JPS6252761B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an aromatic vinyl copolymer having a high heat distortion temperature. More specifically, the present invention relates to a method for producing a granular copolymer containing a specific aromatic vinyl compound and maleic anhydride and having a high heat distortion temperature by bulk-suspension polymerization. Copolymers made of styrene and maleic anhydride have high heat distortion temperatures and are therefore used in many fields. In addition, this copolymer has good miscibility with styrene resins such as styrene-acrylonitrile copolymer (SAN resin), so it can be mixed with other styrene resins such as SAN resin or ABS resin. It is also known to be effective in improving the heat distortion temperature of resins (Japanese Patent Publication No. 46-859 and Japanese Patent Publication No. 47-50775).
Publication No.). Styrene and maleic anhydride have high alternating copolymerizability, and under normal radical polymerization conditions, alternating copolymerization with a molar ratio of styrene and maleic anhydride of 1:1 is possible for a wide range of monomer charge compositions. A union is generated. Since this alternating copolymer is insoluble in styrene monomer, the resulting copolymer precipitates out of the styrene monomer solution, making it impossible to carry out polymerization in a homogeneous system. In addition, maleic anhydride reacts with water and easily undergoes hydrolysis, resulting in a chemical change to maleic acid. Therefore, a copolymer of styrene and maleic anhydride is produced by emulsion polymerization or suspension polymerization using water as a medium. That is difficult. Therefore, as a method for producing styrene-maleic anhydride copolymers of any composition with good economic value, polymerization at a rate substantially lower than that of alkenyl aromatic monomers in the presence of an organic solvent is recommended. A solvent bulk polymerization method has been proposed in which an aromatic vinyl monomer and maleic anhydride are polymerized while adding maleic anhydride (Japanese Patent Laid-Open No. 48-42091). Although this method can yield a copolymer with an arbitrary composition, it has the disadvantage that it requires a recovery step and large-scale equipment for bulk polymerization because it uses an organic solvent. Also styrene 99.9-60% by weight, maleic anhydride
A method of bulk polymerizing a vinyl monomer consisting of 0.1 to 10.0% by weight and, if necessary, 0 to 40% by weight of a vinyl compound copolymerizable with these to substantially polymerize maleic anhydride, followed by suspension polymerization ( Japanese Unexamined Patent Publication 1973-
88189) has also been proposed, but the maleic anhydride content of the copolymer obtained by this method is at most
10% by weight, so a high heat distortion temperature cannot be expected. On the other hand, a method of radical polymerizing a mixture containing 10 to 90% by weight of an α-substituted aromatic vinyl compound, 5 to 30% by weight of maleic anhydride, and 3 to 50% by weight of an unsaturated nitrile compound (Japanese Unexamined Patent Publication No. 53-2591) has been proposed, but this method focuses on polymerizing α-substituted aromatic vinyl compounds, which have a slow polymerization rate, in a short time, and does not concern the heat distortion temperature of the resulting copolymer. Furthermore, it is difficult to obtain a copolymer containing 10% by weight or more of maleic anhydride in the bulk polymerization or solution polymerization employed in this method. Therefore, the present inventors have made extensive studies to solve the above problems and obtain a copolymer of an aromatic vinyl polymer and maleic anhydride containing 10% by weight or more of maleic anhydride by a simple method. If a monomer mixture consisting of maleic anhydride, an aromatic vinyl monomer, and acrylonitrile with a specific composition is subjected to radical bulk polymerization, the resulting copolymer will not precipitate from the monomer phase and will be in a uniform state. After the bulk polymerization proceeds while the maleic anhydride is maintained, and the maleic anhydride is substantially completely polymerized, the polymerization system is transferred to an aqueous system and suspension polymerization is performed. It was discovered that a copolymer of a polymer and maleic anhydride can be obtained, and the present invention was achieved. That is, the present invention consists of a mixture of 65 to 90% by weight of acrylonitrile and an aromatic vinyl compound in which the weight ratio of the aromatic vinyl compound containing 60% by weight or more of acrylonitrile/styrene is 0.17 to 1.5, and 10 to 35% by weight of maleic anhydride. A vinyl monomer mixture is subjected to radical bulk polymerization until the polymerization rate reaches 20 to 75%, and then the polymerization is completed by suspension polymerization using water as a medium.
