JPS6245246B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a thermoplastic resin with excellent impact resistance. ABS resin, which is generally represented as an impact-resistant resin, mainly contains polybutadiene or styrene-butadiene rubber (SBR), styrene, and acrylonitrile. The industrially carried out methods can be categorized based on the polymerization method, and are broadly divided into emulsion polymerization method, bulk polymerization method, suspension polymerization method, solution polymerization method, bulk suspension two-stage polymerization method, and emulsion bulk polymerization method. . However, the above-mentioned polymerization methods are far from satisfactory in all respects.For example, although emulsion polymerization is excellent in polymerization reaction control and production stability, the amount of water used in the coagulation process, washing process, drying process, etc.
The amount of electricity consumed is large, and it is extremely difficult to remove impurities such as salts or acids that are essential in the coagulation process.
It is also a major cause of color banding during thermoforming. In the bulk polymerization method, the rubber elastomer component must be dissolved in the monomer, so it is not only possible to use soluble rubber, but also the rubber content is limited due to the thickening phenomenon of the polymerization system. Therefore, it is not easy to control the reaction of partial heat generation. Even the suspension polymerization method has problems with dissolution of the rubber elastomer into the monomer, problems with the morphology of the product, and further problems with uneven dispersion of the product in the rubber. Further, in the solution polymerization method, reaction operation and reaction control are easy, but a large amount of utility is required for solvent recovery. The two-stage bulk suspension polymerization method has the same problems as the bulk polymerization method in that it requires high viscosity operations during the elastomer dissolution step and the polymerization step. In the emulsion bulk polymerization method, a graft copolymer is produced by emulsion polymerizing styrene and acrylonitrile onto a butadiene-based elastomer that is once produced, and monomers are extracted from this graft copolymer to perform bulk polymerization. Similarly, in addition to the problem of reaction control due to partial heat generation, when the rubber content becomes large, rubber deterioration due to partial heat generation cannot be avoided, which requires painstaking efforts to make the polymerization process continuous and to design the polymerization production equipment. Furthermore, it becomes difficult to switch types in terms of production. In the emulsion suspension polymerization method, styrene and acrylonitrile are emulsion polymerized to a butadiene-based elastomer once produced to produce a graft copolymer.
In order to perform suspension polymerization by adding a partial coagulant, suspension polymerization stabilizer, and monomer to this graft copolymer emulsion latex and recovering it in the form of beads, polymerization reaction control and production stability are difficult to maintain. It is as good as emulsion polymerization, and since no coagulation or washing steps are required, the amount of utility used is small, and the stability of molding is improved because there is less contamination of impurities. However, the current emulsion suspension polymerization method still has serious problems that need to be improved, and has not yet been put into practical use industrially. That is, due to problems caused by the stability of the polymerization system, coarse granules may be formed or a cake-like phenomenon may occur. Furthermore, problems caused by agglomeration of the rubber in the product may result in poor molding processability or lack of smoothness in appearance during molding. Furthermore, problems due to the design of the polymer structure may prevent satisfactory impact resistance from being achieved. At present, no method has been found that simultaneously solves these problems, and it will be difficult to industrially implement emulsion suspension polymerization without improving these points. In view of the current situation, the present inventors completed the present invention as a result of intensive research to improve the conventional method for producing impact-resistant resins. The present invention involves adding an ethylenic monomer or monomer mixture (B) to a rubbery polymer (A) latex and carrying out emulsion polymerization to produce a graft copolymer (C) latex, and then producing a graft copolymer (C) latex. After adding an acidic substance or an electrolyte substance to the coalescing (C) latex to cause partial coagulation, first adding an ethylenic monomer or monomer mixture (D) and then adding a suspension polymerization stabilizer, or Adding the ethylenic monomer or monomer mixture (D) and the suspension polymerization stabilizer at the same time,
In a method comprising suspension polymerization to obtain a graft copolymer (E) in the form of beads, (1) the rubbery polymer (A) contains at least 60% by weight of a diene monomer component, and has a degree of swelling. 10 to 35, gel content of 70% or more, weight average particle size of 0.2 to 0.4μ, with the majority of particles within the range of 0.03 to 0.5μ.(2) Ethylene monomers of (B) and (D) Or each monomer mixture contains 50 to 100 aromatic vinyl monomers.
