Environmentally friendly low odor low VOC automotive sealant adhesive formula design.

First, the impact of automobile seals on the automotive environment
1. The function of automobile seals Automotive seals mainly play a sealing, daming and decorative role. Physically speaking, car seals can effectively prevent external wind, rain, dust and other harmful substances from entering the car, reduce the vibration generated by doors, windows and other parts of the car, in order to maintain the comfort and cleanliness of the vehicle, and improve the working environment of the sealed parts or devices, and extend the working life. For a long time, automotive seals required connectivity, sealing and decorative 3 functions

. With the progress of science and technology and the development of the automotive industry , especially the emergence of emerging materials , people are increasingly demanding environmental protection , comfort , safety , energy saving and aesthetics of automobiles , and the requirements for the three major functions of automotive seals are constantly being developed and improved .
2. The impact of seals on the automotive environment Automotive seal surface coating, rubber body, after-treatment grease and other substances attached to the surface of the sealing fit, or mixed with dust, rain and accumulation of stains, usually appear black, easy to remove through car cleaning. Rubber with the system of higher activity adders, such as certain vulcanizing promoter, anti-age agent, softener, etc. , after a period of time to migrate to the paint, and with the paint reaction to form a pollution, usually stains appear yellow. This stain is difficult to remove and affects aesthetics. Green car seals used raw materials should not contain ingredients related to environmental pollution, color should be with the car body paint color, car interior and exterior decoration coordination match, and has a good sense of insensitivity to paint, in the process of vehicle use seals will not produce light paint pollution, green seals should not emit unpleasant odor, with excellent environmental resistance, weather resistance, its service life should generally be the same as the vehicle life.
2. Green laws and regulations and their differences
Laws and regulations associated with green environmental protection include RoHS Directive, ELV Directive (End-of-Life Vehicle, End-of-Life Vehicle Directive), REACH Directive, VOC (Volatile organic compounds, volatile organic compounds) detection, i.e. organic volatile detection of interior air and interior materials. REACH and RoHS have the same thing, but there is no conflict and repetition. RoHS is a mandatory regulation in the European Union, i.e. products sold in the EU market and must be tested by RoHS. REACH is a voluntary environmental regulation in the European Union, and in addition to requiring suppliers' products to meet RoHS regulations, high-end customers generally require them to comply with REACH regulations. RoHS regulations are mainly for electrical and electronic products, metal, ceramic material detection of 4 harmful substances, non-metallic detection of 6 harmful substances, REACH regulations of non-metallic detection of 53 substances, and covers almost all categories of products except food, medicine. RoHS is one of the largest environmental regulations technology technology technology technology technology with greater coverage and REACH coverage. VOC testing is a potential hazard to the environment and human health, so VOC is specified in many product manufacturing, especially in indoor and in-car products, as concentrations can be very high indoors and in-car. There are also VOC regulations for coatings and paints. The effects of VOC on human health are chronic rather than acute, including skin and eye irritation, respiratory diseases, headaches, fatigue, cancer, etc. REACH weighs the source of raw materials for manufactured products, RoHS weighs finished products, and VOC weighs the environmental impact of products. The purpose of the EU Green Directive is to strengthen the protection of human health and environmental safety and ensure sustainable development. Second, set up technical barriers to improve the entry threshold of products. Third, to maintain and improve the competitiveness of the EU chemical industry, as well as the research and development of non-toxic harmless compounds innovation ability, to prevent market fragmentation, increase transparency in the use of chemicals, the pursuit of sustainable social development.
