Effects of adhesive
1. The type of adhesive
Adhesives for dry compounding are divided into single-component hot-melt adhesives and two-component two-liquid reactive adhesives.
The probability of bubbles generated by the single-component hot-melt adhesive is much higher than that of the two-component two-liquid reactive adhesive, and the bubbles in the finished product caused by it will not be eliminated. This is due to the fact that the single-component hot-melt adhesive is applied to the drying roller after being coated by the upper roller to be dried, and the finished product is not cured after being wound, and the molecular diffusion in the adhesive is relatively weakened. Of course, if the two-component two-liquid reactive adhesive is not selected properly, it will also cause bubbles. When choosing a two-component two-liquid reactive adhesive, one should choose an adhesive produced by a regular manufacturer with a slightly larger molecular weight, a uniform molecular weight distribution, excellent solvent release performance, and good leveling to effectively reduce the probability of bubbles.
Generally speaking, the leveling property of general-purpose adhesives is better than that of cooking adhesives, but for composite products with cooking requirements, special cooking-resistant adhesives must be selected.
2. Preparation and use of adhesive
Before formal compounding, the adhesive should be prepared strictly in accordance with the instructions for use. The correct operation method is: first add the main agent, then add ethyl acetate and stir well, then add the curing agent, and add while stirring. The prepared adhesive should be clear and transparent. The solid content of PU-1975 type adhesive used by our company is 75%, and the compounding ratio is: main agent: ethyl acetate: curing agent = 1: 2.5: 0.2. In actual production, the solid content of the adhesive should be compatible with the coated anilox roller.
Our company has very strict management of adhesives. We use vacuum pump to draw air first, and then pour it into the adhesive tray for coating. When pouring the adhesive into the rubber tray, the action should be gentle to prevent the impact force from being too large, mixing air into the adhesive and causing bubbles. To this end, our company has developed a self-adhesive device. The specific method is: after processing an iron drum (containing adhesive), a plastic flow tube is connected, and a switch is provided on the flow tube. Used to control the flow of adhesive. When the adhesive is added through the device, the impact force is reduced, so that the air cannot enter the glue solution, thereby reducing the probability of bubbles.
3. Use of thinner
When using two-component two-liquid reactive adhesive, in order to ensure uniform coating and facilitate wetting, it is necessary to add a thinner to the adhesive to dilute it. Diluents include toluene, ethyl acetate, methyl ethyl ketone, etc. Toluene is gradually being eliminated because it is not conducive to environmental protection and it is easy to cause bubbles. Methyl ethyl ketone is relatively expensive because of its high price, and its affinity with adhesives is not very good, so it is used less. The most commonly used thinner is ethyl acetate.
The thinner must not contain water, alcohol, amine, etc. If the water content exceeds 0.2%, since the volatilization rate of water is much lower than that of ethyl acetate, the volatilization rate of the solvent will be greatly reduced, which will affect the spreading and hardening of the adhesive. After the BOPP film and the CPP film are compounded, the composite product will generate large bubbles and diffuse out irregularly. After curing, the peel strength of the large bubbles is extremely poor, as if there is no gluing. Therefore, the purity of the diluent should be above 98%.
Effects of residual solvents
The composite film base material is coated with glue and then dried in a drying tunnel. The cleaner the solvent is, the better. Otherwise, the residual solvent will not only produce odor, but also form fine bubbles on the cooled composite film.
The drying tunnel of the dry compound machine is divided into 3 areas, namely: evaporation area, hardening area and odor elimination area. In actual production, the temperature of these three sections should be adjusted according to the actual composite substrate. Generally speaking, the temperature of the three stages is controlled to 50-60 ℃, 70-80 ℃, 80-100 ℃, and the temperature increases in a gradient. It is strictly forbidden to enter the drying tunnel with a high initial temperature, while the temperature in the odor elimination area is low. This is because the excessively high initial drying temperature is not conducive to the evaporation of the solvent from the inside to the outside and cannot be completely and completely dried. "Like", leading to the generation of bubbles.
Effect of curing time
If the product after compounding is not mature enough, tiny bubbles are also easily generated. With the extension of the aging time, the bubbles in the product gradually decreased. When using PU-1975 type adhesive, the curing time is generally 24 to 48 hours, and some products require a longer curing time.
