KR20230170784A - Transparent rubber-modified styrene-based resin composition - Google Patents

Abstract

A rubber-modified styrene-based resin composition having excellent transparency and surface impact strength is provided.
According to the present invention, a rubber-modified styrene-based resin composition containing a continuous phase containing a styrene-based copolymer and dispersed particles containing a rubber-like polymer, wherein the styrene-based copolymer includes a styrene-based monomer unit and one type of A rubber-modified styrene-based resin composition is provided, which has the above (meth)acrylic acid ester monomer units, the graft ratio of the rubber-modified styrene-based resin composition is 2.12 to 2.40, and the hydrogenation rate of the rubbery polymer is less than 7 mol%.

Description

Transparent rubber-modified styrene-based resin composition

The present invention relates to a rubber-modified styrene-based resin composition containing a continuous phase containing a styrene-based copolymer and dispersed particles containing a rubber-like polymer.

High impact polystyrene (HIPS), one of the rubber-modified styrene-based resin compositions with excellent impact resistance, is obtained by graft copolymerization of styrene monomer in the presence of polybutadiene, but due to the difference in refractive index of dispersed particles containing continuous polystyrene and polybutadiene, It is unclear because In order to match the refractive index of the continuous phase and the dispersed particles, a transparent rubber-modified styrene-based resin composition can be obtained by copolymerizing (meth)acrylic acid ester monomer units in the continuous phase and using styrene-butadiene rubber copolymerized with styrene in the dispersed particles. It has various properties such as transparency, impact resistance, and rigidity, and is used in a wide range of fields. Because of its excellent formability, molded bodies are often made by injection molding, but there are problems with surface impact strength related to practical strength.

Japanese Patent No. 4663107 Publication Japanese Patent No. 4386772 Publication Japanese Patent No. 3618876 Publication Japanese Patent No. 3151481 Publication Japanese Patent Publication No. 2004-520459

The object of the present invention is to provide a rubber-modified styrene-based resin composition excellent in transparency, surface impact strength, and Charpy impact strength.

According to the present invention, a rubber-modified styrene-based resin composition containing a continuous phase containing a styrene-based copolymer and dispersed particles containing a rubber-like polymer, wherein the styrene-based copolymer includes a styrene-based monomer unit and one type A rubber-modified styrene-based resin composition is provided, which has the above (meth)acrylic acid ester monomer units, the graft ratio of the rubber-modified styrene-based resin composition is 2.12 to 2.40, and the hydrogenation rate of the rubbery polymer is less than 7 mol%.

Below, various embodiments of the present invention are illustrated. The embodiments shown below can be combined with each other.

(1) A rubber-modified styrene-based resin composition containing a continuous phase containing a styrene-based copolymer and dispersed particles containing a rubber-like polymer, wherein the styrene-based copolymer includes a styrene-based monomer unit and one or more types of ( A rubber-modified styrene-based resin composition comprising a meth)acrylic acid ester monomer unit, the graft ratio of the rubber-modified styrene-based resin composition being 2.12 to 2.40, and the hydrogenation rate of the rubbery polymer being less than 7 mol%.

(2) The rubber-modified styrene-based resin composition according to (1), wherein the haze of the 2 mm thick molded body is 5% or less.

(3) The rubber-modified styrene-based resin composition according to (1) or (2), wherein the rubber-like polymer is a styrene-butadiene rubber-based copolymer.

(4) The rubber-modified styrene-based resin composition according to (3), wherein the content of styrene monomer units in the styrene-butadiene rubber-based copolymer is 10 to 50% by mass.

(5) The rubber-modified styrene-based resin composition according to any one of (1) to (4), which has a refractive index of 1.53 to 1.57.

(6) The method according to any one of (1) to (5), wherein the styrene-based copolymer contains 35 to 75% by mass of the styrene-based monomer units and 25 to 65% by mass of the (meth)acrylic acid ester-based monomer units. A rubber-modified styrene-based resin composition having:

The rubber-modified styrene-based resin composition of the present invention is excellent in transparency, surface impact strength, and Charpy impact strength, and a molded article with high appearance and practical strength can be obtained. Additionally, it has excellent fluidity and is particularly suitable for injection molding applications.

