EP0878441B1 - Process and apparatus for filling and emptying bulk storage containers containing water-like dispersions - Google Patents

Description

The present invention relates to an improved method for filling and emptying storage tanks with aqueous Dispersions, whereby the storage tank is emptied via a line, the opening of which is in the lower part of the storage tank.

Aqueous polymer dispersions, such as those used for a large number of applications, such as. in the paint, adhesive industry, etc. used must meet increased quality requirements. One of these quality requirements is their durability.

The durability of dispersions is enhanced by the addition of preservatives as well as hygiene measures in particular.

It is particularly important when storing that the dispersion is not superimposed. For this is the type of filling and Emptying the storage tanks with vital importance.

Previous procedures used for filling and emptying of the storage tanks the same line. This line is in the ground attached to the storage tank, it occurs during the filling and removal processes migration of the upper dispersion layer, which is getting older, with all the consequences of possible infestation by microorganisms due to aging.

Another procedure uses a filling line, which on Head of the storage tank enters and its outlet opening in the Usually led to the wall. The drain line is located expediently at the bottom of the storage tank. Albeit after This principle largely follows the "first in - first out" principle can be complied with, the filling of above to the formation of deposits on the wall and to the undesirable Cause foaming. Wall covering is also not desirable, because the topping grows up and becomes the source of germs can be. Foaming is undesirable because of the foam slightly dried and to form "specks" (not redispersible Coagulate) in the product.

On the problem of filling and emptying storage tanks or storage of products caused by the infestation of microorganisms can be harmed in an article in the magazine Farbe & Lack, 99, year, issue 1, 1993, Pages 37 - 39 ff. The unwanted microbial Growth is particularly due to the components of the dispersion and causes the water content and to reduce this growth the addition of preservatives known as biocides is recommended.

To be able to reliably store high quality products, it is necessary, the so-called "first in - first out" principle fulfill. This means that the first placed in the storage tank Product parts are also correspondingly removed later be dissipated first to prevent aging of parts of the To avoid product.

In US-A 1 668 793 a device for filling Storage tanks with any liquids set out in which the Filling takes place via a rotatably mounted filling line is supported by one or more swimmers, so that the outlet opening follows the liquid level.

In order to minimize these problems, stirred storage tanks are suggested. Stirred storage tanks, however, are expensive and maintenance-intensive. Larger storage tanks, the contents of which are mixed by stirring have to be specially stiffened. Can too here to dry on the stirrer shaft or the stirrer blades come. Air can also enter the dispersion by stirring be entered, which is undesirable.

It was therefore the task of an improved method for Filling and emptying storage tanks to find the remedied disadvantages and a procedurally simple and economical storage of aqueous dispersions. In particular, the aim is to ensure the high quality of the Ensure storage tank containing aqueous dispersion permanently and damage to technical facilities like them can be caused by biocorrosion or biofouling. This problem is addressed in chemical engineering technology (67), 11/95, pages 1425-1430.

Accordingly, a method for filling and emptying Storage tanks with aqueous dispersions, taking the storage tank emptied via a line, the opening of which is in the lower part of the storage tank, which is characterized by is that you fill the storage tank with another line, the outlet opening in the storage tank in the level changes of the liquid surface Filling and removal processes follow, whereby the level of Exit opening adjusts so that the opening is approximately in Height of the liquid level.

The method according to the invention advantageously enables one Handling of the stored aqueous dispersions according to the principle first in - first out.

When filling, new product is placed near the surface and when it is removed, product becomes from the lower part of the storage tank taken. This advantageously results in a Layering the product in such a way that the product parts, which have been stored for the longest time, near the tapping point located and next removed and accordingly new added product parts on the surface almost as a new surface layer to be given.

It is particularly suitable when using non-agitated storage tanks. The additional apparatus resulting from the stirring Effort can thus be avoided and at the same time the ensures high quality of the stored aqueous dispersion.

