Two-stage mat forming preforming and molding process
First Claim
1. A method of making a preform comprising the steps of:
- (a) mixing a two-stage binder including a first binder constituent which has a photoinitiator responsive to visible light to generate free radicals which cross link and provide a viscosity sufficient to hold glass fibers together and a second binder constituent which has a cationic-type second photoinitiator responsive to ultraviolet light to generate electrons for cross linking and rendering the binder rigid;
(b) applying the two-stage binder to a mat of glass fiber reinforcement material to coat glass fibers of the mat without filling interstices among the glass fibers;
(c) exposing the two-stage binder to visible light to partially polymerize the binder such that it has a viscosity sufficient to hold the glass fibers together for subsequent handling;
(d) placing the partially polymerized binder-coated mat into a preform mold which is transparent to ultraviolet radiation;
(e) pressing the mat into a desired shape; and
(f) exposing the pressed mat to ultraviolet radiation through the mold to activate the second photoinitiator and produce a rigid three-dimensional preform.
1 Assignment
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Accused Products
Abstract
Glass fiber mats are made for subsequent use in preforming for an RTM or SRIM molding process, for example, such that the binder applied to the mat has two distinct curing stages. In the first stage, a partial cure is provided by visible light upon a free radical generation in response to a photoinitiator mixed in the binder in an exact ratio to give a predictable increase in viscosity to that of a semi-solid so that the fibers are sufficiently bound for subsequent handling, but not sufficient to complete a cure, while leaving a second stage ready for a final cure which is achieved by the use of a cationic-type second photoinitiator which is sensitive to ultraviolet light. During the second curing stage, the mat is formed into a three-dimensional shape of a desired end product and cured with ultraviolet radiation while still in the mold, to obtain a rigid three-dimensional preform structure.
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Citations
9 Claims
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1. A method of making a preform comprising the steps of:
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(a) mixing a two-stage binder including a first binder constituent which has a photoinitiator responsive to visible light to generate free radicals which cross link and provide a viscosity sufficient to hold glass fibers together and a second binder constituent which has a cationic-type second photoinitiator responsive to ultraviolet light to generate electrons for cross linking and rendering the binder rigid; (b) applying the two-stage binder to a mat of glass fiber reinforcement material to coat glass fibers of the mat without filling interstices among the glass fibers; (c) exposing the two-stage binder to visible light to partially polymerize the binder such that it has a viscosity sufficient to hold the glass fibers together for subsequent handling; (d) placing the partially polymerized binder-coated mat into a preform mold which is transparent to ultraviolet radiation; (e) pressing the mat into a desired shape; and (f) exposing the pressed mat to ultraviolet radiation through the mold to activate the second photoinitiator and produce a rigid three-dimensional preform. - View Dependent Claims (2, 3, 4, 5)
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6. A method of making a three-dimensional preform, comprising the steps:
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(a) applying a coating of a two-stage binder to a mat of glass fibers to coat the fibers without filling interstices among the fibers, with a binder comprising a first constituent including a first photoinitiator which is responsive to visible light to produce free cross-linking radicals to provide a partial cure for the binder in which the binder has a viscosity sufficient to hold the glass fibers together, and be plastic and deformable, and a second constituent including a cationic-type second photoinitiator which is responsive to ultraviolet radiation to cure by producing cross-linking electrons so that the binder becomes rigid; (b) exposing the binder-coated mat to visible light to activate the first photoinitiator of the first constituent; (c) placing the binder-coated mat in an ultraviolet-transparent mold having a desired size and shape of the three-dimensional preform to be made; (d) pressing the mat in the mold into the desired size and shape of the preform to be formed; (e) exposing the pressed mat to ultraviolet radiation through the mold to activate the second photoinitiator of the second constituent to form a rigid preform; and (f) removing the rigid preform from the mold. - View Dependent Claims (7, 8, 9)
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Specification