<Explanation of terms>

In this specification, for example, the description “A to B” means more than A and less than or equal to B.

Hereinafter, embodiments of the present invention will be described in detail.

The resin composition of the present invention is a rubber-modified styrene-based resin composition containing a continuous phase containing a styrene-based copolymer and dispersed particles containing a rubber-like polymer, wherein the styrene-based copolymer contains a styrene-based monomer unit, 1 It is a transparent rubber-modified styrene resin composition containing more than one species of (meth)acrylic acid ester monomer unit.

A styrene-based monomer unit is a unit derived from a styrene-based monomer used in polymerization. Styrene-based monomer units include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, and α-methyl-p. -Methyl styrene, etc. Among these, styrene is preferable. The styrene-based monomer unit may be used alone or in combination of two or more types.

The (meth)acrylic acid ester monomer unit is a unit derived from the (meth)acrylic acid ester monomer used in polymerization. (meth)acrylic acid ester-based monomers include (meth)acrylic acid ester of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, methyl acrylate, There are ethyl acrylate, n-butyl acrylate, 2-methylhexyl acrylate, 2-ethylhexyl acrylate, and decyl acrylate alone or in mixtures of two or more. From the viewpoint of excellent color tone and heat resistance, it is preferable to use methyl (meth)acrylate as the main component. Additionally, in one embodiment, the (meth)acrylic acid ester-based monomer unit preferably contains methyl (meth)acrylate and n-butyl acrylate.

The styrene-based copolymer constituting the continuous phase is a copolymer having a styrene-based monomer unit and one or more types of (meth)acrylic acid ester-based monomer units. Although the styrene-based copolymer has styrene-based monomer units as its main component and contains one or more types of (meth)acrylic acid ester-based monomer units, it is preferred to contain two or more types of (meth)acrylic acid ester-based monomer units and has excellent heat resistance. The fluidity of the rubber-modified resin composition can be improved by using a component with excellent fluidity in combination. For example, styrene-methyl (meth)acrylate-butyl acrylate copolymer.

Rubber-like polymers exhibit rubbery properties at room temperature and include, for example, those having a butadiene component such as polybutadiene and styrene-butadiene rubber-based copolymers, but are preferably styrene-butadiene rubber or styrene-butadiene block. It is a styrene-butadiene rubber-based copolymer containing styrene monomer units such as rubber (block copolymer) and butadiene monomer units. The content of the styrene monomer unit in the styrene-butadiene rubber-based copolymer is preferably 10 to 50 mass%, more preferably 30 to 45 mass%. Specifically, the content of the styrene monomer unit of the styrene-butadiene rubber-based copolymer is, for example, 10, 15, 20, 25, 30, 35, 40, 45, and 50% by mass, and any two of the values exemplified here It can be within the range between dogs. In addition, some of the unsaturated units such as butadiene monomer units contained in the rubbery polymer may be hydrogenated, but the proportion of hydrogenated units among the unsaturated units contained (hydrogenation rate) is less than 7 mol%, preferably 5 mol%. It is mol% or less, and more preferably, it is 1 mol% or less.

A rubber-modified styrene-based resin composition can be obtained by graft copolymerization of a styrene-based monomer and a (meth)acrylic acid ester-based monomer in the presence of a rubber-like polymer. The method of graft copolymerization can be a method used for producing high impact polystyrene (HIPS). The production of HIPS is often carried out by continuous polymerization. For example, a rubber-like polymer is dissolved in a polymerization solvent along with a styrene-based monomer and a (meth)acrylic acid ester-based monomer to create a raw material solution, and then continuously added to the reactor. Supply and carry out graft copolymerization. After going through a phase inversion in which dispersed particles are formed as polymerization progresses, a polymerization reaction is further performed. The polymerization solution discharged from the reactor is supplied to the devolatilization process, which removes unreacted monomers and polymerization solvent and simultaneously crosslinks the rubbery polymer constituting the dispersed particles. Examples of the reactor include a completely mixed tank reactor, a tower reactor with plug flow, and a loop reactor in which a portion of the polymerization solution is extracted while polymerization progresses. There are no particular restrictions on the arrangement order of these reactors. The devolatilization process consists of a vacuum devolatilizer equipped with a heater or a devolatilizer extruder equipped with a vent. The molten resin from the devolatilization process is transferred to the granulation process. In the assembly process, molten resin is extruded from a porous die onto a strand, and processed into a pellet shape using a cold cutting method, an air hot cutting method, or an underwater cutting method. One or more polymerization reactors are arranged continuously, but in the case of one polymerization reactor, they may be arranged singly, and in the case of two or more, at least two are arranged continuously (in series).

