Method for manufacturing high-impact polystyrene having an improved rubber form

Abstract

A process for manufacturing high-impact polystyrene is disclosed, comprising the steps of: introducing a partially polymerized mixture comprising one or more vinyl aromatic monomers, an elastomer, and a reacted vinyl aromatic monomer into a reactor, wherein the partially polymerized mixture does not undergo phase inversion; polymerizing the partially polymerized mixture in the reactor to a phase inversion point to form a phase inversion mixture; recovering a portion of the phase inversion mixture comprising high-impact polystyrene from the reactor; and introducing at least a portion of the phase inversion mixture into another reactor.

Description

Technology Field

[0001] Cross-reference regarding related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 010,498, filed on April 15, 2020, titled "Methods for Production of High Impact Polystyrene Having an Improved Rubber Morphology," the entire text of which is incorporated herein by reference for all purposes.

[0003] Statements regarding research or development sponsored by the federal government

[0004] It does not apply.

[0005] The present disclosure generally relates to the manufacture of high-impact polystyrene, and more specifically to the manufacture of high-impact polystyrene having an improved rubber morphology. Background Technology

[0006] Elastomer-reinforced polymers of monovinylidene aromatic compounds, such as styrene, alpha-methylstyrene, and ring-substituted styrene, have been widely used commercially. For example, elastomer-reinforced styrene polymers having individual particles of cross-linked elastomer dispersed throughout a styrene polymer matrix can be useful in a variety of applications, including food packaging, office supplies, point-of-purchase markings and displays, household goods and consumer products, building insulation, and cosmetic packaging. These elastomer-reinforced polymers are commonly referred to as high-impact polystyrene (HIPS).

[0007] The mechanical properties of HIPS and their consequent potential applications depend significantly on elastomer (rubber) particles having a desirable morphological structure. As in the art, the terms "elastomer" and "rubber" are used interchangeably in this specification. For example, undesirable mixed forms may be characterized by a broad rubber particle size distribution, with HIPS having a significant amount of small rubber particles with an average diameter of less than 1 micron. Small rubber particles in mixed forms, such as thread or maze shapes, can reduce rubber utilization. Furthermore, HIPS having a form characterized by the presence of small rubber particles generally exhibits poor ductility, having low values ​​for elongation at failure. Therefore, there is a need for a method to manufacture HIPS having an improved rubber form, characterized by a narrow rubber particle size distribution.

[0008] The present specification discloses a process for manufacturing high-impact polystyrene, comprising the steps of: introducing a partially polymerized mixture comprising one or more vinyl aromatic monomers, an elastomer, and a reacted vinyl aromatic monomer into a reactor, wherein the partially polymerized mixture does not undergo phase inversion; polymerizing the partially polymerized mixture in the reactor to a phase inversion point to form a phase-inverted mixture; recovering a portion of the phase-inverted mixture comprising high-impact polystyrene from the reactor; and introducing another portion of the phase-inverted mixture into another reactor.

[0009] Additionally, the present specification discloses a process for manufacturing high-impact polystyrene, comprising: a step of introducing a partially polymerized mixture comprising one or more vinyl aromatic monomers, an elastomer, and a reacted vinyl aromatic monomer into a first reactor, wherein the partially polymerized mixture does not undergo phase inversion; a step of polymerizing the partially polymerized mixture in the first reactor to a phase inversion point to form a phase-inverted mixture; a step of introducing a portion of the phase-inverted mixture from the first reactor into a second reactor, wherein the second reactor is positioned downstream of the first reactor; and a step of recovering another portion of the phase-inverted mixture, wherein the other portion of the recovered phase-inverted mixture comprises high-impact polystyrene.

[0010] Additionally, the present specification discloses a high-impact polystyrene reactor system, said reactor system comprising: (a) a first continuous stirred tank reactor having an inlet configured to receive (i) one or more vinyl aromatic monomers, (ii) an elastomer, and (iii) a free radical initiator, and (b) an outlet configured to deliver a first reactor effluent; (a) a second continuous stirred tank reactor fluidly communicating with the first continuous stirred tank reactor outlet, having an inlet configured to receive (i) a portion of the first reactor effluent from the first continuous stirred tank reactor, (ii) at least one vinyl aromatic monomer, (iii) an elastomer, and (iv) a free radical initiator, and (b) an outlet configured to deliver a portion of the second reactor effluent comprising high-impact polystyrene; and a conduit for establishing a recirculation stream between the second reactor and the first reactor, said conduit comprising the recirculation stream comprising another portion of the second reactor effluent.

[0011] The foregoing description has been somewhat broad in its explanation of the features and technical advantages of the subject matter currently disclosed to better facilitate the following detailed description. Additional features and advantages of the subject matter disclosed that form the subject matter of the claims of this disclosure will be described below. It should be understood by those skilled in the art that the disclosed concepts and specific embodiments can be readily utilized as a basis for modifying or designing other structures to achieve the same purpose of the subject matter of the currently claimed invention. Furthermore, it should be recognized by those skilled in the art that such equivalent configurations do not depart from the spirit and scope of the subject matter of the currently claimed invention as described in the appended claims. Brief explanation of the drawing

[0012] For a detailed description of the embodiments of the subject matter of the invention disclosed herein, reference will now be made to the attached drawings below. Figure 1 is a diagram of the HIPS polymerization reaction. Figure 2 is a schematic diagram of a polymerization reactor system. Figures 3 and 4 are scanning transmission electron microscope images of samples from Examples 1 and 2. Specific details for implementing the invention

[0013] A method for manufacturing HIPS having a rubber particle size distribution (RPSD or span) of about 1.5 or less is disclosed herein. Such HIPS having a narrow rubber particle size distribution is referred to as improved morphology HIPS, and is designated as IM-HIPS in this specification.