The present invention provides a method for producing a granular copolymer containing 35% by weight. In the initial monomer composition of the present invention, the maleic anhydride content is selected from the range of 10 to 35% by weight, preferably 15 to 30% by weight. If the proportion of maleic anhydride is less than 10% by weight, the heat distortion temperature of the resulting copolymer will not be high enough, and if it is more than 35% by weight, the maleic anhydride will be substantially completely removed in the bulk polymerization stage. If the polymerization is carried out to the stage of polymerization, the viscosity of the polymerization system becomes too high, making it impossible to proceed to suspension polymerization, which is not preferable. The remaining initial monomer composition consists of an aromatic vinyl compound and acrylonitrile, with a total of 90 to 65
% by weight, and acrylonitrile/aromatic vinyl compound=0.17 to 1.5 (weight ratio), preferably the total of aromatic vinyl compound and acrylonitrile is 85 to 70% by weight, and acrylonitrile/aromatic vinyl compound= Selected from the range of 0.2 to 1.0 (weight ratio). When other monomers are selected instead of acrylonitrile, it is difficult to maintain a uniform polymerization system and it is difficult to carry out bulk-suspension polymerization using known stirring means, which is not preferred. Furthermore, if the acrylonitrile/aromatic vinyl compound (weight ratio) in the initial monomer composition is less than 0.17, the copolymer formed in the bulk stage will precipitate and precipitate from the polymerization system, resulting in a transition to suspension polymerization. If it exceeds 1.5, the resin becomes significantly colored during the bulk polymerization stage, which is not preferable. The aromatic vinyl compound and acrylonitrile may all be added at the beginning of the polymerization, but if desired, a portion may be added in portions during the bulk polymerization stage. It is also possible to add small amounts of other monomers or solvents within a range that does not interfere with the uniformity of the polymerization solution in the bulk polymerization stage. The termination stage of the bulk polymerization is selected from the stage at which the polymerization rate is 20 to 75%, at which the charged maleic anhydride is substantially completely polymerized. The polymerization rate required to completely polymerize maleic anhydride increases in proportion to the initial amount of maleic anhydride charged, and therefore the viscosity of the bulk polymerization system also increases. At the end of bulk polymerization, an aromatic vinyl compound and/or acrylonitrile can be added to reduce the viscosity of the polymerization system. When stopping bulk polymerization at a polymerization rate of 20% or less, even if the initial amount of maleic anhydride charged is relatively small, maleic anhydride cannot be completely polymerized, and if the transition to suspension polymerization continues, residual This is not preferred because maleic anhydride reacts with water.
Furthermore, when bulk polymerization is stopped at a polymerization rate of 75% or more, the viscosity of the bulk polymerization system becomes abnormally high, making it extremely difficult to shift to suspension polymerization, which is not preferable. The bulk polymerization system in which maleic anhydride has been substantially completely polymerized is then transferred to a suspension polymerization system using water as a medium. The suspension polymerization is continued until the polymerization is substantially complete, and the copolymer is finally recovered in the form of easy-to-handle granules. Among the aromatic vinyl compounds containing 60% by weight or more of styrene used in the present invention, the aromatic vinyl compounds other than styrene include α-methylstyrene,
It is a monomer that is so-called styrene such as chlorstyrene and its substituted products. There are no particular restrictions on the polymerization initiator or polymerization temperature used in the bulk polymerization and suspension polymerization of the present invention, and azo initiators such as 2,2'-azobis-2,4-dimethylparellonitrile, benzoyl peroxide, etc. A free radical-generating initiator such as a peroxide-based initiator, etc., or non-catalytic thermal polymerization is used, and a temperature condition of 50°C to 150°C is preferable. Further, polymerization degree regulators such as mercaptans, lubricants, stabilizers, etc. can be added to the polymerization system as necessary. There are no particular limitations on the suspending agent during suspension polymerization, and known suspending agents such as polyvinyl alcohol, polyacrylamide, or barium sulfate can be used. The granular copolymer containing 10% by weight or more of maleic anhydride produced by the method described above has a high heat distortion temperature and has excellent other mechanical properties. Furthermore, this copolymer has excellent miscibility with resins known as so-called ABS resins or MBS resins, and since it is produced in granular form, mixing operations are easy. That is, so-called ABS resin or MBS resin, which is obtained by graft-copolymerizing a diene rubber polymer, an acrylic rubber polymer, etc. with an aromatic vinyl heavy material and/or a methacrylic acid ester monomer, and/or acrylonitrile, etc.; By blending this copolymer, it is possible to produce an impact-resistant resin that has a high heat deformation temperature and high impact strength. In this case, ABS resin or