Weight% and vinyl monomer copolymerizable with it: 50~
0% by weight (3) Graft copolymer (C) has a free polymer content of 20%
Above, the reduced viscosity of the acetone soluble component (ηsp/
C) is 0.30 to 1.0 dl/g. In the present invention, swelling degree and gel content are defined as follows. That is, ₀ g of rubbery polymer (A)W was immersed in approximately 50 times the amount of toluene at 30°C for 48 hours, and the weight of the swollen sample was calculated.
When W ₁ g and the swollen sample W ₁ g are vacuum-dried to a constant weight, and the weight after drying is W ₂ g, degree of swelling = W ₁ - W ₀ /W ₀ Gel content = W ₂ /W ₀ × 100 (%) Furthermore, the free polymer rate and the acetone soluble content ηsp/C are defined as follows. In other words, the polymer that is not grafted onto the rubbery polymer (A) from the graft copolymer (C) (hereinafter referred to as free polymer) is extracted and separated using acetone, and its weight is measured. Weight of polymer/weight of rubbery polymer (A) x 100 (%) ηsp/C of the acetone soluble portion is obtained by dissolving 0.1 g of the polymer extracted and separated with this acetone in 100 ml of N·N-dimethylformamide. Measured with an Ostwald viscometer at 25°C. The method of the present invention uses all kinds of diene rubbers such as natural rubber, butadiene rubber, styrene-butadiene rubber, acrylonitrile-butadiene rubber, isoprene rubber, chloroprene rubber, ethylene-propylene-butadiene rubber, etc. as the rubbery polymer (A). It is possible to produce an impact-resistant resin that is applicable to various applications, has an excellent uniform fine granule shape, has good thermal stability, and has excellent impact resistance, moldability, and appearance during molding. Make it. In this case, the rubbery polymer (A) contains 60% by weight or more of a diene monomer in its monomer composition, and the degree of crosslinking is equal to the gel content.
70% or more, and the degree of swelling must be within the range of 10 to 35. If the diene content and degree of crosslinking are other than these, it must have excellent impact resistance, moldability, and appearance during molding. It is not possible to obtain a composition with When using a rubbery polymer component with a gel content of less than 70% and/or a swelling degree of more than 35, which is uncrosslinked or has an insufficient degree of crosslinking, the rubber particles in the composition may aggregate during molding and the resin may flow. deformed in the direction,
Defects such as lack of surface gloss and poor appearance during molding appear. On the other hand, when a rubbery polymer with an excessive degree of crosslinking and a swelling degree of less than 10 is used, it has the disadvantage of poor impact resistance. Regarding particle size, in the case of resin compositions obtained by dispersing rubber particles in a continuous resin phase, if the particle size is too small, impact resistance will generally be poor, and conversely, if the particle size is too large, molding process will be difficult. The disadvantage of being inferior in sex appears. For the reasons mentioned above, in the present invention, the particle size of the rubbery polymer (A) is determined by weight in order to obtain a well-balanced composition with excellent impact resistance, molding processability, and appearance during molding. The average particle size is 0.2-0.4μ, with the majority of particles being 0.03-0.5μ.
It is necessary to be within the range of . Ethylene monomers used in the emulsion polymerization section as the first step and the suspension polymerization section as the second step of the present invention include styrene, α-methylstyrene,
an aromatic vinyl monomer such as P-substituted styrene;
Vinyl monomers copolymerizable with this, such as acrylonitrile, methacrylonitrile, acrylic ester, and methacrylic ester, are used. It does not matter whether the types of monomers used in the emulsion polymerization section and the suspension polymerization section are the same or different. The ratio of aromatic vinyl monomer and vinyl monomer copolymerizable with aromatic vinyl monomer is 50 to 100% by weight of aromatic vinyl monomer and vinyl monomer in terms of impact resistance and moldability. It is necessary to set it as 50-0 weight%. It does not matter whether this ratio is the same or different for the monomers used in the emulsion polymerization section and the monomers used in the suspension polymerization section. The proportion of the rubbery polymer (A) is preferably 5 to 70% by weight of the graft copolymer (E), which is the resulting impact-resistant resin, and when the rubber content is less than 5%, the impact-resistant If it exceeds 70%, the rubber particles will aggregate during the polymerization reaction and/or molding process, making the polymerization reaction unstable and/or causing poor moldability and appearance during molding process. There are things to do. It is generally difficult to achieve a polymerization conversion rate of 100% in the emulsion polymerization section, which is the first step of the emulsion suspension polymerization method, but in the method of the present invention, a certain amount of unreacted monomer remains (polymerization conversion rate 75% or more), it is possible to produce an impact-resistant resin that has excellent impact resistance, molding processability, and appearance during molding even when transferred to the second stage of suspension polymerization. The graft copolymer (C) latex, which is the product of the emulsion polymerization section, is mixed with the rubbery polymer (A) in the reaction vessel.
