JPS6259726B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to ABS polymers and a new method of producing polymers with particularly advantageous properties. ABS polymers include a matrix phase copolymer containing monoalkenyl aromatic monomers and alkenyl nitrile monomers having a conjugated diene-based rubber grafted with the same monomers dispersed therein. . A variety of methods have been used to produce such polymers, including emulsion, suspension, and bulk polymerization techniques and combinations thereof. Although bulk polymerization products exhibit desirable properties, this technique is limited by the high viscosity that occurs when the reaction is carried out above fairly low conversions, the attendant energy input and equipment requirements, and the polymers that can be achieved. There is a practical limit to the maximum degree of monomer conversion to. In a typical ABS bulk polymerization process, styrene and acrylonitrile are copolymerized in the presence of a diene-based rubber. Initially the rubber is dissolved in monomer and a continuous homogeneous phase predominates. Once the polymerization has begun, these monomers are simultaneously copolymerized by themselves and also as grafts on the rubber backbone. As the monomer polymerizes, two phases appear: polymer dissolved in the monomer and rubber dissolved in the monomer. Initially, the latter phase is predominant, and a lesser "polymer in monomer" phase is dispersed in a larger "monomer rubber" phase. however,
As the polymerization progresses, the "polymer-in-monomer" phase increases its capacity. At this point, a phase inversion phenomenon occurs and the "rubber-in-monomer" phase is dispersed as independent particles in the matrix of the "polymer-in-monomer" phase. Usually in bulk polymerization processes, the rubber contains polymeric/monomer occlusions which serve to swell the volume of the rubber particles. As polymerization proceeds, monomers are converted to polymers, the viscosity of the mixture increases and more energy is required to maintain temperature and compositional uniformity throughout the polymer. A typical prior art method for the continuous production of ABS polymers by bulk polymerization is described in U.S. Pat.
It is described in the specifications of No. 3243481, No. 3337650, and No. 3511895. Prior art methods that involve feeding a polymerization mixture with a rubber solution in a mixture of styrene and acrylonitrile monomers can produce polymers that have a high proportion of acrylonitrile and at the same time have a high rubber content. It has an inherent limitation in that it is not available. This is because although rubber readily dissolves in styrene, its solubility in styrene-acrylonitrile monomer mixtures decreases with increasing concentration of acrylonitrile. For example, styrene monomer can dissolve about 20% of its weight in diene rubber, while 58% styrene and 42%
Monomer mixtures containing acrylonitrile can dissolve less than 10% of the same rubber by weight. That is, the amount of rubber that can be added to the solution in the monomer mixture is limited by the proportion of nitrile monomers. However, for many purposes such as solvent resistance and toughness, it is advantageous to have a high acrylonitrile proportion of 40% by weight or more. The present invention provides a method by which ABS polymers with high proportions of both rubber and acrylonitrile can be obtained, and is a significant advance in the art. There also exists a need for a continuous bulk polymerization process for ABS polymers with high conversion ratios and low energy requirements. It is an object of the present invention to provide a highly efficient polymerization process for ABS polymers with excellent properties. It is also an object of the present invention to provide a process for continuous bulk polymerization of ABS polymers that can be operated on a large scale and at high conversion rates. The present invention has a matrix phase comprising a copolymer of a monoalkenyl aromatic monomer and an ethylenically unsaturated nitrile monomer and a dispersed phase comprising rubber particles having a weight average particle size of about 0.1 to 10μ. In producing ABS polymers, (i) a stirred reactor is continuously charged with a feed stream of monoalkenyl aromatic monomer having 3 to 33% by weight of diene rubber dissolved therein; (ii) simultaneously and continuously charging separate feed streams of ethylenically unsaturated nitrile monomer to the stirred reactor; (iii) controlling both streams to a level above which phase inversion occurs and based on the weight of the polymerization mixture; (iv) charging the polymerization mixture operating at a polymer solids level of up to about 70% by weight; (iv) such that the polymerization mixture has a substantially uniform composition and the rubber has weight average particles of about 0.1 to 10 microns; (v) continuously polymerizing the ABS polymer from the partially polymerized mixture from step (iv) while maintaining agitation such that the ABS polymer is dispersed in the polymerization mixture as rubber particles having a size; It is a continuous bulk polymerization process that involves separate separation. For purposes of simplicity, in the general description of the process described below, styrene will represent a monoalkenyl aromatic monomer and acrylonitrile will represent an alkenyl nitrile monomer. However, it should be understood that the invention is not so limited. In this process, the rubber is dissolved in styrene monomer in an amount of 3 to 33% and preferably 10 to 30% by weight, and the solution is passed through to form a polymerization mixture of substantially uniform composition. A reactor is charged to provide a continuous polymerization zone containing: The reactor has a polymer solids level above that at which phase inversion occurs;
and steady state up to 70% polymer solids.
