JP2007023298A - Polyamide resin composition for connector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide resin composition for a connector, having excellent mechanical characteristics, heat resistance, moldability and dimensional stability, causing little decrease of rigidity after long-term use in high-humidity atmosphere, and having excellent stability at melt retention and small dimensional change by water absorption. <P>SOLUTION: The polyamide resin composition comprises (A) 99-80 wt.% polyamide resin comprising (a) 75-50 mol% hexamethylene terephthalamide unit and (b) 25-50 mol% dodecanamide unit, having (1) 300-325°C melting point, and (2) ≥40°C glass transition temperature at saturated water absorption, and at least one peak position at ≥80°C in peak values of loss modulus observed in plurality, obtained from a viscoelastic measurement, and (B) 1-20 wt.% modified polyolefin modified with a carboxylic acid and/or a derivative thereof. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polyamide resin composition having excellent mechanical properties, heat resistance, moisture resistance and moldability, and particularly excellent rigidity and dimensional stability when placed in a high humidity environment. More specifically, it has excellent toughness, which is a characteristic of polyamide resin, and has high heat resistance, high humidity resistance, and high dimensional stability with very little reduction in rigidity even after long-term exposure to high humidity. The present invention relates to a polyamide resin and a composition thereof, and relates to a polyamide resin composition suitably used for connector applications mainly used in an automobile engine room.

  Polyamide resins represented by nylon 6 and nylon 66 have excellent properties as engineering plastics and are widely used in various industrial fields such as automobiles, electric / electronics and the like.

  In recent years, in automotive parts, particularly harness connector applications used in engine rooms, with higher engine performance and higher output, it is high even under severe use environments such as temperature rise and high humidity in the engine room. There is an increasing demand for materials that can maintain the binding and connection functions. In response to such advanced demands, nylon 6 and nylon 66 resins, which are used for general purposes, are particularly affected by water absorption, resulting in reduced rigidity and impaired connection function, large dimensional changes, and poor dimensional stability. There was a problem.

  Recently, as polyamide resins that can be used in such a severe environment, Japanese Patent Application Laid-Open Nos. 59-155426, 62-156130, and 3-201375 disclose terephthalic acid and / or Alternatively, a high melting point copolyamide resin containing isophthalic acid is disclosed. These polyamide resins have a high melting point and, at the same time, the introduction of an aromatic dicarboxylic acid unit suppresses water absorption, and can exhibit high rigidity and dimensional stability even in a high humidity environment. Molding processability, such as polymer contamination or carbonization, which is likely to be caused by polymer gelation or carbonization, or volatile gas generation due to partial decomposition is likely to occur during the production of molded products. As a result, there was a problem that it was insufficient to produce a practical molded product with high productivity.

Japanese Patent Application Laid-Open No. 61-283653 discloses that impact resistance is improved by blending the above-mentioned high melting point copolyamide resin with a modified polyolefin. Although the impact resistance is certainly improved to some extent by this technique, the initial rigidity is low, and it has not been possible to suppress a decrease in rigidity after being used for a long time, particularly in a high humidity usage environment.
Japanese Patent Laid-Open No. 9-279019

  The object of the present invention is excellent in mechanical properties, heat resistance, moldability, dimensional stability, small in rigidity even when used in a high humidity atmosphere for a long time, excellent in stability during melting residence, and by water absorption. An object of the present invention is to provide a polyamide resin composition for a connector that is suitable for molding a harness connector for an automobile having a thin portion, particularly a polyamide resin composition for a connector having a small dimensional change.

That is, the present invention provides: “(A) (a) 99 to 80% by weight of a polyamide resin comprising 75 to 50% by mole of hexamethylene terephthalamide units, (b) 25 to 50% by mole of dodecanamide units, and further having properties within the following ranges: (B) A polyamide resin composition for a connector comprising 1 to 20% by weight of a modified polyolefin modified with a carboxylic acid and / or a derivative thereof.
(B) Melting point: 300 ° C. or more and less than 325 ° C. (b) A glass transition point at the time of saturated water absorption determined from viscoelasticity measurement is 40 ° C. or more, and at least one peak among a plurality of observed loss elastic modulus peak values. Is at 80 ° C or higher. "
2. “The homopolymer of α-olefin in which the modified polyolefin of the component (B) contains at least one selected from a carboxylic acid group, a carboxylic acid anhydride group, a carboxylic acid ester group and a carboxylic acid metal base in the polymer molecular chain. 2. The polyamide resin composition for connectors according to the above 1, which is a polymer or copolymer.
3. “The polyamide resin composition for a connector according to the above 1 or 2, which is used for an automobile connector”.
4). “A connector comprising an injection-molded article of the polyamide resin composition according to any one of 1 to 3 above” is provided.

