Styrene polymers having reduced trimer content

Abstract

Styrene polymers prepared by mass or solution processes are disclosed wherein the amount of trimer consisting of styrene and / or acrylonitrile is less than about 0.50 wt%. Methods of minimizing the amount of trimer consisting of styrene and / or acrylonitrile in styrene polymers prepared by mass or solution processes are also disclosed. The methods include the steps of lowering the temperature of the polymerization reaction mixture and including more than one initiator in the polymerization reaction mixture.

Description

[0001] This application is a divisional application of Chinese patent application No. 202080046343.5, filed on June 10, 2020, entitled "Styrene Polymer with Reduced Trimer Content". Technical Field

[0002] This invention relates to styrene polymers prepared by bulk or solution methods. In particular, this invention relates to the formation of styrene polymers wherein the amount of styrene and / or acrylonitrile trimers contained is less than about 0.50% by weight, prepared by bulk or solution methods. Background Technology

[0003] Polymers made from vinylidene-substituted aromatic monomers (such as styrene) are used in many polymer systems, including foams, packaging (food packaging), medical, electronics, optics, home appliances, and automotive applications. In some applications, the glass transition temperature of homopolymers of vinylidene-substituted aromatic monomers is lower than the temperature required for the application. Examples of styrene polymers include, for example, general-purpose polystyrene (GPPS) and high-impact polystyrene (HIPS).

[0004] Polymers containing vinyl or vinylidene-substituted aromatic monomers do not exhibit good chemical resistance, and modified polymers containing vinylidene-substituted aromatic monomers have been developed to improve chemical resistance. Some modified polymers can be copolymers, such as styrene-acrylonitrile (SAN). Other modified polymers may include butadiene-based rubbers, such as copolymers of styrene and acrylonitrile modified with polybutadiene rubber, commonly referred to as acrylonitrile-butadiene-styrene (ABS).

[0005] During the synthesis of styrene polymers (such as those described above) via bulk or solution methods, trimer formation reduces the polymer's Vicat properties, thereby decreasing the polymer's application window. One method to increase the Vicat properties of the resin is by adding N-phenylmaleimide as a comonomer. However, N-phenylmaleimide is costly to use, requires multiple additions, and leads to discoloration and lower ductility of the resulting polymer.

[0006] Therefore, it would be desirable to reduce or eliminate the amount used when using N-phenylmaleimide to increase Vicat, using methods such as bulk or solution methods, which would result in cost savings and excellent polymer properties. Thus, there is a need for styrene polymers that can include reduced concentrations of N-phenylmaleimide with improved properties using cost-effective methods. Summary of the Invention

[0007] This document discloses styrene polymers that meet these and other requirements. The disclosed styrene polymers, compositions, and articles may contain less than about 0.50% by weight of a trimer composed of styrene and / or acrylonitrile. The styrene polymers may include N-phenylmaleimide at a concentration of less than about 10% by weight and greater than about 0.1% by weight. The styrene polymers may also include (meth)acrylic acid monomers.

[0008] A method for reducing the amount of trimers consisting of styrene and / or acrylonitrile in styrene polymers prepared by bulk or solution methods is also disclosed. This method involves carrying out a polymerization reaction in the polymerization reaction mixture with more than one initiator at a reaction temperature lower than the temperature typically used, at the start of the polymerization reaction. Even at standard or even reduced devolatilization temperatures and pressures, this method surprisingly allows for a reduction in trimers present in the polymer. The described method significantly reduces trimer formation in bulk or solution methods, thereby providing thermoplastics with improved Vicat properties and a better balance of characteristics.

[0009] The embodiments of the present invention include:

[0010] 1) A styrene polymer prepared by a bulk or solution method, wherein the amount of the trimer consisting of styrene and / or acrylonitrile is less than 0.50% by weight based on the weight of the polymer, and the styrene polymer comprises unsaturated nitrile and N-phenylmaleimide.

[0011] 2) The polymer as described in embodiment 1, wherein the amount of the trimer is less than 0.45% by weight.

[0012] 3) The polymer as described in embodiment 1 or 2, wherein the amount of said trimer is less than 0.40 by weight.

[0013] 4) The polymer as described in any one of embodiments 1-3, wherein the amount of said trimer is greater than 0.15% by weight.

[0014] 5) The polymer as described in any one of embodiments 1-4, wherein the amount of said trimer is greater than 0.20% by weight.

[0015] 6) The polymer as described in any one of embodiments 1-3, wherein the polymer is a styrene-acrylonitrile copolymer (SAN).

[0016] 7) The polymer as described in any one of embodiments 1-3, wherein the polymer is an acrylonitrile-butadiene-styrene copolymer (ABS).

[0017] 8) The polymer as described in any one of the preceding embodiments 1-4, 6 and 7, wherein the Vicat softening temperature of the polymer is at least 107°C and the amount of the trimer is from 0.15% to 0.5% by weight.

[0018] 9) The polymer as described in any of the preceding embodiments, wherein the concentration of N-phenylmaleimide is less than 10% by weight and greater than 1% by weight.

[0019] 10) The polymer as described in any one of embodiments 1-9, wherein the polymer comprises a (meth)acrylic acid monomer.

[0020] 11) The polymer as described in embodiment 10, wherein the polymer comprises (meth)acrylate.

[0021] 12) A method for reducing the amount of trimer composed of styrene and / or acrylonitrile in a styrene polymer prepared by bulk or solution methods, comprising:

[0022] Provides a polymerization reaction mixture consisting of styrene, acrylonitrile, and more than one initiator, and

[0023] The polymerization reaction mixture is reacted at a polymerization temperature in the range of 60°C to 250°C.

[0024] 13) The method as described in embodiment 12, wherein the amount of the trimer is less than 0.5% by weight.

[0025] 14) The method of any one of embodiments 12-13, wherein the amount of said trimer is greater than 0.1% by weight.

[0026] 15) The method of any one of embodiments 12-14, wherein the amount of said trimer is less than 0.4% by weight.

