JP2011201990A - Polyamide resin pellet reinforced with long glass fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyamide resin pellet reinforced with long glass fibers, which is a material that hardly causes fall off of the continuous reinforcing glass fibers from the pellet and is excellent in strength, mechanical strength such as elastic modulus and impact strength and heat resistance such as heat distortion temperature.SOLUTION: The polyamide resin pellet reinforced with a long glass fiber comprises the reinforcing glass fibers that continue in the longitudinal direction of the pellet and are substantially arranged parallel to the longitudinal direction and contains 45-60 mass% reinforcing glass fibers. The polyamide resin is a crystalline polyamide resin, the relative viscosity (measured using 96 mass% concentrated sulfuric acid as a solvent at 25°C, 1 g/dl) is 1.6-2.1, the porosity of the polyamide resin pellet is ≤1.5%, and the tensile break elongation is ≥1.8% in a tensile test performed at a tensile speed of 2 mm/min using a no. 1 test piece of 4 mm thick prepared by injection molding of the pellet according to JIS K 7113.

Description

  The present invention is excellent in mechanical properties such as strength, elastic modulus and impact strength and heat resistance, and has a good impregnation property with a polyamide resin in glass long fibers, and has excellent handling properties in a molding process. It relates to resin pellets.

Development of long glass fiber reinforced polyamide resin molding materials using glass roving has been studied for a long time, but glass impregnation into glass fiber bundles is poor and the productivity of reinforced resin molding materials is poor. A short fiber reinforced polyamide resin molding material obtained by blending and kneading the chopped strands is widely used. However, in recent years, depending on the field of application, glass long fiber reinforced resin molding materials are potentially better than short fiber reinforced resin molding materials, such as mechanical properties such as strength, elastic modulus and impact strength, and heat distortion temperature. Development of glass long fiber reinforced resin molding materials has been promoted, focusing on the fact that heat resistance characteristics can be easily improved (Patent Documents 1 and 2).
Patent Document 1 uses a polyamide resin having a relatively high melt fluidity to suppress breakage of glass fibers during molding to suppress a decrease in the aspect ratio of the glass fibers, thereby achieving both impact resistance and rigidity of the molded product. I will try to let you. However, the melt impregnation of the resin into the glass fiber bundle at the time of pellet production is not sufficient, the productivity is low, there is a possibility that the glass fiber comes off or cracks from the pellet, and the handling property at the time of molding is low. It may get worse.
In addition, Patent Document 2 improves the physical properties of a molded article by using a polyamide resin obtained by copolymerizing a hexamethyleneisophthalamide unit with polyamide 66 to reduce the crystallization temperature and the degree of crystallization. And general-purpose polyamide resins such as polyamide 6 and polyamide 66 are not used.
Even for general-purpose polyamide resins such as polyamide 6 and polyamide 66, there is a demand for a long glass fiber reinforced polyamide resin molding material that has high productivity, excellent handling during molding, and can exhibit not only high rigidity but also high toughness. It has been.

JP 2003-25456 A JP 2005-263828 A

  Therefore, the present invention improves the impregnation of the crystalline polyamide resin into the continuous glass fiber bundle without reducing the productivity of the pellet production, and also the glass fiber detachment or the pellet that occurs in the molding process. It is an object to provide a good molded product by preventing defects such as cracks and maintaining the excellent mechanical strength and elongation (high toughness) of the long glass fiber reinforced polyamide resin molding material. is there.

  As a result of intensive studies to solve the above problems, the present inventors have improved the impregnation property between the continuous glass fibers of the crystalline polyamide resin by setting the relative viscosity of the crystalline polyamide resin to a specific range. The inventors have found that a molded article having extremely excellent toughness can be obtained, and have completed the present invention.

That is, the present invention
It is a glass long fiber reinforced polyamide resin pellet in which reinforced glass fibers are continuous in the length direction of the pellet and arranged substantially in parallel, and the content of the reinforced glass fiber is 45 to 60% by mass, A crystalline polyamide resin having a relative viscosity (measured at 25 ° C. and 1 g / dl using 96 mass% concentrated sulfuric acid as a solvent) of 1.6 or more and 2.1 or less, and the following porosity of the polyamide resin pellet is 1.5. The tensile fracture elongation when the No. 1 type test piece having a thickness of 4 mm is injection-molded according to JIS K7113 and the tensile test is performed at a speed of 2 mm / min is 1.8% or more. Characteristic long glass fiber reinforced polyamide resin pellets.
Porosity: 2.0 to 2.5 g of resin pellets were immersed in a beaker containing 100 ml of a 1 g / liter aqueous solution of a nonionic surfactant (23 ° C.), and then the beaker was placed on an ultrasonic cleaner for 10 minutes. After removing the resin pellet from the beaker and removing the moisture on the surface of the pellet, the mass is measured and calculated by the following formula.
Porosity (%) = (G1-G0) / G0 × 100
G1: Mass of pellet after immersion after removing water (g)
G0: pellet mass before immersion (g)

