Size Composition

This invention relates to a size composition, coated glass fibers and reinforced thermoplastics. These sizes are particularly useful for reinforcing polyamide resins (nylons).

Numerous thermoplastic materials are available including polyolefins, polyacetals, polyamides (nylons), polycarbonates, polystyrenes, styrene-acrylonitrile copolymers, acrylonitrile-butadiene styrene (ABS) copolymers and polyvinyl chloride (PVC). Thermoplastic resin and glass fibers are made into useful shapes by means of heat and pressure. Processes include injection of hot resin into a mold, extrusion and pultrusion. Other processes include hot calendaring, casting, vacuum forming and the like. Chopped glass fibers feed into these processes to strengthen and stiffen the resulting composite.

The invention includes a size consisting essentially of:

a polyurethane/isocyanate emulsion containing blocked isocyanates;

a homopolymer of acrylic acid monomer;

one or more amino organo-silane coupling agents; and

water.

In the preferred embodiment, we also add polyvinyl pyrrolidone (PVP) for better strand integrity, size stability and fuzz reduction.

The resulting coated glass fibers yield desirable reinforced thermoplastics. We have found an especially surprising effect on the processability of the reinforcements without any sacrifice in mechanical properties for reinforced nylon in the case of aging in a water/ethylene glycol medium.

The glass size composition of the present invention is useful with filamentous glass which is well known to those skilled in the art. Various types of glass filaments, such as "E" glass and other known types of glass, can be sized with the size. The size is useful on glass filaments having a wide range of diameters and can be used on glass filaments whether or not they are gathered into fibers, ropes, rovings, yarns and the like.

Various polyurethane dispersions which are useful in the present invention include aqueous emulsions of blocked polyurethane resins such as aqueous solutions of polyurethane polymers formed by a reaction between an organic isocyanate or polyisocyanate and an organic polyhydroxylated compound or hydroxyl terminated polyether or polyester polymer. The polyurethane dispersion may contain a crosslinking group.

Other suitable examples include chain extended thermoplastic polyurethanes derived from chain extension of an isocyanate-terminated prepolymer prepared by the reaction of an aliphatic or cycloaliphatic diisocyanate with a polyalkylene ether polyol. A suitable polyurethane emulsion is Rucothane latex having a trade designation of 2011L available from Ruco Chemical Corp. from New York. This material along with other Rucothane polyurethane lattices are thermoplastic polyurethane lattices comprised of high molecular weight aliphatic isocyanate-based thermoplastic elastomers in a water dispersion with an anionic or nonionic surfactant, where the dispersion or latex has varying particle sizes. The lattices typically have a polymer solids content ranging from around 55 to 65 percent by weight where the urethane polymer has an ester backbone.

Other suitable polyurethane dispersions include:

The preferred polyurethane is Baxenden 199-76X.

One suitable polyurethane crosslinking agent dispersion is an anionic aliphatic low branched polyester based polyurethane emulsion containing caprolactam blocked isocyanate which enables the polyurethane polymer to be cured at a temperature exceeding about 150.degree. C. The polyurethane/crosslinking agent system has a milky white appearance having a percent solids of 60, an anionic particle charge of pH at 25.degree. C. of 8.0, and a viscosity at 25.degree. Brookfield RVT of 150 cps. Specifically, one suitable polyurethane crosslinking agent dispersion comprises an aqueous dispersion of a high molecular weight branched polyurethane polymer based on polyester polyol and 1,1-methylenebis(isocycanatocyclohexane) wherein some of the polymer chains are terminated with blocked isocyanate groups. Other suitable polyurethane crosslinking agent dispersions comprise polyurethane/isocyanate emulsions of an aliphatic polyurethane containing blocked isocyanate having a milky white appearance, a percent solids of 40, a pH at 25.degree. C. of approximately 8-9, and a viscosity at 25.degree. C. Brookfield RVT of approximately 200-250 cps. Other suitable polyurethane crosslinking agent dispersions comprise a polyurethane and a trimer of 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate ("isophorone diisocyanate" or "IPDI") blocked with butanone oxime.

Other blocking groups like phenols, cresols .SIGMA.-caprolactam, malonates, aceto acetates, sodium bisulfite also may be used.