[0014] The manufacture of HIPS generally involves the dissolution of rubber (e.g., polybutadiene elastomer (PB)) within styrene, which is subsequently polymerized. During polymerization, phase separation based on the immiscibility of polystyrene (PS) and polybutadiene (PB) occurs in two stages. Initially, PB forms a major or continuous phase in which styrene is dispersed. When the reaction begins, PS droplets (PS droplets; 10) (dark circles) are formed and dispersed in an elastomer solution (20) (bright background) of PB and styrene monomers, as shown in FIG. 1a. As the reaction proceeds and the amount of polystyrene continues to increase, shape deformation or phase inversion occurs so that PS forms a continuous phase and PB and styrene monomers form a discontinuous phase, as shown in FIG. 1b. This phase inversion leads to the formation of a discontinuous phase containing complex elastomeric particles, in which the elastomer exists in the form of a PB membrane surrounding the occluded domains of PS, as indicated by reference number 30 (bright circle) in FIG. 1C. Shear agitation may be used to induce the phase inversion. Polymerization performed on a rheometer takes 10 to 30 seconds. -1 It shows that the shear rate is sufficient to reverse the two phases.

[0015] The polymerization of HIPS can be expressed according to the chemical reaction equation given in Reaction Scheme I.

[0016] [Reaction Equation I]

[0017]

[0018] The reaction demonstrates the formation of polystyrene chains in the presence of PB, which induces the production of grafted polybutadiene PS, a factor influencing the morphology of HIPS.

[0019] In one embodiment, a method for manufacturing IM-HIPS comprises a first reactor into which a first reaction mixture comprising a styrene monomer, an elastomer particle, and a free radical initiator is introduced, each of which will be described in more detail herein. The first reaction mixture may then be polymerized in the first reactor to form a reaction mixture. For example, the first reaction mixture may be polymerized until the percentage of solid in the first reaction mixture reaches a range of 1% to about 25%, alternatively about 1% to about 10%, or alternatively about 5% to about 10%, based on the total amount of solid in the reactor. In one embodiment, the reaction mixture mainly comprises unreacted styrene, rubber, and polystyrene.

[0020] The method for manufacturing IM-HIPS of the present disclosure further comprises the step of introducing at least a portion of the reaction mixture as a component of the feedstock into a second reactor. In some embodiments, the reaction mixture is introduced discontinuously into the second reactor in an amount ranging from about 1 volume percent (volume%) to about 20 volume%, alternatively from about 1 volume% to about 15 volume%, or alternatively from about 1 volume% to about 5 volume%, based on the total volume of the first reactor. In alternative embodiments, the reaction mixture is introduced continuously into the second reactor for a time that satisfies some user or process objectives at a unit flow rate ranging from about 1 volume% to about 20 volume%, alternatively from about 1 volume% to about 15 volume%, based on the total volume of the first reactor. For example, at least a portion of the reaction mixture may be transferred at a rate ranging from about 1% to about 20% of the volume of the first reactor per minute.

[0021] In one embodiment, to produce a reactor effluent, the feedstock is polymerized in a second reactor up to at least a phase inversion point. The reactor effluent may include unreacted styrene, polystyrene, polystyrene graft rubber, and high-impact polystyrene.

[0022] In one embodiment, the method of the present disclosure comprises the step of establishing a recirculation stream between a first reactor and a second reactor, wherein the recirculation stream comprises a portion of the reactor effluent. A recirculation stream may be established between the first reactor and the second reactor so that the reactor effluent is introduced from the second reactor to the first reactor. In some embodiments, the reactor effluent is introduced discontinuously into the first reactor in an amount ranging from about 0.1 volume percent (volume%) to about 20 volume%, alternatively from about 0.1 volume% to about 1 volume%, or alternatively from about 0.1 volume% to about 0.5 volume% based on the total volume of the second reactor. In an alternative embodiment, the reactor effluent is continuously introduced into the first reactor for a time that satisfies some user or process objectives at a unit flow rate in the range of about 0.1 volume% to about 20 volume%, alternatively about 0.1 volume% to about 1 volume%, or alternatively about 0.1 volume% to about 0.5 volume%, based on the total volume of the second reactor.

[0023] In some aspects of the present disclosure, IM-HIPS is generated in a stepwise process. The process described herein may be numbered into steps (i.e., Step 1, Step 2) for convenience of reference, but is not intended to restrict the performance of the activities of each step to a specific order. For example, one or more activities described for a specific step may be performed simultaneously with one or more activities of another step, regardless of whether the "other step" is numbered as being after or before the "specific step." Such modifications regarding the timing of activities performed at any specific step may be made by a person skilled in the art who has the advantage of the present disclosure.

[0024] In one embodiment of the present disclosure, a method for manufacturing IM-HIPS comprises: a first step (i.e., step 1) comprising introducing a first reaction mixture comprising a styrene monomer, an elastomer particle, and a free radical initiator into a first reactor. Subsequently, the first reaction mixture may be applied to conditions of the first reactor suitable for polymerization of the first reaction mixture. For example, the first reactor may be heated to a temperature of about 100°C to about 150°C, alternatively about 110°C to about 135°C, or alternatively about 115°C to about 120°C for a time of about 30 minutes to about 120 minutes, alternatively about 30 minutes to about 90 minutes, or alternatively about 30 minutes to about 60 minutes. In one embodiment, step 1 comprises polymerizing the first reaction mixture at a point before phase inversion to produce a reaction mixture having a solid content in the range of about 1% to about 25%, alternatively about 1% to about 15%, or alternatively about 5% to about 10% based on the total amount of material in the reactor.

