PROCESS FOR THE PREPARATION OF MASTER BATCHES OF ADDITIVES FOR POLYMER-BASED COMPOSITIONS, AND PRODUCTS THUS OBTAINED

Abstract: Process for the preparation of master batches of additives for compositions on the bases of polymers, as flame-retardant agents, stabilizers, oxidation inhibitors, dyes, pigments, antistatic additives, inert and/or reinforcing fillers and the like, of the type providing the coating and/or the blending of said additives (previously micronized) with inert and compacting substances, which process comprises the mixing, in at least two successive mixing steps, of at least one of said additives, previously micronized, with at least one molten wax, said wax having a melting point comprised within the range of approximately from 40<o>C to 160<o>C, and being moreover of such a nature as to result compatible both with said additives, and with polymers comprised in the polymeric composition into which the same additives are destined to be added as master batch, the first one of said mixing steps performing the function of accomplishing a thin film of wax wetting around the individual particles of said additives, and the further mixing step(s) performing the function of first accomplishing the aggregation of the wax-coated particles, as obtained above, as spheroidal particles of about 20 to 2000 mu m in diameter, and of then accomplishing the stabilization of these latter particles into other end spheroidal particles of about 100 to 3000 mu m in diameter, said end particles resulting free-flowing and dust-free. The master batches are characterized by very high concentrations of said additives (80-95%) and by being hygienically safe in the operations they are handled in.

Description: * "PROCESS FOR THE PREPARATION OF MASTER BATCHES OF ADDITIVES FOR POLYMER-BASED COMPOSITIONS, AND PRODUCTS 10 THUS OBTAINED" Techni ι ca < L_Fi ι eJ.d The present invention relates to a process for the preparation of "concentrates" (known to those skilled in 15 the art as "master batches") of additives for compositions on the basis of polymers. §3£J£2I2___Q£__ .!__£ It is known that many additives intended for use in polymer-based compositions, such as stabilizers, oxidation 20 inhibitors, dyes, pigments, flame retardant agents, anti stati c ' additi es, inorganic fillers, and the like, are available as powders, which powders create, the most of the times, severe problems of environmental hygiene to the operators who must handle the same powders to the purpose 25 of incorporating them into said compositions, due to the fact that the powders in question, either because- they are per se poisonous, or because they contain fractions constituted by very fine particles, unavoidingly contaminate the surrounding atmosphere, thus coming into 30 contact with the skin and the respiratory apparatus of said operators, with consequent severe detriment to their health. Some of said powder show furthermore the drawback of yielding explosive mixtures with air, with consequent fire and explosion risks. 2i§£i2iyr2__2Ϊ__.__sll2__.lDϋSD__:i2D A purpose of the present invention is hence the provision of a simple and cheap process for the preparation of master batches of additives for compositions on the basis of polymers, which do not show the above said drawbacks, and hence eliminate any dangers of environmental pollution and therefore can be safely handled. Another purpose of the invention is providing master batches of additives, for compositions on the basis, of polymers, which are free from powders, and having a high content of the same additives. These and still further purposes which shall be clear for one skilled in the art from the following disclosure, are achieved by means of a process of the type providing the coating and/or the blending of said additives with inert and compacting substances, which process comprises, according to the present invention, the ixing, in at least two successive mixing steps, at least one of said additives, previously micronized, with at least a molten wax, said wax having a melting point comprised within the o o range of approximately from 40 C to 160 C, and being moreover of such a nature as to result compatible both with said additives, and with the polymers comprised in the polymeric composition into which the same additives are destined to be added in the form of master batch, the first one of said mixing steps performing the function of providing a thin fi lm of waxy wetting around the individual microparticles of said additives, and the further mixing step(s) performing the function of first accomplishing the aggregation of the wax-coated particles, as obtained above, as spheroidal particles of average diameter of approximately 20 to 2000 μm, and then accomplishing the stabi lization of these latter particles into other end spheroidal particles having an average diameter of approximately 100 to 3000 μm, said end particles resulting free-flowing and dust-free. §≤§!