It is obtained by adding a latex, an emulsifier, a polymerization initiator, a monostere (B) and, if necessary, a chain transfer agent, and carrying out emulsion polymerization at 40 to 120°C. As the emulsifier, known anionic emulsifiers such as sodium alkylbenzenesulfonate can be used. As the polymerization initiator, water-soluble inorganic initiators such as persulfates and perborates can be used alone or in combination with sulfites, bisulfites, thiosulfates, etc. as redox initiators. Redox initiator systems such as organic hydroperoxide-ferrous salts, organic hydroperoxide-sodium formaldehyde sulfoxylates may also be used. In the method of the present invention, adjustment of the degree of polymerization and free polymer ratio are important factors, as will be described later. A chain transfer agent is used if necessary to adjust the degree of polymerization and free polymer ratio, and chain transfer agents include alkyl mercaptans, alkyl halides, alkyl sulfides, alkyl disulfides, thioglycolic acid esters, α - Alkylmercaptans are particularly preferred, although methylstyrene dimers are also used. The time required for polymerization varies depending on the type and amount of initiator, polymerization temperature, etc., but is usually 0.5 to 10 hours. Regarding the graft copolymer (C), what is important in the present invention is that the free polymer ratio is 20% or more and the acetone soluble content ηsp/C is 0.30 to 1.0 dl/g. When ηsp/C is less than 0.30 dl/g, moldability and appearance during molding are generally good, but excellent impact resistance cannot be obtained. Surprisingly, even if various modification methods were tried in the suspension polymerization section, this property could not be changed. Furthermore, if the free polymer ratio is less than 20% and/or the acetone-soluble content ηsp/C exceeds 1.0 dl/g, the system often becomes unstable at the time of phase transition from an emulsified state to a suspended state. It may cause a cake-like phenomenon or the formation of enlarged particles.
Furthermore, even if the polymerization reaction is completed smoothly, a composition having excellent moldability and appearance during molding cannot be obtained. That is, the fluidity of the product is poor, making it difficult to mold it at normal temperatures and pressures, and the appearance of the molded product also lacks smoothness. The graft copolymer (E) is prepared by adding a partial flocculant such as an acidic substance or an electrolyte substance, a suspension polymerization stabilizer, a monomer (D), and a polymerization initiator to the graft copolymer (C) latex. Obtained by suspension polymerization at ℃. As a partial flocculant, any acid or water-soluble inorganic salt can be used. Examples of acids include mineral acids such ^as sulfuric acid and hydrochloric acid, and organic acids (benzoic acid, salicylic acid, salicylic acid, (including formic acid and tartaric acid). Salts include, but are not limited to, sulfates such as magnesium sulfate and sodium sulfate, chlorides, and acetates. As the suspension polymerization stabilizer, ordinary inorganic dispersants and organic dispersants can be used. Examples of inorganic dispersants include magnesium carbonate and tribasic calcium phosphate. Among organic dispersants, natural and synthetic polymer dispersants include starch, gelatin, acrylamide, partially saponified polyvinyl alcohol, partially saponified polymethyl methacrylate, polyacrylic acid and its salts, cellulose, methyl cellulose, hydroxymethyl cellulose. , hydroxyethyl cellulose, polyalkylene oxide, polyvinylpyrrolidone, polyvinylimidazole, sulfonated polystyrene, etc. Also, as a low molecular weight dispersant, common emulsifiers such as alkylbenzene sulfonates and fatty acid salts can also be used. Graft copolymer (C) latex, partial flocculant,
