CN103012692B - Method for preparing soybean protein copolymer emulsion - Google Patents

Abstract

The invention relates to natural polymer modification and aims to provide a method for preparing a soybean protein copolymer emulsion. The method comprises the steps of firstly preparing an emulsifier and an initiator by using part deionized water, adding the rest deionized water, soybean protein and a reduction modifier into a reaction kettle, regulating the pH (potential of Hydrogen) value to 8-10 and reacting for 0.5-3h under the conditions of nitrogen protection and mechanical agitation, adding the emulsifier, the initiator, a graft monomer and a functional monomer, adding the rest emulsifier solution, heating to 85-95 DEG C after reacting for 1-3h, reacting for 0.5-3h and obtaining the soybean protein copolymer emulsion. The method provided by the invention has the advantages that the soybean protein modification and the graft polymerization reaction are organically combined, so that the reaction system is simple and the process is simple and easy to control; natural macromolecule is adopted as the raw materials, so that the monomer conversion rate is high and advantages of high efficiency and environmental protection are provided; and the reaction medium is an inorganic alkali aqueous solution, so that the cost is low and the environmental pollution is little.

Description

A kind of preparation method of soybean protein copolymer emulsion

technical field

The invention belongs to the field of natural polymer modification, and in particular relates to a method for synthesizing soybean protein graft copolymer emulsion for surface sizing.

Background technique

Surface sizing technology has many advantages in the papermaking process: (1) The cost of sizing is low, which can alleviate the problems of paper strength decrease, paper machine staining and white water load increase caused by internal sizing agents; (2) It can effectively improve Paper surface properties, such as surface strength, water resistance, two-sidedness, smoothness and printability, etc. Therefore, surface sizing technology has been more and more widely used. At present, there are many kinds of additives used in surface sizing, which can be roughly divided into two categories: natural and synthetic polymers. Synthetic polymer monomers are generally transformed from petrochemical products, and with the increasing shortage of petroleum resources, the world's energy demand continues to increase, and it is an inevitable development trend to find cheap and renewable raw materials to replace petroleum products. However, natural polymers such as starch and soybean protein are commonly found in plants in nature. They are rich in resources, cheap, renewable, and degradable, so they are widely used. At present, soybean protein or starch has become an important raw material for surface sizing agents or adhesives.

Soy protein is an important component of soybeans. Due to the low bonding strength and poor water resistance of soybean protein adhesives, chemical methods are often used to improve the comprehensive performance of soybean protein adhesives.

In the article "Development and characterization of adhesives from soy protein for bonding wood" ("International Journal of Adhesion & Adhesives", 2007, 27, 59), Liu et al. used maleic anhydride to graft and modify soybean protein. Studies have found that MA undergoes a graft reaction with soybean protein through amino and ester bonds. When mixed with polyethyleneimine for modification, the mechanical properties and water resistance properties are significantly improved, and it can be used as a wood adhesive.

He Hongbin et al., in the article "Research on Vinyl Acetate-Soybean Protein Graft Copolymerization Emulsion Adhesive" ("Chemistry and Adhesion", 2007, 29, 146), modified soybean protein with urea and sodium sulfite, and mixed it with vinyl acetate, etc. The composite monomers were grafted and copolymerized under the trigger of APS, and the adhesive emulsion with better performance was prepared, and the cost of raw materials was lower.

In the article "Chemical modification soy protein for wood adhesives" ("Macromolecular Rapid Communications", 2002, 739), Liu et al. introduced a structure similar to dihydroxyphenylalanine into soybean protein, so that soybean protein has a structure similar to that of shellfish. The nature of protein adhesives improves the water resistance and mechanical properties of soy protein.

Chemically grafted modified soybean protein adhesives have excellent cohesiveness and water resistance, but due to the high viscosity of the soybean protein system, the conversion rate of monomers is low at high solid content, which is not mentioned in the above articles The result of monomer conversion in the reaction.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies in the prior art and provide a method for synthesizing soybean protein grafted polymer emulsion with higher conversion rate.

