KR20010013416A - Process for preparing porous polyolefin particles - Google Patents

Abstract

The invention relates to a process for preparing porous polyolefin particles. The process according to the invention is characterized in that it comprises the following steps: 1) dissolving at least one crystallizable polyolefin in a solvent, in the absence of a nucleating agent; 2) dispersing the polyolefin solution obtained in a non-solvent in the presence of a surfactant, at a temperature that is higher than the crystallization temperature of the polyolefin in the polyolefin solution; 3) cooling the multi-phase system obtained with stirring, at a rate of between 0.05 and 10 °C/min to a temperature that lies below the crystallization temperature of the polymer in the polymer solution, so that firm polyolefin particles are formed; 4) separating the polyolefin particles; 5) drying the polyolefin particles. The invention also relates to a porous polyolefin particle with a high effective loadability and a narrow particle size distribution.

Description

Process for producing porous polyolefin particles {PROCESS FOR PREPARING POROUS POLYOLEFIN PARTICLES}

The present invention relates to a method for producing porous polyolefin particles.

The method is known from EP 0 370 260 A1. However, a disadvantage of this method is that it requires a number of different liquids to be able to produce porous polymer particles. First, a mixture of (at least) two liquids is used to dissolve the polymer, which requires high temperatures. This results in a homogeneous polymer solution. Thereafter, a third liquid (hot inert dispersant) is added to the obtained polymer solution. This results in a two-phase system. The two phase system is vigorously stirred to form droplets of the polymer solution. Thereafter, a fourth cold inert liquid is added. Next, the droplets are collected and finally the extraction step takes place. At least the other fifth liquid requires extraction. In some cases, the extraction should be carried out by washing with another (at least sixth) liquid as specified in Example 11. Because the known processes require a lot of liquid, on industrial scale they produce a lot of waste streams that have to be purified. From an environmental and process technical point of view, the method is unsatisfactory and therefore a better method is needed.

It is an object of the present invention to provide a process for producing porous polyolefin particles in which the above disadvantages are eliminated in whole or in part. The above object is a method;

1) preparing a polyolefin solution by dissolving at least one crystallizable polyolefin in a solvent in the absence of nucleation,

2) disperse the obtained polyolefin solution in the non-solvent in the presence of a surfactant at a temperature higher than the temperature at which the polyolefin starts to crystallize in the polyolefin solution to form a multiphase system,

3) The obtained polyphase system is cooled to a temperature below the crystallization temperature of the polymer in the polymer solution while stirring at a rate of 0.05 to 10 ° C./min to form solid polyolefin particles,

4) Isolate the polyolefin particles,

5) drying the polyolefin particles.

This gives the direct result that fewer (other) liquids are needed in the process according to the invention, so that the waste stream to be purified is less and is easier to carry out than the process described in EP 0 370 260 A1. In addition, according to the method of the present invention, there is less risk of producing porous polyolefin particles containing the remainder of the remaining one or more liquids. And, the advantage of the process according to the invention is that the dimensions of the porous polyolefin particles can be better controlled. Another advantage is that the dimensions of the prepared porous polyolefin particles extend smaller than before.

A method for producing polymer particles with adjustable dimensions is known from EP 0 644 230 A1, but no indication is given how the porous polymer particles are produced.

Porous polyolefin particles obtained using the process according to the invention can be prepared using several polyolefins as starting materials. Homopolymers are suitable, but copolymers are also suitable. The term 'copolymer' is understood herein to mean a polymer combined with two or more different monomers. The monomers used are α-olefins (eg ethylene, propylene or other α-olefins having 4-12 carbon atoms). The monomer may also have polar properties such as, for example, vinyl acetate. An advantage of vinyl acetate as comonomer is that the porous particles made therefrom can better absorb polar materials. The concentration of polar monomers, such as vinyl acetate, in EVA (ethylene-vinyl acetate copolymer) suitable for preparing porous particles is at most 25 wt.% Relative to the total amount of polymer. In the description of the invention, mixtures of different polyolefins can be used.

Polyolefins that can be used meet already specified product conditions, such as freshly prepared polyolefins and polyolefins obtained after the improvement of the materials used, for example, polyolefins, contaminated polyolefins and substandard products collected as waste products and manufacturing wastes in regeneration schemes. It is not polyolefin.

It is important that the polyolefin is soluble at a certain temperature and the polyolefin can crystallize to form a porous porous structure in the cooling stage. However, the polyolefin does not need to be able to crystallize completely (100%).

Suitable polyolefins for preparing the porous polyolefin particles according to the invention are, for example, polyethylene, polypropylene, polybutylene, poly (4-methyl-1-pentene), polycyclohexylethylene. Preferably, polyethylene and / or polypropylene are used, more preferably polyethylene. The type of polyethylene used in the process of the invention is not critical. Polyethylene is produced by methods known per se, including solutions, slurries, gas phase and high pressure processes. The density of polyethylene varies from 880 to 965 kg / m 3. For example, ultra high molecular weight polyethylene (UHMWPE), high density polyethylene (HDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), ultra low density polyethylene (VLDPE) and ultra low density polyethylene (ULDPE) can be used. Preference is given to using LDPE or LLDPE.