[0027] 16) The method of any one of embodiments 12-15, wherein the one or more initiators of the polymerization reaction mixture are composed of a first initiator and a second initiator, wherein the T(1hr) half-life of the second initiator is longer than that of the first initiator.

[0028] 17) The method of any one of embodiments 12-16, wherein the T(1hr) half-life of the second initiator is at least 10°C higher than the T(1hr) half-life of the first initiator.

[0029] 18) The method of any one of embodiments 12-16, wherein the polymerization reaction mixture further comprises an olefinically unsaturated dicarboxylic acid, an anhydride or a derivative thereof.

[0030] 19) The method of any one of embodiments 12-16, wherein the T(1hr) half-life of the second initiator is at least 20°C higher than the T(1hr) half-life of the first initiator.

[0031] 20) The method of any one of embodiments 12-19, wherein the polymerization temperature range is 80°C to 200°C.

[0032] 21) The method of any one of embodiments 12-20, wherein the reaction is increased from a lower temperature to a higher temperature within the polymerization reaction temperature range.

[0033] 22) The method of any one of embodiments 18, 20 or 21, wherein the olefinic unsaturated dicarboxylic acid, anhydride or derivative thereof is composed of one or more of maleic acid, fumaric acid, maleic anhydride, dimethyl maleate, diethyl maleate, dibutyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate or N-phenylmaleimide.

[0034] 23) The method of any one of embodiments 18, 20, 21 or 22, wherein the olefinic unsaturated dicarboxylic acid, acid anhydride or derivative thereof is N-phenylmaleimide.

[0035] 24) The method of any one of embodiments 12-22, wherein the polymerization reaction mixture further comprises (meth)acrylate comonomers.

[0036] 25) The method of embodiment 24, wherein the (meth)acrylate comonomer is n-butyl methacrylate. Attached Figure Description

[0037] Figure 1 The effect of different trimer amounts on Vicat in a high-temperature ABS polymer containing a constant amount of N-phenylmaleimide was demonstrated. Detailed Implementation

[0038] Although this disclosure has been described in conjunction with certain embodiments, it should be understood that this disclosure is not limited to the disclosed embodiments, but rather is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, the scope of which is to be interpreted in the broadest possible sense to cover all such modifications and equivalent structures permitted by law.

[0039] As used herein, "one or more" means that at least one or more of the listed components may be used as disclosed. The residual content of a component refers to the amount of that component present in free form. Typically, the residual content of a component can be calculated from the ingredients used to prepare the component or composition. Alternatively, it can be determined using known analytical techniques. Heteroatoms as used herein include nitrogen, oxygen, sulfur, and silicon; more preferably, nitrogen and oxygen, with oxygen being the most preferred. A hydrocarbon group as used herein refers to a group containing one or more carbon atoms in a main chain and hydrogen atoms, optionally containing one or more heteroatoms. When a hydrocarbon group contains heteroatoms, the heteroatoms can form one or more functional groups known to those skilled in the art. A hydrocarbon group may contain any combination of alicyclic, aliphatic, aromatic, or such segments. Aliphatic segments may be straight or branched. Aliphatic and alicyclic segments may contain one or more double and / or triple bonds. Hydrocarbon groups include alkyl, alkenyl, alkynyl, aryl, cycloalkyl, cycloalkenyl, alkylaryl, and aralkyl groups. Alicyclic groups may contain both cyclic and acyclic moieties. "Hydroxyalkyl" means a hydrocarbon group having more than one valence or any subset thereof, such as alkylene, alkenylene, ynylene, arylene, cycloalkylene, cycloalkenylene, alkylenearyl, and arylalkylene. As used herein, valence means a covalent bond between a hydrocarbon or alkylene group and another group, such as a group or atom containing a carbonyl, oxygen, nitrogen, or sulfur, or the mentioned base compound. Unless otherwise stated, weight percentages or parts by weight as used herein refer to or are based on the weight of the composition.

[0040] The copolymers disclosed herein contain vinyl or vinylidene-substituted aromatic monomers. Vinylidene-substituted aromatic monomers include vinylidene, directly bonded to an alkenyl group within an aromatic structure. Vinyl or vinylidene-substituted aromatic monomers may contain one or more aromatic rings, one or two aromatic rings, or one aromatic ring. The aromatic rings may be unsubstituted or substituted with substituents that do not interfere with the polymerization of the vinyl or vinylidene-substituted aromatic monomers or the manufacture of polymers forming the desired structure. Substituents may be halogenated or alkyl groups, such as bromine, chlorine, or C1 to C4 alkyl groups; or methyl groups. Alkenyl groups comprise straight-chain or branched carbon chains having one or more double bonds or one double bond. Alkenyl groups that can be used with vinyl or vinylidene-substituted aromatic monomers may include those capable of polymerizing to form copolymers when bonded to an aromatic ring. Alkenyl groups may have 2 to 10 carbon atoms, 2 to 4 carbon atoms, or 2 carbon atoms. Exemplary vinyl- or vinylidene-substituted aromatic monomers include styrene, α-methylstyrene, N-phenyl-maleimide, and chlorostyrene; or α-methylstyrene and styrene. Vinyl- or vinylidene-substituted aromatic monomers may be monovinyl or vinylidene aromatic monomers containing an unsaturated group. Vinyl and vinylidene aromatic monomers include, but are not limited to, those described by reference in U.S. Patent Nos. 4,666,987, 4,572,819, and 4,585,825, which are incorporated herein by reference. A monomer may correspond to the following formula:

[0041]

[0042] Where R 1Each occurrence of Ar is either hydrogen or methyl, and each occurrence of Ar is an aromatic group. Ar may contain one or more aromatic rings, one or two aromatic rings, or one aromatic ring, and n may be 1 to 3, 1 to 2, or 1 each time it appears. The aromatic rings may be unsubstituted or substituted with substituents that do not interfere with the polymerization of the vinyl or vinylidene substituted aromatic monomers or the manufacture of polymers with the desired structure. Substituents may be halogenated or alkyl groups, such as bromine, chlorine, or C1 to C4 alkyl groups; or methyl groups. The vinyl or vinylidene substituted aromatic monomers may be present in the copolymer in sufficient quantities such that the polymer exhibits advantageous properties associated with polymers of vinyl or vinylidene substituted aromatic monomers (e.g., polystyrene). Advantageous properties of polymers of vinyl or vinylidene substituted monomers include a glass transition temperature of about 100°C or higher, desired transparency, high heat distortion temperature, etc. The copolymers disclosed herein contain vinyl or vinylidene substituted aromatic monomers in amounts of about 10% by weight or more, about 15% by weight or more, or about 20% by weight or more of the copolymer. The copolymers disclosed herein contain vinyl or vinylidene-substituted aromatic monomers in an amount of about 90% by weight or less, about 85% by weight or less, or about 80% by weight or less of the polymerizable composition or copolymer. The amounts may be related to the amount of vinyl or vinylidene-substituted aromatic monomers.

