Molding composite composition and method for preparing the same

Abstract: A thermoplastic composite composition comprising a thermoplastic matrix resin, a liquid crystal resin which has a liquid crystal transition temperature higher than a minimum temperature of the matrix resin is to be molded and an ability to be melt-extruded into a fiber in the matrix resin, and a compatible agent for providing an improved bonding power with an interfacing surface between the matrix resin and the liquid crystal resin, within a range possible to prevent the liquid crystal resin into a fiber or fibers having an aspect ratio of less than 3.

Description: The present invention relates to a molding composite composition and a method for preparing the same. Recently, there have been proposed a liquid crystal resin composite for improving a tensile strength of a matrix resin by the liquid crystal resin fibers dispersed therein (see Japanese Patent Tokkaisho 64-90255). The liquid crystal resin composite is prepared by melt-extruding a mixture comprising a thermoplastic resin as a matrix resin mixed with a predetermined amount of the liquid crystal resin having a liquid crystal transition point higher than a minimum formable temperature of the thermoplastic resin. The composite material comes into public attention as a substitute of the conventional fiber reinforced plastic (FRP) composite because of the advantage of the composite material of being easily recycled. Further, there has been found that a reinforcement property is changed according to a fiber formation degree of the liquid crystal resin and the more the fiber formation degree advances, the more the property improves. Therefore, it is proposed that the melt-extruding process of the mixture should be carried out in a manner that the liquid crystal resin fibers result in being formed in the matrix resin with an aspect ratio of 3 or more (see Fig. 2) and the resulting composite is subjected to a drawing treatment. However, such improvement of the property by means of drawing is limited and the drawing treatment makes the resulting composite material into fine fibers, so that it is necessary to gather the fine fibers in order to have a strand diameter suitable for molding as disclosed in Japanese Patent Tokkaihei 4-7634. The major object of the present invention is therefore to provide a resin composite composition containing a third component for improving the properties of the composite product in order to improve the properties by any other method than the above drawing method. As a result of our intensive study, it has been found that the composite function between the matrix resin and the liquid crystal is improved by addition of a compatible agent therebetween. On the basis of the inventive view, the present invention has been completed. Therefore, there is provided a molding composite material having LCR fibers with an aspect ratio of 3 or more, comprising: a thermoplastic matrix resin; a liquid crystal resin having a liquid crystal transition temperature higher than a minimum molding temperature of said matrix resin, and which is present as fibers having an aspect ratio of 3 or more in the matrix; and a compatible agent; wherein the thermoplastic matrix resin is selected from the group comprising ABS resin, polystyrene resin, polycarbonate resin, polyolefin resin and polyphenyleneoxide resin, and the compatible agent is the same selected matrix resin modifed by a compound having an epoxy group and/or an acid anhydride. The liquid crystal resin (hereinafter referred to as LCR) is selected from the thermoplastic resins having a liquid crystal transition temperature higher, preferably by 20°C or more, than the minimum moldable temperature of the matrix resin. Examples may include a thermoplastic liquid crystal polyester and a thermoplastic liquid crystal polyesteramide. Among them, the liquid crystal resins of Trade name VECTRA, ECONOL, ZAIDA and so on are commercially available. The fiber formable range of LCR is depending on the kind and nature of the matrix resin as shown in Fig. 1. For example, in the case of using ABS (Acrylonitrile-Butadiene-Styrene copolymer) resin as the matrix resin, it is used preferably from 30 to 75 weight% based on the weight of the composite; in the case of PC (polycarbonate)/ABS resin, preferably from 3 to 70 weight%; in the case of PC/PBT (Polybutyleneterephthalate) resin, preferably from 2 to 60 weight%, in the case of PPO (polyphenyleneoxide)/ PA6 (nylon), preferably from 3 to 65 weight%; in the case of the modified PPO resin, preferably from 3 to 60 weight%, in the case of polypropylene, preferably from 2 to 70 weight%; in the case of polycarbonate, preferably from 3 to 70 weight%. On the other hand, the compatible agent is selected depending on the kind and nature of the matrix resin. In the case of using ABS resin, polystyrene resin, polycarbonate resin or