Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2001-11-16
2003-08-19
Zirker, Daniel (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S3550AC, C428S921000
Reexamination Certificate
active
06607827
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a flame-retardant pressure-sensitive adhesive composition having excellent tackiness and flame retardancy, a flame-retardant pressure-sensitive adhesive tape using the composition and an electronic part or a transformer utilizing the tape.
BACKGROUND OF THE INVENTION
Electrical insulating pressure-sensitive adhesive tapes are usually employed for layer and outer insulation of a transformer. These electrical-insulating pressure-sensitive adhesive tapes are required to have not only adhesive strength and electrical insulating property but also high flame retardancy for ensuring safety. In recent years, they are requested to satisfy the UL 510 FR standards which are UL standards for an electrical insulating tape used for electronic parts.
In order to impart this electrical-insulating pressure-sensitive adhesive tape with flame retardancy, decabromodiphenyl oxide, a halogen-based flame-retardant, was conventionally employed. This flame-retardant was able to impart the tape with flame retardancy without lowering adhesive properties. Since regulations on the material has been severer in Europe owing to environmental problems, its use was limited and instead of it, tetrabromobisphenol A or a derivative thereof, tribromophenol or ethylenebispentabromobiphenyl has come to be used.
SUMMARY OF THE INVENTION
The single use of these flame retardants is however accompanied with the problems such as deterioration in adhesive properties and insufficient flame retardancy and there is accordingly a demand for their improvement.
With a view to overcoming the above-described problems, the present invention has been made. It has been found that an acrylic flame-retardant pressure-sensitive adhesive composition having both excellent adhesive properties and flame retardancy is available by adding, to (D) an acrylic polymer, (A) ethylenebispentabromobiphenyl, (B) a brominated bisphenol and (C) antimony trioxide as flame-retardants at a specific ratio, leading to the completion of the present invention.
In one aspect of the invention, there is thus provided a flame-retardant pressure-sensitive adhesive composition, which comprises, as flame-retardants, (A) ethylenebispentabromobiphenyl, (B) a brominated bisphenol and (C) antimony trioxide and, as a base polymer, (D) an acrylic polymer, said flame-retardant components (A), (B) and (C), in terms of weight ratio, satisfying the following conditions:
2≦[(
A
)+(
B
)]/(
C
)≦6
and
(
B
)≦(
A
),
and said [(A)+(B)] being added in an amount of from 30 to 90 parts by weight and said (B) being added in an amount of 15 parts by weight or greater, each based on 100 parts by weight of the base polymer (D).
In another aspect of the invention, there is also provided a flame-retardant pressure-sensitive adhesive tape which comprises a base material having provided at least on one side thereof the above-described flame-retardant pressure-sensitive adhesive composition and satisfies the flame retardancy of the UL-510 FR standards. In a further aspect of the present invention, there is also provided a flame-retardant pressure-sensitive adhesive tape having adhesive strength, as measured in accordance with the UL-510 FR standards, of 3.325 N/19 mm or greater, particularly a flame-retardant pressure-sensitive adhesive tape employed for electrical insulation of electronic parts or a transformer.
In a still further aspect of the invention, there is also provided electronic parts or a transformer having the above-described flame-retardant pressure-sensitive adhesive tape adhered thereto.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is characterized in that to an acrylic polymer (D), ethylenebispentabromobiphenyl (A), a brominated bisphenol (B) and antimony trioxide (C) which are flame-retardants are added as essential components. The ethylenebispentabromobiphenyl (A) has high flame retardancy but tends to lower adhesive properties, while the brominated bisphenol (B) exhibits low flame retardancy but is highly effective for improving adhesive properties. This means that single use of ethylenebispentabromobiphenyl (A) imparts a tape with excellent flame retardancy but owing to low adhesive properties, flagging occurs at the end portion of the tape, while single use of the brominated bisphenol (B) enables exhibition of adhesive properties but lowers flame retardancy.
