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
2000-06-26
2002-09-17
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S241000, C526S346000, C526S347000
Reexamination Certificate
active
06451917
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a styrene-based resin material, precisely to a styrene-based resin material of which the product of MI and the melt tension (MT) is not smaller than a specific value, more precisely to the material of a styrene-based resin composition that contains a styrenic polymer essentially having a syndiotactic structure.
BACKGROUND ART
Styrenic polymers essentially having a syndiotactic structure (these are hereinafter referred to as “syndiotactic polystyrenes” or simply as “SPS”) are known as resins having various excellent properties of heat resistance, oil resistance, etc. Having the advantages of such excellent properties, they are tried for many applications to wrapping and packaging films for edibles, to release sheets, etc., for which SPS is laminated with a resin film of polyethylene, polypropylene or with paper, etc.
For producing the laminates, employable is a method of sticking the substrates together with an adhesive, or a method of co-extruding the constituent resins. However, using an adhesive leads to the increase in the production costs, while the co-extrusion method could not apply to lamination with paper. In addition, in co-extruding different types of polymers, the viscosity of the polymers must be suitably controlled. Anyhow, these methods have such problems. Therefore, it is desired to establish an effective method of co-extrusion lamination for SPS.
In the method of co-extrusion lamination, however, the resins to be processed are required to have high-speed moldability, and the film layers formed are desired to be thin. To meet the requirements, the resins must indispensably have the properties of high-speed casting stability and good spreadability. The high-speed casting stability is meant to indicate that, even when a resin is cast at a high speed, the machine-direction edges (MD edges) of the resin film are all the time kept stable with no fluctuation in the width and the thickness of the film, and therefore the production loss is reduced. On the other hand, the spreadability is meant to indicate that the resin being molded is easy to spread.
None of conventional SPS and its resin compositions could satisfactorily meet the requirements of high-speed casting stability and spreadability. In this connection, it has heretofore been known that the melt index (hereinafter referred to as MI) and the melt tension (hereinafter referred to as MT) of resins have some influences on these properties thereof. Some resins with high MI could have good spreadability but their high-speed castability is often poor; while some others with low MI are not good as their high-speed castability and spreadability are both poor. MI and MT are said to have a negative correlation with each other, and resin materials having both good MI and good MT are unknown at present.
Regarding polyolefins, those having long-chain branches and having high MI are known to have good high-speed casting stability, and they are now in practical use. For improving the high-speed casting stability of SPS, therefore, it will be effective to blend SPS having high MI with polyolefins having long-chain branches and having high MI. However, SPS basically differs from polyolefins in their rheological characteristics. Therefore, merely adding polyolefins having long-chain branches and having high MI to SPS would be ineffective for attaining the intended object. Up to this point, no one could succeed in realizing SPS resin materials having both good high-speed castability and good spreadability.
Given that situation, we, the inventors have made the present invention, of which the object is to provide a styrene resin material, especially a styrene-based resin composition having good high-speed castability and good spreadability and favorable to extrusion molding lines.
DISCLOSURE OF THE INVENTION
We, the present inventors have assiduously studied and, as a result, have found that a styrene-based resin material of which the product of MI and the melt tension (MT) is not smaller than a specific value, more precisely a styrene-based resin composition containing SPS and satisfying the requirement has good high-speed castability and good spreadability, and is therefore favorable to extrusion molding lines. On the basis of this finding, we have completed the present invention.
Specifically, the invention is to provide a styrene-based resin material described below.
(1) A styrene-based resin material, of which the product of the melt index (MI, g/10 min) measured at 300° C. and under 2.16 kg, and the melt tension (MT, g) measured at 290° C., through an orifice having a diameter of 2.095 mm, at a cylinder outlet speed of 6.2×10
2
mm/min and at a take-up speed of 4.7×10
4
mm/min, is at least 20.
(2) The styrene-based resin material of above (1), which is a styrene-based resin composition comprising (A) from 35 to 95% by weight of a styrenic polymer, (B) from 5 to 50% by weight of an olefinic polymer, and (C) from 0 to 15% by weight (including 0) of a compound miscible with or having affinity for the component (A) and the component (B).
(3) The styrene-based resin material of above (1), which is a styrene-based resin composition comprising (A) from 35 to 95% by weight of a styrenic polymer of which the melt index (MI, g/10 min) at 300° C. and under 1.2 kg is at least 8 and which essentially has a syndiotactic structure, (B) from 5 to 50% by weight of a polyethylene-based resin, of which <1> the melt tension (MT, g) measured at 290° C., through an orifice having a diameter of 2.095 mm, at a cylinder outlet speed of 6.2×10
2
mm/min and at a take-up speed of 4.7×10
4
mm/min, falls between 0.3 and 10 and <2> the melt index (MI, g/10 min) at 190° C. and under 2.16 kg falls between 0.1 and 10, and (C) from 0 to 15% by weight (including 0) of a styrene-olefin copolymer having a styrene content of from 40 to 85% by weight.
(4) The styrene-based resin material of above (2) or (3), wherein the ratio of component (C)/component (B) falls between 0.1 and 0.4 (by weight) in the styrene-based resin composition.
BEST MODES OF CARRYING OUT THE INVENTION
Embodiments of the invention are described hereunder.
1. Styrene-based Resin Material of the Invention:
The styrene-based resin material of the invention is such that the product of its melt index (MI, g/10 min) measured at 300° C. and under 2.16 kg, and its melt tension (MT, g) measured at 290° C., through an orifice having a diameter of 2.095 mm, at a cylinder outlet speed of 6.2×10
2
mm/min and at a take-up speed of 4.7×10
4
mm/min, is at least 20, preferably at least 30.
(1) Melt index (MI, g/10 min):
MI of the resin material is measured according to JIS K7210, at 300° C. and under 2.16 kg.
(2) Melt tension (MT, g):
MT of the resin material is measured at 290° C., through an orifice having a diameter of 2.095 mm, at a cylinder outlet speed of 6.2×10
2
mm/min and at a take-up speed of 4.7×10
4
mm/min, for which, concretely, used is a Toyo Seiki's device, Capillograph 1C.
(3) The product of MT and MI must be at least 20, but is preferably at least 30. If the product is smaller than 20, the width of the cast sheet of the resin material greatly fluctuates and the thickness thereof could not be unified, whereby the productivity of the cast sheet will lower.
2. Concrete Examples of the Material Satisfying the Requirements:
The styrene-based resin material satisfying the requirements is not specifically defined. Concretely, it includes styrene-based resin compositions mentioned below.
One preferred embodiment of the resin material is a styrene-based resin composition comprising (A) from 35 to 95% by weight of a styrenic polymer, (B) from 5 to 50% by weight of an olefinic polymer, and (C) from 0 to 15% by weight (including 0) of a compound miscible with or having affinity for the component (A) and the component (B). More preferably, the resin composition comprises (A) from 35 to 95% by weight of a styrenic polymer of which the melt index (MI, g/10 min) at 300° C. and under 1.2 kg
Funaki Keisuke
Kogure Masami
Uchida Takaaki
Idemitsu Petrochemical Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Teskin Fred
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