DE3009812C2 - Process for making beads from polymethacrylate - Google Patents

Description

The invention relates to a process for the production of. · Beads of polymethacrylate in a liquid, in particular water, optionally suspension stabilizers or distributing agents as additives contains.

For the production of Ferlpolymerisat it is known to bring the monomer into hot water in large stirred kettles and stir it into small droplets smashed, after which the droplets polymerize into small pearls. The water contains suspension stabilizers or spreading agents by their surface tension to prevent the droplets from recombining with others. The ones that already exist Droplets are continually broken up again by the stirrer and often forcefully with other droplets reconnected. This smashing and reconnecting by the stirrer is disadvantageous when the Monomers begin to polymerize because then the droplets due to the mechanical action of the Stirrers to stick together and begin to clump. This effect can be limited by a certain Design of the stirrer as well as higher and further additives in the water avoided will. This additional effort is expensive, and this process can also produce a bead polymer cannot be produced continuously.

The object of the invention is to improve a Verlahren of the type mentioned in such a way that with little Effort, a bead polymer of uniform size and shape can be produced continuously and inexpensively is

According to the invention, this object is achieved in that methacrylic acid esters are introduced into the liquid in droplets is injected and the droplets during their

ίο Left to polymerize and remain in the liquid the pearls are then removed from the liquid.

Since in the method according to the invention, the size and shape of the pearls directly depend on the size and shape depends on the droplets introduced, this can be determined and controlled very precisely. The apparatus Effort is low, and the production is carried out continuously, so that there is little operator effort and automation becomes possible. There is no stirrer action, and so does the injected droplet size will be maintained. It is preferably proposed that the monomer be introduced into the liquid before it is introduced was partially polymerized.

The monomer or the resin can be introduced into the liquid from below, so that the droplets you. oh the liquid rise through it to the top.

In order to prevent the monomer from forming a thread and to make it easier for the droplets to tear off, you can the nozzles vibrate in particular at a certain frequency in the ultrasound range.

It is preferably proposed that, depending on the specific gravity of the liquid and the pearls, the pearls be removed continuously in the lower or upper area of the liquid. This can be done by suction or by a conveyor belt. After that, additives in the water, such as suspension stabilizers, can be added from the pearls or spreading agent, washed off and then the beads dried.

The monomer can contain water-insoluble additives such as dyes, pigments, propellants, spheres and / or pearls, depending on the intended use. The liquid in the container can also be under overpressure, which prevents evaporation or driving of the additives contained in the monomer. To generate or accelerate the polymerization or hardening, the liquid, in particular the water, can be heated.

The droplet size can be determined by the amount of monomer or resin added via a metering device to be determined. This is a very

so exact size determination of the pearls possible. In particular For this purpose, an equally large inflow per unit of time to the outlet openings or nozzles can take place. An exact as well as rapid formation of droplets in the liquid is achieved in that the monomer or the resin is fed to the outlet openings or the nozzles in a pulsating manner. Alternatively or additionally can also be determined by the frequency of the vibrations of the nozzles od'jr outlet openings and / or the pulsating monomers or resin, the droplet size can be determined.

An at least initial rise of the droplets in the liquid is achieved in that the monomer or the resin in a specific heavier liquid than the Mon-j-ner or the Harz in particular

it will be injected from below. The liquid can be specifically lighter than the polymer or the resin after hardening, so that the droplets in the liquid first rise and then sink. In order to

polymerize or harden the droplets both while rising and sinking into the liquid. A slowing down of the rate of rise and / or fall of the droplets in the liquid is achieved in that the droplets and pearls rise in a countercurrent of the liquid and / or let it sink. The flow velocity of the countercurrent can be determined by the droplets and / or pearls are changed. This can in particular result in a change in the flow rate be achieved that the cross section of the container during the rise and / or fall of the Droplets and pearls changes.

It is preferably proposed that as the hardening / polymerization of the droplets increases or pearls let the flow rate grow. This will, inter alia. the rate of descent of the Droplets or pearls reduced, so that the container has small dimensions. Particularly small container dimensions are achieved in that the droplets or pearls in an ascending and a subsequent sinking flow are hardened or polymerized.

It is also proposed that to generate or accelerate the hardening or polymerization UV rays penetrate the liquid. The UV radiation penetrates into the core of the droplets and pearls one. so that particularly evenly hardening and tension-free pearls are created.

Hollow beads can be achieved by the fact that during the exit of the droplet from the outlet opening or nozzle a gas is forced into the interior of the droplet through a nozzle.