[0025] In one embodiment of the present disclosure, the method comprises a second step (step 2) in which the reaction mixture is used as a feedstock for a second reactor. In this embodiment, the reaction mixture is transported from the first reactor to the second reactor using any suitable method. The reaction mixture may be transported to the second reactor in a continuous manner at any suitable rate. In one embodiment, the mixture reacted in the second reactor is subjected to conditions suitable for the continued polymerization of the reaction mixture. In some embodiments, the polymerization conditions in the second reactor are the same as the polymerization conditions in the first reactor, and alternatively, the polymerization conditions in the second reactor are different from the polymerization conditions in the first reactor. For example, the polymerization conditions in the second reactor may include a temperature of about 110°C to about 160°C, alternatively about 120°C to about 145°C, or alternatively about 125°C to about 130°C, and a time of about 90 minutes to about 180 minutes, alternatively about 90 minutes to about 150 minutes, or alternatively about 90 minutes to about 120 minutes. In this embodiment, the reaction mixture may be polymerized until a reactor effluent comprising at least 50% solid, alternatively at least 40% solid, or alternatively at least 30% solid is formed in the second reactor based on the total amount of reactor material.

[0026] In one embodiment of the present disclosure, a third step of the process (i.e., step 3) comprises establishing a recirculation stream between a first reactor and a second reactor. For example, a portion of the reactor effluent containing about 10% to about 50% solid may be introduced into the first reactor at a flow rate of about 0.1% to about 20%, alternatively about 0.1% to about 1%, or alternatively about 0.1% to about 0.5%, based on the total volume of the second reactor, and for a time to satisfy some user or process objectives. In one embodiment, the recirculation stream may be established at any time after a solid percentage of about 5% to about 50%, alternatively about 10% to about 40%, or alternatively about 15% to about 30% is formed in the second reactor based on the total amount of material in the reactor. In this embodiment, during the third step, the method for manufacturing IM-HIPS of the present disclosure comprises first and second reactors fluidly connected through at least a first conduit and a second conduit, wherein the first conduit carries a reacted mixture from the first conduit to the second reactor, and the second conduit carries a reactor effluent from the second reactor to the first reactor.

[0027] In one embodiment, the manufacturing process of IM-HIPS may include additional steps (e.g., step 3 + x, where x is 1 or more) in which reactor effluent from a second reactor is transferred to one or more additional reactors for further polymerization and / or treatment to meet the goals sought by some users and / or applications.

[0028] In another embodiment, a process for manufacturing high-impact polystyrene comprises the step of introducing a partially polymerized mixture comprising one or more vinyl aromatic monomers, an elastomer, and a reactive vinyl aromatic monomer into a reactor, wherein the partially polymerized mixture does not undergo phase inversion. The process may further comprise the step of polymerizing the partially polymerized mixture in the reactor up to a phase inversion point to form a phase-inverted mixture. The polymerization of the partially polymerized mixture may be carried out under conditions of the type disclosed herein. In one embodiment, the method further comprises the step of recovering a portion of the phase-inverted mixture from the reactor, wherein the phase-inverted mixture comprises high-impact polystyrene, said recovery step, and the step of introducing another portion of the phase-inverted mixture into another reactor. In one embodiment, the reactor and the other reactor are reactors of the same type. Alternatively, the reactor and the other reactor are reactors of different types.

[0029] In modes in which the reaction mixture is introduced continuously, the first reactor may be fluidly connected to the second reactor. For example, the first reactor may include a reactor having an inlet configured to receive the first reaction mixture and an outlet configured to transfer the reaction mixture to the inlet of the second reactor. A recirculation stream may be established between the outlet of the second reactor and the inlet of the first reactor. This is schematically illustrated in FIG. 2. Referring to FIG. 2, a portion of a reactor system (100) for the manufacture of IM-HIPS, having a first reactor (10) and a second reactor (20), is illustrated. The first reaction mixture is transported to the reactor (10) via line (5), where a reacted mixture is produced according to the polymerization conditions of the type disclosed herein. The reacted mixture may be transferred from the first reactor (10) to the reactor (20) via line (15), and the reactor also produces a reactor effluent after undergoing the polymerization conditions of the type disclosed herein. A portion of the reactor effluent can be transferred from the second reactor (20) to the first reactor (10) via line (25), that is, a recirculation stream can be established. Additionally, the reactor effluent can be transferred to an additional downstream process via line (30).

[0030] Lines for transporting material (e.g., reactor effluent) are shown at specific locations on the reactor (e.g., from line (5) in FIG. 2 to reactor (10)), but it is considered that such lines may be located where a person of ordinary skill needs to allow the transport of material to any area of ​​the reactor. For example, line (5) in FIG. 2 may allow the introduction of material (e.g., first reaction mixture) through the top of the first reactor (10) as shown in FIG. 2. Lines allowing the flow of material to and from the reactor may be placed at any location on the reactor so that, provided these locations are compatible with the equipment used and the material being transported, the material (e.g., first reaction mixture, reactor effluent) may be introduced / removed from any location along the reactor.

