Process for the production of thermoplastic moulding compounds

Abstract

The invention relates to a process for the production of thermoplastic moulding compounds, in particular for the production of acrylonitrile-butadiene-styrene (ABS), wherein at least a first reagent (11) and a second reagent (12) of the thermoplastic moulding compounds are fed to a loop conduit (29) which comprises a static mixer (36), wherein the reagents (11, 12) are pressed in loops through the loop conduit (29) and passing the static mixer (36), whereby the reagents (11, 12) are dispersed to form a dispersion (15) in the static mixer (36). The invention also relates to a thermoplastic moulding compound that is produced by the inventive process.

Claims

1. A process for the production of acrylonitrile-butadiene-styrene (ABS), comprising the following steps: a. adding at least one solvent to a first reagent (11) that contains or consists of styrene-acrylonitrile copolymer (SAN) and a second reagent (12) that contains or consists of rubber, b. mixing the at least one solvent, the first reagent (11) and the second reagent (12) in a mixing vessel (50) to form a premix, c. feeding the premix to a loop conduit (29) which comprises at least one static mixer (36), d. pressing the reagents (11, 12) in loops through the loop conduit (29), and e. dispersing the reagents (11, 12) to form a dispersion (15) in the static mixer (36), and wherein the premix is pressed through the static mixer (36) back to a mixing vessel (50).

2. The process according to claim 1, comprising a step of feeding the first reagent (11) styrene-acrylonitrile copolymer (SAN) to the loop conduit (29) in a molten state.

3. The process according to claim 1, comprising a step of heating the first reagent (11), which contains or consists of styrene-acrylonitrile copolymer (SAN), above melting temperature.

4. The process according to claim 1, comprising a step of feeding the second reagent (12), which contains or consists of rubber, to the loop conduit (29) as relatively fine powder.

5. The process according to claim 1, comprising a step of feeding the second reagent (12) rubber to the loop conduit (29) in a molten state.

6. The process according to claim 1, comprising a step of feeding the premix directly into the loop conduit (29).

7. The process according to claim 1, comprising a step of storing the premix temporarily and later feeding the premix to the loop conduit (29).

8. The process according to claim 1, comprising a step of pressing the reagents (11, 12) in loops through the loop conduit (29) from 1 time to 100 times.

9. The process according to claim 1, comprising a step of pressing the reagents (11, 12) in loops through the loop conduit (29) by a first pump.

10. The process according to claim 1, comprising a step of dispersing the reagents (11, 12) at a temperature at a range of 160 C. to 250 C.

11. The process according to claim 1, comprising a step of processing the dispersion (15) further to form acrylonitrile-butadiene-styrene (ABS).

12. The process according to claim 1, further comprising the steps of: a. feeding the premix to an inlet (42) of a first pump (10) while an outgoing valve (67) for taking the dispersion (15) out of the loop conduit (29) is closed, b. forwarding the premix in loops through the loop conduit (29) toward the static mixer (36) by of the first pump (10), c. opening the outgoing valve (67) after a certain number of loops within the loop conduit (29), d. pressing out the dispersion (15) of the loop conduit (29) and delivering the dispersion (15) through the outgoing valve (67) by the first pump (10).

13. The process according to claim 12, wherein the outgoing valve (67) is arranged at a branch downstream of the mixing vessel (50) and upstream of the first pump (10).

Description

(1) In the drawings:

(2) FIG. 1 shows a schematic drawing of a first embodiment of a system for the production of moulding compounds.

(3) FIG. 2 shows a schematic drawing of a second embodiment of a system for the production of moulding compounds.

(4) In FIG. 1, a schematic drawing of a first embodiment of a system for the production of moulding compounds, in particular for the production of acrylonitrile-butadiene-styrene (ABS), is shown.

(5) The system comprises a loop conduit 29 that contains several static mixers 36. The static mixers 36 are implemented as static mixing sections containing one or multiple static mixing elements. In this embodiment, the system comprises two static mixers 36. However, systems with only one static mixer 36 or with more than two static mixers 36 are also feasible. In this embodiment, the static mixers 36 are arranged in series. It is also possible to arrange several static mixers 36 in parallel.