'LLDPE' is actually understood to be a linear homopolymer or a copolymer of ethylene with one or more α-olefins having 3-12 carbon atoms and optionally one or more unbonded dienes. In particular, suitable α-olefins are propylene, 1-butene, 1-hexene, 4-methylpentene-1 and 1-octene. Suitable dienes are, for example, 1,7-octadiene and 1,9-decadiene. LLDPE mainly has short side chains of 1 to 10 carbon atoms and considerably shorter side chains than LDPE.

LDPE is a highly branched polyethylene. As LDPE, polyethylene produced by a conventional method in a high pressure process by one or more radical initiators can be used. The high pressure process can take place in an autoclave or tubular reactor. LDPE has a density of 935 kg / m 3 or less. Mixtures with EVA are also very suitable.

If polypropylene is used, both co-arranged and alternating polypropylene can be used. Copolymers of polypropylene with one or more other α-olefins such as ethylene and butylene are also possible.

In preparing porous polyoletin particles, one polyolefin or polyolefin mixture can be used. If one polyolefin is used, the polyolefin preferably has a DSC crystallization peak with a width of at least 5 ° C. Preferably, the width of the crystallization peak is at least 10 ° C, in particular at least 15 ° C. The width is the peak width measured at half the height of the crystallization peak in the DSC curve.

If a mixture of polyolefins is used, preferably the polyolefins should have different crystallization peak temperatures. Preferably, the difference in crystallization temperature is 5 ° C. or higher. The amount of polyolefin having a high crystallization temperature is at least 0.1 wt.%, Preferably 1 to 5 wt.%, For the polyolefin having a low crystallization temperature.

Preferably, the polyolefin or mixture of polyolefins exhibits rapid crystallization behavior when cooling the polyolefin solution. Crystallization behavior is considered rapid if the maximum crystallization peak at the onset of crystallization is within 5 ° C. in a DSC experiment as described below.

Crystallization temperatures and thermal behavior of polyolefins can be measured by differential scanning calorimetry (DSC) techniques.

In DCS measurements, a substance or a mixture of substances is heated or cooled under controlled conditions in a controlled atmosphere, during which the temperature difference between the substance and the reference substance is measured continuously (as a result of energy changes in the substance). do. A transition (eg, melting or crystallization) is represented by a mixture or material that absorbs or releases energy, thereby obtaining a corresponding endothermic or exothermic peak in the DSC curve. As noted above, the curve may comprise one or more peaks.

DSC measurements can be performed both on polyolefins and on polyolefin solutions in solvents.

For DSC measurements in the description of the invention, the polyolefin or polyolefin solution is heated to 200 ° C. at a rate of 5 ° C./min (first heating curve); It is then cooled to -50 ° C at a rate of 5 ° C / min (cooling curve). The second heating curve is then recorded at a heating rate of 5 ° C./minute. Melting and crystallization behavior of polyolefins is characterized based on the latter two curves. Crystallization / melting of the solvent can also be observed during DSC measurements, which should not be confused with the DSC behavior of polyolefins.

The temperature at which the (DSC) crystallization curve (cooling curve) deviates by 1% from the baseline is understood as the temperature at which crystallization begins, where% is the ratio to the height of the maximum peak. The width of the crystallization peak means the width at half the height at the temperature at which the cooling curve shows the maximum.

The method of the invention is carried out in the absence of nucleation. The nucleation herein is a component that functions to stimulate the formation of polyolefin crystals while cooling the polyolefin solution and is not soluble in the polyolefin solution during the course of the present invention.

The polymer particles are dried at the temperature at which a substantial part of the crystallization of the polyolefin has already occurred. Preferably, the drying temperature is below the temperature at which 50% of the total heat of the polyolefin is released upon crystallization in the DSC thermogram. The crystallization temperature is shown below the cooling curve in the DSC thermal analysis. Preferably, the drying temperature is lower than the temperature at which 75% of the total heat is released during crystallization. This ensures that the structure of the porous polyolefin remains most preferably completely intact during the drying process.

The method according to the invention is carried out as follows. The polyolefin or polyolefin mixture is first dissolved in a solvent. Several organic liquids can be used as the solvent. The type of solvent used will depend to a high degree on the solvent's ability to dissolve the polyolefin. Suitable organic solvents for use in the process of the invention are, for example, n-alkanes, i-alkanes, cycloalkanes, polycyclic compounds having two or more ring structures, alkenes, cycloalkenes, substituted or unsubstituted Is not selected from the series of aromatic compounds, chlorinated hydrocarbons, decalin, tetralin or paraffin oil. The compounds are all substituted and unsubstituted. The substituents are all composed of C and H atoms alone, and are composed of C, H and / or heteroatoms. It is preferable that a substituent has 3-100 carbon atoms. Preference is given to using n-alkanes, i-alkanes, cycloalkanes, substituted or unsubstituted aromatic compounds and decalin or mixtures thereof. When polyethylene is used as the polyolefin, in particular cycloalkanes or alkanes, more preferably cyclohexane, boiling point spirit, hexane, heptane or octane or mixtures thereof are used. Usually, polar solvents are used for polar olefins.

