在工業涂料中、粉末涂料在制備和成膜過程中的相變化是共同的。由于缺乏溶劑來潤濕和進步涂膜活動性,招致粉末涂料比液體涂料更難去除外表缺陷。固然兩者的主要組份相似,但相比于液體涂料、熱固性的粉末涂料立足于非常不同的機理.
In industrial coatings, the phase change of powder coatings during preparation and film formation is common. Due to the lack of solvent to wetting and improve the film activity, resulting in powder coating than liquid coating more difficult to remove surface defects. Although the main components of both are similar, but compared to liquid coatings, thermosetting powder coatings based on very different mechanisms.
粉末涂料是無溶劑的均一體系。在濟南氟碳噴涂過程中,顏料和其它組份經過熔融混合被分散和局部包裹于低分子固體樹脂中。粉末涂料運用是經過空氣把粉末傳送到底材上(粉末懸浮于空氣中),再經過電荷使之附著于底材上。在預定的溫度下加熱,使粉末顆粒凝結、匯集在一同(聚結),活動(成膜),接著流平,這期間經過一個有粘性的液態階段潤濕外表),最后化學交聯構成高分子量的涂膜,這就是粉末涂料的成膜過程。
Powder coatings are solvent free homogeneous systems. During the fluorocarbon spraying process in Ji'nan, pigments and other components were dispersed and partially encapsulated in low molecular solid resin by melt mixing. Powder coating is the use of air through the powder to the end of the material (powder suspended in the air), and then through the charge to attach to the substrate. Heating at a predetermined temperature, the powder particle coagulation, together (coalescence), activity (Cheng Mo), then leveling, during this period after a viscous liquid phase appearance), finally wetting chemical crosslinking of high molecular weight coating composition, film formation process which is powder coating.
粉末涂料的桔皮問題
Orange peel of powder coatings
影響涂膜活動和外觀的要素：
Factors affecting coating activity and appearance:
濟南氟碳噴涂的成膜過程可分為熔融聚結,構成涂膜,流平三個階段，在給定溫度下,控制熔融聚結速度最重要的要素是樹脂的熔點、熔融態粉末顆粒的粘度以及粉末顆粒的大小。為了使活動效果最佳,熔融聚結應當盡可能快地完成,以便有較長時間來完成流平階段。固化劑的運用縮短了可供活動和流平所需的時間,因此那些極為活性的粉末構成的涂膜常呈現桔皮。
Ji'nan fluorocarbon spray coating process can be divided into melting and coalescence, a film, leveling three stages, at a given temperature, melting and coalescence velocity control elements is the most important resin melting point, the viscosity of molten particles and powder particle size. For best activity, melt coalescence should be done as quickly as possible to allow for a longer period of completion of the flow stage. The use of curing agent for activities and shorten the leveling time required, so the film is extremely active powder which are often orange peel.
影響涂膜活動和流平的關鍵要素是樹脂的熔融粘度、體系的外表張力和膜厚。轉而,熔融粘度特別取決于固化溫度、固化速度和升溫速率。
The key factors that affect the film activity and flow are the melt viscosity, surface tension and film thickness. In turn, melt viscosity depends particularly on curing temperature, curing rate and heating rate.
以上提及的種種要素,連同粒徑散布和膜厚,通常由所請求的涂膜性能、被涂物件和粉末施工條件等所決議。
The above mentioned factors, together with particle size distribution and film thickness, are usually determined by the requested film properties, coated articles and powder construction conditions.
粉末噴涂時活動和流平的動力來自體系的外表張力,這一點前面也曾經提到。該作用力同施加到涂膜上的分子間引力相反,其結果招致如熔融粘度越高,則對立活動和流平的阻力越大。因而,外表張力和分子間引力之間的差值大小決議著涂膜流平的水平。
The kinetic and kinetic forces of powder spraying come from the apparent tension of the system, which is mentioned previously. The force is opposite to the molecular weight applied to the coating, which results in the higher the viscosity, the stronger the opposing activity and the flow resistance. Thus, the difference between the apparent tension and the intermolecular gravity determines the level of film leveling.
關于活動性很好的涂料，顯然,該體系的外表張力應盡可能高,且熔融粘度盡可能低。這些可經過參加能提高體系外表張力的助劑和運用低分子量低熔點的樹脂來完成。
On the very good activity of paint, obviously, the system should be as high as possible surface tension, and melt viscosity as low as possible. These can be used to participate in the system can improve the external tension and use of low molecular weight low melting point resin to complete.