[0043] The composition may contain a branching agent commonly used in vinyl or vinylidene aromatic polymers. The branching agent may be a vinyl or vinylidene-substituted aromatic monomer having two or more vinyl or vinylidene groups (e.g., divinylbenzene). Other branching agents may include other bifunctional and generally multifunctional (functionality > 2) monomers, multifunctional initiators, and multifunctional chain transfer agents. The branching agent may be present in the polymerizable composition in an amount of about 0.001% by weight or more, about 0.002% by weight or more, or about 0.003% by weight or more. The branching agent may be present in the polymerizable composition in an amount of about 0.5% by weight or less, about 0.2% by weight or less, or about 0.1% by weight or less.

[0044] The copolymers disclosed herein may also comprise one or more (meth)acrylates. As used herein, (meth)acrylates refer to compounds having a vinyl group or vinylidene bonded to the carbonyl moiety of an alkyl ester, wherein the carbon atom of the vinylidene group bonded to the carbonyl group also has a hydrogen or methyl group bonded thereto. Exemplary (meth)acrylates available include those corresponding to the following formula:

[0045]

[0046] Where R a Each occurrence is either H or -CH3; and Rb It can be C1 to C- 30 alkyl groups or C 1-10 Alkyl group. Examples of one or more (meth)acrylates include lower (meth)acrylate alkyl esters, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, and hexyl (meth)acrylate.

[0047] One or more (meth)acrylates in the copolymer may be present in sufficient quantities to provide the desired properties of the copolymer, such as processability, practical toughness, refractive index, environmental stress cracking resistance, hydrolytic stability, thermal stability, UV stability, impact resistance, weather resistance, etc. The copolymers disclosed herein contain (meth)acrylates in amounts of about 0% by weight or more, about 1% by weight or more, or about 2% by weight or more of the polymerizable composition or copolymer. The copolymers disclosed herein contain (meth)acrylates in amounts of about 20% by weight or less, about 15% by weight or less, about 10% by weight or less, about 8% by weight or less, or about 5% by weight or less of the copolymer.

[0048] The copolymer may include one or more unsaturated nitriles. Unsaturated nitriles include, but are not limited to, acrylonitrile, methacrylonitrile, ethylacrylonitrile, fumaric acid, and mixtures thereof. Unsaturated nitriles may be acrylonitrile. Unsaturated nitriles are used in copolymers to improve glass transition temperature, chemical resistance, etc. The copolymers disclosed herein contain one or more unsaturated nitriles in amounts of about 0% by weight or more, about 1% by weight or more, or about 2% by weight or more of the copolymer. The copolymer may contain one or more unsaturated nitriles in amounts of about 40% by weight or less, about 35% by weight or less, about 30% by weight or less, or about 25% by weight or less of the copolymer.

[0049] Other vinyl monomers may also be included in the copolymer in sufficient quantities to provide the desired properties as disclosed herein, including conjugated 1,3-dienes (e.g., butadiene, isoprene, etc.); α- or β-unsaturated monocarboxylic acids and their derivatives (e.g., acrylic acid, methacrylic acid, etc.); vinyl halides, such as vinyl chloride, vinyl bromide, etc.; vinyl esters, such as vinyl acetate, vinyl propionate, etc.; olefinically unsaturated dicarboxylic acids and their anhydrides and derivatives, such as maleic acid, fumaric acid, maleic anhydride, dialkyl maleate or dialkyl fumarate, such as dimethyl maleate, diethyl maleate, dibutyl maleate, the corresponding fumarate, N-phenylmaleimide, etc.; and so on. These additional comonomers can be incorporated into the composition in a variety of ways, including crosspolymerization with copolymers containing vinylidene substituted aromatics and / or polymerization into polymer components, which can be combined, for example, blended into a matrix. If present, the amount of such comonomer may be equal to or less than about 20% by weight, equal to or less than about 10% by weight, or equal to about 5% by weight, based on the total weight of the polymer composition. Such comonomer may be present in an amount of about 1% by weight or more.

[0050] The disclosed compositions may contain impact modifiers. The terms impact modifier and rubber are used interchangeably herein. Various impact modifiers may be used in the disclosed compositions; such as diene rubber, ethylene propylene rubber, ethylene propylene diene (EPDM) rubber, ethylene copolymer rubber, acrylate rubber, polyisoprene rubber, silicone rubber, silicone-acrylate rubber, polyurethane, thermoplastic elastomers, halogenated rubber, and mixtures thereof. Interpolymers of rubber forming monomers with other copolymerizable monomers are also suitable. Rubber may be present in a sufficient amount in the formulated composition to provide the desired impact properties to the composition. Desired impact properties include increased izod, charpy, Gardner, tensile strength, falling dart strength, etc. The compositions disclosed herein contain an impact modifier (rubber) in amounts of about 0.5% by weight or more, about 1% by weight or more, or about 2% by weight or more of the composition. The compositions disclosed herein contain about 50% by weight or less, about 45% by weight or less, about 40% by weight or less, about 30% by weight or less, about 20% by weight or less, or about 10% by weight or less of an impact modifier (rubber). The compositions disclosed herein contain about 0.5% by weight or more of a copolymer. The compositions disclosed herein contain about 99.5% by weight or less, 90% by weight or less, 80% by weight or less, or 50% by weight or less of a copolymer. As used in this context, a formulated composition is a formulated composition containing all the ingredients intended for the intended use.

