JPS6356895B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a rubber-modified styrenic resin composition with improved impact resistance. More specifically, the present invention relates to an improved rubber-modified styrenic resin composition produced using a bulk polymerization method or a bulk suspension polymerization method that has improved impact resistance and other properties. Currently, in order to improve the impact resistance performance of styrenic resins, rubber-modified styrenic resins containing rubber-like polymers as dispersed particles are manufactured in large quantities, and these products are widely used as molded products. In recent years, the field of demand for such products has expanded, and the demand for these products is increasing in fields that require impact resistance more than ever before. Furthermore, from the viewpoint of cost saving of molded products, there is a growing demand for products that are thinner than before and that have sufficient impact resistance. As one method for improving such impact resistance performance, a method has been disclosed in which one of the requirements is the addition of an organosilicon additive. For example, special public service 49-29947
Now let's talk about emulsion polymerized ABS resin with a specific structure and
A composition in which an organosilicon compound and a fatty acid metal salt are mechanically mixed in a system containing AS resin, is the same as that obtained by polymerizing by a solution polymerization method and devolatilizing by a steam distillation method. In order to obtain a certain level of impact resistance, liquid paraffin or polysiloxane is added to a rubber-modified thermoplastic resin solution and then passed through a separation and recovery process. JP-A-55-31896 discloses a composition in which a silicone urethane derivative is added to a specific ABS resin made of a mixture of a graft polymer and a thermoplastic resin. Each is disclosed. However, the special public service in 1977-
The method disclosed in No. 29947 is limited by the special manufacturing method and the use of additives, and the degree of improvement achieved in JP-A No. 53-124561 is not remarkable, and JP-A No. 55-3494
In JP-A No. 55-31896, there remain problems such as the scope of application is limited due to restrictions on special resins and additives, and application to styrenic resins in the currently required market fields cannot necessarily be expected. Nakatsuta. The present inventors have conducted extensive research on methods for improving the impact resistance of rubber-modified styrenic resin compositions produced using bulk polymerization or bulk-suspension polymerization, and have surprisingly identified a rubber In the modified styrenic resin composition, specifically, the rubber-modified styrenic resin composition has a particularly high impact strength, which is determined by the average particle diameter of the dispersed particles of the specific rubbery polymer, the amount of organic polysiloxane, and the dispersion state of the organic polysiloxane. The present invention was achieved by discovering that improvements can be seen in the following. That is, the present invention provides a rubber-modified styrenic resin composition produced using a bulk polymerization method or a bulk monosuspension polymerization method containing a rubbery polymer as dispersed particles. The average particle diameter of the dispersed particles of the polymer is 0.5 to 2.5μ, (b) the composition contains 0.002 to 0.2% by weight of the organic polysiloxane as silicon content, and (c) the organic polysiloxane in the composition is This rubber-modified styrenic resin composition is characterized in that when the dispersion state of siloxane is expressed by the coefficient of variation of silicon atom distribution in a cross-sectional photograph taken using an X-ray microanalyzer method, the coefficient of variation is 0.5 or less. The rubber-modified styrenic resin composition of the present invention is produced using any known bulk polymerization method or bulk suspension polymerization method, and in such a method, the organic polysiloxane can be added at any time as long as the requirements of the present invention are met. Added and mixed. For the purpose of the present invention, the bulk polymerization method or the bulk suspension polymerization method is a method with simple steps and pharmaceutical advantages. Therefore, a resin composition made by mixing another styrenic resin composition with a rubber-modified styrenic resin composition produced by a bulk polymerization method or a bulk suspension polymerization method also meets the requirement (a) of the present invention. , (b) and (c)
It is included in the present invention as long as it satisfies the following. To explain the bulk polymerization method with an example,
A styrenic monomer and a rubbery polymer, in some cases a solvent in an amount of up to 50% by weight, preferably up to 30% by weight of the styrenic monomer, and a molecular weight regulator, a polymerization initiator, etc. Continuously fed to the reactor, vigorous agitation is applied to convert the rubbery polymer into dispersed particles until 10-40% of the monomer is converted to polymer. After that, continue the reaction for 50~
The reaction is stopped when a monomer conversion rate of 99% is achieved, and a devolatilization operation is performed to remove unreacted monomers and, in some cases, solvent, followed by a granulation process. Granular resin is produced. In addition, to give an example of the bulk suspension polymerization method, a rubber-like polymer, and in some cases, a molecular weight regulator, a polymerization initiator, etc., are dissolved in a styrene monomer. Polymerization is carried out under stirring until ~40% is converted to polymer, converting the rubbery polymer into dispersed particles. Thereafter, water and a dispersant are added to suspend the above polymerization solution in the aqueous phase to continue polymerization. If necessary, perform devolatilization operation or heat treatment after polymerization to adjust the amount of residual volatile matter in the resin.