The order of addition of monomer (D) and suspension polymerization stabilizer is that it is necessary to add monomer D and suspension polymerization stabilizer after adding the partial flocculant to the graft copolymer (C) latex. The monomer (D) and the suspension polymerization stabilizer may be added at the same time, or the suspension polymerization stabilizer may be added after the monomer (D) is added. If the addition order is other than this, the polymerization system will become unstable, and coarse granules may be formed or a cake-like phenomenon may occur. As the polymerization initiator for suspension polymerization, peroxides such as benzoyl peroxide and lauroyl peroxide, and azo compounds such as azobisisobutyronitrile are used. In addition, a chain transfer agent may be used to adjust the degree of polymerization, and examples of chain transfer agents include alkyl mercaptans having 2 to 18 carbon atoms, thioglycolic acid esters,
Ester mercaptans such as β-mercaptopropionic acid ester, mercapto acids such as thioglycolic acid and β-mercaptopropionic acid, benzyl mercaptan, or aromatic mercaptans such as thiophenol, thiocresol, and thionaphthol can be used, but in particular Preferably carbon number is 4~
12 alkyl mercaptans. There are no particular restrictions on the method of adding the polymerization initiator and chain transfer agent, but there are methods in which both the polymerization initiator and chain transfer agent are dissolved in the monomer (D), and methods in which one is dissolved in the monomer (D) and the other is dissolved in the monomer (D). Adding one or both to the graft copolymer (C) latex, Partial flocculant, Suspension polymerization stabilization method A method of adding the agent to a mixed system of monomer (D), etc. is used. The time required for polymerization varies depending on the type and amount of initiator, polymerization temperature, etc., but is usually 0.5~
It is 10 hours. It is also possible to add plasticizers, lubricants, stabilizers, ultraviolet absorbers, etc. during the suspension polymerization.
The impact-resistant resin obtained by the present invention can also be used with other resins such as polypropylene, polystyrene,
By mixing with vinyl polymers such as acrylonitrile-styrene copolymer, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, thermoplastic polyester, polyamide, etc., moldability and impact resistance can be significantly improved. It becomes possible. In the following examples, parts represent polymerized parts, and % represents weight %. Example 1 (Mixture 1) Polybutadiene latex (solid content) ^*
60 parts (30 parts) Ferrous sulfate 0.003 parts Dextrose 0.5 parts Sodium pyrophosphate 0.2 parts Disproportionated rosin acid soap 2.5 parts Caustic soda 0.1 parts Sodium methylene bisnaphthalene sulfonate
0.2 parts Deionized water 150 parts *Solid content 50% Swelling degree 16.0 Gel content 83.1% Weight average particle size 0.33μ Monomer composition 90% butadiene, 10% styrene (Mixture 2) Styrene 22.2 parts Acrylonitrile 7.8 parts Kyumene hydroperoxide 0.33 parts After charging 0.1 part of tertiary dodecyl mercaptan (Mixture 1) into a reactor and purging the inside of the reactor with nitrogen, (Mixture 2) was added dropwise over 30 minutes while stirring at 60°C and a stirring speed of 200 rpm. Thereafter, polymerization was carried out for 3 hours to complete the reaction and a graft copolymer latex was obtained. Polymerization conversion rate is 80%
and the free polymer ratio of the graft copolymer is
37%, and the acetone soluble content ηsp/C was 0.56 dl/g. The resulting graft copolymer latex (PH
11.0) to room temperature and stirred at 350 rpm for 10
% sulfuric acid aqueous solution to form a highly viscous partial aggregate (PH2.8), then 29.6 parts of styrene, 10.4 parts of acrylonitrile, and benzoyl peroxide.
When a mixture of 0.2 parts of tertiary butyl mercaptan and 0.5 parts of tertiary butyl mercaptan was added, the dispersion changed from a high viscosity state to a low viscosity state (10 centipoise). To this dispersion, add a suspension stabilizer, a sulfonated polystyrene sodium salt aqueous solution (0.3%, number average molecular weight
20000) was added and polymerized at 80°C for 5 hours. After the polymer was filtered off, it was washed, dehydrated, and dried using a bucket-type centrifugal dehydrator. The polymerization conversion rate was 97%, and the obtained polymer was a beautiful bead body having a particle size distribution as shown below.