依據以上條件制備的涂料能具有極好的活動性,但是由于其高的外表張力會招致縮孔,同時由于較低的熔融粘度會產生流掛,且邊角涂覆性差。實踐工作中,體系的外表張力和熔融粘度都控制在特定范圍內,這樣可得到合格的涂膜外表外觀。
Coatings prepared according to the above conditions can have excellent activity, but due to their high surface tension will lead to shrinkage, while due to lower melt viscosity will produce flow hanging, and poor coating angle. In practice, the surface tension and melt viscosity of the system are controlled in a specific range, so that qualified film appearance can be obtained.
外表張力和熔融粘度對涂膜活動的影響見圖2。圖中能夠看到,太低的外表張力或太高的熔融粘度會阻止涂膜活動,招致涂膜活動性差,而外表張力太高時成膜過程中會呈現縮孔。熔融粘度太低會使粉末的物理儲存穩定性變差,施工時邊角涂覆性差,且施工于立面時產生流掛。
The effect of surface tension and melt viscosity on the film activity is shown in figure 2. It can be seen that too low surface tension or too high melt viscosity will prevent coating activity, resulting in poor film activity, and the surface tension is too high during the film formation will show shrinkage. Melt viscosity is too low will make the powder physical storage stability is poor, the construction angle coating bad, and construction in the facade when flow hanging.
綜上所述,很明顯,得到的粉末涂料涂膜最后的外表情況、缺陷和缺乏(如桔皮,活動性差,縮孔,針孔等)是互相親密關聯的,同時也被在成膜過程中參與相變的流變力所控制。
To sum up, obviously, the appearance of coating film, finally obtained and the lack of defects (such as orange peel, poor activity, shrinkage, pinhole etc.) are close related, controlled by rheological force was also in the film forming process in transition.
粉末顆粒大小散布情況也影響著涂膜的外表外觀。顆粒越小,由于其熱容較大顆粒的低,因而其凝結時間比大顆粒的短,聚結也較快,構成涂膜的外表外觀較好。而大的粉末顆粒凝結時間比小顆粒的長,構成的涂膜就可能會產生桔皮效應。粉末靜電施工辦法(電暈放電或摩擦放電)也是招致桔皮構成的一個要素。
Powder particle size distribution also affects the appearance of the film. The smaller the particle, due to the heat capacity of larger particles is low, so the setting time than larger particles, coalescence is also faster, a film looks good appearance. But the setting time of powder particles than small particles, a film might have orange peel effect. The construction method of electrostatic powder (corona discharge or friction) also lead to an element of orange peel.
怎樣減小或防止桔皮效應
How to reduce or prevent the orange peel effect
促進活動和流平能減少或防止桔皮。體系運用較低的熔融粘度、固化過程中延長流平常間以及較高的外表張力可進步活動和流平性�？刂仆獗韽埩μ荻仁菧p少桔皮的重要參數，同時還要控制涂膜外表的外表張力平均,以取得最小的外表積。
Promotion and leveling can reduce or prevent the orange peel. The system can improve the activity and leveling by using low melt viscosity, prolonging the normal flow and high surface tension. Control of surface tension gradient is an important parameter to reduce the surface tension of orange peel, but also to control the average film appearance, in order to obtain the minimum surface area.
濟南氟碳噴涂實踐工作中常運用活動促進劑或流平劑來改善涂膜外觀,以消弭桔皮、縮孔、針孔等外表缺陷。性能好的活動促進劑能降低熔融粘度,從而有助于熔融混合和顏料分散,進步底材的潤濕性，涂層的活動流平,有助于消弭外表缺陷以及便于空氣的釋放。應調查活動改性劑用量與效果的關系。其用量缺乏會招致縮孔和桔皮,而用量過多又會招致失光、霧影,并產生對上層重涂附著力的問題。通常,活動改性劑在預混時參加。它們或做成樹脂的母料(樹脂和該添加劑的比為9/1～8/2),或者以粉末狀吸附在無機載體上。粉末涂料中該添加劑的用量為0.5～1.5%(在以基料計算的有效聚合物中),但是在濃度較低時可能效果也不錯。
Ji'nan fluorocarbon spraying practice activities often use accelerator or leveling agent to improve the appearance of the coating, in order to eliminate orange peel, shrinkage and pinhole defect in appearance. Good performance of the accelerator can reduce the melt viscosity, thus contributing to melt mixing and pigment dispersion, improve the wettability of the substrate, coating activity flow, help to eliminate the appearance of defects and ease of air release. The relationship between activity modifier dosage and effect was investigated. The dosage will lead to a lack of shrinkage and orange peel, and excessive consumption will lead to the loss of light, fog shadow, and the upper recoat adhesion problem. Usually, the active modifier takes part in premixing. They made of resin masterbatch (resin and the additive ratio of 9/1 to 8/2), or a powder adsorbed on inorganic carrier. The additives used in powder coatings are 0.5 to 1.5% (effective polymers calculated in base material), but the effect may be good when the concentration is low.