The polyolefin can be selectively dissolved in the solvent while heating at the same time. If necessary, dissolution can be accelerated by dynamic mixing or static mixing. In some cases, it is advantageous to work at high temperatures depending on the type of solvent selected, thereby allowing it to dissolve at temperatures above the atmospheric boiling point of the solvent. Those skilled in the art will readily be able to determine whether working at high temperatures would be advantageous. The temperature at which the polyolefin is dissolved is not critical as long as the polyolefin is dissolved. Those skilled in the art will also readily appreciate this. Usually, the dissolution temperature will be 40 to 200 ° C. It is preferable that a melting temperature is 70-180 degreeC. Under these conditions, the polyolefin is effectively dissolved in the solvent.

Usually, an amount of solvent is used so that the polyolefin solution prepared contains about 0.1 to 50 wt.%, Preferably 15 to 35 wt.% Polyolefin. This obviates the elimination of evaporation of part of the solvent. At concentrations> 50 wt.%, It becomes difficult to stir the polyolefin solution, and at low concentrations the process is less attractive economically.

The resulting polyolefin solution and non-solvent are optionally dispersed with one another in other forms of dynamic or static mixing or stirring. If the nonsolvent is a continuous phase in the obtained dispersion, the order in which the nonsolvent and the polyolefin solution are added to each other for dispersion is not critical. A non-solvent is a compound in which a polyolefin does not dissolve. For the term 'cost system', see 'Polymer Handbook', J. Bandrup and E.H. Immergut, eds., John Wiley and Sons, 3rd Ed. (1989), pp. See the table specified in / 379, etc. If the non-payment remains in a continuous phase in the obtained dispersion, the amount of non-payment used is not critical. The polyolefin solution: non-volume volume ratio varies from 10: 1 to 1:10, preferably from 5: 1 to 1: 5. Most preferably, the ratio is 1: 1 to 1: 3.

The non-solvent is a polar compound or a nonpolar compound depending on the polarity of the polyolefin. Polar nonsolvents are very suitable for use with polyolefins that dissolve in nonpolar solvents. Suitable polar compounds for use as non-solvents are, for example, compounds or water selected from the group of organic or inorganic acids, ketones or alcohols. It is preferred to use water, acetone, methanol or ethanol, more preferably water. Mixtures of these compounds are also suitable.

While the polyolefin solution is dispersed in the nonconducting agent, a multiphase system is formed and a 'polyphase system' is understood as a system consisting of at least two phases, one of which is a polyolefin-containing phase containing polyolefin. While the polyolefin solution and the nonsolvent are dispersed, the temperature of the polyolefin solution and the nonsolvent should be above the temperature at which the polyolefin starts to crystallize in the polyolefin solution. The temperature is preferably at least 15 ° C. higher than the temperature at which crystallization starts.

In order to control the dimensions of the dispersion and the basic size of the resulting porous polyolefin particles, it is necessary to add a surfactant to the non-paying agent. The higher the concentration of the surfactant, the smaller the particles, and the lower the concentration of the surfactant, the larger the particles. The surfactant concentration is preferably 10 ppm to 5 wt.%, More preferably 100 ppm to 1 wt.%. If the concentration of the surfactant is too low, the droplets in the polyolefin solution are too large, showing a less tendency to aggregate. If the concentration of the surfactant is too high, very small particles are formed. By using the method of the present invention, porous polyolefin particles having dimensions of 0.01 to about 12 mm can be obtained. Those skilled in the art will readily be able to determine the most preferred concentration by experiment.

Surfactants are anionic, cationic, nonionic or amphoteric tensides. Suitable surfactants include alkanesulfonates, alkylbenzene sulfonates, fatty acid alcohol sulfonates, alkylammonium compounds, betaine-type tensides, alkyl polyglycol ethers, ethoxylated fatty acid amines, tweens. , Span And alkyl phenol ethoxylate groups.

If foam is formed due to the presence of one or more surfactants, foam inhibitors and / or defoamers may be added. Combinations of antifoams and / or antifoams are also possible. The antifoam and / or antifoam may be added to other process steps, but is preferably added before the dispersing step.

In the process according to the invention, part of the solvent may be selectively evaporated, for example during or after step 2, from the formed multiphase system. Evaporation may or may not be necessary depending on the solvent and polyolefin and initial polyolefin concentrations used as starting materials. The amount of solvent evaporated depends on the concentration of the polyolefin solution. The lower the concentration, the greater the amount that can be evaporated.

Solvents, non-solvents and polyolefins (mixtures) can also be combined in a single step. The mixture is then stirred with selective heating until the polyolefin is dissolved and the polyolefin solution is dispersed in the non-solvent. The polyphase system obtained is then cooled.

The cooling (step 3) of the multiphase system in the process according to the invention takes place at a rate of 0.05 to 10 ° C./min, preferably 0.1 to 5 ° C./min and in particular 0.2 to 2 ° C./min. The cooling continues until at least 50% of the total heat is released upon crystallization of the polyolefin in the original polyolefin solution. The temperature corresponding to this point can be measured by DSC technique, as mentioned above.

