DE10126679A1 - Mixing polymer resins in exact amount with solvents or other resins on a large scale, e.g. for production of polyisocyanate solutions, involves adding liquid resin or resin melt to a pumped circulating system with a short dwell time - Google Patents

Abstract

Mixing polymer resins in exact amounts with solvents and/or other resins on a large scale in a pumped circulating system involves addition at up to 280 deg C and 1-100 bar with a dwell time of 1-30 minutes and a circulation rate of up to 50 m<3>/h, using resins which are liquids or solid melts at room temperature, the mixing temperature being above the solvent boiling point or the resins being poorly miscible. A method for mixing polymer resins with solvents and/or other polymer resins in exactly defined proportions in a pumping apparatus on the technical or industrial scale. The method involves (a) the addition of two or more components in a temperature range from ambient to 280 deg C and a pressure range from ambient to 100 bar, with a residence time of 1-30 minutes and any circulation flow rate up to 50 m<3>/h and (b) the use of polymer resins which are liquids or solidified melts at room temperature, where the mixing temperature is above the boiling point (at ambient pressure) of the solvent(s) or the resins are poorly miscible with one another or with the solvent(s).

Description

The invention relates to a method for adjusting a mixture of liquid with precisely defined proportions. This Ver is particularly suitable drive to mixing polymer resins with solvents and / or others Polymer resins on an industrial and industrial scale.

The polymer resins to be mixed can be:

• a) Solid resin melts, which must be conveyed hot (up to 250 ° C) so that don't freeze them. Your direct quantity entry is due to the high Temperature or the high melt viscosity difficult or not possible.
• b) low or high viscosity liquids at room temperature. Not infrequently these liquid resins are difficult or only within one mix certain temperature range. The direct quantity recording of highly viscous liquid resins are also difficult or not possible.

Several methods for mixing polymer resins with solvents or other coating resins are known which, for. B. in paddle mixers as described in EP-A 0 726 091 can be carried out:

• 1.Solid resin melts, or low and highly viscous liquids that are difficult to mix or can only be optimally mixed within a temperature range, are continuously immediately pre-dissolved with solvent or with low-viscosity paint resin using counters or mass flow meters in a pre-dissolving kettle and in downstream, discontinuously operated dissolving kettles pumped for final adjustment. The final setting with solvent (counter, mass flow measurements or pressure load cells on the boiler) for the finished product is carried out using laboratory analyzes. After approval, the finished product is pumped into containers, containers, settling tanks or tankers via discontinuously operated filling boilers.
  Technical data of the process
  One pre-dissolving boiler (with reflux cooler for solvents with low boiling temperature) per mixing partner, at least two dissolving boilers and at least two filling boilers with the corresponding pumps and process control equipment. All boilers can be temperature-controlled and stirred tanks.
• Solid resin melts are premixed in small campaigns continuously above the melting point in a temperature-controlled static mixer with solvent or low-viscosity liquid resin and then finally set in a stirred tank using laboratory analyzes with the addition of solvent using a counter, mass flow meter or measuring the weight gain of the tank. The liquid mixture from the temperature-controlled dissolving kettle is then emptied into containers or the like.
  Technical data of the process
  A static mixer and a temperature-controlled dissolving kettle with agitator with appropriate pumps and process control equipment, which also serves as a filling kettle after the goods have been set.
• 3. In the case of solid resins and solvents (or low-viscosity liquid resin) with significant density differences, the resin is continuously pre-dissolved in a pre-dissolving kettle as in 1. and then continuously set in a further dissolving kettle in closed-loop operation via density measurement. The release kettle is kept at a constant level and overflows into several filling kettles. Laboratory analyzes serve to ensure product quality. The goods only have to be readjusted sometimes.
  Technical data of the process
  For each mixing partner, an intermediate dissolving boiler (with a reflux condenser for solvents with a low boiling temperature), a setting boiler with a pumping device and density measuring device and at least two filling boilers with corresponding pumps and process control equipment. All boilers are stirred tanks and can be tempered.
• 4. In the case of solid resins and solvents (or low-viscosity liquid resin), as in 1. and 3., the resin is continuously pre-dissolved in a pre-dissolving kettle and then continuously placed in another loosening kettle kept at constant temperature in circulating mode via viscosity measurement. The dissolving kettle is kept at a constant level and overflows into several filling kettles. The ready mix must be readjusted more often.
  Technical data of the process
  For each mixing partner, an intermediate dissolving boiler (with a reflux condenser for solvents with a low boiling temperature), a setting boiler with a pumping device and a viscosity measuring device, and at least two filling boilers with corresponding pumps and process control equipment. All boilers are stirred tanks and can be tempered.
• 5. In the case of highly viscous resins (solid resin melts or highly viscous liquid resins), the hot resin is fed directly, ie without continuous premixing (intermediate dissolving kettle, static mixer, etc.), into discontinuously operated stirred kettles with the solvent provided and then adjusted using laboratory analyzes. The submission of a partial amount of solvent is necessary to ensure stirrability. If several solvents are required for the mixture, at least one solvent must be presented.
  Technical data of the process
  At least two stirrable, temperature-controlled dissolving or filling boilers with appropriate technical equipment.
• 6. In the case of stirrable liquid resins, the solvent setting is carried out as in 5. without continuous premixing. The solvent need not be presented here. There are two types:
  • 1. 6.1 The final setting is done in dissolving kettles with the help of laboratory analyzes. If the result is good, the finished product is pumped into the filling kettle and filled from there.
    Technical data of the process
    For each mixing partner at least two stirrable temperature controlled dissolving boilers and filling boilers with pumps and corresponding process control equipment (process control technology).
  • 2. 6.2 The solvent or solvents are added to the combined solvent and filling kettles. The setting of the product is carried out with the help of laboratory analyzes. Then it is released from the dissolving kettle for filling.
    Technical data of the process
    At least four stirrable, temperature-controlled dissolving / filling kettles with pumps and appropriate PLT equipment for a maximum of four solvents.

In cases 5 and 6, the laboratory analyzes can be carried out in the final setting be reduced so that the mixing container is designed as a weighing container.  

These known methods have the following disadvantages:

• 1. The recording of the incoming resin is not accurate unless the The use of weighing kettles or mass flow meters is possible. of is because of the solvent addition - with the correspondingly frequent sampling and interim analyzes - multiple: You have to follow the specifications Approach a just attitude.
• 2. Sometimes too much solvent is added, which leads to reworking tion or leads to waste.
• 3. With all previous methods, the thermal load on the paint resin be relatively high, which leads to deterioration of the resin quality. The Ver deterioration in resin quality can e.g. B. in an increase in color number, one Cleavage of monomers or some other kind of secondary product formation exist. Method 2 results in thermal stress due to the high temperature of the static mixer and the other methods due to the long dwell time in the hot resin pipe to the stirred tanks, or by the slow mixing in the stirred tank.
• 4. Presetting the hot resin in the free-ventilated pre-release boiler at the Methods 1, 3 and 4 with low-boiling solvents lead to exhaust air problems that a condenser mounted in the exhaust pipe and a require cooled container jacket.
• 5. When starting and stopping, the pre-release boiler must be heated up and in stationary state of the resin supply can be switched to cooling.
• 6. A packaging system usually exists for a stationary operation Solvent, a predetermined solvent mixture or a low viscous liquid resin from at least four stirred tanks (e.g. two loops  kettles and two filling kettles) with the corresponding pump and Filter stations and are piped together. That means the space requirement and the investment is correspondingly large.
• 7. If several solvents (or low-viscosity liquid resins) are used, the The number of stirred tanks is correspondingly larger.
• 8. The effort involved in switching to a new solvent (or low-viscosity liquid resins) is complex and costly (cleaning costs, installation costs, review of security concepts).
• 9. The filtering effort is much greater due to the risk of contamination of the containers with the associated accessories and the greater piping effort for the following reasons:
  • 1. 9.1 The much larger surfaces of the boiler walls.
  • 2. 9.2 The discontinuous mode of operation of the packaging containers: The rest of the moisture-emptied containers can harden as a covering and then burst.
  • 3. 9.3 Experience has shown that there are increased deposits at the phase boundary between the gas and liquid spaces when the containers are at standstill or when they are filled, which can detach over time and contaminate the mixture.
  • 4. 9.4 Spraying the inlets onto the boiler wall leads to deposits which can also contaminate the mixture.
  • 5. 9.5 The higher temperature load (especially in the case of solid resin melts) of temperature-sensitive mixing partners due to the long heated supply lines to the tanks leads to deposits in the pipelines. These can also contaminate the mixture.
    In the known methods, the filters have the task of freeing the finished mixture from impurities and protecting the pumps from contamination.
• 10. The cleaning effort in the known methods is due to conversion the ready mix to other mixing partners and because of the larger ver Danger of dirt (see also disadvantage 9) much greater.
• 11. When a resin is added to a solvent, a Mixing gaps are crossed, leading to irreversible clouding can lead.

