Process for producing high impact polystyrene with improved rubber morphology

Abstract

A method for producing high impact polystyrene comprises introducing a partially polymerized mixture into a reactor, the mixture comprising at least one vinyl aromatic monomer, an elastomer and reacted vinyl aromatic monomer, wherein the partially polymerized mixture has not undergone phase inversion; polymerizing the partially polymerized mixture to a phase inversion point in the reactor to form a phase inverted mixture; recovering a portion of the phase inverted mixture from the reactor, wherein the phase inverted mixture comprises high impact polystyrene; and introducing another portion of the phase inverted mixture into another reactor.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 010,498, filed on April 15, 2022, entitled “Methods for Production of High Impact Polystyrene Having an Improved Rubber Morphology,” which is incorporated herein by reference in its entirety.

[0003] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0004] none. Technical Field

[0005] The present invention relates generally to the production of high impact polystyrene and, more particularly, to the production of high impact polystyrene having improved rubbery morphology. Background Art

[0006] Elastomer-reinforced polymers of monovinylidene aromatic compounds such as styrene, alpha-methylstyrene, and ring-substituted styrenes have found widespread commercial use. For example, elastomer-reinforced styrene polymers having discrete particles of a crosslinked elastomer dispersed in a styrene polymer matrix are useful in a range of applications including food packaging, office supplies, point-of-sale signs and displays, household and consumer goods, building insulation, and cosmetic packaging. Such elastomer-reinforced polymers are often referred to as high impact polystyrene (HIPS).

[0007] The mechanical properties of HIPS and its potential applications depend to a large extent on whether the elastomer (rubber) particles have an ideal morphological structure. In this article, the terms "elastomer" and "rubber" are used interchangeably in the art. For example, an undesirable mixed morphology may be characterized by a wide distribution of rubber particle sizes and a significant level of small rubber particles with an average diameter of less than 1 micron in the HIPS. Small rubber particles with mixed morphologies (such as linear or labyrinth morphologies) may result in low rubber utilization. In addition, HIPS with small rubber particle morphology characteristics generally exhibits poor toughness and low values ​​of elongation at fail. Therefore, a method is needed to produce HIPS with improved rubber morphology, as shown by a narrow rubber particle size distribution. Summary of the invention

[0008] The present invention discloses a method for producing high-impact polystyrene, comprising introducing a partially polymerized mixture into a reactor, wherein the mixture comprises at least one vinyl aromatic monomer, an elastomer and a reacted vinyl aromatic monomer, 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 from the reactor, wherein the phase-inverted mixture comprises high-impact polystyrene; and introducing another portion of the phase-inverted mixture into another reactor.

[0009] The present invention also discloses a method for producing high-impact polystyrene, comprising introducing a partially polymerized mixture into a first reactor, wherein the mixture comprises at least one vinyl aromatic monomer, an elastomer and a reacted vinyl aromatic monomer, 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 disposed downstream of the first reactor, and recovering another portion of the phase-inverted mixture, wherein the recovered another portion of the phase-inverted mixture comprises high-impact polystyrene.

[0010] The present invention also discloses a high-impact polystyrene reactor system, comprising a first continuously stirred tank reactor, the reactor having (a) an inlet configured to receive (i) at least one vinyl aromatic monomer, (ii) an elastomer, (iii) a free radical initiator and (b) an outlet configured to transport the first reactor effluent; a second continuously stirred tank reactor, having (a) an inlet fluidly connected to the outlet of the first continuously stirred tank reactor, configured to receive (i) a portion of the first effluent from the first continuously 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 transport a portion of the second reactor effluent containing high-impact polystyrene; and (c) a conduit for establishing a recycle stream between the second reactor and the first reactor, wherein the recycle stream comprises another portion of the second reactor effluent.

[0011] The foregoing describes the features and technical advantages of the subject matter of the present invention in a fairly broad manner so that the detailed description below can be better understood. Other features and advantages of the subject matter of the present invention that constitute the object of the claims of the present invention will be described below. It will be appreciated by those skilled in the art that the disclosed concepts and specific aspects can be easily used as the basis for modifying or designing other structures to achieve the same purpose of the present invention. It will also be appreciated by those skilled in the art that such equivalent structures do not depart from the spirit and scope of the subject matter of the claims of the present invention set forth in the appended claims.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to describe in detail various aspects of the present subject matter, reference will now be made to the accompanying drawings, in which:

[0014] Figure 1 It is a schematic diagram of the HIPS polymerization reaction.

[0015] Figure 2 is a schematic diagram of a polymerization reactor system.

[0016] Figure 3 and Figure 4 are scanning transmission electron micrographs of the samples of Examples 1 and 2. DETAILED DESCRIPTION

[0017] Disclosed herein is a method of producing HIPS having a rubber particle size distribution (RPSD or span) equal to or less than about 1.5. Such HIPS having a narrow rubber particle size distribution is referred to as an improved morphology HIPS, referred to herein as IM-HIPS.