[0031] In one embodiment, the first reactor (e.g., reactor (10) of FIG. 2), the second reactor (e.g., reactor (20) of FIG. 2), or both may be continuous stirred tank reactors. A continuous stirred tank reactor (CSTR) generally refers to a reaction vessel that can be continuously stirred or agitated using any suitable stirring means, such as, for example, rotary stirrers, magnetic stirrers, or bubbling or spraying of an inert gas through a liquid phase. The CSTR may be operated as a batch process or a continuous process (e.g., reagents are periodically or continuously added to the CSTR while the reaction mixture is periodically or continuously removed from the CSTR).

[0032] In another embodiment, the first reactor (e.g., reactor (10) of FIG. 2), the second reactor (e.g., reactor (20) of FIG. 2), or both are plug flow reactors (PFRs). Here, PFRs generally refer to reactors in which one or more fluid reagents are pumped through pipes or tubes, chemical reactions proceed as the reagents move through the plug flow reactor, and a mixture containing products is collected as the reactor effluent.

[0033] In another aspect of the present disclosure, a reactor system suitable for use in the present disclosure comprises, as needed, one or more CSTRs and one or more PFRs to produce IM-HIPS of the type disclosed herein.

[0034] In one embodiment, any mixture applied to the polymerization conditions of the type disclosed herein for the preparation of IM-HIPS (e.g., the first reaction mixture) comprises a vinylidene aromatic monomer, alternatively styrene. Styrene, also known as vinylbenzene, ethyleneylbenzene, and phenylethene, is an organic compound represented by the chemical formula C8H8. Similar vinylidene aromatic monomers may be wholly or partially substituted with styrene. Such monomers include, without limitation, various substituted styrenes (e.g., α-methylstyrene), ring-substituted styrenes, such as p-methylstyrene, disubstituted styrene, and unsubstituted styrene. In one embodiment, the styrene monomer constitutes at least 70 weight percent based on the total weight of any mixture applied to the polymerization conditions of the type disclosed herein for the production of IM-HIPS, or alternatively about 70 weight percent to about 95 weight percent or alternatively about 85 weight percent to about 95 weight percent.

[0035] In one embodiment, any mixture applied to the polymerization conditions of the type disclosed herein for the preparation of IM-HIPS (e.g., the first reaction mixture) comprises one or more free radical initiators. Such free radical initiators may function as a source of free radicals that enable the polymerization of styrene. In one embodiment, any initiator capable of forming free radicals that promote the polymerization of styrene may be used. Such free radical initiators include, for example, organic peroxides without limitation. Examples of organic peroxides suitable for use in this disclosure include, without limitation, diacyl peroxides, peroxydicarbonates, monoperoxycarbonates, peroxyketals, peroxyesters, dialkyl peroxides, hydroperoxides, or any combination thereof.

[0036] In one embodiment, the level of free radical initiator in the reaction is provided as active oxygen in parts per million (ppm). In one embodiment, the level of active oxygen in the initiated reaction for the production of IM-HIPS is: about 20 ppm to about 80 ppm, alternatively about 20 ppm to about 60 ppm, alternatively about 30 ppm to about 60 ppm. As understood by a person skilled in the art, the selection of the initiator and the effective amount will depend on numerous factors (e.g., temperature, reaction time) and may be selected by a person skilled in the art to meet the desired requirements of the process.

[0037] In one embodiment, any mixture applied to the polymerization conditions of the type disclosed herein for the preparation of IM-HIPS (e.g., the first reaction mixture) comprises a conjugated diene monomer as an elastomer (rubber). Examples of conjugated diene monomers suitable for use in this disclosure include, without limitation: 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 2-methyl-1,3-butadiene, and 2-chloro-1,3-butadiene.

[0038] In one embodiment, the elastomer comprises an aliphatic conjugated diene monomer. Without limitation, examples of aliphatic conjugated diene monomers suitable for use in this disclosure include C4 to C9 dienes such as butadiene monomer. Copolymers or blends of diene monomers may also be used. Similarly, mixtures or blends of one or more elastomers may be used. In one embodiment, the elastomer comprises a homopolymer of the diene monomer, and alternatively, the elastomer comprises polybutadiene. In one embodiment, the elastomer may be present in any mixture applied to the polymerization conditions of the type disclosed herein for the manufacture of IM-HIPS in an amount of at least about 1 wt%, alternatively about 6 wt% to about 10 wt%, alternatively about 6 wt%, about 7 wt%, about 8 wt%, about 9 wt%, or about 10 wt%, alternatively about 8 wt% to about 9 wt%, alternatively about 8.3 wt% to about 8.7 wt%, or alternatively about 8.5 wt%, based on the total weight of the mixture.

[0039] In one embodiment, IM-HIPS may also contain additives to impart desired physical properties, such as increased gloss or color. These additives may be introduced at any appropriate time during the manufacture of IM-HIPS. Examples of additives include, without limitation, chain transfer agents, talc, antioxidants, UV stabilizers, lubricants, mineral oils, plasticizers, etc. The aforementioned additives may be used alone or in combination to form various formulations of IM-HIPS. For example, stabilizers or stabilizing agents may help protect IM-HIPS from degradation caused by excessive temperature and / or UV exposure. These additives may be included alone or in combination in amounts effective for imparting the desired properties. Effective amounts of additives and processes for incorporating these additives into the polymer composition are known to those skilled in the art.

[0040] In one embodiment, the IM-HIPS of the present disclosure is characterized by a swelling index of about 5% to about 30%, alternatively about 5% to about 15%, or alternatively about 10% to about 15%. The swelling index can be used to measure the degree of bonding (crosslinking) between elastomer molecules (e.g., polybutadiene). The swelling index can be determined by taking the ratio between the mass of the wet gel and the mass of the dry gel, as determined according to ASTM D3616.