[0051] The rubber can be a diene rubber such as polybutadiene, polyisoprene, polypentadiene, polychloroprene, etc., or a mixture of diene rubbers, i.e., any rubbery polymer of one or more conjugated 1,3-dienes such as 1,3-butadiene. Such rubber includes homopolymers of 1,3-butadiene and copolymers of 1,3-butadiene with one or more copolymerizable monomers such as vinylidene-substituted aromatic compounds (styrene). The diene rubber can be a homopolymer of 1,3-butadiene. An exemplary copolymer of 1,3-butadiene is a block or cone block rubber of at least about 30% by weight of 1,3-butadiene, about 50% by weight, about 70% by weight, or about 90% by weight of 1,3-butadiene, and up to about 70% by weight of vinylidene-substituted aromatic monomers, and up to about 50% by weight, about 30% by weight, or about 10% by weight of vinylidene-substituted aromatic monomers, the weight based on the weight of the 1,3-butadiene copolymer.

[0052] The impact modifier used can be those polymers and copolymers that exhibit a second-order transition temperature (Tg) for the diene segment not higher than 0°C or not higher than -20°C, sometimes referred to as the glass transition temperature (Tg), as determined using conventional techniques, such as ASTM Test Method D 746-52 T. Tg is the temperature or temperature range at which a polymeric material transitions from a rigid glassy material to a soft material. Tg can be determined by differential scanning calorimetry (DSC). The diene rubber may have a cis content equal to or less than 99% or less than 97%. The cis content of the diene rubber may be equal to or greater than 20% or greater than 37%, wherein the cis weight percentage is based on the weight of the diene rubber. The rubber may be 1,2-butadiene rubber having at least about 0% by weight of 1,2-vinyl or at least about 7% by weight of 1,2-vinyl 1,3-butadiene rubber based on the weight of 1,3-butadiene rubber. The 1,3-butadiene rubber may have less than or equal to about 30% by weight of 1,2-vinyl or less than or equal to about 13% by weight of 1,2-vinyl based on the weight of the 1,3-butadiene rubber. The diene rubber may have a weight-average molecular weight of at least about 100 kg / mol or at least about 300 kg / mol. The diene rubber may have a weight-average molecular weight equal to or less than about 900 kg / mol or equal to or less than 600 kg / mol. The diene rubber has a solution viscosity of at least 10 centistokes (cSt) (10% (%) solution in styrene at 25 °C) or a solution viscosity of about 30 cSt. The diene rubber may have a solution viscosity equal to or less than about 500 cSt or equal to or less than about 400 cSt. The rubber having grafted and / or adsorbed polymers (if present) is dispersed in a continuous matrix phase as discrete particles. The rubber particles may include a range of sizes having a unimodal, bimodal, or multimodal distribution. As used herein, the average particle size of rubber particles refers to the volume average diameter. Average particle size measurements typically involve the polymer grafted onto the rubber particles. Unless otherwise stated, the rubber particle sizes disclosed and claimed herein are those with ACCUCOMP... TMThe following method was used on Coulter Multisizer II or II e software version 2.01: Dissolve approximately 3 polymer samples (30-70 mg) in 5 mL of dimethylformamide (DMF) using an ultrasonic bath with stirring for approximately 15 to 20 minutes. Mix 10 mL of electrolyte solution (1% NH4SCN in DMF) with 0.2 mL of the sample solution. Use the plough stage with a 20 μm Coulter tube and 1.16 μm calibration material. The coincidence level indicator reading should be between 5% and 10%. If the reading is higher than 10%, dilute the sample with electrolyte solution in a beaker, or if the reading is too low, add more polymer solution dropwise to the DMF. The volume average particle size was reported. The average particle size of the rubber particles can be equal to or greater than approximately 0.05 μm, equal to or greater than approximately 0.1 μm, and approximately 0.5 μm. The average particle size of rubber particles can be equal to or less than about 10 micrometers, equal to or less than about 5 micrometers, or equal to or less than about 4 micrometers.

[0053] The disclosed compositions may optionally contain one or more additives commonly used in this type of composition. Exemplary additives include: flame retardants, stabilizers, colorants (such as pigments, carbon black, TiO2, etc.), antioxidants (such as Irganox 1076 or Irgafos 178), adsorbents (such as zeolite, activated carbon, bamboo charcoal, etc.), antistatic agents, silicone oils, flow enhancers, release agents, etc. Exemplary anti-ignition additives include halogenated hydrocarbons, halogenated carbonate oligomers, halogenated diglycidyl ethers, organophosphorus compounds, fluorinated olefins, antimony oxides, and metal salts of aromatic sulfur, or mixtures thereof. Compounds that stabilize the bulk-polymerized rubber-modified vinylidene-substituted aromatic copolymer compositions to prevent degradation by, but not limited to, heat, light, and oxygen or mixtures thereof may be used. Fillers and reinforcing agents may also be present. Exemplary fillers include talc, clay, wollastonite, mica, glass, or mixtures thereof.

[0054] If used, such additives and / or fillers may be present in the formulated composition in amounts of about 0.01% by weight or more, about 0.1% by weight or more, about 1% by weight or more, about 2% by weight or more, or about 3% by weight or more, based on the weight of the composition. Additives and / or fillers may be present in amounts of about 40% by weight or less, about 30% by weight or less, about 20% by weight or less, about 15% by weight or less, about 10% by weight or less, or about 5% by weight or less, based on the weight of the composition. Based on the weight of the composition, additives may be present in amounts up to 5% by weight, while fillers may be present in amounts up to 40% by weight.