The object of the invention was to provide a method which has the disadvantages of the known methods.

It has now been found that when using a special apparatus that an Abmi of liquids and does a liquid changeover folds, the disadvantages of the prior art mentioned can be avoided.

The invention relates to a method for mixing polymer resins with solvents and / or other polymer resins with precisely defined proportions in a pumping apparatus, characterized in that two or more components in a temperature range from ambient temperature to 280 ° C, with a residence time of one minute up to 30 minutes, with freely selectable circulation quantities up to 50 m ³ / h and in a pressure range from ambient pressure up to 100 bar and where polymer resins are used which are liquids or solidified melts at ambient temperature, whose mixing temperature is above the boiling temperature (at Ambient pressure) of the solvent (s) or which are difficult to mix with one another or with the solvent (s).

The invention is preferably used on an industrial and industrial scale carried out.

Description of the equipment (for the technical scale)

One embodiment for carrying out the process according to the invention for blending polymer resins with solvents and / or other polymer resins on an industrial and industrial scale is as follows:
In a pumping circuit of low volume with a circulation pump, heat exchanger and two static mixers (Sulzer, Kenics, turbulence plates or other flow converters), the finished product is circulated at a high speed relative to the throughput with a short dwell time. The mixing temperature is set precisely with the heat exchanger installed in the circuit. The poorly miscible liquid A (e.g. melt) is continuously pressed into the circuit via the first static mixer. Because of the magnitude of the circulation flow (finished mixture), the liquid A is very quickly mixed with the finished mixture and tempered to the circulation flow. This avoids direct mixing with liquids B, C and others, which would be considerably more difficult and can lead to clouding, gaps in the mixture, etc.

The required amount of the mixing partner B or a mixture of B, C and other liquids is then added via the second static mixer. The volume of finished mixture continuously displaced from the circuit by the added liquid streams A, B, C and other flows through an overflow valve or pressure control and via a mass flow meter into the filling tank or directly into a tanker truck, settling tank or container. On the basis of this mass flow of ready-mix, the supply of liquid B or the premixed liquid B with C and others is automatically regulated via the second static mixer. The solvent flow of the mixture of B, C and others is also recorded via mass flow meters (see Fig. 1). The desired driving pressure can be set using the overflow valve or the pressure control. You can thus avoid steam bubbles with low-boiling mixing partners.

When carrying out the process according to the invention, polymer resins are used used at ambient temperature liquids or solidified melts whose mixing temperature is above the boiling temperature (at ambient pressure) of the solvent (s) or which is bad with each other or with the Solvent (s) are miscible (i.e. when adding a resin to a pre solvent or other resin is crossed a mixture gap, what can lead to irreversible clouding).

