Plastic additives, also called plastic additives, are some compounds that must be added when polymers ( synthetic resins ) are molded to improve their processing properties or to improve the performance of the resin itself. For example, plasticizers are added in order to lower the molding temperature of polyvinyl chloride resin and make the products soft; and foaming agents are added in order to prepare foam plastics that are lightweight, vibration-resistant, heat-insulating, and sound-insulating; the thermal properties of some plastics The decomposition temperature is very close to the molding processing temperature, and it cannot be molded without adding a heat stabilizer. Therefore, plastic additives occupy a particularly important position in plastic molding processing. A large class of additives used in plastic molded products, including plasticizers, heat stabilizers, antioxidants, light stabilizers, flame retardants, foaming agents, antistatic agents, antifungal agents, colorants and additives. Whitening agent (see pigment), filler, coupling agent, lubricant, release agent, etc. Among them, colorants, whitening agents and fillers are not plastic- specific chemicals, but general compounding materials.

Develop

China’s plastic additives industry has developed with the development of the PVC industry. At the same time, with the development of the plastic synthetic resin industry, the application fields of the plastic additives industry have continued to expand, and the product varieties have increased significantly. The plastic additives industry has become an important industry with relatively complete categories and a wide variety of products. In terms of technology, The level, product structure, production scale and quality of scientific and technical personnel have all made great progress, basically meeting the needs of downstream industries for plastic additive products. At present, China’s plastic additives industry has formed an industry with an output value of more than 30 billion yuan, of which about 5 billion yuan is exported.

Since 2005, the average annual growth rate of China’s plastic additives industry has remained at 8%-10%, which is much higher than the 4% average annual growth rate of the world’s plastic additives. The plastic additives industry has also received attention from various national departments and has gradually become an important member of the new materials field with the greatest development potential in recent years. During the “Eleventh Five-Year Plan” period, with the rapid development of China’s plastics industry, the production capacity, output and consumption of various plastic additive products have achieved rapid growth. From 2008 to 2010, China’s consumption of plastic additives was approximately 2.73 million tons, 2.82 million tons, and 3 million tons respectively. In 2011, it is expected to be around 3.2 million tons.

During the “Eleventh Five-Year Plan” period, China’s plastics industry showed an obvious trend of industrial agglomeration and development. The number of large-scale enterprises increased rapidly, and the industrial structure gradually adjusted toward large-scale and intensification. The plastic additives industry is also adjusting towards scale and intensification, especially in plasticizers, heat stabilizers, impact modifiers and processing aids.

Plastic additives are indispensable components for the engineering of general plastics and the high performance of engineering plastics, as well as the key to functionalization through modification of synthetic resins. During the “Eleventh Five-Year Plan” period, the development of the entire industry was mainly focused on the large-scale production of general varieties., but it is rare to see the emergence of structural innovative products. At the same time, most of the production uses patented technologies of foreign companies. Therefore, the research and development and production of high-performance green, environmentally friendly, non-toxic, and efficient plastic additives have become the future development of China’s plastic additives industry. main direction of attack. Plasticizers should increase the output of non -phthalate esters, such as epoxidized soybean oil and trimellitates; stabilizers should reduce the proportion of lead salts and increase calcium/zinc composites, low-lead rare earths, and water The output of talc and organic heat stabilizers; flame retardants should reduce the proportion of halogens and vigorously develop inorganic flame retardants. At the same time, we must actively respond to EU environmental regulations requirements for non-toxic and environmentally friendly products. Plastic additive companies should join forces with universities and scientific research institutes to change the unreasonable product structure and develop environmentally friendly additive varieties.

Development history

Plastic additives were gradually developed after the industrialization of polyvinyl chloride. After the 1960s, due to the rise of petrochemical industry, the plastics industry developed rapidly, and plastic additives have become an important chemical industry. According to the differences in the composition of plastic varieties and plastic uses in various countries, the consumption of plastic additives is about 8% to 10% of plastic production. Today, plasticizers, flame retardants and fillers are the most commonly used plastic additives.

Categories

There are many ways to classify plastic additives, and the more popular method is to classify them according to their functions and effects. In categories with the same function, they are often further subdivided according to the mechanism of action or type of chemical structure.

Functional category

Requires

1. It should have good compatibility with the added synthetic resin, be stable for a long time, and be evenly dispersed in the resin.
2. Synergy effect. Try to use plastic additives that can promote the performance of each other.
3. Good durability. Does not dialyze, volatilize, migrate or be extracted by water and liquid substances.
4. Suitable for the use requirements of the product.
5. Better adaptability to processing conditions.
6. It has good dispersibility and can be easily dispersed evenly during processing and molding. These six points can meet the additive requirements for most products. Of course, many PVC products have special requirements for PVC stabilizers, and these requirements are solved in the development of PVC stabilizers.

