6. The effect of vacuum
When the crude monomer is produced by the cracking reaction and refined, it is required to be carried out under vacuum, and the degree of vacuum has a great influence on the yield and product quality. At the time of cracking, the degree of vacuum must not be less than 8999.5 Pa. Especially when the crude monomer is refined, the vacuum degree must reach 1×10 5 Pa or more, otherwise the fine monomer exceeds its own temperature (70-80° C.) before it vaporizes and evaporates, so that the monomer is easily polymerized and thickened and lost. Adhesion (Table 3).
Second, the process
The rapid synthesis method is simpler than the traditional process and is divided into three processes:
The first was an addition condensation reaction with formaldehyde in the presence of an alkaline catalyst of cyanoacetate, and immediately after completion of the reaction, dehydration was carried out with dichloroethane. Secondly, some of the solvent is recovered in the presence of a cracking medium and under negative pressure, followed by cracking to make the crude monomer. Third, the fine monomer is prepared from the crude monomer in a stream of SO2 and under a negative pressure. It takes only 5 to 6 hours from the feed to the finished product, and the yield is as high as about 65% to 70%, which improves equipment utilization.
Third, application
Pure alpha-cyanoacrylate is a colorless, transparent liquid. To make it into 502 glue, it is necessary to add the following formula: Ethyl α-cyanoacrylate 94%, methyl methacrylate-methyl acrylate copolymer 3%, tricresyl phosphate 3%, trace hydroquinone, Sulfur dioxide traces.
The cure speed of 502 glue is related to the air humidity. The higher the humidity, the faster the curing. If the reaction is too fast, the molecular weight of the polymer is low, the strength of the rubber joint is poor, and the most suitable air relative humidity is about 70%. The 502 glue is exposed. The length of time in the air is very much related to the bonding strength. When the exposure exceeds 2 minutes, the performance drops by more than 50%, and the bonding strength is highest within one second.
The dining table and chair combination in a restaurant refers to the combination of tables and chairs used for dining. According to different needs and styles, restaurant dining table and chair combinations can be classified into various categories. The following will classify and introduce common dining table and chair combinations in restaurants.
1. Classified by purpose
1) Dinner table and chair combination: mainly used in formal dining venues, such as high-end restaurants, banquet halls, etc. The combination of dining tables and chairs usually uses high-end materials such as solid wood, marble, etc. The chairs are generally equipped with soft cushions to provide a comfortable dining experience.
2) Fast food table and chair combination: mainly used in fast food restaurants, coffee shops, and other fast-food restaurants. The combination of fast food tables and chairs usually adopts a simple and practical design. The tables are generally small, and the chairs are generally made of plastic or metal materials, which are easy to clean and move.
3) Outdoor table and chair combination: mainly used in outdoor dining venues, such as outdoor restaurants, balconies, etc. Outdoor table and chair combinations usually use materials with special treatments such as waterproof and anti-corrosion, such as aluminum alloy, plastic, etc., which have the characteristics of durability and easy cleaning.
2. Classify by Style
1) Modern style table and chair combinations: Modern style table and chair combinations usually adopt a simple and streamlined design, emphasizing practicality and comfort. The combination of modern style tables and chairs is suitable for modern restaurants, cafes, and other places.
2) European style table and chair combinations: European style table and chair combinations usually adopt gorgeous carved and curved designs, emphasizing details and decoration. The European style table and chair combination is suitable for high-end restaurants, banquet halls, and other places.
In summary, restaurant table and chair combinations are classified based on factors such as purpose and style. Different classifications are suitable for different types and needs of restaurants, and choosing the appropriate combination of dining tables and chairs can provide a better dining experience and comfort for the restaurant.