Antimony trioxide is known as an assistant flame retardant for improving flame retardancy of a brominated type flame retardant such as ethylenebispentabromobiphenyl (A). If it is not used in combination, a flame retardant must be used much, which is causative of lowering in adhesive properties. In the invention, adhesion and flame retardancy can be attained simultaneously by mixing the above-described three components at a specific ratio.
In the invention, ethylenebispentabromobisphenyl (A), a brominated bisphenol (B) and antimony trioxide (C) are added so as to satisfy, in terms of weight ratio, the following equations:
2≦[(
A
)+(
B
)]/(
C
)≦6,
preferably
3≦[(
A
)+(
B
)]/(
C
)≦4,
and
(
B
)≦(
A
),
and to adjust the amount of the [(A)+(B)] to 30 to 90 parts by weight, particularly 50 to 70 parts by weight and the amount of (B) to 15 parts by weight or greater, preferably 20 parts by weight or greater, each based on 100 parts by weight of the base polymer (D).
The amount of antimony trioxide (C) less than the ⅙ of the amount [(A)+(B)] of ethylenebispentabromobiphenyl (A) and brominated bisphenol (B) lowers flame retarding effect, while its amount greater than the ½ adversely affects adhesive properties, becoming a cause for flagging from the end portion of adhesion.
When the amount of the brominated bisphenol (B) is greater than that of ethylenebispentabromobiphenyl (A), the pressure-sensitive adhesive layer transfers to the back side of a tape upon rewinding of a pressure-sensitive adhesive tape (particularly, rewinding under low temperatures), by which the tape becomes unusable.
In the invention, amount [(A)+(B)] of ethylenebispentabromobiphenyl (A) and the brominated bisphenol (B) exceeding 90 parts by weight based on 100 parts by weight of the base polymer (D) cause lowering in adhesive properties, becoming a cause for flagging at the end portion of adhesion. At an amount of [(A)+(B)] not greater than 30 parts by weight, on the other hand, flame-retarding performance cannot be exhibited. At this time, when the amount of the brominated bisphenol (B) is less than 15 parts by weight, adhesive properties are not satisfactory. The brominated bisphenol (B) must therefore be added in an amount of 15 parts by weight or greater.
Ethylenebispentabromobiphenyl (A) to be used in the invention is commercially available and “SAYTEX8010”, product of Albemarle Corporation can be used for example. Examples of the brominated bisphenol include brominated bisphenol A and brominated bisphenol S having 1 to 8 bromine atoms bonded to the benzene ring of a bisphenol A residue and a bisphenol S residue, respectively. Specific examples include monobromobisphenol A, dibromobisphenol A tribromobisphenol A, tetrabromobisphenol A, pentabromobisphenol A, hexabromobisphenol A, octabromobisphenol A, tetrabromobisphenol A bis(2-hydroxyethyl ether), tetrabromobisphenol A bis (2-bromoethyl ether), tetrabromobisphenol A bis(1,2-dibromoethyl ether), tetrabromobisphenol A bis(propyl ether), tetrabromobisphenol A bis(3-bromopropyl ether), tetrabromobisphenol A bis(2,3-dibromopropyl ether), monobromobisphenol S, dibromobisphenol S, tribromobisphenol S, tetrabromobisphenol S, pentabromobisphenol S, hexabromobisphenol S, octabromobisphenol S, tetrabromobisphenol S bis(2-hydroxyethyl ether), tetrabromobisphenol S bis (2-bromoethyl ether), tetrabromobisphenol S bis(l,2-dibromoethyl ether), tetrabromobisphenol S bis (propyl ether), tetrabromobisphenol S bis (3-bromopropyl ether), tetrabromobisphenol S bis (2,3-dibromopropyl ether) and
Chang Victor S
Nitto Denko Corporation
Sughrue & Mion, PLLC
Zirker Daniel
LandOfFree
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