Development of the hottest casein high speed label

Development of casein high-speed labeling adhesive

Abstract: a high-speed labeling adhesive suitable for beer production lines with more than 36000 bottles/hour was made from casein, polyacrylamide, urea and starch. The effects of various factors on the properties of adhesive were studied. The results showed that the viscosity, drying speed and cold storage stability of the adhesive increased with the increase of casein content; The storage stability increased with the increase of pH value; When the dosage of polyacrylamide increases, the viscosity also increases greatly

key words: casein; Labeling adhesive; Performance

preface

at present, in China's beer production industry, in addition to the adhesives made of starch and modified starch for labeling beer bottles, there are also polyvinyl formal, modified polyvinyl formal and other types of labeling adhesives. Each of them has its own characteristics, which has played a positive role in the development of China's beer manufacturing industry. However, these adhesives are only suitable for labeling beer production lines with a speed of about 20000 bottles/hour. Due to the rapid development of the beer manufacturing industry, the output has been greatly increased, and the production speed has been accelerated. At this stage, the speed has risen to 30000-40000 bottles/hour. The requirements for labeling adhesives are getting higher and higher, resulting in some manufacturers relying more on imported labeling adhesives. This not only increases the production cost, but also restricts the development of China's beer industry to some extent. In order to meet the actual needs of production, the author uses casein as the main raw material, dissolves polyacrylamide water-soluble polymer material, and starch as filler to make a high-speed labeling adhesive for beer production lines with a speed of more than 36000 bottles/hour, which is different from the situation of "many, small and scattered" in China's medical device enterprises

1 experimental part

1.1 name, specification and proportion of main raw materials

Table 1 name, specification and proportion of main raw materials

name, specification and proportion/w% casein grade I 16 urea industry 4 polyacrylamide industry 1. Add appropriate cooling medium to the cooling tank of low temperature tank 8 corn starch industry 20 borax industry 2 ammonia industry appropriate amount of water tap water 501.2 preparation method

add a certain amount of casein Water and borax are placed in the reaction kettle, heated and stirred to dissolve casein into a uniform solution. Add urea and polyacrylamide into the solution to continue to dissolve. After stirring for about half an hour, add starch to stir, and heat at 80 ℃ to gelatinize into a uniform viscous solution. Cool down, add ammonia to adjust the pH value to about 8, and then discharge

1.3 performance test

nonvolatile content: determined according to GB/t2793 － 1995. Viscosity: mdj-1 rotary viscometer, determined according to GB ／ 2794. PH value: measured by phs-3 pH meter. Cold storage stability: put a certain amount of adhesive in the cold storage room of the refrigerator (0-5 ℃), take it out after 72h, place it at room temperature for about 4h, and then measure the viscosity at 25 ℃, and the viscosity remains unchanged. Drying speed: use adhesives with different proportions to measure the drying speed of the labeling machine. Storage stability: observe the casein adhesive at room temperature to see the time of delamination and gel

2 results and analysis

2.1 performance index of labeling adhesive

the performance index of the adhesive produced by the adhesive ratio determined by repeated experiments and production practice is shown in Table 2

Table 2 adhesive performance index

name index appearance yellowish transparent viscous liquid, with fluidity nonvolatile content/% 48 ± 2 pH value 8.2 viscosity (25 ℃)/mpa · C 30000-50000 drying speed/s cold storage stability stability ≥ 6 months 2.2 factors affecting adhesive viscosity

2.2.1 influence of casein dosage on viscosity

casein dosage has a great influence on adhesive viscosity. Figure 1 (omitted) shows the relationship between casein dosage and viscosity. It can be seen from Figure 1 (Figure omitted) that with the increase of casein dosage, the viscosity increases, because casein is a phosphorus containing protein from a safe, convenient and fast liquid of animal milk, with a large relative molecular weight (about 75000-375000), and protein molecules contain amino (-nh2) and carboxyl (-cooh). At dry weight, the protein appears as curly powder particles. Under acid or alkaline conditions, -nh2 combined with h+ is converted to -nh2+, or -cooh is converted to -coo na+ by alkali neutralization, which is soluble in water. At this time, the volume of the curled protein expands rapidly and forms micelles. The hydrophilic end points to the aqueous phase, and the lipophilic end points to micelles, which are suspended in water. With the increase of casein dosage, micelles increase and viscosity increases. The amount of casein should not be too large. Different labeling machines have different requirements for the viscosity of adhesives. Generally speaking, it is appropriate to control the dosage of casein at 14% - 25%. If the dosage is too large, at room temperature, the viscosity of casein adhesive is very large, and the fluidity is poor, which affects the coating

2.2.2 effect of polyacrylamide on viscosity

polyacrylamide is a linear structure with good water solubility. When it is dissolved in water, it is in the form of thread mass structure in water. The amide group reacts strongly with water to form a huge dynamic volume, which increases the viscosity, as shown in Figure 2 (omitted). With the increase of the amount of polyacrylamide, the viscosity increases more and more significantly. However, the dosage of polyacrylamide should not be too large. In addition, the relative molecular weight of polyacrylamide should not be large. If the relative molecular weight is large, the dispersion performance of Polyacrylamide in casein glue solution is poor, and it is easy to hold the rod in the mixing process, affecting production

2.3 effect of casein on drying speed

drying speed is a very important index of beer label adhesive. In the high-speed beer production line, if the drying speed is small, the label cannot be attached to the beer bottle, which makes the phenomenon of label dropping and label flying very serious. The relationship between casein dosage and drying speed is shown in Figure 3 (Figure omitted)

it can be seen from Figure 3 (omitted) that the amount of casein is small and the drying speed is slow. The amount of casein is 4%, and the drying time is about 13 S. when the amount is 8%, the drying time is 12 s. With the increase of casein dosage, the drying time becomes shorter. When the casein dosage is 16%, the drying time is about 9s, which is more in line with the labeling requirements of beer production speed of 36000 bottles/hour

2.4 effect of casein on the cold storage stability of adhesive

people are used to drinking frozen beer. Therefore, whether the beer label adhesive can withstand low temperature is also a very important indicator to measure the performance of the adhesive. If the low-temperature stability of the labeling adhesive is not good, the label pasted on the beer bottle will wrinkle and fall off under low-temperature conditions. It is found that casein plays an important role in the cold storage stability of adhesive. First of all, casein is insoluble in cold water, so the casein film will not be damaged by cold water at low temperature; Secondly, casein has better initial adhesion strength; At the same time, the addition of polyacrylamide can improve the viscosity of casein and make casein adhesive have better cold storage stability

2.5 effect of pH value on storage stability

add ammonia in the final stage of casein adhesive preparation, adjust the pH value to about 8, make the adhesive alkaline, and increase the stability of the adhesive. The effect of pH value on stability is shown in Figure 4. The stability increases with the increase of pH value; However, if the pH value is less than 4, it is stable to avoid the slippage or fracture of the sample before the experiment, and the fixity in the fixture also increases. This is because the isoelectric point of casein is 4.6, greater or less than 4.6 is conducive to the dissolution of casein in the water system

3 conclusion

through experiments and practical tests, it is proved that casein is high