To control the polymerization reaction, a polymerization solvent, polymerization initiator, and chain transfer agent can be used. The polymerization solvent is used to adjust the polymerization rate, adjust the molecular weight, and reduce the viscosity of the polymerization solution, for example, alkylbenzenes such as benzene, toluene, ethylbenzene, and xylene, acetone, methyl ethyl ketone, etc. Ketones, aliphatic hydrocarbons such as hexane and cyclohexane can be used. The amount of the polymerization solvent used is not particularly limited, but is usually preferably 1 to 50% by mass, and more preferably 3 to 25% by mass, as the composition in the polymerization reactor. If it exceeds 50% by mass, productivity may decrease significantly or the molecular weight of the rubber-modified styrene-based resin composition may decrease excessively.

The polymerization initiator is preferably a radical polymerization initiator, and examples of known and common polymers include 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, and 2,2-di(t-butylperoxy)butane. -Peroxyketals such as di(4,4-di-t-butyl)peroxycyclohexyl)propane, 1,1-di(t-amylperoxy)cyclohexane, cumene hydroperoxide, and t-butylhydride. Hydroperoxides such as roperoxide, alkyl peroxides such as t-butyl peroxyacetate and t-amyl peroxyisononanoate, t-butylcumyl peroxide, di-t-butyl peroxide, dicumyl peroxide, Dialkyl peroxides such as di-t-hexyl peroxide, peroxyesters such as t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyisopropyl monocarbonate, and t-butyl peroxide. Peroxycarbonates such as oxyisopropyl carbonate and polyether tetrakis (t-butyl peroxycarbonate), N,N'-azobis(cyclohexane-1-carbonitrile), N,N'-azobis(2) -methylbutyronitrile), N,N'-azobis(2,4-dimethylvaleronitrile), N,N'-azobis[2-(hydroxymethyl)propionitrile], etc., One or two or more of these can be used in combination. Examples of chain transfer agents include aliphatic mercaptan, aromatic mercaptan, pentaphenylethane, α-methylstyrene dimer, and terpinolene.

The graft ratio of the rubber-modified styrene-based resin composition is 2.12 to 2.40, and is preferably 2.15 to 2.35. If the graft ratio is less than 2.12, the cotton impact strength and transparency may decrease, and if it exceeds 2.40, the Charpy impact strength may decrease. The graft ratio is, for example, 2.12, 2.13, 2.14, 2.15, 2.16, 2.17, 2.18, 2.19, 2.20, 2.25, 2.30, 2.35, 2.40, and may be within the range between any two of the values exemplified here. The graft ratio is calculated from the gel powder and rubber powder as graft ratio = (gel powder - rubber powder)/rubber powder, and represents the ratio of components other than rubber per unit rubber powder. Components other than rubber include components such as styrene bonded to rubber, grafted styrene-based copolymers, and encapsulated styrene-based copolymers. The grafting rate can be adjusted by the composition of the rubber polymer used, the content of 1,2-vinyl bonds, the type and amount of polymerization initiator added initially, the type of reactor that forms the rubber particles, etc. However, in addition, the transfer rate It can also be adjusted depending on the type and amount of polymerization initiator added to the subsequent polymerization solution.

The gel content indicates the content of dispersed particles, and 1 g of the rubber-modified styrene resin composition was weighed (mass (W)), and 35 ml of a 50% methyl ethyl ketone/50% acetone mixed solution was added and dissolved. The solution was centrifuged at 14000 rpm for 30 minutes using a centrifuge (H-2000B (rotor: H) manufactured by Kokusan Co., Ltd.) to precipitate the insoluble matter, and the supernatant was removed by decantation to obtain the insoluble matter. Preliminarily dry at 90°C for 2 hours in a safety oven, vacuum dry again at 120°C for 1 hour in a vacuum dryer, cool in a desiccator for 20 minutes, and measure the mass (G) of the dried insoluble matter. It can be obtained as follows.

Gel content (mass%) = (G/W)Х100

In addition, the supernatant separated by decantation was placed in a 300 ml beaker, 250 ml of methanol was rapidly added to re-precipitate the polymer powder, the precipitated polymer was suction filtered through a filter, and the polymer on the filter was placed in a vacuum dryer for 1.5 hours. It was vacuum dried and used to measure the monomer units and weight average molecular weight of the styrene resin constituting the continuous phase described later.

When the rubber-like polymer is a polymer containing a butadiene monomer unit, the rubber powder is calculated as a butadiene component (butadiene monomer unit), and the rubber-modified styrene-based resin composition is dissolved in chloroform and a certain amount of iodine monochloride/carbon tetrachloride solution is added. was added, left in a dark place for about 1 hour, potassium iodide solution was added, excess iodine monochloride was titrated with 0.1N sodium thiosulfate/ethanol aqueous solution, and the butadiene component was calculated from the amount of addition-reacted iodine monochloride. The content can be obtained.

The swelling ratio (SR) of the rubber-modified styrene-based resin composition is preferably 8 to 12. The swelling ratio indicates the degree of cross-linking of the dispersed particles. If it is less than 8, the impact resistance may decrease, and if it exceeds 12, the appearance may deteriorate. The swelling ratio (SR) was determined by weighing 1 g of rubber-modified styrene resin, dissolving it by adding 30 ml of toluene, and centrifuging the solution (H-2000B (rotor: H) manufactured by Kokusan Co., Ltd.) at 30 rpm at 14,000 rpm. The insoluble matter was sedimented by centrifugation for several minutes, the supernatant was removed by decantation, and the mass (S) of the insoluble matter swollen with toluene was measured. Then, the insoluble matter swollen with toluene was placed in a safety oven at 90°C for 2 hours. After pre-drying for a while, vacuum drying again at 120°C for 1 hour in a vacuum dryer, cooling in a desiccator for 20 minutes, and measuring the dry mass (D) of the insoluble matter can be obtained as follows.

Swelling ratio (SR) = S/D

The particle diameter of the dispersed particles containing the rubbery polymer is preferably 0.2 to 2.0 μm, more preferably 0.4 to 1.5 μm. If the particle diameter is less than 0.2 μm, impact resistance may decrease, and if it exceeds 2.0 μm, appearance such as transparency may deteriorate. The particle diameter was determined by cutting an ultra-thin section from a pellet of the rubber-modified styrene-based resin composition, observing it with a transmission electron microscope (TEM), and analyzing images of particles dispersed in a continuous phase, and was equivalent to a circle of about 2,000 particles. This is the value calculated by measuring the diameter (Di) using the formula below.

Particle diameter = Σni·Di ⁴ /Σni·Di ³

The particle diameter can be adjusted by the composition of the rubber-like polymer used, the content of 1,2-vinyl bonds, the number of reactor agitation during phase transfer in which the dispersed particles are formed, and the type and addition amount of the polymerization initiator and chain transfer agent added before phase transfer.

The monomer units of the styrene-based copolymer constituting the continuous phase are preferably 35 to 75% by mass of styrene-based monomer units and 25 to 65% by mass of (meth)acrylic acid ester-based monomer units, and more preferably, styrene-based monomers. The unit is 45 to 70% by mass, and the (meth)acrylic acid ester monomer unit is 30 to 55% by mass. If the structural unit is within the above range, the obtained rubber-modified styrene-based resin composition has an excellent balance of physical properties such as transparency, impact resistance, and fluidity. The structural unit constituting the continuous phase is a value measured by 13C-NMR using a reprecipitate of the supernatant excluding the gel content obtained by measuring the gel content. The monomer units of the styrene resin constituting the continuous phase can be adjusted depending on the composition of the raw materials used for polymerization.