_•__.U d≤__ l_£ ££ iπ2_.2y____.i_ it-IDvent on A preferred, but not exclusive form of practical embodiment of the process of the present invention compri ses : (a) Homogenizing, in the form of microparticles of about 1 to 5 μm in diameter, at least one of said additives, in a high-speed mixer, of known type; (b) Melting, in a conventional melting equipment, a wax having a melting point comprised within the range of approximately from 40 C to 160 C, and of such a nature as to result, compatible both with the additives as of (a), and with the polymers comprised in the polymeric composition in which the same additives are destined to be added as master batch; (c) Adding the desired amount of at least one wax, in the molten state, and as of preceding step (b), to the micronized and homogenized additives contained in the mixer as of (a), such an addition of the wax being accomplished with stirring inside said mixer, in three individual steps comprising: Cc1) First adding about 5-30% by weight of the desired total amount of wax as of (c), the mass being then kept stirred for about 2 to 5 minutes, so to provide a first thin film of waxy wetting on the individual microparticles of said additives; (c2) Then adding a second portion of wax, representing about 5 to 30% by weight of the desired total amount, the whole mass being then kept stirred for about 3 to 5 minutes, so to accomplish the aggregation of the microparticles obtained as under Cc1), as spheroidal particles of about 30 to 500 μm in diameter; Cc3) Finally adding the residual amount of molten wax, the whole mass being then kept stirred for about 2 to 5 minutes, to the purpose of stabilizing the shape of particles obtained in (c2), the same being also brought to the desired end spheroidal size of about 500 to 900 μ , the same particles resulting free-flowing and dust-free, and thus constituting a "safe" and easily handeable master batch, ready to be incorporated into compositions on the basis of polymers. Of course, as desired, particles with controlled size can be selected by means of a normal vibrating screen. The said master batch is characterized by a high concentration of additives, of the order of about 80-95% by weight, the residual 20-5% by weight being, represented by the wax as defined above. Said wax is selected among the esters of montan wax, soaps of synthetic waxy acids, polyolefinic waxes, modified hydrocarbon waxes, esters of fatty acids, stearic acid, and amidic waxes. As it shall be exemplified hereunder, the process according to the invention is particularly useful for preparing master batches on the basis of antimony trioxide (as f lame-retardant agents for compositions on the basis of polyvinyl chloride) and master batches on the basis of a mixture of antimony trioxide and of an organic halo- derivative, such as, e.g., decabromodi phenyI oxide (as f lame-retardant agents for polymeric compositions in general, and in particular for compositions on the basis of acrylonitri le-butadiene-styrene copolymers, known as ABS resins). The first ones of said master batches are constituted, for example, by about 88-92% by weight of antimony trioxide and by about 12-8% of glycerol monostearate, whi lst the second ones are constituted, always to exemplifying purposes, by about 8-12% by weight of a wax on the basis of bi s-ethy lene-stearamide and by about 92-88% by weight of a mixture, constituted in its turn by about 56-66% by weight of decabromodi pheny I oxide and by about 44-34% by weight of antimony trioxide. As it has already been evidenced, said master batches can be a c comp I i ' shed, according to the process of the invention, with the most different additives, either individually, or