[0041] In one embodiment, the IM-HIPS of the present disclosure is characterized by a gel content of about 10% to about 50%, alternatively about 5% to about 30%, or alternatively about 15% to about 25%. The gel content, which indicates the degree of grafting, i.e., the amount of polystyrene grafted onto the rubber, is determined by shaking 1 g of IM-HIPS in 20 ml of toluene at room temperature and then centrifuging the whole to separate the toluene-insoluble gel from the remainder.

[0042] In one embodiment, the IM-HIPS of the type disclosed herein has: a rubber particle size (RPS) in the range of about 1 micron to about 10 microns, alternatively about 1 micron to about 8 microns, or alternatively about 1 micron to about 5 microns, and a rubber particle size distribution (i.e., RPSD or span) of less than about 1.5, alternatively less than about 1.3, or alternatively about 1.0 to about 1.3. The RPS and span may be determined using any suitable method, such as, for example, the ASTM F577-78 Malvern Particle Size Analyzer. The RPS is measured in microns, whereas the span is a dimensionless number measuring the width of the distribution.

[0043] In one embodiment, the IM-HIPS of the type disclosed herein has a gel-to-rubber ratio in the range of about 1 to about 10, alternatively about 2 to about 5, or alternatively about 2 to about 3, determined by the ratio between the % gel and % rubber content used in the sample. The gel-to-rubber ratio indicates the amount of polystyrene present in the rubber phase (occluded inside rubber particles or attached to polybutadiene molecules).

[0044] In one embodiment, the IM-HIPS of the type disclosed herein has a rubber-phase volume fraction (RPVF) in the range of about 10% to about 50%, alternatively about 15% to about 35%, or alternatively about 20% to about 30%, determined by the volume percentage of the rubber phase in the sample.

[0045] The IM-HIPS of the present disclosure may be characterized by a structure having an elastomer dispersed in a polystyrene matrix, wherein each elastomer cell has multiple occlusions of polystyrene partially or completely trapped within the rubber cell. In one embodiment, these occlusions may be in a size range of about 0.1 micron to about 2.0 micron, alternatively about 0.1 micron to about 1 micron, or alternatively about 0.5 micron to about 1 micron, as determined by image analysis performed on an image obtained by scanning electron microscopy technology.

[0046] HIPS generated by the disclosed methodology may be useful in a variety of applications including, but not limited to, food packaging, office supplies, point-of-purchase markings and displays, household goods and consumer goods, building insulation, and cosmetic packaging.

[0047] Examples

[0048] Although the subject matter of this disclosure has been described generally, the following embodiments are provided as specific embodiments thereof and to demonstrate their practice and benefits. The embodiments are provided by way of example and are not intended to limit the specification or claims in any way.

[0049] Example 1

[0050] In the following experiments, batch polymerization was performed using the feed formulations listed in Table 1. The same feed formulation was used in all examples. All rubbers were dissolved in the feed solution prior to the experiment.

[0051] [Table 1]

[0052]

[0053] For batch reactions, determined volumes of reaction A (30 and 50 ml) were collected after phase inversion and added to the feed for reaction B. Then, reaction B was initiated and continued until the conversion rate reached 70% and the material volatilized, and the properties of the polymer were tested. The temperature profile used during the reaction was: 120°C for 30 minutes, then 135°C for 180 minutes, and then the temperature was increased to 150°C until 70% solid was reached.

[0054] Polymer samples were collected from the second reaction (i.e., reaction B) in an aluminum pan. The aluminum pan was placed in a vacuum oven at 225°C for 60 minutes to remove all unreacted styrene and solvent. The properties of the volatilized samples were tested. The analysis results for these samples, such as expansion index, particle size, and recirculation amount, are listed in Table 2.

[0055] [Table 2]

[0056]

[0057] The results of this reaction show a slight change in terms of the expansion index. On the other hand, the rubber particles showed a tendency to increase in size as the recirculation amount increased from 30 ml to 50 ml.

[0058] Scanning transmission electron microscopy (STEM) collected images of the polymer at 3000X and 5000X magnifications (see Fig. 3). Rubber particles appear as a darker phase. Using image analysis, the diameters of the rubber particles and occlusions, as well as the volume fraction of rubber particles (RPVF), were measured. In the STEM images (Fig. 3), it appears that more uniform occlusions are obtained due to the presence of the grafted copolymer. In the case of reaction B, to which 50 ml was transferred, the effect on the occlusion morphology was more pronounced.

[0059] Example 2

[0060] In the following experiments, the production of IM-HIPS of the type disclosed herein was evaluated in a continuous process using CSTR units and the feed formulations listed in Table 1. For the purpose of improving stability and promoting the formation of more uniform rubber particles, laboratory experiments conducted in a continuous process investigated the introduction of grafted copolymers during rubber particle formation. During these experiments, two different strategies were evaluated: (1) a reaction mixture collected from a previous reaction introduced into the feed of a second reaction, and (2) a recirculation loop between two CSTR reactors.

