JPS635412B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing thermoplastic resins. More specifically, a monomer mixture containing a vinyl aromatic compound monomer and a vinyl cyanide compound monomer as essential components is graft-polymerized onto a rubbery polymer latex using a specific method to make it soft and flexible. It is an object of the present invention to provide a method for producing a resin material that has high properties, has excellent secondary processability such as painting and plating, and can be injection molded. Radical polymerization of a mixture of a vinyl aromatic compound monomer such as styrene and a vinyl cyanide compound monomer such as acrylonitrile, or a mixture of these and a (meth)acrylic acid ester monomer such as methyl methacrylate to a rubbery polymer. It is known to produce impact-resistant thermoplastics by graft polymerization in the presence of initiators. A typical method of such a method is to add the above-mentioned monomer mixture, a radical polymerization initiator, and, if necessary, a suitable chain transfer agent to a rubbery polymer latex, and then convert the monomer mixture by emulsion polymerization. This method involves graft polymerization onto a rubbery polymer. The so-called ABS resin manufactured by this method has excellent impact resistance, is easy to mold, has high rigidity, and has a high surface hardness. It also has excellent surface gloss and is not susceptible to secondary processing such as painting and plating. Since it is easy to obtain molded products with a beautiful appearance, it is widely used in the fields of interior and exterior parts of automobiles, electrical products, and household goods. However, such thermoplastic resins have too high rigidity and surface hardness for certain applications, resulting in a hard feel, which has been an impediment to their use. Such applications include, for example, parts that require soft materials from the viewpoint of safety when coming into contact with the human body. In addition, decorative items made from these thermoplastic resins may be attached or fitted onto curved surfaces, and if they are highly rigid, they must be pre-molded into a shape that matches each curved surface. become. If this decorative item is soft and flexible, it can be molded to fit surfaces with various different curvatures, eliminating the need for many different molds. There are advantages. Such impact resistant thermoplastic resin (ABS resin)
There are several possible ways to reduce the hardness of One method is to increase the content of rubbery polymer in the resin. Although this method can reduce the hardness of the resin to a considerable extent, since the rubbery polymer has unsaturated bonds, increasing the content will impair the stability against heat during molding, making molding difficult. It has the disadvantage of being difficult. Another method for reducing the hardness of the resin is to adjust the combination of monomers used during graft polymerization so as to provide a polymer close to a rubber-like polymer. However, if this method is used to lower the hardness of the resin, it will inevitably result in a large drop in the glass transition temperature, resulting in poor heat deformation resistance, which will not only severely limit the use of the resin, but also cause problems in its production. After drying, heat during drying causes fusion, making it impossible to stably produce powder. In this way, attempting to reduce the hardness of ABS resin by the above-mentioned method has disadvantages during processing and production, so there has been a strong demand for the development of a soft resin that can be used for the above-mentioned purposes and can be stably produced. The inventors of the present invention have conducted intensive studies on a method for reducing the hardness of ABS resin without causing the above-mentioned problems and while maintaining the excellent secondary processability of ABS resin. Surprisingly, by carrying out the graft polymerization reaction under specific conditions using a specific combination of radical polymerization initiators, the hardness of the resulting resin can be increased without adversely affecting other properties. It was discovered that this significantly decreased, and the present invention was achieved based on this finding. That is, the present invention applies to rubbery polymer latex.
(A) at least one vinyl aromatic compound monomer;
(B) A mixture of at least one vinyl cyanide compound monomer and optionally (C) at least one (meth)acrylic acid ester monomer is graft-polymerized in the presence of a radical polymerization initiator. In producing a thermoplastic resin, (i) a rubbery polymer latex in which the weight fraction of particles with a particle size of 0.3 μ or more is at least 50% is used; (ii) a rubbery polymer in the latex is used; Solid content and above
The ratio of the total amount of monomers consisting of (A), (B), and (C) was adjusted to be 15:85 to 35:65 by weight, and (iii) organic hydroperoxide and water-soluble (iv) continuously adding the entire amount of the monomer and the organic hydroperoxide component of the radical polymerization initiator, or both components, to the reaction system; ) The grafting rate in the produced thermoplastic resin is 140
% or more, and (vi) Rockwell hardness (R scale) is 70 or less. According to the method of the present invention, the hardness of the resin can be lowered to a level that shows sufficient flexibility, for example, 70 or less on the Rockwell hardness (R scale), and the thermal stability during molding can be reduced. Powder obtained by coagulating the latex after graft polymerization by a known method does not cause fusion during drying and can be stably produced as a powder. Furthermore, the resin thus obtained can be made into various products by injection molding, and these can be painted, plated, etc. by methods conventionally used for this type of resin. Next, the constituent elements of the present invention will be explained in detail. One of the essential conditions in the method of the present invention is that the rubbery polymer latex used for graft polymerization has a particle size.