The weight average molecular weight of the styrene-based copolymer constituting the continuous phase is preferably 80,000 to 220,000, and more preferably 120,000 to 180,000, from the viewpoint of the strength and moldability of the rubber-modified styrene-based resin composition. The weight average molecular weight is a value in terms of polystyrene measured in a THF solvent using gel permeation chromatography (GPC), and was measured under the following conditions using the reprecipitate of the supernatant excluding the gel content obtained from the measurement of the gel content. .

Device name: SYSTEM-21 Shodex (manufactured by Showa Denko Co., Ltd.)

Column: 3 PL gel MIXED-B in series

Temperature: 40℃

Detection: Differential refractive index

Solvent: Tetrahydrofuran

Concentration: 2% by mass

Calibration curve: Produced using standard polystyrene (PS) (manufactured by PL).

The haze of the 2 mm thick molded body of the rubber-modified styrene-based resin composition is preferably 5% or less, and more preferably 2% or less. Haze uses an injection molding machine (IS-50EP manufactured by Toshiba Machine Co., Ltd.) to form a mirror surface plate measuring 90 mm long, 55 mm wide, and 2 mm thick, molded under molding conditions of a cylinder temperature of 230°C and a mold temperature of 60°C, according to ASTM. The haze was measured using a haze meter (NDH-1001DP manufactured by Nippon Denshoku Industries, Ltd.) in accordance with D1003.

The refractive index of the rubber-modified styrene-based resin composition is preferably 1.53 to 1.57, and more preferably 1.54 to 1.56. If the refractive index is within the above range, the resulting rubber-modified styrene-based resin composition has an excellent balance of transparency and physical properties such as impact resistance and fluidity. The refractive index can be measured by manufacturing a molded product with a thickness of 2 mm and using an Abbe refractometer.

The rubber-modified styrene-based resin composition contains dyes such as bluing agents, plasticizers, hindered phenolic antioxidants, phosphorus-based antioxidants, ultraviolet absorbers, hindered amine-based light stabilizers, antistatic agents, and stearic acid within the range that does not impair transparency. Internal lubricants such as, external lubricants such as ethylene bistearamide, MS resin, MBS resin, emulsified graft copolymer, etc. may be added.

The rubber-modified styrene-based resin composition can be used to produce molded articles using known molding methods, but has excellent fluidity, so it is particularly preferable to use it for injection molding.

[Example]

Hereinafter, details will be explained using examples, but the present invention is not limited to the following examples.

(Examples 1 to 5, Comparative Examples 1 to 3)

The first and second reactors, which were completely mixed-type stirring tanks, and the third reactor, which was a tower-type plug flow reactor equipped with stirring blades, were connected in series to constitute a polymerization process. The capacity of each reactor was 5L for the first reactor, 15L for the second reactor, and 40L for the third reactor. A raw material solution was prepared with the raw material composition shown in Table 1, and the raw material solution was continuously supplied to the first reactor at the flow rate shown in Table 1. The rubber-like polymer was Asahi Kasei Co., Ltd. ASAPRENE 670A (styrene-butadiene block rubber, styrene content of 40% by mass, 5% by mass styrene solution viscosity at 25°C, 32 mPa·s, A 1,2-vinyl bond ratio of 13.5 mol% and a hydrogenation rate of 0 mol% were used. The polymerization initiator and chain transfer agent were added to the raw material solution at the inlet of the first reactor and the third reactor so that the addition concentration (concentration based on mass relative to the raw material supply flow rate) shown in Table 1 was uniformly mixed. In Table 1, polymerization initiator-1 is 1,1-bis(t-butylperoxy)-cyclohexane (Perhexa C manufactured by Nichiyu Co., Ltd. was used), and polymerization initiator-2 is t-butyl. It is cumyl peroxide (perbutyl C manufactured by Nichiyu Co., Ltd. was used), and the chain transfer agent is n-dodecyl mercaptan. The reaction temperature was adjusted in the tank to the temperature shown in Table 1, and in the third reactor, it was adjusted by providing a gradient so that the inlet temperature was 130°C and the outlet temperature was 165°C. Next, the polymerization solution continuously taken out from the third reactor is introduced into a vacuum devolatilizer equipped with a preheater, the temperature of the preheater is adjusted so that the resin temperature is 230°C, and the pressure in the devolatilization tank is adjusted to 1 kPa, thereby removing unreacted styrene and After separating ethylbenzene (EB), it was extruded from a porous die into a strand shape, and the strands were cooled and cut using a cold cutting method to pelletize them to obtain a rubber-modified styrene-based resin composition. Table 2 shows the measurements and evaluations of the obtained rubber-modified styrene-based resin composition and the styrene-based copolymer contained therein.