In the MBS resin, the mixing ratio of the rubbery polymer and the monomer to be graft-polymerized is arbitrary, and can usually be selected from the range of 10 to 90% by weight of the rubbery polymer and 90 to 10% by weight of the monomer. Furthermore, the mixing ratio of the resin such as ABS resin and the copolymer of the present invention containing maleic anhydride can be arbitrarily selected depending on the purpose. It may be selected from the range of ~5% by weight. Furthermore, if desired, it is also possible to simultaneously mix a styrene-acrylonitrile copolymer or the like. There are no particular restrictions on the mixing method, and mixing can be performed by any commonly used method. It is also possible to add stabilizers, lubricants, fibrous reinforcing agents, coloring agents, etc. when mixing these. According to the present invention described above, the following advantages can be obtained. (1) A copolymer containing 10 to 35% by weight of maleic anhydride can be obtained, and as a result,
Compared to other styrene resins such as SAN resin,
The heat distortion temperature of the copolymer is significantly improved. (2) Since it is not necessary to use organic solvents in the manufacturing process, there is no need for a recovery process, and therefore the bulk-suspension polymerization method can be easily carried out using relatively simple industrial equipment. A granular copolymer can be obtained. (3) The copolymer of the present invention has good miscibility with resins such as so-called ABS resins and MBS resins, and has a high heat distortion temperature due to the miscibility of this copolymer with these resins. A resin with excellent impact resistance can be produced. Hereinafter, the present invention will be explained with reference to Examples. Note that the numbers in the examples represent parts by weight. Heat distortion temperature is ASTM D-648-56 or
Measured according to BS2782, 102C. In the following description, BS method HDT is the heat distortion temperature measured according to BS2782, 102C. Example 1 [Production of copolymer (A)] 1.91 kg of styrene and 0.64 kg of acrylonitrile were placed in 15 polymerization tanks equipped with a reflux condenser and a stirrer.
Kg, maleic anhydride 0.45Kg, 2・2′-azobis-
0.6 g of 2,4-dimethylvaleronitrile and 30 g of n-dodecylmercaptan were charged and sufficiently dissolved. When the temperature inside the tank was kept at 75°C and stirring was performed, polymerization started and the viscosity of the polymerization solution gradually increased. Approximately 2 hours after the start of polymerization, the viscosity stopped increasing and the polymerization almost stopped. This polymerization solution was a colorless and transparent viscous liquid, and the polymerization rate was 43%. Analysis of the composition of the remaining monomers by gas chromatography revealed that styrene was 69.3% by weight and acrylonitrile was 30.2% by weight.
% by weight, and 0.5% by weight of maleic anhydride. At this point, 0.21 kg of styrene and 6 g of 2,2'-azobisisobutyronitrile were added and dissolved sufficiently, and then methyl methacrylate/acrylamide = 20/
Suspension polymerization was started by adding 4.5 g of ion-exchanged water in which 3.4 g of 80 (weight ratio) copolymer and 1.1 g of sodium dihydrogen phosphate were dissolved. 2 hours at 75℃, 1 hour at 90℃
The polymerization was completed by holding for a certain period of time. The polymer was washed with water and dried to obtain a granular copolymer (A). The content of maleic anhydride in the copolymer was determined to be 14.0% by weight by elemental analysis. The heat distortion temperature (BS method HDT) was 131.5°C. Example 2 [Manufacture of copolymer (B)] Styrene 1.92% was placed in an autoclave equipped with a stirrer.
Kg, acrylonitrile 0.48Kg, maleic anhydride
0.60Kg, 2,2'-azobis-2,4-dimethylvaleronitrile 0.6g, tert-butyl peroxybenzoate 6g, tert-dodecyl mercaptan 30
g was charged and sufficiently stirred to dissolve. Tank temperature 75
When kept at ℃, the polymerization rate reached 48% in 2 hours, and polymerization hardly progressed. At this time, when the remaining monomer was quantified using gas chromatography, styrene was detected.
73.1% by weight, 26.1% by weight of acrylonitrile and 0.8% by weight of maleic anhydride. Next, polyvinyl alcohol with a saponification degree of 80%
Suspension polymerization was started by adding 4.5 g of ion-exchanged water in which 30 g of ion-exchanged water was dissolved. The polymerization was completed by holding at 105°C for 2 hours and at 120°C for 1 hour. The polymer was washed with water and dried to obtain a granular copolymer (B). The maleic anhydride content in the copolymer was determined to be 19.8% by weight by elemental analysis.
The heat distortion temperature (BS method HDT) was 141.7°C. Example 3 [Production of copolymer (C)] In the same polymerization tank as in Example 1, 2.04 kg of styrene, 0.51 kg of acrylonitrile, 0.45 kg of maleic anhydride, n
~30g of dodecyl mercaptan and 6g of tert-butylperoxybenzoate were charged and heated to 8.5g at 75°C.