[0055] This document also discloses exemplary vinyl or vinylidene-substituted aromatic copolymers comprising various proportions of acrylonitrile and styrene monomers. The disclosed acrylonitrile-styrene polymers may contain styrene monomers at concentrations of about 25% by weight or more, about 50% by weight or more, or about 70% by weight or more, and acrylonitrile monomers at concentrations of about 25% by weight or more, or about 50% by weight or more, or about 70% by weight or more. The disclosed acrylonitrile-styrene polymers may contain styrene monomers at concentrations of about 80% by weight or less, about 55% by weight or less, or about 30% by weight or less, and acrylonitrile monomers at concentrations of about 80% by weight, about 55% by weight or less, or less, or about 30% by weight or less.

[0056] This document also discloses exemplary vinyl or vinylidene-substituted aromatic copolymers comprising acrylonitrile and styrene monomers and polybutadiene in respective proportions. The disclosed acrylonitrile-butadiene-styrene polymers may contain styrene monomers at concentrations of about 25% by weight or higher, about 40% by weight or higher, or about 55% by weight or higher; butadiene monomers at concentrations of about 5% by weight or higher, or about 10% by weight or higher; or acrylonitrile monomers at concentrations of about 5% by weight or higher, or about 10% by weight or higher, or about 18% by weight or higher. The disclosed acrylonitrile-butadiene-styrene polymer may contain styrene monomer at concentrations of about 90% by weight or less, about 85% by weight or less, about 75% by weight or less, or about 65% by weight or less; butadiene monomer at concentrations of about 35% by weight or less, about 25% by weight or less, or about 18% by weight or less; and acrylonitrile monomer at concentrations of about 40% by weight or less, about 35% by weight or less, about 25% by weight or less, or about 18% by weight or less.

[0057] The disclosed polymer may optionally include (meth)acrylate comonomers and / or maleimide comonomers. The comonomer may be n-butyl acrylate or N-phenylmaleimide or a combination thereof. n-butyl acrylate or N-phenylmaleimide or a combination thereof may be present in amounts less than about 10% by weight, less than about 7% by weight, or less than 5% by weight. n-butyl acrylate or N-phenylmaleimide may be present in amounts greater than about 0.1% by weight, greater than about 0.5% by weight, greater than about 1% by weight, or greater than about 2% by weight.

[0058] The polymers disclosed herein, prepared by bulk or solution methods, may comprise trimers containing styrene and / or acrylonitrile in amounts less than about 0.50 wt%, less than about 0.45 wt%, less than about 0.40 wt%, less than about 0.30 wt%, less than about 0.25 wt%, or less than about 0.20 wt%. The polymers disclosed herein may comprise trimers composed of styrene and / or acrylonitrile in amounts greater than about 0.05 wt%, greater than about 0.10%, greater than about 0.15 wt%, greater than about 0.25 wt%, greater than about 0.35 wt%, greater than about 0.43 wt%, or greater than about 0.47 wt%. The polymers may be homopolymers, such as, for example, general-purpose polystyrene (GPPS) or high-impact polystyrene (HIPS). The polymers may be copolymers, such as, for example, acrylonitrile-styrene (SAN) or acrylonitrile-butadiene-styrene (ABS).

[0059] Various techniques for generating copolymers are disclosed. Examples of these known polymerization methods include bulk polymerization, bulk solution polymerization, or bulk-suspension polymerization, commonly referred to as bulk polymerization methods. For a detailed discussion of how to prepare compositions containing monovinylene aromatic copolymers, see [link to relevant documentation]. 现代苯乙烯聚合物 Edited by John Schiers and Duane Priddy, Wiley, ISBN 0 471 497525. Additionally, for example, U.S. Patent Nos. 3,660,535; 3,243,481; and 4,239,863. Continuous bulk polymerization techniques are advantageously used for the preparation of copolymers. Polymerization can be carried out in one or more substantially linear, stratified flow, or so-called “plug flow” type reactors, such as those described in U.S. Patent No. 2,727,884, sometimes referred to as the multi-zone plug flow bulk method, which may or may not include a portion of the polymerized product that is recycled, or alternatively, in a stirred tank reactor, wherein the contents of the reactor are substantially homogeneous throughout the process, which is typically used in combination with one or more plug flow type reactors. The stirred tank reactor can be a boiling and / or plug flow reactor. Such reactors can be used in series. Methods for preparing copolymers using stirred tank reactors are disclosed in 现代苯乙烯聚合物, Edited by John Schiers and Duane Priddy, Wiley, ISBN 0 47149752 5, published in 2003, see pp. 43–72. Alternatively, parallel reactor settings, as taught in EP 412801, may also be applied to the preparation of copolymers, the relevant portion of which is incorporated herein by reference.

[0060] Multi-zone plug flow bulk polymerization involves a series of interconnected polymerization vessels (or towers) providing multiple reaction zones. A monomer mixture for preparing copolymers is formed and then fed into the reaction system. Rubber, such as polybutadiene rubber, can be dissolved in the monomer mixture before being fed into the reaction system. Polymerization can be initiated thermally or chemically, and the viscosity of the reaction mixture will gradually increase. During the reaction, if present, the rubber may graft onto the copolymer, and a bulk copolymer (also called a free copolymer or matrix copolymer) is also formed in the rubber solution. When the free copolymer cannot "retain" itself in a single, continuous "phase" of the rubber solution, it begins to form copolymer domains dissolved in the monomers and solvent. The polymerization mixture is now a two-phase system. As polymerization proceeds, more and more free copolymers are formed. Eventually, the free copolymer becomes the continuous phase (phase inversion). Some copolymers are also adsorbed within the rubber particles. A pre-phase inversion means that the rubber solution is a continuous phase and no rubber particles are formed; a post-phase inversion means that all the continuous rubber phases are converted into rubber domains and a continuous copolymer phase is present. After the phase inversion, more matrix copolymers may form.

[0061] Feeds containing functional monomers (such as N-phenylmaleimide) can be added at one or more locations throughout the polymerization process. These additions can improve the Tg of the matrix and the heat resistance of the product. The one or more locations may be the same as or different from where the comonomer is added, see, for example, U.S. Patents 5,412,036 and 5,446,103. Ideally, N-phenylmaleimide is initially present along with all other comonomers such as styrene, butadiene, and acrylonitrile.

