JPH058753B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a water-soluble thickener and a method for producing the same. More specifically, the present invention relates to a water-soluble thickener comprising starch and acrylonitrile-styrene that exhibits a high thickening effect at low concentrations. [Industrial Application Fields] Thickeners are also called thickening stabilizers, and are used as thickeners, stabilizers, It is widely used in many fields as a thickener, disintegrant, etc. [Prior Art] Conventionally, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, guar gum, carboxymethyl starch, polyethylene oxide, sodium polyacrylate, and the like are known as highly viscous thickeners. However, these did not have sufficient viscosity dilution resistance, especially dilution resistance at an aqueous solution concentration of 1% or less. Another disadvantage is that it forms a so-called ``mamako'' during melting, so it must be dispersed in hot water before melting. In addition, these thickeners had the disadvantage of being expensive. Furthermore, conventionally used anionic modified starch (carboxymethyl starch or starch obtained by graft copolymerization of a monomer having an anionic substituent) did not exhibit sufficient thickening properties. The present invention aims to improve or eliminate the above drawbacks. That is, the object is to provide a thickener that exhibits a high thickening effect even at low concentrations. Yet another object of the present invention is to provide a thickener that exhibits high viscosity at low concentrations over a wide pH range. [Structure of the present invention] As a result of extensive research to achieve the above object, the present inventors have found that a saponified product of a graft copolymer of starch and acrylonitrile-styrene eliminates or improves the above drawbacks. They discovered this and completed the present invention. That is, in the first aspect of the present invention, the molar ratio of starch and acrylonitrile:styrene is in the range of 99.9:
Acrylonitrile-styrene graft copolymer with a ratio of 0.1 to 91:9 [Starch-g-
This invention relates to a thickener made of an alkaline saponified product of polyacrylonitrile (co-styrene). The "starch" used in the present invention includes:
Natural starches such as corn starch, horse starch, wheat starch, sweet potato starch, waxy corn starch, high amylose corn starch, tapioca starch, sago starch; Modified starches such as etherified starch, esterified starch, cross-linked starch, oxidized starch; Corn grits,
Examples include starch-containing powders containing proteins such as corn flour and wheat flour, and in addition to these starches, processed celluloses such as carboxymethyl cellulose, and polysaccharides such as guar gum and mannan can also be contained. In particular, in the present invention, it is preferable to use natural starch such as corn starch as the "starch". Furthermore, it is essential that styrene, which is a comonomer of acrylonitrile, is contained in a molar ratio of acrylonitrile to styrene in the range of 99.9:0.1 to 91:9. This is because the molar ratio of styrene is
This is because even if a graft copolymer having a ratio of more than 91:9 is saponified with an alkali, only a product with a low thickening effect can be obtained. However, the molar ratio of acrylonitrile:styrene is particularly preferably in the range of 99.5:0.5 to 95:5. The thickener of the present invention uses the starch exemplified above,
For example, it can be manufactured by the manufacturing method shown below. That is, in the second aspect of the present invention, starch and acrylonitrile are mixed in the presence of styrene, with a molar ratio of acrylonitrile:styrene ranging from 99.9:0.1 to
The present invention relates to a method for producing a thickener, which comprises graft copolymerizing to give a ratio of 91:9 and saponifying the obtained graft copolymer with an alkali. In the present invention, "acrylonitrile" and "styrene" are both commercially available and can be used as they are without any problem. In the graft copolymerization reaction for producing the thickener in the second aspect of the invention, about 50 parts by weight of a mixture of acrylonitrile and styrene is added to 100 parts by weight of starch.
~500 parts by weight, preferably about 100 to 300 parts by weight, and the polymerization catalyst in a proportion of about 1 to 100 parts by weight, preferably 2 to 30 parts by weight, by conventional methods (for example, MO Weaver
et al., Sta¨rke, 29 (12), 413 (1977)). However, the molar ratio of acrylonitrile:styrene in the graft copolymer ranges from 99.9:0.1 to 91:
9, it is possible to obtain a graft copolymer having a molar ratio of acrylonitrile:styrene that is approximately the same as the molar ratio of acrylonitrile:styrene in the mixture of acrylonitrile and styrene used in the copolymerization reaction. Therefore, the copolymer of the present invention can be produced by using a mixture of acrylonitrile and styrene in which the molar ratio of acrylonitrile to styrene ranges from 99.9:0.1 to 91:9. Further, the polymerization catalyst used in the present invention includes ceric ammonium nitrate, ceric ammonium sulfate, perchloric acid, periodic acid, hydrogen peroxide, ammonium persulfate, sodium persulfate, potassium permanganate, etc. can be mentioned. Note that use of ceric ammonium nitrate is particularly preferred. The graft copolymer composed of starch and acrylonitrile-styrene thus obtained is then saponified with an alkali by a conventional method (see, for example, the above-mentioned literature by MO Weaver et al.). Specifically, for example, the alkali concentration is preferably about 0.5N to 7.5N.
, the temperature preferably ranges from about 85 to 200°C, more preferably from about 100 to 150°C, and the time preferably ranges from about 1 to 3 hours. In any case, the end point of saponification can be easily confirmed when the saponified product changes from reddish brown to pale yellow. The obtained saponified product is neutralized or neutralized, separated and purified, and then dried to obtain the thickener powder of the present invention. However, the thickener of the present invention can be made into various forms other than the above-mentioned powder, such as a film, if desired. In short, its shape can vary depending on the final application. As will become clear in the examples described later, the thickener of the present invention has the following properties: (1) The raw materials are inexpensive, (2) It exhibits a high thickening effect, and (3) It can be easily added to cold water in a short time. It has various features such as: (4) exhibits a high thickening effect over a relatively wide range of PH. Therefore, by utilizing these features, it can be used in a wide range of fields as a thickener for soil conditioners, paints, adhesives, cosmetics, boring, ceramics, architectural spray paints, latex, inkjet, etc. Understand that it can be applied. Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 10 parts of waxy corn starch (anhydrous) and 127 parts of water were placed in a reactor equipped with a stirrer, a reflux condenser, and a nitrogen blowing tube, and stirred at 95° C. for 30 minutes under a nitrogen stream. Next, 9.95 parts (99.5 mol%) of acrylonitrile, 0.098 parts (0.5 mol%) of styrene, and 6.7 parts of ceric ammonium nitrate solution (0.1 mol/cerium ion in 1N nitric acid) were added, and graft polymerization was carried out at 25°C for 2 hours. I let it happen. The reaction solution was dehydrated, washed with water, and dried under reduced pressure to obtain a starch-acrylonitrile-styrene graft copolymer. To 2 parts of this copolymer, 20 parts of a 0.7N aqueous sodium hydroxide solution was added, and the mixture was preheated in a hot water bath, and when it turned reddish brown, it was saponified in an open environment at 100°C for 2 hours.
After saponification, excess sodium hydroxide in the reaction solution is neutralized with glacial acetic acid, methanol is added to precipitate the polymer, washed with methanol, and dried under reduced pressure to obtain the starch-acrylonitrile-styrene graft of the present invention. A thickener powder of an alkali saponified copolymer was obtained. Examples 2 to 4 In place of 9.95 parts (99.5 mol%) of acrylonitrile and 0.098 parts (0.5 mol%) of styrene in Example 1, acrylonitrile was used in Example 2.
9.9 parts (99.0 mol%) and 0.196 parts (1.0 mol%) of styrene, in Example 3, 9.8 parts (98.0 mol%) of acrylonitrile and 0.392 parts of styrene (2.0 mol%),
In Example 4, graft copolymerization, alkali saponification, etc. were carried out in the same manner as in Example 1, except that 9.5 parts (95.0 mol%) of acrylonitrile and 0.98 parts (5.0 mol%) of styrene were used. A powder of alkali saponified styrene graft copolymer was obtained. Comparative Example 1 10 parts of waxy corn starch (anhydrous) and 127 parts of water were placed in a reactor equipped with a stirrer, a reflux condenser, and a nitrogen blowing tube, and stirred at 95° C. for 30 minutes under a nitrogen stream. Next, 10 parts of acrylonitrile and ceric ammonium nitrate solution (in 1N nitric acid,
Add 6.7 parts of cerium ion (0.1 mol/) and 25℃
Graft polymerization was carried out for 2 hours. The reaction solution was dehydrated, washed with water, and dried under reduced pressure to obtain a starch-polyacrylonitrile graft copolymer. The graft copolymer was subjected to alkali saponification in the same manner as in Example 1 to obtain a powder of an alkali saponified product. Example 5 (Viscosity measurement) The dry powders of the alkali saponified graft copolymers obtained in Examples 1 to 4 and Comparative Example 1 were made into an aqueous solution with a content of 0.25% by weight, and filtered through a G1 glass filter. Furthermore, carboxymethyl starch (Comparative Example 2), carboxymethyl cellulose (Comparative Example 3), and polyacrylic acid (Comparative Example 4) were made into an aqueous solution with a content of 1.0% by weight, and filtered through a G1 glass filter. The viscosity of the filtrate obtained in this way is
Measurement was performed using a Bruckfield viscometer at 25°C, No. 4 spindle, and 30 rpm. however,
For products with high viscosity, increase the rotation speed to 12rpm or
Measured at 6 rpm. The results obtained are shown in Table 1.

