Abstract This paper introduces a multi-functional adhesive production process that is suitable for the sealing of beer bottle sealing labels and for the bonding of trademark labels. This product is prepared by using dispersant and chelating agent as the main ingredient of casein and corn starch. It has a large initial viscosity and good stability, and can be used as a substitute for imported products. It has been used for half a year on a 300 kt·a-1 beer packaging line. The effect is good. Keywords beer bottle multi-functional adhesive
In recent years, most of the beer manufacturers in China have used aluminum foil or tin foil as the sealing label for beer bottles in order to strengthen the competitiveness of the products of the factory in the market and improve the product quality. In order to meet the production needs, some breweries will reform the domestic trademark labeling machines, while others will introduce foreign models. Because metal paper and wood pulp paper have different penetration forces on water in adhesives, there is a significant gap between the drying speeds of the two. From the perspective of convenience of production, seal labeling and trademark labeling should be completed in one machine. The higher performance requirements for adhesives are: versatility, fast drying speed, high viscosity, good stability, and ability to replace imported products (prices up to 30,000 yuan per t-1). After a large number of experiments, the author successfully developed the LW type multi-functional label adhesive and realized industrial production. The product has been applied in a large-scale breweries, and its performance has reached the requirements for medium and high-speed labeling machines that are imported or domestically modified.   
1 Test section
1.1 Raw Materials and Specifications
Casein, industrial grade, Gansu; corn starch, industrial grade, Hebei Starch starch factory; dispersant, compounded by industrial grade urea and ammonium bicarbonate; pH regulator, industrial grade soda ash and borax Into; defoamer: tributyl phosphate or silicone oil, chemical purity; chelating agent, made from industrial grade zinc sulfate and zinc oxide; preservatives: sodium diacetate, homemade. 
1.2 Process Flow 1.3 Product Specifications [1]
Appearance light yellow or dark yellow viscous fluid
Solid content/% 40 to 50 (depends on different models)
Viscosity (25 °C)/Pa·s 60 to 90 (Depending on the model)
pH 7.5 to 8.5
Storage period (25 °C)/d ≥180
1.4 Performance Test
The solid content was measured according to GB/T 2793-1995; the viscosity was measured with a KQJ-1 rotary viscometer; the pH was measured with a PHS-29A acidity meter; and the rheology was determined with reference to [2].
2 Results and discussion 2.1 Choice of mass ratio of casein to dispersant Casein is the main film-forming substance of LW adhesives, and it is also a key factor affecting the viscosity performance of the product. According to the literature [1] reported and explored and tested, at room temperature, the aqueous solution of casein with a mass fraction of more than 18% is jelly-like, and can only be free-flowing when heated to 60°C, and its use is limited. If the preparation of high solid content, viscosity, no gel, good fluidity, suitable for beer bottle labeling machine adhesive at room temperature, must be added dispersant. The effect of the mass ratio of casein to dispersant on product performance is shown in Table 1.   
Table 1 Effect of mass ratio of casein to dispersant on product properties Casein/dispersant mass ratio 0.6 0.8 1.0 1.2
Viscosity (25 °C)/Pa·s 56 73 81 87
Liquidity/m·min-1 2.1 1.6 1.1 0.7
Applicability medium speed type high speed type high speed type high speed type
Appearance / stability thin / good thick / good thick / good thick / poor
Note: The mass ratio of water to dispersant is 3:1; pH=7. 
From Table 1, it can be seen that the greater the mass ratio of casein to the dispersant, the greater the viscosity, the slower the flow rate, and the higher product cost. At present, most breweries use medium and high-speed labeling machines for labeling, the viscosity is controlled at 70-85 Pa·s, and the fluidity is controlled between 1.0 and 2.0 m·min-1. According to this requirement, casein and dispersion are required. The agent mass ratio should be chosen in the range of 0.8 to 1.0.
2.2 Control of pH According to the physicochemical properties of casein, the solubility of casein at the isoelectric point of 4.6 is the lowest, but at the condition that the pH is relatively far from the isoelectric point, that is, the acid, alkali or some salt Colloidal dispersions can form in aqueous solutions. For the beer packaging line and the sealed label aluminum foil, the strong acid adhesive has corrosive effect on the labeling equipment, while the strong alkaline adhesive corrodes the label. This test compares the effect of different pH values ​​on product performance. The results are shown in Table 2.