[0061] The CSTR unit used consisted of two CSTR-type reactors connected by metal piping to which the feed was continuously added at a fixed rate. Refer to Fig. 2 for a schematic diagram of the reactor system. The flow rate used was maintained at 6 g / min. The reactor volumes were maintained constant at 200 ml in the first reactor and 600 ml in the second reactor. The temperatures were maintained at 120°C and 135°C for the first and second reactors, respectively. A total rubber content of 7% was the specification after volatilization. Polymer samples were collected from the second reactor in an aluminum pan after 8 hours of continuous operation. The aluminum pan was placed overnight in a purge oven at 135°C to complete 70% conversion. The samples were then placed in a vacuum oven at 225°C for 60 minutes to remove all styrene and solvent residues. The volatilized samples were then tested for morphology and physical properties. The formed blockages and rubber particles were quantified by analyzing morphological images captured by STEM.

[0062] For the first strategy, the laboratory reaction was completed by collecting the determined volume of the reaction immediately after phase inversion to be used as the feed for the subsequent polymerization reaction. From the analysis results in Table 3, it was noted that while particle size tended to increase in the reaction using 15% of the material in the feed, the opposite effect was observed in the reaction using 25% of the material in the feed. Although the grafted copolymer in HIPS is necessary to stabilize the interphase between the PS phase and the PB phase, a high level of grafting copolymer would also lead to smaller rubber particle sizes, which was estimated to have occurred in the experiment using 25% recycled material.

[0063] [Table 3]

[0064]

[0065] In the experiment based on Strategy 2, ratios of 5% and 10% were used for the recirculation amount at a unit flow rate of 6 g / min. The reaction was monitored throughout the experiment by measuring % solids and RPS. Once the reaction reached a steady state, the material was collected and finished in an oven with a target final solid content of 70%. The analysis results showed that the RPS decreased as the recirculation amount increased. These results are shown in Table 4. Additionally, the span value decreased, indicating a more uniform distribution of rubber particle sizes.

[0066] [Table 4]

[0067]

[0068] STEM analysis was completed to understand the influence on sample morphology. STEM images confirmed Malvern data, showing that RPS values ​​and spans decreased as the recirculation amount increased. In the STEM images, it can be observed that the rubber particles become more uniform as the recirculation amount increases. This effect promotes progressively smaller rubber particles as a result of a larger amount of grafted copolymer present during phase inversion, which requires more PS-PB intermediate phases. Additionally, it appears that the occlusion morphology was also affected as the rubber particle size decreased.

[0069] To quantify the effect of recirculation flow on sample morphology, STEM images were analyzed (see Fig. 4). A summary of the data collected in this analysis is shown in Table 5, which confirmed a decrease in rubber particle size and clog length with an increase in recirculation %. On the other hand, a decrease in standard deviation was also observed, indicating a narrower particle size distribution. This effect is more pronounced when the clog size decreases from 0.460 to 0.065.

[0070] [Table 5]

[0071]

[0072] These experiments demonstrate that grafted copolymers grown after phase inversion can be used to generate a more uniform rubber particle size distribution. Since more uniform rubber particles can be observed as the amount of recirculation increases, a correlation between a narrower rubber particle size distribution and a higher recirculation percentage was supported by STEM images. This effect is believed to promote smaller rubber particles as a result of the larger amount of grafted copolymer present during phase inversion, which requires more PS-PB intermediate phases. A similar effect was observed in the case of occlusions.

[0073] Additional disclosures

[0074] A first embodiment is a process for manufacturing high-impact polystyrene, comprising the steps of: introducing a partially polymerized mixture comprising one or more vinyl aromatic monomers, an elastomer, and a reacted vinyl aromatic monomer into a reactor, wherein the partially polymerized mixture does not undergo phase inversion; polymerizing the partially polymerized mixture in the reactor to a phase inversion point to form a phase-inverted mixture; releasing at least a portion of the phase-inverted mixture to another reactor; and recovering a portion of the phase-inverted mixture comprising high-impact polystyrene.

[0075] A second embodiment is a process for manufacturing high-impact polystyrene, comprising the steps of: introducing a partially polymerized mixture comprising one or more vinyl aromatic monomers, an elastomer, and a reacted vinyl aromatic monomer into a reactor, wherein the partially polymerized mixture does not undergo phase inversion; polymerizing the partially polymerized mixture in the reactor to a phase inversion point to form a phase-inverted mixture; introducing a portion of the phase-inverted mixture into another reactor; and recovering another portion of the phase-inverted mixture comprising high-impact polystyrene.

[0076] A third embodiment is a process for manufacturing high-impact polystyrene, wherein, in the first or second embodiment, the vinyl aromatic monomer is: styrene, substituted styrene, unsubstituted styrene, or any combination thereof.

[0077] A fourth embodiment is a process for manufacturing high-impact polystyrene, wherein, in any one of the first to third embodiments, the elastomer is a polymer of butadiene.

[0078] A fifth embodiment is a process for manufacturing high-impact polystyrene, wherein, in any one of the first to fourth embodiments, the first reaction mixture further comprises: a free radical initiator, a chain transfer agent, or any combination thereof.

[0079] A sixth embodiment is a process for manufacturing high-impact polystyrene, wherein, in any one of the first to fifth embodiments, the reactor is: a continuous stirred tank reactor, a plug flow reactor, or any combination thereof.

[0080] The seventh embodiment is a process for manufacturing high-impact polystyrene, wherein, in any one of the first to sixth embodiments, at least a portion of the reacted mixture is transferred from the outlet of one reactor to the inlet of another reactor.

[0081] The eighth embodiment is a process for manufacturing high-impact polystyrene, wherein, in the seventh embodiment, at least a portion of the reacted mixture is transferred at a rate ranging from about 1% to about 20% of the first reactor volume per minute.

[0082] The ninth embodiment is a process for manufacturing high-impact polystyrene, wherein, in any one of the first to eighth embodiments, at least a portion of the reacted mixture is transported as a continuous discharge.