So-called are particularly suitable for the method according to the invention Swimming proboscis, which are also used as swimming suction systems or Floating suction probes are used to fill the storage tank. These proboscis are usually made of flexible or rigid elements that are flexible via one or more swivel joints are interconnected, causing a change in length similar to a scissors principle is possible.

Such proboscis are already known and are for example from the companies Emco in Kirchhain, Connex in Kamen and Schwelm distributed in Schwelm.

So far, such proboscis have only been used for emptying, Examples of this can be found in the extraction of liquid phase from settling tanks or oil tanks.

The use of such a proboscis in the case of filling The skilled worker would not have storage tanks with aqueous dispersions considered, since gluing the pivot joints of the Proboscis would have feared from the dispersion. Farther is achieved by the combination of the filling according to the invention the swimming trunk and the removal from the lower part of the storage tank the advantageous stratification of the Product achieved.

By attaching a buoyancy body, the outlet opening the filling line advantageously the level changes of Follow liquid floating.

The buoyancy behavior can be affected by different sized buoyancy bodies to be changed. It is advantageously used however fillable floats that adapt to the density of the product to be stored with e.g. Water, diethylene glycol or other substances, e.g. Metal balls, filled and balanced become. In this way, the immersion depth of the Advantageously change the filling line and optimize it for specific products. In principle, the floats can be any geometric Have shapes. Floating balls or conical ones are preferred Floats, the tapered end of which dips into the dispersion, which may be arranged in pairs. Particularly preferred are hollow bodies made of stainless steel. Usually the proboscis held by one or two floats.

The storage tanks are usually still emptied from below.

The balance of the float (s) and thus the immersion depth the end of the filling line advantageously allows a largely foam-free filling of the storage tanks. So that will a drying of foam and the formation of coagulate avoided.

Through this type of filling of non-agitated storage tanks the freshly produced goods "from above" in the storage tank Avoiding the disadvantages mentioned above.

By emptying the storage container "from below" older goods for sale. The desired principle "first in - first out "is largely adhered to.

All flexible medium-resistant can be used as flexible filling lines Hoses are used.

Hollow bodies made of various are suitable as floating bodies Materials e.g. Plastic (polypropylene, polyethylene) or Stainless steel (V2A, V4A), or also rubberized or coated Steel container. Foam floats are also suitable Plastics that may be coated. In the simplest embodiment become plastic tanks with closed lids used. The floating body is preferably deflectable with the Filling line connected. The float is usually flexibly connected to the end of the filling line, the filling line can also pass through the float.

The outlet opening of the filling line is advantageously located just below the liquid surface, preferably about 50 to 200 mm below the liquid level, the outlet opening a cross-sectional area that is the single to multiple cross-section corresponds to the filling line. The outlet opening of the Filling line can also be located just above the liquid surface are located, the height is to be chosen so that it there is no undesirable foaming. The foaming but is also dependent on the cross section of the filling line and the volume flow of the dispersion with which the storage tank is filled , the diameter of the filling line is preferably 50 to 200 mm, particularly preferably 80 to 150 mm or is 100 mm. Geometric design of the outlet opening, the filling under or via mirror and volume flow, the parameters are product-specific can be optimized through routine tests.

Preferred positions of the outlet opening depend among other things. of the viscosity and foaming tendency of the dispersion used from.

For dispersions with relatively high viscosities (larger, for example 2000 mPas), it is not recommended, for example, to open to be positioned deeply below the liquid level, as in In this case, there may be no product exchange on the surface would result and thus the desired principle first-out would not be fulfilled.

The outlet opening can be changed by routine tests, for example, several openings are also through bifurcations and branches possible.

The outlet opening is preferably in the middle of the Liquid level to ensure a uniform spreading of the dispersion in all directions.

In a preferred embodiment, the outlet opening is at End of the swimming trunk attached via a swivel so that the Cross-sectional area of the opening parallel to the liquid level stands.

The outlet opening can e.g. be bell-shaped. A baffle plate can preferably be mounted in front of the outlet opening be, whereby the product jet is fanned out and on the surface better distributed. This baffle is preferred height adjustable and with the end of the filling line, for example fastened by screw connections.

Through this filling and removal technology for unstirred storage containers the older goods are sold earlier. The end Principle to be favored from a hygienic point of view "first in - first out "is thus largely met.

Especially standing cylindrical storage tanks are expedient preferred, but it can also square, rectangular storage tanks or oval cross-section can be used. Likewise lying cylindrical or rectangular containers can also be advantageous operated in the manner described. Cylindrical storage tanks are advantageously used, the diameter should be chosen so that the Filling the spreading dispersion up to the wall arrives. Standing cylindrical storage tanks are advantageous used, where the inside diameter of the storage tank in Relationship to the diameter of the outlet opening of the filling line is in a range from 10 to 120, preferably 20 to 50.

The storage containers are filled and emptied in the Usually by pumping the dispersions. The filling and emptying lines can advantageously be designed piggable if necessary become.

Figures 1 to 3 show exemplary arrangements according to the method according to the invention.

In Figure 1, the filling line (1) of a storage tank (7) with a swimming trunk (2) connected to a plurality of swivel joints (3) having. The float is located at the end of the proboscis (4) and the outlet opening (5) is slightly below the Liquid surface (6).

The bottom of the storage tank is designed with a slope that the Liquid is led to the sampling line (8).

Figure 2a shows a similar arrangement. The outlet opening (5) is here above the liquid surface (8).

FIG. 2b shows a baffle plate mounted by means of struts (10) (9) at the outlet opening (5).

The angle α can be optimized by a routine experiment in order to good and even spreading of the dispersion when filling achieve.

A baffle plate can be seen in FIG. 2c, the distance H of the Baffle plate from the outlet opening by means of the elongated hole 11 can be adjusted.

To avoid dead spaces when using this baffle the baffle has one or more holes. It can also be made of perforated sheet.

Preferred designs of the baffle plate can be made by a person skilled in the art Routine attempts can be determined. When choosing the angle α are in particular the diameter of the storage tank and viscosity and foaming tendency of the dispersion is important.

Figure 3 shows a similar arrangement in which a flexible Line (2) is used, which by means of an eyelet (3) and the guide rope (10) tensioned by the fastening eyes (9) is controlled.

In this example, the outlet opening (5) is above the Liquid levels (6).

According to the process of the invention, all aqueous Polymer dispersions are stored.

This type of storage is particularly advantageous if the Dispersions are no preservatives or preservatives obtained in a relatively low concentration. For example, this is the case when the dispersions for further processing be temporarily stored. Such preservatives will for example in JOCCA, 1991 (9), pages 324-328.

Suitable preservatives are e.g. Formulations of the 1,2-Benzisothiazolin-3-one sodium salts in a mixture Water and propylene glycol, e.g. Proxel XL2, from ICI, Formulations of biocidal (chlorine) isothiazolones, e.g. Acticide LA from THOR CHEMIE GmbH, Kathon LX plus from ROHM & HAAS. Aqueous dispersions based on the above Kind stored advantageously can be e.g. Dispersions based on ethylenically unsaturated Connections such as based on (meth) acrylic acid esters, Butadiene, styrene, vinyl acetate, (meth) acrylamide, Acrylonitrile, (meth) acrylic acid etc. Such dispersions are known.

The dispersions can optionally be made up. The aqueous dispersions can have the character of intermediate products have, but they can also be used products e.g. are available in pigmented form for painting purposes.

