KR0158079B1 - Polyamide resin composition - Google Patents

Abstract

The present invention relates to a polyamide resin composition, and more particularly, to a gasoline which is an automobile fuel such as a delivery pipe by being made of a specific composite polyamide resin and an organic nucleating agent in the form of a glass fiber and a phosphate metal salt treated with a coupling agent. The present invention relates to a polyamide resin composition which, when applied to a part in direct contact with, has excellent mechanical strength and gasoline resistance even under thermally intense conditions.

Description

Polyamide Resin Composition

The present invention relates to a polyamide resin composition, and more particularly, to a gasoline which is an automobile fuel such as a delivery pipe by being made of a specific composite polyamide resin and an organic nucleating agent in the form of a glass fiber and a phosphate metal salt treated with a coupling agent. The present invention relates to a polyamide resin composition which, when applied to a part in direct contact with, has excellent mechanical strength and gasoline resistance even under thermally intense conditions.

The delivery pipe is an engine peripheral part, and since the conventional delivery pipe is manufactured mainly by aluminum die casting method, the manufacturing process is complicated and the weight of the product is increased. As the temperature increased, the internal pressure in the fuel system increased as a whole, which lowered engine efficiency and had various problems such as environmental problems caused by gasoline emission.

Therefore, in order to simplify the manufacturing process and reduce the weight of the delivery pipe, as well as to improve engine efficiency and prevent gasoline emission, it is desirable to apply the material as plastic, which should be considered first for plasticizing the delivery pipe. Mechanical durability, that is, strength and stiffness by replacing metal materials, in addition to impact resistance and vibration resistance of the driving of the car should also be considered. In addition, since the delivery pipe is always filled with gasoline fuel in the pipe, the metal replacement material should be a material that is resistant to gasoline, that is, a material that minimizes the amount of gasoline emitted to the outside through the inner wall of the pipe.

According to such a request, polyamide resin, which is a kind of engineering plastic, can be used as a resin that can replace the conventional metal material of the delivery pipe. Conventional polyamide resins have a high binding point and excellent mechanical strength because they contain amide groups with high binding strength in the molecule itself. They are widely used in engineering plastics and are widely applied to parts of automobiles and electric and electronic products. It is becoming.

In particular, with the recent trend of lightening of automobiles, the demand for automobile parts is rapidly increasing, and this trend requires not only basic advantages of polyamide resin but also additional characteristics, so that development of polyamide materials having new characteristics is very demanding. It is actively underway.

When the conventional polyamide resin is applied to automobile parts, various polyolefin resins are mixed with the polyamide resin, and the polyolefin resin is present inside the product in the form of fibers or plates, so that there are several layers having different properties in the thickness direction of the product. Designing to have resistance to gasoline penetration or permeation is the most common manufacturing technique. Also, by injecting a polar resin such as polyvinylacetate into polyamide, it causes greater resistance to permeation of nonpolar gasoline. Techniques such as increasing resistance to gasoline have been proposed. However, in such a method, a problem of deterioration in thermal stability or mechanical strength at high temperature is caused by input of a component having a weak thermal stability, and thus there is a limit in applying to a component near the engine. Therefore, in order to improve thermal stability, an attempt was made to improve heat deformation temperature and flexural strength by adding a reinforcing agent such as glass fiber or mineral. However, when these are added, an effective multilayer structure having excellent permeability is destroyed, which can be obtained from an unreinforced material. Can't expect gasoline.

The parts that are mainly made of glass fiber reinforced polyamide resin are vulnerable to the penetration of gasoline. Firstly, gasoline vapor is generated due to the gap of interface between glass fiber and polyamide resin. Diffusion, and second, because gasoline penetrates and is delivered to the amorphous portion of the polyamide resin.

Among these factors, the poor adhesion of the interface can be confirmed by the increase in weight or decrease in strength due to the infiltration of gasoline. The second factor is the increase in the degree of crystallinity of the polyamide resin part using a crystal nucleating agent. The validity of the hypothesis was confirmed from the result of increasing gender.

In addition, during this experiment, it was confirmed that the resistance to gasoline was improved by increasing the injection speed even at the same resin temperature even when the temperature of the resin was slightly lower at the same composition. It has been found that the orientation of glass fiber in the common parts where the resin flows in the direction perpendicular to the increase in the resistance to gasoline compared to the case in which the orientation is slightly decreased. In order to increase the degree of orientation of the glass fiber in the resin itself, various experiments were conducted.

