JPS6094459A - Powdery thermoplastic resin composition - Google Patents

Abstract

PURPOSE:A composition, obtained by incorporating a powdery metallic salt of a fatty acid having a bulk density and an average particle diameter within a specific range with a thermosetting resin, having improved release property in molding, capable of giving molded articles having remarkably smooth inner skin and improved mechanical strength without poor deforming, and suitable for rotary molding. CONSTITUTION:A powdery thermoplastic resin composition obtained by incorporating (A) 100pts.wt. powdery thermoplastic resin, preferably powdery polyethylene, obtained by suspension polymerization in the presence of a Ziegler catalyst, etc. and having 0.92-0.95g/cm<3> density, with (B) 0.02-1pts.wt., preferably 0.07-0.3pts.wt. powdery metallic salt of a fatty acid having 0.35-0.85g/cm<3>, preferably 0.4-0.7g/cm<3> bulk density and 5-500mu, preferably 10-500mu average particle diameter, passing through a 16-mesh screen, and having >=130 deg.C melting point as a lubricant, e.g. obtained by pulverizing mechanically calcium stearate, magnesium stearate, etc. produced by the melting method (dry method).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powdered thermoplastic resin composition suitable for powder molding, particularly rotary molding, which has excellent mold release properties during molding, has an extremely smooth inner surface, and is free from defoaming. The object of the present invention is to provide a raw material powder composition that provides a molded article with excellent mechanical strength.

In powder molding, typified by rotary molding, powdered thermoplastic resin obtained by some method is used, but moldability, especially pore filling and smoothness, depends on the particle size, particle size distribution, and particle shape of the powder used. There was a problem that it was inferior to Furthermore, as described in, for example, JP-A No. 57-38839, powdered polyethylene directly obtained by suspension polymerization has the disadvantage of poor mold release properties. In response to these issues, ■Japanese Patent Application Laid-Open No. 56-41213,
He proposed the use of powder with specific properties, and in JP-A-57-38839, he proposed a composition in which a lubricant such as a saturated fatty acid having a specific melting point range was mixed and dispersed in powdered polyethylene obtained by a suspension method. I suggest using
(1) Japanese Patent Laid-Open No. 58-84719 proposes the use of a mixture of mechanically pulverized pulverized polyethylene with a specific spherical powdered polyethylene. These proposals have the disadvantage that there are restrictions on the manufacturing method of the powder used, and as for (2), there is an upper limit on the melting point of the lubricant used, which limits what can be used.

The present inventors have developed a powder-form product in which a predetermined amount of a lubricant exhibiting predetermined powder properties is mixed and dispersed in powder molding, particularly rotary molding. : By using the plastic resin composition, there are no drawbacks as mentioned above, and it is only ¥1! It can be applied not only to powdered resins produced by turbid polymerization or gas phase polymerization, but also to powdered resins obtained by mechanically crushing pellets, etc. It has excellent mold release properties during molding, has an extremely smooth inner surface, and has no defoaming defects. It was discovered that a molded article having excellent mechanical strength can be obtained, and the present invention was completed.

In other words, in the present invention, powder having a bulk density of 0.35 to 0.85 g/cd, an average particle size of 5 to 500 μm, and passing through a 16-mesh sieve is added to 100 parts by weight of the powdered thermoplastic resin (A). fatty acid metal salt (B) 0.02 to 1
．． The gist of the invention is a powdered thermoplastic resin composition characterized in that 0 parts by weight are mixed and dispersed.

The powdered thermoplastic resin (A) constituting the composition of the present invention, which will be described in detail below, is not particularly limited to polyolefin, as long as it is a resin used for powder molding. These resins include various polyolefin resins such as low-density, medium-density, and high-density polyethylene, polypropylene, propylene-ethylene block copolymers, poly-1-butene, poly-4-methyl-1-pentene, etc. Various thermoplastics can be used, such as polycarbonate, polyphenylene oxide (PPO), acetal resin, polystyrene, ABS resin, ethylene-vinyl acetate copolymer, polyester resin, and polyamide resin. Among these, polyethylene is preferably used, especially low density and medium density polyethylene. In addition to ethylene homopolymers, these polyethylenes contain ethylene and α-olefins such as propylene, ■-butene, isobutyne, ■-pentene, and 4-
Methyl-1-pentene, 1-hexene, 1-octene,
Also included are copolymers with 1-decene and the like. One example of low-density polyethylene is usually obtained by high-pressure radical polymerization, and has a density of about 0.91 to about 0.9.
It is 3g/cot. Polyethylene in the low to medium density range is usually produced by solution polymerization using a Ziegler type catalyst.
It is obtained by a suspension polymerization method or a gas phase polymerization method, and has a density of about 0.91 to about 0.95 g/cM. Among these medium-low density polyethylenes, those obtained by suspension polymerization or gas phase polymerization are preferred for the reasons described below, and those with a density of 0.920 to 0.950 are particularly preferred.

