WO1996035742A1

WO1996035742A1 - All-aromatic polyamide particles or fibers containing resin composition

Info

Publication number: WO1996035742A1
Application number: PCT/US1996/006825
Authority: WO
Inventors: Toshikazu Kobayashi; Tatsuhiro Takahashi; Edmund Arthur Flexman, Jr.
Original assignee: E.I. Du Pont De Nemours And Company
Priority date: 1995-05-12
Filing date: 1996-05-13
Publication date: 1996-11-14
Also published as: JP3665383B2; JPH08302212A

Abstract

The invention provides a resin composition having excellent sliding properties and mechanical properties for its molded articles. The resin composition includes 99.8-30.0 % by weight of a matrix resin comprising a matrix resin comprising a thermoplastic resin which is compatible or semi-compatible with a thermoplastic phenolic resin, 0.1-30.0 % by weight of the thermoplastic phenolic resin, and 0.1-40.0 % by weight of all-aromatic polyamide particles or fibers. Mechanical properties are improved without having the sliding properties of the molded article adversely affected.

Description

TITLE

ALL-AROMATIC POLYAMIDE PARTICLES OR FIBERS CONTAINING RESIN COMPOSITION

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a resin composition which has excellent mechanical properties, such as tensile strength and flexural modulus and is suitable for use in sliding molded parts, specifically to a resin composition obtained by adding a thermoplastic phenolic resin and all-aromatic polyamide particles or fibers to a thermoplastic resin matrix. Description of the Related Art

Resin compositions which are aimed at improving the lubricity and friction characteristics, such as wear resistance, of thermoplastic resins, such as polyamides, or thermoset resins, such as phenolic resins are obtained by adding aromatic polyamide particles to these matrix resins are disclosed in International Laid Open WO 093/04300, Japanese Patent Laid Open H 2-163163, Japanese Patent Laid Open H 2-185563, and so on. Japanese Patent Laid Open H 4-283262 proposes incorporating, in a matrix resin, surface-modified aromatic polyamide particles obtained by the graft-wise addition of organics to the surface of the aromatic polyamide particles.

Although the addition of aromatic polyamide particles to these thermoplastic resins improves the sliding properties of the molded articles therefrom, mechanical properties, such as tensile strength and flexural modulus, are disadvantageously reduced. Surface modified aromatic polyamide particles may suppress the reduction in mechanical properties to some extent, but the work of surface modifying aromatic polyamide particles itself is cumbersome, making this approach not necessarily a highly productive method.

SUMMARY OF THE INVENTION A resin composition having 99.8-30.0% by weight of a matrix resin comprising a matrix resin comprising a thermoplastic resin which is compatible or semi-compatible with a thermoplastic phenolic resin, 0.1-30.0% by weight of the thermoplastic phenolic resin, and 0.1-40.0% by weight of all-aromatic polyamide particles or fibers. DETAILED DESCRIPTION OF THE INVENTION

The present invention aims to provide a resin composition which has excellent mechanical properties such as tensile strength and flexural modulus and friction characteristics, and is suitable to be molded into sliding parts. The present inventors discovered that the decrease in mechanical properties affected by the addition of aromatic polyamide particles is related to the quality of the adhesion between the aromatic polyamide particles and the matrix resin, and found that the adhesion may be improved by adding a thermoplastic phenolic resin, which has led to the completion of this invention. The present invention is a resin composition comprising

99.8-30.0% by weight of a matrix resin comprising a matrix resin comprising a thermoplastic resin which is compatible or semi-compatible with a thermoplastic phenolic resin, 0.1-30.0% by weight of the thermoplastic phenolic resin, and 0.1-40.0% by weight of all-aromatic polyamide particles or fibers. The thermoplastic phenolic resin in this invention is a polycondensate of a phenolic compound and formaldehyde, preferably an oligomer or polymer obtained by polycondensing in the presence of an acid catalyst. Phenolic compounds include phenol, alkyl phenols, such as cresol, butylphenol, octylphenol, naphthol, resorcinol, hydroquinone, hydroxybenzoic acid, and the like. A polyvinylphenol which is a polymer of p-vinylphenol can also be suitably used.