To improve the viscosity of polyamide resin and to increase the orientation of glass fiber, experiments were conducted to improve the viscosity using various additives that can react with amines or carboxyl ends of polyamide. The effect was not shown, which was concluded by the effect of reducing the crystallization of the polyamide resin moiety and the penetration of gasoline into the amorphous moiety due to the reaction of the molecular terminal. The present invention has been completed by the conclusion that the use of a plurality of different polyamide resins in combination is the most useful method of improving the resistance to gasoline.

The inventors of the present invention have conducted research as described above to solve the problem of the lack of resistance to solubility when adding a reinforcing agent such as glass fiber to impart thermal stability to the polyamide resin as described above. By using polyamide resins in combination, the degree of orientation of the glass fibers was increased to develop a polyamide resin composition having improved solin resistance.

It is an object of the present invention to provide a polyamide resin composition which can simultaneously exhibit excellent mechanical strength and gasoline resistance even in an engine room of a vehicle or in extremely thermal conditions.

Hereinafter, the present invention will be described in detail.

The present invention relates to a polyamide resin composition comprising a glass fiber and an organic nucleating agent added to a polyamide resin, wherein 60 to 70% by weight of a polyamide-6 resin having a relative viscosity of 2.2 to 2.8 at room temperature and a relative viscosity of 3.2 to 3.6 25 to 60 parts by weight of glass fiber, organonucleating agent based on 100 parts by weight of polyamide resin consisting of 20 to 30% by weight of phosphorus polyamide-6 resin and 3 to 10% by weight of polyamide-6,6 resin having a relative viscosity of 2.5 to 3.5 It is characterized by consisting of 0.03 to 1.0 parts by weight.

Referring to the present invention in more detail as follows.

The present invention provides a polyamide resin composition for delivery pipes in which mechanical strength is enhanced by adding glass fibers, and at the same time, improving the gasoline resistance. In the present invention, the viscosity of the polyamide resin is adjusted to improve the gasoline resistance. Use in combination.

Here, the polyamide-6 resin having a relative viscosity of 3.2 to 3.6 is a component having a higher polymerization degree than the general polyamide resin, and increases the viscosity of the final resin composition to assist the orientation of the glass fibers, while also taking up the largest proportion of the resin components. Good compatibility with polyamide-6 resin having a viscosity of 2.2 to 2.8 does not cause a decrease in physical properties.

If the content of the polyamide resin component having a relatively high viscosity (relative viscosity 3.2 to 3.6) is less than 20% by weight based on the total polyamide resin composition, the effect of improving the required viscosity is small, which does not greatly help the orientation of the glass fiber. Therefore, it is difficult to expect the effect of improving the resistance to water resistance, and if the content exceeds 30% by weight, the viscosity of the overall resin is greatly increased, so it is difficult to show excellent interfacial properties at the interface with the reinforcing agent when the reinforcing agent such as glass fiber is added. , The physical properties of the final injection-molded product can be lowered by increasing the viscosity, and in order to solve this problem, it is necessary to adjust the injection temperature at the time of injection, thereby lowering the viscosity of the resin composition. it's difficult.

In addition, since a small amount of polyamide-6,6 resin has a higher crystal melting point and higher crystallization temperature at cooling than polyamide-6 component, it exhibits a rapid solidification and crystallization rate at the surface of the mold during injection, thus making the surface of the product very clean. The crystallinity is relatively high, and the glass fiber is prevented from appearing on the surface, thereby exhibiting a very high gasoline resistance in contact with gasoline.

Here, when the content of the polyamide-6,6 resin is less than 3% by weight based on the total resin composition, the effect of improving the viscosity is small, so that it is not very helpful in the orientation of the glass fiber, and thus it is difficult to expect the effect of improving the resistance to gasoline. When the percentage is exceeded, the viscosity of the overall resin is greatly increased, and when the reinforcing agent such as glass fiber is added, it is difficult to show excellent interface characteristics at the interface with the reinforcing agent, and the physical properties of the product are lowered due to the increase in viscosity.

When the content of polyamide-6 resin having a relatively low viscosity (2.2 to 2.8) is less than 60% by weight, the effect of improving the viscosity is small, so that it is not very helpful in the orientation of the glass fiber, and thus it is difficult to expect the effect of improving the gasoline characteristics. When the content of the resin exceeds 70% by weight, the viscosity of the overall resin is greatly increased, so that when the reinforcing agent such as glass fiber is added, it is difficult to exhibit excellent interfacial properties at the interface with the reinforcing agent, and the physical properties of the product decrease due to the increase in viscosity.

In addition, the glass fiber which can be used in the present invention generally uses a product whose surface is treated with an aminosilane-based coupling agent so as to have excellent interfacial adhesion with the polyamide resin when used in a conventional polyamide resin, and the length is about It is cut into about 3mm and has a diameter of about 10 to 15 µm. In the selection of glass fibers, there is no limitation as long as the interface adhesion is excellent, and this interface adhesion can be easily determined by observing the impact fracture surface.

