GB2077272A - Enlarged Powder Particles of Crystalline Polyolefin and Method of Producing the Same - Google Patents
Enlarged Powder Particles of Crystalline Polyolefin and Method of Producing the Same Download PDFInfo
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- GB2077272A GB2077272A GB8112731A GB8112731A GB2077272A GB 2077272 A GB2077272 A GB 2077272A GB 8112731 A GB8112731 A GB 8112731A GB 8112731 A GB8112731 A GB 8112731A GB 2077272 A GB2077272 A GB 2077272A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J3/00—Processes of treating or compounding macromolecular substances
- C08J3/12—Powdering or granulating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B9/00—Making granules
- B29B9/16—Auxiliary treatment of granules
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
Abstract
Enlarged powder particles of crystalline polyolefin are obtained from the welding of crystalline polyolefin powder particles with one another at a mutual welding temperature, while the powder particles are subjected to a rate of mutual travel which is sufficient to prevent conglomeration. The crystalline polyolefin powder particles to be enlarged have an average particle size of smaller than 30 mesh (Tyler) and a viscosity-average molecular weight of at least 50,000 and are prepared by one-step or multi- step suspension polymerization or gas phase polymerization.
Description
SPECIFICATION
Enlarged Powder Particles of Crystalline
P.olyolefin and Method of Producing the Same
The present invention relates to enlarged fine powder particles of crystalline polyolefin prepared by suspension polymerization or gas phase polymerization and, also, relates to a method of enlarging fine powder particles of crystalline polyolefin at relatively low energy.
Crystalline polyolefin is generally used in the form of pellets due to their easy handling properties when the crystalline polyolefin is utilized in conventional molding techniques such as various types of extrusion molding, injection molding and the like. These pellets are produced by extruding resins through die-holes by using various type extruders, followed by pelletizing by using a strand cut method or an underwater cut method. However, when the polyolefin is obtained in the form of fine powder particles as prepared by suspension polymerization or gas phase polymerization, the energy consumption required for the pelletizing step comprises a major portion of the energy cost for the production of the polyolefin in the form of pellets. Especially when high-molecular weight resins are pelletized through melt extrusion, the energy consumption is remarkably high.Accordingly, the energysaving in the pelletizing step is eagerly desired in the art due to the recent rapid increase in the price of energy.
Known processes for pelletizing thermoplastic resin powder particles without using an extruder include, for example, a powder compacting process in which powder particles are pelletized under compression. However, since the particle strength of the pellets so obtained is not sufficient, there is a problem in that the pellets are likely to be broken or crushed during transportation. In order to obviate this problem, a binder can be used to improve the particle strength. However, the desired resin properties are undesirably changed by the use of a binder.
Furthermore, we proposed a preparation of uniformly dispersed powder particles in Japanese
Laid-Open Patent Application No. 48-1 1336/73 in which a mixture of the powder particles of crystalline thermoplastic resins obtained by suspension polymerization with inorganic fillers is stirred at a temperature of at least crystallization temperature but less than a mutual welding temperature as defined hereinbelow. However, according to this proposed method, the powder particles are not enlarged due to the fact that the powder particles are mixed with one another at a temperature of less than the mutual welding temperature. In addiition, it was believed heretofore that powder particles readily become massive bulk material.or conglomerates when they are stirred at a temperature higher than the mutual welding temperature.
However, we have found that the highmolecular weight crystalline polyolefine has a large elasticity when it is melted and does not readily cause the viscous flow under no load.
In accordance with the present invention, there are provided enlarged powder particles of crystalline polyolefin obtained from the welding of crystalline polyolefin powder particles with one another, said crystalline polyolefin powder particles having an average particle size of smaller than 30 mesh (Tyler) and a viscosity-average molecular weight of at least 50,000 and being prepared by one-step or multi-step suspension polymerization or gas phase polymerization and the particle size of the enlarged powder particles being larger than that of the starting crystalline polyolefin powder particles.
In accordance with the present invention, there is also provided a method of enlarging powder particles of crystalline polyolefin having an average particle size of smaller than 30 mesh (Tyler) and a viscosity-average molecular weight of at least 50,000 and being prepared by onestep or multi-step suspension polymerization or gas phase polymerization comprising the steps of:
(i) treating said crystalline polyolefin powder particles under a mutual welding temperature condition to enlarge the crystalline polyolefin powder particles, while the powder particles are subjected to a rate of mutual travel sufficient to prevent the conglomeration of the powder particles due to the complete mixing of the molten powder particles and, then,
(ii) cooling the resultant crystalline olefin powder particles.