For solving technical problem, solution of the present invention is:

Provide a kind of soybean protein copolymer emulsion preparation method, comprise the following steps:

First prepare emulsifier and initiator with part of deionized water; then add the remaining deionized water, soybean protein and reduction modifier to the reaction kettle, and adjust the pH value with alkaline medium under the condition of nitrogen protection and mechanical stirring Adjust to 8~10, and react at 60~85 ℃ for 0.5~3 h; then add emulsifier, the amount added at this time accounts for 80~100% of the total amount of emulsifier; at the same time, at a rate of 2~5mL/h Add the initiator, graft monomer and functional monomer to the reaction system respectively; after the dropwise addition, add the remaining emulsifier solution; react for 1~3 h and then raise the temperature to 85~95 °C, and then react for 0.5~3 h, obtain the soybean protein graft copolymer emulsion;

In the above reaction system, taking deionized water as a benchmark, the mass ratio of other reactants to deionized water is as follows:

Among the above-mentioned reactants, the emulsifier is a composite emulsifier composed of an anionic emulsifier and a nonionic emulsifier, and the initiator is a peroxide; the reduction modifier is a sulfite or bisulfite; the grafting monomer is Styrene and butyl acrylate; functional monomer is acrylic acid.

In the reaction system of the present invention, the preferred proportioning of various reactants is: the mass ratio of styrene and butyl acrylate is 1/2~2/1; acrylic acid accounts for 1~5% of the grafted monomer total amount; The mass ratio of protein to the total amount of grafted monomers is 1/3~1/1.

The reducing modifier of the present invention is sodium sulfite, potassium sulfite, sodium bisulfite or potassium bisulfite.

The alkaline medium of the present invention is ammonia solution.

The anionic emulsifier of the present invention is sodium dodecylbenzenesulfonate (SDBS) or sodium dodecylsulfonate (SDS), and the nonionic emulsifier is nonylphenol polyoxyethylene ether (OP-10) .

The mass ratio of the anionic emulsifier in the present invention to the nonionic emulsifier is 1/3-3/1.

The initiator described in the present invention is ammonium persulfate or persulfuric acid.

The initiator described in the present invention accounts for 0.5-1% by mass of the total amount of grafted monomers.

The principle of the present invention is: in the modification of soybean protein, sulfite and bisulfite are used as reducing agents to break the protein disulfide bond, fully extend the protein molecular chain, and increase the free radical active site on the molecular chain at the same time. concentration. The organic combination of soybean protein modification and free radical polymerization can expose the active sites of soybean protein, initiate the polymerization reaction of monomers containing double bonds or cause double-radical coupling termination with polymer active chains, and generate graft copolymers . The invention adopts mechanical stirring, and the monomer and the initiator are continuously added dropwise, which is favorable for the active point on the protein molecular chain to fully react with the monomer.

The present invention has the following beneficial effects:

1. The present invention organically combines soybean protein modification and graft polymerization, has simple reaction system, simple process and easy control.

2. The present invention uses natural macromolecules as raw materials, and the monomer conversion rate is relatively high, which can make the monomer conversion rate reach 76%~81%. It also has the advantages of high efficiency and environmental protection.

3. The reaction medium used in the present invention is an aqueous solution of inorganic alkali, which has low cost and little environmental pollution.

Detailed ways

The present invention will be described in detail below through specific examples.

