can be utilized to improve the thermal properties as well as the impact resistance of a compatibilized blend.
BACKGROUND OF THE INVENTION
The first studies of the polymerization of lactones were in the 1930s by W. H. Carothers and his coworkers. Subsequently, the mechanisms of cationic, anionic, and coordination polymerization of various lactones were studied throughout the 1950's to the present. It is well known that polylactones, notably poly(&egr;-caprolactone), of high molecular weight mass exhibit a high compatibility and miscibility with many thermoplastics and elastomeric polymers. Polylactones having melting points lower than polyethylene are thermally stable up to 220° C. Above this temperature, they slowly depolymerize to yield lactone monomer and oligomer. Union Carbide, Solvay, and Daicel are commercial producers of a series of polycaprolactones possessing various ranges of molecular weights.
The first commercial polyamides also were developed by W. H. Carothers at the DuPont Company. He obtained many patents on polyamides produced from dicarboxylic acids and diamines. Shortly after DuPont's entry into the field, I. G. Farbenindustrie obtained patents for polymers based on the ring-opening polymerization of &egr;-caprolactam. Linear aliphatic polyamides, frequently referred to generically as nylons, rank among the most important commercial polymers. They were introduced in the 1930s as the first synthetic fiber, and subsequently as the first crystalline engineering thermoplastic.
Lactone and lactam polymerization caused by a ring-opening process can lead to high molecular weight polymers. Such polymerization of lactones usually has been conducted at relatively low temperatures in an appropriate solvent and at modest rates.
Solvent-free (i.e., bulk) polymerization has been of interest to industry because of its great economic savings. However, one of the problems of bulk polymerization is a difficulty of temperature control caused by exothermic reaction. U.S. Pat. No. 3,021,313 relates to aluminum alkoxides as initiators of the polymerization of monomeric cyclic esters in a conventional reactor. U.S. Pat. No. 3,021,016 relates to metal hydrides as initiators of the polymerization of monomeric cyclic esters in a conventional reactor. The polymers of the patents can be prepared via bulk, suspension, or solution polymerization.
Advantages of the screw extruder as a chemical reactor include fewer processing steps and no need for a solvent. On-line (i.e., in-situ) polymerization, mixing and compounding allow continuous downstream processing, easy devolatilization of by-product, and easy recycling of products. Thus continuous polymerization using a screw extruder (i.e., reactive extrusion) is attractive as an alternative to both bulk and solvent polymerization.
Continuous monomer polymerization of certain urethanes, lactams, acrylates, and styrene using a screw extruder is known in the prior art. Co-rotating and counter-rotating twin screw extruders are considered to be attractive chemical reactors providing good technical and economical means for polymerization and polymer modification.
In particular, continuous polymerization of &egr;-caprolactone in a screw extruder has become possible with alkoxymetallic complexes as initiators that result in short reaction times. U.S. Pat. No. 5,468,837 relates to reactive extrusion of &egr;-caprolactone using aluminum alkoxides. U.S. Pat. No. 5,801,224 relates to reactive extrusion of a cyclic aliphatic ester (e.g. a lactone monomer such as &egr;-caprolactone), optionally together with a secondary component containing hydroxyl or amino group functionality, using coordination insertion catalysts and/or initiators such as Lewis acids and metal alkoxides. The ester must contain less than 100 ppm water and have an acid value less than 0.5 mg KOH/g and preferably less than 0.2 mg KOH/g. It is indicated that higher water and acid content reduces overall polymerization rate and ultimately leads to lower conversion of monomer to polymer. Further, Gimenez et al. reported the reactive extrusion of &egr;-caprolactone catalyzed by tetrapropoxytitanium in Polymer Processing Society 14
th
Annual Meeting (Yokohama, Japan), PPS-14, pp. 629-630 (1998), and also in International Polymer Processing 15, pp. 20-27 (2000).
U.S. Pat. No. 2,251,519 relates to random polymerization of cyclic amides such as caprolactam, optionally together with cyclic esters such as caprolactone, using any of the alkali or alkali earth metals. However, the reaction was slow, e.g., ½ hour to 5 hours. U.S. Pat. No. 3,017,391 relates to faster polymerization of &egr;-caprolactam at lower temperatures using certain nitrogen-containing promoters together with alkali and alkali earth metal catalysts. U.S. Pat. No. 3,200,095 relates to reactive extrusion of 6-caprolactam using a mixture of an alkali metal salt of 6-caprolactam and certain N-substituted compounds free of primary amino groups, such as N-acetyl-6-caprolactam. U.S. Pat. No 3,371,055 relates to reactive extrusion of lactams using a catalyst such as certain alkali or alkali earth metal compounds or certain organometallic compounds of the first to third main group of the Periodic Table, together with certain activators such as acylated lactams and lactams having groups with acylating activity attached to the lactam nitrogen. An article by Kye et al. (Journal of Applied Polymer Science, Vol. 52, pp. 1249-1262 (1994)) relates to reactive anionic polymerization of caprolactam integrated with continuous melt spinning of polyamide-6 fiber.
U.S. Pat. No. 3,758,631 relates to block copolymers prepared by (1) end-capping and optionally chain-extending a polylactone diol with a diisocyanate and (2) thereafter reacting the first step reaction product with caprolactam in the presence of an anionic catalyst for the polymerization of caprolactam. The first step is said to take from about 15 minutes to 3 or 4 hours and the second step from 0.1 to 18 hours. However, the examples show reaction times of hours, making the process impractical for reactive extrusion.
British Patent No. 1,099,184 relates to poly(lactone-lactam)s in which as few as 5 for every 100 units of the polymer chain are amide units. The copolymers are solid crystalline materials having high melting temperature and being substantially insoluble in hydrocarbons. Although the patent states that it includes both random and block copolymers, it is apparent that only random copolymers were envisaged, since each example produced a material with a single, narrow melting point range. The patent also states that the polyesteramides can be blended with other polymers, but there is no teaching as to why or how this might be done.
An article by Goodman et al. (Eur. Polym. J., Vol. 20, No. 3, pp. 241-247 (1984)) relates to copolymers of &egr;-caprolactone and &ohgr;-lauryl lactam prepared via anionic polymerization. The products are said to have relatively random structures. However, it is known by those skilled in the art that random &egr;-caprolactone/&ohgr;-lauryl lactam copolymers do not work well if at all to compatibilize blending of PVC with other thermoplastics.
An abstract by Ha et al. presented at the Polymer Processing Society's Aug. 17-19, 1998 meeting in Toronto, Ontario relates to a simultaneous and to a continuous sequential bulk polymerization of lauryl lactam, caprolactone, caprolactam/lauryl lactam, and caprolactone/caprolactam using several anionic catalysts.
New block copolymers are desired that are both relatively easy to prepare, especially via rea
Kim Byong-Jun
White James L.
Hudak Shunk & Farine Co.
University of Akron
Woodward Ana L.
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