JPH0668073B2 - Polyamide resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyamide resin composition for precision molding, and more specifically, to dimensional stability, high strength, and high rigidity over a wide humidity range. The present invention relates to a polyamide-based resin composition that retains, and is particularly suitable for thin-walled parts and precision molded parts.

[Prior Art] As is well known, nylon 6 and nylon 66 are relatively low-priced as a polyamide-based resin and are widely used as engineering plastics because they have excellent mechanical strength. It has been difficult to apply it as a molding material for precision parts, in which dimensional changes and reduction in strength and rigidity due to the above are serious problems.

That is, a glass fiber compounding composition has been put to practical use in the field of application of mechanical parts that require strength, but one part includes a small part with a weight of 10 g or less and a thin part with a wall thickness of 1 mm or less. Regarding parts and parts such as gears that include an acute angle portion at the tip, the one filled with the glass fiber has insufficient flow of long fibers in the thin portion or the acute angle portion and the content of the fiber is other part. Compared with the above, the strength is insufficient because a sufficient reinforcing effect cannot be obtained. Further, anisotropy and warpage occur due to the orientation of the fibers, which makes precise molding difficult.

In a system filled with a powdered inorganic substance, the difference in the content of the filler and the anisotropy and warpage of the molded product such as glass fiber are slight, but the reinforcing effect is not sufficient and the strength is low. I can only get it.

A potassium titanate fiber-containing composition is disclosed as a resin composition having a slight anisotropy and warpage and having high strength up to the end of a thin portion or an acute angle portion. However,
When Nylon 6 or Nylon 66 is filled with potassium titanate fiber, the strength in the dry state is good, but in the moisture-absorbed state in a high humidity atmosphere, the strength is significantly reduced, and it may be a practical material. There wasn't. This phenomenon was caused by a large amount of potassium that can be liberated from the crystal structure in the conventional potassium titanate fiber, and the free potassium deteriorates the characteristics of the resin composition.

[Problems to be Solved by the Invention] As described above, the conventional potassium titanate fiber is not preferable as a reinforcing material for nylon, which does not like its presence, because of its high free potassium content, and the development of a new reinforcing material. Was desired.

INDUSTRIAL APPLICABILITY The present invention does not have the drawbacks of the conventional ones, has a small anisotropy and warpage, has high strength and high rigidity up to the end of the thin portion or the acute angle portion, and has high strength over a wide humidity range. An object of the present invention is to provide a polyamide resin composition that maintains high rigidity.

[Means for Solving the Problems] As a result of studies conducted by the present inventors to solve the above problems, a tunnel structure potassium hexatitanate fiber having a free potassium amount of 15 ppm or less, preferably 5 ppm or less is added to a polyamide resin. It was found that this is effective, and completed the present invention.

That is, the present invention provides a polyamide resin composition for precision molding containing 95 to 50 parts by weight of a polyamide resin and 5 to 50 parts by weight of a tunnel structure potassium hexatitanate fiber having a free potassium content of 15 ppm or less, preferably 5 ppm or less. To do.

The above-mentioned potassium titanate fiber is a product in which the content of layered structure potassium tetratitanate mixed in the tunnel structure potassium hexatitanate fiber is extremely reduced, and the amount of potassium liberated from the crystal structure is 15 ppm or less, preferably 5 ppm or less. However, by blending the potassium titanate fiber with a polyamide resin, the present inventors can remarkably improve the strength and rigidity when absorbing moisture, as compared with the case where the conventional potassium titanate fiber is blended. Is found.

Since the strength of the conventional resin molded product containing potassium titanate fiber-blended at the time of drying is restored by re-drying after absorbing moisture, the polyamide resin is not hydrolyzed by the presence of free potassium, but potassium titanate fiber. Free potassium has an effect on the interfacial shear strength during moisture absorption between and the polyamide resin, and in the case of the conventional potassium titanate fiber blended composition, free potassium reduces the interfacial shear strength during moisture absorption. It is presumed to be a thing.

