JPS6123212B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an industrially advantageous method for producing impact-resistant high nitrile resins with extremely low residual monomer content and high gas barrier properties. So-called nitrile resins containing a high proportion of acrylonitrile units have excellent gas barrier properties and are used in foods,
Recognized as a useful packaging material in pharmaceuticals and other fields. In particular, rubber-reinforced copolymer resins of acrylonitrile and aromatic vinyl compounds have a high heat distortion temperature, and when used as packaging materials, they can be heat-filled and heat-sterilized, making them even more useful. increase. However, when used as a packaging material, the safety and hygiene of the material are extremely important. In particular, since the acrylonitrile monomer remaining in the material is highly reactive as a chemical substance, its toxicity becomes a problem if it migrates to the contents. Therefore, acrylonitrile remaining in the material must be strictly regulated. For this reason, it is usually necessary to rely on methods such as stripping the resin latex obtained by emulsion polymerization under reduced pressure or washing the resin powder, which significantly reduces productivity and economic efficiency in manufacturing. I had a problem with letting it happen. In the production of copolymers of acrylonitrile and aromatic vinyl compounds, due to the marked difference in radical polymerizability between the two, in ordinary radical polymerization methods, the composition ratio of the polymer produced differs between the early and late stages of polymerization, resulting in The resulting resin becomes non-uniform and has reduced impact resistance and thermal stability. This is because when acrylonitrile and an aromatic vinyl compound are charged and polymerized using a conventional method, a copolymer containing highly reactive aromatic vinyl in a higher proportion than the charged composition is obtained at the initial stage of polymerization. On the other hand, in the late stage of polymerization, polyacrylonitrile is produced.
For this reason, various proposals have been made regarding methods for producing copolymers of acrylonitrile and aromatic vinyl compounds having highly uniform compositions or rubber-reinforced copolymers. For example, Japanese Patent Publication No. 46-33574 discloses that when copolymerizing acrylonitrile and an aromatic vinyl compound in the presence of a diene rubber, a highly reactive aromatic vinyl compound is added at a rate that keeps the reflux temperature constant. In Japanese Patent Publication No. 48-16347, the monomer composition of the polymerization system is tracked using a gas chromatograph as the polymerization progresses, and monomers are added to keep the composition constant so that the composition is not too high. There is a method for obtaining a copolymer with a uniform composition in a high yield, or a method for adding an aromatic vinyl compound having a high reaction rate in accordance with the heat of polymerization in Japanese Patent Publication No. 49-1950. In all of the above proposed methods, the monomer composition is adjusted in advance so as to obtain a copolymer with the desired composition, and the monomer composition in the polymerization system is adjusted while monitoring the progress of the charging polymerization. By adding a portion of the monomer to keep it constant, a copolymer with a highly uniform composition is obtained. However, in these methods, a large amount of monomer is initially introduced into the polymerization system, making it difficult to remove the polymerization heat.
The degree of polymerization progress must be constantly monitored, the addition of monomer must be adjusted according to the progress, and monomer addition must be adjusted in order to achieve a high polymer conversion rate of 95% or more. There are problems such as the difficulty in adjusting the speed and the loss of uniformity of the copolymer, and the problem that the polymerization operation and equipment must be complicated to produce at a high conversion rate on an industrial scale. It was hot. The present inventors solved these problems and achieved safety and
As a result of intensive study on an industrially advantageous method for manufacturing this nitrile resin, which is reliable in terms of hygiene, we found that if we were to increase the polymerization rate to a conversion rate of 95% or higher, special operations would have to be carried out. They discovered that residual monomers in product resins can be significantly reduced by a known drying method, and have already filed a patent application. (Japanese Patent Application No. 51-141475), (Refer to Japanese Patent Application No. 57-39252)
If it is less than 95%, the residual monomer cannot be reduced without special operations, such as stripping or other expensive methods. In addition, regarding the method of finishing the reaction at such a significantly high conversion rate, conventionally it was said that attempting to raise the conversion rate to 90% or higher would result in the formation of undesirable polyacrylonitrile.
