Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-02-23
2001-11-06
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S515000, C524S528000, C428S304400, C428S513000
Reexamination Certificate
active
06313226
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polyolefin resin composition suitable for use in the forming of flexible sheets, a foamed resin sheet manufactured therefrom, and a wall paper using such sheet. More specifically, the present invention is concerned with a resin composition having excellent roll processability and flexibility, a foamed resin sheet rollings manufactured therefrom, and a wall paper using such sheet.
2. Description of the Background
Wall papers have such structure that a foamed synthetic resin sheet is laminated onto one side of the paper substrate. Up to the present, sheets made of polyvinyl chloride resin have been used mainly for such foamed synthetic resin sheet. Polyvinyl chloride resin sheets have been evaluated highly and utilized because of their good moldability, fire-retardant property and excellent workability. However, there is a growing trend for polyvinyl chloride resin sheets to be gradually replaced by substitute materials on account of concerns about environmental problem due to their own combustion gases and the effects of the plasticizer contained in them on human health.
From a viewpoint of environmental and health concerns, polyolefin resins are safe materials involving little concerns about environmental problem and effects on health. On the other hand, it has been pointed out that polyolefin resins do not show satisfactory sheet formability on calendering rolls, exhibit a low expansion ratio in the processing of foaming, provide sheets having the surfaces giving a different feel from that of the conventional polyvinyl chloride sheets, and have disadvantages to be improved such as the laminates with paper tending to curl.
In this respect, the selection of an ethylene/&agr;-olefin copolymer from among polyolefin resins allows foamed sheets having excellent flexibility and foamability to be obtained. However, as the resin does not feed well between the calendering rolls, the resin shows poor high-speed processability and has disadvantages to be improved such as formed sheets exhibiting a decline in the accuracy in their thickness.
On the other hand, the Japanese Laid Open Patent Publication No.17724/1998 discloses a wall paper using a sheet with excellent calendering roll processability and foamability which uses a particular ethylene/&agr;-olefin copolymer. However, the sheet shows high impact resilience and difficulty in cutting because of its rubber elasticity and therefore does not always display satisfactory workability. It follows therefore that as things stand now, even if any type of polyolefin resin is selected, sheets having excellent moldability and physical properties cannot be obtained.
SUMMARY OF THE INVENTION
Accordingly it is an object of the present invention to provide an olefin resin composition which makes high-speed sheet formation possible because of a reduction tack to the rolls and enable high-expansion-ratio sheet having of high accuracy in thickness and excellent workability to be formed.
Another object of the present invention is to provide a foamed resin sheet obtained from the olefin resin composition and a wall paper using the foamed resin sheet.
Other and further objects, features and advantages of the present invention will appear more fully from the following descriptions.
The present invention relates to an olefinic resin composition comprising olefinic resins which have the following physical properties described in (a) through (e) below:
(a) A density is 0.870 to 0.890 (g/cm
3
).
(b) A melt flow rate as measured at 190° C. and under a load of 2.16 kg is 2 to 10 (g/10 min).
(c) A &Dgr; tan &dgr; at 120° C. is 0.5 to 1.30, wherein, &Dgr; tan &dgr; is an absolute value of a difference between ln(tan &dgr;) at 1 (rad/sec) and ln(tan &dgr;) at 100 (rad/sec).
(d) A tan &dgr; as measured at 120° C. and 10 (rad/sec) is 0.3 to 2.0.
(e) A melt tension at 150° C. is 25 to 200 mN.
Furthermore, the present invention relates to an olefinic resin composition comprising components (A), (B) and (C) which meet the above requirements (a) through (e). Wherein, a component (A) is a polyethylene which has a density of 0.900 to 0.925 (g/cm), a melt flow rate of 0.5 to 30 (g/10 min) and an ethylene unit content of not less than 95 mol %; a component (B) is an ethylene/&agr;-olefin copolymer which has a density of 0.855 to 0.880 (g/cm
3
), a melt flow rate of 0.1 to 10 (g/10 min), a crystallinity of not more than 30% as measured by X-ray diffractometry, and an ethylene unit content of 70 to 95 mol %; and a component (C) is an ethylene/&agr;-olefin copolymer which has a density of 0.855 to 0.880 (g/cm
3
), a melt flow rate of 20 to 200 (g/10 min), a crystallinity of not more than 30% as measured by X-ray diffractometry, and an ethylene unit content of 70 to 95 mol %, or a propylene/&agr;-olefin copolymer having a propylene unit content of 50 to 90 mol %.
Especially, the component composition ratio of the olefinic resin composition of the invention is preferably 5 to 40 wt % for the component (A), 10 to 90 wt % for the component (B), and 5 to 60 wt % for the component (C), wherein a total amount of (A), (B) and (C) is 100 wt %. A fire-retardant sheet can be obtained by compounding 50 to 200 parts by weight of a fire retardant to 100 parts by weight of the olefinic resin composition.
Moreover, the present invention relates to a foamed resin sheet formed from the resin composition. A laminate of the foamed resin sheet with a paper substrate may be utilized satisfactorily as a wall paper.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Next, a specific explanation of the present invention is given step by step.
Physical Properties of the Olefinic Resin Composition
The olefinic resin composition of the invention is prepared from olefinic resins as the principal component. The resin composition shows an outstanding performance in moldability and use with respect to calendering processability, extrudability, foamability and workability, and provides sheets showing excellent physical properties with the accuracy in thickness and feel, if the values of the density, the melt flow rate, the viscoelastic properties as represented by &Dgr; tan &dgr; and tan &dgr;, and the melt tension of the resin composition are so controlled that they fall within the specified ranges as described below.
(a) When the density as measured on the basis of ASTM D-1505 is in a range of 0.870 to 0.890 (g/cm
3
), the tack of the formed sheet to the rolls declines, and its laminate with the paper substrate does not readily curl.
(b) When the melt flow rate as measured at 1 90° C. and under a load of 2.16 kg on the basis of ASTM D-1238 is in a range of 2 to 10 (g/10 min), the resin feeds well between a pair of rolls at the time of the processing of calendering, and it is possible to reduce the exothermic value by shear force in the extruder at the time of extrusion to a low level, avoiding a sharp rise in the resin temperature. Consequently, it is possible to form a sheet without involving the decomposition of the foaming agent in the extruder at the time of foam extrusion.
(c) The &Dgr; tan &dgr; is the absolute value of the difference between tan &dgr; at 1 (rad/sec) and tan &dgr; at 100 (rad/sec), calculating by the following formula, as measured at a strain of 2% and a temperature of 120° C. using a dynamic viscoelasticity testing device (rheometer) and a disc-shaped test specimen 2 mm in thickness and 25 mm in diameter:
ln(tan &dgr;
1 rad/sec
)−ln(tan &dgr;
100 rad/sec
)
When this value is in a range of 0.5 to 1.30, the feed of the resin between the calendering rolls becomes satisfactory. In this case, the tan &dgr; value is a physical property value called loss tangent, which is an index representing dynamic elastic properties. Specifically, tan &dgr; can be expressed by the ratio of loss elastic modulus G″ to storage elastic modulus G′. That is,
G″/G′=tan &dgr;
(d) When the tan &dgr; value as measured under the conditions of 120° C. and 10 (rad/sec) is in a range of 0.3 t
Sueda Takanori
Yasaka Naoto
Mitsui Chemicals Inc.
Yoon Tae H.
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