The thermoplastic phenolic resin used should have a number average molecular weight, in general, of up to 150,000, preferably 200-10,000. Too small an amount of addition of a thermoplastic phenolic resin will fail to improve the adhesion between the all-aromatic polyamide particles or fibers and the matrix resin, which is not preferred, nor is the use of too large an amount which considerably decreases the elongation of the molded articles therefrom. The suitable amount of addition of the thermoplastic phenolic resin is 0.1-30.0% by weight based on the total resin weight. The matrix resin in this invention is a thermoplastic resin which is compatible or semi-compatible with the phenolic resin. Whether it is compatible or semi-compatible is judged by the clarity of the melt obtained by melt mixing the matrix resin with the phenolic resin, the shift in the glass transition temperature (Tg) or melt temperature (Mp) according to a differential scanning calorimetric measurement (DSC), the change in the peak temperature position of the dissipation factor (tan delta) by dynamic viscoelastic measurement (DMA), and the like. Specifically, the matrix resin and the thermoplastic phenolic resin are judged to be compatible or semi-compatible if the mix melt is clear or semi-clear, or if there is a shift in the glass transition temperature (Tg) or the melt temperature (Mp) peak of a mixture of the matrix resin with the thermoplastic phenolic resin by DSC, from that of the DSC data of the matrix resin alone, or if there is change in the dissipation factor (tan delta) peak temperature as measured by DMA of a mixture compared to the matrix resin alone.

These thermoplastic resins include thermoplastic resins having functional groups, such as esters, nitriles, amides, ketones, ethers, sulfides, sulfones, carbonates, urethanes, and the like, such as styrene acrylonitrile copolymer resin (SAN), methyl methacrylate resin (PMMA), polycaprolactone resin (PCL), styrene-maleic anhydride copolymer resin (S/MANH), imidated methyl methacrylate resin (EVIM-MMA), polycarbonate resin (PC), polyarylate resin (PAR), polysulfone resin, polyphenyleneoxide (PPO), semi-aromatic polyamide resin (6T/6I), polyamide resins (nylon 6, nylon 612), polyethylene terephthalate resin (PET), polybutylene terephthalate resin (PBT), liquid crystalline polymer resin (LCP), polyphenylene sulfide resin (PPS), polyacetal resin (POM), polyether ketone ketone resin (PEKK), and the like.

The amount of the matrix resin added is 99.8-30.0% by weight based on the total resin weight.

The all-aromatic polyamides in this invention are polymers essentially comprising the following repeating units:

-NH-ARι-NH-CO-AR₂-CO- where AR₂ and AR₂ are divalent aromatic groups which may be the same or different. Preferred are para-all- aromatic polyamides, specifically para-aromatic polycarbon amides in which ARi and AR₂ are the same or different divalent para-oriented aromatic groups. The para-oriented aromatic groups include substituted or unsubstituted aromatic groups including 1,4-phenylene, 4,4'-biphenylene, 2,6-naphthalene, 1,5-naphthalene. Suitable substituents are, for example, chloro, lower alkyl, and methoxy groups. Para-oriented all-aromatic polyamides include para-oriented copolymers from two or more para-oriented monomers containing a small amount of a comonomer of the same aromatic in which both an acid and amine functional group are present together.

All aromatic polyamides preferably used in this invention are obtained by polymerizing an aromatic amine at least 80 mole % of which is paraphenylene diamine and an aromatic dicarboxylic halide, at least 80 mole % of which is a terephthaloyl halide in an amide solvent, preferably at temperatures not higher than 60°C. The preferred amide solvents include N-methyl pyrrolidone, dimethylacetamide, tetramethylurea containing an alkali metal halide. The most suitable all-aromatic polyamide in this invention is a poly-p-phenylene terephthalamide.

All aromatic polyamide fibers which are used in this invention have diameters of not more than 30 microns or particles having a particle size of not more than 500 microns. Preferably, all-aromatic polyamide particles are used, where too large a particle size will give molded articles with reduced mechanical properties which cannot be prevented even by adding a thermoplastic phenolic resin. The preferred all-aromatic polyamide particles have a 1-50 micron particle size. It is not preferred to add too small an amount of the all-aromatic polyamide particles or fibers because no expected improvement on sliding properties is obtained, while using too large an amount will decrease the mechanical properties. The preferred amount of addition of all-aromatic polyamide particles or fibers are 0.1-40% by weight based on the total resin. The resin composition of this invention may, in addition to the above components, be compounded with a variety of additives which are normally added, such as a stabilizer, a nucleating agent, an antistatic agent, a flame retardant, a colorant, a lubricant, and the like. It is also permissible to add a filler, such as glass fiber, inorganic powder, talc, or the like. Methods known in the art can be used for manufacturing the resin composition of this invention. They include, for example, a method of kneading each component in a molder, such as an extruder, a method of mechanically kneading using a kneader, or the like, a method of mixing each component in a suitable good solvent at the same time or dissolving each component individually, followed by mixing and removing the solvent, or a combination of two or more of these methods, and the like.