A conversion rate higher than that is industrially impossible, and therefore economically burdensome continuous polymerization methods have only recently been devised (Japanese Patent Laid-Open No. 51-56894,
and Japanese Patent Publication No. 51-92886). However, even in Japanese Patent Application No. 51-141475, serious problems remained in the polymer production process. That is, the polymer latex was extremely unstable and a large amount of scale was generated in the polymerization machine. However, the present inventors continued to solve these problems, and as a result, by adding alkyl acrylate or alkyl methacrylate at least in the first stage polymerization, the latex was stabilized, scale generation was significantly suppressed, and polymer production was improved. It was found that there was no problem. Similar to the previous Japanese Patent Application No. 51-141475 (see Japanese Patent Publication No. 57-39252), the method according to the present invention can significantly reduce the amount of residual monomer, and at the same time achieve a significantly high conversion rate using the patch method, which is useful for polymer production. A resin that has no problems and has excellent impact resistance.
The above-mentioned Special Publication No. 33574 or Special Publication No. 1973-
Simply add a highly polymerizable monomer as described in No. 16347 to the polymerization system without any operational or equipment complexity such as keeping the monomer composition constant in the polymerization system. The authors have discovered a method that can be produced by keeping the amount of monomers low, and this method has important significance as a method that can be implemented on an industrial scale from an economic standpoint. The method of the present invention is 1,3
(1) 45 to 90% by weight of acrylonitrile in the presence of a diene rubber latex consisting of 50% by weight or more of a conjugated diene and 50% by weight or less of at least one monomer copolymerizable with the diene rubber latex; A first stage monomer mixture consisting of 30 to 8% by weight of one type of aromatic vinyl compound and 2 to 25% by weight of at least one type of alkyl acrylate or alkyl methacrylate is added to the monomer mixture in the polymerization system. The polymerization is allowed to proceed while continuously adding at a rate such that the amount is always kept below 5% by weight, and immediately after the addition of the first stage monomer mixture, (2) 0 to 50% by weight of acrylonitrile is added at least. 0 to 100% by weight of one type of aromatic vinyl compound
and 5 to 25 parts by weight of a second stage monomer mixture consisting of 0 to 100% by weight of at least one alkyl acrylate or alkyl methacrylate (the mixture of the first stage monomer and the second stage monomer) (with a total weight of 100 parts by weight) was added continuously at a rate such that the monomer in the polymerization system did not exceed 5% by weight, and the conversion rate at the end of the second stage addition was 90%.
% or more, and furthermore, by finally completing the polymerization at a conversion rate of 95% or more, and substantially including 5 to 25% by weight of diene rubber in the resin,
The desired nitrile resin with extremely low residual monomer content can be advantageously produced industrially. When continuously adding the first-stage monomer mixture in the presence of diene rubber latex, the rate is such that the amount of the monomer mixture present in the polymerization system is always kept at 5% by weight or less based on the polymerization system. This is extremely important in the structure of the present invention. That is, by constantly adding the first-stage monomer mixture to the polymerization system, polymerization can be carried out while preventing the formation of polyacrylonitrile within the system. The amount of the monomer mixture present in the polymerization system is always kept at 5% by weight or less, the lower of which is preferred, but the amount of monomer after the addition of the first stage monomer mixture is preferably 3% by weight or less. preferable. Further, the monomer amount at the final stage of polymerization is more preferably 1% by weight or less. Diene rubber latex is an emulsion copolymerization latex consisting of 50% by weight or more of 1,3-diene monomer and at least one monomer copolymerizable with this. Examples of 1,3-diene monomers include butadiene, isoprene, and chloroprene. 1,3
- Monomers copolymerizable with diene monomers include:
Examples include styrene, substituted styrene, α-methylstyrene, substituted α-methylstyrene, acrylonitrile, alkyl acrylates or alkyl methacrylates having alkyl groups such as methyl, ethyl, propyl, and n-butyl. A crosslinked structure may be imparted to the diene rubber by copolymerizing a polyfunctional monomer such as divinylbenzene or polyethylene glycol dimethacrylate. The 1,3-diene monomer content of the diene rubber must be 50% by weight or more. When it is less than 50% by weight, the glass transition temperature of the rubber becomes high and the reinforcing effect on the resin becomes low. The average particle diameter of the diene rubber latex is preferably in the range of 0.03 to 0.15 μm if transparency is required, but is not particularly limited. If the acrylonitrile content of the first stage monomer is high, the gas barrier properties of the resin can be increased, but processability and thermal stability are reduced. Therefore, a range of 45 to 90% by weight is appropriate. Examples of aromatic vinyl compounds include styrene, substituted styrene, α-methylstyrene, and substituted α-methylstyrene, and examples of alkyl acrylates and alkyl methacrylates include those having substituents such as methyl, ethyl, propyl, and butyl. . The monomers remaining in the polymerization system at the end of the first stage polymerization mainly exist dissolved in water. Second
The monomer in the step further reduces this residual monomer,
It is added to achieve a high conversion rate. The second stage monomer mixture is acrylonitrile 0
50% to 50% by weight, 0 to 100% by weight of aromatic vinyl, and 0 to 100% by weight of at least one alkyl acrylate or alkyl methacrylate. The polymer conversion rate at the end of the addition of the monomer mixture in the second stage polymerization must be 90% or more.