state). Operating at such polymer solids contents ensures that the rubber, when added, immediately forms small particles containing the monomer component dispersed in the partial polymerization reaction mixture. The polymer solids level of the polymerization mixture is approximately 75cm at 200°C for approximately 10 minutes.
Weigh a sample of the mixture under high vacuum of Hg (approximately 2-3
g) and then reweighing. Using this technique, the residual monomer content (all types) is less than 0.5% and virtually all monomer is removed within 30 seconds so that during polymer separation there is no significant polymerization. It was found that no progress was made. What remains is polymeric and the percent sample weight it represents is the polymer solids content of the polymerizing mixture at that point. Since the acrylonitrile is fed separately but simultaneously and the phase inversion point for this system has passed so that the rubber is dispersed as particles as it enters the reaction mixture, this method is effective in forming the final ABS composition. It has the ability to use high rubber concentrations while still achieving high acrylonitrile concentrations. Preferred ABS molding compositions have high gloss and an average rubber particle size of about 0.5 microns or less, and most preferably from 0.2 to 0.4 microns. Conventional ABS polymers with this small rubber particle however lack toughness. Increasing the acrylonitrile content of such ABS polymers from the usual 24% or thereabouts to the approximately 27-40% range indicates that these small rubber particles effectively bind such ABS polymers to an unexpected degree. Make it possible to become stronger. A continuously stirred reactor that provides a polymerization mixture with a substantially uniform composition in which phase inversion has already occurred allows the rubber to be dispersed in the form of particles as it enters the reaction mixture. constitute important method characteristics. The acrylonitrile stream added separately in this way does not adversely affect the formation of rubber particles. The method requires a reactor that is agitated to give a reaction mixture having a substantially uniform composition throughout, and this does not apply to methods without such compositional uniformity in the reactor, such as continuous plugs. It will be appreciated that this is different from a flow bulk polymerization process, a low backmixing continuous process or a batch bulk/suspension process.
In such systems, the rubber content must be less than 15% and the acrylonitrile content cannot exceed about 25% if rubber precipitate formation is to be avoided. Adding acrylonitrile after phase inversion in plug flow systems does not solve the problem. This is because it leads to the formation of non-homogeneous polymers and in some cases even incompatible phases in the final polymer. The process of the invention may use a single reactor, in which case the polymer solids level at which the process operates is between 50 and 70.
Should be %. Alternatively, multiple reactors can be used, the first being a reactor of the type described above operated at a static polymer solids level of 35-55%, and then operated in continuous mode. followed by a reactor or series of reactors in which the polymerization is carried out to advance the polymerization to the desired degree of conversion. If a reactor series is used, it will of course be necessary to make monomer additions to maintain the composition of the polymer produced within the desired range. The polymer solids content at which the reaction is carried out is limited by two practical considerations. At the lower end of this range (as discussed above), the polymer solids level in the reactor (or the first reactor if a series of reactors is used) to which the monomer stream is added is It is important that the polymer/monomer phase has a larger volume than the rubber/monomer phase so that the rubber/monomer readily forms the dispersed phase. In practice this represents a monomer-to-polymer conversion level of about 35%. At upper levels, the practical constraints on the energy requirements for the reactor agitator are approximately
70% solids limit. This does not necessarily imply similar conversion levels. The reason is that up to 50% and preferably up to 99% monomer-to-polymer conversion using 10-30% by weight of a suitable solvent (based on the weight of monomer fed to the reaction). The reaction mixture can even be diluted to the point where the energy requirements are not excessive. Some or all of the diluent can be introduced with the rubber in the styrene stream, either as an additive component or by the use of rubber already dissolved in a suitable solvent such as hexane or cyclohexane. In many cases, rubber solutions containing up to 50% and preferably 5 to 30% by weight of solvent are very suitable for low molecular weight rubbers, which in undissolved form tend to be very viscous solids or even liquids. provides a convenient means of handling. Diluent can also be added separately or to the acrylonitrile stream. The diluent can be a liquid aromatic hydrocarbon containing 6 to 10 carbon atoms such as benzene, toluene, xylene, ethylbenzene, p-cymene, cumene or mixtures thereof. Other organic solvents such as saturated aliphatic hydrocarbons such as hexane, cyclohexane, cyclopentane and others containing 5 to 7 carbon atoms, ketones such as methyl ethyl ketone, methyl cyclopentane, methyl isobutyl ketone, cyclohexane or methyl propyl ketone may also be used. Can also be used. These ABS polymers have a rubber particle size of about 0.1-0.5μ, a nitrile monomer content of about 27-40% or more preferably about 33%, a rubber content of about 14-25% and a grafting level of 150-200%. Coalescing is generally performed using a matrix phase copolymer of lower molecular weight, e.g.