Other packaging materials are e.g. Diols such as butyl glycol, Butyl diglycol, diethylene glycol, alcohols such as e.g. Ethanol, iso-propanol and octadecanol-1, solvents such as Lusolvan FBH (BASF AG), complexing agents e.g. based on ethylenediaminetetraacetic acid, e.g. Trilon B liquid (BASF AG), synthetic Resin solutions such as aqueous solutions of polyvinyl methyl ethers, such as. Lutonal M 40 (BASF AG), solutions of ammonium polyacrylates, such as. Collacral P (BASF AG), plasticizers, such as e.g. Dibutyl phthalate, e.g. Palatinol C (BASF AG), anionic Dispersions of montan ester wax, e.g. lubricant dispersion 8645 (BASF AG), chemical compounds such as e.g. urea and ethylene urea, sodium hydroxide solution, potassium hydroxide solution, ammonia, calcium hydroxide. Zinc nitrate, zinc oxide, emulsifiers such as e.g. alkyl phenol ethoxylates, e.g. Emulsifier 825 (BASF AG), block copolymers based on propylene and ethylene oxide, defoamers such as. Dapro DF 900 from KRAHN CHEMIE GmbH and Byk-033 from BYK-CHEMIE GmbH, Wesel, Nopo 8034 E / D from HENKEL KGaA, Compounds such as benzophenone, solvents such as white spirit and Acetone, polyvinyl alcohols etc., modified rosins, such as. Tacolyn 3179 from HERCULES, Permatac A751 from ALLIANCE TEHCNICAL PRODUCTS (ATP), Snowtac types from AKZO NOBEL.

The method according to the invention is also particularly suitable for the storage of higher viscosity products. The viscosities are in in this case at more than 500 mPas, preferably above 5000 mPas, particularly preferably over 7000 mPas.

The water content of the aqueous polymer dispersions is preferred between 20 and 80% by weight.

The dispersions can be (co) polymers in dispersed form contain. They preferably contain at least one monomer of the following monomer groups: (meth) acrylic acid ester, (Meth) acrylic acid, butadiene, styrene, vinylidene chloride, acrylonitrile, Vinyl acetate.

The aqueous dispersions preferably have a pH of over 3, particularly preferably over 5, very particularly preferred over 7.

Dispersions can advantageously be used in the process according to the invention Processes are used that have a biocide concentration of less than 1000 ppm, preferably less than 50 ppm.

The method according to the invention enables a process engineering simple and economical storage of watery Dispersions. The aging of parts is advantageous the stored dispersion avoided and thus a permanent high quality guaranteed.

Claims (9)

1. A method of filling and emptying storage tanks containing aqueous dispersions, where the storage tank (7) is emptied via a line (8) whose opening is located in the lower section of the storage tank, which comprises filling the storage tank with another line (1), whose outlet (5) in the storage tank follows the changes in the level of the liquid surface in the course of filling and removal procedures, the level of the outlet being adjusted such that the opening is located approximately at the height of the level (6) of the liquid.
2. A method as claimed in claim 1, wherein unstirred storage tanks are used.
3. A method as claimed in claim 1 or 2, wherein single- or multi-joint float trunks are employed to fill the storage tank.
4. A method as claimed in any of the preceding claims, wherein dispersions having a water content of from 20 to 80% by weight are employed for storage.
5. A method as claimed in any of the preceding claims, wherein the aqueous dispersions comprise (co)polymers in dispersed form which include at least one monomer from the following monomer groups: (meth)acrylates, (meth)acrylic acid, butadiene, styrene, vinylidene chloride, acrylonitrile and vinyl acetate.
6. A method as claimed in any of the preceding claims, wherein aqueous dispersions having a pH of more than 3, preferably a pH of more than 5, are employed.
7. A method as claimed in claim 6, wherein aqueous dispersions having a pH of more than 7 are employed.
8. A method as claimed in any of the preceding claims, wherein aqueous dispersions having a biocide concentration of less than 1000 ppm, preferably less than 100 ppm, are employed.
9. A method as claimed in claim 8, wherein aqueous dispersions having a biocide concentration of less than 50 ppm are employed.

Images