polyphenyleneoxide resin as the matrix resin, the compatible agent is the same selected matrix resin modified by a compound having an epoxy group and/or an acid anhydride, which examples include EGMA-g-PS, EGMA-g-AS, an acid anhydride modified polystyrene, N-substituted maleimide copolymer. In the case of polyolefin resin, the compatible agent is also preferably selected from matrix resin modified by a compound having an epoxy group and/or an acid anhydride, which examples include EGMA, EGMA-g-olefin. Preferred combination examples are as follows: Matrix resin compatible agent *PC/ABS (TECHNIACE T105) Ethylene-Glycyzylmethacrylate-Acrylonitrile-Styrene Copolymer (MODIPER A4400) *ABS BLENMER CP-30 MODIPER A4400 The compounding ratio of the compatible agent to be added is changed depending on the kind and nature of the matrix resin and the liquid crystal resin. As shown in Fig. 3, the more the compatible agent is added, the more the bonding power on the interfacing surface between the matrix resin and the LCR fiber increases and results in the increased tensile strength caused by the composite function. On the contrary, at the same time, the more the compatible agent is added, the more the surface tension on the interfacing surface between the matrix resin and the LCR fiber decreases and results in the lowered cohesion power of the LCR when melt-extruded because of dispersion stabilization of the LCR in the matrix resin and thus it is difficult to form the LCR into fibers. Therefore, the compatible agent to be added should be limited to the compounding ratio range that can prevent the LCR fibers from having an aspect ratio of 3 or less when melt-extruded, preferably to an amount range that generate a synergetic effect caused by the compatible effect and the fiber forming reinforcement effect. The resin composite composition comprising the thermoplastic matrix resin, the liquid crystal resin having the liquid crystal transition higher than the minimum moldable temperature of the matrix resin and the compatible agent, should be melt-extruded by such a shear rate to form the LCR into the fibers having an aspect ratio of 3 or more. The shear rate is from 3 x 10 2 to 10 5 sec -1 . The compatible agent may be added on the interfacing surface between the matrix resin and the LCR fibers in a following manner. 1) The LCR and the compatible agent are preformed in a suitable shaped material, which is melt-mixed to the matrix resin or the composite material comprising the matrix resin and the LCR. 2) The matrix resin and the compatible agent are preformed in a suitable shaped material, which is melt-mixed to the LCR or the composite material comprising the matrix resin and the LCR. In the course of the present invention, there is provided a method for preparing the liquid crystal resin composite material for molding, which comprises: a step for mixing a LCR composite comprising the matrix resin and the LCR with the compatible agent, or mixing the matrix resin or the LCR composite with a composite comprising the LCR and the compatible agent or a composite comprising the matrix resin and the compatible agent wherein the compounding ratio of the compatible agent is in a range possible to prevent the liquid crystal resin from being formed into a fiber or fibers having an aspect ratio of less than 3; a step for extruding the mixture at a melting temperature above the liquid crystal transition point by the apparent resin shear rate of 3 x 10 2 to 10 5 sec -1 to give the molding composite material having the LCR fibers having an aspect ratio of 3 or more. Further, the resulting strands may be subjected to the drawing treatment after cooling or continuously without cooling after extruding. In this case, the drawing ratio (cross sectional area before drawing/ that after drawing) is preferably from 11 to 120. Thereafter, the strands are cut into a predetermined length and used as a molding material. According to the present invention, the compatible agent which is present at the interface between the matrix resin and the LCR, make the bonding power therebetween increased, which results in the increased composite function while maintaining the aspect of 3 or more. Therefore, according to the present invention, only the extruding formation is possible to give a sufficient fiber reinforcement to the LCR composite product. That is, while the composite function caused by use of only the matrix resin and the LCR can not give the sufficient reinforcement because the LCR fibers are damaged or destroyed on molding, which results in lowering the tensile strength after molding. The molding composite material prepared according to the present invention has a good productability such that the tensile strength is not lowered by the molding, so that the molding composite material according to the present invention is possible to give a product having a superior property than that of the conventional products. These and other objects and features of the present invention will become clear from the following description taken in conjunction with the preferred embodiments thereof with reference to the accompanying drawings throughout which like parts are designated by like reference numerals, and in which: Fig. 1 is a graph showing an effect of the content of the LCR on the state variation of the composite material; Fig. 2 is a graph showing an interaction between the apparent shear rate and the drawing ratio in the respect of the tensile strength; Fig. 3 is a graph showing an interaction between the compatible function and the fiber-forming function in the respect of the reinforcement effect. Example 1. 