Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-01-27
2001-01-09
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S477000, C524S486000, C524S487000, C524S490000, C524S502000, C526S290000
Reexamination Certificate
active
06172146
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a hot melt composition, and a modified aromatic petroleum resin for hot melt composition used therefor, more specifically, to, for example, a hot melt composition having improved heat stability and adhesion resistance to heat when used as hot melt adhesive, and a modified aromatic petroleum resin for hot melt composition used therefor.
BACKGROUND ART
An example of prior art is disclosed in Japanese Patent Application Laid-open No. Sho 55-65248, which proposes that a modified aromatic petroleum resin obtained by copolymerizing a specific thermal cracked oil fraction having a low indene content and a high vinyltoluene content with a phenol compound and turpentine oil be blended in a hot melt adhesive composition.
This modified aromatic petroleum resin is a preferred petroleum resin for use in hot melt adhesive, with its excellent compatibility with base resins such as ethylene-vinyl acetate copolymer (hereinafter referred to as “EVA”). However, practical adhesive strength in a temperature range above a certain point is not sufficient, partly because commercially available turpentine oil with a low diene value is used, as described in the embodiment of the foregoing laid-open patent application.
During the packaging procedure of liquid products, for example, where they are filled in vessels such as cans or bottles immediately after production while hot, then packaged in containers such as corrugated fiberboard boxes, heat may transfer from the products to the containers. Hot melt adhesive, which gains adhesive strength by solidifying, including the one described in the foregoing laid-open patent application, may easily lose the adhesive strength when exposed to high temperatures. Therefore, the containers need to be allowed to cool for a while until the products become cold enough. This cooling time inevitably prolongs the production time. It is for this reason that improvement in adhesion resistance to heat when applied to substrates, particularly paper substrates such as corrugated fiberboards, is awaited. Improvement in adhesion resistance to heat is generally achieved by increasing the molecular weight of the resin. However, increased molecular weight may sacrifice adhesive properties, especially low temperature adhesion.
An object of the present invention is to improve the adhesion resistance to heat and heat stability of the modified aromatic petroleum resin described in the foregoing laid-open patent application, while maintaining the good hot melt adhesive properties thereof, especially the low temperature adhesion.
DISCLOSURE OF THE INVENTION
The inventors have found, after vigorous studies to improve the modified aromatic hydrocarbon resin described in the foregoing laid-open patent application, that the aforementioned problem can be solved by selecting turpentine oil with a specific diene value and by varying the indene and vinyltoluene contents from those described in the foregoing laid-open patent application.
Thus, the first mode of the present invention relates to a hot melt composition comprising:
(a) an ethylene copolymer resin: 100 weight parts;
(b) a modified aromatic petroleum resin having a weight-average molecular weight in a range of 500 to 2000 and produced by the copolymerization of (1) through (3) below using a Friedel-Crafts catalyst: 50 to 150 weight parts,
(1) a polymerizable component of thermal cracked oil fraction obtained by the thermal cracking of petroleum hydrocarbons, composed primarily of components having boiling points in a range of 140 to 220° C. and containing vinyltoluene at a content of 10% or above and below 60% and indene at a content of 10 to,80%: 100 weight parts,
(2) a turpentine oil having a diene value in a range of 15 to 60 cg/g: 10 to 40 weight parts, and
(3) a phenol compound: 1 to 15 weight parts; and
(c) a wax: 10 to 100 weight parts.
The second mode of the present invention relates to a hot melt composition according to the first mode of the present invention, wherein a conjugated diolefin content in said thermal cracked oil fraction is 2.0% or below.
The third mode of the present invention relates to a hot melt composition according to the first mode of the present invention, wherein said ethylene copolymer resin is ethylene-vinyl acetate copolymer.
The fourth mode of the present invention relates to a modified aromatic petroleum resin for use in a hot melt composition having a weight-average molecular weight in a range of 500 to 2000 and produced by the copolymerization of (1) through (3) below using a Friedel-Crafts catalyst:
(1) a polymerizable component of thermal cracked oil fraction obtained by the thermal cracking of petroleum hydrocarbons, composed primarily of components having boiling points in a range of 140 to 220° C. and containing vinyltoluene at a content of 10% or above and below 60% and indene at a content of 10 to 80%: 100 weight parts,
(2) a turpentine oil having a diene value in the range of 15 to 60 cg/g: 10 to 40 weight parts, and
(3) a phenol compound: 1 to 15 weight parts.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is described in more details below.
Base polymers for use in the hot melt composition according to the present invention may be thermoplastic rubber, such as block SBR (including ones partially hydrogenated), or (a) an ethylene copolymer resin, the latter being preferred. Examples of such (a) an ethylene copolymer resin include ethylene copolymers with one or more polar monomers which can copolymerize with ethylene, such as vinyl acetate or other vinyl esters of monocarboxylic acids, or acrylic or methacrylic acid or their esters with methanol, ethanol or other alcohols.
The desired polar monomer content in the ethylene copolymer resin may be 1 to 60 wt %, preferably 15 to 45 wt %. The melt index, an index to molecular weight, is preferably 10 to 1000 g/10 min (as measured under the conditions of 190° C., 2.16 kg load, 10 minutes). More preferable examples of ethylene copolymer include EVA and ethylene-ethyl acrylate copolymer.
The (b) modified aromatic petroleum resin for use in the present invention is produced from the thermal cracked oil fraction obtained by the thermal cracking of petroleum hydrocarbons, such as crude oil, kerosene, gas oil, naphtha, and butane. The fraction is composed primarily of components having boiling points in a range of 140 to 220° C., and contains vinyltoluene at a content of 10% or above and below 60%, preferably 10% or above and 55% or below, and indene at a content of 10 to 80%, preferably 15 to 80%, and, more preferably, further contains conjugated diolefins at a content of 2.0% or below.
Generally, the thermal cracked oil fraction consists of polymerizable and non-polymerizable components.
The polymerizable components are unsaturated polymerizable components of the thermal cracked oil fraction having boiling points in the above range, and include styrene and alkyl derivatives thereof, such as &agr;-methylstyrene, &bgr;-methylstyrene and vinyltoluene; indene and alkyl derivatives thereof; and cyclopentadiene, methylcyclopentadiene, dicyclopentadiene and alkyl derivatives thereof. These polymerizable components usually account for 10 to 90 wt % of the thermal cracked oil fraction.
The non-polymerizable components account for the remaining portion of the thermal cracked oil fraction and consist primarily of saturated hydrocarbon compounds such as c
9
alkylbenzenes. In the present invention, these non-polymerizable components essentially do not contribute to polymerization, but work mostly as solvents.
In producing petroleum resin, polymerization can be controlled by adding non-polymerizable components consisting of saturated hydrocarbon compounds, such as C
9
alkylbenzenes, to adjust the proportion of the polymerizable components to 40 to 60 wt % (of the total feedstock including turpentine oil, phenol compound, etc.), as appropriate to attain desired viscosity or for other purposes.
Vinyltoluene content (%) herein shall refer to the proportion (wt %) of vinyltoluene to the polymeriza
Egwim Kelechi
Hollander Law Firm, P.L.C.
Nippon Petrochemicals Co. Ltd.
Wu David W.
LandOfFree
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