The above-mentioned thermoplastic resin may be made into powder form by any method as described above, such as mechanically pulverizing resin pellets obtained by various polymerization methods, freeze-pulverizing, suspension polymerization, gas phase polymerization, etc. It is possible to use one directly manufactured by. However, mechanically pulverized powdered thermoplastic resins generally have a low bulk density, a high angle of repose, a wide particle size distribution, and often have irregular particle shapes.
It is preferable to use a powdered thermoplastic resin directly produced by suspension polymerization or the like. Furthermore, among these, the powder has a spherical or ellipsoidal shape or a shape close to these, and essentially does not contain filaments or whiskers, which makes the surface of the rotary molded product smooth, especially the details. Good for finishing. In addition, the properties of the resin that has been subjected to powder molding, especially rotational molding, are such that the bulk density is usually 0.3 to 0.6 g/ci,
Preferably 0.4 to 0.5 g/cJ, average particle size (
The particle size (50% particle size) is usually 150 to 400μ, and preferably 70% by weight or more of the total particle size is in the range of /15° to 400μ. In addition, in rotational molding, in order to increase the fluidity of the powder and ensure sufficient detail moldability, the angle of repose must be 1ffi, usually 25° to 4°.
5°, preferably 30° to 40°. Furthermore, the polyethylene listed as the above-mentioned preferred thermoplastic resin has a melt flow rate (MFR: 190'c).

2.161tg load] is usually 1 to 20g/10 minutes,
Preferably it is 2 to 10 g/min.

Next, the powdered fatty acid metal salt (B) will be explained. Examples of fatty acid metal salts used in the present invention include calcium stearate, magnesium stearate, lithium stearate, strontium stearate, barium stearate, zinc stearate, aluminum stearate, barium laurate, calcium laurate,
Examples include zinc laurate and calcium 12-hydroxystearate. Among these, calcium stearate, magnesium stearate, lithium stearate, and sodium stearate are preferably used for the reasons described below.

The fatty acid metal salts mentioned above can be used alone, or simply a mixture of two or more kinds, or a mixture of two or more kinds can be used. Furthermore, it is preferable that these fatty acid metal salts do not substantially contain free fatty acids, but they may contain a trace amount within a range that does not impair the effects of the present invention. In addition, as a fatty acid metal salt, the melting point (JIS KO
(according to O64) is preferably 80°C or higher, particularly preferably 130'C or higher. This is because if a material having a melting point of 80° C. or lower is used, these compounds will bleed more easily than in a powder molded product.

Furthermore, the powdered fatty acid metal salt (B) used in the present invention has a bulk density (measured according to JIS [6721) of 0.
It is essential that the particle size is 30 to 0.85 g/cl, preferably 0.40 to 0.85 g/cJ, more preferably 0.40 to 0.70 g/cJ, and the average particle size is 5 It is necessary to be in powder form with a thickness of 10 to 500μ, preferably 10 to 500μ. What is the average particle size here? The sieve residue test method using a sieve (JIS Z8801)
) is the 50% diameter of the cumulative distribution calculated from the cumulative distribution curve,
That is, it refers to the 50% particle size. Bulk density is 0.30g/cJ
If the size is smaller, air will easily be mixed into the powdered thermoplastic resin composition during rotary molding, and as a result, the molten inner layer will contain a large number of air bubbles during molding, making it difficult to defoam. This slows down the melting rate of the resin powder and significantly impairs the smoothness of the inner surface of the molded product.Also, the upper limit of the bulk density of 0.85 g/ca is determined by the average particle diameter obtained by the method described later. Based on the fact that the upper limit of the powdered fatty acid metal salt (B) in the essential range is 0.85 g/ca.Furthermore, if the average particle size is larger than 500μ, molding is required due to the particles of the fatty acid metal salt, etc. The above range is essential because the inner surface of the product will not be smooth.Also, if the average particle size is 5.
If it is less than μ, the bulk density will fall below the lower limit and the manufacturing cost will generally increase, which is disadvantageous.

In addition, the powdered fatty acid metal salt (B) was sieved through a 16-mesh sieve (T
yler standard sieve), particularly preferably a 32-mesh sieve. If particles that do not pass through a 16-mesh sieve are included, even if the bulk density and average particle size are within the above-mentioned essential ranges, the smoothness of the inner surface of the molded product will be impaired. In the following, the powdered fatty acid metal salt (
F is the mesh number of the sieve with the narrowest holes through which all B)
This will be referred to as particle size J.

