JPH032883B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a vinyl chloride polymer in which a good polymer can be obtained even if the polymerization initiator is used in a state containing impurities without being purified after production. 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. Dialkyl peroxydicarbonates and the like are usually produced in a yield of 70 to 90% by reacting a mixture of alkyl chloroformates, hydrogen peroxide, and alkali substances such as sodium hydroxide. It is commercially available after completely removing unreacted chloroformic acid alkyl ester and decomposition products contained in the reaction product. These two steps of production and purification are the main factors that make dialkyl peroxydicarbonate expensive, and if it were possible to omit the purification step, the polymerization initiator could be supplied at a low cost. Furthermore, 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 installed, handling during actual use would be dangerous. In order to avoid these problems, 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 simultaneously added to the polymerization vessel. A method of polymerizing vinyl chloride while producing peroxydicarbonate is described, for example, in U.S. Pat.
It has been proposed in No. 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. This is presumed to be caused by impurities that are generated or unreacted during the production of the polymerization initiator. The present inventors have conducted intensive studies on a method for polymerizing vinyl chloride monomers using inexpensive dialkyl peroxydicarbonate polymerization initiators without these drawbacks, and have found that alkyl halide formates and inorganic peroxydicarbonate polymerization initiators can be used as polymerization initiators. Oil-soluble impurities and dialkyl peroxydi Discovered that extremely high quality polymers could be produced by using an organic solvent layer containing carbonate and maintaining the oxygen concentration in the polymerization system before the start of polymerization below a specific value, and completed the present invention. I reached it. That is, an object of the present invention is to provide an inexpensive method for producing a vinyl chloride polymer, which allows an excellent polymer to be obtained even if the polymerization initiator is used in a state containing impurities without being purified after production. . 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 a polymerization initiator, using an alkyl halogenoformate, an inorganic peroxide, and an inorganic peroxide as a polymerization initiator. The organic solvent containing the reaction product obtained by reacting an alkali in the presence of water and a water-insoluble organic solvent is used without purification, and the oxygen concentration in the polymerization system before the start of polymerization is determined relative to the total monomers. A method for producing a vinyl chloride polymer characterized in that the content of the vinyl chloride polymer is 100 ppm or less. 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 copolymerizable with vinyl chloride include vinyl esters such as ethylene, propylene, butene, pentene-1, butadiene, styrene, α-methylstyrene, acetic acid, caproic acid, caprylic acid, and benzoic acid. or allyl esters, dialkyl maleic acid or fumaric acid esters in which the alkyl group has 1 to 12 carbon atoms (C _{1 to 12} ), acrylonitrile, vinylidene chloride, vinylidene cyanide,
Alkyl vinyl ether of C _1-12 alkyl group,
Examples include N-vinylpyrrolidone, vinylpyridine, vinylsilanes, acrylic acid alkyl esters having alkyl groups from C1 _{to C16} , or methacrylic acid alkyl esters, and at least one of these is added in an amount of 0.01 to 40 parts per 100 parts by weight of vinyl chloride. It can be copolymerized in an amount of 5 parts by weight, preferably 5 to 30 parts by weight. 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 hydrogen atom, or a fluorine atom, respectively. ] The alkyl group R preferably has 1 to 10 carbon atoms, particularly 2 to 4 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-
Examples include hexyl chloroformate, n-heptyl chloroformate, n-octyl chloroformate, 2-ethylhexyl chloroformate, and the like. However, it is not limited to these. The inorganic peroxide used in the method of the present invention is not particularly limited as long as it reacts with the aforementioned alkyl halogenoformate and alkali 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 because it causes less contamination of impurities in the polymerization initiator manufacturing process. The concentration of hydrogen peroxide is not particularly limited as long as it is a commonly available aqueous solution, but from the viewpoint of ease of handling and reducing the introduction of excess water into the polymerization system, the concentration is between 30 and 35%.
% concentration and diluted appropriately. Therefore, the amount of hydrogen peroxide used is preferably 0.1 to 5 mol per 1 mol of the alkyl halide formate used.
