JP4875793B2 - Plastic magnet composition - Google Patents

Description

【００４５】
【発明の効果】
本発明によれば、優れた流動性とともに、結晶化速度が大きくそのために操業性が改良されると同時に，従来品より優れた磁気特性と機械的強度を有するプラスチックマグネットを得ることのできる組成物が得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyamide resin composition that can be suitably used for a plastic magnet. More specifically, the present invention is based on a polyamide resin, has good flowability and crystallinity during molding, and has magnetic characteristics and mechanical strength. The present invention relates to a composition capable of obtaining an excellent plastic magnet.
[0002]
[Prior art]
Plastic magnets have higher mechanical strength than conventional sintered magnets, can be molded into various free shapes, and have a wider range of applications due to high productivity. Yes.
[0003]
As the binder resin for plastic magnets, polyolefin resins such as polyethylene and polypropylene, and polyamide resins such as nylon 6, nylon 66, and nylon 12 are mainly used. The one using resin is increasing.
[0004]
Plastic magnets are usually magnetized in the mold during injection molding, but in order to obtain plastic magnets with excellent magnetic properties, the binder resin must have high fluidity, and the binder resin has a low melt viscosity. Is required.
[0005]
As a method for improving fluidity, for example, Japanese Patent Application Laid-Open No. 59-176346 proposes a method of adding a polyamide oligomer to a polyamide resin. However, this method has a problem that the oligomer is eluted during molding to cause a defective release from the mold of the molded product, or the oligomer is deposited on the surface of the molded product to impair the surface appearance.
[0006]
On the other hand, as a polyamide resin composition having improved fluidity, a composition using a polyamide resin having a terminal carboxyl group concentration of 5 to 70 meq / kg (JP-A-2-13061), a terminal carboxyl group concentration of 90 meq / kg is used. Compositions using the following polyamide resins (JP-A-5-51528), compositions using polyamide resins end-capped with monocarboxylic acid (JP-A-9-71721), and the like have been proposed.
[0007]
However, none of the above-mentioned compositions are satisfactory in terms of mechanical strength when used as a plastic magnet.
[0008]
[Problems to be solved by the invention]
The present invention solves the above problems, and can provide a plastic magnet based on a polyamide resin, excellent in fluidity and crystallinity during molding, and having improved magnetic properties and mechanical strength. An object is to provide a composition.
[0009]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have found that a plastic magnet composition comprising a polyamide resin having a specific terminal carboxyl group concentration and a relative viscosity, a layered silicate and a magnetic powder has excellent workability. And the present invention has been achieved.
[0010]
That is, the gist of the present invention is as follows.
(1) (A) Polyamide resin having a terminal carboxyl group concentration of 40 to 150 meq / kg and a relative viscosity of 1.98 to 2.3 (value at 1 g / dl in 25% 96% concentrated sulfuric acid), (B) layered A plastic magnet composition comprising a silicate and (C) magnetic powder, wherein the amount of the layered silicate (B) is 0.2 to 15 parts by weight with respect to 100 parts by weight of the polyamide resin (A). A plastic magnet composition having excellent magnetic properties, wherein the silicate (B) is dispersed in the polyamide resin (A) at a molecular level.
(2) a layered silicate (B) is a plastic magnet composition having excellent magnetic properties of (1) Symbol mounting, characterized in that a swellable fluorine mica-based mineral.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
[0012]
Examples of the polyamide resin in the present invention include aliphatic nylon such as nylon 6, nylon 66, nylon 46, nylon 12, nylon 11, and nylon 610, semi-aromatic nylon such as nylon 6T, nylon 9T, and MXD6 nylon, and a combination thereof. A polymer or a mixture thereof can be mentioned, but nylon 6 or a copolymer thereof (a nylon 6 component is 80% or more) is preferable, and nylon 6 is particularly preferable in terms of a balance between cost and performance. preferable.