60 weight parts of PC/ABS (TECHNIACE T105 made by SUMITOMO DOW LTD.) as the matrix resin and 40 weight parts of aromatic polyester (VECTRA made by POLYPLASTICS Co. Ltd.) as the LCR are mixed with ethylene-glycyzylmethacrylate-acrylonitrile-styrene copolymer (MODIPER A4400 made by NIHON YUSHI Co., Ltd.) in the compounding ratio as shown in table 3 and then extruded with drawing by means of a twin screw extruder (made by PLASTIC TECHNOLOGY Co., Ltd.) at the following conditions: screw diameter 30 mm, resin temperature 290°C, screw rotation number 100 rpm., die diameter 2 mm, shear rate 1700 sec -1 . The resulting composite strand of 1,4 mm diameter is cut into 3 mm in length to obtain pellets. Next, the pellets are subjected to an injection molding process by means of Injection Molding Machine (220 ton made by TOSHIBA MACHINE Co., Ltd.) and a die mold for test piece at the molding conditions: resin temperature 250°C, injection pressure 1000 kg/cm 2 . The molded products are subjected to a measuring of the tensile strength which is shown in table 1. Comparing the data with that of the original strand, no lowering of the tensile strength is found. Compounding ratio of the compatible agent (weight parts) 0 5 10 20 40 Tensile Strength (MPa) 63 81 84 69 46 Example 2: 60 weight parts of ABS (KRALASTIC MH made by SUMITOMO DOW Ltd.) as the matrix resin and 40 weight parts of aromatic polyester (VECTRA made by POLYPLASTICS Co. Ltd.) as the LCR are mixed with ethylene-glycyzylmethacrylate-acrylonitrile-styrene copolymer (MODIPER A4400 made by NIHON YUSHI Co., Ltd.) in the compounding ratio as shown in table 2 and then extruded with drawing by means of a twin screw extruder (made by PLASTIC TECHNOLOGY Co., Ltd.) at the following conditions: screw diameter 30 mm, resin temperature 290°C, screw rotation number 150 rpm., die diameter 2 mm, shear rate 2500 sec -1 . The resulting composite strand of 1,4 mm diameter is cut into 3 mm in length to obtain pellets. Next, the pellets are subjected to an injection molding process by means of Injection Molding Machine (220 ton made by TOSHIBA MACHINE Co., Ltd.) and a die mold for test piece at the molding conditions: resin temperature 240°C, injection pressure 1000 kg/cm 2 . The molded products are subjected to a measuring of the tensile strength which is shown in table 2. Comparing the data with that of the strand, no lowering of the tensile strength is found. Compounding ratio of the compatible agent (weight parts) 0 2.5 5 7.5 10 Tensile Strength (MPa) 69 79 70 68 64 Although the present invention has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope or the present invention as defined by the appended claims unless they depart therefrom.

Claims: Molding composite material having LCR fibers with an aspect ratio of 3 or more, comprising: a thermoplastic matrix resin; a liquid crystal resin having a liquid crystal transition temperature higher than a minimum molding temperature of said matrix resin, and which is present as fibers having an aspect ratio of 3 or more in the matrix; and a compatible agent; wherein the thermoplastic matrix resin is selected from the group comprising ABS resin, polystyrene resin, polycarbonate resin, polyolefin resin and polyphenyleneoxide resin, and the compatible agent is the same selected matrix resin modified by a compound having an epoxy group and/or an acid anhydride. A method for preparing a molding composite material according to claim 1, the method comprising the steps of: combining a liquid crystal resin, a thermoplastic matrix resin and a compatible agent, wherein said compatible agent has a compounding ratio sufficient to prevent the liquid crystal resin fiber formed in the following extruding step from having an aspect ratio of less than 3; and extruding the mixture at a melting temperature above the liquid crystal transition point by the apparent shear rate of 3 x 10 2 to 10 5 sec -1 .

Inventors: ADACHI DAISABUROU, OHSUGI MASAKATSU, TOMITA TAKASHI, ADACHI, DAISABUROU, OHSUGI, MASAKATSU, TOMITA, TAKASHI
Applicants: MAZDA MOTOR, MAZDA MOTOR CORPORATION
Application year: 1993
Main classification: C08L101
IPC codes: C08L69, C08L55, C08L67, C08L77, C08L101