JPH0549687B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for producing a vinyl chloride polymer while producing a catalyst in a polymerization vessel. Generally, when vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable with it is polymerized, organic peroxides such as diacyl peroxide, dialkyl peroxide, peroxy ester, and dialkyl peroxydicarbonate are often used as polymerization initiators. ing. Among them, dialkyl peroxydicarbonates in particular have high low-temperature activity and excellent productivity, and the obtained polymers have excellent physical properties such as thermal stability, gelling properties during processing, and particle size distribution, and are suitable for industrial use. is recognized as the most advantageous polymerization initiator. However, as the low-temperature activity of these organic peroxides increases, they become unstable at room temperature, increasing the risk of explosion. Therefore, dedicated refrigeration equipment is required for storage, and even if such equipment were provided, handling during actual use would be dangerous. To avoid this problem, i.e. instead of using an organic peroxide polymerization initiator, an alkyl chloroformate, an inorganic peroxide and an alkali such as an alkali metal hydroxide or hydrogen carbonate can be added simultaneously to the polymerization vessel. The method of polymerizing vinyl chloride while producing peroxydicarbonate is
For example, it has been proposed in US Pat. No. 3,022,281, Japanese Patent Publication No. 56-5242, etc. However, the polymers produced by this method have quality defects such as extremely irregular particle morphology and poor thermal stability and gelling properties, so they have no commercial value and are difficult to commercially implement. It was hot. As a result of intensive research in order to overcome the above-mentioned drawbacks, the present inventors surprisingly found that by using ammonia as the alkali and keeping the oxygen concentration within the polymerization system below a specific value before the start of polymerization, they were able to achieve an extremely The inventors have discovered that it is possible to produce high quality polymers and have completed the present invention. An object of the present invention is to provide an improved method for polymerizing vinyl chloride and the like while producing a polymerization initiator in a polymerization vessel. Therefore, the gist of the present invention is to polymerize vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable therewith in the presence of an alkyl halogenoformate, an inorganic peroxide, and an alkali, using ammonia as the alkali. A method for producing a vinyl chloride polymer, characterized in that the oxygen concentration in the polymerization system before the start of polymerization is 100 ppm or less based on all monomers. The present invention will be explained in detail below. The vinyl chloride polymer produced by the method of the present invention is a copolymer obtained by copolymerizing a homopolymer of vinyl chloride and a mixture of vinyl chloride and a monomer copolymerizable therewith. . Examples of monomers that can be copolymerized with vinyl chloride include ethylene,
Vinyl esters or allyl esters such as propylene, butene, pentene-1, butadiene, styrene, α-methylstyrene, acetic acid, caproic acid, caprylic acid, benzoic acid, and alkyl groups with 1 to 12 carbon atoms (C _{1 to 12} ) dialkyl maleic acid or fumaric acid esters, acrylonitrile, vinylidene chloride, vinylidene cyanide,
Alkyl vinyl ether of C _1-12 alkyl group,
Examples include N-vinylpyrrolidone, vinylpyridine, vinylsilanes, alkyl esters of alkali acids with C _{1 to 16} alkyl groups, or alkyl methacrylates, and at least one of these is added in an amount of 40 parts by weight per 100 parts by weight of vinyl chloride. The copolymerization can be carried out preferably in an amount of 30 parts by weight or less. The alkyl halogenoformate used in the method of the present invention is represented by the following general formula. [In the formula, R represents an alkyl group which may have a branched chain, and X represents a chlorine atom, a bromine atom, or a fluorine atom, respectively. ] The alkyl group R preferably has 1 to 8 carbon atoms, and the halogen atom X is generally a chlorine atom. Examples of the alkyl halogenoformate include methyl chloroformate (methyl chloroformate), ethyl chloroformate, n-propyl chloroformate, isopropyl chloroformate, n-butyl chloroformate, isobutyl chloroformate, sec
-butyl chloroformate, tert-butyl chloroformate, n-amyl chloroformate, isoamyl chloroformate, n-hexyl chloroformate, n-heptyl chloroformate, n-octyl chloroformate, 2
-Ethylhexylchloroformate and the like. However, it is not limited to these. Therefore, the amount of alkyl halogenoformate used is
Although it varies depending on the amount of inorganic peroxide or ammonia used, which will be described later, in order to complete the polymerization reaction, it is necessary to use at least 0.01 part by weight per 100 parts by weight of monomer, especially
It is preferable to use it in a range of 0.01 to 1 part by weight. 1
When using an amount of more than 1 part by weight, the polymerization reaction is likely to be difficult to control and the quality of the polymer is likely to deteriorate, so care must be taken. The inorganic peroxide used in the method of the present invention is not particularly limited as long as it reacts with the aforementioned alkyl halide formate and ammonia to produce dialkyl peroxydicarbonate, but examples include hydrogen peroxide, sodium peroxide, Potassium peroxide, barium peroxide, magnesium peroxide, sodium hydrogen peroxide are mentioned, and hydrogen peroxide (e.g. Na ₂ SiO ₃ .H ₂ O ₂ .H ₂ O, NaBO ₃ .
H ₂ O ₂ , 3H ₂ O, etc.) can also be used. Among these, it is particularly preferable to use hydrogen peroxide since no impurities are mixed in during the polymerization process. The concentration of hydrogen peroxide is not particularly limited as long as it is a commonly available aqueous solution, but a concentration of 30 to 35% is desirable for ease of handling and to reduce the introduction of excess water into the polymerization system. . Therefore, the amount of hydrogen peroxide used is preferably 0.1 to 5 moles per mole of the alkyl halogenoformate used. In addition, the ammonia used in the method of the present invention can be obtained by blowing ammonia gas into water present in the polymerization system,
Ammonia in any state can be used, such as commercially available ammonia water. The amount of ammonia used is per mole of alkyl halide formate.
A range of 0.2 to 10 moles is desirable. When the amount of inorganic peroxide and ammonia used is less than the above-mentioned ratio, the conversion to dialkyl peroxydicarbonate, which acts as a polymerization initiator, is insufficient; Most of the oxides and ammonia remain in the polymerization system without participating in the reaction, which is not only economically disadvantageous but also tends to cause a decrease in the quality of the polymer. In the method of the present invention, alkyl halogenoformate,
The timing and order of addition of the inorganic peroxide and ammonia to the polymerization system are not particularly limited. Since these three polymerization initiator systems function as polymerization initiators only when they coexist, it is also possible to first introduce the two components into the polymerization system and then introduce the remaining components immediately before the start of polymerization. In the method of the present invention, it is essential that the oxygen concentration in the polymerization system at the start of polymerization be 100 ppm or less relative to the vinyl chloride monomer or copolymerizable monomer. The oxygen concentration in the polymerization system can vary depending on the degassing conditions, but under normal degassing conditions it is at most
It only decreases to about 100ppm. As a method for further reducing the amount of oxygen, various methods can be employed, such as increasing the temperature during degassing, increasing the number of repetitions of degassing and pressure return with nitrogen gas, or a combination thereof. If polymerization is carried out at an oxygen concentration of more than 100 ppm, the resulting polymer tends to have poor thermal stability. To carry out the method of the present invention, for example, water containing a suspending agent or emulsifying agent is placed in a polymerization container, and the oxygen concentration in the container is determined from within the container by the method described above.
100 ppm or less, add vinyl chloride or a monomer copolymerizable with it, then press-inject alkyl halide formate, inorganic peroxide, and ammonia, and carry out suspension or emulsion polymerization at a temperature of 30 to 70°C. conduct. The method of the present invention is most suitably employed in suspension polymerization. Suspending agents used in the method of the present invention are not particularly limited, but include partially saponified polyvinyl alcohol, hydroxypropyl methylcellulose, vinyl acetate-maleic anhydride copolymer,
Water-soluble polymeric substances such as polyvinylpyrrolidone and gelatin can be used alone or in combination. In addition, as emulsifiers, sorbitan monolaurate, sorbitan monostearate, sorbitan monooleate, or their polyoxyethylene derivatives, nonionic surfactants such as pentaerythritol monolaurate, pentaerythritol monooleate, sodium dodecylbenzenesulfonate, etc. , anionic surfactants such as sodium lauryl sulfate, and the like. These suspending agents and emulsifying agents can be used in combination. In addition to the above-mentioned polymerization initiator system, the method of the present invention may also be carried out using conventional polymerization initiators such as dialkyl peroxides, diacyl peroxides, alkyl peroxy esters, dialkyl peroxy dicarbonates, etc., if necessary. Organic peroxides such as or azonitrile compounds may be used in combination. When a polymerization initiator is used in combination, favorable results can often be obtained by adjusting the polymerization rate. In the method of the present invention, dialkyl peroxydicarbonate is produced from an alkyl halide formate present in a monomer such as vinyl chloride and an inorganic peroxide present in an aqueous medium, and by-product hydrogen halide etc. are produced in an aqueous medium. trapped by the ammonia present therein, forming a suitable polymerization initiation catalyst system. According to the present invention, there is no need for special refrigeration equipment associated with using dialkyl peroxydicarbonate as a polymerization initiator, there is no danger during handling, and moreover, dialkyl peroxydicarbonate is used as a polymerization initiator. A high-quality vinyl chloride polymer that is exactly the same as the original product can be obtained. The method of the present invention will be explained in detail below using examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Example 1 After charging 110 g of partially saponified polyvinyl acetate and 165 g of deionized water into a stainless steel polymerization vessel with an internal volume of 300 mm, the inside of the polymerization system was degassed, and finally the internal pressure of the polymerization vessel was reduced to 0 (gauge pressure) using _N2. ) was pressed back until it slightly exceeded. The amount of residual oxygen in the polymerization vessel is determined by gas chromatography for gas sampled from the top nozzle of the polymerization vessel for the gas phase, and by the Winkler method for the liquid phase sampled from the bottom nozzle. The monomer concentration was calculated from the total amount. Next, 110 kg of vinyl chloride monomer was charged into this, followed by 52.8 g of ethyl chloroformate.
(equivalent to 0.048 parts by weight per 100 parts by weight of vinyl chloride monomer), 47 g of 35% hydrogen peroxide (as H ₂ O ₂₎
(equivalent to 0.015 parts by weight), 55 g of 30% ammonia water
(equivalent to 0.015 parts by weight as NH ₃ ) was continuously charged. At a polymerization temperature of 58℃, the pressure inside the polymerization system was 2Kg/cm ²
After the polymerization was continued until a decrease in the amount of polyvinyl chloride was observed, unreacted vinyl chloride monomer was collected and dehydrated and dried to obtain a vinyl chloride polymer. In this system, the oxygen concentration in the polymerization system at the start of polymerization was 28 ppm, and the reaction time was 7 hours and 20 minutes.
(See Table 1) Example 2, Comparative Examples 1 and 2, Reference Example Polymerization was carried out in the same manner as in Example 1, with only the oxygen concentration in the polymerization system and the polymerization initiator system being changed. The results are shown in Table 1. The amount of the polymerization initiator system charged is expressed in parts by weight based on 100 parts by weight of the pure monomer.