The long glass fiber reinforced polyamide resin pellet of the present invention is a matrix polyamide crystalline polyamide resin itself having a low degree of polymerization and inferior mechanical properties, and has a fast solidification rate and a negative effect on impregnation, The glass long fiber surface can be well covered to reduce the voids of the resin pellets, and because of its excellent adhesion to the glass long fiber, the glass long fiber has high reinforcement efficiency, strength, elastic modulus, impact strength, etc. A molded article having excellent mechanical strength can be formed. In particular, even if the glass fiber content is as high as 50% by mass, it can exhibit toughness that can stably exhibit a tensile elongation of 1.8% or more.
In addition, since the pellets of the present invention are less likely to fall out of glass fibers with respect to impact, vibration, friction, etc., it is possible to reduce molding problems such as clogging in the hopper dryer of the molding machine.

The present invention will be specifically described below.
The crystalline polyamide resin of the present invention is an aliphatic crystalline polyamide resin or a semi-aromatic polyamide resin having an acid amide bond (—CONH—) in the molecule. Specifically, ε-caprolactam, 6- Polymers or copolymers obtained from aminocaproic acid, ω-enantolactam, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 9-aminononanoic acid, α-pyrrolidone, α-piperidine, hexamethylenediamine, nonamethylenediamine , Polymers obtained by polycondensation of diamines such as undecamethylenediamine, dodecamethylenediamine, metaxylylenediamine, polymetaxylylene adipamide and dicarboxylic acids such as terephthalic acid, isophthalic acid, adipic acid, and sebacic acid Or a copolymer or a blend thereof DOO but it can not be construed as being limited thereto.
Specific examples include nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 610, nylon 612, nylon 6T, nylon 66T, nylon 66 / 6T, MXD6 and the like, and blends thereof. It is not limited to these. These crystalline polyamide resins are required to have a relative viscosity of 1.6 or more and 2.1 or less measured at 25 ° C. and 1 g / dl using 96 mass% concentrated sulfuric acid as a solvent. Further, the terminal carboxyl group concentration (CEG) of these crystalline polyamide resins is preferably 40 meq / kg or more and 200 meq / kg or less.

The relative viscosity of the crystalline polyamide resin (measured at 25 ° C. and 1 g / dl using 96 mass% concentrated sulfuric acid as a solvent) is 1.6 or more and 2.1 or less, preferably 1.8 or more and 2.1 or less. is there. In general, continuous glass fibers are wound in a roving shape by concentrating thousands of glass single fibers into one bundle. In order to obtain pellets that are excellent in mechanical strength and elongation and that have few glass fibers falling off due to impact, vibration, friction, etc., it is necessary to coat each single glass fiber with a resin. For that purpose, it is necessary to infiltrate the molten resin between each single glass fiber, but when the relative viscosity of the polyamide resin exceeds 2.1, the viscosity at the time of melting becomes high and the glass single fiber It is difficult for the resin to spread over and the impregnation property is insufficient. On the other hand, if it is less than 1.6, the viscosity at the time of melting is too low to be handled easily, and mechanical strength and impact strength as a molding material are also lowered.
The terminal carboxyl group concentration (CEG) of the crystalline polyamide resin is preferably 40 meq / kg or more and 200 meq / kg or less, more preferably 40 meq / kg or more and 120 meg / kg or less. When the terminal carboxyl group concentration exceeds 200 meq / kg, handling at the time of melting becomes difficult. When the terminal carboxyl group concentration is less than 40 meq / kg, the wettability between the reinforced glass long fiber and the crystalline polyamide resin decreases, and the surface treatment is performed with a carboxyl group-reactive silane compound. Even if it is a reinforced glass long fiber, the reactivity between the resin and the reinforced glass long fiber surface decreases, and the resulting pellet is prone to a problem that the reinforced glass long fiber falls off during molding, etc. Mechanical strength and impact strength as a material also decrease.
That is, in the process of impregnating the continuous glass fiber for reinforcement with the polyamide resin, the terminal carboxyl group of the polyamide resin in the molten state is attached to the carboxyl group-reactive silane compound attached to the continuous glass fiber for reinforcement or the continuous glass fiber. It reacts with a carboxyl group-reactive silane compound contained in the sizing agent. When the polyamide resin reacts with the silane compound, the polyamide resin and the continuous glass fiber are firmly bonded.