The present invention will be better understood from the description set forth below with reference to the accompanying drawings in which:
Fig. 1 is a phase contrast photomicrograph (magnified 30 times) of the high-density polyethylene powder particles having a viscosityaverage molecular weight of 280,000 used in
Example 1 hereinbelow at room temperature;
Fig. 2 is a phase contrast photomicrograph (magnified 30 times) of the polyethylene powder particles of Fig. 1 after allowing it to stand for 1 5 minutes at a temperature of 1 500C; Fig. 3 is a phase contrast photomicrograph (magnified 30 times) of the high-density polyethylene powder particles having a viscosityaverage molecular weight of 30,000 used in
Comparative Example 1 hereinbelow;;
Fig. 4 is a phase contrast photomicrograph (magnified 30 times) of the polyethylene powder particles of Fig. 3 after allowing it to stand for 30 seconds at a temperature of 1 50 C; Fig. 5 is a scanning type electron photomicrograph (magnified 30 times) of the enlarged powder particles obtained in Example 1 hereinbelow;
Fig. 6 is a scanning type electron photomicrograph (magnified 30 times) of the enlarged powder particles obtained in Example 2 hereinbelow; and
Fig. 7 is a scanning type electron photomicrograph (magnified 30 times) of the cross-section of the enlarged powder particles of
Fig. 6.
The crystalline polyolefins used in the present invention include, for example, high-density polyethylene, medium-density polyethylene, lowdensity polyethylene, crystalline polypropylene, polybutene, poly(4-methyl-pentene-1 ) and the like as well as crystalline ethylene-propylene copolymer, ethylene-a-olefin copolymer, propylene-cg-olefin copolymer, ethylenebutadiene copolymer and the like. These crystalline polyolefins can be prepared in the form of powder by using an anionic coordination polymerization catalyst such as a Ziegler catalyst according to a suspension polymerization process or gas phase polymerization process. These crystalline polyolefins can be used alone or in any mixture thereof in the present invention.
The crystalline polyolefins used if the present invention are fine powder particles having an average particle size of smaller than 30 meshes.
The term "mesh" used herein means a Tyler mesh. Since these powder particles generally have a low bulk density, these powder particles have disadvantages that the transportation cost is high, the working conditions in the molding process become worse due to the flying of the dust particles and the decrease in the productivity is caused due to the fact that the feeding of the powder particles into an extruder is poor and nonuniform. Therefore, these powder particles cannot be used in the molding operation in the same way as the pellets can be used.
The crystalline polyolefin powder particles used in the present invention are those which have a viscosity-average molecular weight of 50,000 or more, more preferably 150,000 or more. In the case where the viscosity-average molecular weight of the crystalline polyolefin is smaller than 50,000, the powder particles readily cause a viscous flow to form massive bulk material or conglomerates in the form of glutinous rice jelly. Accordingly, the desirable viscosityaverage molecular weight of the crystalline polyolefin is as high as possible and ultra high molecular weight polyethylene powder particles even having a viscosity-average molecular weight of 1,000,000 or more can be enlarged.However, it should be noted that a higher temperature and a longer time are required in the enlargement of the powder particles, as the viscosity-average molecular weight of the powder particles becomes high and, also, that sufficient rate or pressure should be imparted to the powder particles to obtain enlarged powder particles - having a high bulk density.
The powder particles which are relatively easy to enlarge are the powder particles of the crystalline polyolefin prepared by suspension polymerization or gas phase polymerization comprising (i) 40 to 100% by weight of a high molecular weight component of which individual particles do not cause viscous flow deformation upon melting even when they are heated, under no load, to a temperature of at least the melting point thereof but less than 200C higher than the melting point thereof and (ii) O to 60% by weight of a low molecular weight component of which individual particles cause a viscous flow deformation upon melting under the above mentioned conditions.Furthermore, the powder particles of crystalline polyolefin comprising 30 to 100% by weight of the high molecular weight crystalline polyolefin powder particles having a viscosity-average molecular weight of 150,000 or more and 0 to 70% by weight of the low molecular weight crystalline polyolefin powder particles having a viscosity-average molecular weight of 1000 to 100,000 can be used in the present invention. Especially, the powder particles of crystalline polyolefin comprising 40 to 90% by weight of high molecular weight crystalline polyolefin powder particles having a viscosityaverage molecular weight of 200,000 to 1,000,000 and 10 to 60% by weight of low molecular weight crystalline polyolefin powder particles having a viscosity-average molecular weight of 5,000 to 50,000 can be desirably used in the present invention.The powder particles having the different viscosity-average molecular weight portions can be present in such a state that each particle is individually present or that many particles are adhered to one another. In the latter case, both particles having different viscosity-average molecular weight portions can be adhered to each other in such a state that both particles appears in the surface of the adhered particles or that one of the particles having a different molecular weight portion is wrapped or surrounded with the other or vice versa.
