JPH0436171B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a new and useful method for producing heat-resistant and impact-resistant resins, and more particularly, the present invention relates to a new and useful method for producing heat-resistant and impact-resistant resins, and more particularly, the present invention relates to a method for producing heat-resistant and impact-resistant resins, and more particularly, styrene and methacrylic acid are synthesized as essential monomers in the presence of a latex-like rubbery polymer. An improved moldable thermoplastic styrene-methacrylic acid copolymer resin with excellent mechanical strength, particularly useful as various molding materials, which is obtained by graft copolymerization by a specific emulsion-suspension polymerization method. Regarding the manufacturing method. Styrene/methacrylic acid copolymer resin is a type of styrene resin, and is used as a molding material with extremely high heat resistance in a wide range of fields such as home appliance parts, automobile parts, OA equipment, and precision equipment. be. By the way, as a rubber-reinforced brand with even higher impact resistance, we have recently filed a patent application for impact-resistant styrene/methacrylic acid copolymer resin obtained by making full use of our unique polymerization technology. Application Nos. 58-213312 and 59-38358). The resins of these inventions have both heat resistance and impact resistance properties, and are also physically located between conventional general-purpose resins and engineering plastics, making them a promising candidate for the future in these fields. This is noteworthy even when predicted based on current demand trends. Therefore, it is used in fields where both high heat resistance and impact resistance are required, such as automobile related parts such as instrument panels, heater ducts or tail lamp housings, air conditioner ducts, breaker bars, etc. Home appliance parts such as TV cabinets, hair curlers or iron handles, OA related parts such as VTR tape cassettes, audio tape cassettes, floppy disk cases or OA equipment housings, optical equipment such as camera or projector housings or slide magazines. This will lead to further expansion of applications into various fields such as parts, food container parts such as microwave tableware, and insulation materials for construction. [Prior Art] In order to prepare impact-resistant styrene-methacrylic acid copolymer resin, which is a promising material, any of the bulk polymerization method, solution polymerization method, bulk-suspension polymerization method, or emulsion polymerization method can be used. However, in order to obtain a resin that has high heat resistance and impact resistance, as well as good appearance of molded products such as surface gloss, it is necessary to emulsion polymerize styrene and methacrylic acid in the presence of a rubbery polymer latex. Alternatively, it is necessary to use a polymer blend method consisting of the emulsion polymer thus obtained and a styrene/methacrylic acid copolymer resin. Therefore, when graft copolymerization is carried out at 40 to 100°C in an emulsified state using a latex-like rubber (rubber latex) as a rubbery polymer and a peroxide as an initiator, it is necessary to The emulsion system becomes unstable during such polymerization due to enlargement or destruction, and often results in agglomeration (cake-like formation). In order to overcome these difficulties in the prior art, the present inventors have developed a special method in which a portion of the methacrylic acid used is continuously added as the polymerization progresses, thereby preventing the agglomeration of the latex during the polymerization. In addition, in terms of physical properties, we have found that it is possible to obtain a product with superior impact strength compared to the batch addition method by making the copolymer composition uniform, and this has been applied to both of the above-mentioned applications. [Problems to be solved by the invention] However, as long as the above-mentioned special means are involved, when coagulating the graft copolymer latex and recovering the resin, the latex must be salted and filtered. To make it easier, a complicated process of granulation, then filtration, washing, dehydration, and drying is required, which requires a lot of labor and utility costs such as electricity. In addition, when a molding material is obtained by blending a powder with a low bulk density obtained by emulsion copolymerization and a bead-like or pellet-like styrene/methacrylic acid copolymer resin using an extruder, it requires capital investment. It requires special equipment to prevent bridging in the hopper, a screw structure to uniformly knead both resins, or expensive equipment such as a twin-screw extruder. It is often said that [Means for Solving the Problems] However, as a result of intensive studies to solve the above-mentioned problems in the emulsion polymerization method or the emulsion-blending method, the present inventors have developed the emulsion-suspension method as described below. In the polymerization method, it is possible to smoothly transition from an emulsified state to a suspended state, and the mechanical strength is significantly improved compared to conventional manufacturing methods while maintaining