【table】

〔Effect of the invention〕

The thickener obtained in the present invention has the following advantages. (1) The viscosity in a 0.25% by weight aqueous solution is about 10000, which is about 1.5 to 2 times that of the thickener of Comparative Example 1.
It has a high value of ~13000cP. Furthermore, this value is an order of magnitude higher than that of the conventionally used thickeners of Comparative Examples 2 to 4. (1st
(See table) (2) Within the range of content up to 1% by weight, the increase in viscosity is remarkable as the content increases. For example, at 1% by weight, it exhibits a high viscosity of 75,000 cP, which is about 6 times that of the thickener of Comparative Example 1 (about 13,000 cP), which is not seen in conventional thickeners. (See Figure 1) (3) Shows good thickening properties in a wide pH range of 3 to 13. That is, the minimum value PH3.5
The viscosity is higher than the maximum viscosity of the thickener of Comparative Example 1 (approximately 6400 cP). (See Figure 2)

[Brief explanation of the drawing]

FIG. 1 shows the relationship between viscosity and thickener content. Figure 2 shows the relationship between viscosity and pH.

Claims (1)

[Scope of Claims] 1. A thickener comprising an alkaline saponified graft copolymer of starch and acrylonitrile-styrene having a molar ratio of acrylonitrile:styrene in the range of 99.9:0.1 to 91:9. 2. The thickener according to claim 1, wherein the starch is natural starch. 3. Graft copolymerizing starch and acrylonitrile in the presence of styrene so that the molar ratio of acrylonitrile:styrene is in the range of 99.9:0.1 to 91:9, and saponifying the resulting copolymer with an alkali. A method for producing a thickener. 4. The method for producing a thickener according to claim 3, characterized in that ceric ammonium nitrate is used as a catalyst for graft copolymerization. 5. The method for producing a thickener according to claim 3 or 4, wherein the starch is natural starch.