PL232993B1 - Method for production of micronised wax - Google Patents

Description

Description of the invention

The subject of the invention is a method of producing micronized wax.

There is a known method of producing micronized waxes in which the molten wax is sprayed through a nozzle and sprayed onto very fine wax particles. In the next step, these particles are cooled and sieved to remove larger particles.

In another method, the waxes are micronized with special grinding equipment, for example jet mills, which are equipped with screening sections integrated in the grinding chamber.

A process for the production of wax is also known from the patent description DE 10064800 concerning the invention entitled "Micronized polyethylene waxes and their use in cosmetic preparations and as an abrasive for toothpaste." It is a process of high pressure (from 400 to 4000 bar) (^ polymerization of ethylene with the addition of aliphatic and alicyclic ketones as a regulator of the molecular weight of the wax. The production of the wax takes place at a temperature of 180 to 350 ° C. The obtained polyethylene wax is micronized to obtain particles having a maximum size of 100 µm The description states in an exemplary embodiment that one of the methods of obtaining wax is to use a jet mill for micronization.

From US 4,846,887, a micronized wax powder is known, characterized in that it contains at least 95% by weight of particles smaller than 32 μm (claim 1). The method of producing a wax according to claim 1 2, includes only (2) stages. First, the substantially spherical wax starting material is first melted and then nebulized in a conventional manner (e.g. by atomization) to obtain a substantially spherical particle powder containing at least 60% by weight of particles smaller than 96 Pm.

In the second stage, the powder is comminuted (milled). Dependent Claim 11 states that a jet mill is used to micronize the wax. This method does not include the operations of preparing the wax for granulation, e.g. it does not specify the wax melting points, its refining, thermal stabilization and the addition of additives influencing the specific properties of the final product.

One-step granulation methods, which produce granules with particle sizes below 100 μm, are characterized by a high degree of explosion hazard. According to the literature, for example, "Burning and fuels" by prof. W. KORDYLEWSKI (ed.); Publishing House of the Wrocław University of Technology; Wrocław 2005, polyethylene dusts are classified as highly or very highly explosive (p. 286).

On the other hand, “The particle size has an important influence on the dust explosiveness, because the size of the dust surface per unit mass depends on the fragmentation of the dust, and thus the speed of dust reacting with oxygen. The finer the dust, the more explosive it is. Conversely, dusts with particle sizes greater than 500 pm do not pose an explosion hazard. (ibid. p. 288).

It is therefore desirable to develop a new method of producing micronized polyethylene wax with a very small particle diameter which does not present an explosion hazard.

The aim of the invention is to provide a safe, non-explosive, micronized polyethylene wax production process with the use of waste wax from a polyethylene production plant. The use of waste wax from the polyethylene production plant avoids the need for its disposal.

The essence of the method of obtaining the wax according to the invention is that the by-product from the installation producing polyethylene (PE) in the form of low-molecular wax in the form of solid wax, contaminated with light hydrocarbons, water and catalyst destruction products, constituting the input for the micronized wax production installation, is subjected to a slow, uniform heating from ambient temperature to 150 ° C, preferably 130 ° C, in order to melt and homogenize it, and then directed to a distillation (refining) unit, carried out under deep vacuum at a temperature of 130 ° C to 290 ° C.

The semi-finished product obtained in this way is combined with other synthetic and / or natural waxes and then subjected to thermal stabilization.

This mainstream then feeds into a countercurrent tower granulation plant where the atomization of the liquid is achieved by a sectional centrifugal sprinkler. Surprisingly, it turned out that carrying out the process on this plant in such a way as to obtain wax granules with a diameter of less than 0.9 mm (900 µm), combined with a narrow diameter distribution, guarantees the explosion safety of the granulation process in which air is the cooling agent.

PL 232 993 B1

In the final phase, the granulate obtained in this way, the grain size and particle size distribution of which results in a significant increase in grinding efficiency, is micronized, in particular with the use of a jet mill equipped with a high-speed air separator, aimed at obtaining a product with a narrow particle size distribution and an average particle diameter not exceeding 8 ..m.

Preferably, the distillation is multistage and is preferably carried out at a temperature of 250 ° C with an inert gas.

Preferably, before the thermal stabilization process, additional components are introduced in the form of natural or synthetic waxes with parameters depending on the expected properties of the target product.

