JPS62246908A - Production of vinyl chloride polymer - Google Patents

Abstract

PURPOSE:To make it possible to produce a polymer of a superhigh degree of polymerization and to attain high polymer yields within a short polymerization time, by feeding a polymerization vessel with diisobutyl peroxide before feeding it with vinyl chloride, etc., and specifying the polymerization temperature. CONSTITUTION:In producing a vinyl chloride polymer by feeding a polymerization vessel with vinyl chloride or a mixture thereof with a monomer copolymerizable therewith and performing the aqueous suspension polymerization of the monomer in the presence of a catalyst, said polymerization is performed in the following manner. The temperature of the aqueous medium placed in the vessel is kept at 10 deg.C or below, diisobutyl peroxide (DIB) as a catalyst is fed to it before said monomer is fed thereto and the polymerization is performed at a polymerization temperature <=36 deg.C until the conversion reaches at least 60%. It is also possible that said DIB is kept floating on the surface of the aqueous medium by feeding it to the vessel in a state in which the agitator is stopped and mixing by agitation is started on or after the start of feeding of said monomer.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention uses diisobutyryl peroxide (hereinafter abbreviated as DIR) as a fast-acting catalyst to obtain a vinyl chloride polymer with an ultra-high degree of polymerization. This invention relates to a method for aqueous suspension polymerization of vinyl chloride (referring to vinyl chloride or a mixture of monomers copolymerizable with vinyl chloride; the same applies hereinafter).

(Prior art) In the industry, vinyl chloride polymers with an average degree of polymerization of 600 to 1,500 are commonly used, 1.600 to a,
Those with ooo are called high polymerization products, and those with a degree of a, ooo or higher are called ultra-high polymerization products. Furthermore, products manufactured using plasticizers are called soft products. The rubber elasticity of this soft product improves as the average degree of polymerization increases, and products with a high degree of polymerization also improve heat resistance. It is desired to establish a method for producing ultra-high polymerization degree products that have the properties of vinyl chloride polymers and have even higher degree of polymerization in order to exhibit rubber properties.

The present inventors have found that an ultra-highly polymerized product can be obtained by using diisobutyryl peroxide or acetyl cifurooxylsulfonyl peroxide (hereinafter abbreviated as AC3P) as a fast-acting catalyst.

However, with AC8P, it is not impossible to produce ultra-high polymerization products with an average polymerization degree of a, ooo or higher, but the polymerization time is extremely long and the amount of catalyst used is large, so the resulting product It has drawbacks such as poor thermal stability, making it impractical.

Regarding the application of DIR to polymerization catalysts such as vinyl chloride, Japanese Patent Publication No. 48-32,430 describes DIR and tertiary butyryl peroxybivalate (hereinafter abbreviated as TBPP) or tertiary hexyl oxypiparate. (hereinafter abbreviated as THPP) has been proposed to be used in combination with DIR, and if DIR is used at a polymerization temperature of 40 to 60'C, the decomposition rate of DIR is too fast and the catalyst activity will not be lost in a short time. , it is not possible to obtain a high polymerization yield, but T
It is said that the combined use with BPP or THPP can improve the polymerization yield. In other words, this shows that when DIR is used, it cannot be used as a polymerization catalyst unless it is used together with a specific catalyst.

As a method to prevent the deactivation of fast-acting DIR,
No. 6-50892 specifies that DIR should be charged into the polymerization machine at the same time as the charging of vinyl chloride, etc., or during the polymerization start period after the charging of vinyl chloride, etc., but in the case of It is known that it decomposes even at high temperatures and generates radicals, so it is extremely dangerous for safety if a mixed phase of vinyl chloride, etc. and DIR appears even momentarily at room temperature in the absence of an aqueous system. be. In the case of (2), the polymerization progresses with DIR poorly dispersed in the oil droplets of polymerized vinyl chloride, etc., resulting in uneven concentration of I) IB among the oil droplets, resulting in product registration 7 particles. Resin particles with poor plasticizer absorption properties are generated, and fish eyes (hereinafter abbreviated as rFEJ) frequently occur in soft vinyl chloride resin molded products. FE impairs the appearance of resin molded products such as vinyl chloride, thereby significantly lowering the commercial value.