If the temperature is very high, the polyolefin particles are so soft that they cannot be effectively separated. If this happens, stronger cooling will be required. If cyclohexane and / or n-heptane are used as the solvent for polyethylene as the polyolefin, the cooling is preferably continued below 40 ° C. When polypropylene is added as a polyolefin, it is preferable that cooling continues to 70 degrees C or less.

Dispersion must continue while cooling the multiphase system, which can be by static mixing or dynamic mixing or by an agitator. The particle size can also be adjusted according to the type and speed of the stirrer. The greater the amount of energy supplied or the more vigorous the agitation (with the same kind of stirrer), the smaller the porous polyolefin particles will be. And vice versa, the smaller the amount of energy supplied or the slower the stirring, the larger the particles will be.

Next, the polyolefin-containing particles are separated from the multiphase system (step 4). Such separation may occur in a manner known to those skilled in the art. Suitable techniques are, for example, vacuum filtration, centrifugation and / or filtration pressing. Preference is given to using filtration under the influence of gravity.

In step 5, the separated polyolefin particles containing the solvent and optionally the non-solvent are dried. Drying takes place to the desired degree of solvent and cost elimination. The implementation of the drying process largely determines whether the obtained polyolefin particles will retain their porosity. The drying process for obtaining the porous polyolefin particles may be combined with each other or carried out in various ways as described above. Drying can take place, for example, under reduced pressure, and polyolefin-containing particles can be removed with gas or vapor (e.g., 'Microwave Processing and Engineering', RV Decareau and RA Peterson, ed.Ellis Horwood Ltd and VCH Polyolefin-containing particles) may be dielectrically dried by microwave or RF (high frequency) drying as described in GmbH, 1986 or 'Industrial Microwave Heating', ACMetaxas and RJ Meredith, Peter Peregrinus Ltd., 1983.

Suitable gases for use during the stripping process and optionally drying under reduced pressure are, for example, air, nitrogen, helium, carbon dioxide and methane. Nitrogen is preferably used as stripping gas.

In addition, drying under reduced pressure preferably occurs under conditions such that the partial pressure of the solvent in the vapor phase is at most 50%, more preferably at most 20%, of the normal vapor pressure of the solvent at the drying temperature.

The initial temperature during drying of the polyolefin particles is preferably below the temperature at which 75% of the total heat is released during crystallization. The temperature can be measured by DSC. The drying temperature is higher as the amount of solvent decreases and as a result of an increase in the concentration of polyolefins. In particular, the higher drying temperatures effectively implemented are necessary to remove the nonconductor. When polyethylene is used as the polyolefin, drying is preferably carried out at a temperature of 30 ° C. or lower initially; As for the said temperature, 20 degrees C or less is preferable.

Regardless of the type of drying method chosen, drying preferably takes place under conditions that prevent the decomposition of the particulate structure as much as possible (eg, by capillary and mechanical forces). Degradation of the particle structure will increase the particle size distribution. The particle size distribution will be quantified by the degree of dispersion (DOD) below. One skilled in the art will readily be able to determine by one or more experiments whether the decomposition of the particle structure occurs.

In a preferred embodiment according to the invention, certain nonionic tensides are used as surfactants. Typical examples of certain nonionic tensides are tensides from the group consisting of alkyl polyglycol ethers, ethoxylated fatty acid amines or alkyl phenol ethoxylates. Most preferably, alkyl polyglycol ethers or ethoxylated fatty acid amines are used. The use of such nonionic tensides in the production of porous polyolefin particles will yield particles with very small DOD.

The advantage of using such specific nonionic tensides is not limited to the processes carried out in the absence of nucleation. Comparable advantages can be obtained when further nucleation is present in a similar method for producing porous polyolefin particles.

The particle size distribution is quantified by the degree of dispersion (DOD) as measured according to DIN 66 165. The advantage of porous polyolefin particles with small DOD is that their flow characteristics are greatly improved, and the prepared porous polyolefin particles can be introduced into a processing machine such as an extruder in a very quick and renewable manner. Particles obtained by the method in which certain nonionic tensides were added according to the invention have a DOD of <0.4. Particles with such small DODs are not known yet. Accordingly, the present invention also relates to the porous polyolefin particles.

Porous polyolefin particles according to the present invention are:

A) 5-85% porosity

B) Effective loadability of at least 95% (E _1A ),

Where E _1A is the effective loading rate of the polyolefin particles with the absorbent, m _A is the absorbent weight of the absorbent, ρ _A is the density of the absorbent, m _PO is the weight of the porous polyolefin particles before absorbing the absorbent, ρ _PO Is the density of the polyolefin)

C) absorption time of at least 10 minutes (t _a )

D) has a DOD of 0.4 or less;

The porous polyolefin particles have open pore structures and narrow particle size distributions that are connectable. The particles have a high effective load rate, short absorption time, are suitable for use as a concentrate, and exhibit good flow characteristics and dosing characteristics.

Suitable absorbents for measuring effective load rates are ethoxylated amines 163.

