JPS5858362B2 - Enkabinirunokendakujiyugohouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a process for suspension polymerization of vinyl chloride in an aqueous medium.

More specifically, it is possible to easily and efficiently produce polyvinyl chloride with excellent thermal stability and little coloration by preventing the formation and adhesion of polymer scale on the walls of the polymerization vessel without causing a gel effect. Regarding how to.

Demand for polyvinyl chloride, which is produced by suspension polymerization, has been increasing in recent years as a general-purpose resin, but technically there are two problems: (1) scale adheres to the walls of the polymerization vessel, reducing the cooling effect; Furthermore, if this flakes off and mixes into the product, it will cause adverse effects such as causing fish eyes.

(2) Since the polymer is insoluble in the monomer, this is usually called the gel effect, but when the required high polymerization rate is reached, the polymerization rate rapidly increases, resulting in non-uniformity of the product and Problems such as fish eyes occur.

(3) If a polymerization initiator such as diisopropyl peroxydicarbonate or τ cetyl cyclohexyl sulfonyl peroxide is used to increase polymerization efficiency, the reaction will occur explosively, making it difficult to control, and reducing the amount of polyvinyl chloride produced. There are various problems such as deterioration of physical properties, and when the amount of initiator is reduced, the polymerization substantially stops before the reaction reaches a high polymerization rate.Therefore, there continues to be a need for an even better polymerization method. There is.

In order to overcome the drawbacks of the conventional methods as described above, the present inventors have made extensive studies and have made ditertiary-butylhyponitrite monomers in an aqueous medium containing vinyl chloride or a vinyl monomer mainly composed of vinyl chloride. 0.001-0.5 for mass
The present invention has been completed by discovering a suspension polymerization method for vinyl chloride that solves the above-mentioned drawbacks of the conventional method at once and efficiently yields excellent products by polymerizing at 35 to 60° C. in addition to the weight ratio.

The effects of the method of the present invention are believed to be due to the following factors.

(1) The polymerization initiator of the present invention has extremely high activity, so when used for suspension polymerization of vinyl chloride, it is possible to perform polymerization very efficiently compared to conventional azo polymerization initiators. can be,
Even if the amount of initiator is reduced, the polymerization essentially does not stop before a high polymerization rate is reached, thus making possible a polymerization method that does not produce a linear gel effect.

(2) It is said that the adhesion of polymer scale on the walls of the polymerization vessel is caused by chlorine ions generated when vinyl chloride and polyvinyl chloride are mixed with acids, but this may be because the initiator of the present invention has no oxidizing power. The adhesion of scale to the walls of the polymerization vessel is extremely reduced and does not pose a problem at all.

(3) Unlike the azonyl-IJ polymerization initiator commonly used in the past, it does not have a nitrile group, so it has improved thermal stability, does not exhibit a gel effect, and does not cause polymer scale adhesion. Coupled with this, a product with excellent physical properties can be obtained.

The amount of ditertiary butyl hyponitrite used is
The amount is preferably 0.001 to 0.5% by weight based on the monomer. If the amount is less than this, the effect will be reduced, and if the amount is more than this, the physical properties of the product will be deteriorated and it will be economical. Not.

The polymerization temperature is preferably 35 to 60°C; at temperatures below 35°C, polymerization takes a long time and is not efficient, and at temperatures above 60°C, the reaction may proceed rapidly.

Other polymerization conditions in the method of this invention may be exactly the same as those for conventionally known suspension polymerization.

Therefore, this includes polyvinyl alcohol as a suspending agent,
Synthetic or natural water-soluble polymer substances such as various water-soluble cellulose derivatives, vinyl acetate-maleic anhydride copolymers, gelatin, and starch are used, and various solvents as molecular weight regulators are added as necessary. and stir for 35~
Polymerization may be carried out overnight at 60°C.

In addition, although the above description has mainly been made regarding a homopolymer of vinyl chloride, the method of the present invention can be similarly applied to its copolymer mainly composed of vinyl chloride.9. Examples of monomers that can be copolymerized with vinyl chloride include various vinyl esters, vinyl ethers, aromatic vinyls, acrylic acid or meccrylic acid esters, maleic acid esters, and a-olefins.

As described above, by using the method of the present invention, it was possible to significantly shorten the polymerization time, resulting in a significant improvement in productivity.