As can be seen from Table 2, when the pH value is less than 9, the viscosity increases with the increase of the pH value, and when it reaches 10, the viscosity decreases, the flow rate increases substantially, the glue liquid is relatively thin, and the sizing is difficult, so the pH value must be controlled at 7.5. Within the range of ～8.5.
Table 2 Effect of pH on Product Performance pH 7 8 9 10
Viscosity (25 °C)/Pa·s 71 76 88 52
Liquidity/m·min-1 1.6 1.4 0.7 1.8
Applicability High Speed ​​Models High Speed ​​Models High Speed ​​Models Not Easy to Apply
Appearance / stability is thicker / better thicker / thicker / better / thinner / worse
2.3 The role and dosage of corn starch
The addition of corn starch can reduce the stringiness of the adhesive and improve the performance of the adhesive on the labeling machine. It can also reduce the amount of added casein and reduce the cost of the product. In experiments, it was found that the addition of a small amount of unmodified corn starch is prone to gelation, and the use of cornstarch in a dual-denaturation treatment can greatly increase the amount of added corn starch. The effect of modified starch addition on adhesive performance is shown in Table 3. 
Table 3 Effect of modified starch to casein mass ratio on product performance Modified starch/casein mass ratio 0.2 0.4 0.6 0.8
Viscosity (25 °C)/Pa·s 56 71 82 94
Liquidity/m·min-1 2.3 1.5 1.2 0.7
Applicability medium speed model High speed model High speed model is not easy to sizing
Appearance / stability is thinner / better thick / thick / thick / poor
Note: The mass ratio of casein to dispersant is 1.0, pH=8. 
From Table 3, it can be seen that the amount of modified corn starch is the main factor affecting the flowability. With the increase of the amount of modified starch, the viscosity increases and the flowability decreases. When the amount of modified corn starch exceeds 0.6 times the amount of casein, the adhesive is too thick. Prone to gel. 
2.4 The role of chelating agents
Aluminum foil as a beer bottle sealing label, not only in normal temperature and normal conditions do not drop the mark, and when the beer bottle frozen in ice water for several dozen hours, the label can not fall off, at the same time requiring the label in the hot water solution is easy to wash off. To this end, heavy metal oxides or salts may be added to react with casein to form a highly water-resistant chelate to increase the water resistance of the glue. Considering comprehensively, this experiment uses a mixture of zinc sulphate and zinc oxide as a chelating agent [3, 4], and examines the effect of its addition on product performance. The results are shown in Table 4. 
From Table 4, it can be seen that the amount of chelating agent has little effect on the viscosity and flowability of the product. It was also found in the experiment that the higher the chelating degree of the adhesive, the faster the drying speed, but the shorter the storage period, so the amount of chelating agent should not exceed 5% of the amount of casein.   
Table 4 Effect of mass ratio of chelating agent to casein on product performance chelating agent and casein mass ratio 0.01 0.03 0.05 0.07
Viscosity (25 °C)/Pa·s 66 71 75 82
Liquidity/m·min-1 1.7 1.5 1.2 0.9
Applicability medium speed type high speed type high speed type high speed type
Appearance / stability is more dilute / better thicker / better thicker / better thick / better
Note: The mass ratio of casein to dispersant is 1.0; pH = 8; mass ratio of modified starch to casein is 0.4.   
3 Conclusions
(1) Through the orthogonal test and range analysis, the optimized preparation conditions of the selected LW adhesive are: casein/dispersant mass ratio of 1.0; modified starch/casein mass ratio of not more than 0.6; cesium chelating agent/antimony The casein mass ratio is less than 0.05; the pH is 7.5-8.5. 
(2) The glue has good fluidity, high initial viscosity and strong adhesive force. It can be applied to beer bottle sealing metal labels and trademark labels, and can also be used for wood, furniture, carton molding and office adhesives. 