[Table] The vinyl chloride polymer thus obtained was subjected to a thermal stability test, a firm eye test, and a particle size distribution measurement, and the evaluation results are shown in Table 2. The evaluation method is as follows. Thermal stability test: 100 parts by weight of vinyl chloride polymer, 40 parts by weight of dioctyl phthalate, 3 parts by weight of epoxidized soybean oil, 0.4 parts by weight of barium stearate.
part by weight, 0.4 part by weight of zinc stearate, 0.5 part by weight of trinonyl phenyl phosphite, and 0.1 part by weight of octyltin, and kneaded with a roll to obtain a sheet. Roll condition is roll surface temperature 160
℃, roll gap 0.5 mm, and kneading time 5 minutes.
The resulting sheet was hung in a gear oven at 170°C, and the time required for it to turn black was measured to determine thermal stability. The longer the blackening time, the better the thermal stability. Fishery eye test: 50 parts by weight of dioctyl phthalate, 1.0 parts by weight of calcium stearate, and 1.5 parts by weight of carbon black were added and mixed to 100 parts by weight of vinyl chloride polymer, and the surface temperature was 160 parts by weight.
℃ and roll kneading for 5 minutes with a roll gap of 0.6 mm, and after 5 minutes, the film was taken out with a roll gap of 0.17 mm. The number of fish eyes in a 30 cm ² area of this film was read to determine the quality of the fish eyes. Particle size distribution measurement: Using a Tyler standard sieve, the passing rate of each mesh was cumulatively shown.

