First, the most important thing to calculate in the hard foam combination is the ratio of black and white materials (weight ratio) is reasonable, another formal statement seems to be called “isocyanic acid index” is reasonable, translated into the vernacular is “the proportion of white and black materials mixed by weight to completely react to the end The translation is “the white material and the black material must be completely reacted by weight”. Therefore, everything in the white material that is involved in the reaction with -NCO should be taken into account. Theoretical molar amount of -NCO consumed by each component is calculated as follows.
(i) the main material: polyether, polyester, silicone oil (ordinary hard foam silicone oil have hydroxyl value, because the addition of diethylene glycol and other dilution, some foam stabilizer type silicone oil also contains amino) the number of formulations multiplied by the respective hydroxyl value, and then add up the number Q, S1 = Q ÷ 56100 (ii) water: the amount of water formulation W S2 = W ÷ 9
(iii) involved in the consumption of – NCO small molecules: the formulation amount of K, its molecular weight is M, the functional degree of N S3 = K × N / M (with more than two small molecules need to be calculated separately and then add up) S = S1 S2 S3
The amount of crude MDI required for the basic formula [(S × 42) ÷ 0.30 ] × 1.05 (so-called isocyanic acid index 1.05)
In fact, the above calculation is only a basic consumption, due to the complex reaction process of black and white material, the actual -NCO consumption must be more than this number, such as the case of triple catalyst, how much additional consumption of -NCO, no one can say clearly. In addition, there is water in the polyether, high 0.1% is very serious; polyether hydroxyl value is also to see people’s leaflet, I have seen polyether hydroxyl value range spanning 90mgKOH/g, that calculation number out only for reference, can not be serious!
Test design] of “refrigerator, freezer” category
This combination material system important requirements and instructions
1, fluidity should be good, density distribution “as far as possible” uniform. First of all, the viscosity should be considered, only the system viscosity is small, the initial liquidity will be good (the average viscosity of the main part of 6000mPa.S below, the combination of material 350mPa.S below), followed by the system of potassium, sodium miscellaneous ions should be controlled in a low limit (within 20ppm), so that the control to avoid trimer reaction in advance, that is: the system viscosity becomes large prematurely. If the liquidity is not good, foam material marching to the distal end of the injection port will appear draw marks resulting in the olive spherical structure of the bubble hole, this position must not resist low-temperature shrinkage.
2, the bubble hole is fine and dense, the thermal conductivity should be low. It is not difficult to understand the bubble pore is the first premise of low thermal conductivity, at this time, the first consideration is to add 403 or some aromatic amine ether into the system (their role is to first react with -NCO, its products and other components of the mutual solubility, emulsion stability, and to ensure that the initial nucleation of the foaming system is stable, that is, to avoid bursting bubbles, so that the bubble pore fine) followed by the polyether itself alone foaming its bubble pore structure to be good ( For example, 635SA with sorbitol as the starting point is much finer and more uniform than 1050 with sucrose as the starting point, and 835 with glycerol as the starting agent is finer than 1050, even for the so-called 4110 grade polyether, the one with propylene glycol as the starting point is better than diethylene glycol. The polymerization catalysts used for polyether production are different, and the properties of the produced polyethers are also different: the molecular weight distribution of polyethers catalyzed by potassium hydroxide is narrower than that catalyzed by dimethylamine. (In addition: polyether production process control —– temperature control, evacuation, PO – that is, propylene oxide flow control, PO raw material quality, post-treatment, etc. —– will also directly affect the polyether foaming pore structure) Third, you can consider adding some polyester components that can improve the fine density of pores. Fourth, the appropriate addition of low-viscosity material to adjust the overall viscosity (such as 210 polyether)
3, low temperature resistance to shrinkage to be good. This needless to say. One is the degree of functionality, the overall average to 4 or more. Secondly, the foam body molding space crosslinking point distribution is uniform (intuitive interpretation is: the main polyether reaction activity as far as possible, the continuous approximate space structure to be much more stable.)