[0013]
The polyamide resin needs to have a terminal carboxyl group concentration of 40 to 150 meq / kg. When the terminal carboxyl group concentration is less than 40 meq / kg, the affinity with the magnetic powder is deteriorated, the fluidity of the composition is lowered, and excellent magnetic properties cannot be obtained. On the other hand, when the terminal carboxyl concentration exceeds 150 meq / kg, the affinity with the magnetic powder becomes too good, or the fluidity of the composition decreases, which is not preferable.
[0014]
Further, polyamide resin, using 96 wt% concentrated sulfuric acid as solvent, temperature 25 ° C., the value obtained under conditions of a concentration 1 g / dl, it is need the 1.98 to 2.3. When the relative viscosity is less than 1.5, the mechanical strength of the composition is lowered, which is not preferable. On the other hand, when the relative viscosity exceeds 2.3, the fluidity of the composition is lowered, and it is difficult to obtain a high-performance plastic magnet.
[0015]
In the present invention, in order to control the terminal carboxyl group concentration and the relative viscosity within the scope of the present invention, for example, the end capping can be performed with a monocarboxylic acid. Specific examples of monocarboxylic acids include benzoic acid, acetic acid, formic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, palmitic acid , Stearic acid, acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid, phenylacetic acid, hydrocinnamic acid, cinnamic acid, toluic acid, chlorobenzoic acid, nitrobenzoic acid, dinitrobenzoic acid, trinitrobenzoic acid, anthranilic acid, hydroxy Benzoic acid, methoxybenzoic acid and the like can be mentioned, and among these, the case where benzoic acid is used is particularly suitable.
[0016]
As the layered silicate in the present invention, smectite-based minerals such as montmorillonite, beidellite, saponite, hectorite, and saconite, vermiculite-based minerals such as vermiculite, muscovite, biotite, paragonite, levitrite, mica-based materials such as swellable fluorinated mica Minerals, brittle mica minerals such as margarite, clintnite, and anandite, chlorite minerals such as donbasite, sudite, kukeite, clinochlore, chamosite, and nimite, hydrous inosilicate minerals such as sepiolite, etc. Of these, swellable fluorine mica-based minerals (in which the hydroxyl group of mica is substituted with fluorine) and montmorillonite are particularly preferable in terms of dispersibility in the polyamide resin.
[0017]
As a compounding quantity of layered silicate, it is necessary to set it as the range of 0.2-15 weight part with respect to 100 weight part of polyamide resins. If the blending amount is less than 0.2 parts by weight, it becomes difficult to obtain a plastic magnet having good mechanical strength, while if it exceeds 15 parts by weight, the fluidity tends to decrease.
[0018]
The aforementioned swellable fluoromica mineral is represented by the following formula and can be easily synthesized.
α (MF) · β (aMgF ₂ · bMgO) · γSiO ₂
(In the formula, M represents sodium or lithium, α, β, γ, a and b each represents a count, 0.1 ≦ a ≦ 2, 2 ≦ β ≦ 3.5, 3 ≦ γ ≦ 4, 0 ≦ a ≦ 1. , 0 ≦ b ≦ 1, a + b = 1).
[0019]
As a method for producing such a fluorine mica, for example, silicon oxide, magnesium oxide and various fluorides are mixed, and the mixture is completely melted in an electric furnace or a gas furnace in a temperature range of 1400 to 1500 ° C. There is a so-called melting method in which fluorine mica is crystal-grown in the reaction vessel during the cooling process.
[0020]
Further, there is a method in which talc is used as a starting material, and alkali metal ions are intercalated therein to obtain fluorine mica (Japanese Patent Laid-Open No. 2-149415). In this method, fluorinated mica can be obtained by mixing talc with silicic acid alkali or alkali fluoride and heating in a magnetic crucible at 700 to 1200 ° C. for a short time.
[0021]
Moreover, although the above-mentioned montmorillonite may be a natural product or a synthetic product, sodium montmorillonite is particularly preferable. These may be subjected to water treatment or ion exchange treatment (treatment for converting interlayer ions into sodium) to increase the purity.
