JPS61200141A - Powdery polyethylene resin composition and its production - Google Patents

Abstract

PURPOSE:To composition that is composed of polyethylene and a specific (un)saturated higher fatty acid, thus being suitable for use in powder coating such as fluidization dip coating or spraying, because the composition has good fluidity and good coating film surface slip properties. CONSTITUTION:The objective composition is composed of (A) 100pts.wt. of polyethylene and (B) 0.003-2.0pts.wt. of at least one selected from saturated and unsaturated higher fatty acids of 8-22 carbon atoms. Component B is added to component A, the mixture is mechanically crushed and heated, simultaneously or after crushing, in the temperature range from 60 deg.C to the melting point f component A. Or, after crushing, the mixture may be heat-treated, as it is mixed by means of mechanical shear force. The component B is preferably of 10-22 carbon atoms, e.g., caprylic acid, lauric acid or erucic acid. Preferably component B is kneaded into component A.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a powder polyethylene resin composition and a method for producing the same. More specifically, the present invention
A powder polyethylene resin composition with improved fluidity and coating film surface smoothness, which is particularly suitable for powder coating by fluid dipping, electrostatic powder coating, or spraying, and which can be used industrially. Advantageously, it relates to a method of manufacturing.

Conventional technology Powder polyethylene has been known to be a material with excellent weather resistance, chemical resistance, impact resistance, etc., and powder coating using this material has advantages that bath coating does not have, such as Because of its advantages such as high coating efficiency and the ability to coat a thick film in one go, research into its application has been actively conducted in recent years, and with the development of technology, its applications, mainly for rust prevention, have been actively conducted. The scope is being expanded.

By the way, when using bonoethylene resin for powder coating, it is required not only that the resin itself has excellent physical properties but also that the resin has excellent fluidity when made into powder.

For example, in the fluidized soaking method, powder is placed in a tank containing a porous material, and air is introduced from below the porous material to form a fluidized bed. The resulting coating film will be non-uniform.

In the electrostatic powder coating method, if the fluidity of the powder is poor, not only will it be difficult to transport the powder by air from the powder storage tank to the coating gun, but the charged particles will not be uniformly coated. Since it does not adhere to the painted object, it is not possible to obtain an excellent coating film.

The fluidity of such polyethylene powder is a problem not only for the purpose of coating but also for the purpose of rotary molding and fiber processing, for example.

Up to now, many methods have been proposed to obtain powdered polyethylene resin, but these can be roughly divided into chemical pulverization methods, which involve dissolving in a solvent, etc., and mechanical grinding, impact, etc. This is a mechanical crushing method that involves applying force.

In the chemical grinding method, a powder with relatively rounded particle shape and good fluidity can be obtained, but it is costly due to the use of solvent, is dangerous, and decreases in physical properties due to residual solvent. This involves problems such as difficulty in uniformly blending additives such as pigments.

On the other hand, in the mechanical pulverization method, a powder with a uniform composition can be obtained by kneading additives such as pigments into polyethylene using an extruder or the like in advance. This inevitably leads to a decline in liquidity. In order to suppress the occurrence of such whiskers, a method has been proposed in which powdered polyethylene with good fluidity is obtained by mechanically crushing it while cooling it using liquid nitrogen, but this method is expensive. It is extremely bulky and unsuitable for industrial implementation.

Furthermore, methods for improving the fluidity of polyethylene powder include a method of blending additives (Japanese Patent Publication No. 53-1778) and a method of heat-treating the powder (Japanese Patent Publication No. 50-115265).
No. 2) has been proposed. However, in the former case where additives are added, the fluidity of the powder is improved considerably, but the surface smoothness of the product coated with the powder becomes excessive.
When packaging, transporting, and storing products, it is inevitable that various troubles will occur, such as, for example, products being stacked and causing the product to shift. On the other hand, in the latter case, the effect is insufficient and satisfactory powder fluidity is not necessarily obtained.

In this way, powder polyethylene compositions that have good fluidity as a powder and do not impart too much lubricity to the surface of products coated with the powder have been developed in terms of both economic and performance considerations. The reality is that nothing that is fully satisfactory has been found.

