POLYAMIDE RESIN COMPOSITION

Abstract: Polytetramethylene adipamide resin compositions containing 100 parts by weight of the polyamide and 2 to 20 parts by weight of a silicon oil. Objects produced from the composition possess good surface appearance, excellent sliding properties and high heat resistance and rigidity.

Description: POLYAMIDE RESIN COMPOSITION DETAILED DESCRIPTION OF THE INVENTION (Scope of industrial application) The subject, invention relates to polytetramethylene adipamide resin compositions superior in sliding characteristics. (Description of prior art) Being fundamentally superior In friction and wear charac- "" teristics, polyamldes are regarded as being suitable for manufacturing gears and bearings and other sliding parts. The wear depends on the pressures applied to the sliding surface, the sliding speeds, the atmospheric conditions, the temperature and so forth. For practical applications resistance to increasingly severe con¬ ditions are demanded and polya ide materials have been modified for this. Hitherto polyamide compositions obtained by adding molybdenum disulfide, polyethylene, fluoric polymers and silicon oils to polya i- des have generally been used for this purpose. However It has been observed that in the case of the ordinary straight-chain polyamldes e.g. polycaprolactam (nylon-6) or polyhexa- ehtylene adipamide (nylon-6.6), the silicon oil is insufficiently accepted by the material and causes considerable bleed-out to the sur- face of moldings that are obtained from compositions of these polyami- des with silicon oils. Because of this bleeding-out effect the moldings become inferior in surface appearance. However for obtaining good sliding properties it is necessary to have the siliconoil present in appreciable amounts. Further the mechanical properties of the polyamide composition should remain high to be use- full under severe conditions. One has tried to solve this problem in essentially two manners. In the first solution one uses mixtures of lubricants, in which silicon oil is present in low concentrations. For instance a mixture of 2 percent silicon oil and 18 percent by weight polytetra-fluoroethylene in 80 percent by weight polyamide is used in US Patent publication 4428589. Secondly one has tried to incorporate in the polyamide molding an inorganic highly porous material which functions as a carrier for the silicon oil. See for instance JP-A-57174345. However these compositions have the disadvantage of being difficult to process, or need expensive materials or the physical properties of the polyamide composition have been negatively effected. The object of the invention is therefore to produce a polyamide/silicon oil composition of superior sliding properties and mechanical strength with good surface appearance. It has been found that polytetramethylene adipamide (nylon-4.6) shows a supprisingly high affinity for silicon oils, so that even at high concentrations of the silicon-oils no unacceptable level of bleeding is observed. Further the resin composition shows superior properties over present materials to make a highly prac¬ ticable material for various kinds of gears and bearings. Especially the combination of high heat resistance and rigidity of nylon* 4.6 and the vast improvement In sliding performance due to the presence of a relatively high concentration of silicon oil produces these synergistic effects. Therefore the polyamide resin composition according to the subject invention is obtainable by blending 2 to 20 parts by weight of silicon oil with 100 parts by weight of a polyamide with tetramethylene adipa¬ mide as main component. The polyamides according to the subject invention are copoly- mers and mixtures of polyamides containing polytetramethyleneadipamide and tetramethylene adipamide as main components. In principle there excist no limitations concerning the copolymer and mixture components, so that all known amide-forming compounds can be chosen. Representative among the former are 6-aminocaproic, 11-aminoundecanic, 12-aminododecanic, paraminomethylbenzoic and other amino acids; ε-caprolactam, ω-laurolactam and other lactams; hexamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2.2.4-/2,2,4-tri- methylhexamethylenediamine, 5-methylnonamethylenediamine, methaxylire- nediamine, paraxylirerediamine 1,3- and 1,4-bis (aminomethyl)cyclo- hexanes, l-amino-3-aminometh l-3,5,5-trimethylcyclohexane, bis(4-aminocyclohexyl)methane, bis(3-methyl-4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)propane, bis-(aminoproρyl)piperazine, amino- ethylpiperazine and other diamines and adipic acids; and adipic, suberic, azelaic, dodecane-2, terephthalic, isophthalic, 2-chlorotere-ρhthalic, 2-methyltereρhthlatic, 5-methylisoρhthalic, 