JPS5952641B2 - Suspension polymerization method of vinyl chloride - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention deals with vinyl chloride monomer (hereinafter referred to as VC
This relates to a method for producing vinyl chloride resin (hereinafter referred to as PVC) with the aim of reducing the amount of CM) contained in molded objects molded using the resin. be.

Recently, concerns about the health safety of CM in PVC manufacturing plants have been raised, including the reduction of VCM concentration in the working environment of PVC manufacturing plants and molding processing plants, the reduction of the amount of VCM released from the factory into the atmosphere, and the reduction of VCM emissions during molding. A decrease in the concentration of VCM contained in the body is a sanitary problem that must be solved. Industrially, PVC is most often produced mainly by suspension polymerization, and conventionally PVC is partially quenched in an aqueous medium in the presence of an azobis-based or organic peroxide-based oil-soluble radical polymerization initiator. polyvinyl acetate, methylcellulose, hydroxymethylcellulose, polyvinylpyrrolidone, polyacrylic acid,
Water-soluble synthetic polymers such as vinyl acetate-maleic acid copolymer and styrene-maleic acid copolymer, or water-soluble natural polymers such as gelatin and starch, or MgCO3, Mg
Suspension polymerization of CM has been carried out using poorly water-soluble inorganic fine powder such as SO4 and BaSO4 alone or in combination as a suspension stabilizer.

When using a conventional suspension stabilizer, VCM or a mixture of VCM and a vinyl monomer copolymerizable with VCM is heated at a temperature of 50° to
Suspension polymerization is carried out at 70°C, and when the polymer conversion rate is 70-90%, the unpolymerized VCM is removed from the polymerization vessel under the VCM gas pressure at that temperature and further under reduced pressure, and the polymerization is stopped by liquefaction recovery. After dehydration and drying, PVC is obtained.
However, when collecting unpolymerized VCM, the PVC in the slurry discharged from the polymerization can contains more than 1000 ppn of VCM, and the PVC product obtained after dehydration and drying contains 100 ppn or more of VCM.
Contains VCM of pn or more. This increases the concentration of VCM in the working environment at PVC manufacturing plants and molding plants, and as a result, VCM remains in molded products such as blow bottles, sheets, and films. The present invention relates to a method for effectively solving these problems.

That is, when VCM or a mixture of VCM and a vinyl monomer copolymerizable with VCM is suspension polymerized in an aqueous medium at 50 to 70°C in the presence of an oil-soluble radical initiator, 0.01 as a suspension stabilizer is used. 0.005 to 0.0001 part of a water-soluble polymer compound having a specific viscosity of 0.1 or more at 60° C. in an aqueous solution by weight (hereinafter all weight %), and 0.05%
The surface tension of an aqueous solution at 25°C is 55 dyne/Cm
Add the following water-soluble polymer compound (B) to the water medium at 0.1
~0.01 part and 20/80 ethanol/toluene (
The absolute viscosity at 25°C of a 5% solution of
It is characterized by using together with 0.1 to 0.001 parts of an oil-soluble polymer compound (C) having a CPS or higher and an 8% ethylene dichloride solution at 30°C being a true solution to VCM, and increasing the polymer conversion rate. 70-90% unpolymerized VCM
By recovering the VCM under the gas pressure of VCM and further under reduced pressure, the VCM contained in the PVC in the slurry discharged from the polymerization reactor becomes less than 30P, and the VCM contained in the PVC product obtained after dehydration and drying is reduced. This is a method showing a remarkable effect of reducing the amount to 1 ppn or less, and is an improved method of the already disclosed invention (Japanese Patent Application Laid-Open No. 130492/1983). Also, in the patent application filed earlier (Japanese Patent Application No. 51-70716), the unrecovered V
When the CM recovery speed is increased, the slurry foams more intensely and the PV
Although there was a drawback of causing scattering of C particles, this point has also been improved in the present invention. In addition, this method does not allow the adhesion of polymeric substances, commonly known as "scale," inside the polymerization can, making it possible to omit the work inside the can to remove scale, thereby improving the working conditions at PVC manufacturing plants.

