JP4412988B2 - Resin pellets with improved color tone containing silica particles - Google Patents

Description

  The present invention relates to a resin pellet containing silica particles having an excellent color tone. More specifically, the present invention relates to a silica particle-containing resin pellet that can be suitably used in sliding applications or film applications and has excellent color tone and thermal stability.

Conventionally, polyamide resins have been used in the fields of electric and electronic parts, automobile parts, industrial equipment, films and the like. A composition in which silica particles are blended with a polyamide resin is often used, and it is a well-known fact in the art that it is used in sliding applications and film applications. More specifically, for example, a polyamide resin composition having excellent slidability by adding 1 to 30% by weight of high-purity spherical silica having an average particle diameter of 0.1 to 100 μm in the polyamide resin is proposed. (For example, refer to Patent Document 1). In addition, a biaxially oriented film having excellent antiblocking properties has been proposed by containing 0.005 to 1.0% by weight of inorganic fine particles having an average particle size of 0.1 to 10 μm and a specific surface area of 100 m ² / g or more. (For example, refer to Patent Document 2).

It is well known in the art that melt kneading is carried out as a production method containing these inorganic particles such as silica.
However, the color tone and thermal stability of silica-containing pellets and resin molded products obtained by blending silica particles with polyamide resin and melt-kneading deteriorate the commercial value. For this reason, when blending silica particles in a polyamide resin and using it for sliding applications or film applications, it is strongly desired to improve the color tone and thermal stability.
JP-A-5-186684 Japanese Patent Publication No.58-52820

  An object of this invention is to provide the silica particle containing resin pellet excellent in the color tone which consists of a polyamide resin and a silica particle by a melt-kneading method.

As a result of intensive studies, the present inventors have found that the above-mentioned object can be effectively achieved by melt-kneading using a polyamide resin containing a specific phosphorus compound and a soluble metal aluminate salt. Arrived.
That is, the present invention is as follows.
(1) At least one phosphorus compound (a) selected from the group consisting of phosphoric acids, phosphorous acids and hypophosphorous acids and / or metal salts thereof, general formula (M ₂ O) X (Al ₂ O ₃ ) Y (where X + Y = 1 and M is a metal element of Group 1 of the Periodic Table), the soluble aluminate metal salt (b) and the water content are 0.1 wt% or more and 0.5 wt% or less Ri is a polyamide resin (c) Tona, the molar ratio of the polyvalent metal and the monovalent metal (polyvalent metal / monovalent metal), the polyamide resin composition is 0.30 to 1.0 (a) 98 to A silica particle-containing resin pellet obtained by melt-kneading 50 parts by weight and 2 to 50 parts by weight of silica particles (B).

(2) The component (a) is at least one compound selected from phosphoric acid, phosphorous acid and hypophosphorous acid and / or salts thereof with Group 1 metals of the periodic table The silica particle containing resin pellet as described in (1).
(3) The silica particle-containing resin pellet according to (1) or (2), wherein the component (a) is sodium hypophosphite.
(4) The silica particle-containing resin pellet according to any one of (1) to (3), wherein the component (c) contains a polyamide resin having an average particle size of 1 mm or less in an amount of 30% by weight or more .

(5) The silica particle-containing resin pellet according to any one of (1) to (4) above, wherein the component (c) is nylon 66 and / or nylon 66 / 6I .
(6) B value is 15 or less , The silica particle containing resin pellet in any one of (1)-(5) characterized by the above-mentioned.

  The silica-containing resin pellet of the present invention is suppressed from being colored yellow at the time of compounding, thereby providing a sliding member having excellent slidability and a film imparted with antiblocking properties without impairing the color tone. be able to.

The present invention is described in detail below.
Polyamide resins used for the silica-containing resin pellets of the present invention are nylon 6, nylon 10, nylon 12, nylon 66, nylon 610, nylon 612, nylon 46, nylon 6T (T is a terephthalic acid component), nylon 6I (I is isophthalate). And all polyamides such as at least two kinds of copolymers selected from them and a mixture of at least two kinds selected from them. Nylon 66 and / or nylon 66 / 6I are particularly preferable.
The molecular weight of the polyamide resin used in the present invention is not particularly limited, but preferably the effect of the present invention tends to be achieved more significantly by using a polyamide having a VR (formic acid relative viscosity) in the range of 30 to 80. VR35-70 are more preferable, and VR40-60 are still more preferable.