[0022]
In the present invention, the layered silicate (B) needs to be dispersed at the molecular level in the polyamide resin (A) and gives particularly preferable fluidity and crystallization behavior. Specifically, the molecular level dispersion state can be confirmed by performing wide-angle X-ray measurement. That is, in the raw material state, diffraction derived from the interlayer distance in the c-axis direction of the layered silicate (usually 8 to 20 mm under wet heat) is observed, but the layered silicate is dispersed at a molecular level in the polyamide resin. Then, each silicate layer of the layered silicate is peeled off and takes a random direction. As a result, it can be confirmed that a peak derived from the crystal structure of the layered silicate is not observed.
[0023]
Moreover, in order to improve the dispersibility of the layered silicate in the polyamide resin, a so-called swelling treatment may be performed in which the layers of the raw layered silicate are expanded in advance. Examples of electropositive swelling agents include cations obtained by protonating aminocarboxylic acids such as 12-aminododecanoic acid, 11-aminoundecanoic acid and 6-aminocaproic acid, quaternary ammonium cations such as dimethyl distearyl ammonium, Examples include cations obtained by protonating lactams such as ε-caprolactam and ω-laurolactam. Examples of the electrically neutral swelling agent include ε-caprolactam, ω-laurolactam, ethylene glycol, polyethylene glycol, polyvinyl pyridine, dodecyl pyrrolidone, polyvinyl pyrrolidone, and the like.
[0024]
The means for dispersing the layered silicate in the polyamide resin is not particularly limited, and a method of melt-kneading the polyamide resin and the layered silicate that has been swollen in advance with an ordinary extruder, or the polyamide in the presence of the layered silicate. Although it can be obtained by polymerizing the monomer to be formed, the latter method is particularly preferred.
[0025]
Examples of the magnetic powder in the present invention include ferrite-based barium ferrite and strontium ferrite, samarium-cobalt 1/5 and 2/17, and neodymium iron boron MQ powder (manufactured by GM). The particle diameter is preferably 0.5 to 10 μm, particularly preferably 1.0 to 5.0 μm.
[0026]
Moreover, as a compounding quantity of magnetic powder, it is used in 60 to 95 weight% normally with respect to the whole composition. If the blending amount is less than 60% by weight, the magnetic properties are deteriorated, while if it exceeds 95% by weight, molding becomes difficult.
[0027]
The composition of the present invention includes other thermoplastic resins other than polyamide resin, such as polystyrene, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, ABS, PPO (polyphenylene oxide), within a range not impairing the effects of the present invention. ) Etc. may be blended.
[0028]
In addition, plasticizers such as diethyl phthalate, dibutyl phthalate, dioctyl phthalate, and fatty acid esters that are commonly used as plastic magnet compositions, and lubricants such as zinc stearate, aluminum stearate, magnesium stearate, and mineral oil are added. May be.
[0029]
Furthermore, for the purpose of increasing the affinity between the polyamide resin and the magnetic powder, an aminosilane, epoxysilane, vinylsilane, titanium-based coupling agent or the like can be used.
[0030]
In addition, an antioxidant, a crystal nucleating agent, a flame retardant, and the like can be appropriately blended in the composition of the present invention as long as the effects of the present invention are not impaired.
[0031]
【Example】
Next, the present invention will be described more specifically with reference to examples and comparative examples.
[0032]
〔Measuring method〕
(1) The relative viscosity polyamide resin was dissolved in 96% concentrated sulfuric acid so as to have a concentration of 1 g / dl, and the flow time was measured at 25 ° C. using an Ubbelohde viscometer. The value obtained by dividing the sample solution flow time by the solvent flow time was taken as the relative viscosity of the sample.
When adjusting the sample solution concentration of the polyamide resin to 1 g / dl, the concentration of the polyamide resin excluding the layered silicate is set to 1 g / dl in consideration of the concentration of the layered silicate contained in advance. did.