The suspension stabilizer used in the present invention is characterized by the combined use of substances classified into three types, and is a water-soluble polymer (
Items classified as 4) do not require surface activity and the surface tension of a 0.05% aqueous solution at 25°C is 55 dyne/C.
It may be m or more, and has the general formula X (CH2CH2O).

-Y (wherein X and Y are hydrogen, a hydroxy group, an alkyl group, a hydroxyalkyl group, a polypropylene oxide group, and n is an integer of 20,000 or more), in which x is a hydroxy group, Examples include polyethylene oxide in which Y is hydrogen; maleic anhydride-methyl vinyl ether copolymer; alkyl acid, alginate sodium salt, and the like. Usage amount is 0.00 per 100 parts of aqueous medium
5 to 0.0001 part is desirable; if it is less than 0.0001 part, the effect of reducing VCM remaining in PVC will be small;
Even if more than 5 parts is added, the reduction effect is saturated, and depending on the type of additive, the thermal stability of the product and the physical properties of "Fishyuai" may deteriorate, and on the other hand, there may be a cost disadvantage. invite The surface tension of a 0.05% aqueous solution at 25°C is 55
Examples of the water-soluble polymer (B) having a saponification degree of 82m01% or less, methyl cellulose, and methyl cellulose, especially those having a methoxy group content of 2
There are methylcellulose and the like having a hydroxypropoxy group content of 0% or more and 4% or more.

The amount used is preferably 0.1 to 0.01 part based on the aqueous medium; if it exceeds 0.1 part, the emulsion particles will increase and there will be a lot of fine powder, making it difficult to obtain the desired suspended particle size. If it is less than that, the suspension stability will be decreased and agglomeration will occur during the polymerization, which will hinder the polymerization operation. An oil-soluble polymer (exemplified as O) in which the absolute viscosity at 25°C of a 5% mixed solution of 20/80 (weight mixing ratio) of ethanol/toluene is 5 Cps or more, and the 8% ethylene dichloride solution at 30°C is a true solution. An example of such a cellulose is ethylcellulose having an ethoxy group content of 44 to 51%.

The amount of ethyl cellulose is 0.1 to 0.00 relative to VCM.
It is desirable that the amount is 1 part; if it exceeds 0.1 part, the molded product will be colored, and if it is less than 0.001 part, the effect of reducing residual VCM will not be noticeable. Note that any number of these three types may be used in combination. Examples of vinyl monomers that can be copolymerized with VCM include known monomers such as vinyl acetate, maleic acid, itaconic acid, vinylidene chloride, ethylene, and propylene.

In addition, the oil-soluble radical initiator used in the present invention is an azo compound such as azobisisobutylnitrile, azobis2,4-dimethylvaleronitrile, lauroyl peroxide,
Known initiators include organic peroxides such as t-butyl pivalate, di-2-ethynolehexynoleperoxydicarbonate, and diisopropylperoxydicarbonate. Furthermore, in the suspension polymerization of the present invention, menolecaptan, disnolehydride, trichloroethylene, etc. are added as polymerization degree regulators, and alcohols, saturated hydrocarbons, aromatics such as benzene, toluene, DOP, epoxy soybean oil, etc. are added as additives. There is no problem in using plasticizers together. Suspension polymerization consists of unpolymerized VCM at a polymer conversion of 70-90% in the presence of the above raw materials and additives.
is recovered to atmospheric pressure using VCM gas pressure, and unpolymerized CM remaining in the slurry is removed under reduced pressure at a temperature above the polymerization temperature using a vacuum pump, and is liquefied and recovered.

The suspension polymerization method of the present invention provides suspended polymer particles that improve the efficiency of recovery and removal.
M is 1000p Sakigami and Mibu (branch) S is 30 according to the present invention
p Becomes subcocoon. Subsequently, the slurry discharged from the polymerization vessel is dehydrated, and the residual VCM in the resulting PVC product is 100'Ppm or more in the case of a conventional polymerization method, and 1 ppn or less in the case of the present invention.

