JP3409020B2 - Dispersant for suspension polymerization - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dispersant for suspension polymerization of vinyl chloride, comprising a modified polyvinyl alcohol. [0002] In the suspension polymerization of vinyl chloride and other vinyl compounds, conventionally, partially saponified polyvinyl alcohol (hereinafter abbreviated as "PVA") and cellulose derivatives such as methylcellulose and carboxymethylcellulose have been used. It has been used as a dispersant. [0003] In the suspension polymerization of vinyl compounds, the dispersant is an important factor that governs the quality of the obtained polymer. Generally, the performance required for the dispersant is (i)
Shows high dispersing power by using a small amount, and has the function of sharpening the particle size distribution of the obtained polymer particles as much as possible,
(Ii) To increase the rate of plasticizer absorption to facilitate processability, and to facilitate removal of vinyl monomers remaining in the polymer particles, and to further prevent the formation of fish eyes in molded articles. Therefore, it has the function of making the polymer particles as uniform and porous as possible, and (iii) the function of producing polymer particles having a high specific gravity of filling. [0004] However, the above-mentioned dispersants for suspension polymerization which have been conventionally used do not satisfy these required performances, and have a low ability to make polymer particles porous, and the plasticizer absorption rate of the polymer is low. , And it is difficult to remove the residual vinyl monomer. SUMMARY OF THE INVENTION An object of the present invention is to overcome the disadvantages of the conventional PVA dispersants for suspension polymerization and to form uniform porous particles when used in the suspension polymerization of vinyl chloride. ,
An object of the present invention is to provide a dispersant capable of producing a polymer having a high plasticizer absorption rate and easily removing residual monomers. SUMMARY OF THE INVENTION The object of the present invention is to provide a method having a carbon number of four.
This is achieved by a dispersant for suspension polymerization of vinyl chloride, comprising a modified polyvinyl alcohol containing the following α-olefin unit in an amount of 1 to 10 mol%. DETAILED DESCRIPTION OF THE INVENTION The modified PVA containing 1 to 10 mol% of an α-olefin unit having 4 or less carbon atoms used in the present invention is a copolymer of vinyl ester and an α-olefin having 4 or less carbon atoms. Obtained by saponifying a polymer. Examples of the vinyl ester include vinyl formate, vinyl acetate, and vinyl propionate. Vinyl acetate is economically preferable. The α-olefin copolymerized with the vinyl ester has 4 or less carbon atoms and includes, for example, ethylene, propylene, n-butene and isobutylene.
Ethylene is preferred from the viewpoint of the water resistance of the obtained polymer film. The content of α-olefin in the modified PVA is 1 to 10
Mol%, preferably 2 to 8 mol%. When the content of the α-olefin is less than 1 mol%, the above-mentioned remarkable effects cannot be obtained. Conversely, when the content exceeds 10 mol%, the water solubility decreases, and the above-mentioned effects can be obtained. Absent. In the modified PVA of the present invention, other functional groups such as a carboxyl group, a lactone group, an amide group, an amino group and the like may be introduced within a range not to impair the purpose of the present invention. The degree of saponification of the modified PVA of the present invention is 50
Preferably it is in the range of mol% to 99 mol%. The degree of polymerization is appropriately selected within the range of 100 to 8,000. When the dispersant comprising the modified PVA of the present invention is used for the suspension polymerization of vinyl chloride, the amount used and the method of the suspension polymerization may be the same as those when a conventional PVA dispersant is used. That is, the amount used is, for example,
JP-A-136089 and JP-A-54-127490
As described in the publication, the content is 0.01 to 5% by weight, preferably about 0.01 to 3% by weight, based on vinyl chloride. When suspension polymerization of vinyl chloride is carried out using the modified PVA dispersant of the present invention, suspension polymer particles having a sharp particle size distribution, being porous, and having a large filling specific gravity. Is obtained. This suspension polymer has the characteristics that the absorption rate of the plasticizer is high, the residual monomer is easily removed, the scattering of powder during handling is small, and the penetration into a molding machine is good. EXAMPLES The modified PVA dispersant of the present invention will be specifically described below with reference to examples. In each example, “parts” are based on weight. Example 1 (Production of Modified PVA) A reaction vessel equipped with a stirrer was charged with 100 parts of vinyl acetate and 70 parts of methanol, and after purging with nitrogen, 1.3 parts of ethylene was injected. A solution in which 2,2'-azobisisobutyronitrile was dissolved in methanol as an initiator was prepared, and nitrogen was replaced by bubbling with nitrogen gas. The temperature of the reaction vessel charged with the monomer was raised, and when the internal temperature reached 60 ° C., an initiator solution was injected to initiate polymerization. After 3 hours, when the conversion reached 45%, the system was cooled. After ethylene removal, the unreacted vinyl acetate monomer was removed under reduced pressure to obtain a methanol solution, to which a NaOH methanol solution was added to perform saponification. The resulting modified PVA has a degree of polymerization of 700 and a degree of saponification of 7
The content was 5 mol% and the ethylene content was 5.0 mol%. (Suspension polymerization of vinyl chloride) In a glass-lined autoclave, 40 parts of deionized water, 0.75 part of a 2% by weight aqueous solution of a PVA-based dispersant, and 0.050% of a 50% by weight toluene solution of diisopropyl peroxydicarbonate were added.
