Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-02-28
2003-02-18
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S493000, C524S504000, C524S847000, C523S217000
Reexamination Certificate
active
06521693
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a long fiber-reinforced polypropylene resin composition which is suited for producing not only small-sized molded articles but also wide-ranged molded articles from medium-sized ones to large-sized ones and to a molded article obtained from the same. Specifically, it relates to a molded article which is excellent in a mechanical strength obtained particularly when it is molded into a medium-sized to large-sized molded article, particularly a mechanical strength in a direction perpendicular to a flow direction of the resin, and therefore has a small anisotropy in a mechanical strength and which is excellent as well in an impact strength and to a long fiber-reinforced polypropylene resin composition which provides the same.
BACKGROUND ART
A so-called long fiber-reinforced polypropylene resin composition obtained by impregnating a reinforcing continuous fiber bundle with a molten polypropylene resin and then pultruding it to pelletize to a length of 2 to 50 mm provides a molded article which is excellent in a mechanical strength, an impact resistance and a heat resistance and therefore is widely used for uses in car parts, industrial parts and the like.
However, when molding a long fiber-reinforced polypropylene resin composition into medium-sized to large-sized molded articles, the mechanical strength and the impact resistance are still unsatisfactory, and particularly the mechanical strength in a direction perpendicular to a flow direction of the resin is short. Accordingly, the molded articles have a large anisotropy in a strength, and it is the existing state that the uses thereof are restricted.
A composition obtained by impregnating a reinforced fiber bundle with a modified polyolefin blended with an alkaline earth metal compound and then pelletizing it was filed in International Publication WO99/20446 by the present applicants as a long fiber-reinforced polyolefin resin composition providing a molded article which was improved in a mechanical strength. When this composition is molded into small-sized molded articles, the molded articles are improved in a mechanical strength and an impact resistance as compared with those of articles molded from conventional long fiber-reinforced polyolefin resin compositions.
Proposed as a glass fiber-reinforced polyolefin resin composition which is improved in a dispersibility of glass fibers in production and which is less liable to cause breaking of the glass fibers in molding is a glass fiber-reinforced polyolefin resin composition obtained by mixing 10 to 70 parts by weight of pellets which are prepared by blending 100 parts by weight of a mixture comprising 20 to 60% by weight of (A′) a propylene homopolymer and 80 to 40% by weight of glass fibers with 1 to 10 parts by weight of an acid-modified polyolefin having an acid-added amount of 0.1 to 10% by weight and in which a pellet length is 2 to 20 mm and the above glass fiber has substantially the same length as the pellet length with (B) 90 to 30 parts by weight of a propylene-ethylene block copolymer so that the whole amount becomes 100 parts by weight (Japanese Patent Application Laid-Open No. 239286/1993, Japanese Patent Application Laid-Open No. 173329/1995 and Japanese Patent Application Laid-Open No. 237512/1995). When these compositions are molded into small-sized molded articles, the molded articles are improved in a mechanical strength, a durability and an impact resistance as compared with those of articles molded from conventional long fiber-reinforced polyolefin resin compositions.
However, not yet known is a long fiber-reinforced polypropylene resin composition providing a molded article which is excellent in a mechanical strength and an impact resistance even when it is molded into medium-sized to large-sized molded articles and which is improved particularly in a mechanical strength in a direction perpendicular to a flow direction of the resin and therefore has a small anisotropy in a strength. Thus, such composition has been demanded.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a long fiber-reinforced polypropylene resin composition which can solve entirely the inconveniences described above, that is, an anisotropy in a mechanical strength, an impact resistance and a strength even when it is molded into medium-sized to large-sized molded articles and which can suitably be used as well for uses in medium-sized to large-sized molded articles. Another object is to provide a molded article obtained from the same.
Intensive investigations repeated by the present inventors in order to obtain a long fiber-reinforced polypropylene resin composition which can solve entirely the inconveniences described above have resulted in finding that very useful for solving the problems described above is a composition obtained by blending a long fiber-reinforced pellet comprising as a base, a specific modified propylene homopolymer compounded with an alkaline earth metal compound with a specific propylene base block copolymer resin as a diluent, and thus they have completed the present invention.
That is, the present invention comprises structures shown below.
(1) A long fiber-reinforced polypropylene resin composition comprising 40 to 85% by weight of (A) a long fiber-reinforced propylene homopolymer pellet shown below and 15 to 60% by weight of (B) a propylene base block copolymer resin having a melt flow rate (230° C., 21.18 N; hereinafter abbreviated as MFR) of 50 g/10 min or less:
(A): a long fiber-reinforced propylene homopolymer pellet comprising,
(A1): 20 to 64.9% by weight of a modified propylene homopolymer obtained by modifying a propylene homopolymer with unsaturated carboxylic acid or an anhydride thereof or a mixture of the above modified propylene homopolymer and an unmodified propylene homopolymer, wherein the MFR is 60 g/10 min or more,
(A2): 0.1 to 5% by weight of at least one selected from the group consisting of simple substances, hydroxides and oxides of alkaline earth metals, and
(A3): 35 to 75% by weight of glass long fibers having a length of 2 to 50 mm.
(2) The long fiber-reinforced polypropylene resin composition as described in the above item (1), wherein (A1) the modified propylene homopolymer obtained by modifying the propylene homopolymer with the unsaturated carboxylic acid or the anhydride thereof or the mixture of the above modified propylene homopolymer and the unmodified propylene homopolymer has an MFR of 100 g/10 min or more, and (B) the propylene base block copolymer resin has an MFR of 35 g/10 min or less.
(3) The long fiber-reinforced polypropylene resin composition as described in the above item (1) or (2), wherein (B) the propylene base block copolymer is a high rigid propylene-ethylene block copolymer resin comprising a propylene homopolymer part having an isotactic pentad rate of 0.96 or more and an Mw/Mn (Q value) of 6 or less, and a propylene-ethylene copolymer part.
(4) The long fiber-reinforced polypropylene resin composition as described in any of the above items (1) to (3), wherein
(B) the propylene base block copolymer resin contains 0.0001 to 1% by weight of a nucleating agent based on the propylene base block copolymer resin.
(5) A molded article obtained by molding the long fiber-reinforced polypropylene resin composition as described in any of the above items (1) to (4).
(6) The molded article as described in the above item (5), wherein the glass long fibers contained in the molded article originating in the long fiber-reinforced propylene homopolymer pellet have a residual average fiber length of 1 mm or more.
EMBODIMENT OF THE INVENTION
Any of publicly known processes can be employed as a production process for the propylene homopolymer of (A1) described above constituting (A) the long fiber-reinforced polypropylene homopolymer pellet of the present invention, which is modified with unsaturated carboxylic acid or an anhydride thereof, a so-called modified propylene homopolymer. The modified propylene homopolymer can be obtained, for example, by
Atsumi Nobukazu
Kuramochi Hitoshi
Nakai Toshimori
Saito Koichi
Chisso Corporation
Yoon Tae H.
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