Adjust the degree of crosslinking of the rubbery polymer. Thereafter, granular resin is produced through dehydration, drying, and granulation steps. The granular resin is supplied to a molding machine as it is or mixed with other resins and additives, and a molded product of a rubber-modified styrenic resin composition is obtained. The dispersed particles of a rubbery polymer as used in the present invention are particles dispersed in a styrene resin, and these particles are made of a rubbery polymer and a styrene resin, and the styrene resin is a rubbery polymer. It is either grafted to the coalescence or occluded in the particle without grafting. The rubber-modified styrenic resin composition referred to in the present invention has an average particle size in the range of 0.5 to 2.5μ, preferably
It should contain dispersed particles of rubbery polymer in the range 0.5-1.5μ, more preferably in the range 0.6-1.2μ. If the average particle diameter is outside this range, the rubber-modified styrenic resin composition will not exhibit high impact properties and will not be covered by the present invention. The average particle diameter of the dispersed particles of the rubbery polymer in the rubber-modified styrenic resin composition is adjusted using any known method, for example, by adjusting the conversion rate of monomers to polymer in the manufacturing process of the composition. The reaction conditions at the stage of 10 to 40%, i.e., the intensity of stirring, the molecular weight of the produced polymer, the amount of molecular weight regulator, the amount of solvent, the molecular weight of the rubbery polymer used, the solution viscosity, the amount used, or the polymerization The amount and type of organic peroxide used as an initiator, etc.
It can be adjusted by changing. It can also be adjusted by mixing two or more resins containing different average particle diameters of dispersed particles of rubbery polymers. The average particle diameter of the dispersed particles of the rubbery polymer as used in the present invention is defined as follows. That is, an electron micrograph is taken of a rubber-modified styrenic resin composition using an ultra-thin section method, and the rubber-like polymer particles in the photograph are
The diameter of 200 to 500 particles was measured and calculated using the following formula. However, Di is the representative value of the i-th class when the measured values of particle diameter are classified into classes at 0.1μ intervals, average particle diameter = ΣniDi ² /ΣniDi, and the upper and lower Takes the intermediate value. Since the rubbery polymer particles seen in electron micrographs are not perfectly circular, the average value of the maximum and minimum diameters of the particles is treated as the particle size. ni
is the number of dispersed particles of rubbery polymer belonging to the i-th class. The rubbery polymer used in the present invention may be any polymer that exhibits rubbery properties at room temperature, such as polybutadienes, styrene-butadiene copolymers,
Blocked styrene-butadiene copolymers, ethylene-propylene copolymers, ethylene-propylene-nonconjugated diene terpolymers, isoprene polymers, styrene-isoprene copolymers, silicone rubbers, etc. One or more of these are used. Among these, polybutadienes are preferred, and polybutadiene structural units having a 1,4-cis structure of 20 to 40% or 95% or more are more preferably used, and 1,2-vinyl structures of 2% or more are used. or less or 7 to 20% is more preferably used. The molecular weight and degree of branching of the rubbery polymer are not particularly limited, but the viscosity when made into a 5% by weight styrene solution at 30°C is 20~20°C.