A further reduction in the rate of rise and / or fall of the droplets and pearls, and thus a further reduction in the container dimensions is achieved by using such a liquid which has a higher viscosity (thicker) than water. The liquid can be water be that has viscosity-increasing additives.

Preferably, in a process for the production of beads from polymethyl acrylate in a liquid, in particular water, optionally suspension stabilizers or distributing agents as additives contains, suggested that methacrylic acid ester and a different monomer through the outlet openings or nozzles are printed in each droplet with one monomer surrounding the other, the droplets are allowed to polymerize while they remain in the liquid and the pearls afterwards removed from the liquid.

As a result, pearls with a wide variety of optical, aesthetic and mechanical properties achievable. Not only are color effects with different Coloring of the core and shell can be achieved, but the core can, for example, also be made harder as the shell, whereby elastic or kneadable masses can be achieved.

A structurally particularly simple one and a minor one The device for performing the method, which requires effort, is characterized by a the liquid-containing container with arranged in particular on the container bottom or its vicinity Orifices or nozzles connected to at least one line supplying the monomer or the resin are connected. A sufficiently large path of the droplets and pearls in the container can thereby be achieved that the container has a greater height than width.

A decrease in the flow rate of the liquid within the container during the Rising of the droplets is achieved in that the container cross-section increases towards the top. For education the path in the container for the droplets and pearls during their sinking can be at the Top of the container be connected to a downward leading container part. During the one in front of it first container part is arranged vertically in order to rise without contact from the container walls to enable the droplets and thus deformations can be prevented, the second container part be arranged at an angle, since in the sinking stage the droplets or pearls have a harder consistency and are therefore no longer so easily deformable.

An increase in the flow velocity within the second part of the container is achieved by that the cross-section of the downwardly leading container part is reduced towards the bottom. Preferably will suggested that the downwardly leading container part at the bottom has an outlet opening for the pearls owns. In this case, the outlet opening can have a valve in order to allow for intermittent or regular discharge of the pearls without too much liquid escaping. For this purpose, it is also proposed that the Outlet opening leads to a collecting container for the pearls.

A reduction in the container dimensions can also be achieved in that the container or at least one container part is helical. A continuous flow cycle is achieved in that the part or end of the container at which the monomer or resin is introduced is connected to the part or end of the container at which the beads are brought out by a conduit through which the liquid pumpable.
To produce pearls with different properties of the shell compared to the core in terms of consistency, maverial type or color, it is proposed that the outlet openings or nozzles have a central opening for a first type of monomer or resin and a ring opening coaxially surrounding the central opening for one of the first has different second monomer or resin type.

Embodiments of the method according to the invention as well as devices shown schematically for the exemplary implementation of the method are described in more detail below. It shows

F i g. 1 a container with counterflow:
F i g. 2 a container without counterflow with helical sections;

3 shows a container which is only partially filled with liquid, with the pearls being removed by exiting them from the liquid surface; and

F i g. 4 forming the lower part of a container with two coaxially nested outlet openings (Nozzles) pipes.

An offset with peroxides methacrylate is printed through the outlet openings or nozzles 22, 20a, 4b of a (nozzles) head 10, 12a, 3b in 80 to 90 ⁰ C hot water 17, 18a, 166 of the nozzle head vibrates by an oscillating generator 9, 11a, 5b in the ultrasonic range, ie above 20,000 Hz. As a result, the monomer exits the hot water in droplets without thread formation. Additionally or alternatively, the ester is pulsed through the outlet openings

Dosing device 11,13a, 2b supplied.

The horizontally arranged nozzle head emerges with vertical nozzle openings partly or wholly from the bottom into the water, which is surrounded by a pressure vessel 1, 2,1 a, 5a, 6b, Sb and is under a pressure of 4 -8 bar. The internal pressure in the container is generated by compressed air lines 38, 36a, 24b via pressure reducing devices 25, 27, 28, 24a, 25a, 26a.

The B ^ container height is chosen so that the droplets there is sufficient time during the ascent and subsequent descent to polymerize completely. The rate of rise of the droplets decreases with increasing degree of polymerization up to one upper turning point, from where the droplets or pearls begin to sink, with a further degree of polymerization the rate of descent increases. The speed of the polymerization can be determined by the proportion the peroxides and can be determined by the level of the water temperature.

The pearls that have reached the top of the container can also be suctioned off or removed via a conveyor belt will. Then these are separated from the water by a sieve and after rinsing off those in the water Dried additives on tapes.