the inherent heat resistance and impact resistance. The present inventors have discovered that a resin capable of producing molded articles with excellent properties can be obtained, and have completed the present invention. That is, the present invention comprises a step of graft copolymerizing styrene and methacrylic acid in an emulsified state to a rubbery polymer latex, and a step of partially salting the graft copolymer latex obtained in this manner and then converting it into a suspended state. In the method for producing a heat-resistant and impact-resistant resin, which further comprises a step of completing graft copolymerization in this suspended state, a salt-breaking agent and a suspension stabilizer are first added, and then the monomer styrene and Either methacrylic acid is added simultaneously, or styrene is added and then methacrylic acid is added to transform the suspension into a suspension state, and the graft copolymerization is then completed in the suspension state in the presence of an initiator. Heat-resistant and
A method for producing an impact-resistant resin is provided. The method of the present invention will be explained in detail below. First, as a method for preparing this type of impact-resistant resin, recently, emulsion polymerization is first carried out, and then the obtained graft copolymer latex is suspended. The so-called emulsion-suspension polymerization method, in which the reaction is completed by suspension polymerization by converting the material into a turbid state, has become well-known. Regarding this manufacturing method, acrylonitrile/butadiene rubber/styrene copolymer resin (ABS resin), methyl methacrylate/butadiene rubber/
A large number of patent applications have been filed for styrene copolymer resins (MBS resins), etc., and methods suitable for each resin have been devised to transition from an emulsified state to a suspended state. However, in the case of styrene/methacrylic acid copolymer resin, when transferring from an emulsion system to a suspension system, the conventional technology is difficult because methacrylic acid as a monomer has a large effect on the aqueous dispersion state. As long as this is followed, the actual situation is that during a type of emulsification failure, which can be called partial salting, lumps and clumping (cake-like formation) occur, making it impossible to obtain a stable suspension state. That is, for example, in Japanese Patent Publication No. 43-21073, rubbery polymer Terrax (rubber latex), styrene and acrylonitrile are used,
Polymerization is started using a water-soluble polymerization initiator and an oil-soluble polymerization initiator in combination, and the reaction proceeds in an emulsion polymerization system in the early stage, and in the latter stage, the reaction is transferred to a suspension polymerization system in the presence of a suspension stabilizer. , to complete the reaction,
Although the preparation method of ABS resin has been disclosed,
Even if such a method is repeated using methacrylic acid instead of acrylonitrile, the viscosity increases during the polymerization and eventually coagulates, making it impossible to stir.This method makes it difficult to produce impact-resistant styrene-methacrylic acid copolymer resin. There was absolutely no way I could do that. In contrast, the present invention provides an improved emulsification-suspension method for producing impact-resistant styrene-methacrylic acid copolymer resins that have both high heat resistance and impact resistance, and also have excellent mechanical strength. The present invention provides a polymerization method that is characterized by (1) an emulsion polymerization step for grafting styrene and methacrylic acid onto a rubbery polymer latex; and (2)
The process consists of three major steps: a step in which the graft copolymer latex thus obtained is transferred to a suspended state through partial salting, and (3) a step in which the graft copolymerization is completed in this suspended state. In the step of transitioning from an emulsion system to a suspension system, that is, the step (2) described above, first a salting agent and a suspension stabilizer are added to cause partial salting, and then the monomers,
In other words, the basic method is to add styrene and methacrylic acid simultaneously or separately in the order of styrene and then methacrylic acid to bring the mixture into a completely suspended state. In the present invention, the term "partial salting" does not refer to a state in which the latex particles aggregate into a cream-like state, but rather a state in which the latex particles themselves have agglomerated but are still uniformly dispersed. I want it to be understood as a word that indicates. Moreover, in carrying out the method of the present invention, as mentioned above, in order to form a stable suspension system from an emulsion system, it is important to use a salt-breaking agent, a suspension stabilizer, and a unique combination of monomers. Only if the order of addition is followed can the original purpose of the invention be achieved. Here, since methacrylic acid, which is an essential monomer of the present invention, exhibits acidity in an aqueous solution, it has an aggregating effect on the terraces, and moreover, it is important to note that methacrylic acid, which is an essential monomer of the present invention, exhibits acidity in an aqueous solution. The timing of addition of methacrylic acid is a key point in reliably carrying out the emulsion-suspension polymerization method since it affects the viscosity of the liquid. In other words, the timing of adding methacrylic acid is as follows:
This is best done either after the styrene is added or at the same time as the styrene; if added before the styrene, the latex will agglomerate and cream the system, resulting in a suspended system. It will be difficult to move. Both monomers, styrene and methacrylic acid, can be added at once or continuously, but in order to obtain and maintain a stable aqueous dispersion state with low viscosity, It is preferable to use a continuous addition method. By doing so, the latex particles and these monomers do not cause aggregation and agglomeration (cake-like formation), and the generation of abnormal particles caused by aggregation of latex particles together. I am now able to suppress this. The suspension stabilizer may be added either before or after the addition of the salting agent, but preferably before the monomers styrene and methacrylic acid are added. If both of these monomers are added, it will be difficult to achieve a suspension state, and this may even lead to agglomeration (cake-like formation) during the process, so this method should be avoided. be. Incidentally, if necessary, the salting agent may be added after the suspension has been transferred to the suspension system. In this way, the timing of transition to a suspended state (suspension system) by adding a salting agent is determined during the step (1) above, that is, during the emulsion polymerization step (during emulsion polymerization), when the monomer mixture is polymerized. Any polymerization rate may be used as long as the polymerization rate is 50 to 100%, and a polymerization rate of 80 to 100% is suitable. If the polymerization rate is too low, transferring to a suspension system is not preferable because the final product will not have excellent physical properties. If this emulsion polymerization is not carried out at all, but the rubbery polymer latex is salted out, swelled and dissolved in the monomer mixture, and then the reaction is completed by suspension polymerization, the resulting molded product will be It was also found that it was too brittle to be put to practical use. In addition, as a result of measuring various physical properties of molded products of the impact-resistant styrene-methacrylic acid copolymer resin obtained by the improved emulsion-suspension polymerization method as in the method of the present invention, it was found that the Dupont It was also revealed that the impact strength was dramatically improved compared to that prepared by the emulsion-blending method. By the way, when using this emulsion-blending method, physical properties such as Izotsu impact strength, tensile strength, and bending strength were comparable, but Dupont impact strength is considered to be closer to the practical strength of actual molded products. However, high values could not be obtained. In general, rubber-modified copolymer resins are composed of a copolymer grafted onto a rubbery polymer and a free copolymer that does not participate in the grafting, and the composition of the rubber-modified copolymer resin is It is also known that the content of the rubbery polymer, its particle size, the grafting rate, the average molecular weight, and its distribution are important factors for developing the body impact properties of copolymer resins. There is. That is, for example, one of the important factors is how to suppress the aggregation of grafted rubbery polymers during the polymerization or extrusion process and uniformly disperse them into the resin phase. In many cases, small protrusions occur on the resin surface and the mechanical properties cannot be fully exhibited. Conventionally, in order to avoid or fundamentally eliminate this situation, there have been methods of combining a graft copolymer latex and a lubricant, or using a copolymer resin that has been separately emulsion copolymerized in the form of a latex and using this rubber-modified copolymerization method. There is a method of mixing it with resin and coagulating it into powder. On the other hand, it is probably because impact-resistant styrene-methacrylic acid copolymer resins with significantly improved Dupont impact strength can be easily obtained using the improved emulsion-suspension polymerization method such as the method of the present invention. This is because by gradually shifting from an emulsion system to a suspension system, uniform dispersion of the grafted rubbery polymer in the resin phase is achieved during the polymerization process, and this effect is not fully realized. This is thought to be because it is expressed. The impact-resistant styrene-methacrylic acid copolymer resin, which is the final product obtained by the method of the present invention, contains 3 to 40 parts by weight of the rubbery polymer and the total amount of both vinyl monomers, styrene and methacrylic acid, or the necessary amount. Then, the total amount with other vinyl monomers is 97
~60 parts by weight, and the breakdown of vinyl monomers is 97~70% by weight of styrene and 3% by weight of vinyl monomer.