third, glue formula design
. 1. Raw rubber selection car with rubber seal main is made of three yuan ethyl propylene rubber (EPDM) foaming and dense composite, including a unique metal fixture and tongue-shaped buckle, durable, easy to install. At present, EPDM raw rubber brand number is very wide, available for products manufacturers to fully choose. There are many factors affecting the physical mechanical properties of EPDM vulcanized gel, and the selection of biogels for the formulation of sealing strip adhesives in green rings can be considered from the general rules of the chemical structure parameters of EPDM on polymer bioglue and vulcanized gum, including EPDM synthetic catalytic technology, ethylene propylene composition ratio, third monomer content, oil charge, molecular structure distribution and other major parameters. In the process of combining EPDM, whether it is the Ziegler Natta catalyst, the moly metal catalyst, or the more advanced Keltan ACE catalyst, the catalyst is used and the residue is very low due to the high catalytic efficiency. The contamination of EPDM by low metal ions or harmful substance residues can be eliminated, so most EPDM pigments exhibit good colorless and transparent characteristics. Green ring car seals require "good elasticity and anti-shrinking shape, ethylene content should not be too high, about 50% to 60% is appropriate." The third monosome must be fast vulcanized ENB type, and the ENB content should be more than 7.5%, which can shorten the vulcanization time and improve production efficiency. The raw glue with narrow molecular weight distribution can provide fast vulcanization rate, sulfurization speed, and obtain deep crosslinking, especially to improve the permanent deformation performance of compression. In the synthesis EPDM process, through multi-stage reactor, catalyst and mixed with or solution to obtain the distribution of twin peaks of raw glue, twin peak distribution of raw glue in addition to excellent physical and mechanical performance, but also good processing performance, good resistance, excellent anti-collapse performance, more and more people's favor. Properly charged EPDM broadens the molecular weight distribution, which is also equivalent to the distribution of Twin Peaks to a certain extent. Experiments have proved that the presumptive material of EPDM raw glue with oil is less than that of ordinary EPDM biogel, because hydrogen fossil wax oil filled with EPDM is not easy to pre-ate during synthesis, and the use of oil-filled EPDM can reduce the migration pollution caused by large amounts of refueling when combined. The main parameters of several EPDM chemical structures can be found in Table 1, which can be used as the basis for the selection of raw glue for the design of green car sealing strip adhesive formula.
2. Vulcanization system selection Usually the sulfur-yellow vulcanization system needs to be added to a larger variety of promoters, the dosage is also larger, so the residue of the promoter and the by-product of the vulcanization reaction is often more. Coupled with the complexity of the vulcanization reaction, the impact of the vulcanization system on the green environmentally friendly sealant adhesive becomes more complex. The design of green ring car sealing strip adhesive formula, in the selection of vulcanization system should take full account of its toxicity, frost spray, odor and the amount of volatile nitrosamine production. General promoters are less toxic substances. Niacin and thiophenics are the most toxic and are now rarely used again. Autumn lamb, aminomates are moderate, followed by subsulsamide and pyrethroids. According to the solubility parameters of the promoter in ethyl propylene rubber, the amount of dosing of various promoters should not exceed the spray limit dosage, and the alkyl replaces the smaller TMTD and PZ easily equip, which should be noted when used. Some promoters, such as DTDM, produce an odor during the vulcanization process, so avoid them when selecting them. Green sealant adhesive requirements limit the production of volatile nitrosamines during the vulcanization process. Midamine promoter reacts with nitrogen oxidation in the air during vulcanization to produce nitrosamine carcinogens. A number of commonly used promoters, such as desulfurized amino acids, Tyurant and desulphate morphine, will be banned. The desulphate promoter is currently a non-nitrosamine promoter and has been widely used in EPDM's eco-friendly vulcanization system, such as ZDTP (zinc deanaminate). The larger the alkyl subsistor volume of a midamine promoter, the greater the spatial resistance effect, the lower the volatility of nitrite, and the less impact on the environment. The promoter TBzTD (TBzTD (tetimulated tetyurine, relative to molecular mass 544) is currently considered to be a midazolam promoter that does not produce nitrosamine hazards and is associated with its large subsorbic group. Environmentally friendly alternatives to nitrosamines are below Table 2.
, compared the nitrosamine-free vulcanization system with the ordinary sulfur-yellow vulcanization system on the vehicle sealing strip adhesive on the body paint pollution. The effects of different vulcanization systems on paint contamination can be found in Table 3.
from table 3 data, it can be seen that nitrosamine-free vulcanization system adhesive measurements show that the value of E is small, the color change is lighter, less pollution. This is because the relative molecular mass of nitrosamine-free promoters is generally larger, or the chemical groups without nitrosamine promoters are less polluting.
