JPH0455201B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is based on the general formula []

[Formula] (However, R represents -H or -CH ₃ and A represents an alkylene group.) Regarding the method for preventing polymerization of the basic vinyl monomer represented by the formula, in detail, the basic vinyl monomer is heated at a temperature exceeding 120°C. The present invention relates to a method for preventing polymerization that is effective in treating areas. Conventionally, aromatic amine compounds, phenolic compounds, phenothiazine, etc. have been frequently used as polymerization inhibitors for the basic vinyl monomer represented by the above general formula [], and other iron compounds (U.S. Pat. No. 4,228,102). , copper compounds (Unexamined Japanese Patent Publication No. 1983-
145612) etc. have also been proposed. The basic vinyl monomer represented by the general formula [] is produced, for example, by aminolysing methyl methacrylate with a predetermined amine. The reaction temperature at this time is generally about 100 to 120°C, and within this temperature range, even conventional polymerization inhibitors are quite effective in preventing the polymerization of the produced monomers. However, when isolating the desired product from the reaction mixture by distillation, the desired product must be exposed to a temperature considerably higher than the reaction temperature, and at such high temperatures, the research conducted by the present inventors is difficult. According to the above, conventional polymerization inhibitors do not have satisfactory effects or have problems with vapor pressure, sublimation, stability, etc., and these polymerization inhibitors may be mixed into products after distillation. This may reduce the product value. In particular, the problem of polymerization of basic vinyl monomers during distillation is a serious problem that not only causes a decrease in the yield, but also seriously impedes operations such as removing the residue from the pot and cleaning the inside of the distillation tower. Therefore, the present inventors conducted extensive research to find a polymerization inhibitor for the basic vinyl monomer represented by the general formula [] that does not have such conventional drawbacks, and found that sodium pyrophosphate, sodium tripolyphosphate, The inventors have discovered that other condensed phosphates are suitable for the purpose and have arrived at the present invention. That is, the present invention is based on the general formula (1): CH ₂ =C(R)-
When treating the basic vinyl monomer represented by CONH・A・N(CH ₃ ) ₂ (where R represents -H or -CH ₃ and A represents an alkylene group) in a temperature range of 130°C or higher, A method for inhibiting polymerization of basic vinyl monomers, characterized in that a condensed phosphate salt is present in an amount equivalent to 0.01 to 2% by weight based on the basic vinyl monomer. ”. Typical condensed phosphates used in the present invention include sodium pyrophosphate, potassium pyrophosphate, sodium tripolyphosphate, potassium tripolyphosphate, and sodium hexametaphosphate.
In particular, sodium tripolyphosphate and sodium hexametaphosphate are preferably used. Further, as the basic vinyl monomer represented by the general formula [] used in the present invention, for example, N, N
-dimethylaminoethyl acrylamide, N,N
-dimethylaminoethyl methacrylamide, N,
N-dimethylaminopropylacrylamide,
Mention may be made of N,N-dimethylaminopropylmethacrylamide or acrylamide-3-methylbutyldimethylamine. In carrying out the present invention, the amount of condensed phosphate used is not particularly limited, but is usually 0.01% of the basic vinyl monomer represented by the general formula [].
~2.0% by weight, preferably 0.05-1.0% by weight
It is. Condensed phosphate is not only applied to the basic vinyl monomer itself represented by the general formula [], but also used when synthesizing the basic vinyl monomer by charging it into a reaction tank together with the reaction raw materials. Polymerization during the synthesis process can be prevented. Furthermore, in the case of preventing monomer polymerization during distillation after the synthesis reaction, the purpose can be achieved by adding a condensed phosphate to the distillation pot or the column section of the distillation column. Condensed phosphates are extremely stable even at high temperatures, have no risk of decomposing and generating foreign substances, and are generally inactive in the synthesis reaction of basic vinyl monomers represented by the general formula []. Therefore, the condensed phosphate can be used without any hindrance in the synthesis reaction of the basic monomer represented by the general formula [] and in the distillation after the reaction. As is clear from the description of the examples below, condensed phosphates are sufficient to prevent the polymerization of the basic vinyl monomer represented by the general formula [] even at temperatures exceeding 120°C and from 130 to 230°C. It has a great effect. Therefore, condensed phosphates are particularly significant in their use as high-temperature polymerization inhibitors, and in this respect they are clearly distinguished from conventional polymerization inhibitors. In addition, in the present invention, it is also possible to use not only the condensed phosphate salt but also a known polymerization inhibitor together with the condensed phosphate salt. The present invention will be explained below with reference to Examples. Example 1 A flask with a capacity of 100 ml was packed with a packed column (column diameter 15 mm, column length 200 mm, 80 6 x 6 mm stainless steel McMahons).
mm filling) was connected, and a reflux condenser was installed above it. 30 g of N,N-dimethylaminopropyl methacrylamide (hereinafter referred to as DMAPMA) and 0.06 g of a polymerization inhibitor were added to the flask, and the flask was immersed in an oil bath. Next, the pressure inside the apparatus was reduced, the mixture was heated to such an extent that weak reflux occurred, and reflux was continued for a predetermined period of time. Thereafter, the flask was cooled to room temperature, the contents were taken out, and the viscosity was measured using a Gardner-Holdt viscometer to determine the degree of polymerization inhibiting effect of each of the various polymerization inhibitors used. The higher the viscosity, the higher the molecular weight of the content, and from the results shown in Table 1, it is clear that the polymerization inhibitor of the present invention has a greater polymerization inhibiting effect than the control example.