[0062] Throughout the polymerization, volatilization, and conveying process, feeds containing processable functional additives (such as ethylene bis-stearamide, dialkyl adipate, polydimethylsiloxane, or other lubricants or release agents) with additive properties can be added at one or more locations, which may be the same as or different from the locations where comonomers are added.

[0063] Once the desired monomer conversion level is achieved, the polymeric mixture can be subjected to conditions sufficient to further crosslink the rubber and remove any unreacted monomers and solvents. This crosslinking and removal of unreacted monomers, as well as the removal of diluents or solvents (if used) and other volatile substances, is advantageously carried out using conventional devolatiles techniques as described herein and ideally under mild conditions. The polymer can then be extruded, and bulk pellets obtained from a granulator.

[0064] The polymerization temperature depends on a variety of factors, including the specific type and concentration of the initiator and rubber (if present), the comonomer, the reactor setup (e.g., linear, parallel, recycle, etc.), and, if applicable, the use of a reaction solvent. Polymerization temperatures ranging from 60°C to 250°C can be used, typically starting at a lower temperature and then increasing during the polymerization reaction. Ideally, the temperature range is from about 80°C, 90°C, 100°C, or 105°C to about 200°C, 180°C, 170°C, or 160°C. In a specific embodiment containing rubber, a first temperature range of about 60°C to about 120°C may be used before the phase inversion, followed by temperatures from 100°C to 250°C or 200°C after the phase inversion. Bulk polymerization continues at this increased temperature until the desired conversion of monomer to polymer is obtained. The polymerization time can be any feasible, such as those known in the art, and typically ranges from a few minutes to 24 hours, but is usually from about 1 hour to about 8 or 6 hours.

[0065] Typically, a conversion rate of 55 to 90 or 60 to 85% by weight of monomer to polymer (sometimes also called solids percentage) (i.e., monomer added in the feed and any additional streams, including any recycle streams) is desired when adding monomer to the polymerization system. Solids percentage is the ratio of the weight of solids (e.g., rubber plus matrix (co)polymer) to the weight of the reaction mixture (e.g., one or more unpolymerized monomers) expressed as a percentage at any specified time during the polymerization reaction.

[0066] Four aspects are particularly important for the large-scale synthesis of high-performance rubber-modified copolymers. These aspects are the grafting of the rubber matrix, particle formation or particle size measurement, the molecular weight distribution of the matrix, and the crosslinking of the rubber particles at the completion point of bulk polymerization. Alternatively, a combination of bulk and suspension polymerization techniques can be used. Using these techniques, after the phase inversion and subsequent dimensional stabilization of the rubber particles, the partially polymerized product can be suspended in an aqueous medium containing a polymerization initiator, with or without additional monomers, and then polymerization can be completed.

[0067] The molecular weight of a polymer is directly related to the entanglement effect attributable to its rheological and physical properties. The molecular weight of a matrix copolymer can be adjusted by adding a suitable chain transfer agent. Chain transfer agents, or molecular weight regulators, are substances capable of atom or group transfer or addition-elimination. Organic molecules with unstable hydrogen atoms are well-known, such as α-methylstyrene dimers, thiols or thiols such as n-dodecylthiol (nDM) and mercaptoacetate, disulfides, dithiourea disulfides, monosulfides, halides or halogenated hydrocarbons, common solvents, and certain unsaturated compounds, such as, for example, allyl halides, allyl sulfides, and terpenes such as terpinoline. Transition metal complexes such as cobalt(II) porphyrin complexes can also be used as transfer agents. The amount of chain transfer agent added is about 0.0001 to 10% by weight, based on the weight of the reaction mixture (i.e., rubber, one or more monomers, and solvent, if any). Based on the weight of the reaction mixture, the amount of chain transfer agent added may be equal to or greater than about 0.001 wt%, about 0.002 or about 0.003 wt%. Based on the weight of the reaction mixture, the amount of chain transfer agent added may be equal to or greater than about 0.5 wt%, about 0.2 or about 0.1 wt%.

[0068] Chain transfer agents can be added all at once in one reactor zone, or they can be added in two or more reactor zones. Chain transfer agents can be added before phase inversion, during rubber particle size measurement, with more added after particle size measurement to help control the matrix molecular weight, and optionally more added later to fine-tune the matrix molecular weight / molecular weight distribution. Chain transfer agents can be added at the start of polymerization (in other words, when the solid percentage of the reaction mixture equals the weight percentage of the rubber) in a first amount equal to or greater than 0.001 wt%, about 0.002 to about 0.1 wt%, or about 0.003 to about 0.05 wt% (based on the weight of the reaction mixture). Subsequent additions of chain transfer agents, for example after about 40% solids or 30% solids, are added in a second amount equal to or less than about 0.7 wt%, about 0.001 to about 0.6 wt%, or about 0.002 to about 0.5 wt% (based on the weight of the reaction mixture). The molecular weight of the matrix copolymer depends particularly on how much chain transfer agent is used and when it is added.

[0069] This document also discloses a method for reducing the amount of trimer consisting of styrene and / or acrylonitrile in styrene polymers prepared by bulk or solution methods. The method includes the steps of: using a mild polymerization temperature and volatilization conditions for the polymerization mixture, and including more than one initiator in the polymerization mixture, said initiator preferably added simultaneously during polymerization, and particularly at the start or initiation of polymerization. For example, the initiator may be entirely contained in one or more monomer feeds. The styrene polymer may be, but is not limited to, any of the polymers disclosed herein.

[0070] Styrene resins can be prepared by chemical initiation, thermal initiation, or more typically a combination of both. The trimer may contain 0-3 styrene monomer units and 0-3 acrylonitrile monomer units, wherein the total number of monomer units is equal to 3 (e.g., styrene trimer, styrene-acrylonitrile trimer, or acrylonitrile trimer). The amount of trimer can be determined by suitable methods, such as high-performance liquid chromatography (HPLC) techniques known in the art.