The key point is to use latex containing large particles of 0.3μ or more. The content of particles with a particle size of 0.3μ or more must be at least 50% by weight, and if this content is 50%
% or less, the hardness of the resin hardly decreases even if the graft polymerization is carried out under the above-mentioned specific conditions. In order to obtain a resin as soft as possible, the rubbery polymer latex preferably has a weight fraction of particles with a particle size of 0.5 μm or more of 50% or more. The particle size distribution of rubbery polymer latex is determined by a known method.
For example, it is measured by a method using sodium alginate or a Coulter counter. In order to produce a rubbery polymer latex with such characteristics, methods that are known in the art can be used, such as applying mechanical shearing force to small-sized latex to agglomerate the particles, or changing temperature. A method of agglomerating particles by (quenching) can be adopted. However, in order to satisfy the above characteristics, it is necessary to adjust the polymerization conditions, such as the polymerization temperature, polymerization time, or amount of chain transfer agent. It is also possible to use a mixture of two or more latexes having different particle size distributions so that the resulting mixed latex satisfies the above conditions. Examples of the rubbery polymer latex used include polybutadiene and butadiene copolymer latex containing 50% by weight or more of butadiene. Monomers that can be used to copolymerize with butadiene include vinyl aromatic compounds such as styrene, vinyl cyanide compounds such as acrylonitrile, and methyl, ethyl, and acrylic acids and methacrylates.
Acrylic ester compounds such as propyl and n-butyl esters. As a rubbery polymer,
Preference is given to (co)polymers of 100 to 80% by weight of butadiene and 0 to 20% by weight of styrene or acrylonitrile. The second essential requirement in the method of the present invention is the amount of monomers [above (A), (B) and optionally (C)] used in graft polymerization and the rubbery polymer (solid content).
The weight ratio should be in the range of 85:15 to 65:35. Outside this range, even if graft polymerization is carried out using the latex specified above, a resin with low hardness cannot be obtained. Moreover, if the amount of the rubbery polymer increases, the thermal stability will deteriorate as described above, which is not preferable. The vinyl aromatic compound monomer (A) used for graft polymerization is radically polymerizable, such as styrene, α-methylstyrene, vinyltoluene, m-chlorostyrene, p-chlorostyrene, vinylnaphthalene. , acenaphthylene, etc. Particularly preferred monomers are styrene,
These are α-methylstyrene, vinyltoluene, m-chlorostyrene, and p-chlorostyrene. Examples of the vinyl cyanide compound monomer (B) include acrylonitrile and methacrylonitrile. In some cases, (meth)acrylic acid ester monomer (C) can be used in combination with these monomers.
Examples include methyl, ethyl, propyl, n-butyl, and phenyl esters of acrylic acid and methacrylic acid. As monomers, a combination of styrene and acrylonitrile is particularly preferred. There are no particular restrictions on the ratio of these monomers used, but the weight ratio of monomer (A) to monomer (B) is usually 50:50.
~90:10 range, preferably 60:40-80:
The range is 20. Furthermore, when using monomer (c), the proportion of monomer (C) used is usually 25 parts by weight or less per 100 parts by weight of monomer (A) and monomer (B). be. The third essential requirement is the use of a redox initiator consisting of an organic hydroperoxide and a water-soluble iron salt as a radical polymerization initiator during graft polymerization. Specific examples of organic hydroperoxides include cumene hydroperoxide, menthane hydroperoxide, p-diisopropylbenzene hydroperoxide, and t-butyl hydroperoxide. Examples of water-soluble iron salts include sugar-containing pyrophosphate formulations and sulfoxylate formulations. When other initiators commonly used in this type of polymerization are used, such as persulfates, azobisisobutyronitrile, or peroxides alone such as benzoyl peroxide, little decrease in resin hardness is observed. I can't. In the method of the present invention, the monomers (A) to (C) and the above radical polymerization initiator are added to the rubbery polymer latex, and the graft polymerization reaction is carried out by emulsion polymerization. Fourth and fifth, at this time, the total amount of the monomer and the organic hydroperoxide component of the radical polymerization initiator, or both components, are continuously added to the reaction system to increase the grafting rate in the produced thermoplastic resin. The goal is to make it 140% or more. If part or all of the monomer or radical polymerization initiator is added to the reaction system at once, or if the grafting rate is not sufficiently increased, the resin with low hardness, which is the object of the present invention, cannot be obtained. Appropriate. The amount of organic hydroperoxide used in polymerization is 1 part by weight or less, especially 0.2 to 0.6 parts by weight, per 100 parts by weight of the total amount of monomers.