  The polyamide resin composition for a connector obtained in the present invention is obtained by polymerizing a specific copolymerization component within a very limited copolymerization ratio range as described above, and has a specific melting point, viscoelastic behavior, and water absorption. Since the main component is a copolyamide having a viscoelastic behavior, the rigidity is hardly lowered under a high humidity atmosphere, and excellent performance can be achieved by balancing heat resistance, toughness, and moldability. For this reason, it has excellent mechanical properties, heat resistance, moldability, and dimensional stability, and even when used in a high-humidity atmosphere for a long time, its rigidity is small and it has excellent durability. It exhibits excellent performance for use, and is particularly suitable for molding an automobile harness connector having a thin portion.

  In the polyamide resin composition for a connector of the present invention, the polyamide resin (A) includes (a) 75 to 50 mol% of hexamethylene terephthalamide units, preferably 70 to 55 mol% and (b) 25 to 50 dodecanamide units. Copolyamides composed of mol%, preferably 30 to 45 mol% are used. The (a) hexamethylene terephthalamide unit constituting the polyamide resin (A) is a unit synthesized from a derivative such as hexamethylene diamine and terephthalic acid or its ester or acid halide. Examples of the raw material for component (b) include 12-aminododecanoic acid and ω-laurolactam.

  As described above, a copolymerized polyamide obtained by polymerizing a specific copolymerization component within a very limited copolymerization ratio range and having a specific melting point, viscoelastic behavior, and viscoelastic behavior upon water absorption is an automotive connector. When it is used, it is possible to exhibit desirable performance such as little reduction in rigidity in a high humidity atmosphere and excellent balance between heat resistance, toughness, and moldability. In particular, it is important that there is a segment having a glass transition point of 40 ° C. or higher at the time of water absorption and a loss elastic modulus peak of 80 ° C. or higher. Moreover, by using a component having a low amide group concentration as a copolymerization component as compared with a conventionally known high-melting point copolyamide resin containing terephthalic acid and / or isophthalic acid, contamination of a molded product, gas burning, etc. Molding problems have been greatly improved.

  When the copolymerization amount of the component (a) is greater than the above range, the melting point of the polyamide resin to be produced becomes high (for example, more than 325 ° C.), the deterioration at the time of melting becomes obvious, and the probability of foreign matter mixing into the molded product increases. It is not preferable because molding processability is impaired, for example, gas burning occurs in the molded product. Conversely, if it is less than the above range, the viscoelastic property at the time of water absorption is decreased, which is not preferable. When the copolymerization amount of the component (b) is larger than the above range, the melting point is lowered and the necessary heat resistance cannot be maintained, which is not preferable. Conversely, when the amount is less than the above range, the water absorption increases, This is not preferable because the rigidity is lowered.

  The degree of polymerization of the polyamide resin (A) used in the present invention is not particularly limited, but the relative viscosity when measured at 25 ° C. in a 1% concentrated sulfuric acid solution from the viewpoint of mechanical properties and moldability. Usually, those in the range of 1.5 to 5.0, preferably 1.8 to 3.5, particularly preferably 2.0 to 2.8 are suitable. Further, the polyamide resin (A) may contain an amide component not defined in the above (a) and (b) in a small amount, for example, 5 mol% or less, as long as the effect of the present invention is not impaired.

Further, the production method of the polyamide resin (A) is not particularly limited, but a normal pressure melt polymerization, for example, a mixed aqueous solution of hexamethylene diammonium terephthalate (6T salt) and ω-laurolactam is 20 to 60 kg / cm ² of water vapor. A conventional melt polymerization method in which a heat reaction is performed under pressure, followed by melt polymerization while releasing water in the system, or a prepolymer is formed once by heating the raw material aqueous solution at 200 to 350 ° C. For example, a method of solid-phase polymerization with a solvent or a method of increasing the degree of polymerization with a melt extruder.

  The polyamide resin (A) may be added with additives such as viscosity modifiers, pigments, anti-coloring agents, heat-resistant agents and the like as long as the properties are not impaired.

  In the polyamide resin composition of the present invention, (B) a modified polyolefin modified with a carboxylic acid and / or a derivative thereof is added to the above-described polyamide resin (A). The blending ratio of both components (A) and (B) is 99 to 80% by weight, preferably 97 to 90% by weight, preferably 1 to 20% by weight of the modified polyolefin of component (B), relative to polyamide resin (A). Is 3 to 10% by weight.