3. The particle size, structure and surface chemistry of the choice of charcoal black is the main factor that determines carbon blackness. Rubber sealant material commonly used in carbon black N550, N762 / N774, SP5000, etc. , these carbon blacks have a higher structure, medium and other strength, extrusion process and good toughness, and the appearance of smooth, in the EPDM sealant adhesive formula has always occupied a dominant position. There are usually hydrogenic groups containing hydrogen and oxygen, as well as impurities such as sulfur and tar, on the black surface of carbon. Carbon black in the carbide, aldehyde and other oxidizing groups will pollute the contact or working medium, carbon black in the withdrawal content is high, will migrate to the product surface, causing the surface blue, color and other defects. High impurity content can seriously affect the appearance quality of extruded products, such as small spots or slip marks on the surface. The main parameters of several carbon blacks can be found in the table .
the chromometer to show the color difference between the sample and the sample under test, i.e. the greater the value of E, the more serious the color change. Through analysis, it can be seen that the larger the carbon black iodine absorption value, the smaller the particle size, indicating that the larger the surface area, the more oxidizing groups on the carbon black surface, the higher the value of E, the worse the anti-pollution. Therefore, the design of green sealing strip adhesive should choose the iodine absorption value of smaller carbon black. In recent years, in the EPDM automotive high-end seals, Cabot, Uctronic, Columbien has launched SP6000, HS22, XT1004 carbon black, is a semi-strong, high structure of carbon black (iodine absorption value of 20 x 5 mg /g, DBP oil absorption value of 96 x 6Ml/100g), and impurity content and acetone pumping is quite low. Because in EPDM there is a better dispersion than N550 carbon black, extruded products of good stiffness, smooth appearance, small defects, high elasticity, so in the production of high-end car seals, low-hardness seals and sponge seals have been favored, these kinds of carbon black has also become the design and preparation of green car seal strip adhesive formula of choice.
4. The softener widely used in the selection of EPDM rubber seals is paraffin oil, paraffin oil and EPDM are non-polar, its solubility parameters are very close. Therefore, paraffin oil in EPDM has a good compatible, the amount of cooperation is generally unlimited. Green car seals require filled softeners not only to meet EPDM's requirements for their chemical composition and structural characteristics, but also to minimize the adverse components affecting the stability of softeners to ensure environmental protection. Paraffin oil contains sulfur, nitrogen heterocyclic compounds and polycyclic aromatic hydrocarbons, belong to non-hydrocarbon polar compounds, darker color, mainly concentrated in high viscosity distillate, their presence will seriously affect the color of paraffin oil, photooxidation stability, thermal aging, and EPDM products use performance. Aromatic hydrocarbon content and volatile substances in paraffin oil play a vital role in green environmentally friendly EPDM automotive seals, low aromatics content can improve the antioxidant degradation performance of rubber, low volatility can help prevent rubber aging contraction, and help improve the poor appearance of products (such as rough, bubbles), these two characteristics are conducive to extending the life of EPDM automotive seals. Aromatic composition in paraffin oil, asphalt, and chemical substances in the form of extreme compounds such as thiol, carboxyl, and vane can react with body paint to cause paint color change. The main data parameters of several paraffin oils and their comparative tests on body paint contamination are in Table 5.
production of paraffin oil T13 by a domestic company, aromatic content is larger, the measurement of wet E value is relatively high, the stain is relatively large. Paraffin oil T13 and P2280 for the German Hansan Division products, unsaturated hydrocarbons (aromatic hydrocarbons) content is small, paraffin hydrocarbon content is larger, measurements show that the value of E is relatively low, relatively small pollution. PW 380 is white oil, that is, white mineral oil, colorless tasteless, chemical inert, good light stability performance, the basic composition of saturated hydrocarbons (cyclane and paraffin-based) structure, aromatic hydrocarbons, nitrogen, oxygen, sulfur and other substances near zero, safe and environmental protection, products in the light will not change color, is non-polluting high viscosity colorless transparent hydrogen fossil wax oil. As can be seen from Table 5 data, PW380 white oil is the least polluting. Therefore, when choosing softener for green car seal adhesive, white oil without aromatics or paraffin oil with very low aromatic content should be used, and at the same time it has the characteristics of high viscosity, high flash point, light color, high content of saturated hydrocarbons, low volatility and so on.
5. There are a number of foaming agents suitable for EPDM sponge products, including inorganic chemical foaming agents and organic chemical foaming agents, as well as compound foaming agents. Design EPDM automotive sponge sealing strip adhesive, from foaming temperature and vulcanization temperature and other aspects of comprehensive consideration, most of the use of thermal decomposition type of organic chemical foaming agent. The decomposition temperature of selecting foaming agent should be within the temperature range of vulcanization can be regulated, the decomposition temperature of foaming agent is greatly affected by the compound agent in the adhesive, which is more difficult to adjust than the vulcanization speed.