A molecular weight of 60,000 (M _o ) or about 5,000 to 150,000 (M _v ) is required. Number average (M _o ), weight average (M
The interrelationship of molecular weight _w ) and viscosity average (M _v ) and the calculation of such parameters can be found in the book Crystalline Olefine by Raff and Doak.
Polymers”, page 443 (1965 edition). Generally, the rubber molecular weights cited herein are viscosity average molecular weights, which are referred to in "Angewandt Makromol. Chemie" Volume 14 (1970
Calculated using the technique described by VHLange and H. Bauman in 2010). Once the polymerization has proceeded to the desired normal level, the polymer is stripped of residual monomer. This operation, which is the same whether a single reactor or a series of reactors are used in the polymerization step, is usually carried out in separate equipment, e.g.
The process is carried out in a film devolatilizer or a falling strand devolatilizer. The monomer formulation includes, at least in principle, monoalkenyl aromatic monomers and ethylenically unsaturated nitrile monomers. The monoalkenyl aromatic monomer has at least one formula at least one monomer of It encompasses the body. Examples of monoalkenyl aromatic monomers that can be used in this process include styrene and substituted styrenes such as o-, m- and p-methylstyrene, 2,4-
Dimethylstyrene, corresponding ethylstyrene, p
-Tertiary butylstyrene, α-methylstyrene,
α-ethylstyrene, α-ethyl-p-methylstyrene, vinylnaphthalene, alhalomonoalkenyl aromatic monomers such as o-chlorostyrene, m
-chlorostyrene, p-chlorostyrene, o-bromostyrene and 2,4-dibromostyrene and cyclic alkyl cyclic halo-substituted styrenes such as 2
-methyl-4-chlorostyrene and 2,6-dichloro-4-methylstyrene. Mixtures of such monoalkenyl aromatic monomers can be used if desired. Examples of unsaturated nitrile or alkenyl nitrile monomers that can be used are acrylonitrile, methacrylonitrile, ethacrylonitrile and mixtures thereof. Examples of monomers that can be copolymerized with monoalkenyl aromatic monomers and unsaturated nitrile monomers are α- or β-unsaturated basic acids and their derivatives such as acrylic acid, methyl acrylate,
Ethyl acrylate, butyl acrylate, 2-
Ethylhexyl acrylate, methacrylic acid and corresponding esters thereof, such as methyl methacrylate, acrylamide and methacrylamide, vinyl halides such as vinyl chloride, vinyl bromide and vinylidene chloride, vinylidene bromide, vinyl esters such as vinyl acetate and vinyl propionate, dialkyl maleates. or fumarates such as dimethyl maleate, diethyl maleate, dibutyl maleate and maleic anhydride. The monomer component of the polymerization mixture includes at least 40% by weight of monoalkenyl aromatic monomer and preferably includes at least 50% by weight. They also contain at least 5% by weight of unsaturated nitriles and preferably at least 10% by weight thereof. In practice the monomer components of the polymerization mixture will be 40-95% by weight and preferably 60-85% alkenyl aromatic hydrocarbons and 60-95% by weight
It is desirable to contain 5% and preferably 60-15% and most preferably 60-25% unsaturated nitriles. It is well known that styrene and acrylonitrile monomers can be copolymerized in various proportions. For example, a monomer formulation containing approximately 76 parts styrene and approximately 24 parts acrylonitrile is polymerized by bulk polymerization with reflux of the monomers to produce a polymer having this composition at all degrees of conversion. do. The reason is that monomers in this ratio form an azeotrope. By definition, an azeotropic composition is one in which the polymer formed is identical to that of the unpolymerized monomer formulation. It is known that ratios of these two monomers other than the azeotrope can be used to produce polymers of homogeneous composition. "ABS Plastics" (Reinhold 1964 edition)
is a homogeneous composition of styrene/acrylonitrile using a monomer formulation other than the 76/24 azeotropic SAN composition.
