JPH0242361B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is a solution polymerization method for acrylonitrile (hereinafter abbreviated as AN) polymer, which is particularly useful as a raw material for producing fibers and films with good physical properties, and has excellent moldability. This invention relates to a method for polymerizing a high degree of polymerization AN polymer. [Prior Art] Conventionally, a method for producing a polymer solution containing AN as a main component involves suspending or emulsifying monomers such as AN and its copolymer components such as various unsaturated vinyl compounds in an aqueous medium. Polymerize and filter the obtained polymer,
After performing operations such as washing with water, granulation, drying, and pulverization,
A known method is to dissolve the polymer in a solvent, or to omit the above-mentioned granulation and subsequent operations, add a solvent after filtration and water washing, and heat under reduced pressure to mainly evaporate water to form a polymer solution. . On the other hand, a method is also known in which the monomer is solution-polymerized in a polymer solvent to directly form a polymer solution. [Problems to be Solved by the Invention] However, in aqueous polymerization methods such as suspension or emulsion polymerization, the polymerization reaction is easily affected by dissolved oxygen and impurities, which makes the reaction unstable.
Sometimes, a runaway reaction may occur due to abnormal precipitation of slurry. In addition, as the degree of polymerization increases, the polymer becomes less soluble in solvents, so it takes a long time and high temperature to dissolve the polymer, which inevitably causes deterioration of the polymer and increases energy costs. , and is unfavorable from an economic point of view, such as a decrease in productivity. Furthermore, the amount of dispersant or emulsifier used is large (1 to 50 parts) per monomer (100 parts), and the dispersant or emulsifier can be completely removed even after multiple steps such as polymer coagulation, filtration, and water washing. There were problems such as difficulty in obtaining a clean polymer solution. On the other hand, the solution polymerization method does not have the same problems as the water-based polymerization mentioned above, but it depends on the monomer concentration, type of solvent, reaction time, etc., and in some cases, the type and amount of polymerization initiator added. Not only is the degree of polymerization greatly affected, but when attempting to obtain a polymer with a high degree of polymerization, there is a risk of solidification of the polymerization system or even abnormal explosion due to abnormal reactions. That is, an object of the present invention is to solve the problems of the above-mentioned conventional techniques and to provide a method for solution polymerizing AN-based polymers with a higher degree of polymerization. Another object of the present invention is to provide a clean AN-based polymer solution with a high degree of polymerization that has excellent fiber-forming properties and film-forming properties. [Means for solving the problem] The above problem of the present invention is to solve the problem by using AN alone or 93 mol%
The above AN and at least 7 mol% or less of at least one unsaturated vinyl compound copolymerizable with the AN are dissolved in an organic solvent such that the concentration of these monomers is in the range of 10 to 22% by weight. Polymerization is carried out in the presence of a polymerization initiator until a polymerization rate of 5 to 85% is reached, after which unreacted monomers are evaporated and removed, resulting in a polymer concentration of 5 to 18% by weight and an intrinsic viscosity of 5 to 85%. This problem can be solved by forming a polymer solution in which the ratio is 2.5 or more. In other words, the gist of the present invention is the concentration of monomers mainly consisting of AN in the solution polymerization of AN-based polymers, the type of solvent, the polymerization rate, the evaporation removal of unreacted monomers, the intrinsic viscosity of the polymer, and the final This indivisible relationship allows for stable AN-based polymer solutions with a high degree of polymerization that can be easily molded into high-quality fibers and films. You can get it. First, in the solution polymerization of the present invention, the concentration of monomers such as AN alone or 93 mol% or more of AN and at least one unsaturated vinyl compound copolymerizable with the AN is 7 mol% or less. A range of ~22% by weight is required. When this concentration is lower than 10% by weight, the degree of polymerization of the obtained polymer is low;
For example, it becomes difficult to obtain a polymer with an ultimate concentration of 2.5 or higher. On the other hand, if it exceeds 22% by weight, the polymerization reaction becomes unstable and there is a risk of runaway reactions. In the present invention, organic solvents include, for example, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), and dimethylacetamide (DMAC).
and dimethylurea. however,
For solution polymerization of high polymerization degree AN-based polymers, it is preferable to use a solvent with a chain transfer constant as small as possible, and therefore, among the above-mentioned solvents, it is particularly desirable to use DMSO. Preferred polymerization initiators used in the present invention include, for example, octanoyl peroxide, decanoyl peroxide, lauroyl peroxide, hydrogen peroxide, azobisisobutyronitrile (AIBN), and azobisdimethylvaleronitrile (ADVN). For example, azo polymerization initiators such as AIBN and ADVN are particularly desirable from the viewpoint of polymerization stability. The amount of this polymerization initiator used is preferably as the concentration of the polymerization system.
It is within the range of 0.001 to 0.02% by weight. This concentration
If it is less than 0.001% by weight, the polymerization rate is insufficient, if it is more than 0.02% by weight, it will be difficult to obtain a polymer with a high degree of polymerization, and if the polymerization rate is too high, it will be difficult to control the polymerization reaction. There is. Next, in the solution polymerization of the present invention, after starting the polymerization under the above conditions, it is important to control the reaction so that the polymerization rate is within the range of 5 to 85%, preferably 20 to 65%. be. This polymerization rate is 5