(2) A polyamide resin (or polyamide resin) containing a terminal carboxyl group concentration layered silicate was dissolved in benzyl alcohol and quantified by neutralization titration using a 0.01 N KOH benzyl alcohol solution.
(3) Polyamide resin (or polyamide resin) containing terminal amino group concentration layered silicate is dissolved in a mixed solvent of phenol / methanol (volume ratio 10/1) and determined by neutralization titration with 0.01N hydrochloric acid. did.
(4) Interlayer distance of layered silicate (dispersibility in polyamide resin)
Using a wide-angle X-ray diffractometer (manufactured by Rigaku Corporation, RAD-rB type), the corresponding interlayer distance was calculated from the 2θ value of the diffraction peak derived from the thickness in the c-axis direction of the layered silicate.
When no peak derived from the c-axis direction was confirmed, it was considered that each silicate sheet of the layered silicate was randomly dispersed at the molecular level.
(5) Melt flow rate (MFR)
A polyamide resin (or polyamide resin) containing a layered silicate was measured using a melt indexer (manufactured by Toyo Seiki Co., Ltd.) under the conditions of 270 ° C. and 10 kgf.
(6) Crystallization temperature and crystallization speed Polyamide resin (or polyamide resin) containing layered silicate was measured using a DSC measuring apparatus (DSC-7, manufactured by Perkin Elmer).
The temperature was raised from room temperature to 280 ° C. at 20 ° C./min, and the maximum value of the crystallization peak when the temperature was lowered at 20 ° C./min was taken as the crystallization temperature.
Further, the difference ΔT between the crystallization start temperature and the crystallization end temperature at this time was used as an index of the crystallization rate. A smaller value of ΔT indicates a higher crystallization rate.
(7) Bending strength
Based on ASTM D790, the bending strength of the plastic magnet molded piece was measured.
[0033]
Example 1
ε-caprolactam 10 kg, swellable synthetic fluorinated mica (“Co-100 Chemical Co., Ltd.“ ME-100 ”, composition formula: Na _0.6 Mg _2.7 Si ₄ O ₁₀ F ₂ , the interlayer distance of the silicate layer measured by wide-angle X-ray is 9.6 mm and 12.5%) To 400 g of pure water and 500 g of pure water, 82 g of benzoic acid was added as an end-capping agent and polymerized at 260 ° C. for 6 hours in a 30 liter autoclave.
Then, it was discharged into a water bath in a strand form from a nozzle having a diameter of 3 mm, and pelletized while taking out the cooled resin strand with a cutter.
Next, the pellets were scoured with hot water at 95 ° C. and then dried.
The obtained polyamide resin had a relative viscosity of 1.98, a terminal carboxyl group concentration of 126 meq / kg, and a terminal amino group concentration of 25 meq / kg.
Moreover, when the wide angle X-ray measurement of this resin pellet was performed, the diffraction peak of the c-axis direction of the layered structure of the swellable synthetic fluorine mica present in the resin was not observed, and the layer structure was completely lost. Was confirmed.
Further, Table 1 shows the MFR, crystallization temperature, and crystallization speed of the pellet.
Next, the pellets were pulverized and passed through a 150 mesh sieve, and then 12 parts by weight of the pulverized product, 88 parts by weight of strontium ferrite having an average particle size of 1.2 μm, 0.5 part by weight of γ-aminopropyl triethoxysilane, and stearin. 0.1 parts by weight of zinc oxide was mixed with a Henschel mixer and extruded at 250 ° C. using a twin screw extruder (Ikegai Iron Works, PCM-30) to produce pellets.
The pellets were injected in a 10,000 Oe (Oersted) magnetic field using an injection molding machine (Toshiba Machine, IS80G-3A) under conditions of a cylinder temperature of 300 ° C, a mold temperature of 120 ° C, and an injection pressure of 80 MPa. A rectangular plastic magnet molded piece having a thickness of 3 mm, a width of 12 mm, and a length of 127 mm was obtained.