Preferably, it is 0.5 to 2.5 mol. Further, the alkali used in the method of the present invention is not particularly limited as long as it is water-soluble, and examples include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali oxides such as sodium oxide and potassium oxide. Examples include metals, ammonia, etc., and at least one of these is used. These alkalis may be used as an aqueous solution if necessary. Ammonia may also be used in the form of commercially available ammonia water. Therefore, the amount of alkali used is per mole of alkyl halide formate.
A range of 0.2 to 10 mol, particularly 1 to 5 mol is preferred. When the amount of inorganic peroxide and alkali used is less than the above-mentioned ratio, the conversion to dialkyl peroxydicarbonate that acts as a polymerization initiator is not sufficient; Most of the oxides and alkalis remain in the reaction system without participating in the reaction, which is not only disadvantageous economically, but especially when there are a lot of alkalis, the synthesized dialkyl peroxydicarbonate may be decomposed. As a result, the yield of the polymerization initiator apparently obtained is lowered, and the quality of the polymer is also likely to be lowered. The polymerization initiator used in the method of the present invention is synthesized by reacting in the presence of water and an organic solvent insoluble in water.Water may be added separately to the reaction system, but usually inorganic peroxide Water from an aqueous solution of a compound or an alkal is sufficient. Examples of organic solvents include toluene, mineral spirits, ethylene dichloride,
Carbon tetrachloride or the like is used, and the amount used is preferably 50 to 200 parts by weight per 100 parts by weight of alkyl halide formate. Although a polymerization initiator is produced even in the absence of an organic solvent, there is a risk of explosion due to the high concentration of the polymerization initiator, and the organic solvent acts as a diluent during the synthesis of the polymerization initiator. For example, the polymerization initiator is synthesized by mixing the above-mentioned essential components and carrying out a synthesis reaction at room temperature for 5 to 20 minutes. The reaction takes place at the oil-water interface, and the polymerization initiator is dissolved in an organic solvent. As the reaction temperature becomes higher, the synthesized polymerization initiator is more likely to decompose, so the reaction temperature is preferably up to about 30°C. After the reaction is completed, the reaction product is allowed to stand and is separated into an aqueous layer and an organic solvent layer, and the aqueous layer in which the alkali metal and the like are dissolved is removed. Although the organic solvent layer contains impurities such as unreacted alkyl halogenoformate, it is used as a polymerization initiator in the production of a vinyl chloride polymer without being purified. The organic solvent containing the polymerization initiator may be added to the polymerization system before the polymerization reaction, or may be added continuously to the polymerization system after the initiation of the polymerization. In short, it is preferable to prepare the polymerization initiator at the same time as when it is added to the polymerization system, thereby eliminating the need to cool the polymerization initiator and causing problems such as explosions due to rapid self-heating decomposition. can be prevented. Although the amount of the polymerization initiator used varies depending on the number of carbon atoms in the alkyl group of the dialkyl peroxydicarbonate acting as a polymerization initiator, the polymerization rate, etc. 0.005-0.1% by weight relative to other monomers, preferably 0.01-0.01%
Selected from a range of 0.05% by weight. In addition, 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, particularly 5 to 100 ppm. It is preferable that it is in the range of . The oxygen concentration within 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. Surprisingly, by reducing the oxygen concentration in the polymerization system to 100 ppm or less,
It has been found that even if an organic solvent containing impurities is used as a polymerization initiator, a polymer with excellent thermal and mechanical properties can be obtained. When the oxygen concentration is extremely reduced, that is, below 5 ppm, the suspension stability of the polymerization system tends to deteriorate, the particle size tends to become rough, and the fisheye properties tend to deteriorate. 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 pressurize a highly purified organic solvent containing a polymerization initiator synthesized by the method described above, and suspend at a temperature of 30 to 70°C. Perform turbidity polymerization or emulsion polymerization. The method of the present invention is most preferably employed in suspension polymerization. The suspending agent used in the method of the present invention is not particularly limited, but has highly water-soluble materials such as partially saponified polyvinyl alcohol, hydroxypropyl methylcellulose, vinyl acetate-maleic anhydride copolymer, polyvinylpyrrolidone, and gelatin. Molecular substances may be used alone or in mixtures. 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 controlling the polymerization rate. According to the method of the present invention, alkyl halogenoformate,
Since the dialkyl peroxydicarbonate obtained by reacting an inorganic peroxide and an alkali in the presence of water and a water-insoluble organic solvent is dissolved in the organic solvent layer, water-soluble by-products are removed as the aqueous layer is removed. No water-soluble impurities are introduced into the polymerization system. Even if the organic solvent layer contains impurities such as decomposition products of unreacted alkyl halogenoformate or dialkyl peroxydicarbonate, the oxygen concentration in the polymerization system before the start of polymerization can be adjusted relative to the monomer.