Powdered thermoplastic resin (A) of powdered fatty acid metal salt (B)
) is the blending ratio of (A) to 100 parts of B.
) is 0.02 to 1.0 parts by weight, preferably 0
．． 0.05 to 0.5 parts by weight, more preferably 0.07 to 0.3 parts by weight. The blending ratio of (B) is 0.02
If it is less than 1 part by weight, there will be a problem that the molded product will not release from the mold, and if it is more than 1.0 part by weight, the smoothness of the inner surface of the molded product may be lost or the strength of the molded product may be impaired. Therefore, it must be within the above range. In addition, the composition of the present invention may contain, as long as it does not impair the effects of the present invention.
Various stabilizers, antioxidants, and
UV absorbers, antistatic agents, different types of lubricants, plasticizers, pigments, fillers, reinforcing agents,! Various additives such as refueling agents and mold release agents can be added.

Powdered thermoplastic resin (A) and powdered fatty acid metal salt (B)
A tumbler, ribbon blender, Henschel mixer, or the like is usually used to mix the ingredients to produce the composition of the present invention. The temperature of the composition during mixing is such that the resin or lubricant does not melt, usually from 0 to 100°C, particularly preferably from 10 to 70°C.

The powdered thermoplastic resin composition of the present invention is suitable for powder molding, particularly rotational molding. Powder molding generally involves placing resin powder in a sample mold according to the molded product and heating it from the outside.The resin powder inside is sintered along the mold surface to create an integral fusion product, and then the outside of the mold is heated. The molded product is removed from the mold after being cooled further. Powder compaction depends on the movement of the mold, heating method, etc. ■Engel method (static method) - 1 ■Hayashi process, ■One-axis rotation method such as Heisler method, ■Two-axis rotation method, ■Rockflor method (rotation method) Other methods include powder coating, in which powder is coated while rotating a heated substrate.

The composition of the present invention is suitable for any of the above-mentioned molding methods, but is particularly suitable for rotational molding methods such as (1), (2), (2), and (2).

Here, the powdered fatty acid metal salt (B
) manufacturing method will be explained. The powdered fatty acid metal salt (B) used in the present invention must have a predetermined average particle size as described above, and a relatively high bulk density of 0.30 to 0.85 g/c+d. . Such metal salts (B) are generally those obtained by mechanically pulverizing fatty acid metal salts produced by the melting method (also called dry method or direct method), which is one of the manufacturing methods for metal soaps. . This method is a method of producing metal oxides, hydroxides, or carbonates by direct heating reaction with fatty acids or fatty acid esters, and the pulverized product of the cooled and solidified reaction product cannot be used in the present invention. It has a bulk density that allows for. On the other hand, powdered fatty acid metal salts produced by the double decomposition method (also called double decomposition precipitation method or wet method), which is another method for manufacturing metal soaps, generally have a bulk density of 0.3 or less, and cannot be used as is. cannot be used for Powder with high bulk density can be obtained from powder of fatty acid metal salt with low bulk density by the following method.

The first method is to pressurize and compress the fatty acid metal salt powder at a temperature below its melting point, and then mechanically crush the powder, if necessary. As long as the temperature is below the melting point, the temperature is preferably as high as possible unless the fatty acid metal salt powder is melted by pressure compression. Although the compression pressure depends on the temperature, it is also desirable to use high pressure unless the fatty acid metal salt powder is melted. Various methods can be used for compression, specifically:
■Method of putting raw material powder in a certain mold and compressing it with a press, ■Method of introducing raw material powder between two rotating rolls and compressing it, or ■Method of putting powder in a cylinder and compressing it with a piston. etc. can be mentioned. Among these, method (2) is preferable in the comparative example since it is easy to obtain a large amount of powder with little unevenness in bulk density. The compressed product thus obtained is mechanically pulverized as required to obtain a powder having an average particle size etc. necessary for use in the present invention. Mechanical means include a feather mill, ball mill, crusher, and artificial means include grinding in a mortar.

The second method involves heating and melting a powdered fatty acid metal salt with a low bulk density to a temperature above its melting point under pressure or without applying pressure, preferably under an inert gas atmosphere, then cooling and solidifying it, and then melting it into a lump. The fatty acid metal salt is powdered by mechanical means similar to the first method described above.

The third method is to add polyolefin wax or saturated fatty acid glyceride (oil) to the fatty acid metal salt powder with low bulk density, heat and mix to a temperature above the melting point of the polyolefin wax or saturated fatty acid glyceride, and cool the paste mixture. solidify.