Preferably it is 300 cst, more preferably 20 to 100 cst. The rubber-modified styrenic resin composition of the present invention preferably contains 1 to 15% by weight of a rubbery polymer, although it is not particularly limited. 1% by weight
If it is less than that, the impact resistance performance is too low and the effect of the present invention is also small. On the other hand, if the content exceeds 15% by weight, the effects of the present invention will reach a plateau. The organic polysiloxane used in the present invention has the general formula (R ₁ and R ₂ are organic groups) is a polymer containing a repeating structural unit in its skeleton, and a variety of characteristic polymers with different skeletons, degrees of polymerization, and types of organic groups are known. Can be used in inventions. Examples of organic polysiloxanes used in the present invention include:
Polydimethylsiloxane, polymethylphenylsiloxane, polydiphenylsiloxane, monomer unit

[Formula] and

[Formula] (R ₃ , R ₄ , R ₅ , R ₆ are any combination of organic groups such as alkyl groups, phenyl groups, aralkyl groups, etc.)
Random, block or graft copolymers consisting of these organic polysiloxanes, or polymers in which epoxy groups, amino groups, carboxyl groups, hydroxyl groups, fluorine, alkoxy groups, or vinyl groups are introduced into the terminals or molecular chains are mentioned. It will be done.
These organic polysiloxanes may be used alone or in combination of two or more. Among them, polydimethylsiloxane and polymethylphenylsiloxane are preferred, and dimethylpolysiloxane is particularly preferably used. The molecular weight of such organic polysiloxane is not particularly limited, but it is preferably about 1,000 to 30,000 cst, and in the case of liquid organic polysiloxane, one with a viscosity of 100,000 to 100,000 cst at a temperature of 25°C is preferably used. , with a viscosity of 100 to 30,000 cst,
Particularly preferably, those having a viscosity of 100 to 10,000 cst are used. When an organic polysiloxane with a low viscosity is used, it tends to have a poor appearance when molded, and when it has a high viscosity, problems tend to occur in uniformly mixing it into the resin composition. If uniform mixing is incomplete, the effects of the present invention will be reduced. In the method of the present invention, the amount of the organic polysiloxane compound added must be 0.002 to 0.2% by weight, as silicon content, based on the total amount of the rubber-modified styrenic resin composition, preferably 0.003 to 0.05% by weight.
% by weight, particularly preferably in the range from 0.003 to 0.018% by weight. If it is less than 0.002% by weight, the present invention has no effect, and if it exceeds 0.2% by weight, the effect reaches a plateau.
Furthermore, the tensile strength and other properties of the resin are significantly reduced. The amount of silicon can be determined from the amount of organic polysiloxane added or by atomic absorption spectrometry of silicon atoms. Organic polysiloxane is more expensive than styrenic monomers, and is preferably used in the minimum amount necessary to maintain resin performance. In the rubber-modified styrenic resin composition of the present invention, the organic polysiloxane must be dispersed and held in the resin in a specific dispersion state. That is, when the dispersion state of the organopolysiloxane in the rubber-modified styrene resin composition is expressed as a coefficient of variation regarding silicon atom distribution in a cross-sectional photograph taken using an X-ray microanalyzer method, the coefficient of variation is 0.5 or less, preferably 0.4. Particularly preferably, the dispersion state should be 0.35 or less. The coefficient of variation is 0.5
If the dispersion state exceeds the above, the effect of the present invention will be reduced and no substantial effect will be seen. A cross-sectional photograph taken using the X-ray microanalyzer method referred to in the present invention is obtained by cutting out a cross section of a rubber-modified styrenic resin composition and irradiating its surface with an electron beam at an accelerating voltage of 10 to 20 KV and an electron current of 0.01 to 0.02 μA. The silicon atoms in the cross section are detected by the wavelength of the X-rays, and the distribution state of silicon atoms in the cross section of the sample is obtained by scanning the irradiation position of the electron beam, and the distribution state is visualized. In the present invention, the coefficient of variation (CV) regarding silicon atom distribution means that such a photograph is 5μ x 5μ
The area is divided into 30 to 60 square sections, and the relative value of the amount of silicon atoms present in each section is calculated using the following formula.

