- Introduction of PVC and Various Auxiliaries
PVC plastic formula is mainly composed of PVC resin and additive composition, wherein the additive according to the functions are divided into: heat stabilizer, lubricant, processing modifier, impact modifier, filler, anti-aging agent, coloring agent and so on. Before the design of PVC formula, we should first understand the properties of PVC resin and various auxiliary agents.
Raw materials and auxiliaries
The resin for the production of PVC plastics is polyvinyl chloride resin (PVC). PVC is a polymer made from vinyl chloride monomer. The output of PVC is only second to PE, which is the second place.
Due to the polymerization of PVC resin dispersant can be divided into different types of osteoporosis (XS) and compact (XI) two. Loose particle size is 0.1 0.2mm, irregular surface, porous, a cotton ball, easy absorption of plasticizer, compact size is below 0.1mm, the surface of solid rules. A table tennis ball, not easy to absorb plasticizer, currently use loose more.
PVC can be divided into ordinary grade (toxic PVC) and health "(non-toxic PVC). The sanitary requirements of vinyl chloride (VC) was lower than lOXl0-6, can be used for food and medicine. The synthesis process is different, PVC can be divided into PVC and PVC. suspension emulsion method according to the provisions of the general national standard GB / T5761-93< suspension PVC resin inspection standard >, suspension PVC divided into PVC-SGl to PVC-SG8Jk resin, in which the smaller the number, the greater the degree of polymerization, the molecular weight of greater intensity is higher, but the melt flow more difficult, processing more difficult. Specific choices, do soft products, generally use PVC-SGl, PVC-SG2. PVC-SG3, need to add a plasticizer. Such as PVC membrane with SG-2 resin, adding 50~80 phr plasticizer. While processing hard products, generally without or with very small amounts of plasticizer, so use the PVC-SG4, VC-SG5, PVC-SG6, PVC-SG7, PVC-SG8. PVC pipe using SG-4 tree Fat, plastic profiles using SG-5 resin, hard transparent film using SG-6 resin, hard foamed profile using SG-7, SG-8 and PVC paste resin. The emulsion method is mainly used for artificial leather, wallpaper and floor leather and plastic products. With PVC resin PVC resin factory according to the degree of polymerization (degree of polymerization is the number of units the chain link is equal to the degree of polymerization multiplied by the molecular weight of polymer molecular weight) classification, such as PVC resin in Shandong Qilu Petrochemical factory production, the factory's products for SK-700; SK-800; SK 1000; SK 1100; SK-1200. The corresponding SG-5 resin polymerization degree of 1000 - 1100.
PVC powder is a white powder, and its density is between 1.35 and 1.45g / cm3. Apparent density is 0.4-0.5g / cm3.. The content of plasticizer can be soft and hard. The content of plasticizer is 0-5 parts, hard parts, 5-25 parts are semi-rigid products, more than 25 parts are soft products.
PVC is a non crystalline polymer polarity, softening temperature and melting temperature of high pure PVC will generally be in the 160 - 210~C is plasticizing polar bond, because of large molecules between the PVC display performance is hard and brittle. Moreover, PVC compounds containing chlorine group, when the temperature at 120~C, pure PVC began to appear off the HCl reaction, will lead to thermal degradation of PVC. Therefore, in the processing of various additives to be added to the process modification and the impact of the modification on PVC, which can be processed into useful products.
PVC resin is mainly used for the production of various kinds of thin films (such as daily printing film, industrial packaging film, agricultural greenhouse film and heat shrinkable film etc.), various types of plate, sheet (the sheet can be used for plastic products), various types of pipes (such as non-toxic water, building threading pipe, transparent hose), the profile (e.g. door, window, decorative plate), blow molding (used for cosmetics and drinks), cable, all kinds of injection molding products and artificial leather, floor leather, plastic toys and so on.
Pure PVC resin is very sensitive to heat, when heating temperature reached 90Y above, there will be a slight thermal decomposition reaction, when the temperature rises to 120C decomposition reaction intensified, in 150C, 10 minutes, PVC from the original white resin will gradually become yellow to red - Brown - Black.PVC resin decomposition process is due to a series of chain reaction and HCL reaction, resulting in large molecular chain fracture. To prevent thermal stability mechanism of thermal decomposition of PVC is through the following aspects to achieve.