Hereinafter, the present invention will be described in detail. The polyamide resin of the present invention is not particularly limited and various resins can be used. That is, by ring-opening polymerization of cycloaliphatic lactams such as nylon 6 and nylon 6 nylon 6
6, by polycondensation reaction of aliphatic diamine such as nylon 610 and nylon MXD6 with aliphatic dicarboxylic acid or aromatic dicarboxylic acid, and by condensation polymerization of amino acid such as nylon 11 and copolymers of various monomers. Among these, it is particularly preferable to use nylon 6 or nylon 66.

The potassium titanate fiber used as a reinforcing material for the polyamide resin composition of the present invention is a tunnel structure potassium hexatitanate fiber having an amount of free potassium of 5 ppm or less.
The tunnel structure potassium hexatitanate fiber that can be used in the present invention is typically manufactured by the following method.

That is, a mixture of a titanium raw material compound and a potassium raw material compound blended in a ratio represented by the general formula K ₂ O · nTiO ₂ (where n = 2 to 4) is baked at 900 to 1200 ° C. to form a block of potassium titanate. By forming fibers, and then immersing the lump product in water or warm water to defibrate the potassium titanate fibers into single fibers, and then adding an acid to the slurry to adjust the pH to 9.3 to 9.7. , The composition of potassium titanate fiber is Ti
O ₂ / K ₂ O (molar ratio) was subjected to composition conversion treatment to give a composition of 5.95 to 6.00, and further heated at 950 to 1150 ° C for 1 hour or more,
It may be acid washed.

In the production of this potassium titanate fiber, examples of the titanium raw material compound include hydrous titanium oxide, titanium dioxide and rutile ore, and the potassium raw material compound produces K ₂ O upon firing, such as K ₂ O, KOH, K ₂ CO ₃
And KNO _{3 and the} like.

The shape of the potassium titanate fiber has an average fiber length of 5
It is preferable that the average aspect ratio (average fiber length / average fiber diameter) is 10 or more.

The amount of free potassium in the obtained potassium titanate fiber may be measured by the following method.

That is, after dispersing a predetermined amount of potassium titanate fiber in water, potassium eluted by boiling can be measured by high-frequency inductively coupled plasma emission spectrometry, flame spectrophotometry, atomic absorption spectrophotometry, etc. . Also, potassium liberated from the crystal structure of potassium titanate exists as potassium hydroxide in the aqueous solution after boiling,
It is also possible to measure and calculate the pH of the solution.

In the present invention, the amount of free potassium means the amount of free potassium with respect to the potassium titanate fiber in the resin composition after being mixed with the polyamide resin. Since the potassium titanate fibers break during mixing, the average fiber length in the composition is shorter than that before mixing. Therefore, when the composition is formed and molded, far better results are obtained as compared with the conventional composition in which the elution of potassium ions is prevented by the surface treatment.

In producing the composition according to the present invention, it is preferable to use potassium titanate fibers treated with a surface treatment agent such as a silane coupling agent from the viewpoint of dispersibility. As a method of using the surface-treated potassium titanate fiber, a method of using a material that has been previously treated with a surface treatment agent and a surface treatment when kneading the potassium titanate fiber and the polyamide resin There is a method of adding the agent, but the effect of the surface treating agent is larger when the potassium titanate fiber which has been previously treated with the surface treating agent is used.

As the surface treatment agent, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane and N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane are particularly effective, It is preferable to add about 0.2 to 2.0% by weight to the potassium titanate fiber.

Regarding the composition of the polyamide-based resin composition of the present invention, the polyamide-based resin is 95 to 50 parts by weight, preferably 90 to 60 parts by weight, the amount of free potassium is 15 ppm or less, preferably 5 ppm.
The tunnel structure potassium hexatitanate fiber which is the following is 5
It is in the range of 50 to 50 parts by weight, preferably 10 to 40 parts by weight. When the amount of the polyamide resin is less than 50 parts by weight, the molding processability is deteriorated, which is not preferable, and when the amount of the potassium titanate fiber is less than 5 parts by weight, the effect of improving the strength is insufficient.