(6) The loop conduit 29 of the system also contains a first pump 10. The first pump 10 has an inlet 42 and an outlet 44. Reagents 11, 12 can be fed to the inlet 42 of the first pump 10 and are pressed out through the outlet 44 of the first pump 10. In this embodiment, the first pump 10 is of the gear pump type. But also other kinds of pumps are useable within the loop conduit 29 of the system.

(7) In this embodiment, the loop conduit 29 of the system also contains a second pump 70. The second pump 70 is arranged between the two static mixers 36. In this embodiment, the second pump 70 is of the gear pump type and is assembled like the first pump 10. But also other kinds of pumps are useable within the loop conduit 29 of the system. Furthermore, the system contains a third pump 80. The third pump 80 is arranged at the entrance of the loop conduit 29. In this embodiment, the third pump 80 is of the gear pump type and is assembled like the first pump 10. But also other kinds of pumps are useable within system.

(8) For the production of acrylonitrile-butadiene-styrene (ABS), in particular a first reagent 11 and a second reagent 12 are fed to the loop conduit 29, wherein in particular the first reagent 11 is styrene-acrylonitrile-copolymer (SAN), and the second reagent 12 is rubber, e.g. polybutadiene-rubber.

(9) The second reagent 12 rubber is specifically a SAN grafted elastomer, with the elastomer preferably being a polybutadiene based rubber.

(10) Hence, the second reagent can be a SAN grafted rubber. The reagents 11, 12 are fed to the loop conduit 29 by means of the third pump 80 that is arranged at the entrance of the loop conduit 29.

(11) The process is also useable for the production of different thermoplastic moulding compounds. For example, for the production of acrylonitrile styrene acrylate (ASA), in particular the first reagent 11 is styrene-acrylonitrile-copolymer (SAN), and the second reagent 12 is a SAN grafted acrylate based rubber.

(12) After feeding the reagents 11, 12 to the loop conduit 29, the first reagent 11 and the second reagent 12 are then pressed in loops through the loop conduit 29, in particular through the static mixers 36, by means of the first pump 10. Within such a loop, the first reagent 11 and the second reagent 12 are pressed through the outlet 44 of the first pump 10 towards the static mixers 36, and passing the static mixers 36 towards the inlet 42 of the first pump 10.

(13) The second pump 70 supports the movement of the reagents 11, 12 through the loop conduit 29. Within each static mixer 36, respectively within each static mixing section, there is a pressure drop during operation. The second pump 70 increases pressure within the loop conduit 29 downstream of such a static mixer 36.

(14) In particular within the static mixers 36, the reagents 11, 12 are dispersed to form dispersion 15. After a certain number of loops within the loop conduit 29, the dispersion 15 can be taken out of the loop conduit 29. Afterwards, the resultant dispersion 15 is further processable to form moulding compounds, in particular to form acrylonitrile-butadiene-styrene (ABS).

(15) Upstream of the loop conduit 29, an incoming valve that is not shown here is provided. When said incoming valve is open, the reagents 11, 12 can be fed through said incoming valve to the loop conduit 29 with the static mixers 36. Downstream of the loop conduit 29, an outgoing valve that is not shown here is provided. When said outgoing valve is open, the resultant dispersion 15 can be fed through said outgoing valve out of the loop circuit 29.

(16) Within a process for the production of moulding compounds, in particular for the production of acrylonitrile-butadiene-styrene (ABS), the first reagent 11 and the second reagent 12 are fed to the loop conduit 29 while the incoming valve is open and the outgoing valve is closed. The reagents 11, 12 are pressed through the loop conduit 29, in particular through the static mixers 36, by means of the first pump 10.

(17) Within such a loop through the loop conduit 29 and passing the static mixers 36, a partition of the reagents 11, 12 is dispersed to a dispersion 15. Within every new loop, some more of the reagents 11, 12 are dispersed to the dispersion 15. The resultant dispersion 15 also travels around within the loop conduit 29 and passing the static mixers 36. Thereby, the resultant dispersion 15 is also homogenized.

(18) After a certain number of loops within the loop conduit 29, the reagents 11, 12 are dispersed, at least almost, completely. That means, only the dispersion 15 that is also homogenized, then travels around within the loop conduit 29, still forwarded by the first pump 10.