[Formula] = ΣXi/N However, Xi: relative value of the abundance of silicon atoms in the i-th division N: number of divisions to be measured The relative value of the abundance of silicon atoms in each division is the distribution state of silicon atoms. By calculating the area of the image showing the silicon atoms in the above photo showing the image or, if the image is composed of bright spots, calculating the number of bright spots in each section and comparing them,
Alternatively, in the process of obtaining the above-mentioned photograph, it can be obtained by using a counter that measures and records the amount of X-rays from silicon atoms attached to an X-ray microanalyzer to obtain and compare the measured values for each section. The coefficient of variation regarding the silicon atom distribution described above depends on the degree of mixing of the organic polysiloxane and the styrenic polymer constituting the rubber-modified styrenic resin composition in the process of manufacturing the rubber-modified styrenic resin composition of the present invention. The better the adjustment and mixing, the smaller the coefficient of variation appears to be. The mixing method itself can be performed by using any known method alone or in combination, such as a polymerization reaction step, a devolatilization step, a granulation step, a mixing step with other resins or additives, and a molding step. This is done in one or more steps, and the degree of mixing is determined by cross-sectional photographs taken with an X-ray microanalyzer. In order to carry out such mixing advantageously, the organic polysiloxane is added at a stage when the monomer conversion rate is in the range of 0 to 40%, and the granulation step is further carried out so as to reach the above-described value of the coefficient of variation of the present invention. It is preferable to use a mixer such as an extruder for adjustment. It is also preferable to mix the organic polysiloxane and the rubber-modified styrene resin using a twin-screw extruder or the like to adjust the coefficient of variation of the present invention. In the bulk polymerization method, it is preferable to add the organic polysiloxane in the devolatilization step and then pass it through a mixer such as an extruder or a static mixer to adjust the coefficient of variation of the present invention. In the bulk-suspension polymerization method, it is preferable to add organic polysiloxane in the step of granulating bead-like particles and control the mixing conditions so as to reach the coefficient of variation of the present invention. Alternatively, a styrenic resin composition containing a high concentration of organic polysiloxane, or a rubber-modified styrene-based resin composition and a rubber-modified styrene-based resin composition are mechanically kneaded to adjust the coefficient of variation of the present invention. The method is also preferred. In order to obtain a dispersion state of organopolysiloxane in which the coefficient of variation regarding silicon atom distribution in the rubber-modified styrenic resin composition of the present invention is 0.5 or less, conventionally used mixing conditions must be met in the various mixing methods described above. It is usually necessary to apply relatively more severe shear forces or longer mixing times. The composition referred to in the present invention is obtained by polymerizing a styrenic monomer in the presence of a rubbery polymer, or by combining a resin produced by such a method with a styrenic monomer that does not contain a rubbery polymer. It is manufactured by mixing the polymers of The styrenic monomer referred to in the present invention includes styrene and its derivatives, such as styrene, α-methylstyrene, o.
