JPH038388B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a thermoplastic resin composition that has excellent heat resistance and impact resistance, and also has a good balance with moldability. A number of thermoplastic resins are widely used today. A typical example is ABS resin, which is a rubber-modified thermoplastic resin. However, ABS
Resin is still insufficient in terms of heat resistance, and in fields that require high heat resistance, the composition of ABS resin is
- So-called heat-resistant ABS that incorporates methylstyrene
Resin is used. These heat-resistant ABS resins are generally obtained by blending α-methylstyrene, acrylonitrile copolymer, and a graft copolymer obtained by copolymerizing aromatic vinyl monomer and acrylonitrile in the presence of rubber at a certain ratio. It is true. However, in conventional heat-resistant ABS resins, although heat resistance increases when the α-methylstyrene content is increased, there is a drawback in that impact strength decreases, and when the rubber content is increased in an attempt to improve these drawbacks, moldability becomes extremely poor. Become. In addition, one way to increase heat resistance and impact resistance is to increase the molecular weight of the α-methylstyrene-acrylonitrile copolymer, but even with this method, the moldability increases exponentially as the molecular weight increases. descend. When thermoplastic resin is used, it is generally used as some kind of molded product. Therefore, it goes without saying that moldability and processability are important factors when making the resin into an actual molded product, but for example, in molding methods such as injection molding, the moldability of the resin is important as it becomes a molded product. has a great influence on the practical physical properties of In the test piece test, the resin with excellent heat resistance has poor moldability, so in the heat resistance test of the molded product, due to residual stress, in the test piece test, it is easier to use at a lower temperature than the resin with poor heat resistance. It is a common case that it transforms into Furthermore, if the physical properties are set with an actual view of fluidity and impact resistance, the heat resistance of the resin itself inevitably decreases, making it impossible to obtain a resin suitable for use in high-temperature environments. Therefore, in heat-resistant ABS resin systems, it has been an important issue to balance the three factors of heat resistance, impact resistance, and moldability. However, in the heat-resistant ABS resin system, which currently has the highest heat resistance with a Vikatsu softening point of 125℃, the Izot strength is 10Kg.
-cm/cm, and the flow length of the Archimedean circle at a cylinder temperature of 280℃ using an injection molding machine (Kawaguchi Churchill 1040S manufactured by Kawaguchi Iron Works Co., Ltd., injection pressure: 50KgG/cm ² , mold temperature: 40℃) (hereinafter referred to as "spiral flow test") is approximately 22 cm. In addition, heat-resistant ABS has excellent impact resistance compared to existing materials.
For resin systems, the Izot impact strength is 15 to 16 kg−
cm/cm, but in that case the Vikatsu softening point is 115
℃, the flow length of the spiral flow test under the same conditions as above is approximately 35cm, and when the Vikatsu softening point is 120℃, the flow length of the spiral flow test is approximately 24cm.
It is. In this way, conventionally, heat-resistant ABS resins
Among the three factors of heat resistance, impact resistance, and formability,
There was a drawback that when two properties were directed in a positive direction, the other one worsened. Therefore, it has been extremely difficult to obtain a balance between heat resistance, impact resistance, and moldability in heat-resistant ABS resins. In order to solve these problems, the present inventor conducted extensive research on thermoplastic resins that have excellent heat resistance and impact resistance, and also has a good balance with moldability. It consists of components A and B, which are polymers, and component C, which is a graft polymer whose backbone polymer is a rubbery polymer mainly composed of polybutadiene, and component A is α-methylstyrene or 20% by weight.
50 to 80 parts by weight of a main component consisting of α-methylstyrene, including the following aromatic vinyl monomers, 15 to 35 parts by weight of vinyl cyanide monomer, and 0 monomers copolymerizable with these. It is a copolymer containing ~30 parts by weight of α-methylstyrene as an essential component, and has a number average chain length (based on polystyrene).
n) is in the range of 1200 to 1600 Å, and the ratio of weight average chain length (w) to number average chain length w/
n is in the range of 1.8 to 3.5, and component B is α-methylstyrene or a monomer mainly composed of α-methylstyrene containing 20% by weight or less of an aromatic vinyl monomer. A copolymer containing α-methylstyrene as an essential component, consisting of 15 to 35 parts by weight of a vinyl cyanide monomer, and 0 to 30 parts by weight of a monomer copolymerizable with these; The number average chain length (n) based on
It is in the range of 700 to 1000 Å, and the ratio of weight average chain length (w) to number average chain length w/n is 1.8
In the presence of 100 parts by weight of a rubbery polymer mainly composed of polybutadiene, which constitutes the backbone polymer for graft copolymerization, component C has a weight average particle size of 0.1 to 0.5μ. 55-90% by weight of aromatic vinyl monomer, 10-45% by weight of vinyl cyanide monomer, and 0-30% of monomer copolymerizable with these.