Preferably, the secondary waxes are reed or Fischer-Tropsch wax or amide wax.

Preferably, the micronization process is carried out with the use of grinding air with a pressure of 5 to 10 bar, preferably 8 bar, as the energy factor causing grinding (micronization).

The possibility of processing waste wax has the advantage of being an alternative to environmentally polluting disposal.

Unexpectedly, it turned out that the use of countercurrent tower granulation in the production of micronized wax allows to eliminate the risk of explosion.

The countercurrent tower granulation operation produces particles nearly 10 times larger than in the nozzle spraying methods. Carrying out the granulation on the counter-current tower granulation installation guarantees the explosion safety of this process with the use of air as a cooling medium. This significantly distinguishes this method from the methods of spraying molten wax by means of nozzles, which obtain granules with diameters of up to 100 µm, and in order to prevent the formation of an explosive mixture, it is necessary to use expensive inert gases for cooling, e.g. nitrogen.

The wax obtained according to the invention has a preferred melting point of not more than 140 ° C, and the addition of other waxes prior to the thermal stabilization process creates the advantageous feature of shaping the final properties of the micronized wax.

The subject of the invention is explained in the following examples of laboratory application of the method. P R Z Y K Ł A D 1

Wax purified from water, light hydrocarbons and catalyst destruction products [solidification point: 94-100 ° C, dropping point: 102-114 ° C, viscosity (140 ° C): <40 cP, penetration (0.1 mm): 7 -11], coming from a polyethylene production plant, with a molecular weight of 400-1500 g / mol, was slowly heated from ambient temperature to 130 ° C and melted in a 1 liter flask.

This intermediate was subjected to ultrasonic homogenization for 30 minutes and then vacuum distilled at 150 ° C and heat stabilized in an incubator (140 ° C, 15 hours). To this wax was introduced in the amount of 40% (m / m) natural - reed wax [acid number (mg KOH / g): 20-30, dropping point: 78-82 ° C, viscosity (140 ° C): <40 cP, penetration (0.1 mm): 1-3]. The stabilized wax thus obtained had the following parameters:

Dropping point:

Temperature of solidification:

Penetration:

Viscosity (140 ° C):

68-72 ° C.

76-81 ° C.

0.7-1.3 (0.1 mm).

<20 cP.

P R Z Y K Ł A D 2

Wax purified from water, light hydrocarbons and catalyst destruction products [solidification point: 96-106 ° C, dropping point: 104-115 ° C, viscosity (140 ° C): <40 cP, penetration (0.1 mm): 1 -4], coming from a polyethylene production plant, with a molecular weight of 400-1500 g / mol, was slowly heated from ambient temperature to 140 ° C and melted in a 1-liter flask.

This intermediate was subjected to ultrasonic homogenization for 30 minutes and then heat stabilized in an incubator (135 ° C, 10 hours). This wax was supplemented with 50% (m / m) synthetic wax - Fischer-Tropsch [pour point: 105-120 ° C, drop point: 98-110 ° C, viscosity (140 ° C): <40 cP, penetration (0.1 mm): 0-3]. The stabilized wax thus obtained had the following parameters:

PL 232 993 Β1

Dropping point: 110-120 ° C. Acid number: 0 mgKOH / g. Penetration: <2 (0.1 mm). Viscosity (140 ° C): <20 cP.

The micronized waxes obtained by granulating and then micronizing the waxes of Examples 1 and 2 will have the above-mentioned properties.

EXAMPLE 3

In the operating conditions of the industrial installation, a trial production batch was made to obtain a micronized wax mixture of polyethylene wax from the installation for the production of polyolefins with a molecular weight of 400-1500 g / mol (50% m / m) and synthetic amide wax (50% m / m). The waste polyethylene wax was slowly heated from ambient temperature to 150 ° C and melted.

Then the wax was homogenized with the amide wax [acid number (mg KOH / g): <10, pouring point: 140-145 ° C, viscosity (140 ° C): <20 cP, penetration (0.1 mm): 1- 3], Purified liquid polyethylene wax was poured into the tank with a high-speed stirrer, and then, with the stirrer running, the amide wax was added in portions in such a way that the temperature of the mixture did not drop below 150 ° C.