In addition, the final conversion rate must be 95% or more.
Especially when the conversion rate is 97% or more, the amount of residual monomer in the product can be made extremely small. The second stage monomer mixture needs to be in the range of 5 to 25 parts by weight when the sum of the first stage monomer mixture and the second stage monomer mixture is 100 parts by weight. If the amount is less than 5 parts by weight, when attempting to achieve a high conversion rate of 95% or more, the acrylonitrile dissolved in water will polymerize to produce polyacrylonitrile, making the polymerization system unstable. On the other hand, if the amount is 25 parts by weight or more, a large amount of a copolymer rich in aromatic vinyl compounds and/or alkyl acrylates or alkyl methacrylates will be produced, resulting in a decrease in impact resistance, which is not preferable. Adjustment of the polymerization rate is important in this method, but it can be easily adjusted by adjusting the polymerization temperature and the type and amount of the polymerization initiator. The amount of diene rubber latex added during polymerization is determined by the balance between impact resistance and gas barrier properties, but good properties are imparted when the resin contains 5 to 25% by weight. If it is less than 5% by weight, the impact resistance will decrease, while if it is more than 25% by weight, the gas barrier properties will decrease. Polymerization is carried out by a conventional emulsion polymerization method, and the amount of water is 100 parts by weight or more, preferably 100 to 300 parts by weight, based on 100 parts by weight of the total amount of monomers charged in the polymerization system. It is advantageous in terms of removal and economy. Emulsifiers, polymerization initiators, and the like that are commonly used are used. For example, emulsifiers include dialkyl sulfosuccinate soda salts,
Examples include sodium alkylbenzenesulfonate and sodium condensed naphthalenesulfonate. Examples of the polymerization initiator include organic peroxides such as benzoyl peroxide and cumene hydroperoxide, azo initiators such as azobisisoputyronitrile, and persulfates. There are no particular restrictions on the polymerization temperature, but in industrial implementation it is advantageous to carry out the polymerization in the range of 10°C to 90°C. The polymer obtained by the above method is coagulated with an inorganic salt or acid, then subjected to heat treatment if desired, washed with water, and dried to obtain a powdered resin. During or after these steps, pigments,
Additives such as heat stabilizers and lubricants can also be blended. The resin obtained by the method of the present invention has very little monomer remaining in the resin even after the above-mentioned conventional post-treatment method. This is because the system is constantly maintained at a high conversion rate during the polymerization process, so that the amount of monomer in the polymer latex particles is always extremely small. The nitrile resin obtained by this method can be molded by conventional molding methods such as extrusion molding, injection molding, blow molding, calendar molding, compression molding, etc., and has high gas barrier properties and impact resistance. The present invention provides a material useful as a plastic resin for packaging materials, especially food packaging materials. The following examples illustrate the method of the invention. Example 1 A Production of diene rubber latex 1,3-butadiene 77 parts by weight Styrene 23 Triethylene glycol dimethacrylate
1.2 〃 t-dodecyl mercaptan 0.25 〃 Semi-hardened beef tallow soda soap 2.0 〃 Hydrogenated potassium rosinate 1.0 〃 Condensed sodium naphthalene sulfonate
0.2 〃 Ethylenediaminetetraacetic acid disodium
