This invention relates to novel polymer product compositions, polymerization feed compositions and monomer purification therefor. In particular, it relates to a crosslinked, high modulus, high impact strength, thermoset polymer of polycycloolefin units which is formed via a metathesis-catalyst system.
Distillation is commonly used in the preparation of polycycloolefins, for example dicyclopentadiene. Various purities of dicyclopentadiene are available. The invention preferably uses economically available purified dicyclopentadiene which is readily polymerized. Purified dicyclopentadiene forms a substantially cross-linked thermoset polymer when polymerized as disclosed herein.
Any good thermoset polymer should meet at least two criteria. It should have desirable physical properties and it should lend itself to easy synthesis and forming. Among the most desirable physical properties for many polymers is a combination of high impact strength and high modulus. A standard test for impact strength is the notched Izod impact test, ASTM No. D-256. For an unreinforced thermoset polymer to have good impact strength, its notched Izod impact should be at least 1.5 ft. lb./in. notch. It is desirable that this good impact strength be combined with a modulus of at least about 150,000 psi at ambient temperature. Thermoset polymers with high impact strength and high modulus find useful applications as engineering plastics in such articles of manufacture as automobiles, appliances and sports equipment. Among the critical factors in the synthesis and forming of a thermoset polymer are the conditions required to make the polymer set up or gel. Many thermoset polymers require considerable time, elevated temperature and pressure, or additional steps after the reactants are mixed before the setting is complete.
A thermoset homopolymer having high impact strength and high modulus has been described by Klosiewicz in U.S. Pat. Nos. 4,400,340, 4,469,809 and 4,436,858 (with plasticizer) and by Leach in 4,458,037 (a foam). Characteristics of thermoset polymers include insolubility in common solvents such as gasoline, naphtha, chlorinated hydrocarbons, and aromatics as well as resistance to flow at elevated temperatures.
Work has been done on the metathesis copolymerization of dicyclopentadiene with one or more other monomers to produce soluble copolymers. This copolymer formation has resulted in the production of unwanted insoluble by-products. U.S. Pat. No. 4,002,815, for instance, which teaches the copolymerization of cyclopentene with dicyclopentadiene, describes an insoluble by-product and suggests that the by-product could be a gel of a dicyclopentadiene homopolymer.
Some other work, usually in an attempt to produce soluble polymers, has been done on the metathesis polymerization of dicyclopentadiene. Japanese unexamined published patent applications KOKAI Nos. 53-92000 and 53-111399 disclose soluble polymers of dicyclopentadiene. Several syntheses of soluble polymers of dicyclopentadiene have produced insoluble by-products. Takata et al, J. Chem. Soc. Japan Inc. Chem. Sect., 69, 711 (1966), discloses the production of an insoluble polymerized dicyclopentadiene by-product from the Ziegler-Natta catalyzed polymerization of dicyclopentadiene; Oshika et al, Bulletin of the Chemical Society of Japan, discloses the production of an insoluble polymer when dicyclopentadiene is polymerized with WCl.sub.6, AlEt.sub.3 /TiCl.sub.4 or AlEt.sub.3 /MoCO.sub.5 ; and Dall Asta et al, Die Makromolecular Chemie 130, 153 (1969), discloses an insoluble by-product produced when a WCl.sub.6 /AlEt.sub.2 Cl catalyst system is used to form polymerized dicyclopentadiene.
In U.S. Pat. No. 3,627,739 ('739), dicyclopentadiene is gelled with unactivated catalyst and then heated for an hour.
Pampus et al in U.S. Pat. No. 3,873,644 discloses a method of producing graft polymers from a cyclic olefin to obtain thermoplastic products of high impact strength.
Ofstead in U.S. Pat. Nos. 4,020,254 and 3,935,179 disclose metathesis polymerization of cycloolefins to obtain a rubbery polymer. Streck et al in U.S. Pat. Nos. 3,974,092 and 3,974,094 discloses a catalyst for preparation of polyalkenamers. Each discloses polyalkenamers of low reduced melt viscosity. Percent gel obtained using the system of Streck et al is very low. A typical percent gel is about 2 to 6% with 14 being the highest value disclosed. Wilkes in U.S. Pat. No. 3,084,147 discloses thermalpolymerization of dicyclopentadiene. The thermal polymerization is carried out in a nonpolymerizable solvent at about 500.degree. to 550.degree. F.
Stafford in U.S. Pat. No. 3,446,785 discloses a polymerization of olefins. The polymerization discloses the production of a product which is a viscous liquid polymer or a brittle, semi-solid polymer.
Nutzel et al in U.S. Pat. No. 3,684,787 discloses preparation of polyalkenamers. The polymers can be isolated by pouring the solution of polymer into 3 to 5 times its quantity of a solution of a lower alcohol in which an age resister is dissolved. Alternatively, the solution can be introduced into boiling water and the solvent removed with steam. Mensel states in column 1, line 19 that crosslinked products are of no industrial interest. The polymers obtained have a rubber-like character.
Vergne et al in U.S. Pat. No. 3,557,072 discloses plastomers derived from dimethanooctahydronaphthalene and their method of manufacture. Amorphous polymers are obtained in the form of a hard white mass which is washed with methanol and then ground and dried to a white powder.
Tenney et al and Tenney alone in U.S. Pat. Nos. 4,136,247, 4,136,248, 4,136,249 and 4,178,424 disclose ring-opened cycloolefin polymers and copolymers. These polymer products are thermoplastics which can be thermoformed.