As described above, in the known technology, when DIR is used as a suspension polymerization catalyst for vinyl chloride, etc., it must be used in combination with a slow-acting catalyst, or a mixed phase of [vinyl chloride, etc./DIB] at around room temperature must be used. It is clear that this technology is not yet perfected, as there is a risk of a runaway reaction due to a rapid exothermic reaction, and the quality (FE) of the product resin deteriorates.

[Problem that the invention seeks to solve]

The purpose of the present invention is to establish a manufacturing method that enables the production of ultrahigh polymerization degree products, maintains a high overall polymerization yield even when DIR is used alone, and even in a short polymerization time, and does not deteriorate quality.

(Means for Solving the Problems) The present invention provides a method for producing vinyl chloride polymers by charging vinyl chloride etc. into a polymerization machine and carrying out aqueous suspension polymerization in the presence of a catalyst. , the temperature of the aqueous medium charged in the polymerization machine was kept below 10°C, and D as a catalyst was
In this method, IR is charged before charging the vinyl chloride etc. into the polymerization machine, and the polymerization reaction is carried out at a polymerization reaction temperature of 36° C. or lower until the polymerization rate reaches at least 60%.

DIR is a very fast-acting catalyst, so it can be used at room temperature (25℃).
It is known that radicals are generated near ) and that when it comes into contact with water, it is rapidly hydrolyzed and its function as a catalyst decreases.

In addition, if the dispersion of DIR is uneven among oil droplets such as vinyl chloride and polymerization starts in a state where the DIR concentration between oil droplets is different,
It is also true that it causes quality deterioration such as FE.

As a result of intensive research, the inventors found that the temperature of the aqueous medium fc
By keeping the temperature below 10'C and charging DIR into the polymerization machine before charging vinyl chloride, etc., vinyl chloride can be produced while suppressing the tendency of DIR to generate radicals and its hydrolyzability at low temperatures. By uniformly dispersing DIBi in oil droplets such as oil droplets and carrying out suspension polymerization of vinyl chloride, etc., unresolved problems in terms of safety and product resin quality were solved.

Furthermore, as a measure to avoid contact of DIR with water as much as possible, the temperature of the aqueous medium is kept below 10°C, and when charging DIR into the polymerization machine before charging vinyl chloride, etc., With stirring stopped, DIB'i may be charged and floated on the surface of the aqueous medium, and stirring and mixing may be started at the same time as or after the start of charging vinyl chloride, etc.

The polymerization temperature in the present invention is not particularly limited as long as it is selected to obtain an ultra-high polymerization product, but average polymerization degree a,
The upper limit is 36° C., the temperature at which ooo is obtained, and the lower limit is not particularly limited, but it is preferably the lowest temperature that can be cooled by a cooling method using a normal industrial backing method. Preferably 36℃
It is preferred to carry out the polymerization at a temperature of ~19°C.

In addition, as the degree of polymerization increases, moldability deteriorates, and in order to deal with this, it is necessary to raise the molding temperature, but in order to improve workability without raising the molding temperature as much as possible, it is necessary to increase the moldability during the polymerization process. , the polymerization temperature may be changed in two or more steps. That is, during polymerization, the polymerization temperature after changing the polymerization temperature is raised by 2° C. to 20° C. above the polymerizing temperature before the change. At this time, it is necessary to proceed to the next stage after the polymerization rate before the change reaches 60 to 85%. When proceeding to the subsequent stage of polymerization at 60% or less, the activity of the D r B used decreases rapidly as the polymerization temperature rises, and the polymerization is not completed. Furthermore, even if the conversion is 85% or more, the processability characteristics will not be exhibited due to the small amount of low polymers produced. Furthermore, although the polymerization temperature in the previous stage is 36°C or lower, the polymerization temperature in the latter stage may be 36°C or higher, which is 2 times lower than the polymerization temperature in the previous stage.
C. to 20' C. Although not limited to a higher temperature, it is preferable to do this for 30 minutes before charging the vinyl chloride monomer, or just before charging the vinyl chloride monomer.