5-sodiumsulfoisophthalic, hexahydroterephthalic, hexahydroisophthalic, diglycolie and other dicarboxylic acids. The latter Include the polyamides being composed thereof. Polyamides containing tetramethylene as main component, for instance more than 80 mole percent, can be produced by any known pro¬ cess. However preference should be given to the processes disclosed in US patent publications 4,460,762, 4,408,036 and 4,463,166 or EP-A 0039524, 0038094 and 0077106. High molecular weight polyamides should be produced through solid- pha-se aftercondensation in a water-vapor containing atmosphere of pre- polymers having small contents of cyclic endgroups, that are produced under specific conditions or in 2-pyrrolldone, N-methylpyrrolidone or another polar organic solvent. Their degree of polymerization can vary in principle over a wide range. The polymers having a relative visco¬ sity between 2.0 and 6.0 g/dl, as measured in a solution of 1 gram in 100 ml 98 % by weight sulphuric acid, are preferred. The silicon oils according to the subject invention are the polymers fundamentally having polysiloxane structures. Representative thereamong are for example the modified polysiloxanes containing poly- dimethylsiloxane and dimethylsiloxane, the materials with component units represented by the following formulae (1) to (7) and materials possessing endgroups represented by the following formulae (8) to (12). 20 ^Si-R 4 -NH 2 (8) JΞ≡^Si-R -COOH (9) ^ • Si-R4 -OH (10) ^ • Si-R4 -A-OH (11) ,«< -CH-CH, C«, herein Ri and R2 denote hydrogen atoms, the alkyl groups having one 1 to four carbon atoms, cyclohexyl groups, phenyl groups and benzyl groups (R ] _ and R2 not being simultaneously hydrogen or a methyl group); R3 an alkyl group having one to four carbon atoms; R4 an alkylene group having one to six carbon atoms and A an polyalkylene having a polymerization degree of 1 to 50. The viscosity fo the silicon oils according to the invention is not limitative and can be selected within the range of 100 to 50,000 centistokes at a temperature of 25 °C. However those having viscosities of 1,000 to 30,000 centistokes are preferably used for the convenience of the handling in blending and mixing with polyamides. The resin compositions according to the subject Invention are produced by adding 2 to 20, preferably 3 to 18, more preferably 5 to 15, parts by weight of silicon oils to 100 parts by weight of poly- tetramethylene adipamide. Addition ratios less or more than 2 or 20 parts, respectively by weight do not improve them in sliding charac¬ teristic or cause decomposition, foaming and other undesirable pheno¬ mena. Other materials e.g. pigments, dyes, reinforcers, fillers, heat stabilizers, anti-oxidants, weather resistants, nucleating agents, mold release agents, plasticizers, flame retardants, antista¬ tics and other polymers may be added to Che resin compositions according to the subject Invention unless their oldabilities and phy¬ sical properties are affected. Particularly the addition of reinfor- cers and fillers is important. The fibrous and powdery reinforcers available therefor include more specifically glass fibers, asbestos fibers, carbon fibers, graphite fibers, wollastonite, talc, calcium carbonate, mica, clay, potassium titanate whisker and glass beads. The processes for producing resin compositions according to the subject invention are not limited. One of the most common ones Is the melting and mixing of both components supplied to a one- or multi- shaft extruder eventually after premixing in solid form. The resin compositions according to the invention can be used for the production of moldings being superior in physical properties by injection molding, extrusion, blow-molding, compressive and the other molding methods being used for ordinary thermoplastic resins. They are useful for manufacturing various automotive parts, mechanical parts, electric and electronic parts, general miscellaneous goods and so forth. (Embodiments) The subject Invention will be described in more detail in connection with the examples hereinafter. The following methods were used to evaluate the characteristics of the polymers and their moldings in the examples and comparative examples. (1) Relative viscosity: JIS K6810 (2) Sliding characteristic: the friction coefficient of test pieces with steal (S-45C) and the limit PV product value at which they melt by frictional heat were measured by using a Suzuki type fric- tional and wear characteristic tester with surface pressure (Pkg/c ) and running speed (Vm/min. ) changed. (3) Tensile characteristic: ASTM D638 (4). Bending characteristic: • ASTM D790 (5) Izod impact strength: ASTM D256 (6) Thermal deformation temperature: ASTM D648 Example 1 A mixture prepared by mixing 10 parts by weight of polydi- methylsiloxane (Toray Silicon .K. 