Problems to be Solved by the Invention Under these circumstances, the object of the present invention is to provide a powder polyethylene resin composition with improved fluidity and coating surface smoothness, which is particularly suitable for powder coating. The object of the present invention is to provide a product and a method for producing the same industrially and advantageously.

As a result of extensive research, the inventors of the present invention have found that a specific additive is added to polyethylene in a predetermined ratio, and the mixture is mechanically pulverized at the same time or under certain conditions after the pulverization. It has been discovered that the above object can be achieved by heat-treating the material, and based on this knowledge, the present invention has been completed.

That is, the present invention provides a powdered polyethylene resin consisting of polyethylene 100 parts and 0.003 to 2.0 parts of at least one selected from saturated and unsaturated higher fatty acids having 8 to 32 carbon atoms. The higher fatty acid is added to the composition and polyethylene in the above ratio, and then the mixture is mechanically pulverized and simultaneously or after pulverization, heated at a temperature in the range of less than the melting point of the polyethylene and 60° C. or more. The present invention provides a method for producing the powder polyethylene resin composition by processing the powder polyethylene resin composition.

The polyethylene used in the present invention mainly includes homopolymers such as high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, etc. whose main component is manufactured by a high-pressure method, a medium-pressure method, or a low-pressure method. However, these copolymers and those treated with grafting, chlorination, saponification, oxidation, etc. can also be used.
2, preferably 10 to 22 saturated or unsaturated higher fatty acids, such as caprylic acid,
Examples include lauric acid, myristic acid, palmitic acid, stearic acid, araxic acid, behenic acid, myristoleic acid, linoleic acid, oleic acid, arachidonic acid, and erucic acid. Each of these may be used alone, or
Two or more types may be mixed and used.

The amount of the higher fatty acid used in the present invention is 0.003 to 2.01 parts by weight, preferably 0.005 to 1.0 parts by weight, and more preferably 0.01 to 0.5 parts by weight, per 100 parts by weight of polyethylene. The amount is in the range of parts by weight.

If this amount is less than 0.003 parts by weight, the fluidity improving effect of the powder composition will not be sufficiently exhibited, and if it exceeds 2.0 parts by weight, the strength of the molded object obtained from the powder composition will decrease. Or, if powder coating is applied to metal, etc., the adhesive strength may decrease.

In the present invention, a mixture in which the higher fatty acid is added to polyethylene in the above ratio is mechanically pulverized and simultaneously heat-treated at a temperature in the range of 60°C below the melting point of the polyethylene, or mechanically pulverized. After that, heat treatment is performed under the above temperature conditions.

For this mechanical pulverization, any pulverizer selected from those commonly used for resin pulverization can be used.

When the mixture is mechanically pulverized and heat treated at the same time, the temperature of the pulverizing chamber of the pulverizer may be controlled within the above range. This temperature can be accurately controlled by controlling the amount of air flowing into the grinding chamber, the amount of grinding per unit time, the number of rotations of the blades, the gap between the blades, etc. However, since the control factors differ depending on the type of grinder, Care must be taken to ensure that the temperature is within the above range.

Therefore, the heat treatment is performed after mechanically pulverizing the mixture.
It is preferable to do so. This heat treatment may be carried out by simply leaving the powder in a hot air dryer, or may be carried out in a tumbler or ribbon blender equipped with a heating device.
A method that uses a device with a blade-like material inside the device, such as a Hennel mixer or a Polytsunya device, and utilizes the heat generated by the mechanical threshing action of the high-speed rotation of the blade-like material, is used to equalize the temperature and It is optimal because it has advantages such as ease of control and high-speed heating.

In such heat treatment, if the treatment temperature is less than 60°C, a powder composition with sufficiently good fluidity cannot be obtained. On the other hand, if the temperature exceeds the melting point of the polyethylene used for convenience, the particles will fuse together, making it impossible to obtain the desired powder composition and also making it impossible to smoothly operate the apparatus. Note that the temperature in the heat treatment after mechanical pulverization refers to the surface temperature of the powder in the processing device.