~30% by weight of methacrylic acid, or if necessary, an additional 1 to 20% by weight of the styrene may be substituted with other vinyl monomers copolymerizable with the styrene, such copolymerizable. Typical vinyl monomers include α-methylstyrene, tert-butylstyrene, various halogen-substituted styrenes, vinyltoluene (meth)acrylonitrile, α-chloroacrylonitrile, and various (meth)acrylic acid esters. If the rubbery polymer is less than 3 parts by weight,
Since impact resistance becomes low, there is no practical value, and conversely, if it exceeds 40 parts by weight, fluidity and processability deteriorate, which is not preferable. Furthermore, the total amount of styrene and methacrylic acid added at the end of emulsion polymerization is suitably within the range of 50 to 300 parts by weight based on 100 parts by weight of the solid content of the grafted latex (graft copolymer latex). However, the composition is not particularly limited to this, and can be adjusted as appropriate as long as the composition of the final product is within the above range. The composition of the monomer mixture added during suspension polymerization does not need to be the same as that used during emulsion polymerization, and can be changed as appropriate depending on the required performance of the resin. Regarding the previous step in the method of the present invention, that is, the emulsion polymerization step, the above-mentioned patent applications, especially the patent application No.
As described in the specification of No. 58-213312, the initiator, chain transfer agent, antioxidant, etc. used in this case are not particularly limited, and known and commonly used ones can be used as they are. However, the type of surfactant (emulsifier) is important for the stability of the emulsion system, and various cypherate-type and sulfonate-type anionic surfactants are suitable for use in this case. The use of metal salts of higher fatty acids, which are commonly used in emulsion polymerization, is not preferred because it causes demulsification during polymerization. In addition, the method of adding methacrylic acid is to first add 1 to 70% by weight, preferably 1 to 50% by weight of the total amount of methacrylic acid used in emulsion polymerization as a reaction initiator.
Prepare the amount within the range, then the remaining amount,
In other words, an amount corresponding to 99 to 30% by weight, preferably 99 to 50% by weight of the total amount of methacrylic acid is continuously added as the polymerization progresses until the polymerization rate reaches 90%. Special methods are recommended. Further, as the suspension stabilizer (dispersant) used in carrying out the method of the present invention, ordinary organic dispersants can be used as they are. Particularly representative among them are partially saponified polyvinyl alcohol, partially saponified polymethyl methacrylate, polyacrylic acid or its salts, cellulose, methylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, polyalkylene oxide, polyvinylpyrrolidone, sulfonated Examples include polystyrene and alkylbenzene sulfonates, and these may be used alone or in combination of two or more. On the other hand, typical salt-folding agents for partial salt folding include sodium chloride, potassium chloride, sodium sulfate, magnesium sulfate, calcium chloride, and aluminum chloride. Any electrolyte that is commonly used can be used as is. Further, as the initiator for suspension polymerization, known and commonly used oil-soluble initiators can be used as they are, and lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, etc. are particularly representative. Furthermore, a chain transfer agent such as tertiary dodecyl mercaptan or α-methylstyrene dimer can be used to adjust the molecular weight of the resulting target resin. Furthermore, typical rubbery polymer latexes (rubber latexes) include polybutadiene, butadiene/styrene copolymer, butadiene/acrylonitrile copolymer, acrylic ester elastomer, or ethylene/propylene elastomer. Examples include various latexes. Thus, the heat-resistant and impact-resistant resins obtained by the method of the present invention contain compounds that can be dissolved in the monomer mixture during