mp Vinyl-substituted or nuclear-substituted alkylstyrenes such as methylstyrene, ethylstyrenes, isopropylstyrenes, butylstyrenes, omp
Examples include vinyl group-substituted or nuclear-substituted halogenated styrenes such as bromustyrene and chlorostyrenes, and halogenated alkylstyrenes. Among them, styrene is preferably used. The present invention also includes a resin composition in which less than 35% by weight of the styrene monomer constituting the polymer of these styrenic monomers is replaced with another monomer copolymerizable with the styrene monomer. include. Examples of monomers copolymerizable with such styrene monomers include one or more of maleic anhydride, acrylic acids, methacrylic acids, alkyl esters thereof, acrylonitrile, methacrylonitrile, vinylidene cyanide, etc. is used. The rubber-modified styrenic resin composition referred to in the present invention can be used alone or in combination with other resins. For example, it may be used in combination with other styrene resins. In addition, heat, light, oxygen stabilizers, flame retardants, internal lubricants, plasticizers, colorants, lubricants, mold release agents, antistatic agents, etc. used in styrene resins are used within the range that satisfies the requirements of the present invention. They may be added and mixed at the same time. The rubber-modified styrenic resin composition of the present invention maintains extremely high impact resistance and has extremely high industrial utility value. Furthermore, the rubber-modified styrenic resin composition of the present invention has excellent photoselectivity and scratch resistance, and its commercial value is high. FIG. 1 shows the relationship between the Izod impact strength and the average particle diameter of dispersed particles of a rubbery polymer, and FIG. 2 shows the relationship between the Izod impact strength and the coefficient of variation regarding the silicon atom distribution. It is clear from FIGS. 1 and 2 that the rubber-modified styrenic resin composition produced using the bulk polymerization method or the bulk suspension polymerization method that satisfies requirements (a) and (b) of the present invention has significantly improved resistance. It can be seen that it has impact performance. Next, examples of the present invention will be shown. Example 1 Production of rubber-modified styrenic resin: A rubber-modified styrenic resin was produced in a continuous polymerization apparatus. The apparatus consisted of one stirring tank each having an internal volume of 3, a 3-stage column reactor, a devolatilization tank, an extruder, and a granulator connected in series. A solution of 8 parts by weight of a rubbery polymer (sample A-1) and 0.11 parts by weight of an organic polysiloxane (sample B-1) dissolved in 92 parts of styrene is supplied to a stirring tank. A mixed solution of 35 parts by weight of styrene and 30 parts by weight of ethylbenzene is supplied to the inlet of the second stage column reactor. The reaction temperature of the stirring tank was 132℃,
The outlet temperature of the three-stage tower reactor was set at 140°C, respectively.
The temperatures were 145°C and 155°C. The polymerization liquid discharged from the third column reactor was led to a devolatilization tank operated at a vacuum degree of 30 mmHg and an internal temperature of 220°C, where styrene and ethylbenzene were separated from the polymer. A gear pump was installed at the outlet of the devolatilization tank, and the molten rubber-modified styrenic resin composition was guided to an extruder and further passed through a granulation step to obtain a granular rubber-modified styrenic resin composition. The obtained granular resin was molded to obtain a test piece for performance measurement. Tables 1a and 1b show the trade names of the samples used in the Examples and Comparative Examples. Resin analysis, analysis, and performance evaluation: The thus obtained molded product was analyzed, analyzed, and performance evaluated using the following methods. [Viscosity average molecular weight] Dissolve the resin composition in methyl ethyl ketone, remove insoluble matter by centrifugation,
The soluble components are reprecipitated in methanol and measured after drying. [Swelling Index] A resin composition is dissolved in toluene, centrifuged, and then decanted to leave the insoluble matter. After measuring the weight of the gel swollen with toluene (W _s ), drying is performed, and then the weight of the dried gel (W _G ) is measured. Swelling index≡W _S /
W _C. [Rubbery polymer content] Calculated from the ratio of the amount of rubbery polymer used and the amount of the rubber-modified styrenic resin composition produced. [Scratch resistance] A rectangular box-like molded product measuring 7 cm x 11 cm x 1.7 cm is formed. Fill a large box with an inner volume of 7.5 cm x 11.5 cm x 36 cm with 20 box-like molded items, and then create a large box.