[0018] The production of HIPS generally involves the dissolution of a rubber (e.g., polybutadiene elastomer (PB)) in styrene and subsequent polymerization. During the polymerization process, phase separation based on the immiscibility of polystyrene (PS) and polybutadiene (PB) occurs in two stages. Initially, PB forms the main or continuous phase, in which styrene is dispersed. Figure 1 As shown in Figure A, as the reaction begins, PS droplets 10 (darker circles) are formed and dispersed in the elastomer solution 20 of PB and styrene monomers (lighter background). Figure 1 As shown in B, as the reaction proceeds and the amount of polystyrene continues to increase, a morphological transformation or phase inversion occurs, where PS forms a continuous phase, and PB and styrene monomers form a discontinuous phase.

[0019] like Figure 1 As shown by reference numeral 30 (brighter circle) in C, the phase transition leads to the formation of a discontinuous phase containing complex elastomer particles, wherein the elastomer exists in the form of PB membranes surrounding occluded domains of PS.

[0020] Shear stirring can be used to induce phase inversion. Polymerizations performed in a rheometer showed that 10-30 seconds -1 The shear rate is sufficient to cause the two phases to reverse.

[0021] The polymerization of HIPS can be represented by the chemical equation given in Scheme 1:

[0022]

[0023] This reaction describes the formation of polystyrene chains in the presence of PB, leading to the production of grafted polybutadiene PS, which is a factor affecting the morphology of HIPS.

[0024] In one aspect, a method for producing IM-HIPS comprises a first reactor, into which a first reaction mixture is introduced, which comprises styrene monomer, elastomer particles and a free radical initiator, each of which will be described in detail below. The first reaction mixture can then be polymerized in the first reactor to form a reaction mixture. For example, based on the total amount of solids in the reactor, the first reaction mixture can be polymerized into a solid percentage of 1% to about 25%, or from about 1% to about 10%, or from about 5% to about 10%. In one aspect, the reacted mixture mainly comprises unreacted styrene, rubber and polystyrene.

[0025] The method for producing IM-HIPS of the present invention also comprises introducing at least a portion of reacted mixture into the second reactor as a part of raw material. In some aspects, reacted mixture is intermittently introduced into the second reactor, and based on the cumulative volume of the first reactor, its introduction amount is about 1 volume % (vol.%) to about 20 volume %, or about 1 volume % to about 15 volume %, or about 1 volume % to about 5 volume %. In another aspect, reacted mixture is continuously introduced into the second reactor with unit flow rate, and based on the cumulative volume of the first reactor, described flow rate is about 1 volume % to about 20 volume %, or about 1 volume % to about 15 volume %, or about 1 volume % to about 5 volume %, and can set time to meet some users or process targets. For example, based on the first reactor volume, at least a portion of reacted mixture can be transported at a speed of about 1% per minute to about 20% per minute.

[0026] In one aspect, the feedstock is polymerized in the second reactor to at least a phase inversion point to produce a reactor effluent. The reactor effluent may comprise unreacted styrene, polystyrene, polystyrene grafted rubber, and high impact polystyrene.

[0027] In one aspect, method of the present invention is included in setting up recycle stream between first and second reactor, and wherein recycle stream comprises part of reactor effluent.Set up recycle stream between first reactor and second reactor, make reactor effluent introduce first reactor from second reactor.In some respects, reactor effluent is intermittently introduced into first reactor, and based on the cumulative volume of second reactor, its introduction amount is about 0.1 volume % to about 20 volume %, or about 0.1 volume % to about 1 volume %, or about 0.1 volume % to about 0.5 volume %.In another aspect, reactor effluent is continuously introduced into first reactor with unit flow rate, and based on the cumulative volume of second reactor, described flow rate is about 0.1 volume % to about 20 volume %, or about 0.1 volume % to about 1 volume %, or about 0.1 volume % to about 0.5 volume %, and setting time is to meet some users or process targets.

[0028] In some aspects of the invention, IM-HIPS are produced in a staged process. For ease of reference, the process described herein may be numerically ordered by stage (i.e., stage 1, stage 2), but it is not intended to limit the performance of the activities of each stage to a particular order. For example, one or more activities described for a stage may be performed simultaneously with one or more activities of another stage, regardless of whether the "another stage" is numerically designated as being after or before the "particular stage." Modifications in the timing of activities performed at any particular stage may be made by one of ordinary skill in the art with the aid of the present invention.

[0029] In one aspect of the invention, the method for producing IM-HIPS has a first stage (i.e., stage 1), comprising introducing a first reaction mixture into a first reactor, wherein the first reaction mixture comprises styrene monomer, elastomer particles, and a free radical initiator. Then, the first reaction mixture can be subjected to conditions suitable for polymerization of the first reaction mixture in the first reactor. For example, the first reactor can be heated to a temperature of about 100°C to about 150°C, or about 110°C to about 135°C, or about 115°C to about 120°C, for a duration of about 30 minutes to about 120 minutes, or about 30 minutes to about 90 minutes, or about 30 minutes to about 60 minutes. In one aspect, stage 1 comprises polymerizing the first reaction mixture to a point before phase inversion to produce a reaction mixture having a solid content of about 1% to about 25%, or about 1% to about 15% or about 5% to about 10%, based on the total amount of material in the reactor.