as mixtures with one another (as flame- retardant agents, stabi lizers, dyes, pigments, inert and/or reinforcing inorganic fi llers, oxidation-inhibiting additives, and the like), said master batches being from time to time suitable to incorporate one or a plurality of said additives in the polymeric compositions based on the most different polymers, both thermoplastic and thermosett i ng in character, as well as in the elastomers, in artificial and synthetic fibres, -and in paints. The following Examples, which are merely i llustrating and not limitative of the invention, shall serve to better explain the same invention. (ComEaratiye2__EXAMPLE_l Into a 20-litre vertical high-speed mixer, having stirring means equipped with two crossed blades, of known type ("Turbomi xer") , charged are, with stirring, 10 kg of powder of antimony trioxide and 1 kg of wax (in the molten state) on the basis of glycerol monostearate (Wax HOSTALUB FE2, with melting point 58 C, available from Hoechst Co. of Frankfurt am Main, FRG), to the purpose of preparing a master batch constituted by 90% by weight of antimony trioxide and by 10% by weight of said wax. The run must be discontinued after 2 minutes because of the blocking , of the stirrer blades, a shapeless, not homogeneous and highly viscous mass being formed, which hence does not allow the prefixed purpose to be achieved. EXAMPLE_2 By using the same mixer of Example 1, charged into the same mixer are first 10 kg of powder of antimony trioxide (which are thus micronized and homogenized), and then 0.1 kg of molten HOSTALUB FE2 wax (the same as of Example 1), the whole being then kept stirred for 3 minutes. Into the same mixer a further 0.3 kg of the same molten wax as above is then added, always with stirring, which stirring is continued for further 5 minutes. At the end, always into the same mixer, the last 0.6 kg of said wax (in the molten state) is added, the mass being then kept stirred for further 4 minutes. At the end, from the mixer the so-obtained master batch of antimony trioxide is then discharged, said master batch appearing formed by dust-free and free-flowing spheroidal aggregates of average diameter of from 500 to 900 μm. As it can be inferred from the above reported data, the above master batch results constituted by 90% by weight of antimony trioxide, and by 10% by weight of wax, said antimony trioxide resulting coated (practically "encapsulated") by said wax. Said master batch demonstrates to be perfectly compatible with both rigid and plastified polyvinyl c loride. EXAMPLE_3 The run is carried out as in Example 2, but with the following variants: (1) in lieu of antimony trioxide alone, a mixture is used (in the same amount of 10 kg) of powders, constituted by 34% by weight of antimony trioxide and by 66% by weight of decabromodi phen I oxide. (2) in lieu of wax ' Hostalub FE2, a wax on the -basis of bis- ethy lene-stearami de (amidic wax HOSTALUB FA1 available from H0ECHST Co. of Frankfurt am Main), with melting point o 141 C is used. The addition of this wax into the mixer is carried out by hot-head sprayer. At the end, a master batch having the form of spheroidal aggregates (average diameter 500 900 μm) is obtained, which results perfectly compatible with ABS resins ( ac ry Loni t ri le-butadi ene-st rene copolymers) . In the above Examples 2 and 3, in each of them, one single type of wax has been used, but within the scope of the invention, in the various steps (d), (c2) and (c3), the use is also contemplated of a plurality of types of wax, as well as of mixtures of different waxes, according to as required. Of course, into the process of the invention, as it has been described above to exemplifying purposes, modifications and variants technically equivalent, but all within the protection scope of the same invention, can be introduced. In particular, the process can be performed by carrying out the related steps in continuous fashion, but always committing to the same steps the functions - in sequence - of "waxy wetting", "aggregation", and "stabilization" of the particles of the hereinabove indicated additives, in such a case such steps being performed with a pr.oper programming of the amounts of molten wax to be added to the powder of the additive(s) destined to form the master batch of the invention.