Example 1

In the reaction system, the total amount of soybean protein/grafting monomer (styrene and butyl acrylate) is 1/1, the mass ratio of styrene monomer and acrylate monomer is 1/1, and the functional monomer acrylic acid accounts for 2.5% of the total monomer. The mass ratio of anionic emulsifier to nonionic emulsifier in the emulsifier is 1/1, and the total amount of initiator/grafting monomer (styrene and butyl acrylate) is 1%. The mass parts of each substance are:

Prepare a certain mass fraction of 12% mixed emulsifier solution and 4% initiator KPS solution with some deionized water. First, add the remaining deionized water, soybean protein and sodium sulfite reduction modifier into the reaction kettle, and adjust the pH value of the system to 10.0 with 28% ammonia solution under the condition of nitrogen protection and mechanical stirring. React at 70°C for 1 h, then add 80% of the total amount of 12% mixed emulsifier aqueous solution, and drop the monomer mixture (containing St, BA, AA) and 4% KPS aqueous solution, add the remaining emulsifier solution after the dropwise addition, react for 2 hours and then raise the temperature to 90°C, stop the reaction after 1 hour to obtain the soybean protein graft copolymer emulsion. During the whole process, the pH value of the system was guaranteed to be 10.0, and the monomer conversion rate of the obtained product was 76%.

Example 2

In the reaction system, the total amount of soybean protein/grafting monomer (styrene and butyl acrylate) is 1/1, the mass ratio of styrene monomer and acrylate monomer is 1/1, and the functional monomer acrylic acid accounts for 5% of the total monomer. The mass ratio of anionic emulsifier to nonionic emulsifier in the emulsifier is 1/1, and the total amount of initiator/grafting monomer (styrene and butyl acrylate) is 1%. The mass parts of each substance are:

Prepare a certain mass fraction of 15% mixed emulsifier solution and 1% initiator APS solution with some deionized water. First, add the remaining deionized water, soybean protein and sodium bisulfite reduction modifier into the reaction kettle, and adjust the pH value of the system to 9.0 with 28% ammonia solution under the condition of nitrogen protection and mechanical stirring. React at 85°C for 0.5h, then add 90% of the total amount of 15% mixed emulsifier aqueous solution, and drop the monomer mixture (including St, BA, AA) at a rate of 5.0mL/h and 5.0mL/h respectively and 1% APS aqueous solution, after the dropwise addition, add the remaining emulsifier solution, react for 1.5 hours and then raise the temperature to 90°C, stop the reaction after 1.5 hours to obtain soybean protein graft copolymer emulsion. During the whole process, the pH value of the system was guaranteed to be 9.0, and the monomer conversion rate of the obtained product was 80%.

Example 3

In the reaction system, the total amount of soybean protein/grafted monomer (styrene and butyl acrylate) is 1/2, the mass ratio of styrene monomer to acrylate monomer is 1/2, and the functional monomer acrylic acid accounts for 1/2 of the grafted monomer. 1% of the total monomer. The mass ratio of the anionic emulsifier to the nonionic emulsifier in the emulsifier is 3/1, and the total amount of the initiator/grafting monomer (styrene and butyl acrylate) is 0.5%. The mass parts of each substance are:

Prepare a certain mass fraction of 22% mixed emulsifier solution and 2% initiator APS solution with some deionized water. First, add the remaining deionized water, soybean protein and reduction modifier potassium sulfite to the reaction kettle, and adjust the pH value of the system to 8.0 with 28% ammonia solution under the condition of nitrogen protection and mechanical stirring. React at 80°C for 1 h, then add 100% of the total amount of 22% mixed emulsifier aqueous solution, and drop the monomer mixture (containing St, BA, AA) and 2% APS aqueous solution, after the dropwise addition, react for 1 hour, raise the temperature to 85°C, and react for 3 hours to obtain soybean protein graft copolymer emulsion. During the whole process, the pH value of the system was guaranteed to be 8.0, and the monomer conversion rate of the obtained product was 79%.