When using FeSO ₄ .7H ₂ O, a resin with good quality balance can be obtained at 0.0005 to 0.01 part by weight. In order to achieve the above-mentioned high grafting rate and obtain a resin with low hardness and excellent secondary processability, which is the objective of the present invention, monomers and radical polymerization initiators are continuously added for 2 hours or more. It is preferable to add it over a period of time, and it is particularly preferable to add it over a period of 4 hours or more. The temperature of the polymerization reaction is 80°C or less, particularly about 50 to 70°C, which gives good quality and polymerization efficiency. The emulsifier used in emulsion graft polymerization is
Any emulsifier that is commonly used in the emulsion polymerization of vinyl monomers can be used without particular restrictions, and usually alkali metal salts of fatty acids, alkali metal salts of aliphatic sulfuric esters, or alkali metal salts of disproportionated rosin acids. etc. are used. If necessary, when performing graft polymerization, n-octyl mercaptan,
It is possible to improve the fluidity of the resin during molding by adding a small amount of a chain transfer agent such as mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, and mercaptoethanol, various terpenes, or halogen compounds. However, addition of a large amount is unsuitable because it lowers the grafting rate and increases the hardness of the resin. The amount of chain transfer agent added is usually 0.5 parts per 100 parts by weight of the total amount of monomers.
Parts by weight or less are sufficient. The thermoplastic resin obtained by the method of the present invention can be put to practical use alone as it is, or can be used with other thermoplastic resins, for example, as long as it does not increase the hardness of the final product.
Can be used in combination with AS resin. In this case as well, it is preferable that the weight fraction of the rubbery polymer in the resin composition finally obtained is 15% or more. The thermoplastic resin obtained by the method of the present invention is recovered from the graft polymerization latex by a known method, and is obtained, for example, in powder form. These thermoplastic resins (or compositions) are further mixed with appropriate amounts of anti-aging agents such as hindered phenols, lubricants such as fatty acid metal salts, and various other additives commonly used in this type of polymer. It is also possible. The thermoplastic resin thus obtained has lower hardness and greater flexibility than ordinary resins of this type, and is therefore suitable for use in the fields of application mentioned at the beginning. They also have sufficient thermal stability even in injection molding at temperatures around 250°C, giving molded products with excellent appearance, and secondary processing such as painting and plating is not possible with ordinary resins of this type. It can be done very easily using the following method. Furthermore, the thermoplastic resin powder obtained by the method of the present invention retains powder properties under normal drying conditions, and stable continuous production is possible. Thus, the industrial utility value of the present invention is extremely large. The present invention will be explained in more detail below using Examples, but the scope of the present invention is not limited by these Examples unless the gist of the invention is exceeded. In each example below, the number of copies and percentage
All values represent parts and percentages by weight. Example 1 First, rubbery polymer latex A (hereinafter referred to as latex A) was prepared by the following method. That is, butadiene was emulsion polymerized using fatty acid soap as an emulsifier, a redox initiator consisting of cumene hydroperoxide, ferrous sulfate, and formaldehyde sulfoxylate as an initiator, and t-dodecyl mercaptan as a chain transfer agent. A polybutadiene latex with enlarged latex particles was prepared by forcing stirring during the polymerization. The total polymerization time was 38 hours, and the conversion rate was 63%. The obtained latex A had a solid content of 34%, and the particle size distribution measured by the sodium alginate method was as follows. Particle size range Weight fraction (%) 0.3μ or less 26 0.3μ to 0.5μ 11 0.5μ or more 63 Graft polymerization reaction was then carried out by the following method. Internal volume with stirring device, heating jacket, reflux condenser, thermometer, nitrogen gas inlet, and continuous addition device for monomers and polymerization initiator.