(19) Then, the outgoing valve is opened and the incoming valve is closed. The dispersion 15 is then pressed out of the loop conduit 29 and through the outgoing valve by means of the first pump 10. When the dispersion 15 has left the loop conduit 29, the outgoing valve is closed and the incoming valve is opened again. While the incoming valve is open, the first reagent 11 and the second reagent 12 are fed to the loop conduit 29, again, and the first pump 10 forwards the reagents 11, 12 in loops through the loop conduit 29.

(20) Within an alternative, continuous process for the production of moulding compounds, in particular for the production of acrylonitrile-butadiene-styrene (ABS), the incoming valve and the outgoing valve are open and remain open during the production process. The first reagent 11 and the second reagent 12 are fed to the loop conduit 29 and the first pump 10 forwards the reagents 11, 12 through the loop conduit 29, in particular through the static mixers 36.

(21) Within said alternative, continuous process, a partition of the reagents 11, 12 is dispersed to a dispersion 15 when passing the static mixers 36. A part of the reagents 11, 12 and the dispersion 15 remain within the loop conduit 29 and are pressed to the inlet 42 of the first pump 10. Said part of the reagents 11, 12 and the dispersion 15 hence travel around within the loop conduit 29 in a loop.

(22) Thereby the reagents 11, 12 are dispersed in the static mixers 36 to the dispersion 15, and the resultant dispersion 15 is homogenized. A part of the resultant dispersion 15 is pressed out of the loop conduit 29 towards the outgoing valve.

(23) Subsequently, further processing, in particular dewatering, of the resultant dispersion 15 then takes place to give moulding compounds, in particular to provide acrylonitrile-butadiene-styrene copolymer compositions (ABS).

(24) In FIG. 2, a schematic drawing of a second embodiment of a system for the production of moulding compounds, in particular for the production of acrylonitrile-butadiene-styrene (ABS), is shown.

(25) Additionally to the first pump 10 and the static mixer 36, the loop conduit 29 further comprises a mixing vessel 50. The mixing vessel 50 has a beater 52 which is drivable by an electric motor 62. In this embodiment, only one static mixer 36 is provided. However, several static mixers 36, arranged in series as well as in parallel, can be used, as described above.

(26) The loop conduit 29 may further comprise a second pump 70 arranged within the loop conduit 29 downstream of the static mixer 36 and upstream of the mixing vessel 50. In this case, the second pump 70 supports the movement of the reagents 11, 12 through the loop conduit 29 by increasing pressure within the loop conduit 29 downstream of the static mixer 36.

(27) Furthermore, the system may contain a third pump 80 arranged at the entrance of the vessel 50. In this case, the reagents 11, 12 are fed to the vessel 50 by means of the third pump 80.

(28) Also, an outgoing valve 67 is provided for taking the dispersion 15 out of the loop conduit 29. In this embodiment, the outgoing valve 67 is arranged at a branch downstream of the mixing vessel 50 and upstream of the first pump 10. However, said branch at which the outgoing valve 67 is arranged, can also be located at a different place in the loop conduit 29.

(29) Within a process for the production of moulding compounds, in particular for the production of acrylonitrile-butadiene-styrene (ABS), using the system according to FIG. 2, the first reagent 11 and the second reagent 12 are fed to the mixing vessel 50.

(30) Additionally, a solvent, for example EB (ethylbenzene), can be added to the reagents 11, 12. Within the mixing vessel 50, by a rotation of the beater 52, a premixing of the reagents 11, 12 proceeds to form a premix.

(31) The resultant premix of the reagents 11, 12 is then fed to the inlet 42 of the first pump 10 while the outgoing valve 67 is closed. The premix of the reagents 11, 12 is forwarded in loops through the loop conduit 29 towards the static mixer 36 by means of the first pump 10. From the static mixer 36, the premix of the reagents 11, 12 is fed further through the loop conduit 29 and back to the mixing vessel 50.

(32) Within such a loop through the loop conduit 29 and passing the static mixers 36 and the mixing vessel 50, a partition of the reagents 11, 12 is dispersed to dispersion 15. Within every new loop, some more of the reagents 11, 12 are dispersed to the dispersion 15. The resultant dispersion 15 also travels around within the loop conduit 29 and passing the static mixers 36 and the mixing vessel 50. Thereby, the resultant dispersion 15 is also homogenized.