These polyamide resins can be polymerized by known methods such as melt polymerization, ring-opening polymerization, solid phase polymerization, and solution polymerization, and the resin after polymerization is cooled and solidified to obtain a polyamide resin. Generally, melt polymerization is performed to form a polyamide resin in the form of pellets.
The phosphorus compound as component (a) of the present invention is at least one selected from the group consisting of phosphoric acids, phosphorous acids, hypophosphorous acids and / or metal salts thereof.
Examples of the phosphoric acids, phosphorous acids, and hypophosphorous acids include phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphorous acid, and diphosphorous acid.
In addition, examples of the metal phosphates, metal phosphites, and metal hypophosphites include phosphoric acids and manganese, zinc, and aluminum of Groups 1 and 2 of the periodic table. Moreover, the salt with ammonia, an alkylamine, a cycloalkylamine, and diamine can be mentioned.

Preferred component (a) is a metal salt composed of phosphoric acid, phosphorous acid and hypophosphorous acid and / or a metal of group 1 of the periodic table, more preferably phosphorous acid or hypophosphorous acid and / Or a metal salt composed of a Group 1 metal of the periodic table.
The component (a) is used alone, and in this case, the most preferred metal salt is sodium hypophosphite (NaH ₂ PO ₂ ) or a hydrate thereof (NaH ₂ PO ₂ .nH ₂ O).
The soluble aluminates which are the component (b) of the present invention are represented by the following general formula.
(M ₂ O) _X (Al ₂ O ₃ ) _Y
However, X + Y = 1 and M is a periodic table group 1 metal.

A preferred component (b) of the present invention is sodium aluminate in which the main component of M in the above general formula is sodium.
When a metal salt of phosphoric acid is used as the component (a), the molar ratio Y / X between the aluminum (Al) and the group 1 metal M in the general formula is preferably 0.35 ≦ Y. /X≦1.25, more preferably 0.35 ≦ Y / X <1.00, and even more preferably 0.5 ≦ Y / X ≦ 0.87. The range of the content (Z) of the component (c) per 1,000,000 g of polyamide is preferably Z <1.785 / (XY), more preferably Z <1 in relation to Y / X. .785 / X. When X, Y, and Y / X are in the above ranges, there is a tendency that an increase in yellowness due to thermal history, a molecular weight change suppressing effect, toughness, and the like can be achieved higher.

  In the present invention, the molar ratio of polyvalent metal to monovalent metal (polyvalent metal / monovalent metal) is 0.25 to 1.0, preferably 0.30 to 0.9, more preferably 0.30 to 0.75. The polyvalent metal and the monovalent metal are all metals other than Group 1 metal elements of the periodic table contained in the polyamide composition (Group 2 to 13 elements of the periodic table, boron, aluminum, silica, Tin, lead) and Group 1 metals of the Periodic Table. When the molar ratio of the polyvalent metal to the monovalent metal (polyvalent metal / monovalent metal) is less than 0.25, the effect of suppressing the increase in yellowness or the change in molecular weight is not sufficient. If it exceeds the range, problems such as insufficient mechanical properties such as toughness tend to occur.

  In the present invention, it is preferable to contain 0.10 to 10 mol of phosphorus element, 0.10 to 10 mol of polyvalent metal and 0.10 to 10 mol of monovalent metal per 1,000,000 g of polyamide, and 0.20 to 5 phosphorus element. More preferably, it contains 0.20 to 7.5 mol of a polyvalent metal and 0.20 to 7.5 mol of a monovalent metal. By making each element in the above-mentioned range, there is a tendency that the increase in yellowness due to the heat history and the effect of suppressing the change in molecular weight, toughness and the like, which are the objects of the present invention, can be achieved.

  The methods for adding these phosphoric acid compounds and soluble metal aluminate salts include a method of adding to a raw salt aqueous solution of polyamide resin, a method of injecting and adding into a molten polymer in the middle of melt polymerization, and a polyamide obtained after completion of polymerization. Examples thereof include a method of adhering to the surface of the resin pellets, or a method of blending the pellets with phosphoric acid compounds and soluble metal aluminates and then kneading them using an extruder. The phosphoric acid compound and the soluble metal aluminate can be added to the same addition position selected from the above, or can be divided and added in two or more places selected from the addition positions. The method of adding to the raw salt aqueous solution is most suitable because it is simple and has high uniformity.

  The water content of the polyamide resin of the present invention is 0.1 wt% or more because the molecular weight is unnecessarily increased during melt kneading and shearing, and the effect of improving the color tone and thermal stability is not sufficient. Since the molecular weight of the polyamide is greatly reduced by hydrolysis, it is preferably 0.5 wt% or less, more preferably 0.15 to 0.5 wt%, and 0.2 to 0.4 wt%. Further preferred. The moisture content specified in the present invention is higher than the moisture content of the pellets used for normal melt-kneading. In this way, it is presumed that by increasing the moisture, excess moisture covers the surface of the composition such as pellets and acts as a protective film that prevents contact with air, thereby preventing oxygen absorption. .

