BACKGROUND ART Reaction-injection-molding (RIM) systems have become increasingly important for the production of many commercially useful products such as automobile fascias. However, many of the reactive systems employed to date contain extensive polyurethane linkages which have relatively low heat distortion temperatures and lack the flexural modulus and tensile strength necessary for many applications. The chemistry of these reactive systems involves the use of a polyisocyanate "A side"and a"B side"employing a mixture of compounds containing isocyanate-reactive hydrogens. Those"B side"components generally include one or more hydroxyl-functional polyols. The polyol components react with the isocyanate to form urethane linkages.

More recently, the use of RRIM for interior automotive parts has been investigated. In the wake of ever increasing standards for increasing fuel efficiency, the industry is continuously seeking means to reduce the weight of automotive parts while maintaining necessary functional strength. Accordingly, for interior body parts where flexural modulus, tensile strength, and impact resistance requirements are not as stringent as in exterior body panels, low density RRIM parts have been investigated as alternatives to heavier weight metal, wood fiber, ABS and PP interior parts.

One recent solution for providing low weight, low density rigid RRIM components employing flake glass filler dispersed through a matrix comprising the reaction product of an isocyanate component and a polyol component. The search, however, for low cost materials that have higher flexural strength continues.

DISCLOSURE INVENTION The fiber reinforced polyurethane composition of this invention is a composite of a polyurethane produced by the condensation reaction of at least one isocyanate component and at least one polyol component and a unique blend of fibers. The blend is a mix of small fibers and long fibers. The small fibers of this invention are 1/4 inch in length or shorter.

The long fibers of this invention have a length greater than 1/4 inch.

Preferred short fibers are hammermilled glass fibers or mineral fibers.

Preferred long fibers are chopped glass fibers.

BEST MODE OF CARRYING OUT INVENTION The polyurethane of this invention varies widely. Generally, it is a thermoplastic polymer produced by the condensation reaction of a polyisocyanate and a hydroxyl-containing material, e. g., a polyol derived from propylene oxide or trichlorobutylene oxide. The basic polymer unit is formed as follows: R, NCO + R20H-R, NHCOOR2' The organic polyisocyanates which may be employed for the"A side"component include aromatic, aliphatic, and cycloaliphatic polyisocyanates and combinations thereof. Representative of these types are the diisocyanates such as m-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, cyclohexane-1,4-diisocyanate, hexahydrotoluene diisocyanate (and isomers), naphthalene-1,5-diisocyanate, 1-methoxyphenyl-2,4-

diisocyanate, 2,2'-, 2,4'-, and 4,4'-diphenylmethane diisocyanate, 4, 4'- biphenylene diisocyanate, 3,3'-dimethoxy-4,4'-biphenyl diisocyanate, and thetriisocyanatessuch as 4,4', 4"-triphenylmethane triisocyanate, and toluene 2,4,6- triisocyanate; and the tetraisocyanates such as 4,4'- dimethyidiphenylmethane and polymericpolyisocyanates such as polymethylene polyphenylene polyisocyanate. Especially useful due to their availability and properties <BR> <BR> <BR> <BR> are4, 4'-diphenylmethanediisocyanateand polymethylenepolyphenylene<BR> <BR> <BR> <BR> <BR> <BR> <BR> polyisocyanate.

Preferably used are the easily accessible, optionally uretonimine- carbodiimide and urethane group-containing aromatic di-and polyisocyanates such as 2,2'-, 2,4'-, 4,4'-diphenylmethane diisocyanate (MDI), as well as any desired mixtures of these isomers, and mixtures of 2,2'-, 2,4% 4,4'-diphenylmethane diisocyanate and polyphenyl polymethylene polyisocyanates (crude MDI). Preferably, used is a uretonimine-carbodiimide-modified 4, 4'-MDI composition containing from 10 weight percent to 40 weight percent modified MDI and 60 weight percent to 90 weight percent 4,4'-MDI, optionally containing less than 10 weight percent 2,2'- and 2,4'-MDI, the weight percentages based on the weight of the uretoniminecarbodiimide-modified 4,4'-MDI composition. The weight ratio of uretonimine to carbodiimide ranges from 20: 1 to 1: 1.

The B side resin component contains a hydroxy functional polyol.

Examples of the polyol component (b) include an alkylene diol such as ethylene glycol, propylene glycol, polyethylene glycol and polypropylene glycol; and a polyester diol such as an esterification product of an excess amount of an alkylene diol with a dicarboxylic acid or its anhydride.

The unique blend of fibers of this invention is a combination of small fibers and long fibers. The small fibers range in length from lengths

almost too short to measure up to 1/4 inch. Generally, the short fibers have a length ranging from 1/64 inch to 1/4 inch. More specifically, the length of the short fibers range from 1/32 inch to 1/4 inch. Preferably, the length of the short fibers ranges from 1/16 to 1/8 inch. Typically, these fibers have a diameter ranging from 1 to 10 microns. Preferably, the diameter ranges from 2 to 6 microns.