Considering the balance between cost and workability, the range of 10 to 40 parts by weight of potassium titanate fiber is preferable.

The resin composition of the present invention contains one or more kinds of various additives such as a flame retardant, a heat stabilizer, and a lubricant depending on the use and purpose of the composition as long as the physical properties of the composition are not adversely affected. It can be added.

The polyamide resin composition according to the present invention obtained as described above is a precision molded part, that is, a part including a thin part having a wall thickness of 1 mm or less, and a small part having a molding weight of about 10 g or less or a tip. It is suitable for manufacturing parts having sharp corners, such as various gears, cams, pulleys, and shafts, which require mechanical strength.

EXAMPLES The present invention will be described in more detail with reference to the following examples.
The following examples are provided for illustration only and the scope of the invention is not limited thereby. In the following, all parts are by weight unless otherwise specified.

Example 1 1400 g of anatase-type titanium oxide and 800 g of potassium carbonate were dry-mixed, put in an alumina crucible, and fired in an electric furnace at a heating rate of 250 ° C./hour, a holding temperature of 1050 ° C., and a holding time of 3 hours. After that, the temperature was lowered at a rate of 200 ° C./hour.

The fired product is placed in 10 L of hot water in a stainless steel container and immersed for 5 hours, and then stirring is started at 600 rpm to adjust the bath temperature to 60 ° C. The pH is adjusted to 9.5 by adding 5N hydrochloric acid dropwise. After this, if the stirring is further continued, potassium ions will be eluted from the layer of potassium tetratitanate, so the pH will increase, but after dropping hydrochloric acid, the pH will rise to 0.1 or less when the stirring is continued for 30 minutes, Hydrochloric acid was added dropwise at minute intervals to adjust the pH to 9.5.

After filtration, it was baked at 1000 ° C. for 3 hours. The calcined product was dispersed in 10 L of warm water, and 1N-hydrochloric acid was added dropwise to adjust the pH to 4. It was filtered and dried to obtain potassium titanate fiber.

When this fiber was identified by X-ray diffraction, it was a single phase of tunnel structure / potassium hexatitanate. When the fibers were observed with a scanning electron microscope, the average fiber length was
The average fiber diameter was 80 μm and 1.2 μm.

20 parts of the obtained potassium titanate fiber and 80 parts of nylon 66 resin (manufactured by Ube Industries, trade name: UBE nylon 2020B),
A twin-screw extruder AS-30 manufactured by Nakatani Machine Co., Ltd. melted and kneaded at a temperature of 280 ° C. to obtain pellets.

Example 2 70 parts of the same nylon 66 resin as in Example 1 and 30 parts of a sample prepared by treating the surface of the potassium titanate fiber used in Example 1 with 0.8% by weight of γ-aminopropyltriethoxysilane were used. Melting, kneading and pelletizing were performed under the same conditions as in 1.

Comparative Example 1 The firing temperature after the composition conversion treatment was from 1000 ° C. of Example 1 to 850.
The same operation as in Example 1 was carried out except that the temperature was lowered to 0 ° C. to obtain a single phase of tunnel structure / potassium hexatitanate. When the fibers were observed with a scanning electron microscope, the average fiber length was
The average fiber diameter was 80 μm and 1.2 μm.

20 parts of the obtained potassium titanate fiber and 80 parts of the same nylon 66 resin as in Example 1 were pelletized under the same conditions as in Example 1.

The amount of free potassium in each of the potassium titanate fiber obtained in Example 1 and the potassium titanate fiber obtained in Comparative Example 1 was measured by the following method.

