JPH0252924B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for producing a high nitrile polymer with improved impact resistance. More specifically, the present invention relates to an improvement in a method for polymerizing acrylonitrile and a monomer copolymerizable therewith in an aqueous medium in the presence of a conjugated diene synthetic rubber. [Prior Art] Rubber-reinforced high nitrile-containing resins have been developed in recent years because they are thermoplastic polymers that have impact resistance in addition to high gas and vapor barrier properties and excellent solvent resistance that high nitrile resins inherently have. It is attracting attention as a container and packaging material in food, agricultural medicines, cosmetics, and other fields. Regarding the production method of rubber-reinforced high nitrile-containing resin, various polymerization methods have been studied so far, and
A number of improved techniques have been demonstrated. For example, a method in which a monomer consisting of an unsaturated nitrile and an acrylic acid alkyl ester is polymerized by batch addition to a conjugated diene/nitrile copolymer rubber (Japanese Patent Publication No. 46-25005), A method of polymerizing nitrile and a monomer copolymerizable with it, pre-swelling the rubber with a part of the monomer, and continuously adding the remaining monomer (Japanese Patent Application Laid-open No. 75294/1983);
A method of polymerizing monomers consisting of nitrile and aromatic vinyl in the presence of a diene-based synthetic rubber by adding the monomers at a rate determined as a function of the polymerization temperature (Japanese Patent Laid-Open No. 1973- 22086) etc. [Problems to be solved by the invention] The type of polymerization in this technology is carried out in an aqueous medium because of the ease of reaction control due to the advantage of heat removal and the ease of post-treatment after polymerization. Emulsion polymerization method or suspension polymerization method is generally employed. Additionally, there are batch, continuous, and split methods for adding monomers for graft polymerization to rubber, but in the batch method, a large amount of monomer is added at once, resulting in a rapid reaction. It is difficult to remove the heat generated by polymerization, requiring an external cooler or frozen water, and it is difficult to make the composition of the polymer uniform due to the difference in reactivity between nitrile and the monomer copolymerizable with it. The drawback is that it is difficult to control. Therefore, in practical terms, it is advantageous to carry out polymerization while controlling the reaction by adjusting the amount of monomers added and adding them continuously or in portions. However, in polymerization by continuous or divided addition of monomers, the monomer concentration in the polymerization system is always diluted compared to batchwise polymerization, so various factors (monomer concentration, There were problems in that the amount of initiator, emulsifier, dispersant, polymerization temperature, etc. had a complex influence on polymerization, poor reproducibility of polymerization, and variations in quality from batch to batch. An object of the present invention is to solve this problem and provide a polymerization method capable of obtaining a nitrile polymer having excellent impact resistance with good reproducibility. [Means for Solving the Problems] As a result of extensive research, the present inventors have discovered a method of graft polymerizing a diene-based synthetic rubber by adding acrylonitrile and a monomer copolymerizable therewith in an aqueous medium. We discovered that it is necessary to use acrylonitrile in a specified amount or more relative to water at the start of polymerization in order to obtain the desired impact-resistant nitrile polymer with good reproducibility. The invention was completed. That is, in the present invention, in the presence of 1 to 40 parts by weight of a conjugated diene-based synthetic rubber consisting of 50% by weight or more of a conjugated diene monomer and 50% by weight or less of a monomer copolymerizable therewith, at least 50% by weight When polymerizing 100 parts by weight of a monomer mixture containing 100 parts of acrylonitrile in an aqueous medium by adding the monomers continuously or in portions, the acrylonitrile monomer at the polymerization initiation temperature increases in the polymerization system. This is a method for producing a high nitrile polymer, characterized in that the polymer is present at a level higher than its solubility in water. In the present invention, the impact-resistant nitrile polymer is obtained by graft polymerizing a large proportion of acrylonitrile and other monomer components copolymerizable with the same onto a preformed conjugated diene synthetic rubber. The monomers and, if necessary, other polymers are polymerized in an aqueous medium at a temperature of about 0 to 100°C with removal of oxygen by commonly known polymerization methods such as emulsion or suspension polymerization. Polymerization can be carried out by continuous or portionwise addition of the components. Preferred is an aqueous emulsion polymerization method in which monomers are added continuously or in portions. In the present invention, in the polymerization system at the time of polymerization initiation,
It is important that the amount of acrylonitrile used in water is at least equal to or greater than the saturated dissolution amount of acrylonitrile in water at the polymerization temperature, so that the grafting reaction of acrylonitrile to rubber proceeds in a stable manner. In addition, the desired high impact strength of the final polymer can be obtained with good reproducibility. As the conjugated diene monomer used in the present invention,