the preparation of such impact-resistant styrene-methacrylic acid copolymer resins, that is, during emulsion or suspension polymerization. It is also possible to add plasticizers, lubricants, stabilizers, ultraviolet absorbers, etc. that do not hinder the progress of polymerization. [Example] Next, the present invention will be explained in more detail with reference to Reference Examples, Examples, and Comparative Examples. In the following, all parts and percentages are based on weight unless otherwise specified. Reference Example 1 (Preparation example of styrene/methacrylic acid copolymer resin) 200 parts of distilled water was charged into the autoclave equipped with a stirring device in step 5, and 1 part of partially saponified polyvinyl alcohol as a suspension stabilizer and dodecylbenzenesulfone were added. Then, 85 parts of styrene, 15 parts of methacrylic acid, 0.2 parts of ditert-butyl peroxyhexahydroterephthalate, and 0.1 part of tert-butyl perbenzoate were added in sequence. Then, the temperature was raised to 90°C with stirring at a rotational speed of 400 rpm, maintained at the same temperature for 10 hours to perform suspension polymerization, and the reaction was continued at 120°C for another 3 hours. The methacrylic acid copolymer resin was washed, dehydrated, and then dried to obtain the desired resin. Reference Example 2 (Preparation Example of Graft Copolymer) In a reactor similar to Reference Example 1, the following was prepared. The following substances were prepared: Polybutadiene latex 87 parts (solid content = 57.4%) Styrene 40〃 Methacrylic acid 3〃 Potassium persulfate 0.3〃 Tertiary dodecyl mercaptan 0.1〃 Sodium dodecylbenzenesulfonate 2〃 Distilled water 200〃 Then , Nitrogen gas was introduced into the reactor, the temperature was raised to 70°C while stirring, and when the same temperature was reached, 7 parts of methacrylic acid was continuously added over 3 hours, and the temperature was further maintained at the same temperature for 2 hours. The reaction was completed by emulsion polymerization. A 10% aqueous solution of calcium chloride adjusted to 5% based on the solid content of the graft copolymer latex thus obtained was added, and the mixture was stirred for 90 to 90 minutes.
This latex was coagulated at 110° C., filtered, washed with water, dehydrated, and dried to obtain the desired powdery graft copolymer. Example 1 119 parts of the graft copolymer latex obtained in Reference Example 2 and 130 parts of distilled water were charged into a reactor and heated to 50°C. The latex was partially salted by adding 10 parts of a 10% aqueous calcium chloride solution and 2.5 parts of an 8% aqueous partially saponified polyvinyl alcohol solution under stirring at 300 rpm, followed by the addition of 55 parts of styrene. At this point the dispersion had transformed into a complete suspension. Thereafter, 10 parts of methacrylic acid was added, followed by 0.2 parts of tert-butyl peroxyhexahydroterephthalate, 0.1 part of tert-butyl perbenzoate, and 0.1 part of tertiary dodecyl mercaptan. After completing these preparations, this suspension was heated to 90°C, heated and polymerized at the same temperature for 5 hours, and the reaction was further continued at 120°C for 3 hours to obtain bead-shaped graft copolymer resin. However, it was then washed, dehydrated, and dried. Thereafter, 0.2 part of "Irganox 1076" (an antioxidant manufactured by Ciba Geigy, West Germany) was added to this copolymer resin, and the mixture was pelletized using an extruder at a cylinder temperature of 230°C. Next, the pellets were injection molded, and the physical properties of the molded products thus obtained were measured and are summarized in Table 1. Example 2 As a method of adding monomers, 55 parts of styrene and 10 parts of styrene were added.
A graft copolymer resin was obtained in the same manner as in Example 1, except that the mixture with 50% of methacrylic acid was added continuously over 1 hour. Example 3 136 parts of the graft copolymer latex obtained in Reference Example 2 and 120 parts of distilled water were charged into the same reactor as in Example 1, and the temperature was raised to 50°C. 350rpm
of 10% calcium chloride aqueous solution under stirring.