[Table] 50 parts of dry particles, acrylonitrile styrene copolymer (ηsp/C (25°C DMF) = 0.60) 50
part and 0.4 parts of calcium stearate
After mixing in a 10 volume Henschel mixer at 3000 rpm, the mixture was pelletized and a test piece was formed by injection molding. The molded product had no tropical color and had an extremely high surface gloss. Comparative example 1-1 The same material as in Example 1 (mixture 1) was charged into a reactor, and after replacing the inside of the reactor with nitrogen, the mixture was heated at 45°C and 200 rpm.
The same mixture as in Example 1 (mixture 2) was added dropwise over 5 minutes while stirring at a stirring speed of . Thereafter, polymerization was carried out for 3 hours to complete the reaction and a graft copolymer latex was obtained. The polymerization conversion rate was 77%, the free polymer rate of the graft copolymer was 45%, and the acetone soluble content ηsp/C was 1.09 dl/g. Thereafter, a test piece was prepared in the same manner as in Example 1. Comparative Example 1-2 (Mixture 2) Styrene 22.2 parts Acrylonitrile 7.8 parts Qumene hydroperoxide 0.33 parts Tertiarydodecyl mercaptan 0.8 parts The same as in Example 1 (Mixture 1) was charged into a reactor, and the inside of the reactor was replaced with nitrogen. , 200rpm at 75℃
Add the above (mixture 2) while stirring at a stirring speed of
It was added dropwise over 90 minutes. Thereafter, polymerization was carried out for 3 hours to complete the reaction, and a kraft copolymer latex was obtained. The polymerization conversion rate was 84%, the free polymer rate of the graft copolymer was 42%, and the acetone soluble content was η.
sp/C was 0.26 dl/g. Thereafter, a test piece was prepared in the same manner as in Example 1. Example 2 (Mixture 1) Polybutadiene latex (solid content) ^*
90 parts (45 parts) Ferrous sulfate 0.005 parts Dextrose 0.5 parts Sodium pyrophosphate 0.2 parts Disproportionated rosin acid soap 1.0 parts Caustic soda 0.02 parts Sodium methylene bisnaphthalene sulfonate
0.2 parts Deionized water 150 parts *Solid content 50% Swelling degree 24.0 Gel content 76.3% Weight average particle size 0.28μ Monomer composition Butadiene 100% (Mixture 2) Styrene 14.8 parts Acrylonitrile 5.2 parts Kyumene hydroperoxide 0.2 parts (Mixture 3) Styrene 11.1 parts Acrylonitrile 3.9 parts Kyumene hydroperoxide 0.3 parts Tertiary dodecyl mercaptan 0.3 parts (Mixture 1) was charged into a reactor, the inside of the reactor was purged with nitrogen, and the mixture was stirred at 60°C at a stirring speed of 150 rpm. 2) was added dropwise over 10 minutes. One hour after the completion of the dropwise addition, (mixture 3) was added dropwise over a period of 30 minutes. Thereafter, polymerization was carried out for 3 hours to complete the reaction, and a graft copolymer latex was obtained. The polymerization conversion rate was 88%, the free polymer rate of the graft copolymer was 36%, and the acetone soluble content was ηsp/C.
was 0.54 dl/g. The resulting graft copolymer latex (PH
10.8) was brought to room temperature and after adding 2 parts of tertiary dodecyl mercaptan under stirring at 350 rpm.
Add 8 parts of 10% sulfuric acid aqueous solution to form a high viscosity partial aggregate (PH3.0), then add 15.0 parts of styrene,
When a mixture of 5.0 parts of acrylonitrile and 0.3 parts of azobisisobutyronitrile is added, at the same time 10 parts of a 0.3% aqueous solution (number average molecular weight 20000) of a sulfonated polystyrene salt as a suspension stabilizer is added.