(33) After a certain number of loops within the loop conduit 29, the reagents 11, 12 are dispersed, at least almost, completely. That means, only the dispersion 15 that is also homogenized, then travels around within the loop conduit 29, still forwarded by the first pump 10.

(34) Then, the outgoing valve 67 is opened, and the resultant dispersion 15 is then pressed out of the loop conduit 29 and delivered through the outgoing valve 67 by means of the first pump 10.

(35) Subsequently, further processing, in particular dewatering, of the resultant dispersion 15 then takes place to give moulding compounds, in particular to give ABS-compositions, as described above.

(36) The further part describes preferred embodiments of the invention.

(37) The thermoplastic molding compound that is produced comprises the first reagent, which is a thermoplastic copolymer A, and the second reagent, which is a graft copolymer B, and optionally further components K, wherein the molding composition comprises:

(38) 40 to 80 wt % of at least one thermoplastic copolymer A obtainable from: 20 to 31 wt %, based on the copolymer A, of acrylonitrile and: 69 to 80 wt %, based on the copolymer A, of styrene or -methylstyrene or a mixture of styrene and -methylstyrene,

(39) 20 to 60 wt % of the graft copolymer B; and

(40) 0 to 5 wt % of further components K,

(41) where the components A, B and K sum to 100 wt %.

(42) The copolymer A contains or consists of styrene-acrylonitrile copolymers (SAN) and is preferably produced from the components acrylonitrile and styrene and/or -methylstyrene by bulk polymerization or in the presence of one or more solvents. Preference is given to copolymers A having weight-average molar masses Mw of from 50,000 to 300,000 g/mol, where the weight molar masses may be determined, for example, by means of GPC with tetrahydrofuran as solvent and with UV detection. The copolymer A forms the matrix of the thermoplastic molding compound. The number-averaged molar masses (Mn) of the copolymer matrix A is preferably from 15,000 to 100,000 g/mol (determined by GPC with tetrahydrofuran as solvent and with UV detection). The viscosity of the copolymer matrix A (determined according to DIN 53726 at 25 C. in a 0.5 wt % solution in DMF) is, for example, from 50 to 120 ml/g. The copolymer matrix A may be produced by bulk polymerization/solution polymerization in, for example, toluene or ethylbenzene according to a process such as is described, for example, in Kunststoff-Handbuch, Vieweg-Daumiller, Vol V, (Polystyrol), Carl-Hanser-Verlag, Munich 1969, pages 122 f., lines 12 ff.

(43) Graft copolymer B, which is a SAN grafted rubber (elastomer) can be constructed from: B1: 40 to 85 wt %, based on the solids content of the graft copolymer B, of a graft substrate (B1) obtainable by:

(44) (a) polymerizing: (B11): 0 to 21 wt %, based on the graft substrate B1, of at least one vinylaromatic monomer, in particular styrene, and (B12): 79 to 100 wt %, based on the graft substrate B1, of at least one diene, in particular butadiene, where (B11) and (B12) sum to 100 wt %; and
(b) agglomerating the obtained graft substrate B1 by adding (C): 0.01 to 5 parts by weight, based on 100 parts by weight of the graft substrate B1, in each case based on the solids content, of an agglomerating copolymer (C) of: (C1): 80 to 99.9 wt % of one or more hydrophobic C1 to C12 alkyl acrylates or C1 to C12 alkyl methacrylates and (C2): 0.1 to 20 wt % of one or more hydrophilic comonomers selected from the group consisting of methacrylamide, acrylamide, methylacrylamide, ethylacrylamide and n-butylacrylamide, where (C1) and (C2) sum to 100 wt %; and
B2: 15 to 60 wt %, based on the solids content of the graft copolymer B, of a graft sheath obtainable by reacting the agglomerated graft substrate B1 with a mixture of: (B21) 70 to 90 wt %, based on the graft sheath (B2), of styrene and/or -methylstyrene, in particular styrene, and (B22) 10 to 30 wt %, based on the graft sheath (B2), of acrylonitrile and/or methyl methacrylate, in particular acrylonitrile, where the graft substrate B1 and the graft sheath B2 sum to 100 wt % in total.