Further, as a method for adding the higher fatty acid to polyethylene, it is preferable to knead the higher fatty acid into polyethylene in advance, but the higher fatty acid and polyethylene may be dry-bundled during or before pulverization.

If desired, commonly used additives such as dyes and pigments, weathering agents, antistatic agents, heat stabilizers, etc. can be added to the composition of the present invention.

The fluidity of the powdered polyethylene resin composition obtained in this way can be determined by placing the powder in a powder fluidization tank having a perforated plate at the bottom and allowing air to flow in from the bottom. , the minimum amount of air [Q
It can be evaluated using the value (t/min).

Powder with good fluidity, high bulk density, Q
The value becomes smaller. With such powder, when the powder is placed in a fluidized bath and the fluidized bath is formed with air, a uniform fluidized bed with little channeling or bubbling can be obtained.For example, when coating by fluidized dipping method, A coating film with good smoothness can be obtained.

In addition, the slipperiness of the coated product obtained using the powder polyethylene resin composition of the present invention can be determined by, for example, forming a coating film on an iron plate by a fluidized dip coating method, and then applying two coated plates so that the coated surfaces are in contact with each other. It can be evaluated based on the sliding angle between the coated surfaces.

The larger the slip angle, the smaller the slip on the painted surface.

Effects of the Invention The powder polyethylene resin composition of the present invention has extremely good fluidity and is particularly suitable for powder coating by fluidized dipping, electrostatic powder coating, spraying, and the like. In addition, since the coating film obtained from the composition has a suitable surface smoothness, troubles such as shifting of the load are less likely to occur when products having this coating film are stacked.

Furthermore, since the powder composition of the present invention has excellent fluidity, it can be used not only in the coating field but also in the rotary molding field, for example.
It is also suitably used in the field of interlining and dispersion methods in textile processing.

Further, according to the method of the present invention, a powder polyethylene resin composition having such characteristics can be obtained with great industrial advantage.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples.0 In addition, the bulk density, Q value, and sliding angle between coated surfaces of the powder composition were determined, and the flow state was evaluated in the following manner. .

(1) Bulk density 0 (2) Q value determined according to JIS K-6721 Powder compositions 1 and 5 K9 were put into a fluidized tank with a diameter of 200 mm and a height of 40 (Mm), which had a perforated plate at the bottom. More air was allowed to flow in, and the minimum air-IQ value (17 min) at which the composition started to have good fluidity was determined.

(3) Sliding angle between painted surfaces thickness Q, 3 mm iron plate C70X 150 mm)
A 400 micron coating film is formed on each of the two sheets using the fluidized dip coating method, and the two painted steel sheets are stacked so that the painted surfaces are in contact with each other. Ii,',,l: The iron plate was fixed, a load, i 500 F weight was placed on top of the upper painted iron plate, one end was gradually raised, and the angle at which the upper painted iron plate started to slide was determined. .

(4) Fluidized state The powder composition was placed in a fluidized tank and the fluidized state was evaluated in the following three stages.

◎: No bubbling or channeling is observed, showing a uniform and excellent fluidity state.

○: Although small bubbling etc. are observed, a relatively good fluidity state is shown.

X: No fluidized bed is formed at a Q value of 8017 minutes.

Examples 1 to 3, Comparative Examples 1 to 3 100 parts by weight of low-density polyethylene (manufactured by Asahi Kasei Kogyo Co., Ltd., trade name Santic LD M-6525), 2.5 parts by weight of titanium oxide as a white pigment, and stearic acid as a higher fatty acid. (Reagent-grade) were added in the proportions shown in Table 1, melt-kneaded using an extruder to uniformly blend, and granulate. Next, this granular material was pulverized using a Turbo Mill PP-8 pulverizer (manufactured by Pohlmann) while controlling the temperature in the pulverizing chamber at 70°C, and then a 60-mesh sieve was used to determine the particle size that passed through the sieve. A powder polyethylene composition having the following properties was obtained.

