Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1990-08-02
1992-11-10
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524291, 524321, 524417, 524433, 524437, C08K 322, C08K 336, C08K 509, C08L 6106
Patent
active
051624036
DESCRIPTION:
BRIEF SUMMARY
The invention relates to phenol resin pre-moulding materials (intermediates) having a controlled B-stage, which cure under the influence of heat and, advantageously, under pressure, and also to a process for their preparation.
Pre-moulding materials of phenol resins having a long-term adjustable B-stage characteristic, optionally with reagents, additives and adjuvants, which are characterised in that they contain hydraulic binders and/or their components as well as an agent for reducing alkalinity and optionally the content of free metal ions, are a particular object of this invention.
Duroplast pre-moulding materials have long been known. They are moulding material primers in the B-stage, which are more or less stable moulding materials comprising thickened reactive mixtures of the moulding material starting components. They generally comprise few volatile components, and can be worked directly to finished parts, for example by pressmolding. They are prepared as compounds of prematrix and reinforcing material. The prematrix (paste) principally comprises reaction or condensation resin and reagents, for example hardener, catalyst, thickener, optionally in admixture with additives such as fillers, pigments, plasticisers and adjuvants, e.g. internal release agents, lubricants, wetting agents. The reinforcing material conventionally comprises fibrous structures, for example cut glass fibers. The thickening or maturation or rather the attainment of the corresponding B-stage follows relatively quickly, and is usually conducted thermally. The resultant material is pseudo-stable, and its applicability is limited. The storage of such products is associated with further, but slower continuation of the thickening. The pre-moulding materials become drier and harder. Longer storage at room temperature can lead, for example, to extensive hardening. BMC-amorphous pre-moulding materials, prepeg cloth pre-moulding materials and SMC (sheet moulding compounds)-mats pre-moulding materials serve as examples.
The B-stage of such pre-moulding materials exhibits a stage, in which the prematrix of the pre-moulding material, preferably on the basis of a defined increased molecular weight of its reaction or condensation resin component, exhibits a definite limited rheology and, as the case may be, autohesion.
The reaction- or condensation resins are no longer fluid, in this state. They are however soluble and meltable. The prematrix can be substantially solid. Usually, however, it becomes putty-like to somewhat wax-like, and the pre-moulding material has a kneadable to oil cloth consistency. On hotpressmoulding, such B-stage materials behave in such a manner that their prematrix flows under the influence of heat and pressure, reimpregnates and transports the reinforcing material, conveys eventual gas components, fills the relevant mould space and then gels on reaching the appropriate temperature and cures to a form-giving part of the moulded item. The gelling, at the desired end point of the transport phenomenon of the moulded mass in the implement, is characterised by a formation of local networks which largely change to complete cross-linking on curing.
The B-stage thus exhibits a quantity characteristic of the material state, whose thickening rate, level and stability are of essential importance both for the preparation and workability of the pre-moulding materials and for the quality of the resultant parts. The B-stage determines the handability of the pre-moulding material (important in complex mould tool geometry), affects the density of the relevant laminate moulding stack (significant for intra- and inter-laminar strengths) and is also decisive as regards the possibility of manufacturing moulding stacks for stock (significant in mass production). The B-stage is relevant for the storage stability of the pre-moulding materials and important for their flow properties on compression moulding.
It decisively influences the pressure profile structure over the pre-moulding material mass in the compression moulding process, and has a
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I. T. Fucik, "Phenolic Compounds Especially for SMC with Controlled B-Stage", delivered at the Society of the Plastics Industry 45th Annual Conference in Washington, D.C. on Feb. 15th, 1990.
Abstract published in News Survey, No. 4/92, page 8.
Michl Paul R.
Reichhold Chemie Ges.m.b.H.
Szekely Peter
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