Since the above mentioned powder particles having different molecular weight portions contain powder particles whose viscous flow deformation occurs with difficulty at a melting temperature range under no load and powder particles whose viscous flow deformation easily occur, these powder particles can be readily enlarged and, also, enlarged powder particles having a high bulk density can be readily obtained. In the case where the proportion of the high molecular weight powder particles in the powder particles is smaller than the upper limit of the above mentioned range, the powder particles are liable to become massive bulk material and are difficult to granulate even when an appropriate temperature and mutual travel rate are imparted to the powder particles to be enlarged.
The above mentioned powder particles can be prepared during polymerization by either one step continuous polymerization or two or more step (i.e. multi-step) continuous polymerization, or can be prepared by mixing two or more types of polymer powder particles after polymerization.
The powder particles of the crystalline polyolefin according to the present invention can further contain the same or different type polyolefin wax, as long as the characteristics of the resultant powder particles are acceptable for the intended use. The polyolefin wax can be present in the state of individual particles or in the state where the polyolefin wax is adhered to the surface or the interior portion of the crystalline polyolefin powder particles. The polyolefin waxes used in the present invention are those having a viscosity-average molecular weight of from 500 to 5,000. The incorporation of 0.1 to 10% by weight of the polyolefin wax into the powder particles facilitates the enlargement of the powder particles and the formation of the enlarged powder particles having a smooth surface.Especially when the powder particles having a viscosity-average molecular weight of 150,000 or more are to be enlarged, the use of the polyolefin wax is effective.
Since the above mentioned polymer powder particles generally have high melt viscosity, a large amount of power is required when these powder particles are pelletized or granulated by melt extruding through and extruder. Contrary to this, according to the present invention, the enlarged powder particles can be obtained at a low energy consumption by mutually welding the crystalline polyolefin powder particles under a mutual welding temperature condition of the particles, while the powder particles being subjected to the rate of the mutual travel sufficient to prevent the conglomeration of the powder particles due to the complete mixing of the molten powder particles, and, then, cooling the resultant powder particles.
The apparatus for enlarging the powder particles according to the present invention can be any apparatus capable of heating or maintaining the temperature of the powder particles and fluidizing the powder particles at a high speed. For instance, a high speed fluid mixer provided with a heating jacket and a high speed rotary blade can be desirably used in the practice of the present invention. Either the continuous type or batchwise type apparatus can be used in the present invention. The volume fraction of the powder particles occupying the empty space of the apparatus can be appropriately selected. This selection can be easily made by those skilled in the art, taking into consideration the following.
That is, in the case where the volume fraction of the powder particles is too small, the productivity is decreased. Contrary to this, in the case where the volume fraction of the powder particles is too large, the powder particles are liable to conglomerate.
The powder particles to be enlarged according to the present invention should be heated to a mutual welding temperature of the powder particles. The term "mutual welding temperature" used herein means a temperature range which is at least the melting initiation temperature of the crystalline of the polyolefin and within which the powder particles can be mutually fused with one another. From the point of view of (i) the decrease in the heat energy consumed, (ii) the prevention of the heat deterioration of the powder particles and (iii) the prevention of the formation of particles which are too large, the use of an extremely high temperature is not necessary.
Generally, from a temperature at which the surface of the powder particles is melted to a temperature of 200C higher than the melting point of the powder particles can be advantageously used in the present invention.
Such temperature can be obtained by preheating the powder particles, or heating the powder particles through a heating jacket during high speed fluidization of the powder particles, or the heat generation due to the impingement or friction of the powder particles during high speed fluidization of the powder particles, or any combination thereof.
In order to prevent the conglomeration of the powder particles due to the complete melting of the powder particles, a sufficient rate of mutual travel should be imparted to the powder particles under the mutual welding temperature conditions.
In the case where the rate of mutual travel is too low, the powder particles become massive bulk material and finally form the conglomerates thereof, and also the particle size distribution of the resultant particles becomes wide. The preferable rate of mutual travel of the powder particles is as high as possible. Especially when the polyolefin powder particles having a viscosityaverage molecular weight of 200,000 or less which have low melt viscosity are to be enlarged, the use of high speed fluid mixing as in Henschel mixer is desirable. Although the use of the high speed fluid mixing is also desirable when the polyolefin powder particles having high melt viscosity are to be enlarged, medium or low speed fluid mixing as in a ribbon blender or a cone blender can also be used.
The heated powder particles enlarged by the mutual welding of the powder particles of the crystalline polyolefin are then cooled. The powder particles are desirably cooled in such a state that the powder particles are subjected to the rate of mutual travel sufficient to prevent the further enlargement of the heated powder particles.
During or after cooling, the enlarged powder particles can be mechanically ground or crushed by using a grinder or a crusher. Thus, the enlarged powder particles having too large a particle size can be crushed and the particle size of the enlarged powder particles is desirably adjusted.