Time-thermal bulk polymerization was carried out. At this time, the polymerization rate reached 41%, and the composition of the remaining monomers determined by gas chromatography was 75.2% by weight of styrene, 24.2% by weight of acrylonitrile, and 0.6% by weight of maleic anhydride. Next, polyvinyl alcohol 20 with a saponification degree of 80%
Suspension polymerization was started by adding 4.5 g of ion-exchanged water in which 4.5 g of ion-exchanged water had been dissolved. The polymerization was completed by holding at 105°C for 2 hours and at 120°C for 1 hour. The polymer was washed with water and dried to obtain a granular copolymer (C). The maleic anhydride content calculated from elemental analysis was 15.0% by weight. Heat distortion temperature (BS method
HDT) was 134.5°C. Example 4 [Production of copolymer (D)] In the same polymerization tank as in Example 1, α-methylstyrene was added.
0.765Kg, styrene 1.275Kg, acrylonitrile
0.51 kg, maleic anhydride 0.45 kg, tert-dodecyl mercaptan 6 g, and benzoyl peroxide 9 g were charged, and polymerization was carried out while maintaining the temperature at 75°C. The polymerization rate reached 40% in 4 hours, and maleic anhydride in the remaining monomers was substantially consumed at 0.4% by weight. Then methyl methacrylate/acrylamide=
Suspension polymerization was carried out by adding 4.5 g of ion-exchanged water in which 3.4 g of a 20/80 (weight ratio) copolymer and 1.1 g of sodium hydrogen phosphate were dissolved. Polymerization was completed by holding at 75°C for 6 hours and at 95°C for 2 hours. The polymer was washed with water and dried to obtain a granular polymer (D).
The maleic anhydride content in the copolymer is 14.9% by weight
It was hot. The heat distortion temperature (BS method HDT) was 141.0°C. Example 5 [Production of copolymer (E)] In the same polymerization tank as in Example 1, 1.47 kg of styrene, 0.63 kg of acrylonitrile, 0.9 kg of maleic anhydride,
0.6 g of 2,2'-azobis-2,4-dimethylvaleronitrile and 30 g of n-dodecylmercaptan
After being charged and sufficiently dissolved, polymerization was carried out at 75°C. The viscosity gradually increased and became quite high 2 hours after the start of polymerization, so 1.32 kg of styrene,
6 g of 2,2'-azobisisobutyronitrile was added and sufficiently dissolved, and 4.5 g of ion-exchanged water in which 15 g of polyvinyl alcohol with a degree of saponification of 80% was dissolved was added to initiate suspension polymerization. Polymerization was completed by holding at 75°C for 2 hours and at 95°C for 1 hour. A granular copolymer (E) was obtained. The maleic anhydride content in the copolymer was 20.5% by weight. The heat distortion temperature (BS method HDT) was 142.1°C. The polymerization rate at the end of the bulk polymerization was 65% by weight, and the composition of the remaining monomers at that time was 46.0% by weight of styrene, 53.1% by weight of acrylonitrile, and 0.9% by weight of maleic anhydride. Comparative Example 1 [Manufacture of copolymer (F)] In the same polymerization tank as in Example 1, 2.07 kg of styrene, 0.69 kg of acrylonitrile, 0.24 kg of maleic anhydride,
Polymerization was carried out by charging 0.6 g of 2,2'-azobis-2,4-dimethylvaleronitrile and 30 g of n-dodecylmercaptan. When the temperature inside the tank was maintained at 75°C, the polymerization rate reached 29% by weight in 2 hours. The composition of the remaining monomers at this time was 71.2% by weight of styrene, 28.6% by weight of acrylonitrile, and 0.2% by weight of maleic anhydride. Next, 0.12 kg of styrene and 6 g of 2,2'-azobisisobutyronitrile were added, and suspension polymerization was carried out in the same manner as in Example 1. The polymerization was completed by holding at 75°C for 3 hours and at 90°C for 1 hour. A granular copolymer (F) was obtained, but the heat distortion temperature (BS method HDT) was only 107°C. The maleic anhydride content in the copolymer was 7.7% by weight. If the maleic anhydride content is less than 10% by weight, a high heat distortion temperature cannot be obtained. Comparative Example 2 Styrene 1.32Kg, acrylonitrile 0.57Kg, maleic anhydride 1.11Kg, n
- 30 g of dodecyl mercaptan was charged and polymerization was carried out. When the polymerization was carried out at 70℃ for 2 hours and then at 80℃ for 4 hours, the viscosity of the polymer increased, and if the viscosity increased further, stirring became difficult, so 2.2'-
Azobisisobutyronitrile 6g, styrene 0.9
Kg was added and suspension polymerization was started in the same manner as in Example 3, keeping the temperature at 75°C. However, suspension stability is poor,
The polymerized product precipitated into a lump and the polymerization could not be completed. The polymerization rate when bulk polymerization was stopped was 70.3% by weight,
The remaining monomer composition at this time is maleic anhydride 22.6
wt%, styrene 21.2wt%, acrylonitrile
It was 56.2% by weight. The amount of maleic anhydride charged is
If it is 35% by weight or more, a large amount of maleic anhydride remains during suspension polymerization, which is hydrolyzed in hot water and dissolved in water, resulting in poor suspension stability and suspension polymerization cannot be carried out. Comparative Example 3 In a three-neck flask equipped with a reflux condenser and a stirrer, 255 g of styrene and 45 g of maleic anhydride were added.