【table】

[Table] As is clear from this result, when sodium hydroxide is used as the alkali in a polymerization initiator system consisting of ethyl chloroformate, hydrogen peroxide, and an alkali, the resulting polymer The stability and stability are extremely poor, the particle size distribution is also unsatisfactory, and it is of no commercial value. Furthermore, even if ammonia is used as the alkali, if the oxygen concentration in the polymerization system is higher than 100 ppm, the thermal stability will not be improved sufficiently. On the other hand, it is clear that extremely high quality polymers can be obtained by using ammonia as the alkali and further reducing the oxygen concentration to 100 ppm or less.

Claims (1)

[Claims] 1. In polymerizing vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable therewith in the presence of an alkyl halogenoformate, an inorganic peroxide, and an alkali, ammonia is used as the alkali. A method for producing a vinyl chloride polymer, characterized in that the oxygen concentration in the polymerization system before the start of polymerization is 100 ppm or less based on all monomers. 2. The method for producing a vinyl chloride polymer according to claim 1, wherein the alkyl halogenoformate is an alkyl chloroformate. 3. The method for producing a vinyl chloride polymer according to claim 1 or 2, wherein the alkyl group of the alkyl halogenoformate is an alkyl group having 1 to 8 carbon atoms which may have a branched chain. 4. The method for producing a vinyl chloride polymer according to claim 1, wherein the inorganic peroxide is hydrogen peroxide.