Fourteen stainless steel reactors were charged with the following reagents. Latex A (as solid content) 700 parts Disproportionated rosin acid potassium salt 10.5 parts Potassium hydroxide 0.4 parts Water (including water in the latex) 2700 parts After replacing the atmosphere in the reactor with nitrogen gas,
Heated it with a jacket. When the internal temperature of the reactor reached 70°C, a solution of 7.2 parts of sodium pyrophosphate, 9 parts of glucose, and 0.15 parts of ferrous sulfate in 300 parts of water was added. While stirring the mixture, the temperature of the jacket was maintained at 70°C, and the following emulsified mixture was added continuously at a constant rate over 8 hours. Styrene 1510 parts Acrylonitrile 790 parts t-dodecyl mercaptan 9 parts Cumene hydroperoxide 12 parts Disproportionated potassium rosin acid salt 42 parts Potassium hydroxide 1.6 parts Water 3000 parts After the addition, the reaction was continued with stirring for an additional hour. The conversion rate after the reaction was 87%. 2,6-T is added to the obtained polymer latex as an anti-aging agent.
- After adding 30 parts of butyl para-cresol (BHT), the latex was coagulated with sulfuric acid and washed with water to obtain a powdered polymer. This product was then dried overnight in a hot air dryer at 80°C, but there was no fusion phenomenon of the polymer powder, and the powder remained smooth even after drying. Approximately 1 g of polymer powder was accurately weighed, placed in a 50 ml Erlenmeyer flask, 25 ml of acetone was added, and the mixture was left overnight.
Next, the suspension was centrifuged at 23,000 rpm for 60 minutes to separate the acetone soluble and insoluble components. The acetone-insoluble matter was vacuum dried and the weight was measured. The grafting rate was calculated according to the following formula. Grafting rate = (acetone insoluble content - rubber content in the prepared ABS)/rubber content in the prepared ABS x 100 (%) The grafting rate was 162%. Next, 18 parts of ethylene bis stearylamide and 9 parts of calcium stearate were added to 2000 parts of this polymer powder, mixed in a Henschel mixer, and
The pellets were pelletized at 200°C using a mm extruder, and test pieces were prepared using the method described below to measure their physical properties. Even during pelletization and injection molding of test pieces, there were no troubles due to rubber deterioration, and the work could be carried out stably. Fluidity during processing was measured at 200°C using a Koka type flow tester. Izotsu impact strength is 5
A specified test piece was molded at 200℃ using an ounce injection molding machine, and according to the method of ASTM D256.
Measurements were taken at 23°C and 0°C. Rockwell hardness (hereinafter abbreviated as RH) was measured according to the method of ASTM D785 using the same test piece as the Izod impact strength. The gloss level is determined by ASTM after molding the specified test piece at 200℃ using a 5-ounce injection molding machine.
Measured according to D523. Table 1 shows the measurement results of these physical properties. Furthermore, the above test piece for gloss measurement was coated with an acrylic paint and thinner, and as a result, it had good paintability. Example 2 In this example, the following latex B was prepared and used as a rubbery polymer latex together with the above-mentioned latex A. Latex B was prepared by continuing the polymerization in the method for preparing latex A in Example 1 without performing forced stirring during the polymerization. Polymerization time is 38 hours, conversion rate is 71%, solid content is 38%
The particle size distribution measured by the sodium alginate method was as follows. Particle size range Weight fraction % 0.3 μ or less 89 0.3 μ to 0.5 μ 8 0.5 μ or more 3 The experiment of Example 1 was carried out using a mixture of 500 parts of Latex A and 200 parts of Latex B instead of 700 parts of Latex A of Example 1. repeated. I was able to work without problems when drying the polymer and molding test pieces. Table 1 shows the physical property measurement results. A coating test was also conducted in the same manner as in Example 1, and good coating properties were shown. Example 3 In this example, the experiment of Example 1 was repeated using the following latex C instead of latex A. Table 1 shows the physical property measurement results. Moreover, the obtained resin had good paintability. Latex C is latex A in Example 1.