Accordingly, according to the present invention, the amount of VCM exhausted at a vinyl chloride resin manufacturing factory will be reduced to 1/30 or less, the amount of VCM remaining in the vinyl chloride resin product after drying will be reduced to 1/100 or less, and the amount of VCM exhausted during the molding process will be reduced to 1/100 or less. This is an extremely effective suspension polymerization method that allows the amount of VCM to be reduced to 1/100 or less. The present invention is characterized by the combined use of all three types of polymer compounds (A), (B), and (O), and the absence of any one type will result in disadvantages.

Residual VCM in the polymer obtained by combining (4) and (B)
The reduction effect of (B) and (6) is smaller than that of the present invention.
The combination of (4) and (B) has only the same effect as the combination of (4) and (B), and the polymerization method using (4) and (O) in combination lacks suspension stability. However, these do not limit the scope of the present invention.

Example: Absolute viscosity of 4% aqueous solution at 20°C is 35CpS and 0.05% in a stainless steel polymerization machine of 120001.
400 g of partially saponified polyvinyl acetate whose aqueous solution has a surface tension of 51 dyne/Cm, 30 g of polyethylene oxide whose specific viscosity at 60°C is 0.2 as a 0.01% aqueous solution, and 5 ethanol/toluene (20/80 weight ratio). The absolute viscosity of the % solution at 25°C is 80-105 CPS,
An 8% ethylene dichloride solution at 30°C is a true solution, and 10 g of demineralized water in which 50 g of ethyl cellulose with an ethoxy group content of 47.5 to 49.0% is dissolved and dispersed.
00 kg was charged, 125 g of initiator di, 2-ethylhexyl peroxydicarbonate was added, and after degassing with a vacuum pump, 500 kg of vinyl chloride monomer (VCM) was charged, and the polymerization was carried out at an internal temperature of 58°C until the polymerization pressure reached polymerization. When the pressure in the tank decreased by 1 kg/Cnl2 from the steady pressure inside, unpolymerized CM was collected, VCM was collected and removed under reduced pressure at a slurry temperature of 60°C for 30 minutes, and the slurry was discharged from the can.

Subsequently, the slurry was dehydrated and dried in a fluidized bed at 55°C in a fluidized dryer.
After drying for 1 hour, vinyl chloride resin with a moisture content of 0.3% (
PVC) was obtained.

Example 2 As a suspension stabilizer, 400 g of partially saponified polyvinyl acetate described in Example 1 and 5 g of methyl vinyl ether-maleic anhydride copolymer having a specific viscosity of 1.2 at 60° C. in a 0.01% aqueous solution were used. 50g of ethylcellulose mentioned in 1.
1,000 kg of demineralized water dissolved and dispersed in 2,000 kg of
1. PVC was obtained in the same manner as in Example 1 except that the mixture was charged into a stainless steel polymerization can.

Example 3 Methyl cellulose 3 as a suspension stabilizer has an absolute viscosity of 100 CPS at 20° C. in a 2% aqueous solution, a methoxy group content of 21%, and a hydroxypropoxy group content of 6.2%.
50g and polyethylene oxide 20 as described in Example 1
g and 5% of ethanol/toluene (20/80 weight ratio)
The absolute viscosity of the solution at 25°C is 7 CPS, the true solution is an 8% ethylene dichloride solution at 30°C, and demineralized water in which 50 g of ethyl cellulose with an ethoxy group content of 47.5 to 49.0% is dissolved and dispersed. 1000kg 2
00 in an old stainless steel polymerization can, and added 2,
2″-azobis2,4-dimethylvaleronitrile 175
g, and the subsequent operations were the same as in Example 1.
I got a C.