[0030] In one aspect of the invention, the method comprises a second stage (stage 2), wherein the reacted mixture is used as a raw material for a second reactor. In this regard, the reacted mixture is transported from the first reactor to the second reactor using any suitable method. The reacted mixture can be continuously transported to the second reactor at any suitable speed. In one aspect, the reacted mixture in the second reactor is subjected to conditions suitable for continued polymerization of the reacted mixture. In some aspects, the polymerization conditions in the second reactor are the same as those in the first reactor, or the polymerization conditions in the second reactor are different from those 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, or about 120°C to about 145°C, or about 125°C to about 130°C, and a duration of about 90 minutes to about 180 minutes, or about 90 minutes to about 150 minutes, or about 90 minutes to about 120 minutes. In these aspects, the reacted mixture can be polymerized until a reactor effluent is formed in the second reactor comprising at least 50% solids, or at least 40% solids, or at least 30% solids, based on the total amount of material in the reactor.

[0031] In one aspect of the invention, the third stage (i.e., stage 3) of the process includes establishing a recycle stream between the first and second reactors. For example, a portion of the reactor effluent containing about 10% to about 50% solids can be introduced into the first reactor at a rate of about 0.1% by volume to about 20% by volume, or about 0.1% by volume to about 1% by volume, or about 0.1% by volume to about 0.5% by volume based on the total volume of the second reactor, and the time is set to meet some users or process goals. In one aspect, based on the total amount of materials in the reactor, the solid percentage formed in the second reactor can reach about 5% to about 50%, or about 10% to about 40%, or about 15% to about 30% at any time to establish the recycle stream. In these aspects, in the third stage, the preparation method of IM-HIPS of the present invention includes that the first and second reactors are at least connected by a first conduit and a second conduit fluid, wherein the first conduit transports the reacted mixture from the first reactor to the second reactor, and the second conduit transports the reactor effluent from the second reactor to the first reactor.

[0032] In one aspect, the method for preparing IM-HIPS can comprise additional stages (e.g., stage 3+x, where x≥1), wherein the reactor effluent from the second reactor is sent to one or more additional reactors for further polymerization and / or processing to meet the desired goals of some user and / or application.

[0033] In another aspect, a method for producing high impact polystyrene comprises introducing a partially polymerized mixture into a reactor, the mixture comprising at least one vinyl aromatic monomer, an elastomer, and a reacted vinyl aromatic monomer, wherein the partially polymerized mixture does not undergo phase inversion. The method may further comprise polymerizing the partially polymerized mixture to a phase inversion point in the reactor 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 aspect, the method further comprises recovering a portion of the phase-inverted mixture from the reactor, wherein the phase-inverted mixture comprises high impact polystyrene, and introducing another portion of the phase-inverted mixture into another reactor. In one aspect, the reactor and the other reactor are reactors of the same type. Alternatively, the reactor and the other reactor are reactors of different types.

[0034] In some aspects, where the reaction mixture is introduced continuously, the first reactor can be in fluid communication with the second reactor. For example, the first reactor can include a reactor having an inlet configured to receive the first reaction mixture and an outlet configured to deliver the reacted mixture to the inlet of the second reactor. A recycle flow can be established between the outlet of the second reactor and the inlet of the first reactor. This Figure 2 A schematic description is given in FIG. Figure 2 , describes a partial reactor system 100 for preparing IM-HIPS, which has a first reactor 10 and a second reactor 20. The first reaction mixture can be transported to the reactor 10 via pipeline 5, where it is subjected to polymerization conditions disclosed herein, and then a reacted mixture is produced. The reacted mixture can be transported from the first reactor 10 to the reactor 20 via pipeline 15, where it is also subjected to polymerization conditions of the type disclosed herein, and then a reactor effluent is produced. A portion of the reactor effluent can be transported from the second reactor 20 to the first reactor 10 via pipeline 25, i.e., a recycle stream is established. In addition, the reactor effluent can be transported to other downstream processes via pipeline 30.

[0035] Although the lines used to transport materials (e.g., reactor effluent) are depicted at specific locations on the reactor (e.g., Figure 2 , pipeline 5 to reactor 10), but it is contemplated that these pipelines can be positioned as desired by a person skilled in the art to allow material to be delivered to any area of ​​the reactor. Figure 2 As shown, Figure 2The line 5 in the first reactor 10 allows the introduction of materials (e.g., the first reaction mixture) through the top of the first reactor 10. The lines allowing materials to enter and exit the reactor can be set anywhere in the reactor, so that materials (e.g., the first reaction mixture, reactor effluent) can be introduced / removed from any position in the reactor, as long as the position is compatible with the materials being transported and the equipment being used.