Table 1 shows the measurement results of the maximum magnetic energy product (BHmax) as the bending strength and magnetic properties of the molded piece.
[0034]
Example 2
9 kg of ε-caprolactam, 1 kg of 12-aminododecanoic acid, 300 g of swellable synthetic fluorine mica (“ME-100” manufactured by Corp Chemical Co.), 500 g of pure water and 70 g of benzoic acid were polymerized under the same conditions as in Example 1.
The obtained polyamide resin had a relative viscosity of 2.04, a terminal carboxyl group concentration of 100 meq / kg, and a terminal amino group concentration of 30 meq / kg.
Next, magnetic powder was blended in the same manner as in Example 1, and molded by the same method as in Example 1 to obtain a plastic magnet molded piece.
Table 1 shows the measurement results of the interlayer distance, MFR, crystallization temperature and crystallization speed of the resin pellets and the bending strength and BHmax of the plastic magnet molded piece.
[0035]
Example 3
10 kg of ε-caprolactam, 300 g of swellable synthetic fluorine mica (“ME-100” manufactured by Corp Chemical Co.), 500 g of pure water and 52 g of benzoic acid were polymerized under the same conditions as in Example 1.
The resulting polyamide resin had a relative viscosity of 2.10, a terminal carboxyl group concentration of 70 meq / kg, and a terminal amino group concentration of 32 meq / kg.
Next, magnetic powder was blended in the same manner as in Example 1, and molded by the same method as in Example 1 to obtain a plastic magnet molded piece.
Table 1 shows the measurement results of the interlayer distance, MFR, crystallization temperature and crystallization speed of the resin pellets and the bending strength and BHmax of the plastic magnet molded piece.
[0036]
Example 4
Except for the use of natural montmorillonite treated with water (“kunipia F” manufactured by Kunimine Kogyo Co., Ltd., Yamagata, with a silicate layer distance measured by wide-angle X-ray of 12.5 mm) instead of the swellable synthetic fluoromica. Polymerization was carried out under the same conditions as in Example 1.
The obtained polyamide resin had a relative viscosity of 2.10, a terminal carboxyl group concentration of 93 meq / kg, and a terminal amino group concentration of 27 meq / kg.
Next, magnetic powder was blended in the same manner as in Example 1, and molded by the same method as in Example 1 to obtain a plastic magnet molded piece.
Table 1 shows the measurement results of the interlayer distance, MFR, crystallization temperature and crystallization speed of the resin pellets and the bending strength and BHmax of the plastic magnet molded piece.
[0037]
Example 5
Polymerization was carried out under the same conditions as in Example 1 except that natural montmorillonite (“kunipia F” manufactured by Kunimine Kogyo Co., Ltd., Yamagata) was used instead of the swellable synthetic fluorine mica.
The resulting polyamide resin had a relative viscosity of 1.99, a terminal carboxyl group concentration of 91 meq / kg, and a terminal amino group concentration of 32 meq / kg.
Next, magnetic powder was blended in the same manner as in Example 1, and molded by the same method as in Example 1 to obtain a plastic magnet molded piece.
Table 1 shows the measurement results of the interlayer distance, MFR, crystallization temperature and crystallization speed of the resin pellets and the bending strength and BHmax of the plastic magnet molded piece.
[0038]
Comparative Example 1
Polymerization was carried out under the same conditions as in Example 1 except that no swellable synthetic fluorine mica was added.
The obtained polyamide resin had a relative viscosity of 2.02, a terminal carboxyl group concentration of 99 meq / kg, and a terminal amino group concentration of 28 meq / kg.
Next, magnetic powder was blended in the same manner as in Example 1, and molded by the same method as in Example 1 to obtain a plastic magnet molded piece.
Table 1 shows the measurement results of the interlayer distance, MFR, crystallization temperature and crystallization speed of the resin pellets and the bending strength and BHmax of the plastic magnet molded piece.