Especially when the massive large particles or agglomerates having a size of 5 mm or more are obtained under mutual welding temperature conditions, these large particles or agglomerates can be readily crushed to powder particles having a desired appropriate size, as long as the large particles are coarsely welded and are in the porous or sintered state. The cooling can be effectively carried out by air cooling. Water cooling and the subsequent cutting and drying steps which are usually adopted in the granulation or pelletization by using an extruder are not necessary in the present invention.
The average particle size (median diameter) of the enlarged powder particles as obtained above is larger than 25 meshes. Furthermore, the enlarged powder particles having an average particle size (median diameter) of from 25 to 7 meshes and having a particle size distribution of such that 90% by weight or more of the total powder particles is within the range of from 30 to 4 meshes can also be obtained.
Furthermore, in accordance with the present invention, the powder particles of the crystalline polyolefin having an average particle size of smaller than 25 meshes can be effectively obtained by enlarging the fine powder particles.
For instance, it is desirable to use powder particles having a particle size as large as possible (but not as large as 25 meshes) when the powder particles are used in the fields of powder molding such as compression molding, sinter molding and rotational molding, or powder coating. For instance, it is well-known in the art that, when powder particles having an average particle size of smaller than 100 meshes are used, the workability and the finish of the molded articles deteriorate. These problems can be solved when the powder particles, having an average particle size of 25 to 75 meshes, enlarged by the present invention are used.On the other hand, since the filtering characteristics and the gas-permeability of porous articles molded by sinter molding largely depend upon the particle size of the powder particles used, a wide range of the characteristics and the specification of desired molded articles can be covered by controlling the average particle size of the powder particles in accordance with the present invention.
The enlarged powder particles of the present invention can be classified by using an appropriate classificator to adjust the desired particle size of the enlarged powder particles. The coarse powder particles having a particle size larger than the desired size classified by a classificator can be recovered by mechanical grinding or crushing, whereas the fine powder particles having a particle size smaller than the desired size classified by a classificator can be reused in the enlargement step of the present invention.
Especially when 1 to 100 parts by weight, more preferably 1 to 50 parts by weight, of the fine powder particles classified by a classificator, or ground or crushed by a grinder or crusher is added to 100 parts by weight of the powder particles of the crystalline polyolefin prepared by suspension polymerization or gas phase polymerization, the enlargement of the powder particles is facilitated and the bulk density of the enlarged powder particles is desirably improved.
However, in the case where the addition amount of the above-mentioned fine powder particles is increased beyond the above mentioned range, the overall productivity is disadvantageously decreased. It is believed that the above mentioned effects obtained from the addition of the classified or crushed fine powder particles are due to the facts that, since the enlarged powder particles and the mechanically crushed powder particles have a large surface area and contain whisker type particles or particles having projecting portions, heat transfer is rapidly
effected and, as a result, the welding of the
powder particles is rapidly and effectively caused.
The specific embodiments of the present invention are further clearly illustrated by the accompanying photomicrographs. It is clearly understood from the comparison of Figs. 1 to 4 that the powder particles of the high-molecular weight crystalline polyolefin are difficult to cause a viscous flow at a temperature of not less than the melting point.
Fig. 1 is a phase contrast photomicrograph (magnified 30 times) of the high-density polyethylene powder particles having a viscosityaverage molecular weight of 280,000 used in
Example 1 hereinbelow at room temperature, and
Fig. 2 is a phase contrast photomicrograph (magnified 30 times) of the polyethylene powder particles of Fig. 1 after allowing it to stand for 1 5 minutes at a temperature of 1500 C. Although a portion of the powder particles appears to be transparent due to the melting thereof in Fig. 2, the original shapes of the powder particles at room temperature are substantially sustained.
Contrary to this, Fig. 3 is a phase contrast photomicrograph (magnified 30 times) of the high-density polyethylene powder particles having a viscosity-average molecular weight of 30,000 used in Comparative Example 1 hereinbelow, and Fig. 4 is a phase contrast photomicrograph (magnified 30 times) of the polyethylene powder particles of Fig. 3 after allowing it to stand for 30 seconds at a temperature of 1 500C. As is clear from Fig. 4, the powder particles are changed to spherical shapes and cause fluidization due to the melting thereof.
Fig. 5, is a scanning type electron photomicrograph (magnified 30 times) of the enlarged powder particles obtained in Example 1 hereinbelow and clearly shows the conditions that the individual fine powder particles are sintered with one another to form enlarged powder particles. Fig. 6 shows the enlarged powder particles obtained in Example 2 hereinbelow. The sintering conditions of the fine powder particles are coarse and a lot of pores are present in the interior portions of the powder particles, as is clear from Fig. 6. Fig. 7 shows the cross section of the enlarged powder particles of Fig. 6. It is clearly understood from Fig. 7 that complicated and irregular open pores are contained in the interior of the enlarged powder particles of Fig. 7.
In the practice of the enlargement of the powder particles according to the present invention, it is recommendable that the enlargement operation is carried out in, for example, a nitrogen atmosphere to prevent the heat deterioration of the polyolefin. Furthermore, various conventional additives such as antioxidants, ultraviolet absorbing agents, lubricants, antistatic agents, coloring agents, fire retardants and the like can be biended during the enlargement step so long as the desired enlargement is not impaired.
The enlarged powder particles obtained above can be directly used as molding materials suitable for use in various molding machines to form various molded articles as in the case of conventional pellets. In addition, the enlarged powder particles prepared by the present invention can also be directly used as molding materials suitable for use in various powder molding processes such as sinter molding, compression molding, rotational molding and the like.
The present invention will now be specifically illustrated by, but is by no means limited to, the
Examples set forth below.
The properties defining the powder particles of the present invention were determined according to the following methods.
Bulk Density: ASTM D 1895.
Particle Size Distribution: JIS K 0069.
Viscosity-Average Molecular Weight (Mw):
Mw was determined from the relationship set forth in Journal of Polymer Science 36, p91 (1957), x7=6.8 x 1 0-4Mw0 67 in which the intrinsic viscosity 77 of the polymer powder particle was measured in the decaline solution at a temperature of 1 35 C.
Example 1
High-density polyethylene powder particles obtained by suspension polymerization and having powder properties of an average particle size (i.e. median diameter) of 100 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 40 to 280 meshes and a bulk density of 0.37 and having a density of 0.955 and a viscosity-average molecular weight of 280,000 were used as a starting material. According to microscopic observation, 100% by weight of these polymer powder particles did not remarkably change their individual powder particle shapes even in the case where these powder particles were heated, under no load, to a temperature 200C higher than the melting point thereof (refer to Fig. 2).
1 5 kg of these powder particles was preheated to a temperature of 800C by using an air dryer and, then, charged into a 1 50 liter Henschel mixer manufactured by Mitsui Miike Seisakusho and enlarged under the following conditions.
Enlarging Conditions:
Jacket condition 1 200C steam
Revolution number of blades 1460 rpm
Type of blade P-type blade
Stirring time 7 mins.
The heated powder particles thus enlarged by mutually welding with one another were withdrawn and charged into a 1 50 liter cooling mixer and cooled with stirring under the following conditions.
Jacket condition 200C water
Revolution speed of blades 730 rpm
Type of blade Cooling blade
Stirring time 5 mins.
The enlarged powder particles thus prepared had an average particle size (median diameter) of
14 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 25 to 6 meshes and a bulk density of 0.42.
Energy required for granulating these powder particles was about one third when compared with the case where an extruder was used.
Example 2
A mixture of (i) 50% by weight of high molecular weight high-density polyethylene powder particles obtained by suspension polymerization and having powder properties of an average particle size of 80 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 40 to 280 meshes and a bulk density of 0.35 and having a density of 0.954 and a viscosity-average molecular weight of 800,000 and (ii) 50% by weight of low molecular weight polyethylene powder particles obtained by suspension polymerization and having the same properties as those of the above mentioned component (i) except that the viscosity-average molecular weight was 20,000 was used.According to microscopic observation, about half of these powder particles did not remarkably change their individual powder particle shapes even in the case where these powder particles were heated, under no load, to a temperature 200C higher than the melting point thereof.
These powder particles were enlarged in the same manner as described in Example 1 except that the stirring time was 4 minutes. The enlarged powder particles thus obtained had an average particle size of 1 6 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 25 to 8 meshes and a bulk density of 0.36.
Example 3
A mixture of (i) 60% by weight of highmolecular weight crystalline polypropylene powder particles obtained by suspension polymerization having powder properties of an average particle size of 100 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 40 to 280 meshes and a bulk density of 0.34 and having a density of 0.91 and a viscosity-average molecular weight of 700,000 and (ii) 40% by weight of low molecular weight crystalline polypropylene powder particles obtained by suspension polymerization having the same properties as those of the above mentioned component (i) except that a component having a viscosity-average molecular weight of 50,000 was used.
These powder particles were preheated to a temperature of 1 200C and, then, enlarged in a
Henschel mixer under the mixer jacket condition of 1 500C steam and a stirring time of 6 minutes in the same manner as described in Example 1.
After cooling, enlarged polypropylene powder particles were obtained.
The enlarged powder particles had an average particle size of 1 6 meshes, a particle distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 25 to 8 meshes and a bulk density of 0.36.
Example 4
2 parts by weight of polyethylene wax having a viscosity-average molecular weight of 2000 and a density of 0.953 were added to 100 parts by weight of the high-density polyethylene powder particles used in Example 2. The mixed powder particles were able to be enlarged for a stirring time of 3 minutes in the same manner as described in Example 2.