The monomers can contain water-insoluble additives such as dyes, pigments, propellants, beads or small beads should be added, which are located in the polymethacrylate beads after polymerisation.

In the case of the FIG. 1, the liquid in the container flows from a in the vicinity of the pearl outlet the nozzles 22. so that the beads against this flow of liquid rise and then sink against the flow of liquid. The connection between these two Reservoir locations happens through a line 39, in which a circulating pump 15 and a liquid storage container 13 are arranged.

Before the hardened beads 21 emerge from the container part 3, they are placed in a collecting container 4 and then drained through a drain valve 32 into a collecting container 5. From this container 5 the pearls are placed on a discharge valve 33 on a conveyor belt 8, through which the pearls under a Washing unit 6 and then passed under a drying unit 7 in order to then be transferred to a filling station 16 to get. The container 5 acts like a lock to maintain the overpressure in the container 1, 2, 3 to be able to. For this purpose, the container 5 is via a line and a storage container 14 which is filled with liquid and is connected to a compressed air line 38 via a pressure reducing device 28. (The overpressure prevents the formation of bubbles and accelerates polymerisation or hardening.)

The monomer fed to the metering unit 11 is also fed to the nozzle head 10 under pressure, wherein the storage container 12 provided for the monomer via a pressure reducing device 25 with the line 38 is connected It is ensured that the monomer is under a higher pressure than the Liquid pressure at the level of the nozzles 22. The monomer droplets emerging from the nozzles 22 rise in the opposite direction the flow velocity vertically high and thereby reduce their rate of climb, as with increasing polymerisation the specific gravity of these drops increases. The drops are made by the upper container wall deflected to a container part 2, which is above a vertical curing tube 3 is arranged, in which the drops sink, since they now have a higher specific weight than that Liquid 17. The speed of fall increases in the hardening tube 3 until the pearls that have formed in the meantime have reached the collecting container 4. The increase in speed of ascending and descending the droplets or pearls can be partially or even completely canceled by the fact that the speed the liquid flow within the container changes accordingly due to a continuous

borrowed change of the container cross-sections changes. This is where the highest flow velocity occurs for the drops or pearls opposed to where they rise or fall most rapidly, so that opposed to relative movement the actual movement of the droplets and pearls remains about the same.

The exemplary embodiment shown in FIG. 2 differs from that according to FIG. 1 essentially only in that an inclined guide wall 37a is arranged in the upper region of the hardening tube la. which guides the drops or pearls to the sinking vessel 5a. Below the sinking vessel are two helical tubes through which the pearls pass. There is no countercurrent in this container.
In the embodiment shown in FIG. 3, only the curing tube 6 is filled with liquid. The pearls are pressed out of the liquid surface by the pearls below and roll through the overflow vessel Sb into a collecting vessel 9b, from which they are removed via the lock 106 with valves 25b and 266.

In Fig. 4 is only the lower part of a curing container 10c, into which a double nozzle extends from below. This nozzle consists of an inner one Tube 12c (inner cannula), which is coaxial with an outer cannula lic is surrounded so that a circular outlet opening is surrounded by an annular outlet opening is surrounded coaxially. As different monomers are fed to these two tubes, they form Droplets with a core 9c whose material is from another The consistency, appearance or texture is as a shell 8c surrounding this core. After the polymerization or hardening results in pearls with a core that differs from that of the shell. The droplet size can be determined by the pulsating monomer or resin.

Examples where the liquid is not water.

example 1

In 10 parts by weight of MMA there are 20 parts by weight PMMA dissolved in the form of pearl polymer.

The result is an acrylate batch with a viscosity of approx. 200 cp. This batch is cooled to approx. 3-5 ° C.
1 part by weight of acethylcyclohexanesulfonyl peroxide - ACSP - is added to this batch with constant stirring. This batch is placed in a pressure vessel which is cooled to 3 ° C. and is pressurized to a bar
Pentane is introduced into the polymerization system

and is under approx. 2 bar overpressure. The acrylic approach is now via a metering pump that pumps 1 ecm per stroke, via needles with a diameter of 0.5 mm in the liquor solution is pressed. The result is droplets with a diameter of approx. 3–4 mm. These Droplets polymerize in the 35 degree warm pentane liquor solution. After about 30 minutes they are Droplets polymerized to a spherical polymer about 3 mm in size and w; rden

Taken from the bead polymerisation plant via the lock.

Example 2

A batch consisting of 100 parts by weight of poly-400 ethylene glycol dimethacrylate is mixed with 2 parts by weight of Irgacure 162 (1-hydroxycyclohexylphenyl ketone) of the company Ciba Geigy.

