KR20010048278A - Process for Preparing Soy Protein Coated Oil-resistant Paper - Google Patents

Abstract

PURPOSE: A process for preparing oil-proof coating paper by coating soybean protein which is environmentally benign and has oil resistance on a surface of general-purpose paper is provided. Thereby the coating paper shows low permeability to oil and can be widely used for oil-proof food packing paper. CONSTITUTION: The oil-proof coating paper is prepared by a process consisting of: obtaining soybean protein emulsion by dissolving soybean protein in a solvent, adding a plasticizer, a salt and a preserving agent and agitating; obtaining a soybean protein solution by adjusting the pH of a solution to 8 to 11; and coating the soybean protein solution to paper and drying.

Description

Process for Preparing Soy Protein Coated Oil-Resistant Paper Using Soy Protein

The present invention relates to a method for producing an oil-resistant coated paper using soy protein. More specifically, the present invention obtains a soy protein solution composed of soy protein, a plasticizer, a salt and a preservative, adjusts the pH, and then coats and dries it on paper to prepare an oil-resistant coated paper and a coated paper produced therefrom. It is about.

Corn protein, wheat protein, soy protein, and the like are known as protein sources that can produce environmentally friendly protein films. Soy protein has good film formability and is water-soluble and biodegradable due to the hydrophilic groups on the surface of the protein.It has been used as a food wrap, for example, in yuba in Japan and toupoopy in China. In Malaysia, 'Fuchum'. Such a soy protein-based film shows much better oxygen barrier properties than corn protein or wheat protein, and has about 300 to 2,000 times higher oxygen barrier properties than polymers produced from petroleum such as low density polyethylene or polystyrene. In addition, most raw polymers are three times more expensive than petrochemically produced plastics, and they are not widely commercialized because they are severely restricted in use, while isolated soy protein is close to plastics in terms of physical properties and price. In terms of commercialization, it has the greatest advantage. However, when the film is manufactured by using the separated protein alone, the production of the film is considerably restricted due to weak mechanical properties, and even if the film is manufactured, it has been difficult to fully exhibit the oil resistance function.

Various studies have been conducted to develop packaging films using soy protein. For example, US Pat. No. 5,543,164 (Krochta et al.) Has made water-soluble proteins into insoluble proteins through chemical and enzymatic treatment. A method of preparing a film by mixing the same with a fat is disclosed. US Pat. No. 4,997,682 (Coco et al.) Adds soy protein to a synthetic binder, thereby improving the tearing of paper by the synthetic adhesive. To smooth the process and improve the gloss and smoothness of the product. However, in the former case, the process of chemical and enzymatic treatment is complicated, and the reaction time is long. In the latter case, since synthetic polymer is used as an adhesive, compared to a packaging material using only pure natural materials. There is a disadvantage of poor environmental friendliness.

Therefore, the need to overcome the shortcomings of the inventions using soy protein, and to develop a packaging material using soy protein having properties similar to those of synthetic polymers and price competitiveness.

Accordingly, the present inventors have made efforts to develop environmentally friendly, excellent physical properties and low-cost packaging materials, and as a result, coating soy protein on paper having potential as a general purpose, safety, and eco-friendly food packaging material, not only has excellent mechanical properties. It was confirmed that the low permeability with respect to fats and oils, the present invention was completed.

After all, the main object of the present invention is to provide a method for producing oil-resistant coated paper using soy protein that is environmentally friendly and oil-resistant.

Another object of the present invention is to provide a soy protein / paper coated paper produced from the electrical manufacturing method.

1 is a chart showing the maintenance permeability of the coated paper and polyethylene coated paper using soy protein of various thicknesses over time.

Figure 2 is a chart showing the maintenance permeability over time of coated paper using soy protein prepared by varying the amount of plasticizer added.

Method for producing an oil-resistant coating paper using soy protein of the present invention is a step of dissolving soy protein in a solvent, and then adding a plasticizer, salt and preservative and stirring to obtain a soy protein emulsion (emulsion); Adjusting the pH of the electric soy protein emulsion to 8 to 11 to obtain a soy protein solution; And coating the soy protein solution on paper and drying.

Hereinafter, the manufacturing method of the coated paper using the soy protein of the present invention will be described in more detail by dividing each step.