The enlarged powder particles thus obtained had an average particle size of 1 6 meshes, a particle distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 25 to 8 meshes and a bulk density of 0.40.
Example 5
After classifying powder particles having a particle size of 8 meshes or above from the enlarged powder particles obtained in Example 2, the crushed powder particles having an average particle size of 20 meshes and a particle size distribution of such that more than 90% by weight of the total powder particle had a particle size within the range of from 35 to 10 meshes were obtained by using a turbo-type crushing machine.
10 parts by weight of the crushed powder particles thus obtained was mixed with 90 parts by weight of the high density polyethylene obtained by suspension polymerization used in
Example 2. The mixed powder particles were able to be enlarged during a stirring time of 3 minutes when they were enlarged in the same manner as described in Example 2.
The enlarged powder particles thus obtained had an average particle size of 14 meshes, a
particle size distribution of such that more than
90% by weight of the total powder particles had a
particle size within the range of from 25 to 8
meshes and a bulk density of 0.40.
Example 6
After classifying powder particles having a particle size of finer than 40 meshes from the enlarged powder particles obtained in Example 2,
10 parts by weight of the powder particles thus classified was mixed with 90 parts by weight of the high density polyethylene powder particles obtained by suspension polymerization used in
Example 2. The powder particle mixture was able to be enlarged during a stirring time of 3 minutes when the mixture was enlarged in the same
manner as described in Example 2.
The enlarged powder particles thus obtained had an average particle size of 1 6 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 25 to 8 meshes and a bulk density of 0.41.
Example 7
2 kg of medium-density polyethylene powder particles obtained by suspension polymerization having powder properties of an average particle size of 60 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 40 to 200 meshes and a bulk density of 0.37 and having a density of 0.938 and a viscosity-average molecular weight of 80,000 was charged into a 20 liter Henschel mixer manufactured by Mitsui Miike Seisakusho and was enlarged under the following conditions.
Enlarging Conditions*1:
Jacket temperature 900C
Revolution number
of blades 2300 rpm
Type of blades P-type blade
Stirring time 14 mins.
* 1: Although the jacket temperature was less than the melting point of the powder particles, the temperature of the surface of the powder particles became higher than the melting point due to the occurrence of the frictional heat and the like.
The heated powder particles thus enlarged by the mutual welding were withdrawn and charged into a 20 liter cooling mixer and cooled with stirring under the following conditions.
Jacket condition 200C water
Revolution speed
of blades 2300 rpm
Type of blades Cooling blade
Stirring time 5 mins.
The enlarged powder particles thus obtained had an average particle size of 28 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 8 to 100 meshes and a bulk density of 0.39.
Example 8
High-density polyethylene powder particles prepared by two-step continuous suspension polymerization comprising (i) 50% by weight of low molecular weight polyethylene having a viscosity-average molecular weight of 15,0C0 obtained in the first step polymerization and (ii) 50% by weight of high molecular weight polyethylene having a viscosity-average molecular weight of 800,000 obtained in the second step polymerization were used. These powder particles had powder properties of an average particle size of 100 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 50 to 280 meshes and a bulk density of 0.35 and had a density of 0.955.According to microscopic observation, almost all of these polymer powder particles did
not remarkably change their polymer powder particle shape even in the case where these
polymer powder particles were heated, under no
load, to a temperature 200C higher than the
melting point thereof.
These powder particles were enlarged during a stirring time of 3 minutes and 40 seconds, followed by cooling in a cooling mixer, in the same manner as described in Example 1. Thus, the enlarged powder particles were obtained.
The enlarged powder particles thus obtained had an average particle size of 1 6 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 25 to 8 meshes and a bulk density of 0.39.
Example 9
High density polyethylene powder particles obtained by gas phase polymerization and having powder properties of an average particle size of 60 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of 25 to 1 50 meshes and a bulk density of 0.36 and having a density of 0.945 and a viscosity-average molecular weight of 180,000 were used.
These powder particles were enlarged during a stirring time of 5 minutes and 30 seconds, followed by cooling in a cooling mixer, in the same manner as described in Example 1. Thus, the enlarged powder particles were obtained.
The enlarged powder particles thus obtained had an average particle size of 10 meshes, a particle distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 25 to 6 meshes and a bulk density of 0.40.
Example 10
The polyethylene powder particles used in
Example 1 were enlarged under the same conditions as described in Example 1 except that the stirring time was 5 minutes. After cooling, the enlarged powder particles were obtained.
The powder particles thus enlarged had an average particle size of 35 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 80 to 20 meshes and a bulk density of 0.39.
Cylindrical molded filters having a wall thickness of 3.2 mm, an outer diameter of 36 mm and a length of 1 78 mm were sinter molded from the enlarged powder particles obtained above.
The cylindrical filters thus obtained had a filtering characteristics of 120 microns.