A method of making an ABS polymer with a SAN matrix polymer is described. "ABS Resins" No.
20 (Stamford Research Institute) also describes the production of ABS polymers with homogeneous SAN matrix polymers. In such copolymerizations, one monomer tends to enter the polymer molecule more quickly than the other monomer because of their different reactivities. As conversion of the monomer formulation proceeds, one monomer is removed more rapidly than the other and the monomer formulation changes with the conversion. Therefore, it has a uniform monomer composition
The SAN matrix phase is produced by: (a) using an azeotropic monomer formulation; (b) maintaining a uniform monomer formulation in the reactor by adjusting the monomer charge ratio;
and (c) can be produced by limiting the conversion level so that polymerization rate differences have no substantial effect on the composition. Using this last technique,
76/24SAN prescription until approximately 100% conversion, 70/30SAN
It has been discovered that the formulation can be carried out up to about 75% conversion, and the 35/65 SAN and 90/10 SAN formulations up to about 30-40% conversion. However, in general, if the acrylonitrile content of the ABS polymer is 24% or more, no more than 24% by weight of acrylonitrile must be added to the reactor in order to keep the acrylonitrile concentration of the polymer within the preferred range. Must not be. Preferred rubbers include diene rubber mixtures, ie one or more conjugated 1,3-
Dienes, such as butadiene, isoprene, 2-chloro-1,3-butadiene, 1-chloro-1,3
- Butadiene, piperylene, or any other rubber polymer (rubber polymers meet ASTM test D-746-52T)
0°C, preferably not higher than -20°C). Such rubbers include up to equal weights of one or more copolymerizable ethylenically unsaturated monomers, including monoalkenyl aromatic hydrocarbons such as styrene and substituted styrenes such as o-, m- and p-
-Methylstyrene, 2,4-dimethylstyrene,
and corresponding ar-alkylstyrenes, α-methylstyrenes, α-ethylstyrenes, including p-tertiary butylstyrene and others,
α-methyl-p-methylstyrene, vinylnaphthalene, ar-halomonoalkenyl aromatic hydrocarbons such as o-, m- and p-chlorostyrene, 2,
4-dibromostyrene and 2-methyl-4-chlorostyrene, acrylonitrile, methacrylonitrile, ethacrylonitrile, α- or β-unsaturated basic acids and their derivatives such as acrylic acid, methyl acrylate, ethyl acrylate,
butyl acrylate, 2-ethylhexyl acrylate, methacrylic acid and corresponding esters thereof such as methyl methacrylate, acrylamide and methacrylamide, vinyl halides such as vinyl chloride, vinylidene bromide, vinyl esters such as vinyl acetate and vinyl propionate, dialkyl maleates or fumarates such as Examples include copolymers and block copolymers of conjugated 1,3-dienes with dimethyl maleate, diethyl maleate, dibutyl maleate, and maleic anhydride. A useful group of rubbers are stereospecific polybutadiene rubbers made by polymerization of 1,3-butadiene. These rubbers have a cis isomer content of about 30-98% and a trans isomer content of about 70-2%, and generally have at least about 85% polybutadiene formed by addition of 1,4 and about 15% Contains not more than 1,2% of 1,2 additions. Mooney viscosity of this rubber (ML-4,
100°C) ranges from about 0 to 70 and from about -50°C to -105 as measured by ASTM test D-746-52T.