【table】

[Table] Example 2 Acrylamido-3-methylbutyldimethylamine was used instead of DMAPMA in Example 1, and the degree of polymerization inhibitory effect of each of the various polymerization inhibitors used was determined in the same manner as in Example 1. . As shown in Table 2, when the polymerization inhibitor of the present invention was used, the increase in the viscosity of the contents was suppressed, and the polymerization inhibitory effect of the present invention was greater than that of the control example. That is clear.

[Table] Time Example 3 (Example of use of polymerization inhibitor in the synthesis reaction of DMAPMA) Methyl methacrylate 150.2 ml was placed in a 300 ml reactor equipped with a thermometer and a 10-stage distillation column.
g, dibutyltin methoxide (catalyst), 2 g, and phenothiazine (conventional polymerization inhibitor), 0.43 g. This mixed solution was heated under nitrogen gas while being stirred, and 51.1 g of N,N-dimethylaminopropylamine was gradually added over a period of 90 minutes at a liquid temperature of 98°C. The methanol produced during this time was distilled out of the system as an azeotropic mixture with methyl methacrylate by adjusting the reflux ratio appropriately. (The top temperature was 64.5 to 70°C) After the addition of N,N-dimethylaminopropylamine, the reaction was continued for about 2 hours. During that time, the temperature of the contents rose to around 110°C, and the temperature at the top of the column rose to over 70°C at the end of the reaction. After the reaction, methyl methacrylate was distilled off under reduced pressure, and then the contents were distilled under reduced pressure of 10 mmHg. At that time, adjust the reflux ratio appropriately and increase the tower top temperature to 139
After cutting the fraction up to 10 mmHg at 139°C/10 mmHg as the first fraction, the main fraction at 139-140°C/10 mmHg was separated and obtained. (The content temperature was 200 to 210°C.) As a result, the yield of the main fraction was 66.0 g (yield based on N,N-dimethylaminopropylamine: 77.5 mol%). The residue from the still was a highly viscous liquid that solidified at room temperature. Next, DMAPMA was synthesized in exactly the same manner as above except that sodium hexametaphosphate (polymerization inhibitor in the present invention) was used in the same weight as phenothiazine instead of phenothiazine. As a result, the yield of the desired product was 73.1 g, N,N
-The yield based on dimethylaminopropylamine is
It was 85.8 mol%, an improvement compared to when phenothiazine was used as a polymerization inhibitor. In addition, the distillation residue had good fluidity when heated and could be extracted smoothly. From these circumstances, it is clear that the polymerization inhibitor of the present invention has a large polymerization inhibiting effect.

Claims (1)

[Claims] 1 General formula (1): CH ₂ =C(R)-CONH・A・N
(CH ₃ ) ₂ - (where R is -H or -CH ₃ , A
represents an alkylene group. ) When treating the basic vinyl monomer represented by
1. A method for preventing polymerization of basic vinyl monomers, which comprises making a condensed phosphate salt present in an amount equivalent to 2% by weight.