[0036] In one aspect, the first reactor (e.g., Figure 2 Reactor 10), a second reactor (e.g., Figure 2 The reactor 20) 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 by using any suitable stirring means, such as a rotary stirrer, a magnetic stirrer, bubbling or sparging an inert gas through a liquid phase. A CSTR can be operated as a batch process or a continuous process (e.g., reagents are periodically or continuously added to the CSTR and the reaction mixture is periodically or continuously removed from the CSTR).

[0037] In another aspect, the first reactor (e.g., Figure 2 The reactor 10 in the reactor), the second reactor (e.g., Figure 2 The reactor 20 in the plug flow reactor or both are plug flow reactors (PFR). The plug flow reactor herein refers to a reactor in which one or more fluid reagents are pumped through a pipeline or tube; the reagents chemically react while passing through the plug flow reactor, and a mixture containing the products is collected as the effluent of the reactor.

[0038] In another aspect of the invention, a reactor system suitable for use in the present invention comprises one or more CSTRs and one or more PFRs as needed to produce IM-HIPS of the type disclosed herein.

[0039] In one aspect, any mixture (e.g., the first reaction mixture) subjected to polymerization conditions of the type disclosed herein for producing IM-HIPS contains a vinylidene aromatic monomer, or styrene. Styrene, also known as vinylbenzene, vinylbenzene and phenylethylene, is an organic compound with a chemical formula of C8H8. Similar vinylidene aromatic monomers can replace styrene in whole or in part. The monomers include, but are not limited to, various substituted styrenes (e.g., α-methylstyrene), ring-substituted styrenes (e.g., p-methylstyrene), disubstituted styrenes and unsubstituted styrenes. In one aspect, based on the gross weight of the mixture, in any mixture subjected to polymerization conditions of the type disclosed herein for producing IM-HIPS, styrene monomers account for at least 70% by weight, or about 70% by weight to about 95% by weight, or about 85% by weight to about 95% by weight.

[0040] In one aspect, any mixture (such as the first reaction mixture) subjected to polymerization conditions of the type disclosed herein for producing IM-HIPS comprises at least one free radical initiator. The free radical initiator can be used as a source of free radicals to polymerize styrene. In one aspect, any initiator capable of forming free radicals and promoting the polymerization of styrene can be used. The free radical initiator includes, for example, but is not limited to, organic peroxides. Examples of organic peroxides suitable for use in the present invention include, but are not limited to, diacyl peroxides, peroxydicarbonates, monoperoxycarbonates, peroxyketals, peroxyesters, dialkyl peroxides, hydroperoxides, or any combination thereof.

[0041] In one aspect, the free radical initiator level in the reaction is expressed as active oxygen in parts per million (ppm). In one aspect, the active oxygen level in the disclosed reaction for producing IM-HIPS is from about 20 ppm to about 80 ppm, or from about 20 ppm to about 60 ppm, or from about 30 ppm to about 60 ppm. As will be appreciated by one of ordinary skill in the art, the choice of initiator and effective amount will depend on many factors (e.g., temperature, reaction time), and can be selected by one of ordinary skill in the art to meet the desired requirements of the process.

[0042] In one aspect, any mixture (e.g., the first reaction mixture) subjected to polymerization conditions of the type disclosed herein for producing IM-HIPS contains a conjugated diene monomer that is an elastomer (rubber). Examples of conjugated diene monomers suitable for use in the present invention include, but are not limited to, 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 2-methyl-1,3-butadiene, and 2-chloro-1,3-butadiene.

[0043] In one aspect, the elastomer comprises an aliphatic conjugated diene monomer. Examples of aliphatic conjugated diene monomers suitable for the present invention include but are not limited to C4 to C9 dienes, such as butadiene monomers. Blends or copolymers of diene monomers can also be used. Similarly, mixtures or blends of one or more elastomers can also be used. In one aspect, the elastomer comprises a homopolymer of a diene monomer, or the elastomer comprises polybutadiene. In one aspect, the elastomer can be present in any mixture subjected to polymerization conditions of the type disclosed herein for producing IM-HIPS, based on the gross weight of the mixture, and its content is equal to or greater than about 1% by weight, or about 6% by weight to about 10% by weight, or about 6% by weight, about 7% by weight, about 8% by weight, about 9% by weight, or about 10% by weight, or about 8% by weight to about 9% by weight, or from about 8.3% by weight to about 8.7% by weight, or about 8.5% by weight.

[0044] In one aspect, IM-HIPS may also include additives to provide desired physical properties, such as increasing gloss or color. The additives may be introduced at any appropriate time in the preparation of IM-HIPS. Examples of additives include, but are not limited to, chain transfer agents, talcum powder, antioxidants, UV stabilizers, lubricants, mineral oils, plasticizers, and the like. The above additives may be used alone or in combination to form various formulations of IM-HIPS. For example, stabilizers or stabilizing agents may be used to help protect IM-HIPS from degradation due to exposure to excessively high temperatures and / or ultraviolet rays. The additives may be used alone or in combination, and the amount used should be effective in providing the desired properties. Those skilled in the art are familiar with the effective amount of additives and methods for adding these additives to polymer compositions.