(rubber powder)

The content (% by mass) of the butadiene component was calculated as rubber powder. The rubber-modified styrene-based resin composition was dissolved in chloroform, a certain amount of iodine monochloride/carbon tetrachloride solution was added, left in a dark place for about 1 hour, potassium iodide solution was added, and excess iodine monochloride was dissolved in 0.1N thiochloride solution. It was titrated with sodium sulfate/ethanol aqueous solution and determined from the amount of iodine monochloride added.

(gel powder)

1 g of the rubber-modified styrene-based resin composition was weighed (mass (W)) and dissolved by adding 35 ml of a 50% methyl ethyl ketone/50% acetone mixed solution. The solution was centrifuged at 14000 rpm for 30 minutes using a centrifuge (H-2000B (rotor: H) manufactured by Kokusan Co., Ltd.) to precipitate the insoluble matter, and the supernatant was removed by decantation to obtain the insoluble matter. The insoluble matter was preliminarily dried in a safety oven at 90°C for 2 hours, then vacuum dried in a vacuum dryer at 120°C for 1 hour, cooled in a desiccator for 20 minutes, and the mass (G) of the dried insoluble matter was calculated as Measured. Using G and W, the gel content was calculated based on the following equation.

Gel content (mass%) = (G/W)Х100

(graft rate)

The graft rate was calculated based on the following equation.

Graft rate = (gel powder - rubber powder)/rubber powder

(Swelling ratio (SR))

The swelling ratio (SR) was determined by weighing 1 g of rubber-modified styrene resin, dissolving it by adding 30 ml of toluene, and centrifuging the solution (H-2000B (rotor: H) manufactured by Kokusan Co., Ltd.) at 30 rpm at 14,000 rpm. The insoluble matter was sedimented by centrifugation for several minutes, the supernatant was removed by decantation, and the mass (S) of the insoluble matter swollen with toluene was measured. Then, the insoluble matter swollen with toluene was placed in a safety oven at 90°C for 2 hours. After pre-drying for a while, it was vacuum-dried again at 120°C for 1 hour in a vacuum dryer, cooled in a desiccator for 20 minutes, and then the dry mass (D) of the insoluble matter was measured and calculated based on the following formula.

Swelling ratio (SR) = S/D

(Rubber particle size)

The particle diameter was determined by cutting an ultra-thin section from a pellet of the rubber-modified styrene-based resin composition, observing it with a transmission electron microscope (TEM), and calculating the equivalent circular diameter (Di) of about 2,000 particles from image analysis of particles dispersed in a continuous phase. It was measured and calculated using the formula below.

Particle diameter = Σni·Di ⁴ /Σni·Di ³

(refractive index)

The refractive index was measured by producing a molded product with a thickness of 2 mm and using an Abbe refractometer in accordance with JIS K 7142.

(Weight average molecular weight)

The weight average molecular weight of the styrene-based copolymer constituting the continuous phase is a polystyrene conversion value measured in a THF solvent using gel permeation chromatography (GPC), and is the value of the supernatant excluding the gel content obtained from the measurement of the gel content. Measurements were made using re-precipitated material under the following conditions.

Device name: SYSTEM-21 Shodex (manufactured by Showa Denko Co., Ltd.)

Column: 3 PL gel MIXED-B in series

Temperature: 40℃

Detection: Differential refractive index

Solvent: Tetrahydrofuran

Concentration: 2% by mass

Calibration curve: Produced using standard polystyrene (PS) (manufactured by PL).

In the measurement of the gel content, the supernatant separated by decantation is placed in a 300 ml beaker, 250 ml of methanol is rapidly added, the polymer content is reprecipitated, and the precipitated polymer content is suction filtered through a filter. The upper polymer was placed in a vacuum dryer and vacuum dried for more than 1.5 hours.