By capturing the thermal decomposition of PVC produced by HCl, prevent HCl catalytic degradation of Qihong lead salt stabilizer QY-298 main types according to this mechanism, in addition to metal soap, organic tin, phosphite lipid and epoxy etc... replacement reactive allylic chlorine atoms. Metal soap, phosphorous and organic acid esters tin can act according to the mechanism of the reaction and free radical, free radical termination reactions. Qihong organic tin stabilizer YJ-906 and phosphite ester by this mechanism. With the addition of conjugated double bonds, inhibit the growth of conjugated chain. Organic tin and epoxy by this mechanism. The decomposition of peroxide, the number of the reduction of free radical. The organic tin YJ-906 and phosphite ester by this mechanism. The passivation metal ions catalyzed by HCl. The effect of organic tin stabilizer for YJ-906: PVC transparent products, with high thermal stability and excellent initial coloring, pure color Net, little gas, no precipitation.
The role of lubricants is to reduce the friction between materials and materials and the surface of processing equipment, thereby reducing the flow resistance of melt, reducing the viscosity of melt, improving the fluidity of melt, avoiding adhesion between melt and equipment, and improving the surface finish of products.
According to the different molding methods, the lubrication effect is different.
1.Calendering, to prevent the melt adhesive roll;
2.Injection molding, improve flow and improve demoulding.
3.Extrusion molding to improve flow and increase the separability of die.
4.The pressing and laminating molding will help the separation of the plate and the product.
Classification of lubricants:
1. According to the composition of lubricants, there are mainly saturated hydrocarbons and halogenated hydrocarbons, fatty acids, fatty acids, aliphatic amines, metal soaps, fatty alcohols and polyols.
2. According to the function of lubricant, it is divided into internal and external lubricants.
The main difference is its compatibility with the resin. The internal lubricants are highly affinity to the resin, and their action is to reduce the intermolecular force. The affinity between the external lubricants and the resins is small, and its effect is to reduce the friction between the resin and the metal surface.
The internal and external lubricant is relative, there is no strict criteria. In the resin of different polarity, and external lubricant may change. For example, stearic acid amide alcohol, stearic acid, butyl stearate and stearic acid monoglyceride on polar resin (such as PVC and PA), from within lubrication; but for nonpolar resin (PE, PP), is displayed outside the lubrication function. Instead, polymer paraffin and polar resin compatibility is poor, such as in polar PVC used as lubricant, and in PE, as in the lubricant PP nonpolar resin.
In different processing temperatures, external lubricant will change, such as stearic acid and stearic alcohol for early PVC calendering, due to low processing temperature, bad compatibility with PVC, the main external lubrication; when the temperature rises, and the compatibility of PVC is increased, turn up in lubricant.
According to the lubricant composition can be divided into: saturated hydrocarbons, metal soap, aliphatic amide, fatty acids, fatty acid esters and fatty alcohols.
1. saturated hydrocarbons
According to the polarity of saturated hydrocarbons can be divided into non polar hydrocarbons (such as polyethylene wax and polypropylene wax), polar hydrocarbons (such as chlorinated paraffin, polyethylene oxide). Saturated hydrocarbons by molecular weight can be divided into liquid paraffin; (C16-C21) (C26-C32), solid paraffin and microcrystalline wax (C32-C70) and low molecular weight polyethylene (molecular weight 1000 - 10000), mainly used for non-toxic PVC lubricant.
(1) commonly known as liquid paraffin oil, a colorless transparent liquid, transparent outer lubricants can be used as a PVC, 0.5 phr, the large amount of serious impact on the strength of fillet weld.
(2) Solid paraffin, also known as natural paraffin, white solid, can be used as an external lubricant for PVC, the amount of 0.1 to 1 copies, the dosage is too transparent to influence the transparency.
(3) Microcrystalline paraffin, also known as high melting point paraffin, is white or light yellow solid. It is called microcrystalline paraffin wax due to crystal size. Its lubricating effect and thermal stability are better than those of other paraffins. The amount used in PVC is generally less than 0.1-0.3.
(4) low molecular weight polyethylene (PE), also known as polyethylene wax, is white or light yellow solid powder. It has poor transparency and can be used for PVC extrusion and calendering external lubricants. The dosage is generally less than 0.5 parts.