0.002 〃 Ferrous sulfate heptahydrate 0.001 〃 Formaldehyde sodium sulfite condensate
0.1 〃 Paramenthane hydroperoxide
0.1 〃 Deionized water 200 〃 The above main and auxiliary raw materials were charged into a pressure-tight sealed polymerization vessel, and polymerization was carried out at 40°C for 10 hours while stirring and removing oxygen. As a result, the polymerization conversion rate of the monomer was 98
%, and the particle size of the latex was 0.06μ as measured by an electron microscope. B Production of nitrile resin Diene rubber latex
14 parts by weight (as solid content) GAFAC RE-610 (emulsifier) 1.5 parts by weight Disodium ethylenediaminetetraacetate
0.05 〃 Deionized water 200 〃 Potassium persulfate 0.15 〃 The above substances were placed in a polymerization container and kept at 60°C while stirring under a nitrogen stream, and the following first stage monomer was continuously added over 6 hours. . Acrylonitrile 6.05 parts by weight Styrene 15.8 Methyl methacrylate 4.7 N-dodecyl mercaptan 2.0 Immediately after the addition of the first stage monomers, the following second stage monomers were continuously added over one hour. The polymer conversion rate at the end of the first stage addition was 87%. Styrene 4.0 parts by weight Methyl methacrylate 1.0 〃 Conversion rate at the end of second stage monomer addition was 93.6%
The polymerization was continued for about 1 hour after the second stage monomer addition was completed. Final polymerization conversion rate is 97.5
It was %. After completion of polymerization, the polymer latex was cooled to below 50°C, coagulated with calcium chloride, heat-treated at 90°C, filtered, washed with water, and dried to obtain a powdered resin. Changes in unreacted monomers in the polymerization system during polymerization were calculated by taking several cc of latex samples at regular intervals, drying them, and measuring the solid weight of the latex. The results are shown in Table 1.

[Table] (However, parts by weight are based on 100 parts by weight of the total polymerization system at that time) Unreacted acrylonitrile contained in the dried resin powder was 8 ppm. This resin powder was kneaded with a heating roll and then compression molded to form a sheet with a thickness of 0.3 mm, which was used as a sample for measuring the physical properties. Parallel light transmittance and haze (JIS-K6714) Yellowness (JIS-K7103) were measured using an integrating sphere light transmittance measuring device and a colorimeter, and the parallel light transmittance was 90.2% and haze was 0.7. %, and the yellowness is
It was 7.8. Impact resistance strength was measured by placing the test piece freely on a support frame with a 0.9 mm hole, dropping a 0.9 mm diameter steel ball with a load of 500 g, and calculating the fracture height using the Dickson mode method. and calculated the average height. The result of this test was 18.7 cm. Gas permeability (ASTM-D-1434) was measured at 20°C and was 0.31×10 ^-11 cc. cm/cm ² seccmHg
It was hot. Example 2 The composition and addition time of the first stage monomer and second stage monomer were as shown below, the diene rubber latex was 10 parts by weight, and n-dodecyl mercaptan was 2.0 parts by weight. Polymerization was carried out in the same manner as in Example 1, except that 50% of the polymer was added in one batch at the beginning to obtain a resin powder. 1st stage monomer Continuous addition for 5 hours Acrylonitrile 63.4 parts by weight Styrene 16.6 〃 Methyl methacrylate 5.0 〃 2nd stage monomer Continuous addition for 1 hour Styrene 4.0 parts by weight Acrylonitrile 1.0 〃 Monotony at the end of 1st stage The conversion rate was 88.5%. The conversion rate at the end of the second stage addition was 93.5%, and the final conversion rate was 97.3%. Table 2 shows the change over time in the amount of unreacted monomer during polymerization.