[0083] The 10th embodiment is a process for manufacturing high-impact polystyrene, wherein, in any one of the 1st to 9th embodiments, the high-impact polystyrene has a swelling index of about 5% to about 30%.

[0084] The 11th embodiment is a process for manufacturing high-impact polystyrene, wherein, in any one of the 1st to 10th embodiments, the high-impact polystyrene has a rubber particle size of about 1 micron to about 10 microns.

[0085] The 12th embodiment is a manufacturing process for high-impact polystyrene in any one of the 1st to 11th embodiments, wherein the high-impact polystyrene has a rubber particle size distribution of about 1.5 or less.

[0086] The 13th embodiment is a process for manufacturing high-impact polystyrene, wherein, in any one of the 1st to 12th embodiments, the high-impact polystyrene has occlusions of a size ranging from about 0.1 micron to about 2 microns.

[0087] A 14th embodiment is a process for manufacturing high-impact polystyrene, comprising the steps of: introducing a partially polymerized mixture comprising one or more vinyl aromatic monomers, an elastomer, and a reacted vinyl aromatic monomer into a first reactor, wherein the partially polymerized mixture does not undergo phase inversion; polymerizing the partially polymerized mixture in the first reactor to a phase inversion point to form a phase-inverted mixture; introducing a portion of the phase-inverted mixture from the first reactor into a second reactor, wherein the second reactor is positioned downstream of the first reactor; and recovering another portion of the phase-inverted mixture, wherein the other portion of the recovered phase-inverted mixture comprises high-impact polystyrene.

[0088] A 15th embodiment is a high-impact polystyrene reactor system comprising: (a) a first continuous stirred tank reactor having an inlet configured to receive (i) one or more vinyl aromatic monomers, (ii) an elastomer, and (iii) a free radical initiator, and (b) an outlet configured to transfer a first reactor effluent; (a) a second continuous stirred tank reactor fluidly communicating with the outlet of the first continuous stirred tank reactor, having an inlet configured to receive (i) a portion of the first reactor effluent from the first continuous stirred tank reactor, (ii) one or more vinyl aromatic monomers, (iii) an elastomer, and (iv) a free radical initiator, and (b) an outlet configured to transfer a portion of the second reactor effluent comprising high-impact polystyrene; A high-impact polystyrene reactor system comprising a conduit for establishing a recirculation stream between the second reactor and the first reactor, wherein the recirculation stream comprises another portion of the effluent from the second reactor.

[0089] The 16th embodiment is a high-impact polystyrene reactor system in which, in the 15th embodiment, the first continuous stirred tank reactor is arranged vertically such that the inlet is at the top and the outlet is at the bottom.

[0090] The 17th embodiment is a high-impact polystyrene reactor system, wherein in any one of the 15th to 16th embodiments, the vinyl aromatic monomer is: styrene, substituted styrene, unsubstituted styrene, or any combination thereof.

[0091] The 18th embodiment is a high-impact polystyrene reactor system in any one of the 15th to 17th embodiments, wherein the elastomer is a polymer of butadiene.

[0092] The 19th embodiment is a high-impact polystyrene reactor system, wherein, in any one of the 15 to 18 embodiments, the recirculation stream from the second continuous stirred tank reactor is transferred to the first continuous stirred tank reactor at a rate ranging from about 0.1% per minute of the volume of the second continuous stirred tank reactor to about 20% per minute of the volume of the second continuous stirred tank reactor.

[0093] The 20th embodiment is a high-impact polystyrene reactor system in any one of the 15th to 19th embodiments, wherein the high-impact polystyrene has a rubber particle size of about 1 micron to about 10 microns.

[0094] The 21st embodiment is a high-impact polystyrene reactor system in any one of the 15th to 20th embodiments, wherein the high-impact polystyrene has a rubber particle size distribution of about 1.5 or less.

[0095] The 22nd embodiment is a high-impact polystyrene reactor system in any one of the 15th to 21st embodiments, wherein the high-impact polystyrene has occlusions of a size ranging from about 0.1 micron to about 2 microns.

[0096] A 23rd embodiment is a high-impact polystyrene reactor system comprising, in any one of the 15th to 22nd embodiments, one or more additional linear flow reactors for receiving at least a portion of the effluent from the second reactor.

[0097] Although aspects of the subject matter disclosed herein have been illustrated and described, modifications thereto may be made by a person skilled in the art without departing from the spirit and teachings of the subject matter disclosed herein. The aspects described herein are illustrative only and are not intended to be limiting. Many variations and modifications of the subject matter disclosed herein are possible and are within the scope of the subject matter disclosed herein. Where numerical ranges or limitations are explicitly mentioned, such explicit ranges or limitations should be understood to include repetitive ranges or limitations of similar size falling within the explicitly mentioned ranges or limitations (e.g., 1 to 10 includes 2, 3, 4, etc.; and greater than 0.10 includes 0.11, 0.12, 0.13, etc.). The use of the term “optional” in relation to any component of the claim is intended to mean that the component is required or alternatively not required. Both alternatives are intended to be within the scope of the claims. For example, the use of broader terms such as comprises, includes, having, etc., should be understood as providing support for narrower terms such as, for example, constituted, essentially constituted, substantially constituted, etc.