(3) The rubber has achieved industrial production of 300 t·a-1 in Hebei Province. The product has been applied to a large-scale brewery of 300 kt·a-1 and its performance has reached the level of imported Henkel glue. The price is cheap and the drying speed is fast. A variety of labels on one machine can replace imported similar products. 
In recent years, most of the beer manufacturers in China have used aluminum foil or tin foil as the sealing label for beer bottles in order to strengthen the competitiveness of the products of the factory in the market and improve the product quality. In order to meet the production needs, some breweries will reform the domestic trademark labeling machines, while others will introduce foreign models. Because metal paper and wood pulp paper have different penetration forces on water in adhesives, there is a significant gap between the drying speeds of the two. From the perspective of convenience of production, seal labeling and trademark labeling should be completed in one machine. The higher performance requirements for adhesives are: versatility, fast drying speed, high viscosity, good stability, and ability to replace imported products (prices up to 30,000 yuan per t-1). After a large number of experiments, the author successfully developed the LW type multi-functional label adhesive and realized industrial production. The product has been applied in a large-scale breweries, and its performance has reached the requirements for medium and high-speed labeling machines that are imported or domestically modified.   
1 Test section
1.1 Raw Materials and Specifications
Casein, industrial grade, Gansu; corn starch, industrial grade, Hebei Starch starch factory; dispersant, compounded by industrial grade urea and ammonium bicarbonate; pH regulator, industrial grade soda ash and borax Into; defoamer: tributyl phosphate or silicone oil, chemical purity; chelating agent, made from industrial grade zinc sulfate and zinc oxide; preservatives: sodium diacetate, homemade. 
1.2 Process Flow 1.3 Product Specifications [1]
Appearance light yellow or dark yellow viscous fluid
Solid content/% 40 to 50 (depends on different models)
Viscosity (25 °C)/Pa·s 60 to 90 (Depending on the model)
pH 7.5 to 8.5
Storage period (25 °C)/d ≥180
1.4 Performance Test
The solid content was measured according to GB/T 2793-1995; the viscosity was measured with a KQJ-1 rotary viscometer; the pH was measured with a PHS-29A acidity meter; and the rheology was determined with reference to [2].
2 Results and discussion 2.1 Choice of mass ratio of casein to dispersant Casein is the main film-forming substance of LW adhesives, and it is also a key factor affecting the viscosity performance of the product. According to the literature [1] reported and explored and tested, at room temperature, the aqueous solution of casein with a mass fraction of more than 18% is jelly-like, and can only be free-flowing when heated to 60°C, and its use is limited. If the preparation of high solid content, viscosity, no gel, good fluidity, suitable for beer bottle labeling machine adhesive at room temperature, must be added dispersant. The effect of the mass ratio of casein to dispersant on product performance is shown in Table 1.   
Table 1 Effect of mass ratio of casein to dispersant on product properties Casein/dispersant mass ratio 0.6 0.8 1.0 1.2
Viscosity (25 °C)/Pa·s 56 73 81 87
Liquidity/m·min-1 2.1 1.6 1.1 0.7
Applicability medium speed type high speed type high speed type high speed type
Appearance / stability thin / good thick / good thick / good thick / poor
Note: The mass ratio of water to dispersant is 3:1; pH=7. 
From Table 1, it can be seen that the greater the mass ratio of casein to the dispersant, the greater the viscosity, the slower the flow rate, and the higher product cost. At present, most breweries use medium and high-speed labeling machines for labeling, the viscosity is controlled at 70-85 Pa·s, and the fluidity is controlled between 1.0 and 2.0 m·min-1. According to this requirement, casein and dispersion are required. The agent mass ratio should be chosen in the range of 0.8 to 1.0.
2.2 Control of pH According to the physicochemical properties of casein, the solubility of casein at the isoelectric point of 4.6 is the lowest, but at the condition that the pH is relatively far from the isoelectric point, that is, the acid, alkali or some salt Colloidal dispersions can form in aqueous solutions. For the beer packaging line and the sealed label aluminum foil, the strong acid adhesive has corrosive effect on the labeling equipment, while the strong alkaline adhesive corrodes the label. This test compares the effect of different pH values ​​on product performance. The results are shown in Table 2.