Advantages of the invention

• - The main advantage of the invention is the setting of an exact mixture of a polymer resin (liquid A) with solvents or other polymer resins (liquid B, C, etc.) without having to carry out laboratory analyzes afterwards. A direct detection of the flow of liquid A is not necessary, since it can be determined from the difference between the discharge of the finished mixture and the other mixing partners. It is therefore possible to mix unsuitable substances precisely with this pumping apparatus. The method according to the invention allows the desired composition of the mixture to be adjusted in one go.
  Alternatively, the mixture can also be set via the flow measurement of liquid A, if this can be measured directly. In this case, the discharge quantity need not be recorded (see FIG. 2).
  Furthermore, the viscosity, the refractive index or the density of the finished mixture can also be used to determine the quantities when adding the mixing partners. In these cases, the mixing partners can also record quantities using volume counters. (see Fig. 3).
  In the case of easily miscible liquids, it is also possible to dispense with the static mixers and, if necessary, temperature control of the circulating volume via the heat exchanger. The circulation quantity then has the advantage that it compensates for the control fluctuations (see FIG. 4).
  Another advantage of the invention is that a direct Ver mixing of the polymer resin (liquid A) with the liquids B, C and others, which may lead to clouding, gaps in the mixture u. Ä. can lead, is avoided.
• - Because of the small liquid content, the apparatus requires only a small amount of cleaning when changing products. This enables a flexible driving style of even the smallest lots. The apparatus can be easily converted to another finished mixture at the end of the production of the finished mixture. Through clever piping, the pump circuit can empty and drain independently via a vent valve installed at the top, otherwise the liquid content can be largely removed with the circuit pump by closing the pump valve. The remaining amount can then be emptied with inert gas via the vent valve. One way to start is to fill the pump circuit from a residual drum with the desired ready mix: this means that even small quantities of intermediate runs can be avoided entirely.
  Sometimes the solvent can be changed directly (without cleaning or emptying), provided a low content of external solvent is acceptable: if the batch size is very large compared to the circulating content (e.g. 5000 kg vs. 50 kg) and finds only a change of the solvent (liquid B, C, etc.) instead of cleaning can generally be dispensed with.
• - A simpler structure of the apparatus compared to an apparatus for Ab mix in stirred tanks as they only consist of one heat exchanger, tube lines with static mixers, a circulation pump and if necessary a filling boiler.
• - A lower temperature load for temperature-sensitive mixing partners. Since the hold-up of the transfer pump assembly is low (e.g. 0.05 m ³ ), the dwell time for temperature-sensitive, hot-conveyed mixing components can be kept very short (e.g. 2 minutes) with the advantage that this is immediate can be cooled in the circulation line. Even in the event that a high mixing temperature is required in the pumping circuit, the finished mixture can be cooled down immediately by an additional heat exchanger in the discharge line. The quality of the ready mix can thus be improved. This is documented e.g. B. in polyisocyanate coating resins by a slight increase in viscosity, yellowing and monomer elimination.
• - The equipment is contaminated by deposits during pumping packaging much smaller than with conventional processes. Consequently the filtering effort in the pumping assembly is significantly reduced ed.
• - A lower cleaning effort, which is dirty when the Umpumpkon packaging must be operated.  
• - There can be a single-phase liquid flow with a defined flow pattern (without vapor bubble formation with low-boiling mixing partners) over the Pressure can be set on the overflow valve or on the pressure control.

In the method according to the invention for adjusting a mixture of liquids with precisely defined proportions, polymer resins are preferably used, optionally in solvents, preferably polyisocyanates, optionally in Solvents used.

Aliphatic polyisocyanates are preferably used as polyisocyanates, e.g. B. aliphatic polyisocyanates derived from hexamethylene diisocyanate (HDI), Derive isophorone diisocyanate (IPDI). Mixtures can also be used according to the invention the polymer resins, e.g. B. mixtures of polyisocyanates can be used derived from HDI and / or IPDI.