Furthermore, to describe the effect of the method of the present invention, in order to suppress the gel effect, an initiator system that combines low-temperature activity and high-temperature activity was used, but the drawback of this system is that the low-temperature-active initiator is replaced by the high-temperature activity. During the middle stage of polymerization, when the initiation effect is transferred to the initiator, a sagging phenomenon was observed in the polymerization rate in the cold, resulting in a prolongation of the polymerization time and undesirable phenomena such as non-uniformity of the product (hi, fish eyes, etc.). By using it, it is possible to achieve uniform polymerization without gel effect without the above-mentioned sagging phenomenon, and as a result, a product can be obtained in which problems such as initial discoloration and fish eyes are solved.

The present invention will be further explained with reference to Examples below.

In the examples, "part" indicates a part by weight, "%" indicates a weight %, and each abbreviation means the compound shown below.

DBH-(1>: dikushaributylhibonitrite ADVN-(2): 2,2'-azobis-2,4-dimethylvaleronitrile ADMVN-(3): 2,2'-azobis-2,4 dimethyl -4-Methoxyvalerotritrile I P P -(4): Diisopropyl beoxy dicarbonate Example 1 In a sealed tube, 10 parts of water, 5.3 parts of vinyl chloride, polyvinyl alcohol (Cosenol GH-20, Nippon Gosei Chemical Industry Co., Ltd.) Add 0.06 parts of DBH) and 0.0016 parts of DBH,
Polymerization was carried out at 0'C, and the relationship between polymerization time and polymerization rate was plotted, and the results shown in Figure 1 of the attached sheet were obtained.

For comparison, results obtained using conventional initiators ADMVN and IPP under the same conditions are also shown.

As is clear from the figure, in the case of ADMVN, the polymerization activity disappeared during the polymerization, and in the case of IPP, a gel effect occurred, and neither of them achieved the desired uniform polymerization rate.

When using DBH, a very efficient, gel-effect-free, and uniform reaction rate was obtained.

Example 2 In a pressure-sealed glass tube, 10 parts of water, 5.3 parts of vinyl chloride, 0.06 parts of polyvinyl alcohol (same as used in Example 1), and 0.0016 parts of DBH as an initiator were placed. In addition, the tube was melt-sealed while replacing the air in the tube with nitrogen gas, and then subjected to shaking polymerization at 40°C, 145°C, and 50°C.

As a result of sampling at regular intervals from the start of polymerization, the relationship between polymerization time and polymerization rate was as shown in FIG.

As a control, the same amount of ADVN was used as an initiator at 50°C.
The polymerization was carried out in exactly the same way with the warm concubine of DB.
The relationship between polymerization time and polymerization rate at 40° C. was almost the same as in the case of H.

In other words, DBH exhibits higher activity at lower temperatures than ADVN, which is an azonitrile-based initiator that exhibits a practical polymerization time polymerization group relationship, even at high temperatures. There was also no phenomenon of gradual decline in activity.

In the polymerization of vinyl chloride, the polymerization rate depends only on the polymerization temperature and temperature, so in order to obtain vinyl chloride with a high polymerization rate, it is necessary to conduct the polymerization at a low temperature. In this case, the method of the present invention can be used. As a result, the desired polymerization vessel product can be obtained in a short time.

Example 3 2.5 parts of polyvinyl alcohol, 5000 parts of water, and the initiator shown in the table below were added to a stainless steel polymerization vessel having an internal volume of 1007 cm. After reducing the pressure inside the polymerization vessel, 25000 parts of vinyl chloride was added to the vessel. When the mixture was stirred and polymerized at the polymerization temperature shown in the table below, the results shown in the table below were obtained.

In addition, each physical property value in the table is based on the prescription and method shown in the table below.

(1) Amount of scale attached: The amount of scale attached to the inner wall of the polymerization vessel is expressed in g.

(2) Fish Eye: 100 parts of polyvinyl chloride, 50 parts of dioctyl phthalate, 1 part of dibutyltin sila*urate, 1 part of stearic acid, and 0.05 parts of carbon black.
The mixture was kneaded with a roll at 150°C for 7 minutes to form a 2 mm thick sheet, and the number of fish eyes contained in the sheet per 100 cyJ was measured by passing light through this. Indicated.

(3) Colorability: Add 50 parts of dioctyl phthalate and 2 parts of stearic acid to 100 parts of polyvinyl chloride.
After kneading with rolls at 165°C and taking out sheets at regular intervals, the appearance is shown.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between polymerization time and polymerization rate in Example 1,
FIG. 2 shows the relationship between polymerization time and polymerization rate in Example 2.

Claims (1)

[Claims] 1. Into an aqueous medium containing vinyl chloride or a vinyl monomer mainly composed of vinyl chloride, add dikushaributylhybonitrite at a weight ratio of o, o o i to 0.5 to the monomer, and add 35 to A method for suspension polymerization of vinyl chloride, characterized by polymerizing at 60°C.