The porosity (ε) of the particles is measured by mercury (Hg) porosimetry according to ASTM-Standard D4284-83 using Autopore II 9220 from Micrometrics (USA). Porosity is determined by measuring the volume of Hg applied to the pores at various pressures. The measurement starts at a pressure of 3 kPa. At this low pressure, the open spaces between the polyolefin particles are filled with Hg in the inter. Next, the pressure is continuously increased to about 400 MPa or less to inject Hg into the particles of the polyolefin intra. At high pressures, compression of the polymeric material occurs. The difference between the volume of Hg in the expansion system before and after pressurization is a measure for the porosity of the polyolefin. The porosity is calculated by dividing the input-Hg-volume measured at the pressure at which 85% of the pores are filled by the total volume of porous particles minus the input-Hg-volume measured at the pressure at 15% of the pores. The total volume of the porous particles is calculated by summing the weight of the polymer sample divided by its density and the injected Hg-volume as specified above. Particle porosity varies from 5 to 85%. The porosity is preferably at least 25%, more preferably at least 35%. If the porosity is high, many applications for the porous polyolefin particles are possible. The pore diameter varies from 0.01 to 100 μm.

To determine the effective loading rate, a quantity of porous particles is injected into the beaker with stirring at room temperature. Certain amounts of absorbent, such as atmers 163 is added with stirring until the porous particles no longer absorb the absorbent. This is an atmer Film of liquid and / or droplets is formed on the wall of the beaker and does not disappear after 5 minutes. The porous polyolefin particles are then considered saturated with absorbents. By reweighing the porous particles, the amount of absorbent absorbed can be measured. In the porous polyolefin particles according to the invention, E _1A is> 95%, preferably> 99%.

The main advantage of the porous polyolefin particles according to the present invention is that the particles can absorb large amounts of absorbent, and in addition the absorption process also proceeds quickly. The absorption time of the porous polyolefin particles according to the present invention is at most 10 minutes. Absorption time (t _a ) is DOW Corning 200 with a viscosity of 1 cSt and a density of 820 kg / m 3 at R _t in a beaker. It is measured by filling the latex. Porous polyolefin particles are located on the liquid. Absorption time is the amount of time the particles need to settle to the bottom of the beaker. All of this takes place at room temperature.

DOD is measured using polyolefin that is not sieved by experiments to determine particle size. Particle size is measured according to standard DIN 66 165.

DOD is defined as follows:

DOD = (d84-d16) / 2d50

(In the above, dxx represents the mesh size of the sieve where xx wt% of the porous polyolefin particles falls through the sieve.)

High DOD shows a wide particle size distribution. Small DOD shows a narrow particle size distribution, and the flow characteristics, input characteristics and mixing characteristics of the porous polyolefin particles are good.

Porous polyolefin particles of the present invention have a DOD of <0.4. Preferably, the DOD is <0.2. More preferably, the DOD is <0.15.

The size (d _p ) of the porous polyolefin particles according to the invention usually varies from 0.5 to 12 mm. Particles up to 0.5 mm and over 12 mm are also possible, but the input and flow properties are less good.

By the above, some electron microscope (SEM) photographs of porous polyolefin particles obtained using the method according to the invention are shown in FIGS. 1-4. FIG. 5 shows porous polyolefin particles with a narrow DOD, while FIG. 6 shows polyolefin particles with a wide DOD.

Porous polyolefin particles produced by the process according to the invention are suitable as carriers for other uses, for example thickeners, absorbents or substances released in a slow and / or controlled manner.

Additives For good dispersion of auxiliary materials, adjuncts, reagents, products and production control agents, for example in plastics, it is advantageous and necessary to add additives to the plastic in the form of concentrates of additives in the polymerizable matrix. Concentrates are often used in plastics, for example as so-called masterbatches. In order to economically use the additive, it is advantageous that the additive in the polymerizable matrix of the masterbatch has the highest possible concentration. However, it is often shown that especially in the case of liquid additives, high concentrations of additives in the polymer matrix cannot be well dispersed. Porous polyolefin particles are particularly suitable for absorbing one or more high concentrations of additives. In the case of liquid additives, the additives can be absorbed directly. If the additive is in solid form, it may be melted, dissolved or dispersed in a suitable liquid before contacting the porous polyolefin particles. Absorption of the additive in the porous polyolefin particles can be carried out according to known techniques. A suitable technique is for example to add an additive to the porous polyolefin particles in a powder mixer.

Concentrates are often mixed with other polymers, such as polyolefins, in an extruder to evenly distribute the additives within the polymer. Porous polyolefin particles (prepared according to the process of the invention) are very suitable for mixing with other polymers, for example polyolefins, in mixing equipment such as extruders. This is because the porous particles have a balanced mechanical stability. In a simple powder mixer, the structure of the porous particles will remain almost entirely complete so that little or no dust is formed during the formation of the concentrate. When the concentrate is mixed with the polymer in the extruder, the porous concentrate is ground under the influence of the prevailing overall pressure in the solid conveying zone of the extruder to ensure good dispersion of the concentrate on the polymer before the polymer melts. Thereafter, there is no need to charge much when mixing the polymer melt. Therefore, a simple extruder such as a single screw extruder can be used, or it can be carried out with high efficiency since few pressure-consuming mixing elements are required in the extruder for good mixing.

In other uses of the porous polyolefin particles according to the invention, the particles can be used to slowly release the active materials. For this purpose, the active material is first absorbed by the porous polyolefin particles, and then the material is released slowly. Drugs, fragrances, pesticides, attractants and fertilizers may be mentioned as examples of active substances.