An additional circulation system with a pump was used to better homogenize the mixture. The thus obtained homogenized wax had the following parameters:

Dropping point: 130-140 ° C. Acid number: <5 mgKOH / g. Penetration: <5 (0.1 mm). Viscosity (140 ° C): <40 cP.

This wax was subjected to vacuum distillation at a temperature of 250 ° C in the presence of nitrogen in order to remove catalyst destruction products, light hydrocarbons and water, so that the flash point of the purified wax was higher than 200 ° C [solidification point: 96-106 ° C, pouring point : 104-115 ° C, flash point: 200-220 ° C, viscosity (140 ° C): <40 cP, penetration (0.1 mm): 1-4],

After heat stabilization at 145 ° C for 10 hours, the mixture was subjected to a countercurrent tower granulation process. This resulted in a solid product with a melting point of 135 ° C and the following particle size distribution:

Sieve analysis Sieve dimensions [mm] 1.5 1.25 1.00 0.80 0.50 0.20 0.10 - 0.80% 0.50% 6.00% 58.20% 30.00% <0.10%

Legend: The numbers in percent represent the proportion of wax particles in the granulate with a diameter smaller than the corresponding sieve dimensions.

The tower granulation product was micronized in a jet mill under the conditions of the grinding air pressure (8 bar). The product obtained had the following particle size distribution:

Size distribution particle k [urn] dio d ₅ sts dijo dga dgg dioo 3.34 7.06 13.00 17.30 18.60 24.00

Comment: dio - means that 10% of the micronized wax particles have a diameter of do

3.34 µm, ad ₅₀ - means that 50% of the micronized wax particles have a diameter of up to 7.06 µm, etc.

PL 232 993 B1

Micronized waxes are used in particular in the paint and varnish industry, i.e. in every paint coating produced and used, construction, industrial, printing, powder paints, varnishes and impregnating agents. Each of these groups requires the use / application of a different type of wax, usually modified wax blends.

Waxes are used to modify water-based, solvent-based and powder systems. After their application to the substrate, the waxes migrate to the top of the coating, improving a number of properties, such as:

- faster and easier dispersion,

- matt or gloss effect,

- obtaining or increasing the hydrophobic effect,

- anti-blocking,

- degassing effect in powder paints.

The advantage of micronized waxes is that they can be easily applied to the system directly, i.e. without additional thermal energy. This method of application allows you to significantly reduce the amount of wax used to obtain the desired effects, compared to another form of wax (pearls, pastilles).

Claims (6)

Patent claims The method of producing micronized wax, characterized in that the by-product from the installation producing polyethylene (PE) in the form of low-molecular wax in solid form, contaminated with light hydrocarbons, water and catalyst destruction products, constituting the input for the micronized wax production installation, is subjected to a slow, evenly heated from ambient temperature to 150 ° C, preferably 130 ° C, in order to melt and homogenize it, and then directed to the distillation (refining) unit, conducted under deep vacuum and at a temperature of 130 ° C to 290 ° C, and the thus obtained intermediate subjected to thermal stabilization, and then this main stream is the input to the counter-current tower granulation installation, to obtain a granulate with a diameter of less than 0.9 mm and a melting point of not more than 140 ° C, and in the final phase, the granulate obtained in this way is subjected to micronization, in particular with the product oriented jet mill with an average particle diameter not exceeding 8 μm. 2. The method of producing micronized wax according to claim A process as claimed in claim 1, characterized in that the distillation is multistage. 3. The method of producing micronized wax according to claim The process of claim 1, characterized in that the distillation is preferably carried out at a temperature of 250 ° C in the presence of an inert gas. 4. A method of producing a micronized wax according to claim 1 The method of claim 1, characterized in that, during the thermal stabilization, additional waxes of natural or synthetic origin are introduced, with parameters depending on the expected properties of the target product. 5. The method of producing micronized wax according to claim 1 A process as claimed in claim 4, characterized in that the additional waxes are a cane wax or a Fischer-Tropsch wax or an amide wax. 6. A method of producing a micronized wax according to claim 1 A method according to claim 1, characterized in that the micronization process is carried out with the use of grinding air with a pressure of 5 to 10 bar, preferably 8 bar, as an energy factor causing grinding (micronization).