  The component (B) is a polyolefin containing a functional group having an affinity for the polyamide resin (A) in its molecule, and in particular, a carboxylic acid group, a carboxylic acid anhydride group, a carboxylic acid ester group, a carboxylic acid An α-olefin homopolymer or copolymer containing at least one selected from metal bases in the polymer molecular chain is preferred.

  Specific examples of α-olefin homopolymers or copolymers include homopolymers such as polyethylene, polypropylene, polybutene-1, polypentene-1, polymethylpentene, ethylene, propylene, butene-1, pentene-1, 4-methylpentene. -1, α-olefins such as hexene-1, octene-1, isobutylene, 1,4-hexadiene dicyclopentadiene, 2,5-norbornadiene, 5-ethylidenenorbornene, 5-ethyl-2,5-norbornadiene, 5- (1 Mention may be made of polyolefins obtained by radical polymerization of at least one non-conjugated diene such as' -probenyl) -2-norbornene using a normal metal catalyst or a metallocene-based high-performance catalyst.

  The diene elastomer is an AB or AB-A 'type block copolymer elastic body composed of a vinyl aromatic hydrocarbon and a conjugated diene, and the end blocks A and A' are the same or different. And thermoplastic homopolymers or copolymers derived from vinyl aromatic hydrocarbons, where the aromatic moiety may be monocyclic or polycyclic, examples of such vinyl aromatic hydrocarbons include Styrene, α-methylstyrene, vinyltoluene, vinylxylene, ethylvinylxylene, vinylnaphthalene and mixtures thereof. The intermediate polymer block B is composed of a conjugated diene hydrocarbon, and examples thereof include polymers derived from 1,3-butadiene, 2,3-dimethylbutadiene, isoprene, 1,3-pentadiene, and mixtures thereof. In the present invention, those obtained by subjecting the intermediate polymer block B of the block copolymer to a hydrogenation treatment are also included.

  Specific examples of the polyolefin copolymer include ethylene / propylene copolymer, ethylene / butene-1 copolymer, ethylene / hexene-1 copolymer, ethylene / propylene / dicyclopentadiene copolymer, ethylene / propylene / 5-ethylidene- 2-norbornene copolymer, unhydrogenated or hydrogenated polybutadiene, unhydrogenated or hydrogenated styrene / isoprene / styrene triblock copolymer, unhydrogenated or hydrogenated styrene / butadiene / styrene triblock copolymer, etc. Can be mentioned.

  Examples of functional groups that modify these polyolefins include carboxylic acid groups, carboxylic anhydride groups, carboxylic acid ester groups, carboxylic acid metal base carboxylic imide groups, carboxylic acid amide groups, and the like. Examples include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, methylmaleic acid, methyl fumaric acid, mesaconic acid, citraconic acid, glutaconic acid and metal salts of these carboxylic acids, hydrogen maleate Methyl, methyl hydrogen itaconate, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl acrylate, methyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl methacrylate, methacrylic Aminoethyl, acid Dimethyl inoate, dimethyl itaconate, maleic anhydride, itaconic anhydride, citraconic anhydride, endobicyclo- (2,2,1) -5-heptene-2,3-dicarboxylic acid, endobicyclo- (2,2, 1) -5-heptene-2,3-dicarboxylic anhydride, maleimide, N-ethylmaleimide, N-butylmaleimide, N-phenylmaleimide, glycidyl acrylate, glycidyl methacrylate, glycidyl ethacrylate, glycidyl itaconate, citracone Such as glycidyl acid.

  The method for introducing these functional group-containing components is not particularly limited, and methods such as copolymerization or graft introduction using a radical initiator to an unmodified polyolefin can be used. The amount of the functional group-containing component introduced is suitably in the range of 0.001 to 40 mol%, preferably 0.01 to 35 mol%, based on the entire olefin monomer in the modified polyolefin.