The reason why the orientation of the glass fibers affects the penetration or permeation of gasoline is that in the observation of very fine structures, the interface between the polyamide resin and the glass fiber treated with the coupling agent is usually bonded by a chemical reaction. Molecules bound by chemical bonds are difficult to form crystals, and of course, the gasoline vapor diffusion rate is relatively fast at the interface of the amorphous, making it vulnerable to gasoline penetration. However, when surface-treated glass fibers are used so that no chemical bonds exist, gaps are formed at the interface between the glass fibers and the polyamide resin, and gasoline vapors are hardly resisted and are enlarged with little resistance. there is a problem. Therefore, even if it is accompanied by a chemical reaction, it is necessary to use the surface-treated glass fibers.

In this situation, when the interface of the glass fiber becomes the penetration path of gasoline, the orientation of the glass fiber decreases and the velocity of gasoline penetration in the thickness direction when the glass fiber exists in the thickness direction is the longitudinal direction of the product in which the glass fiber is perpendicular to the thickness due to the orientation. Since the gasoline penetrates faster than the gasoline penetration rate in the thickness direction, the longitudinal orientation of the glass fiber is a very important factor.

And, the typical characteristic of the orientation of the glass fiber is the difference in the shrinkage in the flow direction and the perpendicular direction of the flow, in the case of the conventional glass fiber 50% reinforced polyamide-6 shrinkage in the flow direction and the vertical direction of the flow is about In the case of increasing the orientation of the glass fiber as in the present invention, the shrinkage rate decreases in the flow direction to about 0.22% and about 0.38%, and increases in the thickness direction perpendicular to the flow. It shows anisotropy. Therefore, the observation of this phenomenon can indirectly recognize the orientation of the glass fibers very accurately, and in the case of long products such as delivery pipes, the thickness of the glass fibers is usually the direction perpendicular to the flow. It can be seen that it produces a very effective prevention effect for.

In addition, the organic nucleating agent used in the present invention is in the form of a phosphate-based metal salt, showing excellent physical properties and resistance to gasoline resistance compared to conventional inorganic nucleating agents.

In general, the nucleating agent may be classified into inorganic type such as titanium dioxide (TiO ₂ ), talc (Talc), silica, and organic nucleating agent such as aliphatic ester compound, and organic nucleating agent component in the form of phosphate metal salt used in the present invention. In order to simultaneously improve the mechanical strength and resistance to gasoline, the organic nucleating agent in the form of phosphate metal salt shows the best effect.

In the case of the inorganic nucleating agent, the nuclei produced by the dispersibility of the inorganic nucleating agent are very uneven in size and distribution, so that the impact strength is very poor. However, in the case of the organic nucleating agent in the form of phosphate metal salt, the degree of crystallization of the final resin is excellent. It keeps the crystal size very small and uniform while increasing it effectively, thereby increasing the crystallinity of the pure resin part without glass fiber and reducing the amorphous part through which gasoline can easily penetrate. Therefore, since the gasoline vapor is complicated to diffuse, the gasoline permeation is very difficult to penetrate, and the gasoline resistance is rapidly improved.

In addition, the organic nucleating agent in the form of phosphate metal salt is a very effective nucleating agent in the present invention because it can not only express the effect of improving the physical properties such as impact strength of the polyamide resin composition at an excellent level but also obtain an excellent effect even at a small dosage.

Organic nucleating agents in the form of phosphate metal salts that can be used in the present invention include sodium 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate or sodium di (4-tert-butylphenyl) phosphate The most suitable amount is 0.03 to 10 parts by weight based on 100 parts by weight of the total polyamide resin composition. If the content is less than 0.03 parts by weight, it is difficult to expect improvement in crystallinity, and when the content exceeds 1.0 parts by weight In addition, it is not economically effective to increase the degree of crystallization in proportion to the amount of, and there is a concern that thermal stability may be degraded due to excessive input of organic nucleating agents.

In the present invention, in addition to the above composition, a conventional release agent in the form of a metal salt such as stearic acid or lauric acid, various heat-resistant or antioxidants to remove peroxides or radicals generated during oxidative pyrolysis, or absorb or A weatherproofing agent, an antistatic agent or a coloring agent such as a pigment or carbon black, or a plasticizer may be added.