(5) Oxidized polyethylene wax is a partial oxidation product of polyethylene wax. Its appearance is white powder. It has excellent internal and external lubrication effect, good transparency, low price and dosage in 0.2-1.0 parts.
(6) Chlorinated paraffin, good compatibility with PVC, poor transparency, good effect with other lubricants, suitable for less than 0.5 copies.
2. metallic soap type
Heat stabilizer is a fine, it is a kind of lubricant, the external lubrication, with different varieties on slightly different lubrication with calcium stearate, lead stearate is the best.
3. Aliphatic amines
They consist of two main categories: mono fatty acid amide and double fatty amide. The main fatty acids are mainly N, N., ethylene, double ricinamide and so on.
4. Fatty acids
Such as Qi Hong stearic acid G01, a lubricant widely used only after metal soap, can be used for PVC when the dosage is small. It plays an internal lubrication role. When the dosage is large, it plays an external lubrication role. The addition of stearic acid is less than 0.5 copies.
5. aliphatic ester
(1) stearate butyl ester, the appearance of colourless or yellowish oil like liquid, in the PVC within the main lubrication and external lubrication, 0.5 - 1.5 portions.
(2) Glycerin monostearate, code GMS, is white wax solid. It is PVC excellent internal lubricant, and has little effect on transparency. The added amount is less than 1.5 parts, and it can be used with stearic acid.
(3) ester wax and saponified wax, mainly refers to the lignite wax as the main raw material, after the bleaching process and other processes. The bleached wax has S wax and L wax, saponified wax has 0 wax and OP wax. It is mainly used for HPVC, the amount of 0.1-0.3.
6. fatty alcohol
Stearyl alcohol, the appearance of fine white beads, has internal lubrication, good transparency, the amount of 0.2-0.5 in PVC. PS can also be used as high temperature lubricant. Qihong GW-916 916 is a high molecular polymer oxidation, functional additives an excellent, suitable for PVC foam sheet products increase the plastic film, at the later stage, increasing the extrusion torque. As a PVC high temperature lubricant, the amount of 0.2-0.5.
1. the principle of action of processing auxiliaries
Due to the poor ductility of PVC melt, it is easy to cause melt fracture. PVC melt relaxation is slow, and it can cause rough surface, luster and shark skin. Therefore, PVC processing often requires additional processing aids to improve its melt defects.
Processing aids are additives that can improve the processability of resins. There are three main ways of action: promoting resin melting, improving rheological properties of the melt and giving lubrication function.
1. Promote the resin melt: PVC resin in heating condition, melting at a certain stress when processing modifier first melted and adhered to the surface of PVC resin particles, compatibility and its molecular weight and its resin, PVC viscosity and friction increase, thereby effectively the transmission of stress and shear the heat to the PVC resin, the acceleration of PVC melt.
2. Improving melt rheological properties: PVC melt has many disadvantages such as poor strength, poor ductility and melt fracture. Processing modifier can improve the rheological properties of melt. Its action mechanism is to increase viscoelasticity of PVC melt, so as to improve die expansion and melt strength.
3. Give lubrication: processing modifier and PVC compatible part to promote melting, melting; and incompatible with PVC part migration to the molten resin system, thereby improving the releasability. PVC processing modifier K-311 is a polymerization process prepared by emulsion acrylic processing aids, can promote the promotion of PVC in low temperature under the melting, melting PVC enhanced the cohesion and homogeneity, reduce the processing temperature.
Give products excellent transparency, especially suitable for high transparency products and high-grade profiles. Improve the rheological properties of PVC, promote the plasticization and melting of PVC resin, and improve the appearance quality of products. It is especially suitable for processing and shaping PVC high transparency products.
2. a common processing modifier ACR
ACR is a copolymer of methyl methacrylate and acrylic ester and styrene. It can also be used as impact modifier in addition to processing aids. The ACR of our country can be divided into QH201, QH301 and QH401, QH402. Several brands abroad are K120N, K125, K175, P530, P501, P530, and so on.
The important role of ACR processing modifier is to promote the fusion of PVC, shorten plasticizing time, improve the uniformity of plasticization, reduce the plastic flower temperature. Table 4 is BLANBENDE plastometer measured ACR on plasticizing time, influence of temperature. The general use of ACR201 or ACR401 in PVC plastic profiles. Dosage is 1.5-3.