[0071] Typically, the T(1 hr) half-life of one initiator (also referred to herein as "one or more late initiators" or "one or more second initiators") should be greater than that of another initiator (also referred to herein as "first initiator"). Initiators can be added to the polymerization mixture separately at different times during the polymerization process, but it is desirable to add them simultaneously, whether in separate feeds or mixed together, especially at the beginning of polymerization, such as when they are fed into the polymerization reactor, fed together with the initial monomer feed, or mixed with the monomer. More initiators can be added later in the polymerization reaction than the initial feeds, and this can also include additional monomers or recycled materials from the polymerization. The T(1 hr) half-life of a later initiator will be about 10°C, about 15°C, or about 20°C higher than that of the first initiator. Typically, the T(1 hr) half-life of the first initiator is between about 60°C and 130°C.

[0072] The initiator can decompose uniformly. Exemplary initiators include, but are not limited to, dicumyl peroxide, 1,1,di(tert-butylperoxide)cyclohexane, 2,5-dimethyl-2,5-di(tert-butylperoxide)hexane, diisobutyryl peroxide, cumyl peroxide neodecanoate, di(3-methoxybutyl) peroxide, 1,1,3,3-tetramethyl peroxide neodecanoate, tert-amyl peroxide neodecanoate, disec-butyl peroxide dicarbonate, diisopropyl peroxide dicarbonate, di(4-tert-butylcyclohexyl) peroxide dicarbonate, di(2-ethylhexyl) peroxide dicarbonate, and peroxide... tert-butyl neodecanoate, hexadecyl peroxide dicarbonate, dimyristyl peroxide dicarbonate, 1,1,3,3-tetramethylbutyl peroxypentanoate, tert-amyl peroxypentanoate, bis(3,5,5-trimethylhexanoyl peroxide), dilauroyl peroxide, didecyl peroxide, 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxide)hexane, 1,1,3,3-tetramethylbutyl peroxide-2-ethylhexanoate, peroxide- 2-Ethylhexanoate tert-amyl peroxide, benzoyl peroxide, tert-butyl peroxide-2-ethylhexanoate, tert-butyl peroxide isobutyrate, 1,1-di(tert-butylperoxide)-3,3,5-trimethylcyclohexane, 1,1-di(tert-amylperoxide)cyclohexane, 1,1-di(tert-butylperoxide)cyclohexane, 2-ethylhexyl carbonate tert-amyl peracetate, tert-amyl peroxide-3,5,5-trimethylhexanoate tert-butyl peroxide, 2,2-di(tert-butylperoxide)butane, The initiators include isopropyl tert-butyl peroxide, 2-ethylhexyl tert-butyl peroxide, tert-amyl peroxybenzoate, tert-butyl peracetate, butyl 4,4-di(tert-butylperoxy)valerate, butyl 4,4-di(tert-butylperoxy)valerate, di(tert-butylperoxy)isopropylbenzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, di-tert-butyl peroxide, and 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane. As mentioned above, it is required that the later initiator has a different T(1 hr) half-life, with the later initiator having a longer T(1 hr) half-life than the first initiator. Therefore, the selection of the first and second initiators is entirely within the scope of those skilled in the art.

[0073] The first initiator may be present in any amount that enhances the polymerization of vinyl or vinylidene-substituted aromatic polymers at lower temperatures and results in less trimer formation. Based on the weight of the polymerizable composition, the first initiator may be present in amounts of about 10 ppm or more, about 30 ppm or more, or about 50 ppm or more. Based on the weight of the polymerizable composition, the first initiator may be present in amounts of about 800 ppm or less, about 500 ppm or less, or about 300 ppm or less. This amount is based on the pure initiator, not on diluted compositions typically sold commercially. If a diluted composition is used, the amount needs to be recalculated as pure initiator.

[0074] The second initiator may be present in any amount that enhances the polymerization of vinyl or vinylidene-substituted aromatic polymers at lower temperatures and results in less trimer formation. Based on the weight of the polymerizable composition, the second initiator may be present in amounts of about 10 ppm or more, about 30 ppm or more, or about 50 ppm or more. Based on the weight of the polymerizable composition, the second initiator may be present in amounts of about 800 ppm or less, about 500 ppm or less, or about 300 ppm or less.

[0075] As described above, this method can employ mild devolatation conditions and still produce low trimer concentrations. If desired, the styrene resin can be further refined, for example, to further reduce the amount of trimer. For instance, using higher vacuum, higher devolatation temperatures, and larger amounts of devolater during the preparation of the styrene polymer may produce resins with lower trimer content, but surprisingly, these are not necessary when using more than one initiator, especially when such initiators are used from the start to the end of polymerization. Devolatation can be carried out at any suitable temperature, such as between about 180°C and about 300°C or about 250°C, but ideally below about 240°C, 235°C, or 230°C. The pressure during devolatation can be any suitable pressure, such as from about 5, 10, or 20 mbar to about 1200, 1000, 800, 500, 200, 100, or 50. The time during devolatation can be any useful time and typically ranges from 2 to 3 minutes to 100, 50, or 30 minutes. In one implementation, even if two additional devolatilization stages and a preheating stage can be used, a single-stage devolatilizer can be employed. When a two-stage devolatilizer is used, the average temperature and average pressure of the two stages can be the same as those described above.

[0076] In one embodiment, when the polymer contains about 0.1% to 0.5% trimer and 0.1 wt%, 0.25 wt%, 0.5 wt%, 1 wt% to 5 wt%, or 4 wt% N-phenylmaleimide, and particularly when the styrene polymer consists of unsaturated nitrile and N-phenylmaleimide (exemplary examples being styrene-acrylonitrile copolymer and ABS copolymer), the polymer typically has a Vicat softening temperature of at least about 105°C, 106°C, 107°C, or greater to about 120°C, 115°C, or 112°C. The Vicat softening temperature can be determined using the Vicat A test method (A50 method) according to known standards such as ASTM D 1525 or ISO 306.