As can be seen from Table 2, when the pH value is less than 9, the viscosity increases with the increase of the pH value, and when it reaches 10, the viscosity decreases, the flow rate increases substantially, the glue liquid is relatively thin, and the sizing is difficult, so the pH value must be controlled at 7.5. Within the range of ～8.5.
Table 2 Effect of pH on Product Performance pH 7 8 9 10
Viscosity (25 °C)/Pa·s 71 76 88 52
Liquidity/m·min-1 1.6 1.4 0.7 1.8
Applicability High Speed ​​Models High Speed ​​Models High Speed ​​Models Not Easy to Apply
Appearance / stability is thicker / better thicker / thicker / better / thinner / worse
2.3 The role and dosage of corn starch
The addition of corn starch can reduce the stringiness of the adhesive and improve the performance of the adhesive on the labeling machine. It can also reduce the amount of added casein and reduce the cost of the product. In experiments, it was found that the addition of a small amount of unmodified corn starch is prone to gelation, and the use of cornstarch in a dual-denaturation treatment can greatly increase the amount of added corn starch. The effect of modified starch addition on adhesive performance is shown in Table 3. 
Table 3 Effect of modified starch to casein mass ratio on product performance Modified starch/casein mass ratio 0.2 0.4 0.6 0.8
Viscosity (25 °C)/Pa·s 56 71 82 94
Liquidity/m·min-1 2.3 1.5 1.2 0.7
Applicability medium speed model High speed model High speed model is not easy to sizing
Appearance / stability is thinner / better thick / thick / thick / poor
Note: The mass ratio of casein to dispersant is 1.0, pH=8. 
From Table 3, it can be seen that the amount of modified corn starch is the main factor affecting the flowability. With the increase of the amount of modified starch, the viscosity increases and the flowability decreases. When the amount of modified corn starch exceeds 0.6 times the amount of casein, the adhesive is too thick. Prone to gel. 
2.4 The role of chelating agents
Aluminum foil as a beer bottle sealing label, not only in normal temperature and normal conditions do not drop the mark, and when the beer bottle frozen in ice water for several dozen hours, the label can not fall off, at the same time requiring the label in the hot water solution is easy to wash off. To this end, heavy metal oxides or salts may be added to react with casein to form a highly water-resistant chelate to increase the water resistance of the glue. Considering comprehensively, this experiment uses a mixture of zinc sulphate and zinc oxide as a chelating agent [3, 4], and examines the effect of its addition on product performance. The results are shown in Table 4. 
From Table 4, it can be seen that the amount of chelating agent has little effect on the viscosity and flowability of the product. It was also found in the experiment that the higher the chelating degree of the adhesive, the faster the drying speed, but the shorter the storage period, so the amount of chelating agent should not exceed 5% of the amount of casein.   
Table 4 Effect of mass ratio of chelating agent to casein on product performance chelating agent and casein mass ratio 0.01 0.03 0.05 0.07
Viscosity (25 °C)/Pa·s 66 71 75 82
Liquidity/m·min-1 1.7 1.5 1.2 0.9
Applicability medium speed type high speed type high speed type high speed type
Appearance / stability is more dilute / better thicker / better thicker / better thick / better
Note: The mass ratio of casein to dispersant is 1.0; pH = 8; mass ratio of modified starch to casein is 0.4.   
3 Conclusions
(1) Through the orthogonal test and range analysis, the optimized preparation conditions of the selected LW adhesive are: casein/dispersant mass ratio of 1.0; modified starch/casein mass ratio of not more than 0.6; cesium chelating agent/antimony The casein mass ratio is less than 0.05; the pH is 7.5-8.5. 
(2) The glue has good fluidity, high initial viscosity and strong adhesive force. It can be applied to beer bottle sealing metal labels and trademark labels, and can also be used for wood, furniture, carton molding and office adhesives. 
(3) The rubber has achieved industrial production of 300 t·a-1 in Hebei Province. The product has been applied to a large-scale brewery of 300 kt·a-1 and its performance has reached the level of imported Henkel glue. The price is cheap and the drying speed is fast. A variety of labels on one machine can replace imported similar products. 
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