Add 3g of n-dodecylmercaptan and 3g of n-dodecylmercaptan, 2,2'-azobis-2,4-
After 60 mg of dimethylvaleronitrile was charged and thoroughly mixed and dissolved, polymerization was started at 75°C. Approximately 30 minutes after the start of the polymerization, the copolymer formed became a lump and precipitated, making stirring difficult, so the polymerization was stopped. In a system that does not contain acrylonitrile, the copolymer produced does not dissolve in the monomer solution but precipitates, so a homogeneous state cannot be maintained and bulk polymerization cannot be performed. That is, in a system containing 10 parts or more of maleic anhydride, bulk polymerization cannot be carried out in the absence of acrylonitrile. Comparative Example 4 Styrene 222 was placed in the same three-necked flask as Comparative Example 3.
g, acrylonitrile 33g, maleic anhydride 45g
3 g, n-dodecylmercaptan, and 60 mg of 2,2'-azobis-2,4-dimethylvaleronitrile were charged and sufficiently dissolved, and then polymerization was started at 75°C. Approximately 30 minutes after the start of the polymerization, the produced copolymer precipitated into a lump, making stirring difficult, so the polymerization was stopped. In this example, since the acrylonitrile/styrene (weight ratio) in the initial charge was 0.149, it was not possible to maintain a uniform polymerization system. That is, in a monomer solution where acrylonitrile/styrene <0.17 (weight ratio), the resulting copolymer does not dissolve but precipitates, making it impossible to uniformly polymerize. Comparative Example 5 [Manufacture of copolymer (G)] In the same polymerization tank as in Example 1, 0.89 kg of styrene, 1.45 kg of acrylonitrile, 0.66 kg of maleic anhydride,
Polymerization was carried out by charging 0.6 g of 2,2'-azobis-2,4-dimethylvaleronitrile and 30 g of n-dodecylmercaptan. When kept at 75°C for 2 hours, the polymerization rate reached 53% by weight, and the composition of the remaining monomers at this time was 8.9% by weight of styrene, 90.5% by weight of acrylonitrile, and 0.6% by weight of maleic anhydride. Next, 3.0 kg of styrene and 6 g of 2,2'-azobisisobutyronitrile were added and sufficiently dissolved, and suspension polymerization was carried out in the same manner as in Example 1 to complete the polymerization. A granular copolymer was obtained, but it had a yellowish color. A test piece was molded at 240°C to measure heat distortion temperature, but the test piece was colored brown. Its heat distortion temperature (BS method HDT) was 124°C. The composition of copolymer (G) was 11.0% by weight of maleic anhydride, 64.8% by weight of styrene, and 24.2% by weight of acrylonitrile. If AN/ST>1.5 (weight ratio) in the initial monomer charge, the resulting copolymer will be significantly colored, which is not preferred. Example 6 30 parts of a graft copolymer obtained by graft copolymerizing 60 parts of polybutadiene latex (solid content) with 28.5 parts of styrene and 11.5 parts of acrylonitrile, and the copolymers produced in Examples 1 to 5 and Comparative Example 1 ( A)
A resin composition was prepared by blending 70 parts of ~(E) and (F), and its physical properties were measured. The measurement results are summarized in Table 1. 【table】

Claims (1)

[Claims] 1 Vinyl monomer consisting of 65-90% by weight of a mixture of acrylonitrile and aromatic vinyl compound with a weight ratio of 0.17-1.5 of an aromatic vinyl compound containing 60% by weight or more of acrylonitrile/styrene and 10-35% by weight of maleic anhydride. The polymerization rate is 20
1. A method for producing a granular copolymer containing 10 to 35% by weight of maleic anhydride, which comprises carrying out radical bulk polymerization until the concentration of maleic anhydride reaches 75%, and then completing the polymerization by suspension polymerization using water as a medium.