4, good bonding. The so-called bonding superficially refers to the foam body and refrigerator, freezer shell and liner bonding between, in fact, refers to the foam body flexibility, and resistance to shrinkage, (water dosage, reduce the overall hydroxyl value, add flexible structural components, such as 210, 330N and so on can improve the adhesion of foam to the shell)
5, the cost is lower. At present, the refrigerator, freezer industry competition white-hot, excellent performance and expensive combination of materials no one can afford, so we must consider for the cost (such as aromatic polyester price than the polyether low, you can add some.)
6, safety. This is the special requirements of the cyclopentane system (at least cyclopentane is not like F11 as much as you want to add, it is not difficult to understand the addition of more cyclopentane has more security risks)
7, to ensure the continuous stability of the foam production process refrigerators, freezers, continuous production lines are generally very stable control, but does not exclude the occasional fluctuations in process parameters, such as material temperature, ambient temperature a degree or two higher, the proportion of black and white material in a small range of fluctuations, etc., so the combination of materials required to have a certain “tolerance”
8、Black material matching. Each black material own traits, activity is different, then, the white material system to adjust sometimes seems to be exceptionally necessary. (With 5005’s okay, in no way means that with 44v20 can be arbitrarily switched)
The main polyether polyester selection direction
1, phase solubility. Refers to ” polyether, polyester / silicone oil / water / catalyst / physical foaming agent ” composed of the system should be good mutual solubility, homogeneous and stable —– at least stored for a period of time can not be delaminated.
2, functional degree composition and skeleton type. In principle, the higher the degree of functionality, the physical properties of the foaming body values (dimensional stability, compressive strength, etc.) on the more “ideal”, but often the high degree of functionality of the polyether viscosity on the large side (more hanging PO can also reduce viscosity, and the price can not come down), so, on average, 4 degrees of functionality can deal with a sloppy; In addition, if the polyether system Aromatic structure (benzene ring) is introduced, no doubt will also enhance the physical properties of the foam.
3. Reactivity. Polyether containing primary hydroxyl structure (and small molecules such as triethanolamine cross-linking agent) activity is high, but more or less will affect the foam reaction in the late liquidity. Therefore, the amount of its addition must be controlled within a certain ring.
4, hydroxyl value with. According to the amount of water, black and white material ratio preset, you can roughly back-calculate the average hydroxyl value range of the main part, generally 380-410mgKOH/g.
5、Economy. Not only refers to polyether, polyester procurement price is low, should also be integrated with other aspects to consider the proportion of black and white materials, after all, now the price of black materials is high.
6, the convenience of the market procurement. It is difficult to adjust a formula, the result of raw materials on the market just you useful others will not ask for, unless the wealth of the monthly amount of amazing, otherwise the ingredients supply can guarantee only depends on the “friendship” shallow.
The choice of levelling agent (silicone oil)
1, and other components of the combination of compatibility. This is not difficult to understand, otherwise, the production of silicone oil manufacturers will not make up so many models —— what F11 type, 141B type, cyclopentane type, full water type, polyester type, sucrose polyether type and so on. The silicone oil model is properly matched, it can obviously control the low limit of thermal conductivity.
2、Matchability with black material, nucleation ability. Not many people are concerned about this. In fact, in most cases, the “bad bubble hole” is the result of the silicone oil’s emulsification ability to the whole system of black and white materials is not enough.
3、Flowability. Can make the foam system pore fine silicone oil can obviously enhance the foam liquidity, while another supporting evidence is: foam speed slightly accelerated.
4、Stability and dosage. Some silicone oil met with water, alkaline catalyst, chlorine foam or chlorine flame retardant will gradually deteriorate; some must increase the dosage (dosage of 2.5% or more) to show that it is a silicone oil.
