METHOD OF PREVENTING MEASLING WHEN MAKING EPOXY LAMINATES

• US 3,660,199 A
• Filed: 07/24/1969
• Issued: 05/02/1972
• Est. Priority Date: 07/24/1969
• Status: Expired due to Term

• Current Assignee: Harry A. Kreitmayer, Michael Riccitiello
• Original Assignee: Harry A. Kreitmayer, Michael Riccitiello
• Inventors: Riccitiello, Michael, Kreitmayer, Harry A.
• Primary Examiner(s): Quarforth, Carl D.
• Assistant Examiner(s): Lechert, Jr., Stephen J.
• Application Number:
  US04/844,277
• Time in Patent Office: 1,013 Days
• Field of Search: 264/236 156/312,330,311,306,245
• US Class Current: 156/307.1
• CPC Class Codes: B32B 2038/0076 Curing, vulcanising, cross-linking
• CPC Class Codes: B32B 2309/022 Temperature vs pressure profiles
• CPC Class Codes: B32B 37/06 characterised by the heating method
• CPC Class Codes: B32B 37/08 characterised by the cooling method
• CPC Class Codes: B32B 37/10 characterised by the pressing technique, e.g. using action of vacuum or fluid pressure
• CPC Class Codes: C08J 2363/00 Characterised by the use of epoxy resins; Derivatives of epoxy resins
• CPC Class Codes: C08J 5/244 using glass fibres
• CPC Class Codes: C08J 5/249 characterised by the additives used in the prepolymer mixture
• CPC Class Codes: H05K 1/0366 reinforced, e.g. by fibres, fabrics H05K1/036 takes precedence
• CPC Class Codes: H05K 2203/0783 Using solvent, e.g. for cleaning; Regulating solvent content of pastes or coatings for adjusting the viscosity
• CPC Class Codes: H05K 2203/1105 Heating or thermal processing not related to soldering, firing, curing or laminating, e.g. for shaping the substrate or during finish plating
• CPC Class Codes: H05K 3/0011 Working of insulating substrates or insulating layers
• CPC Class Codes: Y10S 428/901 Printed circuit
• CPC Class Codes: Y10T 428/31511 Of epoxy ether

Abstract

Measling, the appearance of spots or stars under the surface of a resin portion of an epoxy-glass fiber laminate, is prevented or significantly diminished by a laminating process which includes curing plies of glass cloth and epoxy resin at an elevated temperature, e.g., 300* to 400* F., at an elevated pressure, e.g., 750 to 1,500 pounds per square inch, until gel formation occurs by reaction of the epoxy resin and curing agent, after which heating is continued at approximately the same temperature but at a lower pressure, e.g., 50 to 400 lbs./sq. in. Suitably, the initial curing step lasts for about 30 to 80 minutes and the subsequent step takes about 20 to 50 minutes, such times varying with the thickness of the laminate, the nature of the expoxy resin, the temperature employed, the geometry of the laminate, the type of reinforcing cloth, the curing apparatus used and the presence or absence of metal molded into the plastic. After completion of heating, the laminate is cooled in the press and is then removed.

Claims

2. A method according to claim 1 wherein the curing is of a plurality of epoxy resin-glass fiber laminae at a pressure over 700 lbs./sq. in. and is conducted over a period of about 30 to 80 minutes and the subsequent heating at a pressure of about 50 to 400 lbs./sq. in. is conducted for about 20 to 50 minutes.

3. A method according to claim 2 wherein the laminate contains at least three laminae and the cooling effected takes place within about 5 to 30 minutes and lowers the temperature of a middle lamina of the laminate to less than 150* F.

4. A method according to claim 3 wherein the epoxy resin is a diglycidyl ether of Bisphenol A, the curing agent is dicyandiamide and the glass sheet is a plain weave of chrome treated fibers.

5. A method according to claim 4 wherein the laminae charged to the press for molding comprise 38 to 43 percent epoxy resin and 57 to 62 percent glass fabric, the curing is at about 1,000 lbs./sq. in., the temperature to which heating is effected is from 330* to 360* F., and the cooling is to a temperature of 125* F. or less.

6. A method according to claim 5 wherein the laminae charged to the press are charged as dry lay-ups of B-stage epoxy resin having a resin flow of about 12 to 16 percent and a volatiles content less than 1 percent.

7. A method according to claim 6 wherein the number of laminae charged to the press is from three to 20 and the thickness of the finished laminate is from about one-sixty-fourth inch to three-thirty-secondths inch.

8. A method according to claim 7 wherein at least one major face of the laminate has molded thereinto a surface metal, which was charged to the press together with the dry lay-ups and was pressed into the curing resin.

9. In a method for manufacturing epoxy resin-glass fiber laminates at a temperature of about 300* to 400* F. in a press, the improvement which results in production of a laminate which is non-measling on heating, which comprises pressing a plurality of laminae of epoxy resin-glass fiber sheets at a pressure over 700 lbs./sq. in. to produce a gel of partially cured resin and then lowering the pressure to 50 to 400 lbs./sq. in. until the resin is completely cured, after which the laminate is cooled, the pressure is reduced to atmospheric and the laminate is removed from the press.