By controlling the amount to 100 ppm or less, a polymer with excellent thermal properties such as thermal stability, and fish eye properties such as gelling property can be obtained. 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. The quality of the obtained vinyl chloride polymer was evaluated 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, 2 parts by weight of barium stearate and 1 part by weight of zinc stearate were mixed and heated to 160°C. The mixture was kneaded for 5 minutes using temperature-controlled rolls to obtain a sheet. the obtained sheet
The sample was hung in a gear oven controlled at 170°C and the time until it turned black was measured. [Fish eye test] Mix 100 parts by weight of vinyl chloride polymer, 50 parts by weight of dioctyl phthalate, 1 part by weight of calcium stearate and 1 part by weight of carbon black and heat at 160°C.
Knead for 5 minutes using temperature-controlled rolls and take out the sheet. The number of fish eyes on this 100 cm ² sheet was counted. Synthesis method of polymerization initiator: Polymerization initiator [] Chloroformic acid secondary butyl ester 27gr, 5
25g of 140gr of 5wt% hydrogen peroxide solution, 160gr of 5wt% aqueous sodium hydroxide solution and 30gr of ethylene dichloride
The mixture was placed in a glass beaker in a constant temperature bath controlled at ℃, stirred for 15 minutes, allowed to stand, and only the supernatant aqueous phase was separated and removed. Obtained. The yield of this reaction was 65%, and about 40% of the input secondary butyl chloride formate was included in the peroxide as an impurity. Polymerization initiator [] 22gr of chloroformic acid ethyl ester, 210gr of 5wt% hydrogen peroxide solution, 200gr of 5wt% ammonia aqueous solution, and 20gr of toluene were placed in a glass beaker in a constant temperature bath adjusted to 25℃, stirred for 15 minutes, and then allowed to stand still. Only the aqueous layer was separated and removed to obtain a toluene solution of diethyl peroxydicarbonate containing impurities. The yield of this reaction was 55%. Example 1, 2 Comparative Example After charging 110 gr of partially saponified polyvinyl acetate and 165 g of water into a stainless steel autoclave with an internal volume of 300, the inside of the polymerization system was sucked to -700 mmHg with a vacuum pump, and then the pressure was returned to normal pressure with nitrogen gas. This operation was repeated 6 times to fully remove oxygen from the polymerization system, and then oxygen gas was sealed in the polymerization system to achieve the predetermined oxygen concentration shown in Table 1. Next, 11 kg of vinyl chloride monomer (VCM) was charged, and then ethylene dichloride solution and toluene solution as polymerization initiators shown in the table were added, and the temperature was raised to a polymerization temperature of 58°C to carry out a polymerization reaction. After polymerization continued until the pressure within the polymerization system showed a drop of 2 kg/ ^cm2 ,
Unreacted vinyl chloride monomer was collected and dehydrated and dried to obtain a vinyl chloride polymer. These qualities are also shown in the table. The vinyl chloride polymer seen in the comparative example is an example in which a polymerization initiator [ ] was applied at an oxygen concentration similar to that of a normal polymerization method, but its quality was extremely poor in both thermal stability and durability, making it very difficult to put into practical use. It is not something that can be provided for. On the other hand, Examples 1 and 2, which are vinyl chloride polymers obtained by the method of the present invention, have excellent thermal stability and durability. 【table】

Claims (1)

[Claims] 1. When vinyl chloride or a mixture of vinyl chloride and a monomer copolymerizable therewith is polymerized in the presence of a polymerization initiator, an alkyl halogenoformate, an inorganic peroxide, an alkali, To purify an organic solvent containing dialkyl peroxydicarbonate and oil-soluble impurities prepared by mixing and reacting water and a water-insoluble organic solvent, allowing the reaction product to stand still, and then separating oil and water. 1. 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 10 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.