butadiene instead of butadiene in the preparation method of
It was prepared using a mixture of 85% styrene and 15% styrene. Polymerization time of this product is 40 hours, conversion rate
64%, and the solid content was 35%, and the particle size distribution measured by the sodium alginate method was as follows. Particle size range Weight fraction % 0.3 μ or less 30 0.3 μ to 0.5 μ 18 0.5 μ or more 52 Example 4 In the experiment of Example 1, the composition of the emulsified mixture to be added continuously was as follows, and this was added over a period of 4 hours. The experiment was conducted in exactly the same manner as in Example 1, except that the mixture was added across the board. Styrene 1510 parts Acrylonitrile 790 parts t-dodecyl mercaptan 3 parts Cumene hydroperoxide 12 parts Disproportionated rosin acid potassium salt 42 parts Potassium hydroxide 1.6 parts Water 3000 parts The physical property measurement results are shown in Table 1. Furthermore, the workability and paintability during drying and molding of the resin powder were also good. Example 5 In the experiment of Example 1, the amount of latex A initially charged into the reactor was 900 parts solids, and the amounts of styrene, acrylonitrile, and t-dodecyl mercaptan in the emulsified mixture that were continuously added were each 1380 parts. Experiments were conducted using 1 part, 720 parts, and 5 parts. The results are shown in Table 1. Comparative Example 1 The experiment of Example 1 was repeated using 700 parts of Latex B in place of Latex A. The results are shown in Table 1. A comparison with the results of Example 1 shows that when the content of particles with a particle size of 0.3 μm or more in the rubbery polymer latex is small, a resin with low hardness, which is the object of the present invention, cannot be obtained. Comparative Example 2 The experiment of Example 1 without the addition of an aqueous solution of sodium pyrophosphate, glucose and ferrous sulfate, and using 15 parts of potassium persulfate instead of cumene hydroperoxide in the emulsified mixture that was added continuously. repeated. The results are shown in Table 1. It can be seen that if a redox polymerization initiator is not used, a resin with low hardness, which is the object of the present invention, cannot be obtained. Comparative Example 3 In the experiment of Example 1, half of the emulsified mixture that was to be added continuously was added at once and reacted for 1 hour, and then the remaining half was added continuously over 4 hours and the experiment was carried out. I did it. As shown in Table 1, it is clear that a resin with low hardness cannot be obtained by such a method. Comparative Example 4 In the experiment of Example 1, the amount of latex A initially charged into the reactor was 1500 parts solids, and the composition of the emulsified mixture to be continuously added was as follows. Styrene 980 parts Acrylonitrile 520 parts Cumene hydroperoxide 10 parts Disproportionated rosin acid potassium salt 30 parts Potassium hydroxide 1.2 parts Water 2000 parts Test pieces for measuring physical properties will be molded from the obtained polymer in the same manner as in Example 1. However, the thermal stability during molding was poor, and a satisfactory test piece could not be molded. Next, when pelletizing the above polymer, a commercially available styrene-acrylonitrile copolymer (SAN manufactured by Mitsubishi Monsanto Chemical Co., Ltd.) was added to 2000 parts of the polymer.
2,000 parts of C) were added to form pellets, and the physical properties of the pellets were measured in the same manner as in Example 1, but a resin with low hardness, which is the object of the present invention, could not be obtained. The results are shown in Table 1. Comparative Example 5 An experiment was conducted in exactly the same manner as in Example 1, except that the composition of the emulsified mixture that was continuously added in the experiment of Example 1 was as follows, and the emulsified mixture was added over a period of 4 hours. Styrene 1510 parts Acrylonitrile 790 parts t-dodecyl mercaptan 7 parts Cumene hydroperoxide 12 parts Disproportionated rosin acid potassium salt 42 parts Potassium hydroxide 1.6 parts Water 3000 parts The physical property measurement results are shown in Table 1. The grafting ratio of the thermoplastic resin obtained by this method was 115%, which in this case was insufficient to obtain the desired resin with low hardness. 【table】

Claims (1)

[Scope of Claims] 1. A rubbery polymer latex containing (A) at least one vinyl aromatic compound monomer, (B) at least one vinyl cyanide compound monomer, and optionally
(C) In producing a thermoplastic resin by graft polymerizing a mixture containing at least one type of (meth)acrylic acid ester monomer in the presence of a radical polymerization initiator, (i) as a rubbery polymer latex; , using a latex in which the weight fraction of particles with a particle size of 0.3 μ or more is at least 50%;
The ratio of the total amount of monomers consisting of (A), (B), and (C) is adjusted to be 15:85 to 35:65 by weight, and (iii) organic hydroperoxide is used as a radical polymerization initiator. (iv) continuously adding the entire amount of the monomer and the organic hydroperoxide component of the radical polymerization initiator, or both components, to the reaction system; (v) Grafting ratio in the generated thermoplastic resin is 140
% or more, and (vi) a Rockwell hardness of 70 or less.