Step 1 : Obtaining Soy Protein Emulsion

Soy protein is dissolved in a solvent, and then plasticizer, salt and preservative are added and stirred to obtain soy protein emulsion:

At this time, the solvent may be water, alcohol or a mixed solvent thereof, and the amount of soy protein added to the solvent is 1 to 50 parts by weight, preferably 2 to 30 parts by weight based on 100 parts by weight of the solvent. When the amount of soy protein dissolved in the solvent is less than 1 part by weight, it is not preferable because oil resistance is lowered. When it exceeds 50 parts by weight, it is not only inferior in workability but also in terms of cost.

As the plasticizer, glycerin, 1,2,6-hexanetriol, 1,4-butanediol, 1,4-butanediol, cellulosemethylether and diadia Cetine, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol polyethylene glycol, polypropylene glycol, polyethylene Propylene glycol, polyethylene glycol fatty acid ester, ethanol, glycerol monoacetate, glycerol diacetate, glycerol triacetate, lactic acid lactic acid, mannitol, polyvinyl alcohol, sodium arginate, sodium celluloseglyconate, sodium diethylsuccinate 1 to 40 parts by weight of one or more plasticizers selected from the group consisting of potassium diethylsuccinate, sorbitan, sorbitol, triethanolamine, urea, etc. Parts, preferably 2 to 30 parts by weight is added. If the amount of plasticizer added is less than 1 part by weight, the coated surface is not easily broken, and if it exceeds 40 parts by weight, it is not preferable because the oil resistance and tensile strength of the coated paper are lowered.

And, salts include magnesium chloride (MgCl ₂ ), calcium chloride (CaCl ₂ ), manganese chloride (MnCl ₂ ), ferrous chloride (FeCl), ferric chloride (FeCl ₂ ), copper chloride (CuCl ₂ ), zinc chloride (ZnCl ₂₎ ), Sodium chloride (NaCl), potassium chloride (KCl), magnesium sulfate (MgSO ₄ ), calcium sulfate (CaSO ₄ ), manganese sulfate (MnSO ₄ ), iron sulfate (FeSO ₄ ), copper sulfate (CuSO ₄ ), zinc sulfate (ZnSO ₄ ), at least one salt selected from the group consisting of sodium sulfate (Na ₂ SO ₄ ), potassium sulfate (K ₂ SO ₄ ), and the like, is 0.01 to 10 parts by weight, preferably 0.01 to 5, based on 100 parts by weight of the solvent. Parts by weight is added. The salt added serves to improve the stability of the soy protein emulsion. Therefore, when the amount of salt is less than 0.01 parts by weight, the salt bridge effect is not sufficient, so that the emulsion is unstable and a uniform coating cannot be obtained. When the amount is more than 10 parts by weight, a gel is formed by a large amount of salt. You won't get it.

Finally, preservatives include benzoic acid, sodium benzoate, ethyl p-oxybenzoate, propyl p-oxybenzoate, and paraoxybenzoic acid isopropyl. p-oxybenzoate, butyl p-oxybenzoate, i-butyl p-oxybenzoate, calcium propionate, sodium propionate, dehydroacetic acid ), At least one preservative selected from the group consisting of sodium dehydroacetate, sorbic acid, potassium sorbinate, and the like, with respect to 100 parts by weight of the solvent, preferably 0.01 to 10 parts by weight, 0.01 to 5 parts by weight is added. The function of the preservative serves to prevent the growth of microorganisms on the biodegradable soy protein coated paper. When the amount of the preservative added is less than 0.01 part by weight, it does not function as a preservative, such as mold growth in the rainy season. If it exceeds, there is a problem that the function of the coated paper is lowered, which is not preferable.

When bubbles are present in the coating liquid, pinholes are formed on the surface of the coated paper to form passages through which oil and fat can pass. Degassing and defoaming are essential in preparing the coating liquid. Stirring should be carried out at 50 ° C. to 150 ° C., but if the temperature at the time of stirring does not reach 50 ° C., the viscosity of the solution is high, so that the removal of bubbles is insufficient. Rather, the bubble is aggravated.

