Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
1998-09-21
2001-09-04
Zirker, Daniel (Department: 1771)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S345000, C428S920000, C428S921000, C522S182000, C525S163000, C525S479000
Reexamination Certificate
active
06284368
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pressure-sensitive flame-retardant adhesive required to have a sufficient adhesive force and also a self fire-extinguishing property for instantaneously extinguishing fire in the fields of fixation of electronic parts, building materials, vehicles, aircraft, ships, etc.; adhesive sheets formed by forming the pressure-sensitive flame-retardant adhesive into, for example, a sheet form or a tape form; and a photopolymerizable composition for obtaining the pressure-sensitive flame-retardant adhesive.
BACKGROUND ART
An acrylic pressure-sensitive adhesive has generally been prepared by solution-polymerizing monomers mainly comprising a (meth)acrylic acid alkyl ester. However, from the restrictions on safety of organic solvents and environmental health, a method of preparing the pressure-sensitive adhesive by emulsion-polymerizing or photo-polymerizing the above-described monomers is recently widely used.
Such a pressure-sensitive adhesive is usually that an acrylic adhesive polymer is crosslinked with a crosslinking agent to increase a cohesive force at high temperature, thereby imparting an excellent heat resistance. However, since many of the adhesive components are constituted of combustible materials, there has been a difficulty that the pressure-sensitive adhesive cannot be used in fields of application requiring a flame-retardance together with a heat resistance.
To overcome this difficulty, JP-A-1-223187 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), for example, discloses a pressure-sensitive flame-retardant adhesive obtained by adding a flame-retardant or a flame-retardant assistant, such as a brominated material, chlorinated paraffin, aluminum hydroxide, antimony trioxide, etc., to a adhesive base polymer such as an acrylic polymer, a synthetic rubber, a natural rubber, etc.
However, it is necessary to add a large amount of a flame-retardant in order to exhibit a sufficient flame retardant effect by such a conventional pressure-sensitive flame-retardant adhesive. In this case, there is a problem that the heat resistance of the pressure-sensitive adhesive is decreased. Further, if the degree of crosslinking of the base polymer, such as a rubber, is increased in order to improve the heat resistance, the adhesive property thereof is decreased, so that it is necessary to add a large amount of a tackifier. In this case, there is a problem that holding power of the adhesive at high temperature is decreased in addition to increase of the cost.
In view of these circumstances, an object of the present invention is to provide an acrylic pressure-sensitive flame-retardant adhesive which has excellent adhesive performances such as adhesive force or holding at high temperature, and also has a self fire-extinguishing property for instantaneously extinguishing fire, that is, a flame-retardance; adhesive sheets obtained by forming the pressure-sensitive flame-retardant adhesive in, for example, a sheet form or a tape form; and a photopolymerizable composition for obtaining the above-described pressure-sensitive flame-retardant adhesive.
DISCLOSURE OF THE INVENTION
As a result of various investigations to attain the above-described object, the present inventors have found that if a photopolymerizable composition comprising a (meth)acrylic acid alkyl ester as a main component and a specific crosslinking agent added thereto together with a photopolymerization initiator, and a specific flame-retardant further compounded therewith is polymerized and cured by irradiation with ultraviolet rays, a pressure-sensitive flame-retardant adhesive having excellent adhesive performances such as adhesive force and holding power at high temperature and also a self fire-extinguishing property for instantaneously extinguishing fire, that is, a flame-retardant property, and the adhesive sheets thereof are obtained, and have accomplished the present invention.
That is, the present invention relates to a photopolymerizable composition comprising following components a) to d);
a) 100 parts by weight of monomer(s) (or an oligomer thereof) comprising 70 to 100% by weight of a (meth)acrylic acid alkyl ester having on the average a carbon number of 2 to 14 in the alkyl group, and 30 to 0% by weight of a monoethylenically unsaturated monomer,
b) 0.02 to 5 parts by weight of a polyfunctional (meth)acrylate as a crosslinking agent,
c) 0.01 to 5 parts by weight of a photopolymerization initiator, and
d) 10 to 180 parts by weight of a flame-retardant having a melting point of at least 60° C.;
a pressure-sensitive frame-retardant adhesive comprising the photopolymerization product of this composition; and adhesive sheets having the layer of the pressure-sensitive flame-retardant adhesive on one surface or both surfaces of a substrate.
In the monomer of the component a) used in the present invention, the (meth)acrylic acid alkyl ester having on the average a carbon number of 2 to 14 in the alkyl group includes ethyl (meth)acrylate, butyl (meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)-acrylate, iso-octyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, and the like. Those can be used alone or as a mixture of two or more kinds of them.
If necessary, together with the (meth)acrylic acid alkyl ester, a monoethylenically unsaturated monomer copolymerizable with the (meth)acrylic acid alkyl ester is used to improve adhesive property, cohesive force, heat resistance, etc. Such a monoethylenically unsaturated monomer includes acrylic acid, itaconic acid, sulfopropyl acrylate, hydroxyalkyl acrylate, cyanoalkyl acrylate, acrylamide, substituted acrylamide, vinylcaprolactam, acrylonitrile, 2-methoxyethyl acrylate, glycyl acrylate, vinyl acetate, etc., and according to the purpose, those are used alone or as a mixture of two or more kinds.
In the monomer of the component a), the use proportion of the (meth)acrylic acid alkyl ester and the monoethylenically unsaturated monomer copolymerizable therewith is that the former is from 70 to 100% by weight, and preferably from 85 to 95% by weight, and the latter is from 30 to 0% by weight, and preferably from 15 to 5% by weight. By using such a use proportion, the adhesive property, the cohesive force, etc., can be balanced well.
The polyfunctional (meth)acrylate as the crosslinking agent which is the component b) used in the present invention functions to increase shear strength of the adhesive. Examples thereof include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, etc.
The amount of this polyfunctional (meth)acrylate used is from 0.02 to 5 parts by weight, and preferably from 0.1 to 3 parts by weight, per 100 parts by weight of the monomer as the component a). Within this range, where a bifunctional (meth)acrylate is used, the amount thereof can be increased, and where a trifunctional or more (meth)acrylate is used, the amount thereof can be decreased. However, when the amount is less than 0.02 part by weight, the degree of crosslinking after the photopolymerization cannot sufficiently be increased and when the amount is larger than 5 parts by weight, there is the possibility of lowering the adhesive force, etc., which are either undesirable.
The photopolymerization initiator as the component c) used in the present invention includes benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, etc; substituted benzoin ethers such as anizoin methyl ether, etc; substituted acetophenones such as 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenoneacetophenone, etc.; substituted &agr;-ketols such as 2-methyl-2-hydroxypropiophenone, etc.; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride, etc.: photoactive oximes such as 1-phenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime, etc.
The photopolymerization initiator is used in an amount of from 0.01 to 5 parts by weight, and preferably from 0.05 to 1 part by
Muta Shigeki
Oura Masahiro
Yoshikawa Takao
Nitto Denko Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
Zirker Daniel
LandOfFree
Photopolymerizable composition, pressure-sensitive... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Photopolymerizable composition, pressure-sensitive..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photopolymerizable composition, pressure-sensitive... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2514579