GB1339444A - Production of laminar articles - Google Patents

Abstract

1339444 Injection moulding IMPERIAL CHEMICAL INDUSTRIES Ltd 22 Nov 1971 [30 Nov 1970] 48711/71 Divided out of 1339443 Heading B5A Articles having dissimilar skin and core materials are formed by injecting skin material (A) or skin material followed by core material (B) through a first sprue channel, e.g. 1, and injecting skin material (A) and/or core material (C) through at least two sprue channels, e.g. 2, 6, displaced from the first channel, core material (C) or skin material followed by core material (B) being injected through at least one of the sprue channels so that core material is injected to within skin material already injected into the mould cavity. Embodiments having three and five sprue channels are described. If three sprue channels are used, eight alternatives exist i.e. A, A, C; A,C,C; B,A,A; B,A,C; B,C,C; B,B,A; B, B, C; and B, B, B. If skin material is injected through two channels, the materials, e.g. 9, 10, may be injected simultaneously or sequentially and may be different, e.g. additives such as pigments may vary. Skin material need not be injected through both channels before core material is injected through the third channel. Core material, e.g. 3, may be injected during or after injection of skin material. If core material is injected through two sprue channels, the materials may be injected simultaneously or sequentially and may be different (e.g. 8, 10, Fig. 6). Core material injected through one channel may extend skin material already present in the cavity to below another channel so that core material may then be injected therethrough, e.g. (Fig. 5). The core material which may be foamed may be the same as the skin material except for additives which may be different or which may be the same but present in different proportions. The core materials may become integral or remain separated by skin material (Fig. 6). Additional skin material may be injected after injection of core material to reduce surface exposure of core material (Fig. 9). More skin material than is desired in the moulded article may be injected with the excess material being forced back through the respective channel by the injection of core material (see Specification 1,339,445). Examples of moulds, plastics materials and articles produced are as disclosed in parent Specification 1,339,443.