JPS6144085B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a graft copolymer using starch as a backbone polymer. This invention relates to a method of graft copolymerizing monomers to obtain a graft copolymer with high graft efficiency. Conventionally, methods using ceric nitrate, persulfate, etc. as initiators or methods using radiation have been known as methods for graft copolymerizing styrene onto starch.
No method has been found that satisfies both grafting efficiency. Furthermore, when radiation is used, both the grafting rate and the grafting efficiency are improved, but it is not practical due to manufacturing costs. In order to solve the above problems, the present inventors
As a result of extensive research, we found that by introducing a half-esterified maleic acid group into the hydroxyl group of starch by reacting it with maleic anhydride, this maleic acid group showed grafting activity, and it was found that this maleic acid group showed grafting activity using a normal polymerization initiator. have also found that styrene, its derivatives, or styrene and other polymer monomers can be efficiently graft-polymerized. This is because the maleic acid group introduced into starch has an electron-withdrawing double bond and forms a complex with an electron-donating monomer such as styrene, increasing the speed of graft polymerization and extremely high grafting efficiency. This is thought to be due to the fact that grafting is possible even when using a normal polymerization initiator that is unlikely to cause graft polymerization. That is, the present invention uses starch as a backbone polymer,
When graft copolymerizing at least one monomer selected from styrene and its derivatives alone or together with at least one other polymerizable monomer, the starch is converted into its maleic acid half ester, and then the monomer component is added to the starch. The purpose of the present invention is to provide a method for producing graft copolymerization using starch as a backbone polymer, which is characterized by carrying out a graft copolymerization reaction. A graft copolymer is obtained. According to the method of the present invention, starch is reacted with maleic anhydride to obtain maleic acid half ester starch, and the monomer component is graft-polymerized onto this using a conventional polymerization initiator in a solvent. A graft copolymer having starch as a backbone polymer is obtained by this method. Starches used as the backbone polymer in the method of the present invention include starches such as potato starch, sweet potato starch, corn starch, waxy corn starch, high amylose corn starch, wheat starch, rice starch, tapioca starch, and sago starch; Examples include starch derivatives such as starch, crosslinked starch, etherified starch, and esterified starch. The method for producing maleic acid half ester starch is known and can be easily produced according to a conventional method, but the degree of substitution per glucose unit is 0.01 to 3.00, preferably 0.03 to 3.00, from the viewpoint of production cost and manufacturing process.
Set it to 0.20. In particular, those with a low degree of substitution (e.g.
0.15), it is advantageous to react maleic anhydride in an aqueous dispersion of starch using a caustic catalyst (as described in US Pat.
(See No. 2461139). In the method of the present invention, the monomer component is selected from styrene and alkylstyrenes such as α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, sodium p-styrenesulfonate, and styrene derivatives such as vinylpyridine. using at least one monomer of
Furthermore, along with these styrene or styrene derivatives, maleic anhydride, methacrylic acid and its esters, acrylic acid and its esters, vinylidene chloride, vinyl acetate, vinyl chloride, butadiene, acrylonitrile, methacrylonitrile,
At least one other polymerizable monomer such as methyl vinyl ketone may be graft copolymerized. The polymerization reaction is usually carried out using an organic solvent such as dimethyl sulfoxide, formamide, dimethyl formamide, acetone, tetrahydrofuran, acetonitrile, dimethyl acetamide, tetramethyl sulfone, or nitrobenzene, water, or a mixture thereof, preferably water. Using a polymerization initiator, the temperature at which the used polymerization initiator separates and generates radicals under normal pressure, usually 30~
Perform at 100℃. Examples of the polymerization initiator used include peroxides such as benzoyl peroxide, lauroyl peroxide, and acetyl peroxide, azo compounds such as azobisbutylnitrile, persulfates such as potassium persulfate and ammonium persulfate, and hydrogen peroxide. Examples include redox initiators such as Mohr's salt, persulfate-sulfite, and benzoyl peroxide-dimethylaniline. The ratio of maleic acid half ester starch to monomer components, their concentrations relative to the solvent, and the concentration of the polymerization initiator at the time of starting the polymerization reaction can be appropriately selected depending on the desired object. The starch-polystyrene graft copolymer obtained by the present invention has excellent compatibility with thermoplastic polymers and can be used for biodegradable plastics and the like. Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto. The test methods used for performance evaluation in each example are as follows. (1) Grafting rate, grafting efficiency, total polymerization rate After carrying out the specified reaction, the polymer and graft copolymer that did not undergo graft polymerization were precipitated using excess methanol as a precipitant, and washed with methanol. After drying, extract with acetone for 10 hours to remove the polymer that did not undergo graft polymerization.
It was calculated according to the following formula. Grafting rate (%) = starch weight increase after reaction/starch weight before reaction x 10
0 Grafting efficiency (%) = Weight increase of starch after reaction / Total weight of polymer x 100 Total polymerization rate (%) = Weight of polymerized monomer / Weight of monomer x 100 Example 1 500 g of corn starch ( (as anhydride) and, under stirring, add sodium hydroxide.
While maintaining the pH at 9.0, 65 g of maleic anhydride powder was added in portions at 10°C. The precipitate was washed with methanol, collected by filtration, and dried at 50°C to obtain a degree of substitution of 0.13.
The maleic acid half ester starch sodium salt was obtained. 18.6 g of this maleic acid half ester starch (as anhydride) and 45 g of styrene were dispersed in 20 ml of water, and various concentrations of ammonium persulfate were added as a polymerization initiator, followed by stirring at 60° C. for 2 hours under a nitrogen atmosphere. Wash the precipitate with methanol, collect by filtration, and heat at 50°C.
was dried to obtain a maleic acid half ester starch-polystyrene graft copolymer. The relationship between the concentration of ammonium persulfate and the performance of the obtained copolymer is shown in the table on the next page. 【table】

Claims (1)

[Claims] 1 Starch maleic acid half ester having a degree of substitution of 0.01 to 3.00 is used as a backbone polymer, and at least one monomer selected from styrene and its derivatives is craft-copolymerized with the starch maleic acid half ester alone or together with at least one other polymerizable monomer. A method for producing a starch-polystyrene graft copolymer characterized by: