JPH07109421A - Aromatic polyamide resin composition - Google Patents

Abstract

PURPOSE:To obtain the subject resin composition which is moldable at a low mold temp., gives a void-free molding, and is excellent in releasability, moldability including stability during residence, mechanical strength, etc. CONSTITUTION:A fibrous reinforcing filler is incorporated into a polyamide resin composition comprising 95-20wt.% MXD-6 nylon (a) and 5-80wt.% amorphous polyamide (b) having a glass transition temp. of 100 deg.C or higher (the sum of (a) and (b) being 100wt.%, in an amount of 5-50wt.% based on the whole composition.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aromatic polyamide resin composition, and more particularly to an aromatic polyamide resin composition prepared by mixing MXD-6 nylon with a fibrous reinforcing filler.

[0002]

2. Description of the Related Art Conventionally, as a resin composition excellent in mechanical strength and dimensional stability, MXD-6 nylon, modified 6T-nylon having terephthalic acid and an aliphatic diamine component as main constituent units, and glass fiber It is known that a reinforcing fiber such as or potassium titanate fiber is blended.

[0003] These resin compositions use a crystalline resin as a matrix resin and can exhibit predetermined physical properties only after being crystallized. However, since these resin compositions generally have a slow crystallization rate, crystallization does not proceed at a mold temperature of 60 ° C. to 100 ° C. used for ordinary molding, and a mold temperature of 120 ° C. to 150 ° C. is required. It was However, a mold temperature of 120 ° C. to 150 ° C. causes problems such as burrs and a long molding cycle. Further, there is a problem that as the thickness of the molded product becomes thinner, it becomes difficult to crystallize even if the temperature is raised.

Therefore, when molding these resin compositions, after molding at a mold temperature of 60 ° C. to 80 ° C., 1
A molding method in which re-heating (annealing treatment) at 20 ° C. to 150 ° C. is performed to crystallize is generally adopted.

[0005]

However, according to such a method, there arises a problem that deformation or warpage occurs in the entire molded product due to the annealing treatment, and bubbles or swelling occur on the surface of the molded product. . In order to solve these problems, methods of using a crystallization nucleating agent and a crystallization accelerator have been studied, but the above problems have not been solved yet.

On the other hand, in order to solve such a problem, a method of using a polyhexamethylenediamide resin having a relatively high crystallization rate may be considered, but these nylon resins have sufficient mechanical properties even if they are blended with reinforcing fibers. It has the drawbacks that no strength can be obtained and the physical properties are greatly reduced by water absorption.

Further, a method of using amorphous polyamide as a matrix resin can be considered, but these polyamide resins are a group of polyamide resins in which polymer crystallization hardly occurs or the crystallization rate is very small. On the other hand, although relatively high physical strength is easily obtained, there are drawbacks such as chemical resistance, particularly weakness against alcohol, and a decrease in glass transition temperature (Tg) due to absorption of water and heat resistance.

Further, in a composite material obtained by filling a fibrous reinforcing filler in an engineering plastic such as a POM (polyoxymethylene) resin or a PBT (polybutylene terephthalate) resin, a sufficiently satisfactory result in mechanical strength and shape accuracy can be obtained. Not not.

The object of the present invention is to solve the above-mentioned problems of the prior art and to produce ultra-thin molded products such as gear parts for watches and micro molded products at a low mold temperature without generating bubbles or voids. An object of the present invention is to provide an aromatic polyamide resin composition that can be molded and is excellent in molding stability such as releasability and retention stability, and in mechanical strength and dimensional stability.

[0010]

MEANS TO SOLVE THE PROBLEMS As a result of intensive studies conducted by the present inventors to solve the above-mentioned conventional problems, the MXD
A resin composition prepared by blending -6 nylon with an amorphous polyamide having a glass transition temperature of 100 ° C. or higher is used as a matrix resin, and a fibrous reinforcing filler is blended into the resin composition, so that the mold temperature can be kept as usual. To make it hot
Alternatively, it has been found that an aromatic polyamide resin composition having excellent mechanical strength and dimensional stability can be obtained without annealing, and the present invention has been completed.

That is, the aromatic polyamide resin composition of the present invention comprises 95 to 20% by weight of MXD-6 nylon (a).
And 5 to 80% by weight of the amorphous polyamide (b) having a glass transition temperature of 100 ° C. or higher (the sum of (a) and (b) is 1).
It is characterized in that the fibrous reinforcing filler (B) is added to the polyamide resin composition (A) consisting of 100% by weight) in an amount of 5 to 50% by weight of the entire resin composition.

[Polyamide Resin Composition (A)] MXD-6 Nylon MXD-6 nylon constituting the polyamide resin composition (A) which is the matrix resin in the present invention is xylylenediamine and α having 6 to 12 carbon atoms. , Ω-linear aliphatic dibasic acid is subjected to polycondensation reaction. here,
The xylylenediamine is mainly composed of metaxylylenediamine, and may be metaxylylenediamine alone, or a proportion of metaxylylenediamine of 60% or more and paraxylylenediamine of 40% or less. It may be mixed with. Examples of the α, ω-linear aliphatic dibasic acid include adipic acid, suberic acid, sebacic acid, undecanedioic acid, dodecanedioic acid and the like. Among these dibasic acids, adipic acid is particularly preferable in consideration of various characteristics of the obtained molded product. These dibasic acids can be used alone or in combination of two or more. Moreover, the polycondensation reaction of xylylenediamine and a dibasic acid can be performed by a conventionally known method.

Amorphous Polyamide In the present invention, an amorphous polyamide having a glass transition temperature of 100 ° C. or higher is used. Glass transition temperature is 1
If it is less than 00 ° C, the heat resistance is poor and the ambient temperature of the molded product is limited.

As such an amorphous polyamide, 3
A lactam having a member ring or more, a polymerizable ω-aminocarboxylic acid, and a polyamide obtained by polycondensation of a diamine and a dicarboxylic acid can be used. Specific examples of the monomer include ε-caprolactam and ω-lauro. Lactams such as lactam, 6-aminocaproic acid, 1
1-aminoundecanoic acid, 12-aminododecanoic acid, p
-Aminocarboxylic acids such as aminobenzoic acid, tetramethylenediamine, hexamethylenediamine, undecamethylenediamine, dodecamethylenediamine, 2,2,4 /
2,4,4-trimethylhexamethylenediamine, 5-
Methylnonamethylenediamine, m-xylenediamine,
p-xylenediamine, 1,3-bis (aminomethyl)
Cyclohexane, 1,4-bis (aminomethyl) cyclohexane, bis (4-aminocyclohexyl) methane,
1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane, 4,4'-diamino-3,3'-dimethyldicyclo-hexylenemethane, 2,2-bis (4
-Aminocyclohexyl) propane, bis (aminopropyl) piperazine, bis (aminoethyl) piperazine and other diamines, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecane 2 acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, etc. And dicarboxylic acids thereof.

Any monomer composition may be used as long as it has a glass transition temperature, but preferred specific examples include terephthalic acid, isophthalic acid, hexamethylenediamine and 4,4'-diamino-. Examples thereof include polycondensates of 3,3′-dimethyldicyclo-hexylenemethane, and polycondensates of terephthalic acid, isophthalic acid, and hexamethylenediamine.

The molecular weight of the amorphous polyamide used in the present invention is not particularly limited,
The relative viscosity when measured using m-cresol at a concentration of 1 g / dl and 25 ° C. is preferably within the range of 1.2 to 5.0, more preferably within the range of 1.3 to 4.0. Is. If the relative viscosity is too high, the flowability of the resin composition deteriorates, which may cause a problem in moldability, and the toughness represented by Izod impact strength decreases, which is not preferable. Further, if the relative viscosity is too low, the mechanical strength of the resin composition is poor, which is not preferable.

The amorphous polyamide used in the present invention can be produced by a known method such as solution polymerization, melt polymerization or interfacial polymerization. It is also possible to use a known solid-phase polymerization method in combination to obtain a polyamide having a higher molecular weight. A melt polymerization method is used as a general method.

[0018] MXD-6 nylon and amorphous polyamide
Mixing ratio In the present invention, MX constituting the polyamide resin (A)
The blending ratio of the D-6 nylon (a) and the amorphous polyamide (b) is 5 to 80% by weight of the amorphous polyamide with respect to 95 to 20% by weight of MXD-6 nylon. MXD-
If the blending ratio of 6-nylon is less than 20% by weight, the mechanical strength is poor and the chemical resistance is poor. On the contrary, when the blending ratio of MXD-6 nylon exceeds 95% by weight, the effect of improving the molding stability due to crystallization becomes not remarkable.

[Fibrous Reinforcing Filler (B)] The fibrous reinforcing filler used in the present invention is not particularly limited, and various fibrous substances usually used for reinforcement can be used. Specifically, potassium titanate whiskers, metal borate whiskers, SiC whiskers, alumina whiskers, silicon nitride whiskers, zinc oxide whiskers having a three-dimensional structure, CaO.SiO.
Examples thereof include wollastonite or zonotolite, which is a fibrous material containing ₂ as a main component, and micro carbon fiber. From the aspects of fluidity, strength, etc., potassium titanate whiskers are particularly preferable.

The potassium titanate whiskers have the general formula K
₂ O · n (TiO _2−x ) (where n = an integer of 2 to 12 and X is 0 or a decimal number of 1 or less), for example, n = 8 and X = 0. Examples thereof include potassium 8-titanate whiskers, potassium hexatitanate whiskers in which n = 6 and X = 0, and potassium tetratitanate whiskers in which n = 4 and X = 0. These can be used alone or in combination. Examples of commercially available products include "Tismo"
(Trade name, manufactured by Otsuka Chemical Co., Ltd.) can be used.
This has an average fiber diameter of 0.2 to 0.5 μm and a fiber length of 1.
It is a high-strength single crystal whisker of 0 to 20 μm. Such potassium titanate whiskers may be used untreated, but if necessary, a usual coupling agent, for example, a silane coupling agent such as epoxysilane, aminosilane, acrylsilane or a titanate coupling agent. It may be surface-treated with a coupling agent before use.

As the boric acid metal salt type whiskers, whiskers generally represented by aA _x O _y · bB ₂ O ₃ (A is a metal atom) can be used. Examples thereof include aluminum borate whiskers in which A is Al in the above formula, magnesium borate whiskers in which A is Mg, and the like. Commercially available aluminum borate whiskers, for _{example, 9Al 2 O 3 · 2B 2} O 3 ALBOREX G (trade name, manufactured by Shikoku Chemicals Corp.) represented by have an average fiber diameter of this product is 0.5~1μm Yes,
The average fiber length is 10 to 30 μm.

Wollastonite is a fibrous substance containing CaO.SiO ₂ as a main component and is a naturally occurring white needle crystal. As a wollastonite, the aspect ratio is 6
60% by weight or more, preferably 80% by weight or more of the above components, and 80% by weight or more of components having a fiber diameter of 5 μm or less,
Fine and long wollastonite containing 95% by weight or more is preferable.

Zonotorite is composed of 6CaO ・ 6SiO ₂・
A synthetic fibrous calcium silicate represented by H ₂ O,
For example, zonotolite manufactured by Ube Industries is known.
This has an average fiber diameter of 0.5 to 1 μm and an average fiber length of 2 to
It is 5 μm and the aspect ratio is 2 to 15.

[Blending Ratio of Polyamide Resin Composition (A) and Fibrous Reinforcing Filler (B)] In the present invention, the fibrous reinforcing filler (B) is added to the polyamide resin (A).
Is mixed so as to be 5 to 50% by weight of the entire resin composition. The blending ratio of the fibrous reinforcing filler (B) is 5% by weight.
If it is less than the above range, the reinforcing effect becomes poor, and a resin composition having sufficient mechanical strength cannot be obtained. On the other hand, if it exceeds 50% by weight, the effect of improving the physical properties is small as compared with the mixing ratio, and compounding becomes difficult, which is not preferable.

[Other Compounding Agent] In the present invention, in addition to the above-mentioned compounding materials, a heat stabilizer, a processing stabilizer, a release agent, etc. may be compounded, and as the heat stabilizer, a hindered phenol-based heat stabilizer is used. Agents are preferred, phosphorus-based processing stabilizers are preferred as processing stabilizers, and fatty acid ester-based release agents are preferred as release agents.

As the hindered phenol heat stabilizer, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] and pentaerythrityl-tetrakis [3-] are used.
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionate], N, N′-hexamethylenebis (3,5-di-t-butyl-4-hydroxy-hydrocinnamamide) and the like.

As the phosphorus-based processing stabilizer, tetrakis (2,4-di-t-butylphenyl) -4,4'-biphenylene phosphonite and tris (2,4-di-t-) are used.
Butylphenyl) phosphite and the like.

The blending amount of the hindered phenol heat stabilizer and the phosphorus processing stabilizer is not particularly limited, and it is usually sufficient to blend these blending agents in a blending amount, specifically, a resin. 0 for each total amount of composition.
It is suitable to be about 1 to 5% by weight. The compounding amount is
If it is less than 1% by weight, the retention stability during molding may be poor, and the heat aging resistance of the molded product may be poor. If the blending amount exceeds 5% by weight, the effect of improving the retention stability and heat aging resistance is less than that of the blending amount, and the deposit on the mold at the time of molding and the bleeding on the surface of the molded product are reduced. Such problems may occur.

Examples of the fatty acid ester-based release agent include high molecular weight esters of montanic acid represented by the following formula.

[0030]

[Chemical 1]

(In the formula, Rs are the same or different and each represents an alkyl group having 28 to 32 carbon atoms. N is 1 to 50.
Represents a real number of zero. The amount of the fatty acid ester-based release agent may be usually such an amount that this release agent is added, and specifically about 0.1 to 5% by weight based on the total amount of the resin composition. Appropriate. If it is less than 0.1% by weight, the releasability from the mold at the time of molding may not be sufficient, while if it exceeds 5% by weight, the mechanical strength may decrease.

Further, in the resin composition of the present invention, one or more kinds of various additives such as a flame retardant, a weather resistance agent, an antistatic agent, a colorant, a lubrication agent and the like may be added, if necessary. it can.

[Manufacturing Method] The manufacturing method of the aromatic polyamide resin composition of the present invention is not particularly limited, and for example, a known method can be used. Specifically, MXD-6 nylon (a) and amorphous polyamide (b) are added with a hindered phenol-based heat stabilizer, a phosphorus-based processing stabilizer, a fatty acid ester-based release agent, etc., if necessary. And dry-blending, then the mixture is charged from the main hopper of the twin-screw extruder, the fibrous reinforcing filler (B) is further added midway, and the mixture is melt-kneaded into pellets.

[0034]

The present inventors have found that by blending MXD-6 nylon with a specific amorphous polyamide, excellent characteristics can be exhibited even at a low mold temperature, that is, in an amorphous state. The invention was completed.
That is, MXD-6 nylon exhibits predetermined physical properties, that is, various properties such as excellent strength, rigidity, hardness, creep resistance, and chemical resistance, only by being originally crystallized. It has been found that by blending an amorphous polyamide, predetermined characteristics can be exhibited without crystallization. Therefore, it is not necessary to raise the mold temperature or to carry out an annealing treatment at the time of molding, and it is possible to significantly reduce the occurrence of molding defects due to these processes.

[0035]

EXAMPLES The present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Compounding ingredients MDX-6 nylon (a): Product name MX Nylon 60
00 (manufactured by Mitsubishi Gas Chemical Company, relative viscosity 2.43) -Amorphous polyamide (APA-1): isophthalic acid 4
5 mol%, 5 mol% terephthalic acid, 45 mol% hexamethylenediamine, 5 mol% 4,4'-diamino-3,3'-dimethyldicyclo-hexylenemethane 10 kg of raw materials together with 8 kg of pure water. The reaction vessel was charged and the air in the reaction vessel was purged with nitrogen several times. After raising the temperature to 90 ° C and reacting for about 5 hours, gradually increase the reaction temperature to 1
The temperature was raised to 280 ° C. over a period of 0 hours while stirring the inside of the tank under a pressure of about 18 bar. Then, the pressure was released and the pressure was reduced to atmospheric pressure, and then polymerization was carried out at the same temperature for 6 hours. After the reaction was completed, it was discharged from the reaction tank and cut to obtain pellets. The relative viscosity of the obtained pellet was 1.50.
The glass transition temperature was 150 ° C. This amorphous polyamide is hereinafter referred to as APA-1.

Amorphous polyamide (APA-2): 50 mol% of hexamethylenediamine, 35 mol% of terephthalic acid, and 15 mol% of isophthalic acid are used as raw materials for the above A.
A polycondensate was obtained by reacting in the same manner as PA-1. The obtained polycondensate had a relative viscosity of 2.1 and a glass transition temperature of 125 ° C. This is referred to below as APA-2
Called.

PTW: potassium titanate whiskers,
Product name: Tismo-D102 (Otsuka Chemical Co., Ltd., average fiber diameter 0.3-0.6 μm, average fiber length 10-20 μm, epoxysilane 1% by weight treated product) Aluminum borate whiskers: Arborex G
(Manufactured by Shikoku Kasei Kogyo Co., Ltd., fiber diameter 0.5 to 1.0 μm, fiber length 10 to 30 μm), treated with 1% by weight of epoxysilane-Hindered phenol heat stabilizer: Irganox 1010 (trade name, manufactured by Ciba Geigy) -Phosphorus processing stabilizer: Brand name Irgafos 168 (manufactured by Ciba Geigy) -Fatty acid ester-based release agent: Brand name Hostalbu WE40
(Hoechst) Evaluation method (1) Tensile strength and elongation at break: ASTM D638
It measured using the No. 1 dumbbell according to the above.

(2) Bending strength and elongation at break: ASTM
It was measured according to D790. (3) Izod impact value: measured according to ASTM D256. (4) Heat distortion temperature: Load 1 based on ASTM D648
The measurement was performed under the condition of 8.6 kgf / cm ² .

(5) Residence test: Injection molding was performed after 60 minutes of residence in the cylinder of the injection molding machine (second shot after residence), and its physical properties and appearance were examined. The appearance was evaluated as follows.

∘: No change, ◯: Slightly colored, Δ: Colored and flow mark generated ×: Violently colored and flow mark generated (6) Heat-resistant aging: 5 in air atmosphere at 120 ° C
The treatment was performed for 00 hours and 1000 hours, and the physical properties thereafter were evaluated.

(7) Chemical resistance: ASTM No. 1 dumbbell was immersed in methanol at 23 ° C. for 24 hours, and the physical properties thereafter were evaluated. (8) Gear evaluation: The shape of the spur gear 1 as shown in FIGS. 1 and 2 (2 indicates a gate portion), and the pitch circle diameter is 330 m.
m, the number of teeth is 45, the module is 7.3, and 3000 pieces are continuously molded using a gear mold having a tooth thickness of 0.2 mm. All the gears were inspected and evaluated as follows.

Bubbles, voids: Bubbles even in one place on the gear,
Those in which voids were found were classified as defective and the number was counted. Demolding failure: Similar to the above, those having deformation due to defective demolding were classified and counted.

Gear strength: A spur gear side was engaged with a mating gear (metal), torque was applied to the spur gear side, and the strength at breakage was measured. Examples 1 to 8 and Comparative Examples 1 to 4 MXD-6 nylon (a), amorphous polyamide (b), heat stabilizer, processing stabilizer, and mold release at the compounding ratios shown in Tables 1 to 3. Mixing agents separately, twin screw extruder (PCM
45, manufactured by Ikegai Co., Ltd.) was melt-kneaded at 300 ° C., a fibrous reinforcing filler was added halfway and kneaded, and the obtained strand was cut to obtain pellets of the resin composition. Using the obtained pellets, an injection molding machine (J75SSII-A, manufactured by Japan Steel Works) was used to obtain a resin temperature of 300 ° C. and a mold temperature of 75.
Molding was carried out at 0 ° C. to obtain ASTM No. 1 dumbbell pieces, 3.2 mm thick bending test pieces, and 3.2 mm thick Izod test pieces. In addition, in Comparative Example 2, after molding, 1
Annealing treatment was performed at 30 ° C. for 3 hours.

The obtained test pieces were used to evaluate initial physical properties, retention, heat aging and chemical resistance, and surface appearance. The results are shown together in Tables 1 to 3. Next, a gear for evaluation was formed by using an injection molding machine (J75SSII-A, manufactured by Japan Steel Works) with a gear evaluation mold using a part of the obtained pellets as a raw material. In Examples 1 to 8 and Comparative Examples 1, 3 and 4, molding was performed at a resin temperature of 300 ° C and a mold temperature of 85 ° C. In Comparative Example 2, the resin temperature is 3
After molding at 00 ° C and a mold temperature of 75 ° C, an annealing treatment was performed at 130 ° C for 3 hours. The obtained gear molded product was evaluated as described above, and the results are also shown in Tables 1 to 3.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

[Table 3]

As is clear from Tables 1 to 3, the polyamide resin compositions of Examples 1 to 8 according to the present invention were superior to the polyamide resin compositions of Comparative Example 2 in which the annealing treatment after molding was performed according to the conventional method. It can be seen that mechanical properties, durability, heat aging, and chemical resistance are exhibited, and at the same time, the occurrence of air bubbles, voids and molding defects such as mold release defects in gear molded products is small.

Further, it can be seen that further excellent moldability and durability can be obtained by blending the hindered phenol heat stabilizer, the phosphorus processing stabilizer and the fatty acid ester release agent.

[0051]

As described above, the aromatic polyamide resin composition of the present invention can exhibit the various characteristics of MXD-6 nylon even in the amorphous state, and therefore, need to be crystallized. There is no. Therefore, the steps of increasing the mold temperature or performing the annealing treatment at the time of molding become unnecessary, and the occurrence of molding defects due to these treatments can be significantly reduced.

Therefore, the aromatic polyamide resin composition of the present invention is particularly suitable as a molding material for precision parts used in office automation equipment and watches.

[Brief description of drawings]

FIG. 1 is a plan view showing a gear to be molded in an embodiment of the present invention.

FIG. 2 is a front view showing a gear to be molded in the embodiment of the present invention.

[Explanation of symbols]

 1 ... Gear 2 ... Gate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C08L 77/00

Claims (3)

[Claims] 1. A total of 95 to 20% by weight of MXD-6 nylon (a) and 5 to 80% by weight of an amorphous polyamide (b) having a glass transition temperature of 100 ° C. or higher ((a) and (b)). Is 100% by weight), and the fibrous reinforcing filler (B) is added to the polyamide resin composition (A) in an amount of 5 to 50% by weight of the entire resin composition. Polyamide resin composition. 2. The amorphous polyamide (b) is terephthalic acid, isophthalic acid, hexamethylenediamine,
And 4,4′-diamino-3,3′-dimethyldicyclo-hexylenemethane polycondensation product, or terephthalic acid, isophthalic acid, and hexamethylenediamine polycondensation product. The aromatic polyamide resin composition according to claim 1. 3. The aromatic polyamide resin composition according to claim 1, further comprising a hindered phenol-based heat stabilizer, a phosphorus-based processing stabilizer, and a fatty acid ester-based release agent.