Plasticizer

Plasticizer is a type of additive that increases the plasticity of polymer resins and gives softness to products. It is also the plastic additive category with the largest production and consumption so far. Plasticizers are mainly used in PVC soft products and are also widely used in polar plastics such as cellulose. The categories of compounds involved in plasticizers generally include phthalates, fatty dicarboxylate esters, trimellitates, polyesters, epoxy esters, phenyl alkyl sulfonates, phosphate esters and chlorinated paraffins, etc., especially phthalates are the most important.

Heat stabilizer

If not specified, heat stabilizers refer specifically to stabilizers used in the processing of polyvinyl chloride and vinyl chloride copolymers. Polyvinyl chloride and vinyl chloride copolymers are heat-sensitive resins. They can easily release hydrogen chloride during thermal processing, which can trigger thermal aging degradation reactions. Thermal stabilizers generally achieve thermal stabilization by absorbing hydrogen chloride, replacing active chlorine and adding double bonds. The types of heat stabilizers widely used in industry generally include basic lead salts, metal soaps, organic tins, organic antimonies and other main stabilizers, as well as epoxy compounds, phosphites, polyols, and Ketones and other organic auxiliary stabilizers. Composite stabilizers, which are composed of main stabilizers, auxiliary stabilizers and other auxiliaries, play a decisive role in the heat stabilizer market.

Processing modifiers

Processing modifiers in the traditional sense almost exclusively refer to modification additives used in the processing of rigid PVC to improve the plasticizing properties, increase the viscoelasticity of the resin melt, and promote the melt flow of the resin. Such additives are based on acrylic acid. Mainly ester copolymer (ACR), which plays a prominent role in the processing of rigid PVC products. The concept of processing modifiers in the modern sense has been extended to polyolefins (such as linear low density polyethylene LLDPE ), engineering thermoplastic resins and other fields. It is expected that newer and wider processing modifications will appear in the next few years after metallocene resins are put into use. Types of sexual agents.

Impact modifier

Broadly speaking, any additives that can improve the impact resistance of hard polymer products are collectively called impact modifiers. Impact modifiers in the traditional sense are basically based on the elastic toughening theory, and the compounds involved almost without exception belong to various copolymers and other polymers with elastic toughening effects. Taking rigid PVC products as an example, the varieties widely used in the application market today mainly include chlorinated polyethylene ( CPE ), acrylate copolymer (ACR), methacrylate -butadiene- styrene copolymer (MBS), Ethylene-vinyl acetate copolymer ( EVA ) and acrylonitrile -butadiene-styrene copolymer (ABS), etc. The ethylene propylene diene rubber ( EPDM ) used in polypropylene toughening modification also belongs to the scope of rubber toughening. After the 1980s, a theory of toughening polymers with inorganic rigid particles emerged. Coupled with the rapid development of nanotechnology, plastic toughening modifications and impact modifiers have been given new meanings. In this regard, a large number of monographs and documents have been reported.

Flame retardant

Most plastic products are flammable, which brings many hidden dangers to the safety of their products. To be precise, flame retardants are more appropriately called flame retardants, because “flame retardant” includes both flame retardant and smoke suppression, and is a broader concept than flame retardants. However, people have been accustomed to using the concept of flame retardants for a long time, so the flame retardants referred to in the literature are actually the general term for flame retardant and smoke suppression functional additives. Flame retardants can be divided into additive flame retardants and reactive flame retardants according to their use methods. Additive flame retardants are usually added to the base resin, and they are simply physically mixed with the resin; reactive flame retardants are generally monomers containing flame retardant elements and reactive groups in the molecule. Such as halogenated acid anhydrides, halogenated bisphenols and phosphorus-containing polyols, etc., due to their reactivity, can be chemically bonded to the molecular chain of the resin and become part of the plastic resin. The structure of most reactive flame retardants is still synthetic additive flame retardant. agent monomer. According to different chemical compositions, flame retardants can also be divided into inorganic flame retardants and organic flame retardants. Inorganic flame retardants include aluminum hydroxide, magnesium hydroxide, antimony oxide, zinc borate and red phosphorus, etc. Organic flame retardants are mostly halogenated hydrocarbons, organic bromides, organic chlorides, phosphates, halogenated phosphates, nitrogen It is a flame retardant and nitrogen-phosphorus intumescent flame retardant. The function of smoke suppressant is to reduce the amount of smoke produced by flame retardant materials andThe amount of toxic and harmful gases released is mostly molybdenum compounds, tin compounds and iron compounds. Although antimony oxide and zinc borate also have smoke suppression properties, they are often used as flame retardant synergists and are therefore classified as flame retardant systems.