One of the most important content of the modification of polymer materials is to improve the impact resistance performance of PVC resin is a non crystalline polymer, there is a strong force between molecules, is a hard and brittle material; impact strength is low. With impact modifier, impact modifier elastomer particles can reduce the total craze initiation stress, and the deformation and shear of the particle itself, prevent craze expansion and growth, absorb the impact energy of materials in person, so as to achieve the purpose. The impact modifier particles is small, increasing the number of per unit of weight or volume modifier in order to, so that the effective volume fraction increased, thereby enhancing the ability of dispersing stress. At present widely used as organic anti impact modifier.
According to the internal structure of the organic anti impact modifier, it can be divided into the following categories:
1. A predetermined elastomer (PDE) type impact modifier, which belongs to the core-shell structure of the polymer, the core is soft like elastic, anti shock performance products to give high, shell has high glass transition temperature of the polymer, the main function is to make the mutual isolation between the modifier particles, forming a free the flow of the component particles in the polymer, promote the dispersion of reinforced between modifier and polymer interaction and compatibility. This kind of structure modifier: MBS, ACR, MABS and MACR, these are excellent impact modifier.
2. Non scheduled elastomeric (NPDE) impact modifier, which belongs to the network polymer, its modification mechanism is to solvation (plasticization) modification of plastic mechanism. Therefore, NPDE must form a resin coated mesh structure, it is not very good compatibility with the resin body. This kind of structure modifier: CPE, EVA.
3. Excessive impact modifier, whose structure is between two structures, such as the specific varieties of ABS. for PVC resins:
(1) (CPE) is a chlorinated polyethylene powder products were suspended in aqueous chloride by HDPE, with the increase of the degree of chlorination the original crystalline HDPE elastomer has gradually become amorphous. Used as toughening agent C? E, C1 content is generally 25-45%.CPE wide source, low price, in addition to a toughening effect outside, also has the cold resistance, weather resistance, flame resistance and chemical resistance. At present in our country, CPE is the dominant impact modifier, especially in the PVC pipe and profile production, most factories use the added quantity of CPE. is generally 5 - 15.CPE with other toughening agents used together better such as rubber, EVA, rubber additive effect, but not resistant to aging.
(2) ACR methyl methacrylate copolymer of acrylate monomer, ACR as the development in recent years, the best impact modifier, it can make the impact strength of the material increases several times to.ACR core-shell impact modifier, composed of methyl methacrylate acrylic ester polymer shell, rubber elastomer forming the crosslinking of butyl acrylate as core segment distribution in the inner particles. PVC plastic product is especially suitable for outdoor use, the impact of modification, the use of ACR in PVC plastic profiles as impact modifier and other modifiers compared with good processing performance, smooth surface, good ageing resistance, the characteristics of fillet weld high strength, but the price is higher than CPE, 1 / 3. Foreign common brands such as K-355, the general amount of 6 - 10. The current domestic production of ACR impact modifier manufacturers use less, manufacturers are also less.
(3) MBS is methyl methacrylate, styrene butadiene and solubility parameters of three kinds of monomer copolymer.MBS is between 94-9.5, close to the solubility parameter of PVC, so PVC has good compatibility, its biggest feature is: after the addition of PVC can be made of transparent products. In general PVC with 4-6 copies, the impact the intensity of PVC increased 6 - 15 times, but the amount of MBS is more than 30 phr, the impact strength of PVC decreased the.MBS itself has good mechanical properties, good transparency, light transmission rate can reach more than 90%, and in improving the impact at the same time, other properties of the resin, such as tensile strength, elongation at break and impact is small.
Qihong BS-156 is well developed with synthetic resin technology advanced MBS products, which is composed of Methyl Methacrylate Butadiene Styrene copolymer, and a three yuan, is a comprehensive resin with improved impact strength and processability of PVC products. The addition of BS-156 in PVC formulation, the impact strength of products can be improved and the inherent characteristics of PVC, with no adverse effects. It is widely used in PVC film, transparent sheet, pipe, pipe fittings, bottle pellets and other products.