Second Step : Obtaining Soy Protein Solution

A soy protein solution is obtained by adjusting the pH of the soy protein emulsion obtained above to 8-11: soy protein is precipitated at an isoelectric point of pH = 4.5, in order to increase the solubility of soy protein. To 11 should be adjusted. If the pH does not reach 8, the solubility of soy protein is insufficient to obtain a uniform coating, and if the pH exceeds 11, the soy protein is hydrolyzed, so that the tensile strength of the coated paper becomes poor. At this time, the pH is controlled by adding an aqueous solution of a metal hydroxide or a metal hydroxide such as sodium hydroxide while checking the pH of the solution by using conventional pH checking means such as pH-meter, litmus test paper, and indicator.

Third Step : Preparation of Coated Paper by Coating and Drying Soy Protein Solution

A solution containing the soy protein was coated on paper and then dried to prepare coated paper using soy protein:

At this time, the coating of the solution is coated on a paper having a basis weight of 20 to 40g / ㎡, preferably 25 to 35g / ㎡ with a coating bar so that the thickness of the coated soy protein is 1 to 10kg / ream (278m ² ). If the basis weight of the paper is 28 or less, the tensile strength of the coated paper is low, so that breakage occurs frequently during the process, and the smooth operation is not disturbed, and it is not suitable as the coated paper. In addition, when the basis weight is more than 40, the convenience or appearance of the product packaging is degraded, the amount of waste is also increased. Subsequently, drying is performed by hot air drying, heat drum drying or infrared drying, which are commonly used in the art.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are only for illustrating the present invention in more detail, it will be apparent to those skilled in the art that the scope of the present invention is not limited to these examples.

Example 1 Preparation of Coated Paper Using Soy Protein

Example 1-1 Preparation of Coated Paper Using Soy Protein (I)

First, 100 g of powdered soy protein was dissolved in 1 L of distilled water, 60 ml of a polyethylene glycol 400 and glycerin 1: 1 (v / v) mixed solution, a plasticizer, 5 g of calcium chloride, and 0.5 g of sodium dehydroacetate were added as a preservative, 85 After stirring for 20 minutes at ℃ to obtain an aqueous soy protein solution, the pH was adjusted to 10 by adding 0.1M aqueous sodium hydroxide solution while measuring the pH of the aqueous solution by pH-meter. Next, the soy protein solution with the electric pH adjusted was coated on a paper of 35 g / m ² basis weight with a thickness of 2.5, 5.6 and 6.4 kg / ream (278 m ² ), respectively, using a hot air dryer for 1 hour at 100 ° C. Drying made coated paper.

For each coated paper, tensile strength and elongation were measured according to the evaluation method of ASTM D882-88 using a universal testing machine (see Table 1).

As shown in Table 1 below, the coated paper using soy protein is inferior in tensile strength, but when the coating thickness is 2.5kg / ream or more, it can be confirmed that the coated paper is equal or more than the tensile strength of the polyethylene coated paper.

Table 1 : Effect of Coating Thickness on Tensile Strength of Coated Paper Using Soy Protein

Paper type sample water Tensile Strength (MPa) ^* 35g basis weight original paper (Kyesung Paper Co., Ltd.) 10 47 ± 2.4 Soy Protein Coated Paper (2.5kg / ream) 10 34 ± 2.2 Soy Protein Coated Paper (5.6kg / ream) 10 35 ± 1.9 Soy Protein Coated Paper (6.4kg / ream) 10 40 ± 2.4 Soy Protein Film (2mm) 10 6 ± 2.1 Polyethylene coated paper 10 34 ± 2.5

* The values of tensile strength are expressed as mean value and standard deviation.

Example 1-2 Preparation of Coated Paper Using Soy Protein (II)

A coated paper was prepared in the same manner as in Example 1-1, except that 20, 60, and 100 ml of a mixed solution of polyethylene glycol 400 and glycerin in a 1: 1 ratio (v / v) as a plasticizer were added, respectively. Tensile strength and elongation were measured (see Table 2).

Plasticizers function to prevent coating paper from breaking, which can occur when soybean meal is used. As shown in Table 2 below, the tensile strength of the coated paper was found to be highest when the plasticizer was added at a rate of 60 ml with respect to 1 L of solvent. This is because if the concentration of the plasticizer is too high, the plasticizer will dominate the physical properties of the coated paper. This is because the tensile strength and elongation are lowered.

Table 2 : Effect of Plasticizer on Tensile Strength of Coated Paper Using Separate Soy Protein

Amount of plasticizer added sample water Tensile Strength (MPa) expansibility(%) 20 ml 10 35 ± 6.7 5.1 ± 0.8 60 ml 10 36 ± 2.3 6.3 ± 0.7 100 ml 10 28 ± 5.3 6.2 ± 0.7

Example 2 Maintenance Permeability Test

Example 2-1 : retention permeability according to the thickness of soy protein coating

For coated paper prepared in the same manner as in Example 1-1, except that the thickness of the soy protein coating was 2.2 kg / ream, 2.4 kg / ream, 2.5 kg / ream and 3.1 kg / ream, Maintenance permeability was measured by the measuring method of 507 (Tapi, 1991) (see Fig. 1). The thickness of the coating can be adjusted by using a coating bar, and coated using a coating bar 7, 12, 14 and 28, respectively.

As shown in Figure 1, the soy protein coated paper is not only significantly less than the permeability of the polyethylene coated paper, the thickness of the coated soy protein was confirmed that the maintenance blocking effect is improved.

Example 2-2 : Permeability maintenance according to the concentration of the plasticizer

For the coated paper prepared in Example 1-2, the retention permeability was measured in the same manner as in Example 2-1 (see Fig. 2).

As shown in FIG. 2, the coated paper prepared by adding 60 ml of plasticizer had excellent retention barrier until the first 4 hours, but after that, the coated paper prepared by adding 100 ml of plasticizer had excellent retention barrier. However, all of the coated papers prepared with the addition of 20, 60, and 100 ml of plasticizer showed excellent retention barrier properties compared to polyethylene coated papers.

Comparative Example 1 Effects of Bubble Formation on Oil Permeability of Coated Paper Using Soy Protein

The coated paper produced in Example 1-1 was coated with the same method as in Example 1-1, except that coated soybean protein coating had a thickness of 2.5 kg / ream and the temperature at the time of stirring was 40 ° C. Oil permeability was measured to investigate the effect of bubble formation on oil permeability (see Table 3).

As shown in Table 3 below, the formation of bubbles is affected by the pretreatment process of the solution, and the oil permeability of the separated soy protein coated paper depends on the degree of bubbles. This is because, when bubbles are present in the coating liquid, pinholes are formed on the surface of the coated paper to form passages through which oil and fat can pass. Therefore, degassing and defoaming in the preparation of the coating solution is an essential element, which is closely related to the foaming ability of the coating solution, the bubble formation in the separated soy protein coated paper can be controlled through the preparation of the coating solution.

Table 3 : Bubble Formation of Separated Soy Protein Coating [Liquid]

Heat Treatment (Separated Soy Protein 2.5kg / ream) sample water Number of bubbles / 10ml Heat treatment (85 ℃) 10 none No heat treatment (40 ℃) 10 5

Example 3 Retention Permeability According to Paper Type

Soy protein prepared in the same manner as in Example 1-1, with 1 L of distilled water and 100 g of soy protein, 60 ml of polyethylene glycol 400 and glycerin 1: 1 (v / v) mixed solution, 5 g of calcium chloride, and 3 g of sodium dehydroacetate. an aqueous solution, as prepared by using the bar 14 once the coating is coated on the three sheet of Co. gyeseong basis weight of the paper 35g / m ^2, the basis weight of Co. signal paper 32g / m ^2, and Co. the basis weight of the signal paper 30g / m ² coated paper, polyethylene Coated paper and signal paper basis weight 32g / m ² base paper was compared according to the retention permeability test method of Example 2-1 (see Table 4).

As shown in Table 4 below, the maintenance permeability of the coated paper decreased as the basis weight of the paper increased, and the maintenance permeability rapidly increased with time when the coating paper was not coated. On the other hand, even when compared to the polyethylene coating product was confirmed to be excellent in terms of maintenance permeability.