Example 4 Partially saponified polypropylene as described in Example 1 was used as a suspension stabilizer. The absolute viscosity at 25°C of 400 g of vinyl acetate, 5 g of the methyl vinyl ether-maleic anhydride copolymer described in Example 2, and a 5% solution of ethanol/toluene (20/80 weight ratio) at 25°C is 200 CpS, and the absolute viscosity at 30°C is 200 CpS. 8% ethylene dichloride solution is a true solution, and the ethoxy group content is 49.0~
1000 kg of demineralized water in which 50.0% ethyl cellulose was dissolved and dispersed was charged, and the rest was carried out in Example 1.
PVC was obtained by the same operation as above.

Comparative Example 1 Partially saponified polyvinyl acetate 40 from the suspension stabilizer of Example 1
The same operation as in Example 1 was performed except for 0 g.

Comparative Example 2 The same operation as in Example 1 was performed except that ethyl cellulose was removed from the suspension stabilizer in Example 1.

Comparative Example 3 The same operation as in Example 2 was carried out except that the partially saponified polyvinyl acetate was removed from the suspension stabilizer of Example 2.

Comparative Example 4 The same operation as in Example 2 was carried out except that the methyl vinyl ether-maleic anhydride copolymer was removed from the suspension stabilizer in Example 2.

Comparative Example 5 The same operation as in Example 1 was performed except that polyethylene oxide and ethyl cellulose were removed from the suspension stabilizer of Example 1.

VCM concentration contained in PVC in the discharged slurry obtained according to Examples 1 to 4 and Comparative Examples 1 to 5 above, P after drying
The concentrations contained in the VC products are shown in Table 1.

Claims (1)

[Claims] 1. When vinyl chloride alone or a mixture with other vinyl monomers copolymerizable with vinyl chloride is subjected to suspension polymerization in an aqueous medium at 50° to 70°C using an oil-soluble radical initiator. , as a suspension stabilizer, a water-soluble polymer compound (A) having a specific viscosity of 0.1 or more at 60° C. in a 0.01% by weight aqueous solution;
The surface tension of a wt% aqueous solution at 25°C is 55 dyne.
The absolute viscosity at 25°C of a 5% by weight mixed solution of water-soluble polymer compound (B) of 20/80 (weight mixing ratio) of 20/80 (weight mixing ratio) of ethanol/toluene of 5 cps or more and 3
A suspension polymerization method for vinyl chloride, characterized in that an 8% by weight ethylene dichloride solution at 0°C is used together with an oil-soluble polymer compound (C) which is a true solution. 2. The water-soluble polymer compound (A) has the general formula: X-(CH_2CH_2O)_n-Y (wherein The polymerization method according to claim 1, which is a compound represented by a substituent (n is an integer of 20,000 or more). 3. The polymerization method according to claim 2, wherein X is a hydroxy group and Y is hydrogen. 4 Claim 1, wherein the water-soluble polymer compound (A) is a copolymer of maleic anhydride-methyl vinyl ether
Polymerization method described in section. 5. The polymerization method according to claim 1, wherein the water-soluble polymer compound (A) is alginic acid or sodium alginate. 6. The polymerization method according to claim 1, wherein the water-soluble polymer compound (B) is partially saponified polyvinyl acetate of 82 mol% or less. 7. The polymerization method according to claim 1, wherein the water-soluble polymer compound (B) is methylcellulose. 8. The polymerization method according to claim 7, wherein the methyl cellulose has a methoxy group content of 20% by weight or more and a hydroxypropoxy group content of 4% by weight or more. 9. The polymerization method according to claim 1, wherein the oil-soluble polymer compound (C) is a cellulose derivative in which hydrogen in cellulose is replaced with an alkyl group or an acyl group. 10. The polymerization method according to claim 9, wherein the alkyl group is an ethyl group and the content of ethoxy groups is 44% to 51% by weight. 11 The water-soluble polymer compound (A) is 0.005 to 0.0001 part per 100 parts of the aqueous medium, and the water-soluble polymer compound (A) is
B) is used in an amount of 0.1 to 0.01 part per 100 parts of the aqueous medium, and the oil-soluble polymer compound (C) is used in an amount of 0.1 to 0.001 part per 100 parts of vinyl chloride monomer. A polymerization method according to claim 1.