Patent GB-1174943-A (GB)
Title: Reinforced Polypropylene
IPC: C03C25/30
Filed: 1967-01-09
Abstract: 1,174,943. Coating. HERCULES Inc. 9 Jan., 1967 [7 Jan., 1966], No.1155/67. Headings B2E and B2K. [Also in Divisions B5, C3 and Dl] An inorganic fibre-reinforced propylene polymer moulding composition comprises an inorganic fibre reinforcing phase and a crystalline polypropylene matrix phase, the fibres being coated with the product obtained by reacting a silane having at least one substituent reactive with the inorganic fibrous material and at least one acid reactive organic substituent with a "modified polypropylene" comprising a material made by grafting an alpha, beta, ethylenically unsaturated acid or acid anhydride onto a crystalline polypropylene. The inorganic fibres may comprise glass or asbestos. The crystalline propylene polymer may be isotactic or stereo regular or a crystalline copolymer of propylene with e.g. ethylene, block copolymers. The polypropylene may be grafted with maleic, fumaric, itaconic, citraconic, acrylic, methacrylic, crotonic, isocrotonic, mesaconic, angelic acid, and anhydrides. The modified polypropylene is prepared by treating the polymer to produce on the chain active sites at which the modifying compound can anchor through its double bend. Such active centres can be induced by subjecting the polymer to high energy ionising radiations or by contacting the polymer with a free radical producing material such as peroxide. Substituents reactive with the inorganic fibres in the silane may be hydroxyl, alkoxyl and halide groups. Acid reactive substituents can be e.g. epoxy, hydroxyl, amino, hydroxylalkyl isocyanato, mercapto. Examples of such compounds are given. The inorganic fibres may be first treated with the silane and thereafter the silane modified polypropylene is formed in situ, or the two components may be first pre-reacted and then applied to the fibres. The fibres can be used as fibres or as woven fabrics, rovings. For compression moulding powder short fibres can be employed mixed into the polymer powder. A composition for vacuum forming may comprise a laminate consisting of a plurality of alternating plies of fabric and crystalline film. Compositions suitable for compression moulding on injection moulding can be prepared by applying the polymer directly to a sized glass roving and thereafter reducing the coated roving to moulding powder size. The coating can be applied by drawing the roving through a solution or melt of the propylene, or by extrusion. In another embodiment the modified polypropylene can be melt blended with the unmodified polypropylene and the glass treated with the specified silane incorporated into the mixture so that the reaction between the silane and the acid modified polypropylene takes place in situ. Glass rovings coated with the silane-modified polypropylene exhibit improved know strength, lubricity and abrasion resistance. In Examples (1-4) glass fabric sections were heated cleaned at 750‹F and then dipped into a 1% aqueous solution of γ-glycidoxypropyltrimethoxy silane and dried. The treated glass fabrics were then immersed in hot, 1 % solutions of polypropylene grafted with maleic anhydride and dried. Laminates were prepared by alternating squares cut from the fabric with crystalline polypropylene fibre in a picture frame mould. Thirteen plies of the fibre were used with 12 plies of the fabric, all of the fabric being in the interior of the structure. The structure was heated under pressure to produce a laminate. Examples 5-8 also relate to the production of similar laminates. In Example 10, 50 parts asbestos were dispersed in 500 parts water, the pH adjusted to 6-7 with acetic acid, and 4g. y-glycidoxypropyltrimethoxy silane. 200 parts acetone and 400 parts methylene chloride were added to break the suspension, the slurry vacuum filtered, and one-half of the paste mixed with 600 parts xylene, 5 parts of a dispersing agent were added, the suspension stirred and heated to 90‹C. and 5 parts of crystalline polypropylene grafted with maleic anhydride added. After 1 hour at 90‹C, 20 parts unmodified crystalline polypropylene were added and the slurry cooled. The precipitate was dried and compression moulded into sheets.