(Styrene content · MMA content)

The content of styrene monomer units (styrene content) and the content of methyl methacrylate monomer units (MMA content), which are structural units of the styrenic copolymer constituting the continuous phase, were obtained by measuring the gel content, and were obtained by reprecipitating the supernatant excluding the gel content. Measurement was made by 13C-NMR using water. Regarding the reprecipitated material, it is the same as the reprecipitated material in terms of (weight average molecular weight). In addition, the structural unit of the styrene-based copolymer includes n-butyl acrylate (n-BA) as a (meth)acrylic acid ester-based monomer unit, and the content of n-butyl acrylate is calculated from 100% by mass as the styrene content. This is the amount minus the MMA content.

(melt mass flow rate)

The melt mass flow rate was measured at 200°C and a 49N load based on JIS K7210.

(Hayes)

Using an injection molding machine (IS-50EP manufactured by Toshiba Machine Co., Ltd.), a mirror-surface plate with a length of 90 mm, a width of 55 mm, and a thickness of 2 mm was molded under molding conditions of a cylinder temperature of 230°C and a mold temperature of 60°C, in accordance with ASTM D1003. Haze was measured using a haze meter (model NDH-1001DP manufactured by Nippon Denshoku Industries, Ltd.).

(Charpy impact strength)

Charpy impact strength was measured based on JIS K7111-1 using a notched test piece and using edge wise as the hitting direction. Additionally, a digital impact tester manufactured by Toyo Seiki Manufacturing Co., Ltd. was used as the measuring instrument.

(Cotton Impact Strength)

Using an injection molding machine (IS-55EPN manufactured by Toshiba Machine Co., Ltd.), a test piece (film gate) measuring 90 mm long, 90 mm wide, and 2 mm thick was molded under the molding conditions of cylinder temperature 230°C, mold temperature 60°C, and injection speed 70%. ), a surface impact test was conducted using a high-speed punching impact tester (HITS-PX) manufactured by Shimadzu Corporation. Under the conditions of 23℃, striker diameter 12.7mm (ASTM D3763), and piston speed 5m/sec, the central part of the test specimen fixed to the clamp is destroyed by impact, and the energy absorbed until it reaches the maximum impact point is calculated as the impact strength. I did it.

(flexural modulus)

The bending elastic modulus was measured at a bending speed of 2 mm/min based on JIS K7171.

From the results in Table 2, the rubber-modified styrene-based resin compositions of the examples are excellent in transparency, surface impact strength, and Charpy impact strength.

By using the rubber-modified styrene-based resin composition of the present invention, a molded article that is transparent and has excellent impact resistance can be obtained. In addition, because it has excellent fluidity, it is especially suitable for injection molding, and has excellent surface impact strength, so it can be used for housings of home appliances, etc.

Claims (6)

A rubber-modified styrene-based resin composition containing a continuous phase containing a styrene-based copolymer and dispersed particles containing a rubber-like polymer,
The styrene-based copolymer has a styrene-based monomer unit and one or more types of (meth)acrylic acid ester-based monomer units,
The graft ratio of the rubber-modified styrene-based resin composition is 2.12 to 2.40,
The hydrogenation rate of the rubbery polymer is less than 7 mol%,
Rubber-modified styrene-based resin composition. According to paragraph 1,
A rubber-modified styrene-based resin composition having a haze of 5% or less in a 2 mm thick molded body. According to paragraph 1,
A rubber-modified styrene-based resin composition, wherein the rubber-like polymer is a styrene-butadiene rubber-based copolymer. According to paragraph 3,
A rubber-modified styrene-based resin composition wherein the content of styrene monomer units in the styrene-butadiene rubber-based copolymer is 10 to 50% by mass. According to paragraph 1,
A rubber-modified styrene-based resin composition having a refractive index of 1.53 to 1.57. According to any one of claims 1 to 5,
A rubber-modified styrene-based resin composition, wherein the styrene-based copolymer has 35 to 75% by mass of the styrene-based monomer units and 25 to 65% by mass of the (meth)acrylic acid ester-based monomer units.