  Specific examples of modified polyolefins particularly useful in the present invention include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, ethylene / acrylic acid copolymers, ethylene / methacrylic acid copolymers, and carboxylic acid moieties in these copolymers. Or a salt of sodium, lithium, potassium, zinc or calcium, ethylene / methyl acrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / Ethyl methacrylate copolymer, ethylene / ethyl acrylate-g-maleic anhydride copolymer ("g" represents graft, the same shall apply hereinafter), ethylene / methyl methacrylate-g-maleic anhydride copolymer , Ethylene / ethyl acrylate-g-maleimide copolymer, ethylene / a Ethyl laurate-g-N-phenylmaleimide copolymer and partially saponified products of these copolymers, ethylene / glycidyl methacrylate copolymer, ethylene / vinyl acetate / glycidyl methacrylate copolymer, ethylene / methyl methacrylate / glycidyl methacrylate Copolymer, ethylene / glycidyl acrylate copolymer, ethylene / vinyl acetate / glycidyl acrylate copolymer, ethylene / glycidyl ether copolymer, ethylene / propylene-g-maleic anhydride copolymer, ethylene / butene-1- g-maleic anhydride copolymer, ethylene / propylene / 1,4-hexadiene-g-maleic anhydride copolymer, ethylene / propylene / dicyclopentadiene-g-maleic anhydride copolymer, ethylene / propylene / 2 , -Norbornadiene-g-maleic anhydride copolymer, ethylene / propylene-gN-phenylmaleimide copolymer, ethylene / butene-1-gN-phenylmaleimide copolymer, hydrogenated styrene / butadiene / styrene- g-maleic anhydride copolymer, hydrogenated styrene / isoprene / styrene-g-maleic anhydride copolymer, ethylene / propylene-g-glycidyl methacrylate copolymer, ethylene / butene-1-g-glycidyl methacrylate Copolymer, ethylene / propylene / 1,4-hexadiene-g-glycidyl methacrylate copolymer, ethylene / propylene / dicyclopentadiene-g-glycidyl methacrylate copolymer, hydrogenated styrene / butadiene / styrene-g- Examples thereof include a glycidyl methacrylate copolymer.

  The polyamide resin composition obtained here has an antioxidant, a heat stabilizer such as copper iodide and potassium iodide, a lubricant, a crystal nucleating agent, an ultraviolet light inhibitor, a colorant, a hardener, as long as its properties are not impaired. Conventional additives such as flame retardants and small amounts of other polymers can be added.

  The method for producing the polyamide resin composition is not particularly limited, and after the polyamide resin, the modified polyolefin and other additives are dry blended using a ribbon blender, a Henschel mixer, a V blender, etc., a Banbury mixer, a mixing roll, a uniaxial or Examples thereof include a melt kneading method using a twin-screw extruder, a kneader and the like. Among them, a typical method is melt-kneading using a single-screw or twin-screw extruder having a sufficient kneading force.

  The polyamide resin composition of the present invention has excellent mechanical properties, heat resistance, moldability, and dimensional stability, and has a small decrease in rigidity even when used for a long time in a high humidity atmosphere. The dimensional change is small, and it is particularly suitable for manufacturing an automobile harness connector molded product having a thin portion, and the obtained connector molded product has a high practical value.

  Hereinafter, although an example is given and the effect of the present invention is further explained, the present invention is not limited only to these examples.

  Various characteristics described in Examples, Reference Examples and Comparative Examples were measured by the following methods.

Melting point: Using a RDC220 differential operating calorimeter manufactured by Seiko Denshi Kogyo Co., Ltd., the temperature was raised once at a temperature rising rate of 40 ° C./min, held at an endothermic peak temperature plus 20 ° C. for 5 minutes, and then 20 ° C. / After the temperature was lowered to 100 ° C. at a rate of minutes, the peak value when measured at a rate of temperature rise of 20 ° C./min was taken as the melting point.

Viscoelastic behavior: A polyamide resin sample was melt press molded to produce a sheet having a thickness of about 0.2 mm, and a 2 × 50 mm strip-shaped test piece was cut out therefrom, and Leover Ibron DDV-II-EA manufactured by Toyo Baldwin Co., Ltd. Was measured under the conditions of a frequency of 110 Hz and a heating rate of 2 ° C./min. The peak temperature of the loss elastic modulus corresponding to α-dispersion was taken as the glass transition point. In addition, the peak temperature on the highest temperature side of the loss elastic modulus observed by specific splitting at the time of water absorption was displayed as the high temperature side peak at the time of water absorption.

-Tensile strength: measured in accordance with ASTM D638.
-Flexural modulus: According to ASTM D790, the flexural modulus at the time of absolutely dry and at the time of atmospheric equilibrium water absorption was measured.

