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
2001-11-13
2004-01-06
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S064000, C525S069000, C525S070000, C525S071000, C525S087000, C525S088000, C525S09200D, C525S093000, C525S179000, C525S184000, C525S421000, C525S437000, C522S113000, C522S114000, C522S161000
Reexamination Certificate
active
06673867
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a heat-resistant engineering-plastic resin composition and a heat-resistant injection molded product made with the resin composition, such as for a surface mount PCB (printed circuit board) connector featuring high soldering-heat resistance and heat-aging resistance.
BACKGROUND ART
Downsizing and improvement for the performance of electronic devices and parts have brought a high density parts-mounting technology for PCB.
Consequently, not only electronic parts such as semiconductors and capacitors but also peripheral electronic parts such as connectors, which are used for data input and output, have been mounted on PCB. Conventionally, electronic parts were soldered on PCB via through holes. However, these parts mounting process have been increasingly converting to so-called SMT (surface mounting technology) in recent years to realize higher parts mounting density.
If a resin product melts or deforms when it is in contact with flow solder at high temperature, it cannot be applied in practical use. Therefore, in recent years, electronic parts having resin component such as resin substrates or connectors have been increasingly required to have enhanced soldering-heat resistance to keep the original shape without melting or deforming even when they are exposed to flow solder at high temperature.
As for the PCB connectors, polyamide-based plastics such as nylon 6,6 and polyester-based plastics such as polybutyleneterephthalate (PBT) have been used as the housing materials. However, the soldering heat-resistance of these plastics have a limitation of about 240° C. for 10 to 60 sec.
On the other hand, since the soldering-heat resistance of 260° C. for 10 to 60 sec is required in case for a narrow-pitch type or thin-walled type surface-mounted connector, engineers have no choice but to use so-called super engineering plastics such as a liquid crystal polymer (LCP) and polyphenylenesulfide (PPS). However, these super engineering plastics are costly comparing with conventional general-purpose engineering plastics such as nylon 6,6 and PBT. As a result, the price of the connectors increases.
Even if their high cost is tolerated, super engineering plastics are following disadvantageous in the injection molding process:
(a) They require higher temperature for injection molding, and this reduces the life time of the metal mold;
(b) The weld-line strength is low; and
(c) The molded product may have anisotropy in mechanical strength.
Concerning with solder, the tin-lead alloy has been used conventionally for flow or re-flow soldering process. However, worldwide interest on environmental problems in recent years has compelled the intensified study on lead-free solder. As a result, the practical use of lead-free solders has been steadily increasing. However, lead-free solders have higher melting point of about 20° C. or more than conventional tin-lead alloy solder. Therefore, at least 20° C. of increase for soldering temperature cannot be avoided in case for the lead-free solder, and at least 260° C. for 10 to 60 sec of soldering-heat resistance has been required for the housing materials for electronic parts such as PCB connectors.
As mentioned above, conventional common engineering plastics, such as nylon 6,6 and PBT, have a limitation of soldering-heat resistance of 240° C. for 10 to 60 sec. They do not satisfy the requirement for the soldering-heat resistance of 260° C. for 10 to 60 sec. On the other hand, super engineering plastics such as LCP and PPS have the above-described problems of the cost increase and the disadvantages in the injection molding process.
One of the methods to solve these problems is the cross-linking of nylon 6 or PBT using ionizing radiation. However, even when nylon 6 and PBT are irradiated with electron beam or &ggr; ray, if the dose is low, sufficient cross-linking density cannot be obtained. In other words, low-dose irradiation does not satisfy the soldering-heat resistance of 260° C. specification. On the other hand, high-dose irradiation for increasing the cross-linking density causes partial decomposition of nylon 6 and PBT during the irradiation process to deteriorate the mechanical strength of the material after heat aging test.
DISCLOSURE OF THE INVENTION
An aim of the present invention is to offer the low cost heat-resistant engineering-plastic composition and injection molded electronic parts such as PCB connectors which satisfies the soldering-heat resistance of 260° C. for 10 to 60 sec, and has no problems in the injection molding process, and has excellent in heat-aging resistance. By an intensive study on the foregoing problems, the present inventors found that the intended molded product can be obtained by the following process: (a) melt-kneading (a1) an engineering plastic either having or introduced an active site for reacting with a specific functional group and (a2) either an organic compound that has both the said specific functional group and a polymerizing functional group in the same molecule or polyolefin that has the functional group described in (a1) to obtain a engineering-plastic based resin composition, (b) melt-molding of resin composition of (a), and (c) irradiating the melt-molded plastic composition with ionizing radiation. Thus, the present inventors completed the present invention.
A molded product made with a heat-resistant engineering-plastic based resin composition of the present invention can be embodied by the following methods:
{circle around (1)} (a) melt-kneading of (a1) an acid anhydride group introduced styrene based polymer and (a2) an organic compound that has in the same molecule both (a2a) a polymerizing functional group selected from the groups consisting of vinyl group, allyl group, acrylic group, and methacrylic group and (a2b) a functional group selected from the groups consisting of amino group and epoxy group;
(b) molding a resin composition of (a) into a specified shape by a melt-molding method such as an injection molding method; and
(c) cross-linking of the molded parts of (b) by ionizing radiation.
{circle around (2)} (a) melt-kneading of (a1) an oxazoline group introduced styrene based polymer and (a2) an organic compound that has in the same molecule both (a2a) polymerizing functional groups selected from the groups consisting of a vinyl group, allyl group, acrylic group, and methacrylic group and (a2b) functional group selected from the groups consisting of amino group, carboxylic acid group, hydroxyl group, epoxy group, and thiol group;
(b) molding a resin composition of (a) into a specified shape by melt-molding method such as injection molding; and
(c) cross-linking of the molded parts of (b) by ionizing radiation.
{circle around (3)} (a) melt-kneading (a1) a carboxylic acid group introduced styrene based polymer and (a2) an organic compound that has in the same molecule both (a2a) a polymerizing functional group selected from the groups consisting of vinyl group, allyl group, acrylic group, and methacrylic group and (a2b) a functional group selected from the groups consisting of amino group, hydroxyl group, epoxy group, and thiol group;
(b) molding a resin composition of (a) into a specified shape by a melt-molding method such as an injection molding; and
(c) cross-linking of the molded parts of (b) by ionizing radiation.
{circle around (4)} (a) melt-kneading (a1) an acid anhydride group introduced polyphenylene ether and (a2) an organic compound that has in the same molecule both (a2a) a polymerizing functional group selected from the groups consisting of vinyl group, allyl group, acrylic group, and methacrylic group and (a2b) a functional group selected from the groups consisting of amino group and epoxy group;
(b) molding a resin composition of (a) into a specified shape by a melt-molding method such as an injection molding; and
(c) cross-linking of the molded parts of (b) by ionizing radiation.
{circle around (5)} (a) melt-kneading (a1) polybutyleneterephthalate and (a2) an organic compound that has in the same molecule both (a2a) a polymerizing
Hayami Hiroshi
Nishikawa Shinya
Asinovsky Olga
Seidleck James J.
Sumitomo Electric Fine Polymer, Inc.
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