The method for adjusting the moisture content of the polyamide resin includes a method in which the polyamide resin after melt polymerization is solidified by cooling with water and pelletized, and the immersion time in the water bath is made longer than usual. And a method of spraying mist-like water on the pellet, a method of spraying water vapor, a method of naturally absorbing the composition in the atmosphere, and the like. In particular, a method of spraying mist-like water on pellets is preferable because it can be easily set to an arbitrary moisture content and there is little uneven distribution of moisture. Moreover, it is preferable to process as early as possible after pelletization from the viewpoint of preventing oxygen adsorption.
In the present invention, the average particle size of the polyamide resin is preferably 1 mm or less, more preferably 0.5 mm or less, from the viewpoint of dispersion of silica particles, product transparency, appearance, and mechanical properties.

In the present invention, the polyamide resin having an average particle diameter of 1 mm or less and other polyamide resins can be mixed and used. In this case, from the viewpoint of dispersion of silica particles, a polyamide resin having an average particle size of 1 mm or less is preferably contained in an amount of 30% by weight or more, and more preferably 50% by weight or more.
The polyamide resin is usually in a pellet form. In order to obtain the polyamide resin of 1 mm or less, pelletized polyamide can be pulverized to obtain a polyamide resin having a particle size in the above range. If necessary, the polyamide resin may be cooled with liquid nitrogen or dry ice, frozen, and pulverized. The polyamide resin can be pulverized either dry or wet, and any pulverizer such as a ball mill, knife mill or hammer mill can be used.

The silica particles of the present invention are not particularly limited, but silica particles having an average particle diameter of about 1 to 15 μm well known in the art are used. Further, a surface treatment with a known surface treatment agent such as a silane treatment agent or a titanium treatment agent may be used.
The method for producing silica particles of the present invention can be roughly classified into two types: wet method silica and dry method silica. Any of the raw materials used in the present invention can be used.
The silica particle content in the silica particle-containing resin pellet in the present invention is 2 to 50 parts by weight.
The apparatus for performing melt kneading in the present invention is not particularly limited, and a known apparatus can be used. For example, melt kneaders such as single-screw or twin-screw extruders, Banbury mixers, and mixing rolls are preferably used. Among these, a twin-screw extruder equipped with a deaeration mechanism (vent) device and side feeder equipment is most preferably used.

The temperature of the melt kneading of the present invention is not particularly limited, but is preferably 250 to 350 ° C, more preferably 260 to 330 ° C.
The residence time for melt kneading is not particularly limited, but is preferably 0.5 to 15 minutes, more preferably 1 to 10 minutes, and most preferably 1.5 to 5 minutes.
In the present invention, it is preferable to melt-knead under reduced pressure from the viewpoint of further improving the color tone. The degree of vacuum is preferably 0 to 0.070 MPa.
Furthermore, the color tone of the silica particle-containing resin pellet can be measured using a color difference meter, and the color tone of the silica particle-containing resin pellet of the present invention is -5 to 15 as the b value (yellowness), preferably -5. -10.

In addition, the silica particle-containing resin pellets of the present invention can be melt-kneaded with other polyamide resins substantially free of silica particles.
In the present invention, a dispersant can be used to sufficiently disperse the silica particles in the polyamide resin. Examples of the dispersant include known higher fatty acid esters, higher fatty acid amides, and higher fatty acid metals.
When compounded using the above silica-containing resin pellets, a polyamide resin composition having an excellent color tone can be obtained.
Compounds include reinforcing materials such as glass fibers and carbon fibers, release lubricants, plasticizers, crystal nucleating agents, flame retardants, antioxidants, pigments, dyes and other additives, wollastonite, talc, kaolin, mica, etc. One or more inorganic fillers can be selected and used as necessary.

The present invention will be described more specifically with reference to the following examples and comparative examples, but the scope of the present invention is not limited thereto. The measurement method and evaluation method in the description of the present invention are as follows.
(1) Moisture content 0.7 g of a measurement sample was measured by a Karl Fischer method using a moisture vaporizer (VA-06 model, manufactured by Mitsubishi Chemical Corporation) under a temperature condition of 185 ° C.
(2) VR: Formic acid relative viscosity Measured according to ASTM D789. A polyamide resin was dissolved in 90% formic acid at a concentration of 1.0 g / 9.08 ml, and the measurement was performed at 25 ° C.
(3) Color tone of pellets Using a color difference meter ND-300A manufactured by Nippon Denshoku Industries Co., Ltd., L value, a value, and b value were measured by reflection measurement, and yellowness was determined by b value. The b value indicates that the higher the absolute value is-, the better the color tone is white, and the higher the absolute value is +, the more yellow the color is generated.