A graft copolymer obtained by graft copolymerizing 40 to 150 parts by weight of a monomer mixture consisting of the total amount of
Assuming 100 parts by weight, component A is 20 to 70 parts by weight, component B is 30 to 80 parts by weight, and the total amount of component A, component B, and component C is included in the composition as a whole. A thermoplastic resin composition characterized by a rubbery polymer content of 7 to 30% by weight has excellent heat resistance and impact resistance, and is far superior to conventional heat-resistant ABS resins in terms of moldability. The present invention was completed based on the discovery of excellent balance. The present invention will be specifically explained below. From the viewpoint of heat resistance, α-
Methylstyrene is an essential ingredient. Therefore, the amount of aromatic vinyl monomer that can be mixed with α-methylstyrene must be 20% by weight or less. If the amount of aromatic vinyl monomer exceeds 20% by weight, heat resistance will be impaired. Further, the aromatic vinyl monomer used here is not particularly limited, but preferably styrene, p
- A monomer selected from methylstyrene, p-tert-butylstyrene, chlorstyrene, etc., or a mixture of two or more monomers. α-methylstyrene or a monomer mixture of α-methylstyrene and the above monomer or monomer mixture is 50 to
It is appropriate to copolymerize within a range of 80 parts by weight. Outside this range, if it is less than 50 parts by weight, it will lead to a decrease in heat resistance, and if it exceeds 80 parts by weight, it will not only lead to a significant decrease in impact resistance, but also make copolymerization itself difficult. As vinyl cyanide monomers to be copolymerized with these, acrylonitrile, methacrylonitrile, etc. can be used alone or in combination in an amount of 15 to 35 parts by weight. If the vinyl cyanide monomer is used outside the above range, if it is less than 15 parts by weight, copolymerization will be difficult and a copolymer cannot be obtained in a satisfactory yield, and if it exceeds 35 parts by weight, the heat resistance will significantly deteriorate. This leads to deterioration of moldability and deterioration of formability. The object of the present invention can also be substantially achieved by a copolymer of a monomer or a monomer mixture containing α-methylstyrene as a main component and a vinyl cyanide monomer or a monomer mixture. However, monomers that can be copolymerized with these monomers may be added during copolymerization. Examples of these monomers include maleimide or maleimide derivatives such as maleimide, N-alkyl or arylmaleimide, and methacrylic acid esters such as methyl methacrylate and ethyl methacrylate. Among these, maleimide or maleimide derivatives are particularly effective when heat resistance is important. In addition, methacrylic acid esters are effective in improving the hue of molded products.
It is appropriate to use each of these monomers in an amount not exceeding 30 parts by weight. The reason for this is that, as mentioned above, the object of the present invention can be substantially achieved without using these monomers, and if the use of these monomers exceeds 30 parts by weight, One of the disadvantages is that the moldability is reduced, which is not suitable for the purpose of the present invention. In the present invention, a copolymer having α-methylstyrene as an essential component, that is, component A and component B
The average chain length and chain length distribution of the components and the blending ratio of the A component and the B component are important. Component A is a copolymer with a long chain length, that is, a substantially large molecular weight, and component B is a copolymer with a short chain length, that is, a substantially small molecular weight. In order to obtain a thermoplastic resin composition that has excellent heat resistance and impact resistance as well as good moldability, which is the objective of the present invention, first of all, the conditions are as follows:
As the A component, the number average chain length (n) based on polystyrene is in the range of 1200 to 1600 Å,
In addition, the ratio w/n of the weight average chain length (w) to the number average chain length must be in the range of 1.8 to 3.5, and the B component must also be the number average chain length (n) based on polystyrene. is 700~1000Å
and the ratio w/n of weight average chain length (w) to number average chain length must be in the range of 1.8 to 3.5. Furthermore, in the A component and the B component, the A component is 20 to 70 parts by weight, and the B component is 30 to 70 parts by weight.
The object of the present invention can only be achieved by blending in a proportion of 80 parts by weight. In general, copolymers containing α-methylstyrene as an essential component in the copolymer composition used in the present invention generally have long chain lengths and substantially high molecular weights, which are superior in terms of heat resistance and impact resistance. Those with a short chain length and substantially low molecular weight are inferior in terms of heat resistance and impact resistance, but are excellent in moldability.