The physical properties are shown in Table 3. Comparative Example 1 Polymerization was carried out in the same manner as in Example 1 except that the addition time of the first stage monomer was changed to 3 hours to obtain a resin powder. Table 2 shows the change over time in the amount of unreacted monomer during polymerization, and Table 3 shows the physical properties. The conversion rate at the end of the first stage addition was 72.5%, and the final conversion rate was 93.5%. However, at 2 hours of polymerization,
More than 5% by weight of unreacted monomer remains with respect to the polymerization system in the system, and the resulting product has low transmittance and impact resistance, and the acrylonitrile monomer in the product resin is
560ppm was also present. Comparative Example 2 The first stage polymerization in Example 1 was carried out for 6 hours, and immediately after the first stage monomer addition was completed, hydroquinone was added to stop the polymerization. The change over time in the amount of monomer in the polymerization system was the same as in Example 1, and the polymer conversion rate at the end of the polymerization was 85%. As shown in Table 3, the properties of the resin were the same as those obtained in Example 1, but the acrylonitrile content contained in the resin was extremely high at 860 ppm. Comparative Example 3 The first stage polymerization in Example 2 was carried out for 5 hours without adding methyl methacrylate, by continuously adding the first stage monomer for 5 hours, and using 67.5 parts by weight of acrylonitrile and 17.5 parts by weight of styrene. Stage monomer: Continuous addition for 1 hour Styrene: 4.0 parts by weight Acrylonitrile: 1.0%. The conversion rate at the end of the second stage monomer addition was 93.6%, but a large amount of scale was generated, and the polymerization system did not lose stability 3 hours after the end of the addition. Congealed. Changes over time and physical properties of unreacted monomers in the polymer are shown in Tables 2 and 3, and the residual monomers in the resin were extremely large at 430 ppm.

【table】

【table】

Claims (1)

[Scope of Claims] 1 Emulsion polymerization method in the presence of a diene rubber latex consisting of 50% by weight or more of a 1,3-conjugated diene and 50% by weight or less of at least one monomer copolymerizable with the diene. (1) A first stage monomer consisting of 45 to 90% by weight of acrylonitrile, 30 to 8% by weight of at least one aromatic vinyl compound, and 2 to 25% by weight of at least one alkyl acrylate or alkyl methacrylate. 95 to 75 parts by weight of the monomer mixture (assuming a total of 100 parts by weight of the first and second stage monomer mixtures) in such a way that the amount of the monomer mixture in the polymerization system is always kept at 5% by weight or less based on the polymerization system. (2) 0 to 50% by weight of acrylonitrile and 0 to 100% by weight of at least one aromatic vinyl compound. weight%
and at least one alkyl acrylate or alkyl methacrylate 0 to 100% by weight
5 to 25 parts by weight of the second-stage monomer mixture (assuming the total weight of the first-stage monomer and second-stage monomer mixture is 100 parts by weight), The polymerization is continuously added at a rate such that the amount of the polymer mixture does not exceed 5% by weight, and the conversion rate at the end of the second stage addition is 90% or more, and finally the polymerization is completed at a conversion rate of 95% or more. 5 in the resin.
A method for producing a high impact resistant nitrile resin having extremely low residual monomer content and having a high degree of gas barrier property, characterized by containing from 25% by weight of diene rubber. 2 The 1,3 diene monomer of the diene rubber is butadiene, isoprene or chloroprene, and the monomer copolymerizable with this is styrene, substituted styrene, α-methylstyrene, substituted α-methylstyrene, acrylonitrile, or The method for producing a high nitrile resin according to claim 1, which is a monomer mixture of one or more of alkyl acrylates and alkyl methacrylates. 3. Claim No. 3, wherein the aromatic vinyl compound of the monomer mixture in the first stage and second stage is one or a mixture of two or more of styrene, substituted styrene, α-methylstyrene, or substituted α-methylstyrene. A method for producing a high nitrile resin according to item 1. 4 Claims in which the alkyl acrylate or alkyl methacrylate of the monomer mixture in the first and second stages is one or a mixture of two or more of methyl, ethyl, propyl, butyl, or substituents. A method for producing a high nitrile resin according to item 1. 5. The method for producing a high nitrile resin according to claim 1, wherein the final polymerization conversion rate is 95% or more. 6 Residual monomers in the polymerization system may cause the first
The method for producing a high nitrile resin according to claim 1, wherein the amount is 5% by weight or less after the addition of the step monomer mixture is completed. 7 Residual monomers in the polymerization system may cause secondary damage to the polymerization system.
2. The method for producing a high nitrile resin according to claim 1, wherein the amount is 2% by weight or less at the end of polymerization after addition of the stage monomer mixture.