1 part and 2.5 parts of an 8% partially saponified polyvinyl alcohol aqueous solution to partially salt the latex,
Then 51 parts of styrene was added to transform it into a suspension. Thereafter, 9 parts of methacrylic acid were added, followed by 0.2 parts of tert-butyl peroxyhexahydroterephthalate, 0.1 parts of tert-butyl perbenzoate, and 0.1 parts of tert-dodecyl mercaptan. Next, heat polymerization was performed at 90°C for 5 hours, and further
The reaction was continued at 120° C. for 3 hours, and the graft copolymer resin thus obtained was treated in the same manner as in Example 1 to evaluate its physical properties. Example 4 Instead of 51 parts of styrene, 41 parts of styrene and 10
The desired graft copolymer resin was obtained in the same manner as in Example 3, except that methyl methacrylate was used. Comparative Example 1 This example is about a preparation example using the emulsification-blending method. First, 40 parts of the powdered graft copolymer resin obtained in Reference Example 2 and the bead-shaped particles obtained in Reference Example 1 were added. 60 parts of styrene/methacrylic acid copolymer resin and 0.2 parts of "Irganox 1076" were mixed and pelletized using an extruder with a cylinder temperature of 260°C. The pellets were then injection molded, and the physical properties of the molded articles thus obtained were measured, as shown in Table 1. Comparative Example 2 This example is also about a preparation example using the emulsion-blending method, but 35 parts of the powdered graft copolymer resin of Reference Example 2 and 65 parts of the beaded styrene-methacrylic acid copolymer resin of Reference Example 1 were added. Table 1 shows the results of pelletizing in the same manner as in Comparative Example 1, then injection molding, and measuring the physical properties, except that the ratio was changed to 50%. Table 1 shows the physical properties of the molded products obtained in each of the above Examples and Comparative Examples.
Of these, Izotsu impact strength is ASTM D-256.
The tensile drop point strength and bending strength are based on ASTM D-638 and D-790, respectively, and the heat distortion temperature is based on ASTM D-648 with a maximum fiber stress of 18.6 kg/ ^cm2 . . In addition, the Dupont impact strength was measured using a Dupont impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd. under the conditions that the diameter of the striking tip tip is 1/2 inch, the diameter of the striking pin cradle is 1/2 inch, and the thickness is 4.0 mm. A 500g weight was dropped onto a molded product from an arbitrary height, and the height at which cracks appeared in the molded product was measured.

〔Effect of the invention〕

As mentioned above, the object of the present invention is to provide a method for producing impact-resistant styrene/methacrylic acid copolymer resin by emulsion-suspension polymerization, and the advantages of following the method of the present invention are as follows. In summary, a copolymer resin with extremely superior mechanical strength can be obtained compared to conventional methods, and since the polymerization process is finally completed in the form of suspension polymerization, the resin produced is extremely easy to filter. It is possible to obtain beads with high properties, so there is no need for the salt-folding step that is seen in ordinary emulsion polymerization methods, and the subsequent workability of washing, dehydration, and drying is also excellent. Can be mentioned. As a result, it is understandable that economic efficiency is significantly improved.

Claims (1)

[Claims] 1. A step of graft copolymerizing styrene and methacrylic acid to a rubbery polymer latex in an emulsified state, and then partially salting the thus obtained graft copolymer latex, and then converting it into a suspended state. A heat-resistant and
In the method for producing impact-resistant resins, a salt-breaking agent and a suspension stabilizer are first added, and then the monomers styrene and methacrylic acid are added simultaneously, or styrene is added and then methacrylic acid is added. Production of a heat-resistant and impact-resistant resin with excellent mechanical strength, characterized by adding an acid to convert it into a suspended state, and then completing graft copolymerization in this suspended state in the presence of an initiator. Method. 2 A moldable thermoplastic resin obtained by copolymerizing the heat-resistant and impact-resistant resin described above with 3 to 40 parts by weight of a rubbery polymer and a total amount of 97 to 60 parts by weight of styrene and methacrylic acid. Moreover, the percentage of styrene and methacrylic acid mentioned above is 97~
Claim 1, characterized in that it is 70% by weight of styrene and 3-30% by weight of methacrylic acid.
The manufacturing method described in section. 3 The monomeric styrene described above is 1 of the styrene.
20% by weight of other vinyl monomers copolymerizable with the styrene. manufacturing method.