(4) Dispersion state of silica A sample having a thickness of 100 μm is cut out from the pellet by a microtome. This sample was magnified and observed with an optical microscope to determine the appearance.
A: There is no aggregation of silica particles and the particles are uniformly dispersed.
○: There is almost no aggregation of silica particles, and the dispersion state is uniform.
(Triangle | delta): Although there is almost no aggregation of a silica particle, there exists an uneven distribution location.
X: There is an aggregate of silica particles.
(5) Particle size of silica particles The particle size was measured with a laser particle size analyzer SALD1000 manufactured by Shimadzu Corporation.

[Example 1]
First, nylon 66 resin pellets were obtained by melt polymerization. This is a preconcentration of approximately 80% of a raw material obtained by adding 50 ppm of sodium hypophosphite and 100 ppm of sodium aluminate to the resulting polymer in an approximately 50% aqueous solution of an equimolar salt of adipic acid and hexamethylenediamine. Then, it was heated to about 250 ° C. in a polymerization tank, and condensed water was removed while pressurizing to about 17 atm to make a prepolymer. Then, it heated at about 280 degreeC, reducing pressure to atmospheric pressure, further removed condensed water, and the polymerization reaction was advanced. The molten polymer was discharged from the die to form a strand. The strand was passed through a cooling bath containing water, cooled and solidified, and cut to obtain a nylon 66 resin pellet. The obtained nylon 66 resin pellets were sent to a fluidized drying furnace and dried by flowing heated nitrogen in a countercurrent to produce nylon 66 resin pellets having a moisture content set to 0.10 wt%.
95% by weight of this nylon 66 resin pellet and 5% by weight of silica particles were melt-kneaded to prepare a silica-containing resin pellet. The silica particles used were melt kneaded at a temperature of 300 ° C. and a discharge rate of 10 kg / hr using a twin screw extruder (BT30 type) with a particle size of 2.7 μm (Sylicia 310P manufactured by Fuji Silysia Chemical). Furthermore, the evaluation result of the obtained silica containing resin pellet is shown in Table 1.

[Example 2]
The same operation as in Example 1 was performed except that nylon 66 resin pellets obtained by melt polymerization were not dried in a fluidized drying furnace. The evaluation results are shown in Table 1.

[Example 3]
Nylon 66 resin pellets obtained by melt polymerization were frozen and then pulverized to form nylon 66 resin powder having an average particle size of 0.5 μm, and then mixed with silica particles and melt-kneaded. The same operation was performed. The evaluation results are shown in Table 1.

[ Comparative Example 3 ]
Nylon 66 resin pellets obtained by melt polymerization were sent to a fluidized drying furnace, dried by flowing heated nitrogen countercurrently, and the moisture content was adjusted to 0.03 wt%. went. Table 1 shows the evaluation results of the obtained pellets.

[Comparative Example 1]
The same operation as in Example 1 was performed except that sodium aluminate was not added to the raw material salt. The results are shown in Table 1.

[Comparative Example 2]
The same operation as in Example 2 was performed except that 30 parts by weight of nylon 66 resin pellets and 70 parts by weight of silica particles were melt-kneaded. The evaluation results are shown in Table 1.

[Reference Example 1]
The same operation as in Example 1 was performed, except that no silica particles were added during compounding. The evaluation results are shown in Table 1.

  The present invention relates to a resin pellet containing silica particles having an excellent color tone. More specifically, the present invention relates to a silica particle-containing resin pellet that can be suitably used in sliding applications or film applications and has excellent color tone and thermal stability.

Claims (6)

At least one phosphorus compound (a) selected from the group consisting of phosphoric acids, phosphorous acids and hypophosphorous acids and / or their metal salts, general formula (M ₂ O) X (Al ₂ O ₃ ) Y ( However, the soluble aluminate metal salt (b) represented by X + Y = 1 and M is a metal element of Group 1 of the periodic table) and a polyamide resin having a water content of 0.1 wt% or more and 0.5 wt% or less (c) Tona is, the molar ratio of the polyvalent metal and the monovalent metal (polyvalent metal / monovalent metal), the polyamide resin composition is 0.30 to 1.0 (a) ninety-eight to fifty parts by weight Silica particle-containing resin pellets obtained by melting and kneading 2 to 50 parts by weight of silica particles (B).   The component (a) is at least one compound selected from phosphoric acid, phosphorous acid and hypophosphorous acid and / or a salt thereof with a Group 1 metal of the periodic table. 2. Silica particle-containing resin pellets according to 1.   (A) A component is sodium hypophosphite, The silica particle containing resin pellet of Claim 1 or 2 characterized by the above-mentioned. The silica particle-containing resin pellet according to any one of claims 1 to 3 , wherein the component (c) contains 30% by weight or more of a polyamide resin having an average particle size of 1 mm or less. The silica particle-containing resin pellet according to any one of claims 1 to 4 , wherein the component (c) is nylon 66 and / or nylon 66 / 6I. b value is 15 or less, The silica particle containing resin pellet in any one of Claims 1-5 characterized by the above-mentioned.