[0045] In one aspect, the IM-HIPS of the present invention is characterized by a swelling index of about 5% to about 30%, or about 5% to about 15%, or about 10% to about 15%. The swelling index can be used to measure the degree of bonding (crosslinking) between elastomeric molecules (e.g., polybutadiene). The swelling index can be determined by the mass ratio of the wet gel to the mass ratio of the dry gel, which is determined according to the ASTM D3616 standard.

[0046] In one aspect, the IM-HIPS of the present invention is characterized by a gel content of about 10% to about 50%, or about 5% to about 30%, or about 15% to about 25%. The gel content indicates the degree of grafting, i.e., the amount of polystyrene grafted onto the rubber, which 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.

[0047] In one aspect, the rubber particle size (RPS) of the IM-HIPS of the type disclosed herein is from about 1 micron to about 10 microns, or from about 1 micron to about 8 microns, or from about 1 micron to about 5 microns, and the rubber particle size distribution (i.e., RPSD or span) is less than about 1.5, or less than about 1.3, or from about 1.0 to about 1.3. The RPS and span can be determined using any suitable method, such as using an ASTM F577-78 Malvern particle size analyzer. The units of RPS are microns, while span is a dimensionless number that is a measure of the breadth of the distribution.

[0048] In one aspect, the gel: rubber ratio of IM-HIPS of the type disclosed herein is from about 1 to about 10, or from about 2 to about 5, or from about 2 to about 3, determined by the ratio between the gel % and rubber % content used in the sample. The gel to rubber ratio represents the amount of polystyrene present in the rubber phase (either embedded in the rubber particles or attached to the polybutadiene molecules).

[0049] In one aspect, IM-HIPS of the type disclosed herein have a rubber phase volume fraction (RPVF) ranging from about 10% to about 50%, or from about 15% to about 35%, or from about 20% to about 30%, as determined by the volume percentage of the rubber phase in the sample.

[0050] The IM-HIPS of the present invention is characterized by a structure having an elastomer dispersed in a polystyrene matrix, wherein each elastomer unit has a plurality of polystyrene embedding bodies, partially or completely trapped in the rubber unit. In one aspect, the embedding bodies may have a size of about 0.1 micron to about 2.0 microns, or about 0.1 micron to about 1 micron, or about 0.5 micron to about 1 micron, as determined by image analysis of images obtained by electron microscopy.

[0051] The HIPS produced by the disclosed method can be used in a variety of applications including, but not limited to, food packaging, office supplies, point-of-purchase signs and displays, household and consumer products, building insulation, and cosmetic packaging.

[0052] Example

[0053] After generally describing the subject matter of the present invention, the following examples are given as specific aspects thereof and demonstrate its practice and advantages. It should be understood that these examples are given in an illustrative manner and are not intended to limit the specification or claims in any way.

[0054] Example 1

[0055] In the following experiments, batch polymerization was carried out using the raw material formulation described in Table 1. The same raw material formulation was used in all examples. Before the experiments, all rubbers were dissolved in the raw material solution.

[0056] Table 1

[0057]

[0058] For the batch reactions, a certain volume of reactant A (30 and 50 ml) was collected after phase inversion and added to the feed of reaction B, which was then started and continued until a conversion of 70% was reached, the material was devolatilized and the polymer properties were tested. The temperature profile used during the reaction was as follows: 120°C for 30 minutes, then 135°C for 180 minutes, and then the temperature was increased to 150°C until a solid content of 70% was reached.

[0059] A polymer sample was collected from the second reaction (i.e., reaction B) in an aluminum pan. The pan was placed in a vacuum oven at 225°C for 60 minutes to remove all unreacted styrene and solvent. The properties of the devolatilized sample were tested. The analytical results of the sample, such as swelling index, particle size, and recycle amount, are listed in Table 2.

[0060] Table 2

[0061]

[0062] The results of these reactions show that there is little change in the swelling index. On the other hand, the particle size of the rubber tends to increase as the circulation volume increases from 30 ml to 50 ml.

[0063] Scanning transmission electron microscopy (STEM) images of the polymer were collected at 3000X and 5000X magnifications, i.e. Figure 3 The rubber particles appear as a darker phase. Image analysis was used to measure the rubber particle and embedded body diameters as well as the rubber particle volume fraction (RPVF). From the STEM images ( Figure 3 ) shows that the presence of the graft copolymer makes the embedded body more uniform. In the case of transferring 50 ml in reaction B, the effect on the embedded body morphology is more obvious.

[0064] Example 2

[0065] In the experiments described below, the production of IM-HIPS of the type disclosed herein was evaluated in a continuous process using a CSTR unit and the feed formulation described in Table 1. Laboratory experiments conducted in a continuous process investigated the introduction of a graft copolymer during the rubber particle formation process with the goal of improving its stability and promoting the formation of more uniform rubber particles. Two different strategies were evaluated in the experiments; (1) the introduction of the reaction mixture collected from the previous reaction into the feed of the second reaction; and (2) a recycle loop between two CSTR reactors.