The acrylic acid monomer has the formula: ##STR1## wherein X is a hydrogen atom or a methyl or an alkyl group having 1 to 10 carbon atoms. Preferably, the acrylic acid monomer has the formula: ##STR2##

The salt of the polyacrylic acid may be that of alkalimetal or ammonium salts either derived from ammonium hydroxide or from any organic primary, secondary or tertiary amine poly- or monofunctionalized, e.g. triethylamine, triethanolamine, glycine, dimethylaminoethylmethacrylate. Degree of neutralization of the polyacrylic acid may vary from about 20% to 90%. Below 20%, the shelf life of the polyacrylic acid silane mixture is too short and does not present industrial interest. Preferred salts are those from ammonium hydroxide with a degree of neutralization of about 40%. Generally the ammonium hydroxide is added to the polyacrylic acid aqueous solution in order to reach a pH of about 5 or higher if it is necessary to adjust the pH of the polyacid solution with the pH of the polyurethane dispersion.

Some commercially available polyacrylic acid homopolymers that have been evaluated successfully are now given as example:

Particularly suitable organo-silane coupling agent includes amino silanes such as gamma-aminopropyltriethoxysilane, available as A-1100 from Union Carbide. In various embodiments, the coupling agent can optionally further include additional, conventionally known aminosilanes such as gamma-methacryloxypropyltri-methoxy silane and/or a diamino silane such as N-beta-(aminomethyl)-gamma-amino propyltrimethoxysilane and triamino silanes.

The aqueous sizing compositions of the invention can be prepared following generally accepted mixing practices. These sizing compositions can be applied to the glass fiber using any convenient method. The amount of aqueous sizing composition applied is not narrowly critical, but is preferably controlled so as to deposit on the glass fibers a size coating comprising the dried residue of the aqueous: sizing composition of the invention in an amount from about 0.25 to about 2 percent of the weight of the glass, taking into account the dilution of the non-volatile components in the aqueous sizing composition and the usual mechanical loss of some of the aqueous composition initially applied to the fibers before it is dried.

The aqueous sizing composition can be applied to the glass fibers drawing the fibers over a roll, pad, or other suitable surface wet or flooded with the aqueous sizing composition, by spraying, by dipping, or by any other suitable means. The overall concentration of the non-volatile components in the aqueous sizing composition can be adjusted over a wide range according to the means of application to be employed, the character of the glass fibers to be sized, e.g., their diameter and composition, and the weight of dried size coating desired for the intended use of the sized fibers.

The sized glass fibers of the invention can be incorporated into the curable matrix resin which is to be reinforced thereby in the final cured resinous article as either monofilament or multi-filament strand, as either long, essentially continuous, elements or short chopped pieces, depending upon the shape and method of fabrication of the article to be formed. The sized glass fibers of this invention are particularly adapted for use in the form of chopped glass fibers. Principal among such reinforcements are glass fibers which generally have diameters of about 0.0025 to 0.0075 inch and lengths of about 0.13 to about 2.00 inch.

Generally, the size composition has the following composition in parts per 100 parts of solids:

Preferably, the size composition ranges has the following formulation:

The addition of a base to the size is primarily for pH control. The amount of base employed is sufficient to impart to the size a pH of 3 or higher. However, the quantity of base may be increased to impart to the size a pH within the size from about 5 to about 11.

The classical additives of the sizing art may be added to the formulation when necessary like:

antioxydant

processing aids

humidity regulator

surfactants to help PU dispersion

dispersion stabilizer

antistatic

lubricants

stabilizers

optical brightener

discolorant

etc. . .

The lubricant may be any normally liquid or solid lubricating material suitable for the purpose. Such materials include vegetable and mineral oils, waxes or various types and certain materials which also have utility as surfactants, such as fatty acid monoesters of polyalkylenegylcols.

Surfactants that aid dispersion are ethoxylated fatty acids or di-acids, an ethoxylated nonylphenol, and an ethoxylated octylphenol.

Polyvinyl pyrrolidone (PVP) also may be present for better processing, i.e., strand integrity, size stability and fuzz reduction.

Our preferred size composition has the following formation:

The size is efficient on glass fibers from 0.1 to 1.2 LOI.

The aqueous solution has a solids content of 6.3 weight percent and a pH of 5-5.5. The size was applied to individual glass fibers by conventional application methods and at rates such that the strand solids, on drying, amounted to about 0.8% weight percent.

Glass fibers comprising standard length chopped glass fibers having an average length of about 0.125 inches and from about 0.00035-0.00039 inch fiber diameter were produced from the strands.

The present formulation allows for excellent processability of the sized fibers, i.e., we observed excellent strand integrity, size stability and fuzz reduction over standard products for reinforcing nylon resins.

Sized chopped glass fibers of Example I were compared to standard products. We tested reinforcements from Example I and standard products under hydrolysis pressure at 120.degree. C. We carried out the tests in a medium of 50/50 water/ethylene glycol mixture. Mechanical properties such as tensile strength, tensile elongation, tensile modulus, charpy unnotched impact strength for the products of Example I were essentially the same as for the standard products.