After 30 minutes or more, DIR will decompose, This is not preferred because its efficiency decreases.

The method of the present invention is mainly applied to the polymerization of vinyl chloride monomers, but it can also be applied to the copolymerization of vinyl chloride and monomers copolymerizable with vinyl chloride.

Examples of vinyl monomers that can be copolymerized with vinyl chloride monomers include alkyl vinyl esters such as vinyl acetate, and S-fluorine such as cetyl vinyl ether. Examples thereof include α-monoolefin monomers such as rubinyl ether, ethylene, and propylene, alkyl acrylates such as methyl acrylate, and alkyl methacrylates such as methyl methacrylate.

Furthermore, it can also be applied to graft polymerization of vinyl chloride tetramer onto ethylene-vinyl acetate copolymer or ethylene-propylene copolymer.

Dispersants that can be used in the present invention include polyvinyl alcohol (including partially saponified polyvinyl acetate), cellulose derivatives such as methylcellulose, polyvinylpyrrolidone, synthetic polymeric substances such as maleic anhydride-vinyl acetate copolymer, starch, and gelatin. , gum tragacanth, gum arabic fZ, or a mixture of two or more thereof, and is not particularly limited.

(Example) In the examples and comparative examples shown below, thermal stability and F
The determination method for E was as follows.

(1) Method for determining thermal stability [Composition (PHR)] PVC (100) DOP (70) -! -Boxylated soybean oil (2) Calcium stearate (0,6) Zinc stearate (0,9) (Roll film forming conditions) 6 inch roll: 17o''c x 5min (kneading)
, 5 m (thickness) [Open test] The time required for the test piece to blacken in an open environment at 180'C is measured, and thermal stability is determined based on the length and shortness of the time.

(2) FE determination method [Composition (PHR)] PVC (100) DOP (80) Tribasic lead sulfate (5) Lead stearate (1) [Roll film formation conditions] 6 inch a-roll: 160°C x 7 min (kneading) x
Q, 1 ttrx (thickness) (FE determination) Read the number of ungelled particles per roll film i o o oi.

Examples 1 to 7 The inside of a polymerization machine with an internal volume of 2,001 cm equipped with a stirrer was replaced with nitrogen gas, and then partially saponified polyvinyl acetate with a degree of saponification of 80% and an average degree of polymerization of 1,700 was used as a suspending agent in 100 kq5 of pure water at 5°C. 4011 (0.08i parts to vinyl chloride 1
00 parts by weight] into a polymerization machine, and add the amount of DI shown in Table 1.
R (expressed in parts by weight based on 100 parts by weight of vinyl chloride)
After 5 minutes, add 9 to vinyl chloride 50,
At the same time as the preparation starts, turn on the stirrer to start stirring and mixing. Polymerization was started by increasing the temperature to the polymerization reaction temperature shown in Table 1, and the polymerization was stopped at the pressure (recovery pressure) shown in Table 1, and all unreacted vinyl chloride was discharged to obtain a polymer. The polymerization conditions and properties of the obtained polymer are shown in the first column.

Comparative Examples 1 to 5 Examples 1 to 5 except that the catalyst DIBt-AC8P was used, and the catalyst addition, polymerization temperature, and polymerization time were changed as shown in Table 2.
Polymerization was carried out under the same conditions as in Example 7. The results are shown in Table 2.

Comparative Example 6 The polymerization temperature was 38°C, the amount of catalyst charged and the polymerization time were
Polymerization was carried out in the same manner as in Example 1 except that the conditions shown in the table were used. The results are shown in Table 2.

Example 8 In the same manner as Examples 1 to 7, the DI shown in Table 3
Polymerization was carried out at a polymerization temperature of 31°C for 8 hours using a short H.
The temperature was then changed to 44.5° C. over 1 hour, and the polymerization was stopped after 30 minutes. The results are shown in Table 3.

Example 9 In the same manner as Examples 1 to 7, the DI shown in Table 3
Using t of B, first, polymerization was carried out at 28°C for 9 hours (polymerization rate approximately 70%), then the temperature was changed to 38°C over 1 hour, and 1
Polymerization was stopped after an hour. The results are shown in Table 3.