Influence of anilox roller
The role of the anilox roller is to apply the adhesive uniformly to the surface of the composite substrate. The amount of coating is determined by the depth of the anilox roller and the working concentration of the adhesive. Under normal circumstances, the anilox roller can only apply 1/6 to 1/4 of the adhesive on the substrate under the pressure of the rubber roller, so the anilox roller must be kept clean and free of clogging, otherwise glue will occur. Adhesive transfer is poor, uneven coating, and eventually the composite material generates bubbles.
It is best to clean the anilox roller regularly, and use a special film cleaner. When the machine is not working, the anilox roller should also be cleaned and the rubber roller should be separated from the anilox roller.
Environmental impact
The temperature and humidity of the environment also have a great influence on the quality of the composite product.
When the ambient temperature is too high, the two-component adhesive is turbid and the coating performance is poor, resulting in the generation of air bubbles. Therefore, the adhesive should be used as needed, and how much is used. If the ambient temperature is too low, the leveling of the adhesive will deteriorate, and bubbles will also be generated. Especially in winter, it is often found that the adhesive becomes thicker and the leveling becomes worse. In response to this phenomenon, our company first matures the main agent for 1 to 2 hours, and then mixes it. The leveling is much better, but it needs to be guarded. The ambient temperature is generally controlled at 23 ～ 25 ℃.
If the ambient humidity is too high (more than 70%), condensation will occur at the anilox roller and rubber roller. The reaction of moisture with the curing agent will generate carbon dioxide, which will eventually cause bubbles. It is better to control the relative humidity between 50% and 60%.
Influence of mechanical factors
The bubbles generated by the composite membrane are sometimes very regular, for example, bubbles repeatedly appear at the same position. Regular air bubbles are often caused by mechanical reasons, such as unevenness of the surface of the rubber roller or the heat press roller, or the temperature of the heat press roller is low, the pressure is not enough, or the angle of the composite film is too large. Among them, the temperature of the heat press roller is too low is not conducive to the further activation of the adhesive, resulting in the generation of bubbles. The temperature of the heat press roller should be adjusted within the range of 60 ~ 80 ℃ according to the actual situation. The pressure is generally adjusted within the range of 0.15 to 0.4 MPa. The angle of the composite membrane is too large, it is easy to bring air into the membrane layer and generate bubbles. The included angle is generally 35 ℃.
There are still many reasons for the generation of dry composite bubbles, and everyone needs to sum up and communicate with each other in their usual work.
Dining chair is a common seat in restaurants, bars, cafes and other places for people to use when dining. According to different design styles, materials, functions and uses, dining chairs can be divided into a variety of categories. The following will be a brief introduction to the product classification of dining chairs.
First, according to the design style classification
1. Simple modern style: Simple modern style dining chairs usually use simple lines and Outlines, focusing on functionality and practicality, suitable for modern restaurants and cafes.
2. European classical style: European classical style dining chairs pay attention to gorgeous details and decoration, common hollow carving design and curve shape, suitable for high-end restaurants and banquet places.
3. Nordic style: Nordic style dining chairs focus on simple, natural and comfortable design, usually using wood materials and simple lines, suitable for family restaurants and cafes.
4. Industrial style: Industrial style dining chairs often use metal materials, with simple, solid and practical characteristics, simple and unadorned, suitable for cafes and bars and other places.
Second, according to the material classification
1. Wooden dining chair: Wooden dining chair is usually made of solid wood or artificial wood, with natural, environmental protection and warm characteristics, suitable for families and cafes and other places.
2. Metal dining chair: Metal dining chair is often made of metal materials such as iron, aluminum or stainless steel, with strong, durable and easy to clean characteristics, suitable for bars and cafes and other places.
3. Plastic dining chair: Plastic dining chair is usually made of polypropylene or polycarbonate and other plastic materials, with light, waterproof and easy to clean characteristics, suitable for fast food restaurants and school cafeterias and other places.
Third, according to the use of classification
Generally, it can be divided into two uses: domestic and commercial.
1. Home dining chair: Home dining chair pays attention to comfort and beauty, common dining table chair, folding chair and bar chair.
2. Commercial dining chairs: Commercial dining chairs pay attention to durability and practicality, common bar chairs, cafe chairs and fast food restaurant chairs.
In general: dining chair as one of the important furniture in restaurants, bars, cafes and other places, according to the design style, material and use of different, can be divided into a variety of categories. Choosing a dining chair that suits your place and needs can enhance the comfort and beauty of the dining environment.
Cafe chair,wholesale chair,stackable chair,connected chair
Foshan Shengshi Zhihui Technology Co., Ltd. , https://www.szhfurniture.com