Therefore, it was thought that if these were combined, the disadvantages of each would be improved, but the advantages would also be lost, and physical properties that were averaged would be obtained.
It was also true that it was outside the scope of the invention. By using copolymer components A and B within the scope of the present invention, it is surprisingly possible to improve moldability without reducing impact resistance. Further, within the scope of the present invention, there is little decrease in heat resistance. If a copolymer with a chain length outside the range of the present invention is used, moldability will be improved, but impact resistance and heat resistance will be reduced, resulting in loss of balance in physical properties. Also A
Even if the blending ratio of component B deviates from the range of the present invention, if the heat resistance and impact resistance are improved, the moldability may deteriorate, resulting in an extremely unbalanced physical property. Chain length distribution of a copolymer containing α-methylstyrene as an essential component such as component A or component B w/
It is rare for n to be less than 1.8 in polymerizations using conventional radical initiators. w/n
To obtain a copolymer with a molecular weight of less than 1.8, it is necessary to stop the polymerization at an early stage and distill off the remaining monomers, or else to perform fractionation based on molecular weight (for example, solvent fractionation). Such a method is not very practical from an economical and process point of view. w/
If n exceeds 3.5, it is unavoidable that component A contains a copolymer with a substantially high molecular weight and a long chain, resulting in a significant decrease in moldability. Component C is blended in the thermoplastic resin composition of the present invention in order to impart particularly high impact resistance.
Examples of the aromatic vinyl monomer in component C include styrene, α-methylstyrene, p-methylstyrene, p-tert-butylstyrene, chlorostyrene, etc. These may be used alone or in a mixture of two or more. Can be done. As vinyl cyanide monomers, acrylonitrile, methacrylonitrile, etc. are generally used. These monomers in component C form a branch polymer grafted onto the polybutadiene or butadiene copolymer described below, but in order to produce component C that substantially achieves the object of the present invention, , 55 to 90% by weight of an aromatic vinyl monomer and at least one vinyl cyanide monomer selected from the group of vinyl cyanide monomers based on 100 parts by weight of a rubbery polymer mainly composed of polybutadiene. Monomer mixture 40 consisting of 10 to 45% by weight and 0 to 30% by weight of monomers copolymerizable with these
It is sufficient to use ~150 parts by weight. If the composition of these monomers deviates from the above range, satisfactory moldability may not be obtained or heat resistance may deteriorate, making it impractical. In this way, a monomer copolymerizable with an aromatic vinyl monomer or a vinyl cyanide monomer can also be used in combination with the C component. Examples of these monomers include maleimide or maleimide derivatives such as maleimide, N-alkyl or arylmaleimide, and methacrylic acid esters such as methyl methacrylate and ethyl methacrylate. Among these, maleimide or maleimide derivatives are particularly effective when the heat resistance is to be observed. In addition, methacrylic acid esters are effective in improving the hue of molded products. Each of these monomers accounts for 30% by weight of the total amount of all monomers forming branched polymers in graft polymerization.
It is appropriate to use it within a range that does not exceed. The reason for this is that, as mentioned above, the purpose of the present invention can be substantially achieved without using these monomers, and that the use of these monomers makes up the total amount of all monomers. If it exceeds 30% by weight, there will be a drawback that moldability will be reduced, which will not meet the purpose of the present invention. For component C, it is appropriate to use a rubbery polymer containing polybutadiene as a main component that forms the backbone polymer and has a weight average particle size of 0.1 to 0.5 microns.
The rubber-like polymer containing polybutadiene as a main component herein refers to polybutadiene or a butadiene copolymer containing 50% by weight or more of polybutadiene. If the average particle size is outside the above range,
If the particle size is less than 0.1μ, sufficient impact strength cannot be obtained.