Porous polyolefin particles are also suitable for (optionally) absorbing certain materials. Examples are absorption of malodorous components, leaks and / or emulsions or purification of contaminated water streams, in which the porous polyolefin particles absorb contaminants. Polar porous polyolefin particles such as EVA allow the particles to absorb polar materials well.

The invention will also be described in detail with reference to the following examples, but is not limited thereto.

In the examples, the density (d) was measured according to ASTM standard D792-66. Melt Index (MI) was measured according to ASTM Standard D1238, Condition E.

DSC measurements were performed using Perkin-Elmer DSC-7. Temperature and energy correction was performed based on melting of indium and lead. The temperature measurement during cooling is adjusted based on the solid-solid transition of 4,4'-azoxy-anisole. A heating and cooling rate of 5 ° C./min was used during the measurement.

The measurement results of the examples are provided in Table 1.

Example I

In a Erlenmeyer flask, 60 g of LDPE (with a density of 918 kg / m 3 and MI of 8 dg / min) was dissolved in 190 g of heptane at about 95 ° C. under reflux. To the solution was added 0.6 g of LLDPE (with a density of 936 kg / m 3 and a MI of 4.4 dg / min) and dissolved. Next, the solution obtained above was injected into a vessel containing 500 g of water at about 74 ° C. together with 0.4 g of nonionic surfactant and C ₁₁ -oxo alcohol polyglycol ether having seven ethylene oxide units. The temperature was kept constant at 78 ° C. with stirring (200-300 W / m 3) with a stirrer-blade and 10 N / h continuous nitrogen flow, and the water and polyolefin solutions were dispersed for 5 minutes and thereafter about 1 It cooled to room temperature at the cooling rate of ° C / min. The particles were then separated by a sieve. As a result, solid, mostly spherical, wet polyolefin particles having a d50 of 1.85 mm were obtained. The particles were then dried in a vacuum stove at room temperature and <10 kPa pressure. The structure of the polymer particles was visualized by scanning electron microscopy (SEM) scanning. Magnifications of 80 *, 500 *, 1000 * and 2000 * porous polyolefin particles are shown in FIGS. The figures show open pore structures that interconnect the cells. The narrow particle distribution is shown in FIG. 5, where the particles have a more uniform size.

Example II

Polyolefin particles were prepared according to Example I. 0.4 g of isotridecyl alcohol polyglycol ether with 8 ethylene oxide units was used as the nonionic surfactant.

Example III

Example II was repeated with 0.6 g of nonionic surfactant. Polyolefin particles homogeneous and mostly spherical were obtained. Comparison of Examples II and III shows that the porous polyethylene particles become smaller when the concentration of nonionic surfactant is increased.

Example IV

80 g of LDPE (with density of 918 kg / m 3 and MI of 8 dg / min) in a Erlenmeyer flask was dissolved in 190 g of heptane at about 95 ° C. under reflux. To the solution 0.8 g of LLDPE (with a density of 936 kg / m 3 and MI of 4.4 dg / min) was added and dissolved. The solution obtained above was poured into a vessel containing 580 g of 74 ° C., to which 0.4 g of C ₁₁ -oxo alcohol polyglycol ether having seven ethylene oxide units was added as a nonionic surfactant. It was then stirred and cooled as described in Example I. Polyolefin particles were separated by a sieve. The particles were dried in a fluidized bed having a nitrogen flow of 40 ° C. The higher the concentration of polyolefin in the polyolefin solution, the more porous polyolefin particles having a lower porosity are obtained.

Example Ⅴ

85 g of LDPE (with density of 918 kg / m 3 and MI of 8 dg / min) was dissolved in 300 g of heptane at reflux at reflux. To the solution was added 0.85 g of LLDPE (with a density of 936 kg / m 3 and MI of 4.4 dg / min). 750 g of 74 ° C. water in which 0.6 g of C ₁₁ -oxo alcohol polyglycol ether having 7 ethylene oxide units was dissolved as a nonionic surfactant was injected into the solution. The rest of the preparation was carried out as in Example I.

Example VI

11 kg of LLDPE (with a density of 918 kg / m 3 and MI of 8 dg / min) and 0.1 kg of LLDPE (with a density of 936 kg / m 3 and MI of 4.4 dg / min) were heptane 35 at about 95 ° C. Dissolved in kg within 30 minutes. The solution was stirred while supplying about 1000 w / m 3 of power, and 125 L of water at about 80 ° C. to which 0.125 kg of a nonionic surfactant (C ₁₁ -oxo alcohol polyglycol ether having a chain composed of seven ethylene oxide groups) was added was added. It was injected into the containing container. The stirring batch consists of a MIG stirrer with four baffles. The pressure increased because the heptane / water mixture reached its azeotropic boiling point. After addition of the organic phase, the mixture was cooled at a rate of about 1 ° C./min. After the mixture was cooled to 30 ° C., it was poured into a sieve to separate the aqueous phase. After separation, polyolefin particles with the majority of spherical diameters of 3 to 4 mm remain. The particles were dried in a continuously oscillating fluidized bed with a nitrogen cycle, and the inlet fluidized gas had a temperature of 40-60 ° C. The bed temperature gradually increased from 5 to 60 ° C.