Minchak and Minchak et al respectively in U.S. Pat. Nos. 4,002,815 and 4,380,617 each disclose polymerization of cycloolefins to form polymers which may be isolated by precipitation using an alcohol or by steam or hot water stripping. The polymers produced have inherent viscosities from about 0.1 to about 10 and are greater than 90% soluble in solvent. Viscous cements and plastic polymers solidify in from about 30 minutes to 180 minutes. The reaction is short stopped in less than 2 hours by addition of an alcohol. Minchak in U.S. Pat. No. 4,426,502 discloses bulk polymerization of cycloolefins by reaction injection molding in less than about 2 minutes using an organoammonium molybdate or tungstate catalyst.
DeWitt et al in U.S. Pat. No. 4,418,179 discloses impact modification cycloolefins by polymerization using an organoammonium molybdate or tungstate catalysts in the less than 2 minutes using reaction injection molding.
Oshika et al in the Bulletin of the Chemical Society of Japan, line 41, pages 211-217 (1968) discloses ring opening polymerization of norbornene and its derivatives by MoCl.sub.5, WCl.sub.6 and ReCl.sub.5 catalysts. Dark crude polymer is obtained which is dissolved and reprecipitated with methanol.
U.S. Pat. No. 4,002,815 discloses the use of a metathesiscatalyst system which employs a dialkylaluminum iodide, an alkylaluminum diiodide or a mixture of trialkylaluminum compounds with elemental iodine to produce substantially gel-free copolymers of cyclopentene and dicyclopentadiene.
U.S. Pat. No. 4,069,376 discloses the use of a three component catalyst comprised of a soluble tungsten compound, a dialkylaluminum chloride or alkylaluminum dichloride, and a dialkylaluminum iodide or alkylaluminum diiodide to produce substantially gel-free norbornene-dicyclopentadiene copolymers.
U.S. application Ser. No. 526,835 filed Aug. 26, 1983 and assigned to the same assignee, discloses a cellular crosslinked poly(dicyclopentadiene) which is made with a metathesis-catalyst system. The cellular polymer is made by injecting the catalyst system, which includes an alkylaluminum activator, into a reaction vessel which is preheated, preferably to a temperature from about 100.degree. C. to about 125.degree. C.
Not only is it desirable that the thermoset polymer have high impact strength, but it is also desirable that it be easily synthesized and formed. A reaction injection molding (sometimes hereinafter referred to as RIM) process achieves this second goal by in-mold polymerization. The process involves the mixing of two or more low viscosity reactive streams. The combined streams are then injected into a mold where they quickly set up into a solid infusible mass. For a RIM system to be of use with a particular polymer, certain requirements must be met: (1) the individual streams must be stable and must have a reasonable shelf-life under ambient conditions; (2) it must be possible to mix the streams thoroughly without their setting up in the mixing head; (3) when injected into the mold, the materials must set up to a solid system rapidly; and (4) any additives-fillers, stabilizers, pigments, etc. - must be added before the material sets up. Therefore, the additives selected must not interfere with the polymerization reaction.
Interpenetrating polymer networks (IPNs) are a type of polymer alloy consisting of two (or more) crosslinked polymers. They are more-or-less intimate mixtures of two or more distinct, crosslinked polymer networks held together by permanent entanglements with few, if any covalent bonds between the polymers. The entanglements in IPNs must be of a permanent nature and are made so by self-crosslinking of the two polymers. They are introduced either by swelling a crosslinked polymer with monomer and the crosslinking agent of another polymer, and curing the swollen polymer in situ or by mixing the linear polymer, prepolymers, or monomers in some liquid form solution, or bulk, together with crosslinking agents, evaporating the vehicle (if any), and curing the component polymers simultaneously.
IPNs possess several interesting characteristics in comparison to normal polyblends. Formation of IPNs is the only way to intimately combine crosslinked polymers, the resulting mixture exhibiting (at worst) only limited phase separation. Normal blending or mixing of polymers results in a multiphase morphology due to the well-known thermodynamic incompatibility of polymers. However, if mixing is accomplished simultaneously with crosslinking, phase separation may be kinetically controlled by permanent interlocking of entangled chains.
Molecular and supramolecular perspectives are believed to be important in considering interpenetrating networks. On linked polymer networks intermeshed through molecular chain segment entanglements. These are totally non-separable without chain breaking (i.e. degradation). A semi-interpenetrating network (SIPN) then is a crosslinked network having a non-crosslinked polymer dispersed through it on a molecular scale. These in theory are separable without bond breaking. Neither the interpenetrating network nor the SIPN represents a heterophase polymer structure in a morphological or supramolecular sense.
The supramolecular scale microscopically observable heterophases are present SIPN and IPN. In this context an interpenetrating network is any system of two polymers where the supramolecular structure involves two intermeshed continuous polymer phases irrespective of whether or not they are crosslinked.
Because molecular mixing of dissimilar uncrosslinked polymers is thermodynamically unfavorable (for entropic reasons) it is unusual to form a stable, molecular IPN from two uncrosslinked polymers. They generally will separate into a heterophase polymer system which might or might not be a supramolecular IPN.
The forming of supramolecular interpenetrating networks of two uncrosslinked polymers is called polymer blends. "Co-reacted" polymers is a process which results in block copolymers and sometimes results in heterophase polymer systems which could exhibit supramolecular IPN morphology, depending on block length.