It has a second-order transition temperature of °C. The diene rubbers used in the production of grafted diene rubbers are styrene-soluble diene rubbers of the type described above. Stereospecific polybutadiene rubbers are preferred for optimum physical properties of the polymer. The diene rubbers used in diene grafted rubbers are of the type described above. A preferred group of rubbers consists essentially of 75-100% by weight of butadiene and/or isoprene and up to 25% by weight of monovinylidene aromatic hydrocarbons (e.g. styrene) and unsaturated nitriles (e.g. acrylonitrile).
or a mixture thereof. The diene rubber may contain up to about 2% cross-linking agent, based on the weight of rubber monomer. The cross-linking agent is any agent commonly used for forming cross-links in diene rubbers, such as divinylbenzene, diallyl maleate, diallyl fumarate,
It can be diallyl adipate, allyl acrylate, allyl methacrylate, diacrylate and dimethacrylate, or polyhydric alcohols such as ethylene glycol dimethacrylate and others. As mentioned above, the rubber content of the rubber in the styrene solution fed to the reactor may be from 3 to 33% by weight, preferably from 10 to 30% by weight. This means the rubber content in ABS polymers up to about 30% by weight e.g. 10-30% by weight
A polymer having a rubber content of . The process of the invention is particularly useful for the production of ABS polymers having 14-25% by weight rubber. This rubber content of the ABS polymer, expressed in terms of the weight of the rubber itself rather than the grafted rubber produced during polymerization, is not necessarily the same as that charged to the reaction mixture. This is because the rubber is necessarily present in the polymeric portion of the reaction mixture and, as a result, removal of unreacted monomer after polymerization has reached the desired level will result in a correspondingly higher proportion of rubber in the residue. This is because it results in giving . Monomer to polymer conversion can be carried out at about 30-99%. If monomer separation is carried out after only 50% monomer-polymer conversion, the rubber content will be approximately 100% higher than that obtained if the polymerization were allowed to proceed until reaching 100% conversion. will. Therefore, the rubber content of the ABS polymer can be easily controlled by the feed weight percent and the monomer conversion level prior to residual monomer separation. Rubbers having a viscosity average molecular weight of about 200,000 or greater generally produce rubber particle sizes in the range of 1 to 10 microns, preferably 1 to 5 microns. However, the rubber particle size with a weight average diameter of 1μ or less is 0.2~
For particles in the 0.5μ range, diene rubber is 5000~
It has been found that compounds having a viscosity average molecular weight in the range of 150,000, preferably 5,000 to 50,000, and most preferably 20,000 to 30,000 are readily formed in the present process. Generally, the molecular weight of rubber is 1 in diameter.
In order to produce a polymer having rubber particles of less than μ, it is desirable that the molecular weight be lower than that of the graft copolymer. The dispersed rubber phase increases the toughness of ABS polymers. Generally, the impact strength of such polymers increases with the weight percent rubber dispersed in the polymer. This impact strength is also influenced by the size of the dispersed rubber particles. Higher impact strength is provided by particles with a weight average particle diameter in the range 0.5-10μ. The weight average diameter of the rubber particles also affects gloss. Smaller particles provide high gloss and larger particles provide low gloss to the molded article or sheet. Selection of optimum rubber particle size must balance impact strength with gloss requirements. Regarding the particle size range of 0.1-10μ, rubber particles in the range of 0.1-5μ and especially 0.2-2μ are most preferred for the best balance of impact strength and gloss. The weight average particle diameters discussed herein are measured using a photosedimentometer and the method described by MJ Graves et al., British Chemical Engineering, Vol. 9, pp. 742-744 (1964). . The particle sizes described herein were determined using a Martin Sweets Model 3000 Particle Size Analyzer. In the present invention, monomer formulations comprising, at least in principle, mixtures of monoalkenyl aromatic monomers and ethylenically unsaturated nitrile monomers are readily polymerized in the presence of a dispersed rubber phase. Forming a matrix phase copolymer. Optionally small proportions of other monomers can be present in the copolymer.
The copolymer in the partial polymerization mixture is formed either as a free or matrix phase polymer or as a polymer grafted onto diene rubber particles. The matrix phase and the grafted copolymer have approximately the same composition for a given formulation. Polymerization can be initiated by any free radical-generating initiator that promotes grafting and is activated at the intended reaction temperature.
Suitable initiators include peresters and peroxycarbonates such as tertiary butyl perbenzoate, tertiary butyl peroxyisopropyl carbonate, tertiary butyl peroctoate, tertiary butyl peroxyisonoate, tertiary Mention may be made of butyl 2-ethylhexyl monoperoxy carbonate and mixtures thereof. These initiators are generally included primarily in the range of 0.001 to 3.0% by weight of polymerizable material, depending on the monomers present, and preferably on the order of 0.005 to 1.0%. Acrylonitrile monomer is charged to the reactor in an amount such that the partial polymerization mixture in the reactor contains about 15 to 60 weight percent acrylonitrile, based on the total monomer charged. This mode of operation makes the ABS polymer higher in acrylonitrile content, which is in the preferred range of about 25-40% by weight. As is well known, it is often desirable to include relatively small percentages of molecular weight control agents such as mercaptans, halides and terpenes, on the order of 0.001 to 1.0% by weight of the polymerizable material. Additionally, it may be desirable to include relatively small amounts of antioxidants or stabilizers such as common alkylated phenols.