Place on a shaker for 20 minutes. The scratch state of the 20 box-shaped molded articles is visually judged and rated on a scale of 1 to 5 points, and the average value is taken as the scratch resistance value. A high score indicates good scratch resistance. The evaluation result is represented by ○ if the average value is 3 or more, and × if it is less than 3. [Impact resistance, gloss and tensile strength] respectively
ASTM-D-260, JIS-Z-8741, ASTM-D
- Measured according to 638. Table 2 shows the above analysis, analysis, and performance evaluation results. In the following Examples and Comparative Examples, resin analysis, analysis, and performance evaluation were performed in accordance with the above. Comparative Example 1 A molded product was obtained and evaluated in the same manner as in Example 1 except that the rotation speed of the stirring blade in the stirring tank was lowered. The results are shown in Table 2. Comparative Example 2 A molded product was obtained and evaluated in the same manner as in Example 1 except that no organic polysiloxane was added. The results are shown in Table 2. Example 2 A molded product was obtained and evaluated in the same manner as in Example 1, except that the rotation speed of the stirring blade in the stirring tank was increased. The results are shown in Table 2. Example 3 A molded product was obtained and evaluated in the same manner as in Example 1, except that the rotation speed of the stirring blade in the stirring tank was between that of Example 1 and Comparative Example 2. The results are shown in Table 2. Comparative Example 3 A molded product was obtained and evaluated in the same manner as in Example 3, except that the organic polysiloxane was not added in Example 2. The results are shown in Table 2. Comparative Example 4 A molded product was obtained and evaluated in the same manner as in Example 3, except that the rotation speed of the stirring blade in the stirring tank was further increased in Example 2. The results are shown in Table 2. Example 4 Production of a rubber-modified styrenic resin composition: Add 0.06 parts by weight of t-dodecyl mercaptan to a rubber solution consisting of 93.5 parts by weight of styrene, 6 parts by weight of a rubbery polymer (sample A-2), and 0.5 parts by weight of liquid paraffin. Part was subjected to bulk polymerization at 112°C for 8 hours. After adding 0.1 parts by weight of t-butyl perbenzoate and 0.25 parts by weight of di-t-butyl peroxide to this polymerization liquid, 100 parts by weight of water was added to disperse the polymerization liquid.
Thereafter, polymerization was carried out at 118°C for 3 hours and at 145°C for 2 hours to obtain bead-like particles. Addition of organic polysiloxane: 10 parts by weight of organic polysiloxane (Sample B-2) and 90 parts by weight of homopolystyrene with an average molecular weight of 120,000 were kneaded in a twin-screw extruder under adjusted conditions to produce master pellets. .
0.4 parts by weight of the master pellets and 99 parts by weight of the above bead-like particles were mixed, and a granular rubber-modified styrenic polymer composition was obtained using an extruder and a granulator. This composition was molded using a molding machine and evaluated. Example 5 In Example 4, after mixing bead-like particles and 0.04 parts by weight of organic polysiloxane (sample B-3), a granular rubber-modified styrenic resin composition was obtained using an extruder and a granulator. A molded product was obtained and evaluated in the same manner as in Example 4 except for the following. The results are shown in Table 2. Comparative Example 5 In Example 4, a granular rubber-modified styrenic resin composition was obtained by using an extruder and a granulator for bead-like particles, and 99 parts by weight of the composition and 0.4 parts by weight of the master pellets of Example 4 were added. Except for mixing the parts, sending it to the molding machine, obtaining the molded product, and performing the evaluation.
The same operation as in Example 4 was performed. The results are shown in Table 2.

【table】

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 shows the relationship between the Izot impact strength of the compositions of the present invention and compositions not included in the present invention and the average particle diameter of dispersed particles of rubbery polymer. In the figure, ○: composition of the present invention, ●: composition outside the scope of the present invention. Subscript: Silicon content. FIG. 2 shows the relationship between the Izod impact strength and the coefficient of variation regarding the silicon atom distribution. In the figure, ○: composition of the present invention, ●: composition outside the scope of the present invention.

Claims (1)

[Scope of Claims] 1. A rubber-modified styrenic resin composition produced by a bulk polymerization method or a bulk monosuspension polymerization method containing a rubber-like polymer as dispersed particles, which includes: (a) a rubber-like polymer in the composition; the average particle diameter of the dispersed particles of the polymer is 0.5 to 2.5μ, (b) the composition contains 0.002 to 0.2% by weight of the organic polysiloxane as silicon content, and (c) the organic polysiloxane in the composition 1. A rubber-modified styrenic resin composition characterized in that when the dispersion state of siloxane is expressed by the coefficient of variation of silicon atom distribution in a cross-sectional photograph taken by an X-ray microanalyzer method, the coefficient of variation is 0.5 or less.