  In order to obtain a crystalline polyamide resin having a relative viscosity of 2.1 or less, an ultra-low viscosity crystalline polyamide resin having a relative viscosity of 2.1 or less is polymerized, or a relative viscosity of more than 2.1 is obtained. There is a method of cleaving a polyamide molecular chain using a thinning agent with a crystalline polyamide resin having a viscosity. As the viscosity reducer, aliphatic dicarboxylic acid, aromatic dicarboxylic acid, etc. are effective. Specifically, oxalic acid, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, terephthalic acid, etc. Can be mentioned. When the amount of addition is about 0.1 to 3 parts by mass with respect to 100 parts by mass of the crystalline polyamide resin and melt kneading, the relative viscosity of the present invention becomes 2.1 or less. Since the value of the relative viscosity varies depending on the type, it is necessary to conduct a preliminary experiment in advance to determine the amount of the thickener added.

  As described above, the crystalline polyamide resin in the present invention has a low relative viscosity and is not usually suitable for molding materials intended for high mechanical strength. In the present invention, however, the terminal carboxyl group concentration (CEG) ) In a specific range, it can be suitably used for a long glass fiber reinforced polyamide resin composition.

As described above, in the present invention, the crystalline polyamide resin penetrates well between the continuous glass fibers for reinforcement, and the polyamide resin and the continuous glass fibers for reinforcement are firmly bonded. And voids that are likely to be formed at the interface between the fibers can be remarkably reduced. The void at the interface between the resin and the fiber can be represented by a value called porosity. Specifically, after the long glass fiber reinforced polyamide resin pellet of the present invention is completely immersed in water containing a surfactant, bubbles on the surface of the pellet are removed using an ultrasonic cleaner or the like. Then, the immersed long glass fiber reinforced polyamide resin pellets are taken out, the surface water is removed, and the mass change rate before and after the immersion is expressed.
When the resin is not sufficiently impregnated between the continuous glass fibers for strengthening, the void at the interface between the resin and the fiber becomes large, and water penetrates into the void, so the mass change before and after immersion, that is, the porosity is large. Become.
In a long glass fiber reinforced polyamide resin pellet having a large porosity, since the void at the interface between the resin and the fiber becomes large, the handleability is extremely deteriorated, and there is a possibility that variations in physical properties may occur. For pellets with a high porosity, pipes that transport pellets to the molding machine due to impacts during transportation or repeated vibration and friction, cracking of the pellets, and continuous glass fiber bundles coming up on the surface of the pellets causing the fibers to fall off. Problems such as clogging of glass fibers and clogging of a filter of a hopper dryer of a molding machine occur.
The porosity of the long glass fiber reinforced polyamide resin pellets of the present invention is 1.5% or less, preferably 1.0% or less.

Although it does not specifically limit as a glass long fiber in this invention, The thing which melt-spun glass, such as E glass, C glass, A glass, S glass, and alkali-resistant glass, is made into the filament-like fiber. A fiber diameter of about 3 to 25 μm can be used, and a fiber diameter of 8 to 20 μm is preferable in terms of handleability.
The content rate of the glass long fiber in a glass long fiber reinforced resin pellet is 45-60 mass%, Preferably it is 45-54 mass%. Within this range, both high rigidity and high toughness with a tensile elongation of 2.0% or more can be achieved. If the content of the long glass fiber is less than 45% by mass, the reinforcing effect of the long glass fiber is poor, so that the mechanical strength is difficult to improve. If the content exceeds 60% by mass, the polyamide resin impregnated between the long glass fibers decreases. As a result, the penetration of the molten resin between the glass single fibers at the time of production becomes insufficient, making it difficult to improve the mechanical strength and increasing the dropout of the glass fibers from the pellets.

  The long glass fiber reinforced polyamide resin of the present invention has high strength and rigidity, and at the same time has a high toughness with a tensile elongation of 2.0% or more. Therefore, the molded product is destroyed even if an instantaneous impact is applied. The amount of plastic deformation is reduced even if a long-term and continuous load is applied without absorbing the impact.