Table 3 Examples 10 to 12 The procedure was the same as in Example 1, except that the temperature of the charging water, the amount of DIR charged, the timing of charging DIR of the vinyl chloride monomer-prepared poem, and the polymerization temperature were carried out under the conditions shown in Table 3. Polymerization was carried out using The results are shown in Table 4.

As can be seen from the comparison between Tables 1 and 2 of Table 4, it is possible to produce products with an ultra-high degree of polymerization using AC3Pt, but the polymerization time is longer than when using DIR. The use of DIR is a much more efficient manufacturing method for ultra-high polymerization products because of the deterioration of thermal stability and the fact that conditions are economically very poor when the degree of polymerization exceeds 6,000. be.

As can be seen from Comparative Examples 5 and 6 in Table 2, DIB is 36
When used at a polymerization temperature of 0.degree. C. or higher, the decomposition rate of DIR is fast, resulting in a decrease in polymerization yield.

As shown in Example 8.9 of Table 3, it is also possible to change the temperature during the polymerization.

As shown in Examples 10 to 11 in Table 4, the catalyst (DIR
), it can be seen that if the charging time is 30 minutes or more before the vinyl chloride monomer is charged, DIR decomposes and the polymerization initiation ability decreases.

Example 13, Comparative Examples 7 to 11 In the method of Example 1, the temperature of pure water charged into the polymerization machine, the start time of stirring and mixing, the time of charging DIR to the polymerization machine, etc. were changed as shown in Table 5. The results were as shown in Table 5.

From Table 5, DIB was added before the start of vinyl chloride charging.
When charging, if the temperature of the charged water is higher than 10°C, polymerization may take a long time or the polymerization yield may decrease, and DIR
It can be seen that a large amount of FE is produced in the obtained polymer film when the charging is carried out at the same time as or after the charging of vinyl chloride.

Figure 1.2 shows polymerization temperature recording charts (jacket cooling water temperature) for Example 1 and Comparative Example 1, respectively.

DIR and AC were used as catalysts in Example 1 and Comparative Example 1, respectively.
Although 0.06 parts by weight and 0.045 parts by weight of 8P were used, as shown in Figure 1, for DIB (Example 1), which is a fast-acting catalyst, an active exothermic reaction appeared from the early stage of the polymerization reaction, and during the middle stage of the reaction. It can be seen that the heat of reaction is effectively removed even during the period from ~ to the final stage.

As shown in Figure 2, in the case of AC8P (Comparative Example 1), which is a slow-acting catalyst, the exothermic reaction in the early to middle stages of the polymerization reaction is slow. It can be seen that increasing t may make it impossible to control the internal temperature of the polymerization system, considering the removal of reaction heat at the end of the reaction.

Accurate control of the internal temperature of the polymerization system is an important element in obtaining high-quality resin with a high average degree of polymerization.

From the above, it is clear why the usage amount of AC8P is limited.

[Brief explanation of drawings]

Figures 1 and 2 show polymerization temperature recording charts (jacket cooling water temperature) of Example 1 and Comparative Example 10, respectively. that's all

Claims (3)

[Claims] (1) Vinyl chloride-based polymers are produced by charging vinyl chloride or a monomer copolymerizable with vinyl chloride (hereinafter simply referred to as vinyl chloride, etc.) into a polymerization machine and carrying out aqueous suspension polymerization in the presence of a catalyst. In this method, the temperature of the aqueous medium charged into the polymerization machine is maintained at 10°C or less, and diisobutyryl peroxide as a catalyst is charged before charging the vinyl chloride etc. to the polymerization machine, and the polymerization rate is maintained. at least 60%
The method described above is characterized in that the polymerization reaction is carried out at a polymerization reaction temperature of 36°C or less until the temperature reaches 36°C. (2) The method described in item (1), characterized in that diisobutyryl peroxide is charged while stirring of the polymerization machine is stopped. (3) In the method described in paragraph (1), the polymerization rate is 6.
The above method, characterized in that the post-polymerization temperature is raised by 2 to 20° C. after reaching 0 to 85%.