Claims: C_L_A_I_M_S .1. Process for the preparation of master batches of additives for compositions on the basis of polymers, such as f lame-retardant agents, stabilizers, oxidation- inhibiting additives, dyes, pigments, antistatic additives, inert and/or reinforcing inorganic fi llers and the like, of the type providing the coating and/or the mixing of said additives with inert and compacting substances, characterized in that it comprises the mixing, in at least two subsequent mixing steps, of at least one of said additives, previously micronized, with at least one molten wax, said wax having a melting point comprised o o within the range of approximately from 40 C to 160 C, and being furthermore of such a nature as to result compatible both with said additives and with the polymers comprised in the polymeric composition to which the same additives are intended to be admixed in the form of master batch, the first one of said mixing steps performing the function of providing a thin fi lm of waxy wetting around the individual microparticles of said addi ives, and the further mixing step(s) performing the functoins of providing first the aggregation of the waxed particles, as obtained above, as spheroidal particles having an average diameter of about 20 to 2000 μm, and then the stabi lization of these latter particles into other end spheroi al particles having an average diameter of about 100 to 3000 μm, said end particles resulting free-flowing and dust-free. 2. Process according -to claim 1, characterized in that it comprises (a) homogenizing, in the form of microparticles of about ' 1 to 5 μm in diameter, at least one of said additives, in a high-speed mixer, of known type; (b) melting, in a conventional melting equipment, a wax having a melting point comprised within the range of approximately from 40 C to 160 C, and of such a nature as to result compatible both with the additives as of (a), and with the polymers comprised in the polymeric composition into which the same additives are intended for addition as master batch; (c) Adding the desired amount of wax, in the molten state, and as of preceding step (b), to the micronized and homogenized additives contained in the mixer as of (a), such an addition of the wax being accomplished with stirring inside said mixer, in three individual steps compri sing: (d) first adding about 5-30% by weight of the desired total amount of wax as of (c), the mass being then kept stirred for about 2 to 5 minutes, so to accomplish a first thin film of waxy wetting on the individual microparticles of said additives; (c2) then adding a second portion of wax, representing about 5 to 30% by weight of the desired total amount, the whole mass being then kept stirred for about 3 to 5 minutes, so to accomplish the aggregation of the microparticles obtained as under (d), as spheroidal particles of about 30 to 500 μm in diameter; (c3) finally adding the residual amount of molten wax, the whole mass being then kept stirred for about 2 to 5 minutes, to the purpose of stabilizing the shape of particles obtained in ( c2), the same being also brought to the desired end spheroidal size of about 500 to 900 μm, the same particles resulting free-flowing and dust-free. 3. Process according to claim 1, characterized in that said master batches contain about 80-95% by weight of said additives, and about 20-5% by weight of said wax. 4. Process according to clai 1, characterized in that said wax is selected among the esters of montan wax, soaps of synthetic waxy acids, polyolefinic waxes, modified hydrocarbon waxes, 'esters of fatty acids, stearic acid, and amidic waxes. 5. Master batches of additives for compositions on the basis of polymers, of the type providing a coating of the same additives when these are in powder form, characterized in that - said master batches have the form of aggregates of microparticles of said additives, the same microparticles having average size comprised within the range of from about 1 to 5 μm, and being individually coated by a thin fi lm of wax, which fi lm isolates and at the same time keeps the said microparticles assembled ith one another; - that said aggregates are of spheroidal shape with average diameter comprised within the range of from about 100 to 3000 μm, they being coated in their turn by a wax fi lm which keeps individually compacted the same aggregates; - that said wax is of such chemical nature as to result compatible both with the additive it goes to coat, and with the polymer into which the same additive is destined to be incorporated by addition accomplished by means of the said aggregates, the same master batches being constituted by about 80-95% of at least one of said additives and by about 20-5% of at least one wax; - that said wax has a melting point comprised within the range of from 40 C to 160 C, it being selected from at least one of the following waxes: esters of montan wax, soaps of synthetic waxy acids, polyolefinic waxes, modified hydrocarbon waxes, esters of fatty acids, stearic acid, and amidic waxes. 6. Master batch according to claim 1, characterized in that it comprises about 92-88% by weight of antimony trioxide and about 8-12% by weight of glycerol monostearate. 7. Use of the master batch according to claim 6,. as flame-retardant additive for compositions on the basis of polyvinyl chloride. 8. Master batch according to claim 1, characterized in that it comprises about 8-12% by weight of a wax constituted by bi s-ethylene-stearami de, and about 92-88% by weight of a mixture, in its turn constituted by 56-66% by weight by an organic bromo-deri vati ve and by about 44- 34% by weight by antimony trioxide. 9. Use of the master batch according to claim 8, as flame-retardant additive for compositions on the basis of aeryloni tri le-butadi ene-styrene (ABS) copolymers.

Inventors: SCARSO LUCIANO, SCARSO, LUCIANO
Applicants: VAMP SRL
Application year: 1986
Main classification: C08K9
IPC codes: C08J3, C08K9