The dispersion changed from a high viscosity state to a low viscosity state (10 centipoise). This dispersion was polymerized by heating at 80°C for 5 hours. After filtering off the polymer, it was washed and dehydrated using a basket-type centrifugal dehydrator and dried. The polymerization conversion rate was 97%, and the obtained polymer was a beautiful bead body with a particle size distribution as shown below.

[Table] 35 parts of dried particles, acrylonitrile-styrene copolymer (ηsp/C (25°C DMF) = 0.61) 65
part, and 0.4 parts of calcium stearate.
After mixing in a 10 volume Henschel mixer at 3000 rpm, the mixture was pelletized and a test piece was formed by injection molding. The molded product had no tropical color and had extremely excellent surface gloss. Comparative example 2-1 As polybutadiene latex, solid content 50
%, swelling degree 24.8, gel content 86.3%, weight average particle diameter 0.07μ, and monomer composition 100% butadiene, except that a test piece was prepared in the same manner as in Example 2. Comparative Example 2-2 A graft copolymer latex obtained in the same manner as in Example 2 was used, and a monomer mixture, a flocculant,
Suspension stabilizers were added in this order. Although it formed a lump during heating, it was crushed to create a test piece. Example 3 (Mixture 1) Polybutadiene latex (solid content) ^*
120 parts (60 parts) Dextrose 1.0 parts Disproportionated rosin acid soap 2.5 parts Caustic soda 0.06 parts Sodium methylene bisnaphthalene sulfonate
0.2 parts Deionized water 180 parts* Same as used in Example 1 (Mixture 2) Styrene 18.5 parts Acrylonitrile 6.5 parts Yumene hydroperoxide 0.3 parts Tertiary dodecyl mercaptan 0.1 part (Mixture 3) Ferrous sulfate 0.005 parts Pyrophosphoric acid 0.2 parts of soda and 20 parts of deionized water (Mixture 1) were charged into a reactor, and after purging the inside of the reactor with nitrogen, (Mixture 2) was added dropwise over 60 minutes while stirring at 60°C and a stirring speed of 200 rpm. Thirty minutes after starting dropwise addition of (Mixture 2), (Mixture 3) was added dropwise over 5 minutes. After the addition of (Mixture 2) was completed, polymerization was carried out for 3 hours to complete the reaction and a graft copolymer latex was obtained. Polymerization conversion rate is 84%
and the free polymer ratio of the graft copolymer is
At 21%, the acetone soluble content ηsp/C was 0.37 dl/g. Example 1 except that a mixture of 11.1 parts of styrene, 3.9 parts of acrylonitrile, 0.1 part of benzoyl peroxide, and 0.2 parts of tertiary butyl mercaptan was used in the obtained graft copolymer latex.
Suspension polymerization was carried out in the same manner as above to obtain bead-shaped polymer particles. 25 parts dry particles, acrylonitrile
Styrene copolymer (ηsp/C (25℃DMF)=
0.60) and 0.4 parts of calcium stearate were mixed in a 10 volume Henschel mixer at 3000 rpm, pelletized, and a test piece was formed by injection molding. The molded product had no tropical color and had extremely excellent surface gloss. Various resin properties of the above Examples and Comparative Examples are summarized in Table 1.

【table】

Claims (1)

[Claims] 1. Adding an ethylenic monomer or a monomer mixture (B) to a rubbery polymer (A) latex and carrying out emulsion polymerization to produce a graft copolymer (C) latex, and then After adding an acidic substance or an electrolyte substance to the graft copolymer (C) latex and causing partial aggregation,
Either the ethylenic monomer or monomer mixture (D) is added first and then the suspension polymerization stabilizer is added, or the ethylenic monomer or monomer mixture (D) and the suspension polymerization stabilizer are added. In a method comprising simultaneously adding carbon dioxide and suspending polymerization to obtain the graft copolymer (E) in the form of beads, (1) the rubbery polymer (A) contains at least 60% by weight of the diene monomer component; (2) (B) and (D) The ethylenic monomer or monomer mixture contains 50 to 100 aromatic vinyl monomers, respectively.
Weight% and vinyl monomer copolymerizable with it: 50~
0% by weight (3) Graft copolymer (C) has a free polymer content of 20%
The reduced viscosity of the acetone soluble content is 0.30 to 1.0.
dl/g.