(45) As the further components K, the thermoplastic molding compound may comprise one or more components selected from the group consisting of dispersants, fillers and additives D. As the component K, the thermoplastic molding compounds may further also comprise 0 to 5 wt % of fibrous or particulate fillers or mixtures thereof, in each case based on the amount of the components A plus B plus K. Examples of fillers or reinforcers that may be employed include glass fibers that may be finished with a sizing and a coupling agent, glass beads, mineral fibers, aluminum oxide fibers, mica, quartz flour or wollastonite. It is also possible to admix with the molding compounds metal flakes, metal powder, metal fibers, metal-coated fillers, for example nickel-coated glass fibers, and other additive substances that shield electromagnetic waves. It is also possible to add carbon fibers, carbon black, in particular conductivity carbon black, or nickel-coated carbon fibers.

(46) Various additives (D) may be added to the molding compounds in amounts of from 0 to 5 wt % as assistants and processing additives. Suitable added substances (D) include all substances customarily employed for processing or finishing the polymers. Examples include, for example, dyes, pigments, colorants, antistatic agents, antioxidants, stabilizers for improving thermal stability, stabilizers for increasing photostability, stabilizers for enhancing hydrolysis resistance and chemical resistance, anti-thermal de-composition agents and in particular lubricants that are useful for production of molded bodies/articles. These further added substances may be admixed at any stage of the manufacturing operation, but preferably at an early stage in order to profit early on from the stabilizing effects (or other specific effects) of the added substance. For further customary assistants and added substances, see, for example, Plastics Additives Handbook, Ed. Gchter and Mller, 4th edition, Hanser Publ., Munich, 1996.

(47) Examples of suitable pigments include titanium dioxide, phthalocyanines, ultramarine blue, iron oxides or carbon black, and also the entire class of organic pigments.

(48) Examples of suitable colorants include all dyes that may be used for the transparent, semi-transparent, or non-transparent coloring of polymers, in particular those suitable for coloring styrene copolymers.

(49) Examples of suitable flame retardants that may be used include the halogen-containing or phosphorus-containing compounds known to the person skilled in the art, magnesium hydroxide, and also other commonly used compounds, or mixtures thereof.

(50) Examples of suitable antioxidants include sterically hindered monocyclic or polycyclic phenolic antioxidants which may comprise various substitutions and may also be bridged by substituents. These include not only monomeric but also oligomeric compounds, which may be constructed of a plurality of phenolic units. Hydroquinones and hydroquinone analogs are also suitable, as are substituted compounds, and also antioxidants based on tocopherols and derivatives thereof. It is also possible to use mixtures of different antioxidants. It is possible in principle to use any compounds which are customary in the trade or suitable for styrene copolymers, for example antioxidants from the Irganox range. In addition to the phenolic antioxidants cited above by way of example, it is also possible to use so-called co-stabilizers, in particular phosphorus- or sulfur-containing costabilizers. These phosphorus- or sulfur-containing co-stabilizers are known to those skilled in the art. Examples of suitable light stabilizers include various substituted resorcinols, salicylates, benzotriazoles and benzophenones.

(51) The following example and claims further describe the invention.

(52) A thermoplastic molding compound is produced by a process as outlined which comprises copolymer A, graft co-polymer B, and further components K, wherein the molding composition comprises: 79 wt % of commercial SAN copolymer A, 20 wt % of the graft copolymer B (ABS); and 1 wt % of further components K (antioxidants Irganox and lubricant). This process for the production of the ABS-composition is made, wherein the SAN, the ABS are fed to a loop conduit which comprises a static mixer and the reagents (components) are pressed in loops through the loop conduit and passing the static mixer, whereby the reagents and the additives are dispersed to form a dispersion in the static mixer.

LIST OF REFERENCE SIGNS

(53) 10 first pump 11 first reagent 12 second reagent 15 dispersion 29 loop conduit 36 static mixer 42 inlet 44 outlet 50 mixing vessel 52 beater 62 electric motor 67 outgoing valve 70 second pump 80 third pump