5, price. Can use 22 yuan / kg to get the need to use the imported 45 yuan / kg, to know that each ton of combination material in the silicone oil 14kg that the difference is over 200 yuan.
Determination of the share of water
1, bonding. Water dosage, the surface of the bubble body is brittle, and the bonding of the shell surface is poor, general refrigerator, freezer material water dosage 1.7-2.3% (specifically 141B system and cyclopentane system).
2, the selection of physical foaming agent system. Now everywhere shouting environmental protection, 141B has long been said to be limited use, but under the market there are actually F11 type (or blending type F11) combination material transactions. The amount of water can only follow the line price: F11 type — 0.6/1.6, 141B type — 1.7/2.2, cyclopentane type — 2.0/2.4.
3、Economy. Water is indeed very cheap, but it uses more, the amount of black material will have to be added, so it is still not cost-effective chances (naturally, it is the customer who uses the combination of materials to pay for.
Catalytic system to determine
1. Pre-requirement. In the past, many friends think that the milky white hair is slower to start, and then straighten up after the material flows to the bottom of their respective “posts”. In fact, it is not, one: the liquid material is very easy to leak out from the gap in the box caused by dirt sticky mold; second: the impact of the fine density of the bubble hole and the overall structure, so as to pull up the thermal conductivity of the bubble body; third: the speed of hair will speed up the foam material marching speed. Generally speaking, out of the gun milky white time 6-8 seconds is the best.
2, medium-term flow. During the foam shaping, medium-term flow time period (wire drawing minus whitening time) the longer the better, to ensure that the bubble body fill all corners of the box, and not to the bubble hole deformation serious. The most ideal state is 3-5 seconds before the start of drawing, the foam has been filled in place, the most distal exhaust hole has obvious escape material appears.
3、Later curing. This requirement does not have to be too strict, anyway, continuous production in the mold is not cold, if the production line has insulation kangdao, not afraid of expiration of the crop.
4、Recommended with Am-1 cyclohexylamine.
Process confirmation
1, foaming system to determine: 141B’s or cyclopentane’s. The range of water volume/physical foaming agent volume is predetermined
2、First make clear the process details of the target production line: the type of foaming machine, infusion flow rate, temperature control value before infusion, kangdao insulation temperature control value and insulation time, where the box infusion port and the flow of foam through the route itinerary, the operation process of closing the mold and sealing the hole after infusion.
3、The current (working) environment temperature and humidity changes.
4. Ask the site operator and quality inspector what defects there are in the current process and raw materials and ask them to put forward any other specific requirements.
Specific tests
1, phase solubility: ① 100ml small beaker with a short glass rod, zeroed, in turn, pour in the main polyether (polyester) stir well to see if transparent. ② Add silicone oil, catalyst, water, stir well and see if it is transparent. ③Add physical foaming agent and stir well to see if it is transparent (note that the physical foaming agent evaporated after stirring should be replenished). ④The pre-mixed combination material sample should be stored for at least 3 days to be transparent without delamination. ⑤ combination of material samples were put in 35, 15 ℃ storage 24hr to see whether transparent ⑥ conditions, the need to measure the design of the combination of material viscosity (25 ℃ and the normal production state temperature) to see if the viscosity changes with the temperature has a substantial fluctuation.
2, shrinkage resistance: free foam sample 1hr after cutting into a regular square body, measuring the size of the fixed edge in the -20 ℃ freezer 24hr to see the size change, within 2% of the linear shrinkage is acceptable.
3, free foam: according to the design of the ratio of black and white material, temperature control implementation of free foam, pay attention to the material speed, core density and drawing traces.