The thermoplastic phenolic resin is compatible or semi-compatible and improves the adhesion of the matrix resin to all-aromatic polyamide particles or fibers which are added to impart sliding properties to the matrix resin. Therefore, the addition of a thermoplastic phenolic resin, along with the all-aromatic polyamide particles or fibers into the matrix resin will uniformly disperse the all-aromatic polyamide particles or fibers in the matrix resin, thereby improving the mechanical properties of the molded articles without reducing sliding properties. EXAMPLES

Example 1 - Compatibilitv of Thermoplastic Phenolic Resins and Matrix Resins The compatibility or semi-compatibility of each matrix resin with a Novolak resin was judged by observing the clarity of a melt mixture of the Novolak resin with each matrix resin, or measuring any shift in the glass transition temperature (Tg) or melt temperature (Mp) on DSC, or a change in the temperature position of the peak temperature position of the dissipating factor (tan delta) on DMA. Table 1 shows thermoplastic resins which are compatible or semi-compatible with the thermoplastic phenolic resin.

Table 1

DSC DMA

Thermo¬ Mixed Clarity Tg(°C) MP(°C) (tanδ) plastic Ratio of Resin Novolak

Resin

SAN 20% Clear 113/111

MMA 20% 102/100

PCL 20% Clear 58/52

S/MAnh 20% Clear 116/108 imm-MMA 20% Clear 159/142

PC 20% Clear 152/127

PAR 20% Clear 195/142

Polysulfone 20% Clear 190/151

PPO 20% Clear 220/199

6T/6I 20% 127/116

6-Nylon 20% Clear 61.6/77.4

612-Nylon 10% Clear 53/63

PET 20% Clear

PBT 20% Clear 51/55

LCP 20% 335/300

PPS 10% Clear 115.3/97.2

POM 20% Clear

PEKK 20% Clear 161/146

In the table, Tg, MP, and tan delta represent mixtures of thermoplastic resin itself/Novolak. The first number is for the resin itself and the second number after the/ is the Novolak mixture. Example 2 Measurement of Mechanical Properties Each component was melt kneaded using a twin screw extruder

(TEM-35 manufactured by Toshiba), water cooled, and reduced to pellets with various compositions. The resultant pellets were used to mold 13 mm x 130 mm x

3.2 mm test pieces based on ASTM D-638.

The following mechanical properties were measured on the test pieces obtained:

Tensile Strength According to ASTM D-638

Elongation According to ASTM D-638 Flexural Modulus According to ASTM D-790 Notch Izod Impact Strength According to ASTM D-256

Tables 2-4 show the compositions of pellets produced and the results of measurement of the mechanical properties.

Table 2 - Polvbutylene Terephthalate/ All-Aromatic Polyamide Particle Svstems

Table 2

Example 1 Example 2 Example 3 Example 4

Compound (wt %) PBT 92.5 90.0 87.5 85.0

Novolak Resin 2.5 5.0 2.5 5.0 Kevlar (40 micrometers) 5.0 5.0 10.0 10.0

Mechanical Strength

Tensile Strength (kg cm²) ^' 660.4 703.6 660.0 696.5

Elongation (%) 6.7 6.4 4.6 3.7 Flexural Modulus (kg/mm²) 284.8 296.7 303.7 310.8

Impact Strength (kg.m cm) 3.2 2.6 2.6 2.6

Comparative Comparative

Example 5 Example 6 Example 1 Example 2

Compound (wt %) PBT 82.5 80.0 100 90.0

Novolak Resin 2.5 5.0 Kevlar (40 micrometers) 15.0 15.0 10.0

Mechanical Strength

Tensile Strength (kg/cm²) 650.4 668.8 591.3 595.4

Elongation (%) 3.1 2.8 49 5.7 Flexural Modulus (kg/mm²) 319.2 327.6 238.4 291.1

Impact Strength (kg.m/cm) 2.5 2.6 6.3 2.8

PBT: Polybutylene terephthalate KEVLAR: All-aromatic polyamide particles

The tensile strength and flexural modulus are shown to be improved in all the examples of this invention. It is also noted that increasing the Kevlar content from Examples 4 and 6 reduces the tensile strength, but improves the flexural modulus.