Suitable small fibers for use include glass fibers, preferably milled glass fibers, and other inorganic or organic fibers. Suitable milled glass fibers, for example, can be obtained by hammer milling longer glass fibers. Examples of the inorganic fibers include mineral fibers having the appropriate dimensions. Examples of organic fibers include nylon, aramid, and other such fibers having the appropriate dimensions. The milled glass fibers and mineral fibers are preferred. The composition of the glass fibers are the same as the long fibers herein. The mineral fibers may be naturally occurring fibers such as wollastonite. Man-made mineral fibers are produced according to well-known methods, such as fiberization through a spinning disk fiberizer. Most mineral fibers are produced from raw materials such as iron blast furnace slag, cooper refinery slag, or lead blast furnace slag. These raw materials are readily available, and mineral fibers are therefore generally very economical to use.

The long fibers generally are greater than 1/4 inch in length and may range up to 6 inches in length. Generally, the long fibers range in length from 1/2 inch to 2 inches. While the diameter can vary widely, it generally ranges from 10 to 30 microns. Preferably, the diameter ranges from 10 to 20 microns.

Regarding composition, the long fibers may be glass fibers, mineral fibers or organic fibers with glass fibers being preferred. The preferred glass fibers consist primarily of oxides of silicon, but oxides of other minerals such as magnesium and aluminum are often present in relatively

low concentrations. Glass fibers known as K, L and M filaments are readily available in the industry and fall within this range of dimensions.

A variety of fiber choppers may be used to chop glass fiber rovings to the short or long lengths of this invention. U. S. patent applications Serial No. 09/080,570 and Serial No. 09/080,574, both filed on May 18, 1998 show fiber choppers in greater detail and are herein incorporated by reference.

The amount of small fibers in the composition of this invention ranges from 5 to 20 weight percent based on the weight of the composition. The amount of long fibers in the composition of this invention ranges from 5 to 30 weight percent based on the weight of the composition.

Preferably, the amount of small fibers ranges from 5 to 15 weight percent and more preferably from 5 to 10 weight percent. Preferably, the amount of long fibers ranges from 10 to 20 weight percent. The ratio by weight of small fibers to long fibers generally ranges from 1: 1 to 1: 6 and preferably ranges from 1: 1 to 1: 4.

Methods of manufacturing RRIM moldings are well known in the art. The resin components are mixed and maintained at tank temperatures from 70° F to 95°F, preferably from 85°F to 95°F to reduce the viscosity of the resin. The isocyanate component"A"and the resin component"B"are impingement mixed at pressures around 2,000 psi and injected at about atmospheric pressure into an open mold which is subsequently shut and clamped at or about 150-200 psi into a closed mold. The mold is preheated from 100°F to 180°F, preferably from 130°F to 160°F, more preferably around 145°F and may contain a substrate such as vinyl laid up on a mold surface.

Example The samples of low density RRIM compositions of this invention were made on a Hennecke compression mold. Heated mold halves having the dimensions of a conventional door panel were used.

The four variables chosen to conduct the fractional factorial design experiment were mold temperature, fiber loading, ratio index and density.

TABLE I Mold Temperature, deg. F. 140°F-180°F Composite Density, pcf 0.3 to 0.7 Ratio Index (isocyanate/resin) 1.0 to 1.3 Small Fiber Loading wt. percent 5-10 Chopped Glass Fiber Loading wt. percent 10-20 Material Temperature, deg. F.

Resin 70 to 95 Isocyanate 70 to 95 Throughput, gps 50-300 Mix Pressures, psi Polyol 1500-2200 Isocyanate 1500-2200 Demold Time, seconds 70-100 The examples were run with the following materials.

The Polyol is polyether polyol comprising propylene oxide-ethylene oxide from ICI or Bayer.

Isocyanate A is a blend of isocyanates comprising about 60 weight percent 4,4'-diphenylmethane diisocyanate, 5 weight percent 2,4'- diphenylmethane diisocyanate, and 35 weight percent three-ringed or higher oligonscic polymethylene polyphenylene polyisocyanate.

The long chopped glass fibers were 1/2 inch chopped fibers produced from rovings commercially available from Owens Corning, Inc.

The small fibers were mineral fibers from Dayton Bag and Burlap or NICO Fibers. The mineral fibers were 1/16 inch in length.

Results Flexural modulus 100,000 psi to 200,000 psi at 72°F.

The results shows that the molded composites of this invention have a high flexural modulus. The reinforcements mix in and strays in dispension better may be more environmentally friendly than other reinforcements. We can use fiber amounts ranging from 10-30% by composite loading. The aspect ratios of this product range from 3: 1- 27: 1. The fibers can be used in molded urethane articles varying in density from 0.3-2.0 sp. gv. g/cc can be used with whole glass mats, plus pads (partial mats), chopped fibers and the like.

In addition to these embodiments, persons skilled in the art can see that numerous modifications and changes can be made to the above invention without departing from the intended spirit and scope thereof.