If it exceeds 0.5μ, silver-like marks are likely to occur during molding. Butadiene copolymers containing 50% by weight or more of polybutadiene include butadiene-styrene copolymers, butadiene-styrene copolymers,
Examples include methyl methacrylate copolymer and butadiene-acrylonitrile copolymer. Two or more of these copolymers and polybutadiene may be used as a mixture as long as the total butadiene content is not less than 50% by weight. Component C, which includes a rubbery polymer, is used by blending the above-mentioned A component and B component, but in that case, the amount of the rubbery polymer contained therein is calculated based on the total amount of A component, B component, and C component. It is essential that the amount is between 7 and 30% by weight. Outside this range, if the rubbery polymer content is less than 7% by weight, good impact resistance cannot be obtained, and if it exceeds 30% by weight, moldability is significantly reduced. The thermoplastic resin according to the present invention may be blended with an anti-aging agent, a lubricant, etc., if necessary. Further, it is permissible to mix and use other resins in addition to the A, B, and C components in the thermoplastic resin composition of the present invention as long as no compatibility problems such as layer peeling occur. Conventional methods may be used for compounding, but generally speaking, melting using an extruder,
It is best to knead. Acrylonitrile is a resin that can be blended with
Styrene copolymer, acrylonitrile-styrene methacrylate ester copolymer, acrylonitrile-α-methylstyrene copolymer, acrylonitrile-α-methylstyrene-methacrylate ester copolymer, acrylonitrile-p-methylstyrene copolymer, acrylonitrile -p-methylstyrene-methacrylic acid ester copolymer, acrylonitrile-styrene-α-methylstyrene copolymer, polycarbonate resin, etc., and these can be used alone or in combination of two or more. When blending other resins such as those mentioned above with the thermoplastic resin composition of the present invention, it is preferable that the amount of the other resin blended is 50% by weight or less based on the total amount of resin. The purpose of the present invention is to provide a thermoplastic resin composition with an excellent balance of heat resistance, impact resistance, and moldability. Taking advantage of conventional heat resistance
It goes without saying that it is suitable for use as a substitute for ABS resin, but it is especially suitable for use in the interior and exterior of automobiles, the exterior of motorcycles, and office equipment, and its industrial value is extremely high. It is. The present invention will be explained below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Furthermore, all parts and percentages in the examples are based on weight, and parts are parts by weight, and percentages are percentages by weight. Production of a copolymer containing α-methylstyrene as an essential component used in Examples 1 to 19 and Comparative Examples 1 to 34 Copolymer a containing α-methylstyrene as an essential component used in this example ~ x is Table 1 while blowing nitrogen gas into the 5 autoclave equipped with a stirrer.
The substances listed in the column of addition before initiation of polymerization were added.
After heating the autoclave and raising the temperature of the contents to 70°C, 0.1 part of potassium persulfate was added to initiate polymerization. The same amount of potassium persulfate was also added 6 hours later. Every 30 minutes after the start of polymerization, the remaining monomer is analyzed using gas chromatography to measure the polymerization rate (expressed on a weight basis relative to all monomers, the same applies hereinafter), and from the point when the polymerization rate exceeds 20%. Using a micro-metering pump, the entire amount of the substances listed in the sequential or continuous addition column of Table 1 was added to the polymerization system over 6 hours. After addition, add more potassium persulfate.
After adding 0.1 part and continuing the polymerization reaction for 4 hours, the polymerization was stopped. The polymerization rates at the time the polymerization was stopped were all 97% or higher except for copolymer m (copolymer m had a polymerization rate of 68% and no copolymer suitable for testing could be obtained). The polymer emulsion thus obtained was coagulated with magnesium chloride, washed, dehydrated, and dried to obtain a white powdery copolymer. Measurement of the average chain length of a copolymer containing α-methylstyrene as an essential component.
After making it into a 0.1% by weight tetrahydrofuran (THF) solution, it was analyzed by GPC. GPC is Toyo Soda Kogyo
HCL-802A manufactured by Co., Ltd., the column is also Toyo Soda Kogyo
Three GMH-6 manufactured by Co., Ltd. were used by connecting them in series. The obtained chromatogram is based on "Gel Permeation Chromatography" by Tsuguo Takeuchi and Sadao Mori, 81-85.
The number-average chain length (n) and weight-average chain length (w) were analyzed using the method described in Page and Maruzen (1976).
and chain length distribution (w/n). The determined n, w and w/n are shown in Table 2. The copolymers whose average chain lengths were measured were used as component A or component B according to Table 4. Production of graft copolymers used in Examples 1 to 19 and Comparative Examples 1 to 34 While blowing nitrogen gas into a 5 autoclave equipped with a stirrer, the substances listed in the column of addition before starting polymerization were charged, and while stirring. The temperature was raised to 50°C. When the internal temperature reached 50°C, sequential or continuous addition of the substances listed in the monomer mixture column of Table 3 was started, and the addition was completed after 5 hours. After the addition of the monomer mixture was completed, the internal temperature of the autoclave was raised to 70°C, and the polymerization reaction was continued for an additional 2 hours to complete the polymerization. The graft polymer emulsion thus obtained was coagulated with magnesium chloride, washed, dehydrated, and dried to obtain a white powdery graft polymer. Production of thermoplastic resin compositions of Examples 1 to 19 and Comparative Examples 1 to 34 Copolymers and graft copolymers containing α-methylstyrene as an essential component were prepared as component A according to Table 4.