Porous polyolefin particles exhibited comparable properties to the particles prepared in Example I.

Example Ⅶ

Example VI was repeated except that 37 kg of cyclohexane was used. The particles were inactivated with nitrogen, dried in a tray dryer with a pressure of <10 Pa and a plate temperature of 20 ° C. After about 48 hours, the plate temperature rose to 50 ° C.

Example Ⅷ

190 g of n-heptane, 60 g of LDPE having a density of 918 kg / m 3 and a MI of 8 dg / min, 0.6 g of LLDPE having a density of 936 kg / m 3 and a MI of 4.4 dg / min, and the lime were injected into the vessel. The stone liquor consists of 580 g of demineralised water and 0.40 g of C ₁₁ -oxo alcohol polyglycol ether with seven ethylene oxide units. The resulting mixture was inactivated with nitrogen and heated to 95 ° C. with stirring (200 W / m 3) with a stirrer with an inclined blade. After the stirrer was stopped, wait for complete phase separation. The two phase system was cooled to 25 ° C. with stirring at 1 ° C./min. After the polyolefin particles were separated by a sieve, solid and majority spherical particles were obtained. The particles were dried in a vacuum stove at room temperature and <10 kPa pressure.

Example Ⅸ

Example VII was repeated except that the LDPE used had a density of 932 kg / m 3 and an MI of 8 dg / min.

Example Ⅹ

17 g of polypropylene having a density of 904 kg / m 3 and a MI of 19 dg / min was dissolved in 190 g of p-xylene at 130 ° C. in a Erlenmeyer flask. The resulting solution was then poured into a vessel containing a stone liquid having a temperature of 90 ° C. The stone liquor consists of 780 g of demineralised water and 2.0 g of fatty alcohol polyglycol ether with nine ethylene oxide units. The resulting mixture was inactivated with nitrogen. The water and the polyolefin solution were stirred (250 W / m 3) with a stirrer with a beveled blade to disperse for 5 minutes and then cooled to 25 ° C. at a rate of 1 ° C./min. The formed particles were then separated from the water by a sieve. Solid, mostly spherical, wet polyolefin particles were obtained. The particles were dried in a fluidized bed by a flow of nitrogen having a temperature of 5 to 40 ° C. of the dry gas. During evaporation of the solvent the temperature of the product did not rise above 20 ° C. The porosity was 77%.

Comparative Example A

In a Erlenmeyer flask, 60 g of LDPE (with a density of 918 kg / m 3 and MI of 8 dg / min) was dissolved in 190 g of heptane at about 95 ° C. under reflux. The solution was then cooled to 80 ° C. and poured into a vessel containing 500 g of water at about 74 ° C., to which 0.4 g of a surfactant (alkane sulfonate having an average chain length of 14.5 C atoms) was added. While maintaining the temperature at 78 ° C., the polyethylene solution was dispersed in water for 5 minutes by stirring (250 W / m 3) with a stirrer equipped with 10 L / hour continuous nitrogen flow and an inclined blade, and cooling rate of about 1 ° C./min. Cooled to room temperature. The particles were then separated by a sieve. This resulted in wet gel particles that were mostly solid. The particles were dried in a vacuum stove at room temperature and <10 kPa pressure.

Porous polyolefin particles with very wide particle size distributions are formed (see FIG. 6).

Comparative Example B

158 g of n-heptane, 52 g of LDPE having a density of 926 kg / m 3 and MI of 4 dg / min, 0.6 g of di-ethylbenzylidene sorbitol (NC-4, manufactured by Mitsui Toatsu), and the stone were Injected. The stone liquor consists of 580 g of demineralised water and 0.4 g of C ₁₁ -oxo alcohol polyglycol ether with seven ethylene oxide units. The resulting mixture was inactivated with nitrogen and heated to 95 ° C. with stirring (200 W / m 3) with a stirrer with an inclined blade. After the stirrer was stopped, wait for complete phase separation. The two phase system was cooled to 25 ° C. with stirring at 1 ° C./min. After the polyolefin particles were separated by a sieve, solid particles showing a wide DOD were obtained. The particles were dried in a vacuum stove at room temperature and <10 kPa pressure.

Comparative Example C

In a Erlenmeyer flask, 45 g of LDPE having a density of 918 kg / m 3 and an MI of 8 dg / min were dissolved in 330 g of cyclohexane at about 80 ° C. under reflux of cyclohexane. 0.38 g of di- (ethylbenzylidene) sorbitol (NC-4, manufactured by Mitsui Toatsu) was added to the solution as nucleation product. The solution was injected into a vessel containing about 750 g of water at about 65 ° C., and 0.63 g of a surfactant (alkane sulfonate having an average chain length of 14.5 C atoms) was added thereto. The mixture was dispersed for 20 minutes while stirring with a power of about 200 W / m 3, at which time a portion of the cyclohexane was evaporated. The mixture was then cooled to room temperature at an average cooling rate of about 0.6 ° C./min. The mixture was fractionated to obtain hard, majority spherical gel particles having a particle size of about 2-3 mm. The particles were dried in a vacuum stove at room temperature and <10 kPa pressure. Porous polyolefin particles were formed.

Results of the Example Example / Comparative Example ε (%) E _1a (%) t _a (minutes) DOD D50 (mm) I 43 116 1.2 0.32 1.9 Ⅱ 40 95 0.8 0.31 3.4 Ⅲ 36 106 0.7 0.23 1.6 Ⅳ 28 100 0.5 0.16 3.5 Ⅴ 50 n.d. n.d. 0.13 1.5 Ⅵ 47 102 0.8 n.d. n.d. Ⅶ 44 108 n.d. n.d. n.d. Ⅷ 45 n.d. n.d. 0.23 3.7 Ⅸ 60 112 0.8 0.40 2.4 Ⅹ 77 n.d. n.d. 0.24 2.8 A 30 n.d. 0.7 0.76 n.d. B 49 n.d. 0.8 0.47 5.9 C 61 n.d. 0.8 0.76 6.0

n.d. = Not measured.

Claims (27)

1) preparing a polyolefin solution by dissolving at least one crystallizable polyolefin in a solvent in the absence of nucleation, 2) dispersing the obtained polyolefin solution in the non-solvent in the presence of a surfactant at a temperature higher than the crystallization temperature of the polyolefin in the polyolefin solution to form a multiphase system, 3) The obtained polyphase system is cooled to a temperature below the crystallization temperature of the polymer in the polymer solution while stirring at a rate of 0.05 to 10 ° C./min to form solid polyolefin particles, 4) separate the polyolefin particles, 5) A method for producing porous polyolefin particles consisting of drying the polyolefin particles. The method of claim 1, Dissolving and dispersing the polyolefin in the solvent and the non-solvent in a single step. The method according to claim 1 or 2, Wherein a portion of the solvent is evaporated from the formed multiphase system before the multiphase system is cooled. The method according to any one of claims 1 to 3, The polyolefin is a manufacturing method characterized in that the polyethylene. The method according to any one of claims 1 to 3, The polyolefin is a production method characterized in that the copolymer of ethylene and α-olefin. The method according to any one of claims 1 to 3, The polyolefin is a production method, characterized in that the polypropylene. The method according to any one of claims 1 to 6, The solvent is n-alkanes, i-alkanes, cycloalkanes, alkenes, cycloalkenes, hydrogenated or non-hydrogenated aromatic compounds, polycyclic aromatic compounds, chlorinated hydrocarbons or a mixture thereof. The method of claim 7, wherein The solvent is cyclohexane, boiling point spirit, heptane or octane. The method according to any one of claims 1 to 8, The concentration of the polyolefin in the polyolefin solution is characterized in that 10 to 35wt.%. The method according to any one of claims 1 to 9, The non-solvent is a manufacturing method, characterized in that the polar compound when a non-polar polyolefin is used. The method of claim 10, The cost-effective agent is characterized in that water, acetone, methanol, ethanol or a mixture of the compounds. The method according to any one of claims 1 to 11, The polyphase system is cooled at a rate of 0.1 to 5 ° C / min. The method according to any one of claims 1 to 12, During drying, the partial pressure of the solvent in the vapor phase is at most 20% of the normal vapor pressure of the solvent at the drying temperature. The method of claim 13, The drying method is characterized in that carried out by the stripping gas. The method according to any one of claims 1 to 14, A nonionic surfactant is present. The method of claim 15, Wherein the nonionic surfactant is an alkyl polyglycol ether or an ethoxylated fatty acid amine. Porous polyolefin particles, characterized in that the porous polyolefin particles satisfy the following conditions: A) 5-85% porosity B) effective load factor of at least 95% (E _1A ), Where E _1A is the effective loading rate of the polyolefin particles with the absorbent, m _A is the absorbent weight of the absorbent, ρ _A is the density of the absorbent, m _PO is the weight of the porous polyolefin particles before absorbing the absorbent, ρ _PO Is the density of the polyolefin) C) absorption time of at least 10 minutes (t _a ) D) Dispersion degree of particle size distribution of <0.4. The method of claim 17, Polyolefin particles, characterized in that the porosity is 35-85%. The method of claim 17 or 18, E _1A > 99% polyolefin particles. The method of claim 17 or 18, Dispersion degree is <0.2, The polyolefin particle characterized by the above-mentioned. The method according to any one of claims 17 to 20, Wherein said particles are made from one polyolefin. The method of claim 21, Wherein said polyolefin has a DSC crystallization peak at least 5 ° C. wide. The method of claim 21 or 22, The polyolefin is a polyolefin particle, characterized in that the LDPE. The method according to any one of claims 17 to 20, Wherein said particles are prepared from a mixture of polyolefins, polyolefins or polyolefins in a mixture having a crystallization temperature higher than the crystallization temperature of other polyolefins. The method of claim 24, The highest crystallization peak temperature is at least 5 ° C. higher than other polyolefins or polyolefin crystallization peak temperatures. Method and use of the porous polyolefin particles as described and described in the Examples. The method according to any one of claims 17 to 25 or as a carrier, absorbent or concentrate of an additive released in a slow and / or controlled manner. Use of the obtained porous polyolefin particles.