Comparative Example 1
High-density polyethylene powder particles obtained by suspension polymerization and having powder properties of an average particle size of 70 meshes, a particle size distribution of such that more than 90% by weight of the total powder particles had a particle size within the range of from 40 to 280 meshes and a bulk density of 0.35 and having a density of 0.953 and a viscosity-average molecular weight of 30,000 was used. According to microscopic observation, the particle shapes of 100% by weight of the powder particles first changed to spherical shapes, and then fluidized to form mutually welded massive particles (see Fig. 4).
Although these particles were enlarged in the manner as described in Example 7, the particles became conglomerates during a stirring time of less than 4 minutes and enlarged particles were not obtained.
Claims (12)
1. Enlarged power particles of crystalline polyolefin obtained from the welding of crystalline polyolefin powder particles with one another, said crystalline polyolefin powder particles having an average particle size of smaller than 30 mesh (Tyler) and a viscosity-average molecular weight of at least 50,000 and being prepared by onestep or multi-step suspension polymerization or gas phase polymerization and the particle size of said enlarged powder particles being larger than that of the starting crystalline polyolefin powder particles.
2. Enlarged powder particles as claimed in claim 1, wherein the average particle size of the enlarged powder particles is larger than 25 mesh (Tyler).
3. Enlarged powder particles as claimed in claim 1, wherein the enlarged powder particles are porous particles having irregular open-pores therein.
4. Enlarged powder particles as claimed in claim 1,2 or 3, wherein the viscosity-average molecular weight of the crystalline polyolefin powder is within the range of from 150,000 to 1,000,000.
5. Enlarged powder particles as claimed in claim 1, 2 or 3, wherein said crystalline polyolefin comprises (i) 40 to 90% by weight of a high molecular weight component of which individual particles do not cause viscous flow deformation upon melting even when they are heated, under no load, to a temperature of at least the melting point thereof but less than a temperature 200C higher than the melting point thereof and (ii) 10 to 60% by weight of a low molecular weight component of which individual particles cause viscous flow deformation upon melting under the above mentioned conditions, both the components being present in such a state that each particle is individually present or that plural particles are adhered to each other and a total viscosityaverage molecular weight being at least
6.Enlarged powder particles as claimed in claim 5, wherein the viscosity-average molecular weight of the high molecular weight component is within the range of from 200,000 to 1,000,000 and that of the low molecular weight component is within the range of from 5,000 to 50,000.
7. Enlarged powder particles as claimed in claim 1,2 or 3, wherein said crystalline polyolefin powder contains from 0.1 to 10% by weight of polyolefin wax having a viscosity-average molecular weight of from 500 to 5,000 therein as the low molecular weight component in such a state that each particle of the polyolefin wax is individually present or that the particles of the polyolefin wax are adhered to the crystalline polyolefin powder particles.
8. Enlarged powder particles of crystalline polyolefin obtained from the welding of the crystalline polyolefin powder particles with each other said crystalline polyolefin powder particles comprising (i) 100 parts by weight of crystalline polyolefin powder having a viscosity-average molecular weight of at least 50,000 and an average particle size of less than 30 mesh (Tyler) and being prepared by one-step or multi-step suspension polymerization or gas phase polymerization and (ii) 1 to 100 parts by weight of mechanically crushed polyolefin powder particles having an average particle size of smaller than 30 meshes, the particle size of said enlarged powder particles being larger than those of the starting crystalline polyolefin powder particles.
9. Enlarged powder particles obtained from the welding of (i) 100 parts by weight of crystalline polyolefin powder particles having an average particle size of smaller than 30 mesh(Tylerl and a viscosity-average molecular weight of at least 50,000 and being prepared by one-step or multistep suspension polymerization or gas phase polymerization and 1 to 30 parts by weight of the enlarged powder particles as set forth in claim 1 having a particle size of less than 30 mesh (Tyler), the particle size of said enlarged powder particles thus obtained being larger than those of the starting powder particles.
10. A method of enlarging powder particles of crystalline polyolefin having an average particle size of smaller than 30 mesh (Tyler) and a viscosity-average molecular weight of at least 50,000 and being prepared by one-step or multistep suspension polymerization or gas phase polymerization comprising the steps of:
(i) treating said crystalline olefin powder particles under a mutual welding temperature condition to enlarge the crystalline olefin particles, while the powder particles are subjected to a rate of mutual travel sufficient to prevent the conglomeration of the powder particles due to the complete mixing of the molten powder particles and, then,
(ii) cooling the resultant crystalline olefin powder particles.
11. A method as claimed in claim 10, wherein the mutually welded enlarged powder particles are mechanically ground or crushed during or after cooling.
12. A method as claimed in claim 10, substantially as described in any one of the
Examples.