Example 4

In the reaction system, the total amount of soybean protein/grafted monomer (styrene and butyl acrylate) is 1/3, the mass ratio of styrene monomer to acrylate monomer is 2/1, and the functional monomer acrylic acid accounts for 1/3 of the grafted monomer. 2% of the total monomer. The mass ratio of the anionic emulsifier to the nonionic emulsifier in the emulsifier is 1/3, and the total amount of the initiator/grafting monomer (styrene and butyl acrylate) is 0.8%. The mass parts of each substance are:

Prepare a certain mass fraction of 22% mixed emulsifier solution and 3% initiator APS solution with some deionized water. First, add the remaining deionized water, soybean protein and reduction modifier potassium bisulfite to the reaction kettle, and adjust the pH value of the system to 9.0 with 28% ammonia solution under the condition of nitrogen protection and mechanical stirring. React at 60°C for 3 hours, then add 80% of the total amount of 22% mixed emulsifier aqueous solution, and drop the monomer mixture (containing St, BA, AA) and 3% APS aqueous solution, after the dropwise addition, add the remaining emulsifier solution, react for 3 hours and then raise the temperature to 95°C, and react for 0.5 hours to obtain soybean protein graft copolymer emulsion. During the whole process, the pH value of the system was guaranteed to be 9.0, and the monomer conversion rate of the obtained product was 81%.

The present invention may be embodied in other specific forms without departing from the spirit and main characteristics of the invention. Therefore, no matter from which point of view, the above-mentioned experimental scheme of the present invention can only be considered as explanation of the present invention and can not limit the present invention, and the claims have pointed out the scope of the present invention, and above-mentioned description does not point out the scope of the present invention Therefore, any changes within the meaning and scope equivalent to the claims of the present invention should be considered to be included in the scope of the claims.

Claims (8)

1. a soybean protein copolymer emulsion preparation method, is characterized in that, comprises the following steps:

First with part deionized water preparation emulsifying agent and initiator; Then in reactor, add remaining deionized water, and soybean protein, modified with reduction agent, under nitrogen protection and mechanical stirring condition, pH value is adjusted to 8 ~ 10 with alkaline medium, and reacts 0.5 ~ 3 h at 60 ~ 85 DEG C; Then add emulsifying agent, add-on now accounts for 80 ~ 100% of emulsifying agent total amount; In reaction system, add initiator, grafted monomer and function monomer respectively with the rate of addition of 2 ~ 5 mL/h simultaneously; After dropwising, then add remaining emulsifier solution; After reaction 1 ~ 3 h, be warming up to 85 ~ 95 DEG C, then react 0.5 ~ 3 h, obtain soybean protein copolymer emulsion;

In above-mentioned reaction system, taking deionized water as benchmark, the mass ratio of other reactant and deionized water is as follows:

In above-mentioned reactant, emulsifying agent is the mixed emulsifier of anionic emulsifier and nonionic emulsifying agent composition, and initiator is peroxide; Modified with reduction agent is sulphite or hydrosulphite; Grafted monomer is vinylbenzene and butyl acrylate; Function monomer is vinylformic acid.

2. method according to claim 1, is characterized in that, in described reaction system, the preferred proportioning of various reactants is: vinylbenzene and butyl acrylate mass ratio are 1/2 ~ 2/1; Vinylformic acid accounts for 1 ~ 5% of grafted monomer total amount; The mass ratio of soybean protein and grafted monomer total amount is 1/3 ~ 1/1.

3. method according to claim 1, is characterized in that, described modified with reduction agent is S-WAT, potassium sulfite, sodium bisulfite or Potassium hydrogen sulfite.

4. method according to claim 1, is characterized in that, described alkaline medium is ammonia soln.

5. method according to claim 1, is characterized in that, described anionic emulsifier is Sodium dodecylbenzene sulfonate or sodium laurylsulfonate, and described nonionic emulsifying agent is polyoxyethylene nonylphenol ether.

6. method according to claim 1, is characterized in that, the mass ratio of described anionic emulsifier and nonionic emulsifying agent is 1/3 ~ 3/1.

7. method according to claim 1, is characterized in that, described initiator is ammonium persulphate or persulfuric acid.

8. method according to claim 1, is characterized in that, described initiator accounts for the mass ratio 0.5 ~ 1% of grafted monomer total amount.