As described above, since the polyamide resin composition of the present invention uses a plurality of polyamide resins having different viscosity behaviors, the surface is clean, and the longitudinal orientation of the glass fibers is excellent, so that gasoline is removed from the interface between the glass fibers and the polyamide resin. It exhibits very high resistance to penetration and permeation. It also reduces the ratio of non-crystalline part and crystal size in the resin part, thus extending the path of gasoline penetrating and permeating into the resin part. In particular, the highly crystalline polyamide-6,6 layer present on the surface minimizes the display of glass fibers, which is excellent in gasoline resistance since it directly inhibits the amount of gasoline in direct contact with the inside of the part. . In addition, the resin composition of the present invention can be applied as an induction pipe through which fuel of an automobile passes. Such products generally have a very long length compared to the diameter or width, so that the molding shrinkage ratio in the longitudinal direction is normal. Since it is lower than glass fiber reinforced materials, it also has the advantage of being very advantageous in the design of products.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited by the Examples.

Example 1

70% by weight of polyamide-6 (A ₁ ) having a relative viscosity of 2.6 by formic acid method, 23% by weight of polyamide-6 (A ₂ ) having a relative viscosity of 3.4 and polyamide-6 having a relative viscosity of 2.6 by sulfuric acid method, 6 (A ₃ ) to a composite polyamide resin composed of 7% by weight of glass fiber (B) having a diameter of 13 μm, a length of 3 mm, and a surface treated with an aminosilane-based coupling agent, based on 100 parts by weight of the resin composition. 40 parts by weight, 0.3 parts by weight of sodium di (4-tert-butylphenyl) phosphate (C ₁ ) as an organic nucleating agent based on 100 parts by weight of the resin composition, and N, N'-hexamethylene as a heat-resistant agent as other additives. 0.3 parts by weight of -bis- (3,5-di-tert-butyl-4-hydroxyamide) to 100 parts by weight of the resin composition and 100 parts by weight of ethylene-bis-stearimide as a release agent. 0.2 parts by weight of the mixture, and using a twin screw thermomelting kneading apparatus The resin composition was prepared at 270 ° C. After discharging the spaghetti through the die and cutting it with a cutter while cooling, compounding the chip was prepared, drying the moisture for 6 hours in a dehumidifying hot air dryer at 85 ° C., and then in an injection molding machine having a clamping force of 150 tons. Injection molding was applied at a resin temperature of 280 ° C and a mold temperature of 90 ° C.

[Examples 2 to 5 and Comparative Examples 1 to 11]

The content ratio of the polyamide resin composition was performed in the same manner as in Example 1, except that the content ratio was changed as shown in Table 1 below.

Experimental Example 1

According to Examples 1 to 5 and Comparative Examples 1 to 11, tensile strength, flexural strength, flexural modulus, impact strength, mold shrinkage ratio, and solubility resistance of the injection molded specimens were measured, and the results are shown in Table 2 below. As shown.

Here, tensile strength was measured according to ASTM D-638, flexural strength and flexural modulus were measured according to ASTM D-790, and impact strength was measured at room temperature (23 ° C) based on ASTM D-256 (Izod). Notched).

The shrinkage rate is a percentage of the shrinkage in the direction perpendicular to the flow direction using disc specimens with a thickness of 3.2 mm and a diameter of 100 mm. O indicates a weight change of within ± 0.5%, Δ represents a weight change of ± 0.5 to 0.75%, and x represents a weight change of ± 0.75% or more.

Experimental Example 2

The product weight, manufacturing process, and productivity of the conventional aluminum delivery pipe and the delivery pipe prepared from the composition obtained in Example 1 of the present invention were compared, and the results are shown in Table 3 below.

From the results of Experimental Example 1, it can be seen that the polyamide resin composition of the present invention not only has excellent mechanical strength but also improved solin resistance. From the results of Experimental Example 2, the plastic delivery pipe of the present invention is a delivery pipe of a conventional metal material. The weight is reduced by about 47% and the process is shortened to improve workability.

Claims (3)

In a polyamide resin composition obtained by adding a glass fiber and an organic nucleating agent to a polyamide resin, 60 to 70% by weight of a polyamide-6 resin having a relative viscosity of 2.2 to 2.8 at room temperature and a polyamide having a relative viscosity of 3.2 to 3.6 25 to 60 parts by weight of glass fiber and 0.03 to 1.0 of organic nucleating agent with respect to 100 parts by weight of polyamide resin consisting of 20 to 30% by weight of -6 resin and 3 to 10% by weight of polyamide-6,6 resin having a relative viscosity of 2.5 to 3.5 A polyamide resin composition comprising a weight part added. The polyamide resin composition according to claim 1, wherein the glass fiber has a length of 3 mm and a diameter of 10 to 15 µm surface-treated with an aminosilane-based coupling agent. The polyamide according to claim 1, wherein the organonucleating agent is sodium di (4-tert-butylphenyl) phosphate or 2,2'-methylenebis (4,6-di-tert-butylphenyl) phosphate Resin composition.