Examples

The following examples show the advantages according to the invention using Polyisocyanate coating resins.

The polyisocyanates used in the examples are prepared as described in the patent literature:
Polyisocyanate A)
As described in EP-A 003765, Example 1, 1000 kg of isophorone diisocyanate (IPDI) are trimerized on an industrial scale until an NCO content of the crude solution of 30.6% is reached. By thin-layer distillation at 170 ° C / 1 mbar, monomeric IPDI is distilled off, and a polyisocyanate melt of the IPDI trimer is obtained, which at room temperature forms a solid resin with an NCO content of 16.7% and a monomeric IPDI content of 0.1 % stiffens.
Polyisocyanate B)
As described in EP-A 377177, Example 2, an HDI uretdione / isocyanurate polyisocyanate is produced with the following characteristics: 21.6% NCO content, viscosity 180 mPas / 23 ° C, monomeric HDI 0.3%.
Polyisocyanate C)
As described in EP-B 277353, Example 3, an HDI biuret polyisocyanate is produced with the following characteristics: 21.9% NCO content, viscosity 10100 mPas / 23 ° C, monomeric HDI 0.2%

example 1 Mixing a solid resin with a solvent

Preparation of a 70% solution of polyisocyanate A in solvent naphta 100.
Travel information:
300 kg / h solid resin melt of polyisocyanate A at 140 ° C, 190 kg / h solvent naphta at 30 ° C,
490 kg / h 70% solution of the IPDI trimer,
Circulation volume in pump transfer assembly (UPK): 4000 kg / h at 90 ° C and 3 bar.
The hold-up of the transfer pump assembly is 50 l, so the dwell time is 6.1 minutes

Example 2 Mixing a solid resin with a liquid resin

A polyisocyanate mixture is produced from 1 part by weight of polyisocyanate A and 2 parts by weight of polyisocyanate B.
Travel information:
300 kg / h solid resin melt of polyisocyanate A at 140 ° C, 600 kg / h liquid resin of polyisocyanate B at 50 ° C
900 kg / h polyisocyanate mixture
Circulation volume in UPK: 4000 kg / h at 90 ° C and 3 bar.
With a hold-up of the pump transfer assembly of 50 l, the dwell time is 3.3 minutes.

Example 3 Mixing a liquid resin with a solvent

Preparation of a 75% solution of polyisocyanate C in a mixture of 1-methoxypropylacetate-2 / xylene = 1/1.
Travel information:
1200 kg / h polyisocyanate C at 135 ° C,
200 kg / h 1-methoxypropylacetate-2 at 30 ° C,
200 kg / h xylene at 30 ° C
1600 kg / h 75% solution of polyisocyanate C
Circulation volume in UPK: 4000 kg / h at 50 ° C and 3 bar.
With a hold-up of the transfer pump assembly of 50 l, the dwell time is 1.9 minutes

Claims (4)

1. Process for blending polymer resins with solvents and / or other polymer resins with precisely defined proportions on a technical and industrial scale in a pumping apparatus, characterized in that two or more components in a temperature range from ambient temperature to 280 ° C, with a dwell time from one minute to 30 minutes, with freely selectable circulation quantities up to 50 m ³ / h and in a pressure range from ambient pressure to 100 bar, and polymer resins are used which are liquids or solidified melts at ambient temperature, the mixing temperature of which above Boiling temperature (at ambient pressure) of the solvent (s) is or which are difficult to mix with each other or with the solvent (s). 2. The method according to claim 1, characterized in that as polymer resins Polyisocyanates are used. 3. The method according to claim 1 and 2, characterized in that as Polymer resins aliphatic polyisocyanates are used. 4. The method according to claims 1 to 3, characterized in that as Polymer resins are used, which differ from HDI and / or Derive IPDI.