Table 4 : Comparative test of oil permeability of coated paper (oil permeability,%)

Gyeseong paper 35g / m ² base paper Signal paper 32g / m ² paper Signal paper 30g / m ² paper Periethylene Coated Paper Signal Paper 32g / m ² Uncoated Base 1hr 0.00 0.00 0.91 0.00 0.19 2hr 0.00 0.00 0.00 0.00 2.05 3hr 0.00 1.09 5.52 5.30 1.99 4hr 0.48 2.16 1.87 2.30 15.07 5hr 2.10 9.81 13.69 15.20 23.39 6hr 1.33 4.28 9.38 24.10 46.79 Average thickness of the ground (um) 50.62 67.50 59.58 67.50 Ground weight (g / m ² ) 35.00 32.00 30.00 32.00 Raw paper density (g / cm ³ ) 0.691 0.474 0.503 0.474

As described and demonstrated in detail above, the present invention obtains a soy protein solution composed of soy protein, a plasticizer, a salt and a preservative, adjusts pH, and then coats it on paper and dries to prepare an oil-resistant coated paper, and to prepare therefrom. To provide coated paper. The oil-resistant coated paper using the soy protein of the present invention not only has excellent mechanical properties such as tensile strength, but also shows low permeability to fats and oils, and thus can be widely used as an oil-resistant food packaging paper.

Claims (10)

(Iii) dissolving soy protein in a solvent, followed by adding and stirring a plasticizer, salt and preservative to obtain soy protein emulsion; (Ii) adjusting the pH of the electric soy protein emulsion to 8 to 11 to obtain a soy protein solution; And, (Iii) A method of producing an oil-resistant coated paper, comprising the step of coating an electric soy protein solution on paper and drying it. The method of claim 1 The solvent is characterized in that the water, alcohol or a mixed solvent thereof Method for producing oil-resistant coated paper. The method of claim 1, The amount of soy protein to be dissolved is 1 to 50 parts by weight based on 100 parts by weight of the solvent. Method for producing oil-resistant coated paper. The method of claim 1 Plasticizers include glycerin, 1,2,6-hexanetriol, 1,4-butanediol, 1,4-butanediol, cellulosemethylether, and diacetin diacetin, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol polyethylene glycol, polypropylene glycol, polyethylene propylene glycol (polyethylenepropylene glycol), polyethylene glycol fatty acid ester, ethanol, glycerol monoacetate, glycerol diacetate, glycerol triacetate, lactic acid ), Mannitol, polyvinyl alcohol, sodium arginate, sodium celluloseglyconate, sodium diethylsuccinic acid (p) At least one plasticizer selected from the group consisting of otassium diethylsuccinate, sorbitan, sorbitol, triethanolamine and urea is added in an amount of 1 to 40 parts by weight based on 100 parts by weight of the solvent. Characterized by Method for producing oil-resistant coated paper. The method of claim 1 Salts include magnesium chloride (MgCl ₂ ), calcium chloride (CaCl ₂ ), manganese chloride (MnCl ₂ ), ferrous chloride (FeCl), ferric chloride (FeCl ₂ ), copper chloride (CuCl ₂ ), zinc chloride (ZnCl ₂ ), Sodium chloride (NaCl), potassium chloride (KCl), magnesium sulfate (MgSO ₄ ), calcium sulfate (CaSO ₄ ), manganese sulfate (MnSO ₄ ), iron sulfate (FeSO ₄ ), copper sulfate (CuSO ₄ ), zinc sulfate (ZnSO ₄ ) At least one salt selected from the group consisting of sodium sulfate (Na ₂ SO ₄ ) and potassium sulfate (K ₂ SO ₄ ) is added in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the solvent. Method for producing oil-resistant coated paper. The method of claim 1 Preservatives include benzoic acid, sodium benzoate, ethyl p-oxybenzoate, propyl p-oxybenzoate, and paraoxybenzoic acid isopropyl p-oxybenzoate. ), Butyl p-oxybenzoate, i-butyl p-oxybenzoate, calcium propionate, sodium propionate, dehydroacetic acid, dehydrate At least one preservative selected from the group consisting of sodium dehydroacetate, sorbic acid and potassium sorbinate is added in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the solvent. Method for producing oil-resistant coated paper. The method of claim 1, Stirring is carried out at 50 ℃ or more Method for producing oil-resistant coated paper. The method of claim 1, The basis weight of the paper is characterized in that 20 to 40g / ㎡ Method for producing oil-resistant coated paper. The method of claim 1, The thickness of the coated soy protein is characterized in that 1 to 10kg / ream (278m ² ) Method for producing oil-resistant coated paper. Soy protein / paper coated paper prepared by the method of claim 1.