The viscosity is approx. 400 cp. This acrylic approach is placed in a pressure vessel and 1 bar overpressure is applied

Trichlorotrifluoroethane with a temperature of 25 degrees is filled in the polymerization system. Above a metering pump with a stroke of 1 ecm, droplets 3–4 mm in size are introduced into the liquor solution via 50 needles injected.

The droplets are polymerized in the float via UV exposure (Philips fluorescent tube P 12).

The trichlorotrifluoroethane liquor is under an overpressure of approx. 2 bar. After about 25 minutes they are Droplets 3–4 mm in size are polymerized to form an acrylic glass sphere and are then passed through a sluice in the bead polymerization system taken.

Example 3

To claim 24

Examples of the use of various monomers
Example 4

10 neck 1 cup is located.

The polymerization takes place at 40 degrees and is completed in about 30 minutes. Depending on the injection speed result in smaller or larger droplets or smaller or larger bead polymers with a softer one Core.

Example 5

n-Butyiacrylate of the 2nd batch from Example 4 is replaced by ethylhexyl methacrylate. With the same process technology, pearl polymers with external hard shell and a soft core.

15th

20th

25th

100 parts by weight of triethylene glycol dimethacrylate (TEDMA) are combined with one part by weight of CHPC (dicyclohexyl peroxide carbonate) and one part by weight of t-butyl per-2-ethylhexanoate.

This approach is placed in a pressure vessel and pressurized with approx. 1 bar overpressure. About the connected The batch is fed into the liquor bead polymerization system using a metering pump pumped. Dosing stroke approx. 1 cm, 50 injection needles, diameter 0.5, droplet size 3–4 mm in diameter. In the peripheral system A silicone oil M 100 Baysilon® (liquid, water-clear polydimethylsiloxane) is given. the The liquor system is placed under 2 bar overpressure and at a temperature in the ascent phase of 40 degrees brought to 100 degrees in the descent phase. The acrylic droplets polymerize in about 35 minutes to a solid polymer and are made using the lock technology taken from the bead polymerization plant.

45

50

Approach for the harder outer shell 100 parts by weight MMA, 30 parts by weight PMMA, 1% ACSP Acethylcyclohexanesulfonyl peroxide, 1 part by weight of t-butyl per-2-ethylhecanoate. This batch is placed in a pressure vessel and placed under approx. 5 bar overpressure.

The following is entered into a second pressure vessel:
100 parts by weight of n-butyl acrylate, 2 parts by weight of ω acetylcyclohexanesulfonyl peroxide. In the polymerization system is an aqueous liquor with 2 bar excess pressure and a temperature of 40 degrees. Approach 1 is introduced into the liquor solution via the outer injection needle via a FeinstreguHerventil, over the inner injection needle, approach 2 is also introduced via a Feinstreguiierventii so that, when the droplets are formed, approach 2 in the droplet in the 4 sheet drawings

Claims (1)