The continuous glass fiber for reinforcement in the present invention is preferably one in which the surface of the glass fiber is treated with a carboxyl group-reactive silane compound. As the carboxyl group-reactive silane compound, any of a silane coupling agent, an epoxy coupling agent, a titanate coupling agent, an aluminum coupling agent, etc. can be used. A ring agent is preferred.
As for the adhesion rate of a coupling agent, 0.1-3.0 mass% is preferable, More preferably, it is 0.1-1.0 mass%. If the adhesion rate is less than 0.1% by mass, the effect of the coupling agent is not exhibited, and if it exceeds 3.0% by mass, it is not preferable from the viewpoint of economy and leads to an increase in the amount of gas generated during molding.

  In the present invention, the coupling agent is not only adhered to the surface of the continuous continuous glass fiber for reinforcement, but can also be added when the polyamide resin is melted. The addition method may be adhered to the surface of the polyamide resin pellets, or may be injected from the side feed port of the extruder.

The method for producing pellets of the long glass fiber reinforced polyamide resin composition of the present invention is based on a known pultrusion molding method (Japanese Patent Laid-Open No. 53-50279). With this drawing method, continuous glass fibers for reinforcement consisting of thousands of filaments are drawn, and the continuous glass fibers for reinforcement are impregnated into the continuous glass fibers for reinforcement, and then cut in a direction perpendicular to the direction in which the continuous glass fibers are drawn. To obtain pellets.
In the present invention, any method may be used for impregnating the bundle of continuous glass fibers for reinforcement with the crystalline polyamide resin. However, the polyamide resin heated and melted by a twin screw extruder or the like may be used on a bar, roll, die or the like. The most preferred method is to impregnate while opening a bundle of glass fibers.

  The glass long fiber reinforced polyamide resin pellets thus obtained have the same length as the pellets from which the glass fibers have been cut, and are present in a state of being arranged substantially parallel to the length direction. The length of the pellet at this time is 3 to 20 mm, more preferably 5 to 10 mm. When the length of the pellet is shorter than 3 mm, the pellet is easily broken along the fiber direction in the pellet, and when it is longer than 20 mm, hopper clogging or the like in the molding process is likely to occur and plasticization becomes difficult. The shape of the pellet is not particularly limited except for the length. For example, the cross-sectional shape of the pellet may be a circle, an ellipse, a quadrangle, a flat shape, etc. Close shape.

  The glass long fiber reinforced polyamide resin pellets of the present invention can be blended with other compounding agents, additives, and the like as necessary. For example, heat stabilizers, UV stabilizers, weather resistance improvers, antioxidants, flame retardants, antistatic agents, pigments, dyes, mold release agents, lubricants and other compounding agents and additives used in ordinary polyamide resins However, it is not limited to these.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.
The following polyamide 6 (PA6) and polyamide 66 (PA66) were used as the crystalline polyamide resin of the present invention.
As PA6 (1) Toyobo Co., Ltd. T-860 (relative viscosity 1.9)
(2) T-800 manufactured by Toyobo Co., Ltd. (relative viscosity 2.5)
As PA66 (1) A27 manufactured by BASF (relative viscosity 2.8)
(2) A27 added with adipic acid (relative viscosity 2.0)

The following were used as reinforcing fibers.
Continuous continuous glass fiber: ER2400T-448N / S manufactured by Nippon Electric Glass Co., Ltd. (epoxy coupling agent, adhesion rate 0.3 mass%)
Short glass fiber: CS03MA411 manufactured by Owens Corning
The following coupling agents were used.
Organosilane KBE903 manufactured by Shin-Etsu Chemical Co., Ltd.

Each physical property value was measured by the following test method.
(1) Measurement of relative viscosity 0.25 g of crystalline polyamide resin was dissolved in 25 ml of 96.3% sulfuric acid, 10 ml of this solution was placed in an Ostwald viscosity tube, measured at 25 ° C., and calculated from the following formula.
RV = t / t0
RV: Relative viscosity t: Fall time of sample solution t0: Fall time of solvent (2) Porosity Glass long fiber reinforced polymiad resin pellets were sampled in the range of 2.0 to 2.5 g. The sampled long glass fiber reinforced polyamide resin pellets were placed in a beaker into which 0.1 g of 100 ml of pure water and a surfactant (Kao Emazole L120V) was dropped, and the sample was completely immersed. The beaker was placed in an ultrasonic cleaner for 10 minutes, and then the long glass fiber reinforced polyamide resin pellets were taken out of the beaker, the moisture on the pellet surface was removed, mass measurement was performed, and the following formula was calculated.
Porosity (%) = (G1-G0) / G0 × 100
G1: Mass of pellet after immersion after removing water (g)
G0: pellet mass before immersion (g)
The porosity measured with non-reinforced polyamide resin pellets (T-800) was 0.06%.

