Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-04-30
2001-08-07
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S038000, C525S192000, C525S193000, C525S194000
Reexamination Certificate
active
06271288
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a polyolefin resin composition containing an esterified cellulose material and useful for forming a shaped article, especially, an odd-shaped article, by extrusion. The present invention is also directed to a raw material composition for the above polyolefin resin composition.
Because of cheapness, woody materials such as wood meal have been mixed with a thermoplastic resin for the production of molded plates or tubes. In such a technique, fluidity of the mixture is the most important concern. Thus, a lot of proposals have been made to improve the fluidity of a thermoplastic resin composition containing a woody material. Such a composition, however, is usable only for the production of shaped articles having a simple contour, such as rods, but is ill-suited for the production of odd-shaped articles, namely articles having a relatively complicated contour, such as L-shaped plates, because of poor melt tension thereof.
JP-A-H9-316248 discloses a composition containing a polyolefin resin, an esterified cellulose or lignocellulose and an organic peroxide compound. JP-A-H9-316248 teaches that a polypropylene resin used as the polyolefin resin decomposes by reaction with the organic peroxide compound during kneading to cause reduction of the molecular weight thereof. As a result, the melt tension of the kneaded composition is lowered. JP-A-H9-316248 thus proposes to incorporate a liquid cross-linking agent or a low melting point cross-linking agent to prevent the reduction of the molecular weight of the polymer and to improve the melt tension of the kneaded composition.
SUMMARY OF THE INVENTION
It has now been found that the use of a liquid cross-linking agent or a low melting point cross-linking agent causes problems not only because the production costs increase but also because the cross-linking agent is not compatible with a polyolefin resin.
It is, therefore, an object of the present invention to provide an inexpensive polyolefin resin composition containing a woody material suitable for the production of an odd-shaped article by extrusion.
Another object of the present invention is to provide a polyolefin resin composition of the above-mentioned type which has a high melt tension and good shape retentivity when extruded through a die.
It is a further object of the present invention to provide a raw material composition for the above polyolefin resin composition, which does not contain a cross-linking agent and which is devoid of the drawbacks of the above-described known composition.
In accomplishing the foregoing objects, there is provided in accordance with the present invention a polyolefin resin composition obtained by kneading a raw material composition containing a polypropylene resin, a polyethylene resin, an esterified woody material and an organic peroxide compound, wherein the weight ratio of the polypropylene resin to the polyethylene resin ranges from 30:70 to 80:20.
The esterified woody material may be an esterified cellulose material obtained by esterifying a cellulose material with a polybasic acid anhydride and having a content of the polybasic acid anhydride bonded thereto of 0.5-20% based on the weight of the cellulose material. The weight ratio of a total of the polypropylene resin and polyethylene resin to the cellulose material ranges from 30:70 to 70:30. The organic peroxide compound is used in an amount of 0.001 to 0.1% based on a total weight of the polypropylene resin, polyethylene resin and cellulose material. The cellulose material may be selected from cellulose, modified cellulose, lignocellulose and modified lignocellulose.
The polyolefin resin composition is obtained by kneading the above raw material composition at 150-200° C. for 0.5 to 30 minutes. Though not wishing to be bound by the theory, it is considered that, during the kneading, the organic peroxide is decomposed with the simultaneous breakage of main chains of the polyolefin resins and the formation of cross-linkages. The kneaded composition, namely the polyolefin resin composition, may be pelletized. Thus, in one preferred embodiment, the polyolefin resin composition according to the present invention is in the form of pellets which are ready for use in extrusion molding for the formation of molded articles having any desired shape or contour.
Other objects, features and advantages of the present invention will become apparent from the detailed description of the preferred embodiments of the invention to follow.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION
The raw material composition for the polyolefin resin composition according to the present invention contains the following ingredients (a)-(d):
(a) a polypropylene resin;
(b) a polyethylene resin;
(c) an esterified cellulose material; and
(d) an organic peroxide compound.
As the polypropylene resin (a), a polypropylene homopolymer or a propylene copolymer such as a propylene-&agr;-olefin random or block copolymer may be used. The propylene copolymer preferably contains at least 50 molar % of propylene. Illustrative of &agr;-olefins are ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene. The above polypropylene resins may be used in combination of two or more thereof. The use of a propylene homopolymer or a propylene-ethylene block copolymer is particularly preferred for the purpose of the present invention.
The polypropylene resin (a) preferably has a melt flow rate (MFR in accordance with ASTM D1238) of 0.1 to 10 g/10 minutes, more preferably 0.5-5 g/10 minutes, at a temperature of 230° C. and a load of 2.16 kg and a melt tension of at least 5 g at 190° C.
As the polyethylene resin (b), a polyethylene homopolymer such as a low density polyethylene or a high density polyethylene or an ethylene copolymer such as an ethylene-&agr;-olefin copolymer may be used. The ethylene copolymer preferably contains more than 50 molar % of ethylene. Illustrative of &agr;-olefins are 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene. The use of a high density polyethylene is particularly preferred for the purpose of the present invention.
The polyethylene resin (b) preferably has a melt flow rate of 0.01 to 1.0 g/10 minutes, more preferably 0.01-0.5 g/10 minutes, most preferably 0.01-0.3 g/10 minutes, at a temperature of 190° C. and a load of 2.16 kg and a melt tension of at least 15 g at 190° C.
The weight ratio of the above ingredient (a) to ingredient (b) ranges from 30:70 to 80:20, preferably 40:60 to 70:30. A weight ratio (a) to (b) above 80:20 causes chain degradation of the polypropylene resin (a) so that the melt tension of the polyolefin resin composition decreases and, hence, it is difficult to prepare an odd-shaped molded article by extrusion. On the other hand, too small a weight ratio (a) to (b) below 30:70 causes the formation of excessive cross-linking so that a high load should be applied to an extruder and, hence, it is difficult to smoothly perform extrusion of the polyolefin resin composition.
The esterified cellulose material (c) is obtained by esterifying a cellulose material with a polybasic acid anhydride and has a content of the polybasic acid anhydride bonded thereto of 0.5-20%, preferably 1-10%, based on the weight of the cellulose material.
The cellulose material may be selected from cellulose, modified cellulose, lignocellulose and modified lignocellulose. Any cellulose, lignocellulose or derivatives thereof customarily used as a filler for a resin composition may be suitably used for the purpose of the present invention. Illustrative of suitable cellulose materials are wood meal and wood fiber.
The polybasic acid anhydride to be used for the esterification of the cellulose material may be, for example, maleic anhydride, phthalic anhydride, succinic anhydride, tetrahydrophthalic anhydride, itaconic anhydride and adipic anhydride. Above all, the use of maleic anhydride, phthalic anhydride or succinic anhydride is preferred for reasons of their availability at low costs. The above polybasic acid anhydrides may be
Matsuda Hideaki
Matsumoto Yutaka
Ueda Minoru
Yamaguchi Yuki
Lorusso & Loud
Okura Industrial Co., Ltd.
Rajguru U. K.
Seidleck James J.
LandOfFree
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