The amount added may be sufficient to make the molten mixture paste-like. The thus obtained lumps are made into powder by the same mechanical means as in the first method described above. Examples of the polyolefin wax used in this method include ethylene, propylene, 1-butene, 1-hexene,
- A homopolymer of α-olefin such as methyl-1-pentene or 1-decene or a copolymer of two or more α-olefins, which has an intrinsic viscosity (measured at 135°C in a decalin solvent) is usually in the range of 0.04 to 0.5 d1/g. Examples of saturated fatty acid glycerides include triglycerides of stearic acid and palmitic acid. Further, the heating conditions may be selected so that the mixture exhibits a paste-like state.

By using the powdered thermoplastic resin composition of the present invention, powder molding, especially rotary molding, has excellent mold release properties during molding, and there is no defective defoaming due to excessive inner skin, and rotary molding with excellent mechanical strength. Molded products can now be obtained.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 Chive 1? - Powdered polyethylene (A) produced by suspension polymerization with a catalyst (density 0, 943 g/cta,
To 100 parts by weight of melt index 4.5 g/10 minutes), calcium stearate (manufactured by Sanshaki Synthesis @,
Bulk density 0, 22g/cc, particle size 200 mesh,
Metathesis method) was placed in a circular drop mold (diameter 20 cm) and compressed under pressure (150 kg/CA) at room temperature using a press molding machine to solidify it, and then crushed using a ball mill to obtain a bulk density of 0. .46g/cc powdered calcium stearate (particle size 100mesh, average particle size 50μ) 0.15
Parts by weight were added as a lubricant and mixed for 3 minutes at room temperature using a Henschel mixer. Add r to 4 of the obtained powder polyethylene composition in a steel plate mold (vertical 30cm x horizontal 30cm).
cm x depth of 40 cm), set it in a two-shaft rotary molding machine, heated it from the outside of the mold with a propane gas burner for 10 minutes, then left it to cool naturally for 5 minutes, cooled it in water for 2 minutes, and then molded it. finished. The releasability, defoaming state, and inner skin state of the obtained molded product were observed.

In addition, in order to examine the adverse effect of small bubbles inside the molded product, which are difficult to observe, on the physical properties of the product, a test piece from the molded product was punched out using an ASTM No. 4 Danher and a tensile test was conducted to examine the elongation until breakage.

The results are shown in Table 1 (the same applies to the following Examples and Comparative Examples).

Example 2 In Example 1, powder polyethylene (B) produced by suspension polymerization using a Ziegler catalyst (density 0.935 g
Rotational molding was carried out under the same conditions as in Example 1, except that the molding was performed using the following methods:

Comparative Example 1 In Example 1, calcium stearate (manufactured by Sankyoki Synthesis@, bulk density 0.22 g/cc, particle size 200 mesh, double decomposition method) was used as a lubricant in a circular drop mold (diameter 2
0 cm) and pressurized (30 cm) at room temperature using a press molding machine.
kg/cut) was compressed and solidified, and then crushed to obtain a powder with a bulk specific gravity of 0.34 g/cc (particle size: 200 mesh).
Rotational molding was carried out under the same conditions as in Example 1, except that particles with an average particle diameter of 10 μm were used.

Example 3 In Example 1, calcium stearate (manufactured by Sankyoki Synthesis, bulk density 0.22 g/cc, particle size 200 mesh, double decomposition method) was used as a lubricant in a circular drop mold (diameter 2
0 cm) and compressed using a press molding machine at a temperature of 100°C under pressure (150 kg/csl =
Rotational molding was carried out under the same conditions as in Example 1, except that a particle size of 80 mesh and an average particle size of 80 μm were used.

Example 4 In Example 1, as a lubricant, calcium stearate (Sankyo-synthesized (manufactured by Kiki, bulk density 0.22 g/cc, double decomposition method) was placed in a circular drop mold (diameter 4 cm) and the press molding machine was turned on. pressure (150 kg/c) at a temperature of 100°C using
Rotational molding was carried out under the same conditions as in Example 1, except that a powder with a bulk density of 0.63 g/cc (particle size 80 mesh, average particle size 100 μ) obtained by compressing and solidifying and crushing was used. Ta.

Example 5 In Example 1, as a lubricant, calcium stearate (trivalent synthesis (4 grade, bulk density 0.22 g/cc,
A powder with a bulk density of 0.57 g/cc (particle size of 100 me
Rotational molding was carried out under the same conditions as in Example 1 except that sh, average particle size: 50 μm) was used.