A predetermined amount of the pellets of Example 1 and Comparative Example 1 were collected, dispersed in water, boiled for 10 minutes, eluted in water, and the amount of potassium was analyzed by Japan Jarrell Ash model ICAP-505 high-frequency inductively coupled plasma emission spectrometry. The amount of chlorine ions in the aqueous solution was analyzed by a device and a spectrophotometer 100-0101 manufactured by Hitachi, Ltd.

Thus, the potassium contained as potassium chloride was removed, and the amount of free potassium eluted from the crystal structure of potassium titanate was calculated.

In the case of Example 1, 1.5 ppm with respect to potassium titanate fiber,
In the case of Comparative Example 1, it was 23 ppm. The average fiber length of the potassium titanate fibers in the test pieces of Examples and Comparative Examples are both 25
Since it was about μm, it is considered that the amount of free potassium is related to the decrease in strength and rigidity when absorbing moisture.

Comparative Example 2 70 parts of the same nylon 66 resin as in Example 1 and 30 parts of a sample obtained by treating the surface of the potassium titanate fiber used in Comparative Example 1 with 0.8% by weight of γ-aminopropyltriethoxysilane were used. Pelletization was performed under the same conditions as in 1.

Comparative Example 3 80 parts of the same nylon 66 resin as in Example and 20 parts of potassium titanate fiber (Otsuka Chemical, trade name: Tismo D) were pelletized under the same conditions as in Example 1.

The pellets obtained in Examples 1 and 2 and Comparative Examples 1 to 3 were dried at 120 ° C. for 12 hours using a vacuum dryer, and then injected by Yamashiro Seiki Seisakusho SAV-30-30 type injection molding machine. Molding (cylinder temperature 260 to 280 ° C, mold temperature 80 ° C) was performed to obtain a test piece for measuring tensile strength and bending strength. Table 1 shows the results of the strength measurement when absolutely dried and when the resin absorbs 2.5% of moisture. For comparison, this table also shows the physical properties of nylon 66 resin alone. (Comparative example 4) As is clear from Table 1, the nylon 66 resin composition containing tunnel structure potassium hexatitanate fiber having a free potassium content of 15 ppm or less has high strength and high rigidity even when absorbing moisture.

Example 3 Nylon 6 resin (manufactured by Ube Industries, trade name: UBE nylon 1013)
B) 70 parts and 30 parts of the same potassium titanate fiber as in Example 2 were melted and kneaded at a temperature of 260 ° C. by a twin-screw extruder AS-30 manufactured by Nakatani Machine Co., Ltd. to be pelletized.

Comparative Example 5 70 parts of the same nylon 6 resin as in Example 3 and 30 parts of the same potassium titanate fiber as in Comparative Example 2 were pelletized under the same conditions as in Example 3.

The pellets obtained in Example 3 and Comparative Example 5 were dried at 110 ° C. for 15 hours using a vacuum dryer, and then SAV-made by Yamashiro Seiki Seisakusho Ltd.
Injection molding with a 30-30 type injection molding machine (cylinder temperature 22
(0 to 240 ° C., mold temperature 80 ° C.) to obtain a strength measuring test piece.

Table 2 shows the results of measuring the physical properties when absolutely dry and when the resin absorbs 3.5% moisture. For comparison, this table shows the physical properties of nylon 6 resin alone. (Comparative example 6) As is clear from Table 2, the nylon 6 resin composition containing the tunnel structure potassium hexatitanate fiber having a free potassium content of 5 ppm or less has high strength and high rigidity even when absorbing moisture.

[Structure of the Invention] A molded product obtained by molding the composition of the present invention has high strength and high rigidity when absorbing moisture, and is required to have high mechanical strength such as gears, cams, pulleys and shafts. Effective in precision machine parts applications.

Claims (2)

[Claims] 1. A polyamide resin composition for precision molding containing 95 to 50 parts by weight of polyamide resin and 5 to 50 parts by weight of tunnel structure potassium hexatitanate fiber having a free potassium content of 15 ppm or less. 2. A precision machine part made from the composition of claim 1.