[0077] Articles prepared from the compositions disclosed herein are disclosed. Such articles can be manufactured in any known manner, typically with polymers containing one or more vinylidene substituted aromatic compounds. The articles can be manufactured by molding, extrusion, thermoforming, foaming, blow molding, injection molding, extrusion blow molding, and combinations thereof. The articles can be molded, extruded, and molded, etc. The disclosed articles may exhibit a glass transition temperature of about 100°C or lower. The disclosed articles may be transparent or opaque.

[0078] Example

[0079] The following examples are provided only to illustrate the invention and are not intended to limit its scope. Unless otherwise stated, all parts and percentages are by weight.

[0080] Example 1: Reducing trimer in high-temperature ABS polymers containing N-phenylmaleimide as a comonomer

[0081] The comparative examples are based on the use of a single initiator and standard temperature profiles. The reactor setup consists of four stirred-tube reactors in series, each with three zones, followed by a two-stage volatilization process with an average temperature of approximately 210°C to 218°C. The residence time in each zone is 20 minutes, and the residence time in each reactor is 1 hour. The feed composition is 16.9 wt% acrylonitrile, 52.2 wt% styrene, 21.2 wt% ethylbenzene, and 9.7 wt% polybutadiene rubber. As an initiator, 115 ppm (based on feed) of Trigonox 22 is added to the feed. A certain amount of N-phenylmaleimide is added to improve heat resistance (approximately 3.8 wt% of the final product). Examples of the present invention use the same hardware and volatilization process, but employ two initiators and optimized temperature profiles. The feed composition is 16.9 wt% acrylonitrile, 49.4 wt% styrene, 24.0 wt% ethylbenzene, and 9.7 wt% polybutadiene. A mixture of 115 ppm (based on feed) Trigonox 22 and 200 ppm (based on feed) Trigonox 101 was used as the initiator. The same amount of N-phenylmaleimide was added. The temperature profiles for the examples are summarized in Table 1. Table 2 shows the trimer concentration and Vicat concentration under both conditions.

[0082] Table 1: Zone Temperature (°C)

[0083]

[0084] The results are shown in Table 2.

[0085] Table 2

[0086]

[0087] Referring now to the figure, the effect of varying trimer content on Vicat hardness is illustrated in high-temperature ABS polymers comprising a constant amount of N-phenylmaleimide (3.7–4.0 wt% based on the final product). Vicat hardness, as used herein, was measured at a loading of 50 N and a heating rate of 50 °C / hr (ISO 306 standard). The data in the figure yields a linear regression equation: y = -6.3693x + 110.42. Therefore, when the ABS copolymer contains approximately 3.8 wt% N-phenylmaleimide, a trimer content of approximately 0.5 wt% achieves a Vicat hardness of approximately 107.2 °C. Similarly, a trimer content of approximately 0.4 wt% achieves a Vicat hardness of approximately 107.9 °C.

Claims

1. A styrene polymer prepared by a continuous bulk or solution method, wherein the amount of the trimer containing styrene and acrylonitrile is from 0.10% by weight to less than 0.50% by weight based on the weight of the styrene polymer, the styrene polymer comprising unsaturated nitriles and more than 0.1% by weight to less than 10% by weight of N-phenylmaleimide, and the Vicat softening temperature of the styrene polymer is at least 105°C.

2. The styrene polymer according to claim 1, wherein the continuous bulk or solution method comprises: A polymerization reaction mixture comprising styrene, acrylonitrile, N-phenylmaleimide and a first initiator and a second initiator is provided, wherein the T(1hr) half-life of the second initiator is at least 20°C higher than the T(1hr) half-life of the first initiator; The polymerization reaction mixture is reacted at a polymerization temperature in the range of 60°C to 160°C, wherein the polymerization begins at a polymerization temperature in the range of 60°C to 120°C and is increased to a higher polymerization temperature of up to 160°C.

3. The styrene polymer according to claim 1, wherein the amount of the trimer is greater than 0.15% by weight and less than 0.45% by weight.

4. The styrene polymer according to claim 1, wherein the styrene polymer comprises acrylonitrile, butadiene, and styrene comonomer.

5. The styrene polymer according to claim 1, wherein the Vicat softening temperature of the styrene polymer is at least 106°C.

6. The styrene polymer according to claim 1, wherein the concentration of N-phenylmaleimide is less than 7% by weight and greater than 1% by weight of the styrene polymer.

7. The styrene polymer according to claim 1, wherein the styrene polymer comprises (meth)acrylic acid monomer.

8. A method for reducing the amount of styrene and acrylonitrile trimers in a styrene polymer prepared by a continuous bulk or solution method, comprising: A polymerization reaction mixture comprising styrene, acrylonitrile, greater than 0.1% to less than 10% by weight of N-phenylmaleimide, and a first initiator and a second initiator, wherein the T(1hr) half-life of the second initiator is at least 20°C higher than the T(1hr) half-life of the first initiator. The polymerization reaction mixture is reacted at a polymerization temperature in the range of 60°C to 160°C, wherein the reaction is initiated at a polymerization temperature in the range of 60°C to 120°C and carried out at a higher polymerization temperature of up to 160°C. A styrene polymer is manufactured having a trimer containing styrene and acrylonitrile at less than 0.50% by weight based on the weight of the styrene polymer, and the Vicat softening temperature of the styrene polymer is at least 105°C.

9. The method of claim 8, wherein the amount of the trimer is greater than 0.10% by weight of the styrene polymer and less than 0.5% by weight of the styrene polymer.

10. The method according to claim 8 or 9, wherein the polymerization reaction mixture comprises, in addition to N-phenylmaleimide, an olefinically unsaturated dicarboxylic acid, an anhydride, or a derivative thereof.

11. The method according to claim 10, wherein the olefinically unsaturated dicarboxylic acid, anhydride or derivative thereof comprises one or more of maleic acid, fumaric acid, maleic anhydride, dimethyl maleate, diethyl maleate, dibutyl maleate, dimethyl fumarate, diethyl fumarate or dibutyl fumarate.

12. The method according to claim 8 or 9, wherein the polymerization reaction mixture further comprises a (meth)acrylate comonomer.

13. The method according to claim 8, wherein the T(1hr) half-life of the first initiator is from 60°C to 130°C.

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