[0066] The CSTR unit used consists of two CSTR type reactors connected by metal pipes to continuously add feed at a defined rate. See the schematic diagram of the reactor system for details. Figure 2. The flow rate used was maintained at 6 g / min. The reactor volumes remained unchanged, 200 ml for the first reactor and 600 ml for the second reactor. The temperatures of the first and second reactors were maintained at 120°C and 135°C, respectively. The total rubber content after devolatilization was 7%. After the reactors had been running continuously for 8 hours, polymer samples were collected from the second reactor into an aluminum pan. The aluminum pan was placed in a purge oven at 135°C overnight to achieve 70% conversion. The sample was then placed in a vacuum oven at 225°C for 60 minutes to remove all styrene and solvent residues. The devolatilized samples were then tested for morphology and physical properties. The embedded bodies and rubber particles formed were quantified by analyzing the morphological images taken by STEM.

[0067] In the case of the first strategy, laboratory reactions have been completed in which a certain volume of the reactants is collected immediately after the phase inversion and used as feed for subsequent polymerization reactions. From the analysis results (Table 3), it can be seen that when 15% of the material is added to the reaction, the particle size tends to increase, while when 25% of the material is added to the reaction, the opposite effect occurs. In HIPS, the graft copolymer is required to stabilize the intermediate phase between the PS phase and the PB phase, but high levels of graft copolymer also lead to a decrease in the rubber particle size, which is suspected to occur in the experiment using 25% recycled material.

[0068] Table 3

[0069]

[0070] In the experiments conducted according to the second strategy, recirculation amounts of 5% and 10% ratios relative to the unit flow rate (6 g / min) were used. Throughout the experiment, the reaction was monitored by measuring the solid percentage and RPS. Once the reaction reached a steady state, the material was collected and finished in an oven with a final solid content target of 70%. The analysis results showed that the RPS decreased with increasing recirculation amounts. The results are listed in Table 4. In addition, the span value also decreased, indicating a more uniform distribution of rubber particle size.

[0071] Table 4

[0072]

[0073] STEM analysis was completed to understand the effect on the sample morphology. The STEM images confirm the Malvern data, with the RPS value and span decreasing with increasing recycling amount. From the STEM images, more uniform rubber particles can be observed when the recycling amount increases. This effect is due to the presence of more graft copolymers during the phase transition, which requires a larger PS-PB mesophase to promote the production of more and smaller rubber particles. In addition, the morphology of the embedded body seems to be affected, and the rubber particle size decreases.

[0074] To quantify the effect of the recirculating flow on the sample morphology, STEM images were analyzed, see Figure 4 Table 5 shows a summary of the data collected from the analysis, which confirms the decrease in rubber particle size and investment length with increasing recycling percentage. On the other hand, a decrease in standard deviation is also noted, indicating a narrower particle size distribution. Its effect is more pronounced on investment size, as it decreases from 0.460 to 0.065.

[0075] Table 5

[0076]

[0077] These experiments suggest that the graft copolymer formed after phase inversion can be used as a method to produce a more uniform rubber particle size distribution. The correlation between narrower rubber particle size distribution and higher recycling percentage is supported by STEM images, as more uniform rubber particles can be observed with increasing recycling. This effect is believed to be a result of the presence of a larger amount of graft copolymer during the phase inversion, which requires a larger PS-PB mesophase to promote the production of more and smaller rubber particles. A similar effect was noted in the embedded body.

[0078] Additional public content

[0079] The first aspect is a method for producing high impact polystyrene, comprising introducing a partially polymerized mixture into a reactor, the mixture comprising at least one vinyl aromatic monomer, an elastomer and a reacted vinyl aromatic monomer, 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; discharging at least a portion of the phase-inverted mixture into another reactor; and recovering a portion of the phase-inverted mixture, wherein the recovered portion of the phase-inverted mixture comprises high impact polystyrene.

[0080] The second aspect is a method for producing high impact polystyrene, comprising introducing a partially polymerized mixture into a reactor, the mixture comprising at least one vinyl aromatic monomer, an elastomer and a reacted vinyl aromatic monomer, 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; introducing a portion of the phase-inverted mixture into another reactor; and recovering another portion of the phase-inverted mixture, wherein the phase-inverted mixture comprises high impact polystyrene.

[0081] A third aspect is the method of any one of the first and second aspects, wherein the vinyl aromatic monomer is styrene, substituted styrene, unsubstituted styrene, or any combination thereof.

[0082] A fourth aspect, that is, the method of any one of the first to third aspects, wherein the elastomer is a polymer of butadiene.

[0083] A fifth aspect, that is, the method of any one of the first to fourth aspects, wherein the first reaction mixture further comprises a free radical initiator, a chain transfer agent, or any combination thereof.

[0084] A sixth aspect, that is, the method of any one of aspects 1 to 5, wherein the reactor is a continuous stirred tank reactor, a plug flow reactor, or any combination thereof.

[0085] A seventh aspect, that is, the method of any one of aspects 1 to 6, wherein at least a portion of the reacted mixture is transferred from the outlet of one reactor to the inlet of another reactor.