After 09 parts were charged and the inside of the autoclave was degassed until the pressure became 50 mmHg to remove oxygen, 30 parts of a vinyl chloride monomer was charged and the temperature was raised to 57 ° C. with stirring to carry out polymerization. At the start of polymerization, the pressure in the autoclave is 8.5 kg
/ Cm ² G, but 4.5 kg after 7 hours from the start of polymerization.
/ Cm ² G, the polymerization was stopped at this point, the unreacted vinyl chloride monomer was purged, the contents were taken out and dehydrated and dried. Table 1 shows the physical properties and amounts of the PVA-based dispersants.
Table 2 shows the characteristic performance of the obtained vinyl chloride resin. The polymerization yield of vinyl chloride resin is 85% and the average polymerization degree is 10%.
It was 50. The properties of the obtained vinyl chloride resin were evaluated according to the following criteria. (1) Particle size distribution: measured by dry sieve analysis using a metal mesh based on Tyler mesh. (2) Filling specific gravity: Measured according to JIS K6721-1959. (3) Uniformity of particle porosity: 100 parts of vinyl chloride resin, 50 parts of dioctyl phthalate, 1 part of dibutyltin maleate, 1 part of cetyl alcohol, 0.1 part of titanium white.
1 part of a mixture consisting of 25 parts and 0.1 part of carbon black
The mixture was kneaded with a roll at 50 ° C. for a predetermined time (3 minutes, 5 minutes, 7 minutes) to form a sheet having a thickness of 0.2 mm, and light was transmitted through the sheet to make the fish eye contained in the sheet per 100 cm ^2. Was counted. A fish eye that disappears in a shorter time indicates better uniformity of particle porosity. (4) Absorbency of plasticizer: Using a planetary mixer connected to a plastograph, 100 parts of vinyl chloride resin and 50 parts of dioctyl phthalate are charged into a container kept at 80 ° C., and stirred for each hour. The kneading torque for each kneading was recorded and indicated by the kneading time at the point where the kneading torque decreased. The shorter the time, the better the absorbency of the plasticizer. (5) Residual vinyl chloride monomer: A fixed amount of the vinyl chloride resin was dissolved in tetrahydrofuran, and the content of the vinyl chloride monomer in the vinyl chloride resin was determined by gas chromatography. Examples 2 and 3 (Production of modified PVA) Example 1 except that the monomer composition was changed.
By the same operation as described above, two types of modified PVA (degree of saponification,
Table 1 shows the degree of polymerization and the ethylene content. ) Manufactured. (Suspension Polymerization of Vinyl Chloride) Using the modified PVA as a dispersant, suspension polymerization of vinyl chloride was carried out in the same manner as in Example 1, and the obtained vinyl chloride resin was evaluated. The results are shown in Tables 1 and 2. In Example 3, unmodified PVA was prepared in substantially the same manner as in Example 1 except that ethylene was not copolymerized.
A and the modified PVA were used in combination to carry out suspension polymerization of vinyl chloride. Comparative Example 1 (Production of PVA) Unmodified PVA was obtained in substantially the same manner as in Example 1 except that ethylene was not copolymerized. (Suspension Polymerization of Vinyl Chloride) Using the unmodified PVA as a dispersant, suspension polymerization of vinyl chloride was performed in the same manner as in Example 1, and the obtained vinyl chloride resin was evaluated. The results are shown in Tables 1 and 2. [Table 1] [Table 2] From the results in Table 2, it can be seen that when the modified PVA dispersant of the present invention is used alone or in combination with a conventionally known PVA to carry out suspension polymerization of vinyl chloride, uniform porous particles are formed and the plasticizer absorption rate is reduced. It is found that a vinyl chloride polymer which is large and easy to remove the residual monomer can be obtained.

Claims (1)

(57) [Claims] [Claim 1] One α-olefin unit having 4 or less carbon atoms
A dispersant for suspension polymerization of vinyl chloride, comprising a modified polyvinyl alcohol containing from 10 to 10 mol%.