Alternatively, they may be added during or after the polymerization. The formulation may also contain other additives that are suitable or dispersible in the formulation, such as stabilizers, plasticizers, lubricants, colorants, and non-reactive preformed polymeric materials. The process of the invention can be operated using a single reactor with a single reaction zone, in which case the rubber-in-styrene solution and the acrylonitrile feed stream are at or above the level at which phase inversion occurs. and then continuously fed into a reactor operating at polymer solids levels of up to about 70%, or in other words at 30 to 99% conversion of the total feed monomer, and then Combined collection will be carried out. In a preferred method, this reaction is carried out in two reactors. The first reactor A is agitated and operated at a polymer solids content of 35-55% to give a reaction mixture having a substantially uniform composition throughout, and the second reactor B is 55% polymer solids. ~
It is a continuous bulk reactor operated at 70% polymer solids content. This preferred method is described in more detail below. Reactor A Simultaneously and continuously (1) a solution of styrene monomer in which about 3-33% by weight of diene rubber having a molecular weight ( _Mv ) of 5,000-50,000 is dissolved; and (2)
A first partial polymerization mixture is formed in reactor A by charging a separate acrylonitrile monomer feed stream to the reactor. The reactor is then agitated to provide a mixture of substantially homogeneous composition. The reactor is operated at a static state monomer-to-polymer conversion of about 30-50% (35-55% polymer solids content), so that the rubber is about 0.1-10μ upon addition.
directly dispersed as rubber particles having a weight average particle size of . The monomer at a temperature of about 90° to 180°C and about 0.7 to
It is polymerized at an operating pressure of 14 Kg/cm ² and at least a portion of the monomers polymerized are grafted onto the diene rubber as substrate copolymer molecules. Although the amount of polymeric superstrate grafted onto a 100 parts rubber substrate can vary from as little as 10.0 parts by weight to as much as 20,000 parts or more, preferred graft copolymers generally include The superstrate/substrate weight ratio is about 20-200:100, and most preferably about 50-150:100. Highly desirable improvements in various properties are generally obtained when using grafting ratios of about 50 to 150:100. In reactor A, (1) formation and dispersion of the rubber particles and (2) grafting of the rubber particles must occur while preserving the size and morphology or structure of the rubber particles. Some monomer/polymer phase is often occluded within the rubber particles. The amount of such occluded monomer-polymer phase is maintained at a constant level by static state polymerization. It has been discovered that the greater the storage capacity within the rubber particles, the more efficiently the rubber phase is used to toughen the polymer. Rubber particles function as approximately pure rubber particles when their occlusion is controlled to a level of about 0.25 to 2.5 parts by weight based on the particle weight. The occluding monomer also begins to polymerize and form a monomer/polymer component within the rubber particles. The rubber particles are also externally grafted to stabilize their structure with respect to size and their dispersibility in the monomer-polymer phase. The first reactor produces a first partially polymerized mixture of a monomer-polymer phase having the rubber phase dispersed therein. Reactor B generally 55-99% and preferably 55-80%
Reactor B is preferably a continuously stirred reactor of the type used as reactor A, or a continuous stirred reactor of the type used as reactor A. A series of reactors like this. Reactor B is preferably operated at a temperature of 110° to 180°C and an operating pressure of 0.7 to 14.0 kg/cm ² . The polymerization reaction is exothermic and cooling may be provided by vaporization of a portion of the monomer from the reaction mass. However, if the desired composition is greater than or equal to the S/AN azeotrope, it may be necessary to maintain the desired monomer ratio in reactor B by using separate polymer feeds at appropriate concentrations. Will. Cooling can be provided additionally or alternately by the reactor jacket. Cooling can also be provided by feeding condensed recycled monomer into reactor B. It may also be suitable to use as reactor B a continuous flow-through reactor provided with efficient agitation. The cooling mechanisms described above are also useful for such reactors. As the material progresses through such a reactor, the amount of polymer increases continuously, the amount of monomer decreases (due to losses through polymerization and vaporization), and the temperature decreases from inlet to outlet. It increases gradually until To allow for the natural swelling of the reaction mass and to provide space for the escape of vapors, such reactors are usually operated at a filling