If it is less than 85%, the burden of recovering unreacted monomers in subsequent steps will increase, causing problems in terms of productivity as an industrial polymerization method.On the other hand, if it exceeds 85%, the resulting It becomes difficult to increase the polymerization degree of the coalescence, and for example, it becomes extremely difficult to obtain a polymer with an intrinsic viscosity exceeding 2.5. After the polymerization system reaches the above polymerization rate, in the present invention, unreacted monomers are removed by evaporation, and the concentration of the polymer is reduced to 5 to 18% by weight, preferably 8 to 15% by weight.
It is necessary to keep it within the range of . That is, if the polymer concentration of the obtained polymer solution exceeds 18% by weight, the viscosity of the polymer solution increases significantly, resulting in poor moldability, that is, fiber forming ability and film forming ability. On the other hand, if the amount is less than 5% by weight, a problem arises in that the physical properties of the fibers and films of molded products obtained from this polymer solution are not sufficiently improved. The intrinsic viscosity of the AN-based polymer in the present invention is determined from Journal of Polymer Science (A-1) No. 6.
This value was measured at 30°C using dimethylformamide as a solvent according to the measurement method described in Vol., pp. 147-157 (1968). [Example] Hereinafter, the present invention will be specifically explained with reference to Examples. In addition, in the solution polymerization of the present invention, even when AN alone as a monomer or a copolymerization component is added simultaneously with AN, if the amount exceeds 5 mol%, it is difficult to produce a polymer with a high degree of polymerization. . Therefore, the obtained AN alone or AN at least 93
It is a copolymer whose main component is AN and contains 7 mol% or less of the copolymerized component. Moreover, parts in this example are parts by weight. Example 1 20.0 parts of AN, 1.4 parts of methyl acrylate,
Dissolved in 78.6 parts of DMSO, charged into a glass reaction vessel equipped with a stirring blade, thermometer, nitrogen inlet and air outlet, added 0.002 part of ADVN, and stirred in a nitrogen atmosphere for 60 minutes.
The reaction was carried out at ℃ for 6 hours. The polymerization reaction proceeded in a homogeneous solution system, and the polymerization rate reached 65%. Polymerization solution at 60℃
600 poise, and the intrinsic viscosity of the polymer was 3.0. Unreacted monomers were evaporated from this polymerization solution at 20 Torr.70°C, and the intrinsic viscosity was 3.0 and the polymer concentration was 15% by weight.
A 1000 poise polymer solution was obtained at 70°C. Using this solution as a spinning stock solution, wet-dry spinning was carried out in a 50% DMSO aqueous solution, stretched five times in hot water, and then washed with water and dried for densification. This dried densified yarn was stretched three times in hot air at 200°C. The spinning properties were good and stable production was possible. The tensile strength of the obtained fiber was 14 g/d, and the initial ratio was
AN-based fibers with extremely high strength and high elastic modulus of 220 g/d were obtained. This AN-based fiber has a tensile strength that significantly exceeds the tensile strength of commercially available AN-based fibers, approximately 4 g/d, and as a result of investigation into cement reinforcement applications, it has been found to have a reinforcing strength approximately seven times that of asbestos, which has carcinogenic properties. It was confirmed that it is an industrially useful material as an asbestos substitute fiber. Example 2 20.7 parts of AN and 0.3 parts of acrylic acid were dissolved in 79 parts of DMSO and charged into the same reaction vessel as in Example 1.
Added 0.006 parts of AIBN, 12 at 60℃ in nitrogen atmosphere
Allowed time to react. The polymerization reaction proceeded in a homogeneous solution system, the polymerization rate was 45%, the viscosity of the polymerization solution was 550 poise at 60°C, and the intrinsic viscosity of the polymer was 5.0. Unreacted monomers were evaporated from this polymerization solution to obtain a polymer solution with an intrinsic viscosity of 5.0, a polymer concentration of 11% by weight, and a temperature of 2500 poise at 70°C. This solution showed good and stable moldability (thread-spinning property) and could be molded into fibers or films as is. Example 3 18.1 parts of AN was dissolved in 81.9 parts of DMSO and charged into the same reaction vessel as in Example 1, 0.007 parts of ADVN was added, and the mixture was reacted for 24 hours at 40°C in a nitrogen atmosphere.
The polymerization reaction proceeds in a homogeneous solution system, and the polymerization rate is 30%.
The viscosity of the polymerization solution was 100 poise at 40°C, and the intrinsic viscosity of the polymer was 8.0. Unreacted monomers were evaporated to obtain a polymer solution with an intrinsic viscosity of 8.0, a polymer concentration of 8% by weight, and a temperature of 7000 poise at 70°C. This solution showed good and stable moldability (thread-spinning property) and could be molded into fibers or films as is. Comparative Example 1 Using the same reaction vessel as in Examples 1 to 3, the first
Table 2 shows the results of a reaction at 60° C. in a nitrogen atmosphere using the feed composition shown in the table. In No. 1, the viscosity of the polymer solution was low, and the polymer concentration was too low even after evaporation of unreacted monomers, resulting in poor moldability. In No. 2, the polymer solidified during the reaction and could not be handled. In No. 3, the reaction did not proceed sufficiently,
In Nos. 4 and 5, the intrinsic viscosity of the polymer was low, and it was not possible to obtain a high polymerization degree AN polymer as the object of the present invention.