(4) ABS (40%-50%), styrene butadiene (25% - 30%), acrylonitrile (25%-30%) copolymer three yuan, mainly used as engineering plastics, also used as PVC impact modified, on low temperature impact modification effect is also very good.ABS added up to 50 phr, the impact strength of PVC and pure ABS considerable amount of.ABS is 5 - 20, ABS poor weather resistance, not suitable for long-term outdoor use products, generally do not do plastic profile production impact modifier.
(5) EVA is the ethylene vinyl acetate copolymer by acid, vinyl acetate changed the crystallinity of polyethylene, vinyl acetate content of a large number of poor, and the EVA and PVC index is different, it is difficult to get transparent products, therefore, often EVA and other impact resin and.EVA addition amount is less than 10 copies.
4, rubber impact modifier
The performance is excellent toughening agent, the main varieties are: ethylene propylene rubber (EPR), three EPDM (EPDM), nitrile rubber (NBR) and styrene butadiene rubber, natural rubber, butadiene rubber, chloroprene rubber, polyisobutylene, butadiene rubber, EPR, EPDM, NBR three is the most commonly used. To improve the impact resistance of superior low temperature, but not aging, plastic windows generally do not use this kind of impact modifier.
Other commonly used auxiliaries
1, light stabilizer
Most of PVC products are exposed to sunlight and other kinds of light. A certain amount of light stabilizers can be used to prevent and delay their decomposition and aging, and prolong their service life according to the application environment of products.
The light stabilizers can be divided into four categories:
(1) a light shielding agent. Such as titanium dioxide and carbon black, can block UV into the material, to prevent degradation of polymer. Such as LDPE sheet with 2% carbon black resistance LDPE material aging degree than carbon black increased by 20 times. There is a big increase of titanium dioxide aging degree of material, titanium dioxide should be the use of rutile, used in PVC plastic profiles in 3-6.
(2) Ultraviolet absorber can absorb ultraviolet radiation of 280-400nm and convert it into visible light or heat. Commonly used products such as UV - 531, UV-327, UV-326, UV-p and so on are usually 0.1-0.5%., but the price is higher.
(3) Quench agent is mainly used to destroy the energy of the excited polymer molecule and make it return to the ground state. The specific variety is nickel cobalt complex, its light stabilizer 2002, light stabilizer 1084 and so on. Generally it is used in combination with other light stabilizers, the dosage is 0.1-0.5%.
(4) Free radical scavenger. Is a kind of efficient light stabilizer, it captures the light degradation of the decomposition of free radicals, terminate the degradation reaction. Generally used in LDPE film. The main varieties are: light stabilizer GW-540, GW - 544, CW-310, BW, 10LD, light stabilizer 744, light stabilizer 622, light stabilizer 944, the amount of 0.02-0.5%.
The main purpose of using fillers is to occupy space to reduce costs. Of course, some fillers also give some special properties to the material, such as flame retardancy, electrical conductivity, heat conduction, rigidity, etc.
The main indexes of fillers are whiteness, particle size, particle shape and particle surface activity.
The main varieties are:
(1) the main carbonates are heavy calcium carbonate, light calcium carbonate and active calcium carbonate. The light calcium carbonate is usually used in the PVC plastic section.
(2) Carbon black, such as natural gas tank black, mixed gas tank black, high wear resistant furnace black, hot cracking carbon black, acetylene carbon black and so on, mainly affects the reinforcement of rubber, and some varieties are also used as filler, such as conductive and antistatic polymer products.
(3) Barium sulfate, calcium sulfate, lithopone (Li Defen), mainly as fillers, also a coloring agent of barium sulfate can reduce the X light permeability.
(4) Metal oxides, such as alumina, iron oxide, manganese oxide, Zinc Oxide, antimony oxide, Magnesium Oxide, iron oxide, magnetic powder, etc., are used as filler and colorants.
(5) The metal powder such as aluminum, bronze, zinc, copper, lead powder, as a decoration and improve thermal conductivity. In the production of plastic profile in the sometimes used copper, aluminum aluminum profiles production imitation.
(6) The most commonly used ceramic clay in silicon compound is kaolin, a filling agent. The hard clay has a reinforcing effect. The talcum powder is used as a filling agent.
(7) Fibers, such as glass fiber, boron fiber, carbon fiber, etc., are used as enhancers.
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