degree of about 15-90% of their capacity, preferably 40-75%. ing. Recovery of ABS Polymer Two or more partial polymerization mixtures exiting a single reactor (if only one is used) or the last reactor if a series of reactors is used. The remaining unreacted monomers can be removed by using the above volatile matter removal device. Such devolatilization is carried out in a known manner in any desired devolatilization equipment, such as wiped film or falling strand type. The devolatilization process is generally carried out at a temperature of about 140 DEG to 280 DEG C. and a reduced pressure of 0.01 to 700 mm Hg absolute, preferably at about 180 DEG to 250 DEG C. and 2 to 200 mm Hg absolute. The partially polymerized mixture can be preheated to the desired devolatilization temperature prior to devolatilization by passing it through a conventional tube and shell heat exchanger or the like. The product of the devolatilization step is a polymer composition with residual monomer levels reduced to less than about 2.0% by weight, and desirably less than about 0.4% by weight. After removing the devolatilized polymer from the devolatilization step, generally in the form of a melt, it is formed into a strand or other shape by the use of a strand die or other conventional means, and then The pellets are then cooled and cut or pelletized to the desired final size and stored or packaged for shipment. All final operations can be carried out in a conventional manner using known equipment and equipment. The following examples are provided to more clearly explain the principles and practice of the invention to those skilled in the art.
These examples are not intended to be limiting, but merely illustrative of the invention disclosed herein. Example 1 A diene rubber (9.8 parts) of 90% butadiene and 10% styrene was dissolved in 46.8 parts of styrene monomer to form a monomer rubber solution. This solution was fed to the first reactor where it was stirred to maintain an essentially uniform composition throughout. 1
A separate feed stream of 34.2 parts of acrylonitrile was continuously fed to this reactor at a volume of 34.2 parts, while the first reactor was operated in steady state conversion at 125° C. and approximately 44% polymer solids. Approximately 0.15 parts of terpinoline and 0.03 parts of tertiary butyl peroxyisononoate were added to the monomer rubber solution during feeding to the first reactor. The feed stream is continuously added to the first reactor while the feed stream has an average residence or transit time in the reactor of about 1.3 hours and maintains a monomer-to-polymer steady state conversion of about 34%. Approximately 44% polymer solids was provided in the first reactor. The partially polymerized reaction mixture from the first reactor is continuously fed to a 1 volume second reactor operated at 123° C. and about 57% monomer-to-polymer conversion in a steady state manner. . A polymer solids content of about 61% and an average feed residence (or passage) time of about 2.5 hours. A second feed stream of 8.8 parts styrene and 0.2 parts terpinoline is added to this second reactor along with the partial polymerization reaction mixture from the first reactor to form a homogeneous styrene-acrylonitrile matrix copolymer and graft copolymer. Make it certain. The parts provide a total of 100 parts and represent the relative proportions of the feeds that are fed and polymerized to form the ABS polymer. Thus, the first reaction zone was operated using a feed containing about 58% styrene monomer and 42% acrylonitrile, while the second reactor had about 62% styrene and 38% acrylonitrile. A mixture comprising: The reactor mixture removed from the second reactor is placed in a wiped film devolatilizer.
Continuous devolatilization at 410° C. (210° C.) and 15 cm Hg produced an ABS polymer having a rubber content of about 17% and a rubber particle size of about 1.0 μ. This matrix and graft copolymer are approximately
30% acrylonitrile content and about 164000M _v
It had a molecular weight of Izod impact strength is
320 J/m (60 foot pounds per inch), giving an ABS polymer of excellent toughness and great utility. Examples 2-6 13 parts of polybutadiene-diene rubber of a different molecular weight than that used in Example 1 were dissolved in 40 parts of styrene and 21 parts of ethylbenzene. about
0.13 parts of tertiary butyl peroctoate catalyst was added to this solution and it was continuously heated at 57% polymer solids (69% monomer-to-polymer conversion), 40 rpm stirring speed, and 116°C. The polymerization mixture was charged into a substantially uniform composition in a single stirred reactor operated at a temperature and an average flow rate of about 0.9 hours. A separate 24 parts acrylonitrile stream was added to the reactor concurrently with the styrene-diluent-rubber stream. The monomer formulation fed to the polymerization mixture was approximately 63
% styrene and 37% acrylonitrile, and this gave a matrix and graft polymer with an acrylonitrile content of about 30% by weight based on the polymerized monomers.