活動改性劑中聚丙烯酸酯系樹脂應用最廣,如聚丙烯酸丁酯(“Acronal4F”)、丙烯酸乙酯-丙烯酸乙基己酯共聚物和丙烯酸丁酯-丙烯酸己酯共聚物等。它們可在濃度很寬的范圍內運用。普通聚丙烯酸酯對外表張力影響很小,它們能有助于涂層構成比擬恒定的平均外表。同那些使外表張力降低的添加劑(如硅氧烷等)相比,它們不會降低外表張力,因而可用來加速流平。降低外表張力的添加劑包括外表活性劑、氟化烷基酯以及硅氧烷等。它們對參加量的幾十分敏感。安息香是一種脫氣劑,也有降低外表張力的效果,被普遍用于改善粉末涂料涂膜的外表外觀。
The polyacrylate resin is the most widely used in the modification agent, such as butyl acrylate ("Acronal4F"), ethyl acrylate ethyl acrylate copolymer and butyl acrylate acrylic copolymer. They can be used in a wide range of concentrations. Ordinary polyacrylate has little influence on external surface tension, which can help the coating form a constant average appearance. They do not reduce the apparent tension compared with those additives (such as silicones) that reduce the apparent tension, and thus can be used to accelerate the flow. Additives for reducing surface tension include surface active agents, fluorinated alkyl esters, and silicones. They are sensitive to scores of participants. Benzoin is a degassing agent, also reduce the surface tension effect, is widely used to improve the appearance of the appearance of coating film.
涂層中有氣泡
There are bubbles in the coating
緣由:粉末中含有揮發性的物質和水.,工件外表有水,緊縮空氣中有油或水
Reason: powder contains volatile substances and water, the workpiece surface water, compressed air with oil or water
辦法:增強粉末的保管,防潮,烘干工件的外表水份.對緊縮空氣停止除油,除水
Approach: to enhance the custody of powder, moisture, drying the workpiece surface moisture.
涂層呈現針孔,凹膜,
The coating presents a pinhole, a concave film,
涂層過厚,形成靜電排擠,噴槍距工件太近,形成打火擊穿,工件外表有油脂和水份,粉末含水量大,緊縮空氣中含有油或水,工件自身有針孔,
The coating is too thick, the formation of electrostatic exclusion, the gun from the workpiece is too close, the formation of spark breakdown, workpiece surface with moisture and oil, powder containing water, oil or water containing compressed air, the workpiece itself has a pinhole,
涂層厚度不均
Uneven coating thickness
粉末噴涂速度不均,緊縮空氣不穩定,供粉安裝流化效果不好,保送鏈的速度不穩.粉末受潮結困而招致的流化效果好.
Powder spraying speed is not uniform, the compressed air is not stable, the flow of the powder supply installation is not good, for the speed of the chain is not stable. The powder with trapped incurred by the fluidizing effect.
涂層流掛
Coating flow
涂層太厚,升溫太快,固化溫度太高,烘烤固化前涂層不平均,
Coating too thick, heating too fast, curing temperature is too high, baking curing coating is not average,
涂層光澤不良,變色
Poor coating gloss, discoloration
粉末耐耐熱性能差,固化溫渡過高或時間過長,噴粉與固化工序時間距離太長,前處置脫質不凈,供粉和噴粉系統,回收系統等清算不凈,混入其它種類或顏色的粉末。
Powder heat resistance, curing temperature is too high or too long, too long time and powder curing process before disposal and distance, quality is not a net, and dusting powder supply system, recovery system, clearing dirty, mixed with other types of color or powder.