[0086] An eighth aspect is the process of the seventh aspect, wherein at least a portion of the reacted mixture is delivered at a rate of about 1% of the first reactor volume per minute to about 20% of the first reactor volume per minute.

[0087] A ninth aspect, that is, the method of any one of aspects 1 to 8, wherein at least a portion of the reacted mixture is transported in a continuous discharge manner.

[0088] A tenth aspect, the method of any one of aspects 1 to 9, wherein the high impact polystyrene has a swelling index of about 5% to about 30%.

[0089] An eleventh aspect, the method of any one of aspects one to ten, wherein the high impact polystyrene rubber particle size is from about 1 micron to about 10 microns.

[0090] A twelfth aspect, the method of any one of aspects 1 to eleven, wherein the high impact polystyrene has a rubber particle size distribution of less than about 1.5.

[0091] A thirteenth aspect, the method of any one of aspects 1 to twelfth, wherein the high impact polystyrene has embedded bodies with a size of about 0.1 microns to about 2 microns.

[0092] A fourteenth aspect is a method for producing high impact polystyrene, comprising introducing a partially polymerized mixture into a first reactor, the mixture comprising at least one vinyl aromatic monomer, an elastomer and a reacted vinyl aromatic monomer, wherein the partially polymerized mixture does not undergo phase inversion; polymerizing the partially polymerized mixture to a phase inversion point in the first reactor 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 disposed downstream of the first reactor, and recovering another portion of the phase-inverted mixture, wherein the recovered another portion of the phase-inverted mixture comprises high impact polystyrene.

[0093] A fifteenth aspect is a high impact polystyrene reactor system comprising a first continuously stirred tank reactor having (a) an inlet configured to receive (i) at least one vinyl aromatic monomer, (ii) an elastomer, (iii) a free radical initiator and (b) an outlet configured to transport the first reactor effluent; a second continuously stirred tank reactor having (a) an inlet fluidly connected to the outlet of the first continuously stirred tank reactor, configured to receive (i) a portion of the first effluent from the first continuously 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 transport a portion of the second reactor effluent comprising high impact polystyrene; and (c) a conduit for establishing a recycle stream between the second reactor and the first reactor, wherein the recycle stream comprises another portion of the second reactor effluent.

[0094] A sixteenth aspect, that is, the reactor system of the fifteenth aspect, wherein the first continuously stirred tank reactor is arranged vertically, with the inlet at the top and the outlet at the bottom.

[0095] A seventeenth aspect, that is, the reactor system of any one of aspects fifteen to sixteen, wherein the vinyl aromatic monomer is styrene, substituted styrene, unsubstituted styrene, or any combination thereof.

[0096] In an eighteenth aspect, the reactor system of any one of aspects fifteen to seventeen, wherein the elastomer is a polymer of butadiene.

[0097] A nineteenth aspect, i.e., the reactor system of any one of aspects fifteen to eighteen, wherein the recycle stream from the second continuously stirred tank reactor is delivered to the first continuously stirred tank reactor at a rate of about 0.1% per minute to about 20% per minute based on the volume of the second continuously stirred tank reactor.

[0098] A twentieth aspect, the reactor system of any one of aspects fifteen to nineteen, wherein the high impact polystyrene rubber particle size is from about 1 micron to about 10 microns.

[0099] In a twenty-first aspect, the reactor system of any one of aspects fifteen through twentieth, wherein the high impact polystyrene has a rubber particle size distribution of less than about 1.5.

[0100] A twenty-second aspect, which is the reactor system of any one of aspects fifteen to twenty-one, wherein the high impact polystyrene has an embedded body size of about 0.1 microns to about 2 microns.

[0101] In a twenty-third aspect, the reactor system of any one of aspects fifteen to twenty-second, further comprising one or more additional linear flow reactors for receiving at least a portion of the effluent from the second reactor.

[0102] Although various aspects of the subject matter of the present invention are shown and described, those skilled in the art may make various changes to it without departing from the spirit and teachings of the subject matter of the present invention. The various aspects described herein are illustrative only and are not limiting. Many changes and variations of the subject matter disclosed in the present disclosure disclosed herein are possible and are within the scope of the subject matter disclosed in the present disclosure. When a numerical range or limitation is clearly indicated, it should be understood that these clear ranges or limitations include repeated ranges or limitations of the same magnitude that fall within the clearly indicated range or limitation (e.g., 1-10 includes 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). The use of the word "optionally" for any element in a claim means that the subject element is necessary or not necessary. Both options are within the scope of the claim. The use of broader terms such as including, including, having, etc. should be understood to support narrower terms such as consisting of, essentially consisting of, mainly consisting of, etc.