TABLE From the above data it is clear that rubber particle size can be reduced by lowering the rubber molecular weight. However, mold toughness can be maintained down to rubber particle sizes of about 0.3 microns or less. Toughness can be easily increased within this process by increasing the rubber content by as much as about 25%.

Claims (1)

Claims: 1. A matrix phase comprising a copolymer of a monoalkenyl aromatic monomer and an ethylenically unsaturated nitrile monomer and a dispersion comprising rubber particles having a weight average particle size of about 0.1 to 10 microns. have a phase
In producing ABS polymers, (i) a stirred reactor is continuously charged with a feed stream of monoalkenyl aromatic monomer having 3 to 33% by weight of diene rubber dissolved therein; (ii) simultaneously and continuously charging separate feed streams of ethylenically unsaturated nitrile monomer to the stirred reactor; (iii) controlling both streams at a level above which phase inversion occurs and based on the weight of the polymerization mixture; (iv) a rubber such that the polymerization mixture has a substantially uniform composition and the rubber has a weight average particle size of about 0.1 to 10 microns; continuously polymerizing the mixture while maintaining agitation such that it is dispersed in the polymerization mixture as particles; and (v) continuously separating the ABS polymer from the partially polymerized mixture from step (iv). A continuous bulk polymerization method comprising: 2. The monomer mixture in the reactor contains 15 to 60% by weight of ethylenically unsaturated nitrile monomer,
A method according to claim 1. 3. A process according to claim 2, wherein the monomer mixture in the reactor contains 25 to 60% by weight acrylonitrile. 4 The rubber in (i) above has a polymer weight of 14
25. The method of claim 1, wherein the ABS polymer is added in an amount sufficient to produce an ABS polymer of up to 25%. 5. Claim 1, wherein the rubber in (i) has a viscosity average molecular weight of 5,000 to 50,000.
The method described in section. 6. The method of claim 1, wherein the rubber is dispersed in the reactor as particles with a weight average particle size of 0.2 to 0.5 microns. 7. The reactor contains styrene and a diene rubber having a viscosity average molecular weight of 5,000 to 50,000, and
A solution containing 30% rubber by weight and a separate stream of acrylonitrile was charged to reduce the rubber content to 0.2-0.5% by weight.
Said claim produces a polymerization mixture having a substantially uniform composition comprising 25-60% acrylonitrile (based on the weight of monomers present) dispersed as particles with a weight average particle size of μ. The method described in item 1. 8. A process according to any of the preceding claims, wherein the polymerization mixture contains up to 50% by weight of diluent, based on the monomers fed to the reactor. 9. The polymerization mixture of claims 1 to 7, wherein the polymerization mixture includes a graft-promoting initiator selected from peroxycarbonates and peresters and activated at a reaction temperature between 110° and 180°C. Any method described. 10. A process according to any of the preceding claims, wherein the polymerization is carried out in a single reactor operated at a monomer-to-polymer conversion of 30 to 99%. 11 Polymerization is carried out in two reactors, the first reactor being operated at a polymer solids content of 35-55% and the second reactor being continuously fed with the partially polymerized mixture where the polymerization proceeds to the desired level. 8. A method according to any of the preceding claims, wherein: 12. The first claim wherein the separation of the ABS polymer from the partially polymerized mixture is accomplished using a wiped film devolatilizer.
7. The method according to any one of items 7 to 7. 13A 10-30% diluent and on monomer charge into a polymerization mixture having a 35-55% polymer solids level in a first reactor which is stirred to provide a substantially uniform composition. consisting of effective amounts of tertiary butyl perbenzoate, tertiary butyl peroxyisopropyl carbonate, tertiary butyl peroctoate, tertiary butyl peroxyisononoate and tertiary butyl 2-ethylhexyl monoperoxy carbonate. B. charging the rubber and monomer with an initiator selected from the group B. continuously operating the first partially polymerized stream from the first reactor with substantially uniform composition throughout; Further polymerization in two reactors results in a second polymer having a polymer solids content of up to 70%.
C. and separating the ABS polymer from the second partially polymerized stream using a wiped film devolatilizer. Method described in Crab.