・ Practical water absorption characteristics: The connector shown in FIG. 1 having a maximum value of 55 mm, a height of 13 mm, a depth of 37 mm, and a thickness of 1 mm is formed by injection molding, and this is placed as shown in FIG. The degree of deformation of the molded product was observed after being left for 100 hours under the conditions of 30 ° C. and 95% RH in a state where the weight was placed. Judgment criteria are as follows.
○: No deformation △: Small deformation ×: Large deformation

・ Stability during melt residence: Set the cylinder temperature of the above injection molding machine to the melting point of the polyamide resin plus 30 ° C., hold the connector in the cylinder for 15 minutes, and then mold the foreign matter in the molded product. The number and the occurrence behavior of gas burn were visually observed and used as an index of stability during melt residence. Judgment criteria are as follows.
○: The number of foreign matters is 1 or less, and no gas is burnt. Δ: The number of foreign matters is 1 to 2, and the gas burn is small. ×: The number of foreign matters is 3 or more, the gas burn is large.

Reference example 1
Hexamethylene diammonium terephthalate (6T salt) and ω-laurolactam mixed aqueous solution (solid raw material concentration 60% by weight) prepared so as to be 65 mol% hexamethylene terephthalamide units and 35 mol% dodecanamide units The mixture was charged into a polymerization can, heated with stirring, reacted at a water vapor pressure of 35 kg / cm ² for 3.5 hours, and then the reaction mixture was discharged from the lower discharge outlet of the polymerization can and collected. The relative viscosity (1% concentration) of the sulfuric acid solution of the polyamide prepolymer obtained here was 1.45. When this was subjected to solid phase polymerization at 220 ° C. for 10 hours under vacuum to evaluate its properties as a polyamide having a relative viscosity of 2.4, the properties were as shown in Table 1. Various test pieces were obtained by injection molding this polyamide resin, and the characteristics were measured. As shown in Table 1, it has excellent rigidity and dimensional stability at the time of water absorption. It turned out to be useful as a material of a thing.

Comparative Example 1
Polymerization, molding, and property evaluation were performed in exactly the same manner as in Reference Example 1 except that the polyamide composition was changed to 65 mol% of hexamethylene terephthalamide units, 30 mol% of hexamethylene adipamide units, and 5 mol% of dodecanamide units. It was. The results are shown in Table 1. The polyamide resin obtained here had a particularly low rigidity at the time of water absorption, and also had insufficient thermal stability and could not withstand practical use.

Comparative Example 2
Polymerization was carried out in exactly the same manner as in Reference Example 1, except that the raw material mixing ratio was changed so that the composition of the resulting polyamide was 25 mol% hexamethylene terephthalamide units, 50 mol% hexamethylene sebacamide units, and 25 mol% caproamide units. Molding and property evaluation were performed. The results are shown in Table 1, and the polyamide resin obtained here also has a low rigidity at the time of water absorption and cannot withstand practical use.

Comparative Example 3
Exactly the same as Reference Example 1 except that the raw material mixing ratio was changed so that the composition of the resulting polyamide was 65 mol% hexamethylene terephthalamide units, 25 mol% hexamethylene isophthalamide units and 10 mol% hexamethylene adipamide units. Polymerization, molding, and property evaluation were performed. The results are shown in Table 1. The polyamide resin obtained here has insufficient melt heat stability and cannot withstand practical use.

Example 1
The polyamide resin obtained in the above Reference Example 1 and EPR modified with maleic anhydride were melt-kneaded at a compounding ratio shown in Table 2 using a twin screw extruder, and then injection molding and characteristic evaluation were performed sequentially. The result was a composition having excellent characteristics, as summarized in Table 2.

It is the schematic of the connector molded article produced in the Example, (A) is a top view, (B) is a front view.

Claims (4)

(A) (a) 75 to 50% by mole of hexamethylene terephthalamide units, (b) 99 to 80% by weight of polyamide resin having 25 to 50% by mole of dodecanamide units, and the characteristics are within the following ranges: B) A polyamide resin composition for a connector comprising 1 to 20% by weight of a modified polyolefin modified with a carboxylic acid and / or a derivative thereof.
(B) Melting point: 300 ° C. or more and less than 325 ° C. (b) A glass transition point at the time of saturated water absorption determined from viscoelasticity measurement is 40 ° C. or more, and at least one peak among a plurality of observed loss elastic modulus peak values. Is at 80 ° C or higher.   The α-olefin homopolymer in which the modified polyolefin of the component (B) contains at least one selected from a carboxylic acid group, a carboxylic anhydride group, a carboxylic acid ester group, and a carboxylic acid metal base in the polymer molecular chain. 2. The polyamide resin composition for connectors according to claim 1, which is a copolymer.   The polyamide resin composition for connectors according to claim 1 or 2, which is used for automobile connectors.   A connector comprising an injection-molded product of the polyamide resin composition according to claim 1.

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