【table】

【table】

[Table] [Effects of the invention] According to the solution polymerization method of the present invention, the degree of polymerization of the AN-based polymer is extremely high, that is, when expressed in terms of intrinsic viscosity, it is 2.5 or more, preferably 2.5 to 10, more preferably 2.5 to 5. An AN-based polymer with a high degree of polymerization is obtained. Moreover, this AN-based polymer is clean and has excellent moldability, so the fibers and films made from it have even better strength properties, thermal stability, and
The effects of the present invention are remarkable, such as weather resistance.

Claims (1)

[Scope of Claims] 1. Acrylonitrile alone or 93 mol% or more of acrylonitrile and at least 7 mol% or less of at least one unsaturated vinyl compound copolymerizable with the acrylonitrile at a concentration of these monomers.
Dissolve the monomer in an organic solvent to a concentration of 10 to 22% by weight, polymerize in the presence of a polymerization initiator until a polymerization rate of 5 to 85% is reached, and then evaporate unreacted monomers.
1. A method for solution polymerizing an acrylonitrile polymer, the method comprising removing the acrylonitrile polymer to form a polymer solution having a polymer concentration of 5 to 18% by weight and an intrinsic viscosity of 2.5 or more. 2 The polymerization initiator is an azo compound, and the amount used is
A method for solution polymerizing an acrylonitrile polymer according to claim 1, wherein the amount is 0.001 to 0.02% by weight. 3. The solution polymerization method for an acrylonitrile polymer according to claim 1 or 2, wherein the organic solvent is dimethyl sulfoxide.