Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-12-28
2002-01-29
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C428S365000, C428S375000, C428S376000, C428S378000, C526S309000, C570S125000, C570S126000, C570S127000, C570S128000, C570S129000, C570S131000, C570S132000
Reexamination Certificate
active
06342572
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention pertains to benzocyclobutene resins, or more particularly to benzocyclobutene resins having flame retardant and reduced brittleness properties. Such resins have a high glass transition temperature (Tg>250° C.), low moisture absorption, low dielectric constant, good mechanical properties, flame retardancy, and can be cast onto a reinforcement to prepare a laminate for use as a substrate for electronic circuitry.
2. Description of the Related Art
In the manufacture of electronic devices, such as computers, printed circuit boards are widely used to support discrete electronic components and to provide the electrical circuitry between the components. Commercial electronic computers have become more powerful since their introduction, yet they have been reduced in physical dimensions from room size to desk size. As their size has decreased and the number of inter-connections due to more powerful logic has increased, the printed circuit boards used have become denser and more complex. Today's printed circuit boards can be extremely dense, with very small geometry and with many layers.
Printed circuit boards typically have a central core of a dielectric material, such as a composite of fiber glass and a thermosetting resin, for example an epoxy resin, which core has applied on at least one surface a layer of conductive material such as copper. The layer or layers of conductive material are etched or otherwise processed to provide circuits of a predetermined pattern. Individual circuit boards are then laminated to form a multilayer structure having the metal circuitry sandwiched between dielectric layers. A major problem exists in the preparation of printed circuit boards which are flame retardant and non-brittle.
It is known in the art to render thermoplastics fire resistant by adding flame-inhibiting substances to them when they are being prepared. However, such additives to thermoplastics produce side effects in addition to their flame-inhibiting action, which are undesirable because they impair the characteristic properties of the thermoplastics and limit their usefulness. Thus flame inhibiting substances are added in powder form to the thermoplastic and remain in powder form therein or, when they cool after being melted and mixed, separate again as an independent phase. These produce not only the desired flame-inhibiting effect, but also act as fillers which modify the mechanical properties of the thermoplastics, by embrittling them, and reducing their elongation and impact strength. U.S. Pat. No. 4,128,709, which is incorporated herein by reference, has proposed the mixture of certain polymers and copolymers of pentabromobenzyl esters and tetrabromoxylylene diesters to thermoplastics to render them flame retardant. However, such are not taught to be useful for thermosetting compositions. Many flame retardant compounds embrittle thermosetting plastics.
Benzocyclobutene polymers are known as thermosetting polymers having high thermal stability, but they are flammable. The invention reduces the flammability and brittleness of the benzocyclobutene (BCB) resins. These goals are achieved by adding a brominated acrylate, such as pentabromobenzylacrylate monomer (PBA) to the BCB and causing them to react to form a resulting fire-resistant thermoset material. The PBA also reduces the brittleness of the cured material versus pure, cured BCB by reducing the crosslinking density. An important difference between this invention and prior art is that addition of the PBA imparts fire resistance to a previously flammable BCB based material. There have been other reports of fire resistant materials containing BCB, but all those reported are cases where a fire resistant polymer had minor amounts of BCB as attached end groups. According to this invention, a material where the bulk is a flammable BCB-based resin has been rendered flame retardant by a reactive additive. The PBA, is unique in that it reacts with the BCB to create a homogeneous system. In addition, the PBA reduces the brittleness of cured BCB while imparting flame retardancy. The resin resulting from curing of PBA and BCB has a unique combination of high glass transition temperature (Tg>250° C.), low moisture absorption, low dielectric constant, good mechanical properties, flame retardancy (meeting or exceeding UL94 V-0 and/or VTM-0 requirements), and can be cast onto a reinforcement to prepare a printed circuit board. Other resins have been reported with high glass transition temperatures, but these typically absorb more moisture than the resin described herein or are not flame retardant or both.
SUMMARY OF THE INVENTION
The invention provides a flame resistant compound which comprises the reaction product of
a) a halogen containing compound of the formulae
R&Parenopenst; DA)
n
or
R&Parenopenst; DA&Parenclosest;
n
R
2
wherein R is a halogen containing aromatic group, a halogen containing aliphatic group or a combination thereof; R
2
is hydrogen, an aromatic group, an aliphatic group or a combination of an aromatic group and an aliphatic group which may contain halogen atoms; DA is a Diels-Alder reactive diene or a group that can act as a dienophile in a Diels-Alder reaction; and n is greater than or equal to 1; with
b) a benzocyclobutene compound.
The invention also provides an article which comprises a substrate, and a flame resistant compound applied to the substrate; which flame resistant compound which comprises the reaction product of
a) a halogen containing compound of the formulae
R&Parenopenst; DA)
n
or
R&Parenopenst; DA&Parenclosest;
n
R
2
wherein R is a halogen containing aromatic group, a halogen containing aliphatic group or a combination thereof; R
2
is hydrogen, an aromatic group, an aliphatic group or a combination of an aromatic group and an aliphatic group which may contain halogen atoms; DA is a Diels-Alder reactive diene or a group that can act as a dienophile in a Diels-Alder reaction; and n is greater than or equal to 1; with
b) a benzocyclobutene compound.
The invention further provides a process for preparing a laminate article which comprises
i) forming a flame resistant compound which comprises the reaction product of
a) a halogen containing compound of the formulae
R&Parenopenst; DA)
n
or
R&Parenopenst; DA&Parenclosest;
n
R
2
wherein R is a halogen containing aromatic group, a halogen containing aliphatic group or a combination thereof; R
2
is hydrogen, an aromatic group, an aliphatic group or a combination of an aromatic group and an aliphatic group which may contain halogen atoms; DA is a Diels-Alder reactive diene or a group that can act as a dienophile in a Diels-Alder reaction; and n is greater than or equal to 1; with
b) a benzocyclobutene compound;
ii) coating the flame resistant compound onto a substrate;
iii) heating the coated substrate at a sufficient pressure and at a sufficient temperature for a sufficient time to cure the flame resistant compound.
This invention fills the need for a resin that has a high glass transition temperature, low moisture absorption, low dielectric constant, good mechanical properties, flame retardancy, and can be cast onto a reinforcement to prepare a laminate for use as a substrate for electronic circuitry. Such can also be used for packaging materials.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The composition of the invention comprises a flame resistant compound which is the reaction product of
a) a halogen containing compound of the formulae
R&Parenopenst; DA)
n
or
R&Parenopenst; DA&Parenclosest;
n
R
2
wherein R is a halogen containing aromatic group, a halogen containing aliphatic group or a combination thereof; R
2
is hydrogen, an aromatic group, an aliphatic group or an combination of an aromatic group and an aliphatic group which may contain halogen atoms; DA is a Diels-Alder reactive diene or a group that can act as a dienophile in a Diels-Alder reaction; and n is greater than or equal to 1; with
b) a benzocyclobutene compound.
In one
McCarthy Thomas F.
Wagaman Michael W.
Brueske Curtis B.
Cain Edward J.
Honeywell International , Inc.
LandOfFree
Flame retardant benzocyclobutene resin with reduced brittleness does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flame retardant benzocyclobutene resin with reduced brittleness, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flame retardant benzocyclobutene resin with reduced brittleness will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2843997