[0103] Therefore, the scope of protection is not limited by the above description, but only by the claims herein, which include all equivalents of the subject matter of the claims. Each claim is incorporated into the specification as an aspect of the present invention. Therefore, the claims are a further description and are supplementary to the various aspects of the subject matter of the present disclosure. The discussion of references herein does not mean that they are prior art to the subject matter of the present invention, especially the publication date of any reference may be after the priority date of this application. The disclosures of all patents, patent applications and publications cited herein are hereby incorporated by reference to the extent that they provide exemplary, procedural or other details supplementary to those described herein.

Claims

1. A method for producing high impact polystyrene, comprising: introducing a first reaction mixture into a first reactor, the first reaction mixture comprising at least one vinyl aromatic monomer and an elastomer, wherein the first reaction mixture is polymerized in the first reactor to produce a partially polymerized mixture; introducing a partially polymerized mixture comprising at least one vinyl aromatic monomer, an elastomer, and reacted vinyl aromatic monomer into a second reactor, wherein the partially polymerized mixture does not undergo a phase inversion; polymerizing the partially polymerized mixture to a phase inversion point in a second reactor to form a phase inverted mixture; recovering a portion of the phase-inverted mixture from the second reactor, wherein the phase-inverted mixture comprises high impact polystyrene; and Another portion of the phase-inverted mixture is introduced into the first reactor, wherein the another portion of the phase-inverted mixture accounts for 1 volume % to 20 volume % of the total volume of the second reactor.

2. The method of claim 1, wherein the vinyl aromatic monomer is styrene, substituted styrene, unsubstituted styrene, or any combination thereof.

3. The method of claim 1, wherein: The elastomer is a polymer of butadiene.

4. The method of claim 1, wherein the first reaction mixture further comprises a free radical initiator, a chain transfer agent, or any combination thereof.

5. The method of claim 1, wherein the reactor is a continuous stirred tank reactor, a plug flow reactor, or any combination thereof.

6. The method of claim 1, wherein: Another portion of the phase-inverted mixture is conveyed from the outlet of the second reactor to the inlet of the first reactor.

7. The process of claim 6, wherein the other portion of the phase-inverted mixture is delivered at a rate of 1% of the second reactor volume per minute to 20% of the second reactor volume per minute.

8. The method of claim 1, wherein another portion of the phase-inverted mixture is delivered in a continuous discharge.

9. The method of claim 1, wherein: The high impact polystyrene has a swelling index of 5% to 30%.

10. The method of claim 1, wherein: The rubber particle size of the high impact polystyrene is 1 micron to 10 microns.

11. The method of claim 1, wherein: The rubber particle size distribution of the high impact polystyrene is less than 1.

5.

12. The method of claim 1, wherein: The high impact polystyrene has embedded bodies with a size of 0.1 microns to 2 microns.

13. The method of claim 1, wherein the method is performed by a high impact polystyrene reactor system, the high impact polystyrene reactor system comprising: a first continuous stirred tank reactor having (a) an inlet configured to receive (i) at least one vinyl aromatic monomer, (ii) an elastomer, (iii) a free radical initiator and (b) an outlet configured to deliver a first reactor effluent; a second continuously stirred tank reactor having (a) an inlet in fluid communication with the outlet of the first continuously stirred tank reactor configured to receive (i) a portion of the first effluent from the first continuously 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 a recycle stream is established between the second reactor and the first reactor, wherein the recycle stream comprises another portion of the effluent of the second reactor.

14. The process of claim 13, wherein the first continuously stirred tank reactor is arranged vertically with the inlet at the top and the outlet at the bottom.

15. The method of claim 13, wherein: The vinyl aromatic monomer is styrene, substituted styrene, unsubstituted styrene or any combination thereof.

16. The method of claim 13, wherein: The elastomer is a polymer of butadiene.

17. The method of claim 13, wherein the recycle stream from the second continuously stirred tank reactor is delivered to the first continuously stirred tank reactor at a rate of 0.1% per minute to 20% per minute based on the volume of the second continuously stirred tank reactor.

18. The method of claim 13, wherein: The rubber particle size of the high impact polystyrene is 1 micron to 10 microns.

19. The method of claim 13, wherein: The rubber particle size distribution of the high impact polystyrene is less than 1.

5.

20. The method of claim 13, wherein: The high impact polystyrene has embedded bodies with a size of 0.1 microns to 2 microns.

21. The method of claim 13, wherein: The high impact polystyrene reactor system further comprises one or more additional linear flow reactors for receiving at least a portion of the effluent from the second reactor.

22. A method for producing high impact polystyrene, comprising: introducing a partially polymerized mixture comprising at least one vinyl aromatic monomer, an elastomer, and reacted vinyl aromatic monomer into a second reactor, wherein the partially polymerized mixture has not undergone a phase inversion; polymerizing the partially polymerized mixture to a phase inversion point in a second reactor to form a phase inverted mixture; introducing a portion of the phase-inverted mixture from a second reactor into the first reactor, wherein the second reactor is disposed downstream of the first reactor, wherein the portion of the phase-inverted mixture accounts for 1 volume % to 20 volume % of the total volume of the second reactor, and Another portion of the phase-inverted mixture is recovered, wherein the recovered another portion of the phase-inverted mixture comprises high impact polystyrene.

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