's SH 200 showing a viscosity of 12,500 cs at a temperature of 25 °C) to 100 parts by weight of nylon-46 powder having a relative viscosity of 3.90 was melted, kneaded and pelletized at a temperature of 305 °C using a 40 mm aper¬ ture molder. These pellets were vacuum-dried and used for the molding of various kinds of test pieces for measuring the different physical properties by using an injector molder with its cylinder and mold set at the temperatures of 300 °C and 80 °C respectively. Table 1 shows the results of the evaluation of the sliding- characteristics and other physical properties. Causing only a little surface bleed-out of silicon oil, the moldign showed to be very superior in sliding characteristics, strength, rigidity and heat resistance. The molding stability of the materials and the physical properties and appearances of the test pieces were measured as shown in the table. Comparative Example 1: Test pieces obtained through the injection molding of nylon 4,6 without silicon oil as was used for Example 1 showed the following unsatisfactory values of the sliding characteristics. Wear coefficient: 0.65 Limit PV product value: 600 kg/cm^. /min. Comparative Example 2: Experiment 1 was repeated, however 30 parts of polydi- methylsiloxane had been added. Considerable foam formation happened, indicating a very low operational stability. Comparative Example ' 3: The test pieces obtained through the same extruder kneading and injection molding as being mentioned in connection with Experiment 1 except that nylon 4,6 Is replaced with nylon 6,6 showed an inferior appearance caused by considerable surface bleed-out of silicon oil. Experiments 2 to 14: Table 1 shows the physical properties of the test pieces obtained through the same operation as described in Experiment 1 with the different kinds and addition ratios of nylon 4,6 and silicon oil. In all cases shown in the table 1, polyamide resin compositions superior in sliding characteristic, strength, ridigity and heat resistance were obtained. Embodiment 15: A mixture obtained by adding 12 parts by weight of the poly- dimethylsiloxane from Example 1 and 45 parts by weight of a chopped strand glass fiber (Nippon Denki Glass ECS03) to 100 parts by weight of nylon 4,6 pellets having a relative viscosity of 3.70 was melted, kneaded and pelletizxed at a temperature of 310 °C using a 65 mm aper¬ ture molder. The following were the physical properties obtained after vacuu rdrying and injection-molding of these pellets. Tensile strength: 1,830 kg/cm 2 Bending strength: 2,750 kg/cm 2 Bending: 96,000 kg/cm 2 Izod impact strength: 9 kg.cm/cm-notch Thermal deformation temperature: 285 °C Limit PV product: 3,500 kg/cm 2 .m/min. Table 1 Surface appearance of Excellent Excellent Excellent Excellent Excellent Excellent Exce molded articles Surface appearance of Excellent Excellent Excellent Excellent Excellent Excellent Excell molded articles a) N-4,6-polytetramethylene adipamide, N-4,6/6-ρoly/tetramethylene adipamide/caprolactam) copolymer (copolymerization ratio: 95/5 percents), N-4,6/6,6-ρoly(tetramethylene adipamide/hexamethylene adipamide) copolymer (copolymerization 90/10 percents by weight), N-4,6/N-6,6: polytetramethylene adipamide and polyhexame h lene adipaα|d/.e (mixing ratio 90/10 percents by weight) b) All the following are the grade names given by Toray Silicon K.K. SH 8421

Claims: CLAIMS 1. Polyamide resin composition containing 100 parts by weight of a polyamide with tetramethylene adipamide as main component and 2 to 20 parts by weight of silicon oil. 2. Polyamide resin composition according to claim 1 containing 3 to 18 parts by weight of silicon oil. 3. Polyamide resin composition according to one of the claims 1 and 2 containing 5 to 15 parts by weight of silicon oil. 4. Polyamide resin composition according to one of the claims 1-3 in which the silicon oil has a viscosity in the range of 100 to 50,000 centistokes. 5. Polyamide resin composition according to claim 4 in which the silicon oil has a viscosity in the range of 1,000 to 30,000 cen¬ tistokes. 6. Polyamide resin composition according to one of the claims 1-5 in which the silicon oil has been chosen from the compounds repre¬ sented by the general for ual (1)-(12) in the description. • 7. Molds mainly consisting of a polyamide composition according to one of the claims 1-6. 8. Process for the preparation of a polyamide resin composition with superior sliding characteristics by blending 2 to 20 parts by weight of silicon oil with 100 parts by weight of a polyamide with tetramethylene adipamide as main component.

Inventors: CHIBA KAZUMASA, CHIBA, KAZUMASA
Applicants: STAMICARBON, STAMICARBON B.V.
Application year: 1985
Main classification: C08L77
IPC codes: C08K5, C08L77, C08L81, C08L83