Examples include 1,3-butadiene, isoprene, and chloroprene, with 1,3-butadiene and isoprene being preferred from the viewpoint of ease of availability and polymerizability.
Furthermore, monomers copolymerizable with the conjugated diene monomer include unsaturated nitriles, unsaturated carboxylic acid esters, aromatic vinyl compounds, etc., and one or more of these may be used. Examples of unsaturated nitriles include acrylonitrile,
Examples include methacrylonitrile and α-chloroacrylonitrile, with acrylonitrile and methacrylonitrile being preferred. In addition, unsaturated carboxylic acid esters include methyl, ethyl, and acrylic acid or methacrylic acid.
Examples include esters such as propyl and butyl; particularly preferred are methyl acrylate,
They are ethyl acrylate, methyl methacrylate, and ethyl methacrylate. Examples of aromatic vinyl monomers include styrene, α-
Examples include methylstyrene, vinyltoluenes, vinylxylenes, etc., with styrene being preferred. Monomers to be grafted onto the rubber include acrylonitrile and monomers copolymerizable with it, such as unsaturated carboxylic acid esters, aromatic vinyl compounds,
A monomer consisting of one or more of vinyl esters, vinyl ethers, α-olefins, etc. Regarding the unsaturated carboxylic acid ester and the aromatic vinyl compound, those exemplified above can be used. Vinyl esters include vinyl acetate, vinyl propionate, vinyl lactate, etc.
Preferred is vinyl acetate. Examples of vinyl ethers include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ethers, butyl vinyl ethers, methyl isopropenyl ether, ethyl isopropenyl ether, and the most preferred are methyl vinyl ether, ethyl vinyl ether, propyl vinyl ethers, and butyl vinyl ether. They are vinyl ethers. α-olefins include isobutene, 2-methyl-1-butene, 2-methyl-1-pentene, 2
-Methyl-1-hexene, 2-methyl-1-heptene, 2-methyl-1-octene, 2-ethyl-
Examples include 1-butene and 2-propyl-1-butene. Most preferred is isobutene. The conjugated diene synthetic rubber useful in the present invention includes 50% by weight or more of a conjugated diene monomer, typically 1,3-butadiene, and a monomer copolymerizable therewith, such as 0% by weight or less of acrylonitrile. The composition is preferably 60 to 80% by weight of conjugated diene. In an aqueous medium, emulsifiers or dispersants, polymerization initiators, molecular weight regulators,
It is obtained by removing oxygen and polymerizing at a desired temperature in the presence of a PH regulator and other additives. The monomer and other addition methods may be batch, continuous, or divided. Emulsion or suspension polymerization is preferred as a method for polymerizing monomers mainly composed of unsaturated nitrile in the presence of the conjugated diene synthetic rubber previously produced by the above method. Polymerize with a polymerization initiator at a temperature of ~100°C. For the purpose of controlling the heat of the polymerization reaction and uniformizing the composition of the resulting polymer, it is preferable to add the monomer continuously or in portions. Further, if necessary, emulsifiers, dispersants, polymerization initiators, molecular weight regulators, PH regulators, and other additives may be added continuously or in portions. The amount of the conjugated diene synthetic rubber used is about 1 to 40 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the total monomer weight. In general, as the relative proportion of rubber components in the final polymer increases, impact strength increases, but gas and vapor barrier properties decrease somewhat, so the amount of rubber that provides the physical properties appropriate for the intended use is determined. Just use it. The content of acrylonitrile in the monomer mixture polymerized in the presence of rubber is at least 50% by weight, preferably of the order of 60-90% by weight. In the present invention, regarding the acrylonitrile/water ratio at the start of polymerization, for example, when emulsion polymerization is carried out at a polymerization temperature of 60°C, the saturated solubility of acrylonitrile in water at 60°C is approximately 9wt.
%, it is necessary to set the ratio of acrylonitrile to water at the start of polymerization so that it is at least 9 wt % or more based on water. Considering the solubilization of acrylonitrile in the emulsifier, etc., it is preferably 11 wt% or more based on water in normal emulsion polymerization, although it depends on the amount of emulsifier used. If polymerization is carried out using the above method of the present invention, a nitrile thermoplastic monomer having high impact strength can be produced.
Monomers can be obtained stably without variations from batch to batch, but monomers obtained when the amount of acrylonitrile dissolved in water is less than the saturated amount have large variations between batches in terms of impact resistance, and are generally monomers with low impact strength. Only quantities can be obtained. When polymerizing monomers in the presence of rubber, usable polymerization initiators (or catalysts) include peracid catalysts such as persulfuric acid, peracetic acid, and perphthalic acid, and peroxyacid catalysts such as potassium persulfate. Acid salt catalyst, hydrogen peroxide, benzoyl peroxide, chlorbenzoyl peroxide, brobenzoyl peroxide, naphthyl peroxide, acetyl peroxide, benzoylacetyl peroxide, lauryl peroxide, succinyl peroxide, di-t-butyl peroxide ,
dicumyl peroxide, cumyl hydroperoxide, peracetic acid t