Regarding the resin component, each raw material shown in Tables 1 and 2 was put into an extruder, melted and kneaded, and sent to a coating die. The temperature of the extruder and the coating die was 240 to 300 ° C., and the strand take-up speed was 10 m / min.
Comparative Example 4 was prepared by melt-kneading T-860 using a twin screw extruder and side-feeding short glass fibers.

The pellets of Examples and Comparative Examples were subjected to physical property evaluation by injection molding of test pieces in accordance with ISO 294-1. The physical property evaluation method is as follows.
Tensile strength, elongation ISO 527
Flexural strength, flexural modulus: ISO 178
Charpy impact strength: ISO 179 / le A

Each example of the present invention and each comparative example were charged with 5Kg of pellets for each level into the hopper of the injection molding machine, all of the input pellets were molded, and the state of the hopper after completion of molding was confirmed. Judged.
○: State in which almost no glass fiber is seen on the hopper surface. Δ: State in which several glass fibers are scattered on the hopper surface. ×: State in which several tens or more glass fibers remain on the hopper surface.

In Examples 1 and 2, glass fibers having a high degree of resin impregnation and high physical properties were obtained. On the other hand, in Comparative Example 1 and Comparative Example 2 using PA6 and PA66 having a high relative viscosity and a low terminal carboxyl group concentration, the porosity is high and the glass fiber is easily dropped, and after molding, the hopper surface of the molding machine There were traces of reinforcing fibers remaining in the pellets and falling off the pellets. Even in Comparative Example 3 in which the content of the reinforcing fibers was high, the porosity was too high, and the glass fibers were likely to fall out, and a large number of reinforcing fibers remained in the hopper after completion of molding.
On the other hand, in Example 3 in which adipic acid was added to the same polyamide 66 as in Comparative Example 2 to lower the viscosity, the resin impregnation property increased and the porosity decreased, and many glass fibers dropped out into the hopper after molding. None and high physical properties were obtained.
In Comparative Example 4 reinforced with short glass fibers, the porosity was low, but the physical properties did not reach the glass long fiber reinforced material.

In the present invention, glass fibers are less likely to fall off due to impact, vibration, friction, etc. on the pellets, thus reducing molding problems such as clogging in the hopper dryer of the molding machine, and high strength and high impact resistance. The material is provided. Therefore, it can be developed in fields centering on metal replacement, such as automobile exterior materials, breaker cover materials that require high material strength, and PC casings that require high strength due to its thin wall thickness, contributing to the industry. It is great to do.

Claims (2)

It is a glass long fiber reinforced polyamide resin pellet in which reinforced glass fibers are continuous in the length direction of the pellet and arranged substantially in parallel, and the content of the reinforced glass fiber is 45 to 60% by mass, A crystalline polyamide resin having a relative viscosity (measured at 25 ° C. and 1 g / dl using 96 mass% concentrated sulfuric acid as a solvent) of 1.6 or more and 2.1 or less, and the following porosity of the polyamide resin pellet is 1.5. The tensile fracture elongation when the No. 1 type test piece having a thickness of 4 mm is injection-molded according to JIS K7113 and the tensile test is performed at a speed of 2 mm / min is 1.8% or more. Characteristic long glass fiber reinforced polyamide resin pellets.
Porosity: 2.0 to 2.5 g of resin pellets were immersed in a beaker containing 100 ml of a 1 g / liter aqueous solution of a nonionic surfactant (23 ° C.), and then the beaker was placed on an ultrasonic cleaner for 10 minutes. After removing the resin pellet from the beaker and removing the moisture on the surface of the pellet, the mass is measured and calculated by the following formula.
Porosity (%) = (G1-G0) / G0 × 100
G1: Mass of pellet after immersion after removing water (g)
G0: pellet mass before immersion (g) The glass fiber reinforced polyamide resin pellet according to claim 1, wherein the reinforced glass fiber is treated with a carboxyl group-reactive silane compound.