1 3. Enlarged powder particles as claimed in claim 1, substantially as described in any one of the Examples.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6226280A JPS56159116A (en) | 1980-05-13 | 1980-05-13 | Method of coarse granulation of crystalline polyolefin powder and coarse granules |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2077272A true GB2077272A (en) | 1981-12-16 |
| GB2077272B GB2077272B (en) | 1983-11-23 |
Family
ID=13195051
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8112731A Expired GB2077272B (en) | 1980-05-13 | 1981-04-24 | Enlarged powder particles of crystalline polyolefin and method of producing the same |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS56159116A (en) |
| CA (1) | CA1176810A (en) |
| DE (1) | DE3118499C2 (en) |
| GB (1) | GB2077272B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2011140053A1 (en) * | 2010-05-03 | 2011-11-10 | Ticona Llc | Polyethylene powders and porous articles produced therefrom |
| US9027566B2 (en) | 2010-10-15 | 2015-05-12 | Celanese Acetate Llc | Apparatuses, systems, and associated methods for forming porous masses for smoke filter |
| US9386803B2 (en) | 2010-01-06 | 2016-07-12 | Celanese Acetate Llc | Tobacco smoke filter for smoking device with porous mass of active particulate |
| US20190055385A1 (en) * | 2017-08-17 | 2019-02-21 | Celanese Sales Germany Gmbh | Polymer Composition For Producing Gel Extruded Articles and Polymer Articles Made Therefrom |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6262710A (en) * | 1985-09-13 | 1987-03-19 | Achilles Corp | Manufacture of synthetic resin granule |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1426438A (en) * | 1964-01-18 | 1966-01-28 | Hoechst Ag | Process for conditioning olefin polymers in powder form for the preparation of shaped articles |
| US3527845A (en) * | 1967-06-28 | 1970-09-08 | Avisun Corp | Method of reducing fines in alphaolefin polymer powder |
-
1980
- 1980-05-13 JP JP6226280A patent/JPS56159116A/en active Pending
-
1981
- 1981-04-16 CA CA000375629A patent/CA1176810A/en not_active Expired
- 1981-04-24 GB GB8112731A patent/GB2077272B/en not_active Expired
- 1981-05-09 DE DE19813118499 patent/DE3118499C2/en not_active Expired
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9386803B2 (en) | 2010-01-06 | 2016-07-12 | Celanese Acetate Llc | Tobacco smoke filter for smoking device with porous mass of active particulate |
| WO2011140053A1 (en) * | 2010-05-03 | 2011-11-10 | Ticona Llc | Polyethylene powders and porous articles produced therefrom |
| CN102869688A (en) * | 2010-05-03 | 2013-01-09 | 提克纳有限责任公司 | Polyethylene powders and porous articles produced therefrom |
| CN102869688B (en) * | 2010-05-03 | 2015-03-25 | 提克纳有限责任公司 | Polyethylene powders and porous articles produced therefrom |
| US9179708B2 (en) | 2010-10-15 | 2015-11-10 | Celanese Acetate Llc | Apparatuses, systems, and associated methods for forming porous masses for smoke filter |
| US9149069B2 (en) | 2010-10-15 | 2015-10-06 | Celanese Acetate Llc | Apparatuses, systems, and associated methods for forming porous masses for smoke filter |
| US9138017B2 (en) | 2010-10-15 | 2015-09-22 | Celanese Acetate Llc | Apparatuses, systems, and associated methods for forming porous masses for smoke filter |
| US9027566B2 (en) | 2010-10-15 | 2015-05-12 | Celanese Acetate Llc | Apparatuses, systems, and associated methods for forming porous masses for smoke filter |
| US20190055385A1 (en) * | 2017-08-17 | 2019-02-21 | Celanese Sales Germany Gmbh | Polymer Composition For Producing Gel Extruded Articles and Polymer Articles Made Therefrom |
| WO2019035083A3 (en) * | 2017-08-17 | 2019-03-28 | Celanese Sales Germany Gmbh | Polymer composition for producing gel extruded articles and polymer articles made therefrom |
| US10875991B2 (en) | 2017-08-17 | 2020-12-29 | Celanese Sales Germany Gmbh | Polymer composition for producing gel extruded articles and polymer articles made therefrom |
| US20210108056A1 (en) * | 2017-08-17 | 2021-04-15 | Celanese Sales Germany Gmbh | Polymer compositon for producing gel extruded articles and polymer articles made therefrom |
| US11780995B2 (en) | 2017-08-17 | 2023-10-10 | Celanese Sales Germany Gmbh | Polymer composition for producing gel extruded articles and polymer articles made therefrom |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3118499C2 (en) | 1984-07-26 |
| DE3118499A1 (en) | 1982-03-25 |
| GB2077272B (en) | 1983-11-23 |
| CA1176810A (en) | 1984-10-30 |
| JPS56159116A (en) | 1981-12-08 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19990424 |