The bulk density, Q value, and sliding angle between coated surfaces of this powder composition were determined, and the fluidity state was evaluated. The results are shown in Table 1.

In addition, for comparison, a powder polyethylene composition (Comparative Example 1) obtained by pulverizing a granular material containing pg without the addition of stearic acid under the same pulverizing conditions as above, and a granular material having the same composition as in Example 2. The performance of each powdered polyethylene composition (Comparative Example 2) obtained by controlling the temperature in the grinding chamber at 50° C. was determined in the same manner, and the results are shown in Table 1.

Furthermore, a powder polyethylene composition was obtained in exactly the same manner as in Example 2 except that oleic acid amide was used in place of 1-stearic acid in Example 2 (Comparative Example 3), and each performance was determined for this composition as well. . The results are shown in Table 1.

Examples 4 to 6 Example 2 except that behenic acid, palmitic acid and erucic acid were used instead of stearic acid, respectively.
A powder polyethylene composition was obtained in exactly the same manner as in Example 2, and its properties were determined. The results are shown in Table 2.

Examples 7 to 9 In Example 2, instead of low-density polyethylene, ethylene/vinyl acetate copolymer (manufactured by Mitsui Polychemical Co., Ltd., trade name: Evaflex 560), high-density polyethylene (manufactured by Asahi Kasei Corporation, trade name: Santic) HDJ-320F) and linear low-density polyethylene (manufactured by DuPont, trade name Sflare-2114) were used, and the temperature of the grinding chamber was set to 3.
A powder polyethylene composition was obtained in exactly the same manner as in Example 2, except for the changes shown in the table, and each property was determined. The results are shown in Table 3.

Examples 10 to 11, Comparative Examples 4 to 6 Granules having the same composition as in Example 2 were milled using a Turbo Fine Mill TF-450 type (manufactured by Turbo Kogyo Co., Ltd.) pulverizer.
After pulverizing the mixture while controlling the temperature in the pulverizing chamber at 50° C., a powder polyethylene composition having a particle size that could pass through a 60-mesh sieve was obtained. Each property of this product was determined, and the results are shown in Table 4 as Comparative Example 4.

The powder polyethylene composition thus obtained was
Each property was determined for the powdered polyethylene composition that was left to stand in a hot air dryer controlled at 8 to 99°C for 15 minutes, then heat-treated and then allowed to cool to room temperature, and the results were used in Example 1o. are shown in Table 4.

The powdered polyethylene composition of Comparative Example 4 was processed using a polisher device (which is directly connected to a mixing device having mechanical shearing force).
(manufactured by Turbo Kogyo Co., Ltd.) and heated and mixed at 85° C. to obtain a continuously heat-treated powder polyethylene composition. Each property of this product was determined, and the results are shown in Table 4 as Example 11.

For comparison, a heat-treated powder polyethylene composition was obtained in the same manner as in Example 11, except that the heat-mixing temperature was changed to 55°C. Each property of this product was determined, and the results are shown in Table 4 as Comparative Example 5.

Furthermore, in Example 11, a heat-treated powder polyethylene composition was obtained in exactly the same manner as in Example 11, except that higher fatty acids were not added +JO. Each property of this product was determined, and the results are shown in Table 4 as Comparative Example 6.

Claims (1)

[Scope of Claims] 1. 100 parts by weight of polyethylene and at least one selected from saturated and unsaturated higher fatty acids having 8 to 32 carbon atoms.
A powder polyethylene resin composition comprising 0.003 to 2.0 parts by weight of seeds. 2 Carbon number 8 to 32 per 100 parts by weight of polyethylene
0.003 to 2.0 parts by weight of at least one selected from saturated and unsaturated higher fatty acids are added, and the mixture is then mechanically pulverized at the same time or after the pulverization, below the melting point of the polyethylene, A method for producing a powder polyethylene resin composition, the method comprising heating at a temperature in the range of 60° C. or higher. 3. The manufacturing method according to claim 2, wherein the mixture of polyethylene and higher fatty acids is mechanically pulverized, and then the powder is heat-treated while being mixed using mechanical shearing force.