[0039]
Comparative Example 2
Polymerization was carried out under the same conditions as in Example 1 except that 10 g of benzoic acid was used.
The resulting polyamide resin had a relative viscosity of 2.50, a terminal carboxyl group concentration of 55 meq / kg, and a terminal amino group concentration of 28 meq / kg.
Next, magnetic powder was blended in the same manner as in Example 1, and molded by the same method as in Example 1 to obtain a plastic magnet molded piece.
Table 1 shows the measurement results of the interlayer distance, MFR, crystallization temperature and crystallization speed of the resin pellets and the bending strength and BHmax of the plastic magnet molded piece.
[0040]
Comparative Example 3
Polymerization was carried out under the same conditions as in Example 1 except that the amount of benzoic acid was changed to 110 g.
The resulting polyamide resin had a relative viscosity of 1.50, a terminal carboxyl group concentration of 55 meq / kg, and a terminal amino group concentration of 28 meq / kg.
Next, magnetic powder was blended in the same manner as in Example 1, and molded by the same method as in Example 1 to obtain a plastic magnet molded piece.
Table 1 shows the measurement results of the interlayer distance, MFR, crystallization temperature and crystallization speed of the resin pellets and the bending strength and BHmax of the plastic magnet molded piece.
[0041]
Comparative Example 4
Polymerization was carried out under the same conditions as in Example 1 except that no swellable synthetic fluorine mica was added and the amount of benzoic acid was changed to 110 g.
The resulting polyamide resin had a relative viscosity of 1.50, a terminal carboxyl group concentration of 180 meq / kg, and a terminal amino group concentration of 29 meq / kg.
Next, magnetic powder was blended in the same manner as in Example 1, and molded by the same method as in Example 1 to obtain a plastic magnet molded piece.
Table 1 shows the measurement results of the interlayer distance, MFR, crystallization temperature and crystallization speed of the resin pellets and the bending strength and BHmax of the plastic magnet molded piece.
[0042]
Comparative Example 5
Polymerization was carried out under the same conditions as in Example 1 except that the swellable synthetic fluorine mica and benzoic acid were not added.
The obtained polyamide resin had a relative viscosity of 2.60, a terminal carboxyl group concentration of 30 meq / kg, and a terminal amino group concentration of 35 meq / kg.
Next, magnetic powder was blended in the same manner as in Example 1, and molded by the same method as in Example 1 to obtain a plastic magnet molded piece.
Table 1 shows the measurement results of the interlayer distance, MFR, crystallization temperature and crystallization speed of the resin pellets and the bending strength and BHmax of the plastic magnet molded piece.
[0043]
In Comparative Example 1 and Comparative Example 4, since the layered silicate was not added, the resin was slowly solidified when being discharged from the autoclave, and a resin fusion phenomenon occurred when pelletizing with a strand cutter, Operational conditions were extremely poor.
[0044]
[Table 1]

[0045]
【Effect of the invention】
According to the present invention, a composition capable of obtaining a plastic magnet having excellent fluidity, high crystallization speed, and hence improved operability, and at the same time superior magnetic properties and mechanical strength than conventional products. Is obtained.

Claims (2)

(A) a terminal carboxyl group concentration of 40 to 150 meq / kg, a relative viscosity of 1.98 to 2.3 (value at 1 g / dl in 25 ° C., 96% concentrated sulfuric acid), (B) a layered silicate, and (C) A plastic magnet composition made of magnetic powder, wherein the amount of layered silicate (B) is 0.2 to 15 parts by weight relative to 100 parts by weight of polyamide resin (A), and layered silicate ( A plastic magnet composition having excellent magnetic properties, wherein B) is dispersed in the polyamide resin (A) at a molecular level.   The plastic magnet composition having excellent magnetic properties according to claim 1, wherein the layered silicate (B) is a swellable fluoromica-based mineral.