- Peroxide catalysts such as butyl, sodium peroxide, and barium peroxide, alkyl hydroperoxides such as t-butyl hydroperoxide, and azo catalysts such as azobisisobutyronitrile, which may be used alone or in combination. A mixture of the above can be used. The preferred polymerization method in the present invention is an aqueous emulsion polymerization method, and emulsifiers that can be used include sodium and potassium salts of myristic acid, lauric acid, palmitic acid, oleic acid, stearic acid, lauryl sulfate, cetyl sulfate, oleyl sulfate, etc. fonic acid,
Examples include sodium, potassium, and ammonium salts such as stearyl sulfonic acid and sulfated castor oil, higher amine salts such as laurylamine hydrochloride and stearylamine hydrobromide, and polymeric substances such as polyvinylpyrrolidone, sodium polyacrylate, and methylcellulose. The polymer product is obtained in the form of a latex, and the polymer is coagulated by a conventionally known method, such as a coagulation method using an electrolyte or a solvent, or a freezing method, and then washed with water and dried to obtain a polymer. It is also possible to add plasticizers, stabilizers, lubricants, dyes and pigments, fillers, etc. during or after the polymerization, if necessary. The polymer produced by the method of the present invention is a thermoplastic resin that can be easily thermoformed by conventional molding methods using known thermoplastic materials, such as extrusion molding, injection molding, blow molding, etc. It has high gas barrier properties, excellent solvent resistance, and excellent impact resistance, making it particularly useful as a packaging container material for bottles, films, and other types of liquids and solids. [Example] The present invention will be explained below with reference to Examples. All "parts" and "%" in the examples are based on weight. Example 1 (A) Production of conjugated diene rubber latex A mixture consisting of the following components was placed in a stainless steel polymerization reactor to remove oxygen and polymerized at 45° C. for 20 hours with stirring. Acrylonitrile 40 parts Butadiene-1,3 60〃 Fatty acid soap 2.4〃 Azobisisobutyronitrile 0.3〃 t-Dodecyl mercaptan 0.5〃 Water 200〃 The monomer conversion rate is 90%, and the solid content concentration of the latex is 30 It was %. (B) Production of graft polymer The total amount of main and auxiliary raw materials including the rubber latex obtained in A above is as follows. Water 235 parts Acrylonitrile 70 Methyl acrylate 30 Latex of A above 33 (solid content 10 parts) Sodium dioctysulfosuccinate 1.0 parts Polyvinylpyrrolidone 0.4 Potassium persulfate 0.06 n-dodecyl mercaptan 1.0 First, polymerization reaction Put the following main and sub-ingredients into a container,
After removing oxygen, polymerization was started at 60°C with stirring. Initial charge water 127 parts Acrylonitrile 14〃 (9.3% to water) Methyl acrylate 6 parts Latex of A above 33〃 Sodium dioctyl sulfosuccinate 0.2〃 Polyvinylpyrrolidone 0.08〃 Potassium persulfate 0.06〃 Thirty minutes after the start of polymerization, the remaining Polymerization was continued at 60° C. while continuously adding the following main and auxiliary raw materials over a period of 5 hours. Continuous additive composition Water 108 parts Acrylonitrile 56〃 Methyl acrylate 24〃 Sodium dioctyl sulfosuccinate 0.8〃 Polyvinylpyrrolidone 0.32〃 n-Dodecyl mercaptan 1.6〃 After addition of the above raw materials, polymerization was continued for another 1 hour to form monomers. The conversion rate was set at 90%. The obtained latex was coagulated with an aqueous aluminum sulfate solution,
A powdered polymer was obtained by washing with water and drying. When this polymer was pressure-molded at 170°C and 140 kg/cm ² , a transparent, pale yellow sheet was obtained. A test piece was created from this sheet, and according to ASTM D256,
The notched isot impact value was measured at 23°C and a load of 3.828 kg. In addition, in order to examine the processability of the polymer, the flow rate was measured at 200°C and a load of 12.5 kg using a melt indexer according to ASTM D1238.
The measurement results are shown in Table 1. Examples 2 to 3 Comparative Examples 1 and 2 In Example 1B, the initial amount of water was changed without changing the total water consumption of 235 parts, and the acrylonitrile/water ratio was 15%, 20%, and 7%, respectively. Polymerization was carried out in the same manner as in Example 1 except that % and 8% were used, and the physical properties of the obtained polymer were measured. Table 1 shows the results.

【table】

〔Effect of the invention〕

As seen in the method of the present invention, in a method in which monomers are polymerized by continuous or divided addition, the acrylonitrile/water ratio at the start of polymerization is higher than the solubility of acrylonitrile in water at the polymerization temperature. In this case, the resulting polymer has excellent impact resistance and stable high impact strength.

Claims (1)

[Claims] 1. In the presence of 1 to 40 parts by weight of a conjugated diene synthetic rubber consisting of 50% by weight or more of a conjugated diene monomer and 50% by weight or less of a monomer copolymerizable with this, at least 50% by weight
Monomer mixture containing wt% acrylonitrile
When polymerizing by adding 100 parts by weight of the monomer in an aqueous medium in a continuous or divided manner, the acrylonitrile monomer must be present at a level higher than its solubility in water in the polymerization system at the polymerization initiation temperature. A method for producing a high nitrile polymer characterized by: