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
1999-10-25
2001-07-03
Cain, Edward J. (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...
C524S445000, C524S493000
Reexamination Certificate
active
06255378
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a polyamide resin composition which provides molded articles exhibiting high strength, high modulus, high heat resistance, high toughness, excellent dimensional stability and high tensile elongation with small deviation. This invention also relates to a process for producing said polyamide resin composition.
BACKGROUND OF THE INVENTION
Polyamide resin compositions reinforced with fibrous reinforcing materials such as glass fiber and carbon fiber or inorganic fillers such as calcium carbonate are widely known. However, since these reinforcing materials have poor affinity to polyamide, the reinforced polyamide resin compositions have reduced toughness while mechanical strength and heat resistance are improved. Furthermore, molded articles of a fiber-reinforced polyamide resin composition suffer from appreciable warp. Additionally, in using the inorganic fillers, substantial improvement in mechanical strength or heat resistance cannot be obtained unless they are added in a large quantity.
In order to eliminate these disadvantages of conventional reinforced polyamide resin compositions, a composition comprising polyamide and a layered silicate typified by montmorillonite has been proposed (unexamined published Japanese patents No.62-74957, No.63-230766, No.2-102261, and No.3-7729). In this resin composition, silicate layers are uniformly dispersed in the polyamide resin on the molecular level by introducing polyamide chains into the laminae of a layered silicate. In the case of using montmorillonite for the above purpose, the montmorillonite must be swelled with organic salts (e.g., an ammonium salt of an aminocarboxylic acid, an onium salt) and then isolated, before the monomer or monomers forming the polyamide resin are polymerized.
Meanwhile, the present inventors discovered that polyamide resin compositions having a specific layered silicate (swellable fluoromica mineral) uniformly dispersed therein on the molecular level and exhibiting excellent mechanical strength and heat resistance can be obtained without the above-described inorganic salt treatment. This is achieved by mixing monomer(s) forming polyamide and swellable fluoromica mineral, and polymerizing the above-described monomer(s) usually under a high pressure of over 10 kg/cm
2
(unexamined published Japanese patent No. 6-248176).
Furthermore, the present inventors have proposed a process which comprises mixing monomer(s) forming polyamide, swellable fluoromica mineral, and an acid having pKa of 0~6 or negative (in 25° C. water), and then mixing the above-described monomer(s) (unexamined published Japanese patents No.8-3310 and No.8-134205). Because this process does not necessarily require high pressure during polymerization, polymerization usually under a pressure of about 5 kg/cm
2
provides a polyamide resin composition which provides molded articles exhibiting excellent mechanical strength, toughness, heat resistance, and dimensional stability, low water absorption ratio, and an improved water absorption property including no decrease of the above-described properties under the influence of water.
However, for the above-described polyamide resin composition, the tensile strength of molded articles is always insufficient and the deviation of the values is substantially large, being independent of the kind of layered silicates. Moreover, when manufacturing the above-described polyamide resin composition on an industrial scale, some problems arise from the viewpoint of productivity including observation of increased pressure at a nozzle part at the withdrawal of the polymer and consequently frequent exchange of filters.
As a result of extensive studies, the present inventors have discovered that the above problems are caused by an insufficient degree of uniform dispersion of a layered silicate into a nylon matrix on the molecular level, and at the same time by oversized particles which remain in the resin composition originating from impurities contained in a layered silicate as a raw material which did not participate in the above uniform dispersion.
This invention provides a polyamide resin composition which provides molded articles exhibiting high strength, high modulus, high heat resistance, high toughness, excellent dimensional stability, and high tensile elongation with small deviation. Also provided is a process for producing said polyamide resin composition.
SUMMARY OF THE INVENTION
The present invention solves the above-described problems by providing:
(1) A polyamide resin composition in which a layered silicate having the below-described property {circle around (1)} is uniformly dispersed on a molecular level.
{circle around (1)}: average particle size from observation of transmission electron microscope is 0.1 &mgr;m or less and does not include a maximum particle size of 30 &mgr;m or higher.
(2) The polyamide resin composition according to (1) above, wherein said polyamide resin is selected from the group consisting of nylon 6, nylon 6 copolymers, nylon 11, nylon 11 copolymers, nylon 12 and nylon 12 copolymers.
(3) The polyamide resin composition according to (1) or (2) above, wherein 0.01~10 parts by weight of the layered silicate having the above-described property {circle around (1+L )} per 100 parts by weight of said polyamide resin are formulated.
(4) A process for producing the polyamide resin composition described in (3), which comprises polymerizing a monomer forming 100 parts by weight of polyamide resin after mixing with 0.1~10 parts by weight of a layered silicate of the below-described property {circle around (2)} having a cation exchange capacity of 50~200 meq/100 g and an acid (pKa 0~6 or negative in 25° C. water) at an amount of 3 times or less moles per the total cation exchange capacity of the above-described layered silicate, wherein the total amount of the above-described layered silicate and the total amount of the above-described acid are mixed with a fraction of the monomer corresponding to 30 wt % or less of the total amount of the above-described monomer, followed by addition of the rest of the monomer and polymerization of the monomer.
{circle around (2)}: average particle size of 1~6 &mgr;m by laser diffraction method; not containing particles of 30 &mgr;m or larger as a maximum particle size.
(5) A process for producing the polyamide resin composition described in (3), which comprises polymerizing a monomer forming 100 parts by weight of polyamide resin after mixing with 0.1~10 parts by weight of a layered silicate of the above-described property {circle around (2)} having a cation exchange capacity of 50~200 meq/100 g and an acid (pKa 0~6 or negative in 25° C. water) at an amount of 3 times or less moles per the total cation exchange capacity of the above-described layered silicate.
(6) A process for producing the polyamide resin composition described in (3), which comprises polymerizing a monomer forming 100 parts by weight of polyamide resin after mixing with 0.1~10 parts by weight of an organically treated layered silicate which is obtained by a process comprising (i) mixing a layered silicate of the above-described property {circle around (2)} having a cation exchange capacity of 50~200 meq/100 g, an acid (pKa 0~6 or negative in 25° C. water) at an amount of 3 times or less moles per the total cation exchange capacity of the above-described layered silicate, and a compound forming an organic cation by reacting with the above-described acid in the presence of water, and (ii) treating at 60° C. or higher.
REFERENCES:
patent: 4739007 (1988-04-01), Okada et al.
patent: 4894411 (1990-01-01), Okada et al.
patent: 5102948 (1992-04-01), Deguchi et al.
patent: 5164440 (1992-11-01), Deguchi et al.
patent: 5204078 (1993-04-01), Tateyama et al.
patent: 5248720 (1993-09-01), Deguchi et al.
patent: 5414042 (1995-05-01), Yasue et al.
patent: 5741601 (1998-04-01), Kishida et al.
patent: 0 358 415 (1990-03-01), None
patent: 940430 (1999-09-01), None
patent: 970989 (2000-01-01), None
patent: 63-230766 (1988-09-01), None
patent: 2-102261
Fujimoto Koji
Kojima Kazushige
Kokuryo Sachiko
Tamura Tsuneo
Yoshida Izumi
Cain Edward J.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Unitika Ltd.
Wyrozebski Katarzyna
LandOfFree
Polyamide resin composition and process for producing the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polyamide resin composition and process for producing the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polyamide resin composition and process for producing the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2543698