Example 6 In Example 1, calcium stearate produced by a direct method (manufactured by NOF@, bulk density 0.60) was used as a lubricant.
g/cc, particle size 16 mesh, average particle size 500 p)
Rotational molding was carried out under the same conditions as in Example 1, except that the sample was used as it was.

Example 7 In Example 1, calcium stearate produced by a direct method (manufactured by NOF@, bulk density 0.42) was used as a lubricant.
Rotational molding was carried out under the same conditions as in Example 1, except that the particles (g/cc, particle size: 200 mesh, average particle size: 10 μm) were used as they were.

Example 8 In Example 1, a small amount of triglyceride stearate was added as a binder to calcium stearate (manufactured by Sankyoki Gosei, bulk density 0.22 g/cc, double decomposition method) as an aggregation agent to obtain a bulk density of 0.40 g. /cc powder (particle size: 32 mesh, average particle size: 100 μm) was obtained, and rotational molding was performed under the same conditions as in Example 1, except that this powder was used.

Comparative Example 2 In Example 1, metathesis method calcium stearate (manufactured by Sankyoki Synthesis, bulk density 0.22 g/c) was used as a lubricant.
Rotation molding was carried out under the same conditions as in Example 1, except that the powder (particle size 200 mesh) was added as it was to powdered polyethylene and mixed using a piece.

Comparative Example 3 1 In Example 1, calcium stearate (manufactured by Sankyoki Gosei@, bulk density 0.22 g/cc) was placed in a circular drop lid (diameter 20 cm) and pressurized at 100°C using a press molding machine (150 kg). Example 1 except that a powder with a bulk density of 0.75 g/cc and an average particle size of 800 μ (particle size 14 mesh) obtained by compressing, hardening, and pulverizing was used as the exfoliant. Rotational molding was carried out under the same conditions.

Comparative Example 4 Rotational molding was carried out under the same conditions as in Example 1, except that the powdered polyethylene was rotomolded as it was without adding any lubricant.

Example 9 In Example 1, sodium stearate (manufactured by NOF ■, bulk density 0.34 g/cc) was melted and then cooled and solidified, and the lump was crushed to iM with a bulk density of 0.47 g/cc.
Rotational molding was carried out under the same conditions as in Example 1, except that powder (particle size: 100 mesh, average particle size: 50.c+) was used as a lubricant.

Comparative Example 5 Rotational molding was carried out under the same conditions as in Example 1, except that sodium stearate (manufactured by NOF ■, bulk density 0.32 g/cc) was used as a lubricant.

Example 10 In Example 2, lithium stearate (NOF@
A powder with a bulk density of 0.51 g/cc (particle size 8Q mesl+, average particle size 80 μ) obtained by crushing the solidified lump by cooling and crushing it (f4j) was used as a lubricant. Rotational molding was carried out under the same conditions as in Example 2, except that the sample was used as a sample.

Comparative Example 6 In Example 2, rotational molding was carried out under the same conditions as in Example 2, except that metathesis method lithium stearate (manufactured by NOF@, bulk density 0.21 g/cc) was used as a lubricant.

Example 11 In Example 2, bulk density 0.5 was obtained by melting magnesium stearate (manufactured by NOF@, bulk density 0.17 g/cc, double decomposition method) and then crushing the solidified lump by cooling.
4g/cc powder (particle size 100mesh, average particle size 50
Rotational molding was carried out under the same conditions as in Example 2 except that μ) was used as a lubricant.

Example 12 In Example 2, zinc stearate produced by a direct method (manufactured by NOF@, bulk density 0.48 g/c) was used as a lubricant.
Rotation molding was carried out under the same conditions as in Example 1, except that the sample (c, particle size: 80 mesh, average particle size: 80 μm) was used as it was.

Comparative Example 7 In Example 2, metathesis method magnesium stearate (manufactured by NOF ■, bulk density 0.17 g/cc) was used as a lubricant.
) was used as it was, but rotational molding was performed under the same conditions as in Example 2.

Comparative Example 8 In Example 2, rotational molding was carried out under the same conditions as in Example 2, except that the powdered polyethylene was rotomolded as it was without adding any lubricant.

Claims (1)

[Scope of Claims] (]) 100 parts by weight of powdered thermoplastic resin (A) has a bulk density of 0.35 to 0.85 g/cJ and an average particle size of 5
1. A powdery thermoplastic resin composition comprising 0.02 to 1.0 parts by weight of a powdered fatty acid metal salt (B) having a particle size of 500 μm to 500 μm and passing through a 16-mesh sieve. (2) The powdered thermoplastic resin composition according to claim (1), wherein the fatty acid metal salt (B) has a melting point of over 130°C.