B and C components are blended in the proportions shown in Table 4, and if necessary, other resins are blended in the proportions shown in Table 4, and further, for 100 parts of the rubber component in the thermoplastic resin composition, Add 1.2 parts of 2,6-di-t-butyl-4-methylphenol, mix thoroughly with a Henschel mixer, and melt with an extruder.
The mixture was kneaded into pellets. Sample pieces were prepared from the thermoplastic resin composition thus obtained by injection molding, and subjected to Vicat softening point and Izot impact strength tests. Further, the moldability of the pellet-shaped resin composition was evaluated by the spiral flow length in a spiral flow test. The measurement was based on the Vikat softening point and the Izot strength according to the JIS method described below. (1) Vikatsu Softening Point JIS K-6870 (2) Izot Impact Strength JIS K-6871 The spiral flow test was conducted under the following conditions. (a) Spiral shape: Alkyrmedean circle. The cross-sectional shape is shown in the drawing. (b) Molding machine: Kawaguchi Churchill 1040S manufactured by Kawaguchi Tekko Co., Ltd. (c) Injection pressure: 50KgG/cm ² (d) Cylinder temperature: 280°C (e) Mold temperature: 40°C As shown in Examples 1 to 19 All thermoplastic resin compositions within the scope of the claims of the present invention exhibit excellent heat resistance, impact resistance, and well-balanced good moldability. In comparison, all thermoplastic resin compositions outside the scope of the claims, such as Comparative Examples 1 to 33, have a poor balance in heat resistance, impact resistance, and moldability. Furthermore, as shown in Comparative Example 34, in a copolymer containing α-methylstyrene as an essential component, a satisfactory copolymer cannot be obtained and is not suitable for practical use if the copolymer composition is outside the scope of the claims. In Table 4, the evaluation of Izot impact strength, Vikatsu softening point, and spiral length in the 280° C. spiral flow test was as follows. Izotsu impact strength: 15Kg-cm/cm or more
Less than 15 kg-cm/cm was marked as x. Vikatsuto Softening Point: ○ above 122℃, × below 122℃
And so. 280℃ spiral flow length: 21cm or more, 21cm
Less than that was marked as ×.

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【table】 [Brief explanation of the drawing]

The figure shows the cross-sectional shape of the Archimedean circle used in the spiral flow test conducted to evaluate formability.

Claims (1)

[Scope of Claims] 1. A graft copolymer whose backbone polymer is component A and component B, which are copolymers mainly composed of α-methylstyrene shown below, and a rubbery polymer mainly composed of polybutadiene. It consists of C component, α
- In the case of a copolymer mainly composed of methylstyrene, the total amount of components A and B is 100 parts by weight,
Component A is 20 to 70 parts by weight, component B is 30 to 80 parts by weight, and the total amount of the rubbery polymer contained in the composition is 20 to 70 parts by weight. A thermoplastic resin composition characterized in that the amount is 7 to 30% by weight. Component A: 50 to 80 parts by weight of α-methylstyrene or a monomer mainly composed of α-methylstyrene, including 20% by weight or less of an aromatic vinyl monomer, and 15 to 35 parts by weight of vinyl cyanide monomer. , and α consisting of 0 to 30 parts by weight of a monomer copolymerizable with these
- A copolymer containing methylstyrene as an essential component, the number average chain length (n) based on polystyrene is in the range of 1200 to 1600 Å, and the weight average chain length (w) and the number average chain length The ratio w/n is in the range of 1.8 to 3.5. Component B: 50 to 80 parts by weight of α-methylstyrene or a monomer mainly composed of α-methylstyrene, including 20% by weight or less of an aromatic vinyl monomer, and 15 to 35 parts by weight of vinyl cyanide monomer. , and α consisting of 0 to 30 parts by weight of a monomer copolymerizable with these
- A copolymer containing methylstyrene as an essential component, the number average chain length (n) based on polystyrene is in the range of 700 to 1000 Å, and the weight average chain length (w) and the number average chain length The ratio w/n is in the range of 1.8 to 3.5. Component C: In the presence of 100 parts by weight of a rubbery polymer mainly composed of polybutadiene, which forms the backbone polymer of the graft polymer and has a weight average particle size of 0.1 to 0.5μ,
40-150 parts by weight of a monomer mixture consisting of 55-90% by weight of aromatic vinyl monomers, 10-45% by weight of vinyl cyanide monomers, and 0-30% by weight of monomers copolymerizable with these. A graft copolymer obtained by graft copolymerizing.