Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Coated or impregnated woven – knit – or nonwoven fabric which... – Coating or impregnation intended to function as an adhesive...
Reexamination Certificate
2001-02-20
2004-03-02
Cole, Elizabeth M. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Coated or impregnated woven, knit, or nonwoven fabric which...
Coating or impregnation intended to function as an adhesive...
C442S150000, C442S175000, C442S178000, C442S180000, C442S295000, C442S296000, C428S324000, C428S3550EP, C428S363000, C428S454000, C156S060000, C156S166000, C427S208600
Reexamination Certificate
active
06699804
ABSTRACT:
SUBJECT OF THE INVENTION
The present invention relates to the preparation of a micaceous product preferably in the form of a mica tape comprising a support coated with a solvent-free resin, combined with a mica sheet.
More specifically, the present invention relates to a process for preparing a mica tape which is capable of being impregnated subsequent to the preparation process itself.
The present invention also relates to a novel micaceous product.
TECHNICAL BACKGROUND OF THE INVENTION
The electrical and optionally thermal insulation of copper components of electric engines, such as rods or coils, is achieved by taping up the said parts using micaceous products, more specifically micaceous tapes.
These micaceous tapes are in the form of a support impregnated with a resin, for example an epoxy resin, combined with a mica sheet. This mica sheet may be mica paper, optionally reinforced with a small amount of resin, for example epoxy resin.
Two main families of these tapes exist.
The first family comprises tapes known as “saturated tapes” or “prepregs”, which are tapes manufactured from mica paper that is highly impregnated with a resin of Novolac type and having a glass fabric as support. The resin content is usually between 30% and 40% relative to the total weight of the tape.
During manufacture, the epoxy resin is brought to stage B, i.e. it has already undergone curing. Next, this type of product may be taped around the part to be insulated and will then undergo a heat treatment of about from 160° C. to 180° C.
Document JP-07 149 928 discloses a product in the form of a saturated mica tape manufactured conventionally. It appears that a solvent-free epoxy resin is then used in the second phase of the manufacture, i.e. after taping the tape around the machine, in order to obtain adequate electrical insulation.
Document EP-A-0 735 071 discloses a solvent-free resin composition optionally intended for manufacturing a micaceous tape of saturated type, i.e. a tape which is already totally impregnated and consequently has a relatively high resin content.
Document GB-A-2 083 849 discloses a process for preparing insulating tapes, which consists in impregnating a mica support at room temperature using a solvent-free resin, followed by attachment to a support and heating of the assembly so as to reduce the viscosity of the resin, which will promote the deep impregnation of the mica paper. A tape of “prepreg” type which is hence already highly impregnated will thus again be obtained.
The second family comprises so-called “porous” tapes, which have a relatively low resin content of between about 4% and 10% relative to the total weight of the tape. These tapes are capable of being impregnated subsequent to the process for manufacturing the said tapes and will be subjected, after taping up, to a “VPI (vacuum pressure impregnation)” treatment, which makes it possible in a second phase to carry out an impregnation with a resin which is usually solvent-free. The “VPI” treatment consists in immersing in the impregnation resin the copper parts taped up with the porous mica tape, while applying vacuum in order to remove any infiltrated air; next, the vacuum is broken and a certain pressure is applied for several hours in order to make the post-impregnation resin penetrate into the mica insulant. The prosecution of the entire post-impregnation process and the temperature of the resin are set by the nature of this resin, the thickness of the insulation to be impregnated and the porosity of the mica tape used.
Before taping up, very flexible, non-adhesive dry tapes are obtained, which are distinguished by truly exceptional absorption capacity. They are consequently used for high-voltage machines (of: up to 1000 MVA).
To prepare such tapes of the second family which are considered as capable of being impregnated, the “spraying” technique is known, which consists in spreading and impregnating a mica paper with an epoxy resin in solvent medium and then combining it with a support.
To prepare tapes capable of being impregnated, it is also known practice to use techniques of dusting a solid resin either on a mica sheet or directly onto the support, and then to attach the two components under pressure and heat. In particular, the publication EP-A-0 194 974 discloses a process for preparing thin mica tapes capable of being impregnated and comprising an incorporated accelerator, characterized in that a thin mica sheet is dusted with a powdered varnish free of hardener, next either the side of the thin mica sheet dusted with the varnish is bonded under pressure or heat with a glass fabric or a felt serving as support, or a glass fabric is impregnated with a liquid accelerator or a solution of a liquid or solid accelerator in a low-boiling solvent and the support thus obtained is bonded under pressure and heat with one side of the mica sheet dusted with varnish, and the laminate obtained is then impregnated with a liquid accelerator or a solution of a liquid or solid accelerator in a low-boiling solvent. Another possibility consists in impregnating a mica sheet with a liquid accelerator or a solution of a liquid or solid accelerator in a low-boiling solvent, in next dusting the impregnated mica sheet with a powdered varnish free of hardener, and then either in impregnating a glass fabric with a liquid accelerator or solution of a liquid or solid accelerator in a low-boiling solvent and bonding the support thus obtained under heat and pressure with the side of the thin mica sheet which has been dusted with powdered varnish, or in bonding the felt serving as support under pressure and heat with the side of the thin mica sheet which has been dusted with powdered varnish. However, it is observed that by using this process, the dusting operation with a varnish requires the use of a certain amount of varnish. In particular, the varnish will have a tendency, when it has been dusted onto the support, to pass through the mesh and be found on both faces of the support.
AIMS OF THE INVENTION
The present invention aims to provide a process for manufacturing micaceous products capable of; being impregnated, which requires the use of a low content of resin.
The present invention aims to provide a technique for avoiding the use of solvents for the preparation of micaceous products capable of being impregnated, such as mica tapes of porous type.
The present invention aims also to allow the preparation of such tapes which have increased flexibility while at the same time having sufficient or even increased adhesion properties.
In addition, the present invention aims to provide in the specific case of preparing roiled-up tapes, a process which avoids the problem of bonding between successive turns.
MAIN CHARACTERISTIC ELEMENTS OF THE INVENTION
The present invention relates firstly to a process for preparing a micaceous product capable of being impregnated, which is preferably in the form of a mica tape obtained by combining a support and a mica sheet, characterized in that:
the support or the mica sheet is coated with a resin or an adhesive or alternatively a mixture of solvent-free resins, with the aid of coating cylinders at a working temperature for the coating operation,
the support is combined with the mica sheet, and they are subjected to a pressure and temperature treatment at a second working temperature.
The expression “working temperature of the coating operation” should be understood as meaning the temperature to which the mixture of solvent-free resin is brought in order to be able to coat the support or the mica sheet. This temperature is usually between 40° C. and 200° C. This means that the resin should be in a non-solid form, i.e. in the more or less viscous or liquid form.
The expression “a pressure and temperature treatment” means a treatment at a temperature of between 40° C. and 200° C. for a pressure of between 0 and 20 bar in order to allow attachment of the support to the mica sheet.
Among the possible examples of resin intended for coating which may be mentioned are solvent-free epoxy resins, solvent
Jacques Alain
Mortier Noël
Cole Elizabeth M.
Compagnie Royale Asturienne des Mines SociétéAnonyme
Knobbe Martens Olson & Bear LLP
Pierce Jeremy R.
LandOfFree
Method for making a micaceous product preferably in the form... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for making a micaceous product preferably in the form..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for making a micaceous product preferably in the form... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3280497