Table 3 - Polvphenylene Sulfide/ All-Aromatic Polvamide Particle Svstems

Table 3

Example 7 Example 8 Example 9 Example 10

Compound (wt %) PBT 93.5 92.0 88.5 87.0

Novolak Resin 1.5 3.0 1.5 3.0 Kevlar (40 micrometers) 5.0 5.0 10.0 10.0

Mechanical Strength

Tensile Strength (kg/cm²) 892.9 885.9 900.0 892.9

Elongation (%) 2.7 2.1 2.6 2.2 Flexural Modulus (kg mm²) 409.9 410.6 424.7 430.3

Impact Strength (kg.m/cm) 2.6 2.8 2.7 2.5

Comparative Comparative

Example Example 12 Example 3 Example 4 11

Compound (wt %) PBT 83.5 82.0 100 90.0

Novolak Resin 1.5 3.0 Kevlar (40 micrometers) 15.0 15.0 10.0

Mechanical Strength

Tensile Strength (kg/cm²) 850.8 836.7 871.8 759.3

Elongation (%) 2.3 2.1 2.5 2.7 Flexural Modulus (kg/mm²) 440.8 450.7 383.2 414.8

Impact Strength (kg.m/cm) 2.8 2.3 2.9 2.8

PPS: Polyphenylene sulfide

The tensile strength and flexural modulus improved when the matrix resin is polyphenylene sulfide, as in the case where polybutylene terephthalate is used.

Table 4 - Nylon 66/ All-Aromatic Polvamide Particles Svstems

Table 4

Example 13 Examplel4 Example 15 Example 16

Compound (wt %)

Nylon 66 88.0 86.0 88.0 80.0

Novolak Resin 2.0 4.0 2.0 10.0

Kevlar (40 micrometers) 10.0 10.0 - -

Kevlar (120 micrometers) - - 10.0 -

Kevlar (200 micrometers) ~ ~ 10.0

Mechanical Strength

Tensile Strength (kg/cm²) 900.0 928.1 801.5 414.8

Elongation (%) 3.5 3.6 2.2 0.9

Flexural Modulus (kg/mm²) 341.0 348.7 348.0 383.9

Impact Strength (kg.m/cm) 3.8 3.3 2.7 1.6

Comparatiave Comparative Comparative Comparative

Example 5 Example 6 Example 7 Example 8

Compound (wt %)

Nylon 66 100 90.0 90.0 90.0

Novolak Resin - - - -

Kevlar (40 micrometers) - 10.0 - -

Kevlar (120 micrometers) - - 10.0 -

Kevlar (200 micrometers) " _. 10.0

Mechanical Strength

Tensile Strength (kg/cm²) 892.9 885.9 773.4 365.6

Elongation (%) 14.6 4.1 2.2 0.9

Flexural Modulus (kg/mm²) 306.6 342.4 348.7 343.1

Impact Strength (kg.m/cm) 6.5 • 3.3 2.7 2.2

The tensile strength and flexural modulus are also improved when nylon 66 is used as the matrix resin, as in the cases where PBT and PPS were used. Examples 13 and 15 show that the smaller the Kevlar particle size, the more significant the improvement in tensile strength and the less reduction in elongation and impact strength.

The present invention which comprises adding all-aromatic polyamide particles or fibers along with a thermoplastic phenolic resin into a matrix resin improves mechanical properties without adversely affecting the sliding properties of the molded articles therefrom.

Claims

1. A resin composition comprising 99.8-30.0%) by weight of a matrix resin comprising a matrix resin comprising a thermoplastic resin which is compatible or semi-compatible with a thermoplastic phenolic resin, 0.1-30.0%o by weight of the thermoplastic phenolic resin, and 0.1 -40.0% by weight of all-aromatic polyamide particles or fibers.

2. A molded part made from the resin of Claim 1.