Patent claims: 1. Process for the production of beads from polymethacrylate in a liquid, especially water, which optionally contains suspension stabilizers or distributing agents as additives, thereby characterized in that methacrylic acid ester (18) is injected into the liquid in droplets and allowing the droplets (19) to polymerize while remaining in the liquid and the beads then removed from the liquid. 2. The method according to claim 1, characterized in that the monomer before being introduced into the liquid has been polymerized. 3. The method according to claim 1 or 2, characterized in that the monomer (18) from below in the liquid (17) is introduced. 4. The method according to any one of claims 1 to 3, characterized in that the outlet openings (22) or nozzles for the monomer with a certain frequency, preferably in the range of Ultrasound, vibrate. 5. The method according to any one of claims 1 to 4, characterized in that depending on the specific Weight of the liquid (17) and the pearls (21) Pearls in the lower or upper area of the liquid (17) are continuously removed. 6. The method according to claim 5, characterized in that the removal of the beads (21) by Suction or: done by a conveyor belt. 7. The method according to claim 5 or 6, characterized in that that the additives in the liquid are washed off the pearls (2!) and then the pearls are dried. vcriBiircn nscii one scii an uer i-insprucnc 1 uis /, characterized in that the monomer (18) contains water-insoluble additives. 9. The method according to claim 8, characterized in that the additives dyes, pigments, Propellants, beads and / or beads. 10. The method according to any one of claims 1 to 9, characterized in that the liquid (17) in the Container is under an overpressure, which evaporates or expels the contained in the monomer Prevents additives. 11. The method according to any one of claims 1 to 10, characterized in that the liquid (17) is heated. 12. The method according to any one of claims 1 to 11, characterized in that the droplet size is determined by the added amount of the monomer (18) via a metering device (11). 13. The method according to any one of claims 1 to 12, characterized in that the same to achieve large droplets (19) an equally large inflow of monomers (18) per unit of time to the outlet openings (22) or nozzles. 14. The method according to any one of claims 1 to 13, characterized in that the monomer (18) the outlet openings (22) or the nozzles is supplied in a pulsating manner. 15. The method according to any one of claims 1 to 14, characterized in that by the frequency the vibrations of the nozzles or outlet openings (22) and / or the pulsating monomer (18) the droplet size is determined. 16. The method according to any one of claims 1 to 15. 35 40 45 50 55 60 65, characterized in that the monomer (18) is injected into a liquid (17) that is specifically heavier than the monomer. 17. The method according to claim 16, characterized in that that the liquid (17) is specifically lighter than the polymer after curing. 18. The method according to any one of claims 1 to 17, characterized in that the droplets (19) and pearls (21) during the rising and falling in the Liquid to be polymerized. 19. The method according to any one of claims 1 to! 8, characterized in that the droplets (19) and pearls (21) rise and / or sink in a countercurrent to the liquid (17) 20. The method according to claim 19, characterized in that the flow rate of the Countercurrent via the path of the droplets (19) and / or pearls (21) is changed. 21. The method according to claim 20, characterized in that with increasing polymerization of the droplets or peries (21) the flow velocity lets grow 22. The method according to any one of claims 1 to 21, characterized in that the droplets (19) or pearls (21) harden in an ascending flow and a subsequent falling flow left or polymerized. 23. The method according to any one of claims 1 to 22, characterized in that for generating or Acceleration of the polymerization, the liquid (17) is penetrated by UV rays. 24. The method according to any one of claims 1 to 23, characterized in that during the exit of the droplet from the outlet opening or nozzle into the interior of the droplet by means of a nozzle a gas is pressed in. 25. The method according to any one of claims 1 to 24, characterized in that such a liquid (17) is used, which has a higher viscosity (thicker) than water. 26. The method according to claim 25, characterized in that the liquid (17) is water that the Has viscosity increasing additives. 27. A method for producing beads from polymethacrylate in a liquid, in particular water, which optionally contains suspension stabilizers or distributing agents as additives, characterized in that methacrylic acid ester (5c) and a different monomer (6c) through the outlet openings (22) or nozzles in squeezing each droplet, one monomer surrounding the other, allowing the droplets (19) to polymerize while remaining in the liquid, and then removing the beads from the liquid. 28. Apparatus for performing the method according to any one of claims 1 to 27, by a die Liquid-containing container (1, 2, 3) with, in particular, on the underside of the container or its vicinity arranged openings (22) or nozzles, which are connected to at least one of the monomer (18) feeding Line are connected. 29. The device according to claim 28, characterized in that that the container (1, 2,3) has a greater height than width. 30. Apparatus according to claim 28 or 29, characterized in that the Behällerquerschniit increases towards the top. 31. Device according to one of claims 28 to 30, characterized in that the cross section of a downward leading container part (3) is reduced towards the bottom. 32. Apparatus according to claim 31, characterized in that the downwardly leading container part (3) has an outlet opening for the pearls (21) on the underside 33. Apparatus according to claim 32, characterized in that the outlet opening is a valve (32) having 34. Apparatus according to claim 32 or 33, characterized in that the outlet opening to one Collecting container (5) for the pearls (21) leads 35. Device according to one of claims 28 to 34, characterized in that the container or at least one container part (38a) is helical 36. Device according to one of claims 28 to 35, characterized in that the part or end of the container at which the monomer (18) is introduced is, with the part or end of the container where the beads (21) are brought out, over a Line (39) is connected through which the liquid (17) can be pumped 37. Device according to one of claims 28 to 36, characterized in that the outlet openings (lic, 12c ^ or nozzles have a central opening for a first type of monomer (5c) and a ring opening coaxially surrounding the central opening for a second type of monomer (6c) different from the first. 38. Device according to one of claims 28 to 37, characterized in that the container (6b) is only partially filled with liquid and the upper horizontal edge (28Z ^ of an inclined or approximately vertical surface (29b) over which the pearls ends at the level of the liquid level (27b) inside the container (18 /?) Emerge from the liquid (t6b) .