4, fluidity: free foam density, speed to determine the fluidity test must be carried out. The simple method is: quantitative foam material (generally 200g) stirring immediately after the mouth of the foam cup set on a slightly larger long plastic bag, straighten the vertical up to let the foam material grow upward until the shape (to two people to operate). Cup mouth to the top height L and the ratio of material weight G will be used as an important parameter to assess the fluidity of the combination of materials, the greater the L / G, the better the fluidity, after which the core density should be measured in sections as an auxiliary reference (from low to high density difference can not be too large, otherwise the fluidity can not be regarded as good, especially the highest point of that section) in fact, if the test is done more, in the normal free bubble foam, you can look at the residual bubble in the cup The shape of the residual bubble to roughly determine the advantages and disadvantages of mobility: the more like mushrooms after the bubble to the cup, the better, the more like a straight stick is the worse.
5, process conditions tolerance: ① the implementation of preset temperature control 3, -3 ℃ foaming, to see whether to maintain good fluidity and bubble hole structure (“fast material” and “slow material” bubble hole can not fall too far) ② constant amount of white material, black material amount 10%, -10 % of the free foam test, at room temperature for 30 minutes when the bubble body does not shrink significantly even if it passes.
【Trial production】 of “refrigerator, freezer” category
This is simple, the whole barrel of material on the machine trial production, according to the predetermined (or the reality of the implementation) of the process conditions of production, the finished product installed in the machine to play cold, to see the box shrinkage and insulation. General procedures: trial production box in the finished bubble body to take samples to test the thermal conductivity and other comprehensive data. The site needs to be fine-tuned generally: foam temperature control, black and white material ratio, adding catalyst, maturation temperature adjustment.
Wood-like products of the combination of material / process control (internal discussion version)
White material system requirements and product requirements]
1、White material viscosity: it is related to the initial fluidity (machine foaming type), mixing effect (including manual foaming type) and the size of the gun flow and the ratio of black and white material, in principle, should not be higher than 2000mPa.S (25℃, the same below), except for high density (free foam density above 130kg/m3).
2、Compatibility: unless the present match is used or white material on the whole barrel of the machine while stirring, white material should be transparent and not layered (if the choice of low cloud point of silicone oil white material may also be opaque at low temperature, but can not be layered), the manual material is more so.
3, fluidity: general imitation wood material fluidity requirements are not too high, which depends on its own production process of reasonable arrangements. For special size closed mold casting products or require material foaming process to have good fluidity, at least it will affect the product density distribution
4, adapt to the black material varieties and black and white material ratio changes: white material system is best to be able to switch the black material varieties (M20S, 44V20, 5005, etc.) under a slight adjustment of process parameters (material temperature, tube pressure, etc.) or within a reasonable fluctuation of black and white material ratio to ensure that the products meet the requirements.
5、Product appearance crust thickness and hardness: imitation wood products at least to ensure that the surface “hard enough”, generally require a certain thickness of the skin to ensure that the surface hardness. Specific indicators are difficult to quantify because of the product density requirements and operating environment temperature, humidity changes and other factors. Some special products are required to be rigid inside and outside, and can even play self-tapping screws without slipping.
6, product surface finish and bubbles: the surface of the product should be bright and clean, there can be no bubbles, pinhole, dark bubbles (the back of some products can reduce the requirements, such as picture frames, wall hanging).
7, white line: this is the most likely to appear defects (the surface of the product appears irregular white block spot, long line spot, the place is obviously soft), to try to avoid, at least the white spot should be hard enough.
8、Fine density of bubble hole: the internal bubble hole of the product is dense and proportional, and the less the large bubble eye (diameter 0.2mm or more), the better.
9、Lacquer and gold foil: products do not flake and bulge after spraying or pasting gold foil.
10, deformation resistance: stable products, long size embryo products after opening the mold not only can not “see cold shrinkage”, the final product across the ocean through the cold and heat can not be deformed.
11, impact resistance: sufficient toughness (usually can withstand 1 meter high flat drop, throwing drop).
12, the surface of the product corrosion resistance: before painting the foil, the product often needs to be washed with solvent to remove the release agent, roughening treatment, can not pass this level Ken