[0098] Accordingly, the scope of protection is not limited by the description provided above, but is limited only by the following claims, which include all equivalents of the subject matter of the claims. Each and all claims are incorporated herein as an embodiment of the invention. Accordingly, the claims are additional descriptions and additions to the embodiments of the subject matter disclosed herein. The discussion of reference in this specification does not imply that any reference to the subject matter currently disclosed, particularly any reference that may have a publication date after the priority date of this application, constitutes prior art. All disclosures of patents, patent applications, and publications cited herein are incorporated by reference to the extent that they provide exemplary, procedural, or other details that supplement what is specified herein.

Claims

Claim 1 A process for manufacturing high-impact polystyrene, comprising the steps of: introducing a partially polymerized mixture comprising one or more vinyl aromatic monomers, an elastomer, and a reacted vinyl aromatic monomer into a reactor, wherein the partially polymerized mixture has not undergone phase inversion; polymerizing the partially polymerized mixture in the reactor to a phase inversion point to form a phase-inverted mixture; recovering a portion of the phase-inverted mixture comprising high-impact polystyrene from the reactor; and introducing at least a portion of the phase-inverted mixture into another reactor. Claim 2 A process for manufacturing high-impact polystyrene, wherein the vinyl aromatic monomer is: styrene, substituted styrene, unsubstituted styrene, or any combination thereof. Claim 3 In claim 1, the manufacturing process of high-impact polystyrene, wherein the elastomer is a polymer of butadiene. Claim 4 A process for manufacturing high-impact polystyrene, wherein the partially polymerized mixture in claim 1 further comprises: a free radical initiator, a chain transfer agent, or any combination thereof. Claim 5 In claim 1, the reactor is: a continuous stirred tank reactor, a plug flow reactor, or any combination thereof, for the production process of high-impact polystyrene. Claim 6 A process for manufacturing high-impact polystyrene according to claim 1, wherein at least a portion of the reacted mixture is transferred from the discharge port of a reactor to the inlet port of another reactor. Claim 7 A process for manufacturing high-impact polystyrene according to claim 6, wherein at least a portion of the reacted mixture is transferred at a rate ranging from 1% to 20% of the first reactor volume per minute. Claim 8 A process for manufacturing high-impact polystyrene according to claim 1, wherein at least a portion of the reacted mixture is transported as a continuous discharge. Claim 9 A manufacturing process for high-impact polystyrene according to claim 1, wherein the high-impact polystyrene has a swelling index of 5% to 30%. Claim 10 In claim 1, the high-impact polystyrene is a manufacturing process of high-impact polystyrene having a rubber particle size of 1 micron to 10 microns. Claim 11 In claim 1, the manufacturing process of high-impact polystyrene having a rubber particle size distribution of less than 1.

5. Claim 12 A manufacturing process for high-impact polystyrene according to claim 1, wherein the high-impact polystyrene has occlusions of a size ranging from 0.1 micron to 2 microns. Claim 13 A process for manufacturing high-impact polystyrene, comprising: a step of introducing a partially polymerized mixture comprising one or more vinyl aromatic monomers, an elastomer, and a reacted vinyl aromatic monomer into a first reactor, wherein the partially polymerized mixture has not undergone phase inversion; a step of polymerizing the partially polymerized mixture in the first reactor to a phase inversion point to form a phase-inverted mixture; a step of introducing a portion of the phase-inverted mixture from the first reactor into a second reactor, wherein the second reactor is positioned downstream of the first reactor; and a step of recovering another portion of the phase-inverted mixture, wherein the other portion of the recovered phase-inverted mixture comprises high-impact polystyrene. Claim 14 A high-impact polystyrene reactor system comprising: (a) a first continuous stirred tank reactor having an inlet configured to receive (i) one or more vinyl aromatic monomers, (ii) an elastomer, and (iii) a free radical initiator, and (b) an outlet configured to transfer a first reactor effluent; (a) a second continuous stirred tank reactor having a fluid connection with the outlet of the first continuous stirred tank reactor, (i) a portion of the first reactor effluent from the first continuous stirred tank reactor, (ii) one or more vinyl aromatic monomers, (iii) an elastomer, and (iv) a free radical initiator, and an inlet configured to receive (b) a portion of the second reactor effluent comprising high-impact polystyrene; and a conduit for establishing a recirculation stream between the second reactor and the first reactor, wherein the recirculation stream comprises another portion of the second reactor effluent. Claim 15 In claim 14, the above-mentioned first continuous stirred tank reactor is a high-impact polystyrene reactor system arranged vertically such that the inlet is at the top and the outlet is at the bottom. Claim 16 In paragraph 14, the vinyl aromatic monomer is: styrene, substituted styrene, unsubstituted styrene, or any combination thereof, a high-impact polystyrene reactor system. Claim 17 In paragraph 14, the above elastomer is a polymer of butadiene, a high-impact polystyrene reactor system. Claim 18 A high-impact polystyrene reactor system, wherein the recirculation stream from the second continuous stirred tank reactor is transferred to the first continuous stirred tank reactor at a rate ranging from 0.1% per minute of the volume of the second continuous stirred tank reactor to 20% per minute of the volume of the second continuous stirred tank reactor. Claim 19 In claim 14, the high-impact polystyrene is a high-impact polystyrene reactor system having a rubber particle size of 1 micron to 10 microns. Claim 20 In claim 14, the high-impact polystyrene is a high-impact polystyrene reactor system having a rubber particle size distribution of less than 1.

5. Claim 21 In claim 14, the high-impact polystyrene is a high-impact polystyrene reactor system having occlusions of a size ranging from 0.1 micron to 2 microns. Claim 22 A high-impact polystyrene reactor system according to claim 14, further comprising one or more additional linear flow reactors for receiving at least a portion of the effluent from the second reactor.

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