Antioxidants

Additives whose main function is to inhibit thermal oxidative degradation of polymer resins belong to the category of antioxidants. Antioxidants are the most important type of plastic stabilization additives, and almost all polymer resins involve the application of antioxidants. According to the mechanism of action, traditional antioxidant systems generally include primary antioxidants, auxiliary antioxidants and heavy metal ion passivators. The main antioxidant has the main function of capturing polymer peroxyl radicals. It is also known as “peroxyl radical trapping agent ” and ” chain termination antioxidant” and involves two major categories: aromatic amine compounds and hindered phenolic compounds. series of products. Auxiliary antioxidants have the function of decomposing polymer peroxy compounds, also known as ” peroxide decomposers”, including thiodicarboxylates and phosphite compounds, and are usually used in conjunction with the main antioxidant. Heavy metal ion passivators, commonly known as “anti-copper agents,” can complex transition metal ions and prevent them from catalyzing the oxidative degradation reaction of polymer resins. Typical structures include hydrazide compounds. In recent years, with the deepening of theoretical research on polymer antioxidants, the classification of antioxidants has also undergone certain changes. The most prominent feature is the introduction of the concept of “carbon radical scavengers “. This kind of free radical scavenger is different from the main antioxidant in the traditional sense. They can capture polymer alkyl free radicals, which is equivalent to adding a line of defense to the traditional antioxidant system. Such stabilizing aids reported today mainly include aryl benzofuranone compounds, bisphenol monoacrylate compounds, hindered amine compounds and hydroxylamineCompounds, etc., the ternary antioxidant system formed by them, primary antioxidants and auxiliary antioxidants can significantly improve the antioxidant stabilization effect of plastic products. It should be pointed out that amine antioxidants have coloring and pollution properties and are mostly used in rubber products, while phenolic antioxidants and their composite antioxidant systems with auxiliary antioxidants and carbon radical scavengers are mainly used in plastics and colorful products. Colored rubber products.

Light stabilizer

Light stabilizers, also known as UV stabilizers, are a type of stabilizing additive used to inhibit photooxidative degradation of polymer resins and improve the weather resistance of plastic products. According to different stabilization mechanisms, light stabilizers can be divided into light shielding agents, ultraviolet absorbers, excited state quenchers and free radical trapping agents. Light shielding agents are mostly carbon black, zinc oxide and some inorganic pigments or fillers, and their function is achieved by shielding ultraviolet rays. UV absorbers have a strong absorption effect on ultraviolet rays and convert harmful light energy into harmless heat energy for release through intramolecular energy transfer, thereby preventing the polymer resin from absorbing ultraviolet energy and inducing photo-oxidation reactions. There are many types of compounds involved in UV absorbers, mainly including benzophenone compounds, benzotriazole compounds, salicylate compounds, substituted acrylonitrile compounds and triazine compounds, etc. The excited state quencher is intended to quench the energy on the excited polymer molecules to return them to the ground state and prevent them from causing further breakage of the polymer chain. Excited state quenchers are mostly nickel complexes. The free radical scavenger uses hindered amine as a functional group, and its corresponding nitroxide radicalIt is the basis for capturing polymer free radicals, and because this nitrogen-oxygen free radical is regenerative during the stabilization process, the light stabilizing effect is very outstanding. So far, it has developed into the light stabilizer category with the most varieties and the largest production and consumption. Of course, the role of hindered amine light stabilizers is not limited to capturing free radicals. Studies have shown that hindered amine light stabilizers often have the functions of decomposing hydroperoxides and quenching singlet oxygen at the same time.

Filling reinforcement system additives

Filling and reinforcement are important ways to improve the physical and mechanical properties of plastic products and reduce matching costs. Reinforcement materials involved in the plastics industry generally include fibrous materials such as glass fiber, carbon fiber, and metal whiskers. Fillers are additive materials with low compounding costs, including calcium carbonate, talc, clay, mica powder, silica, calcium sulfate, fly ash, red mud, and natural minerals such as wood flour and cellulose, synthetic inorganics and industrial by-products. In fact, it is difficult to distinguish between enhancers and fillers because almost all fillers have a reinforcing effect. Since fillers and reinforcing agents are used in large amounts in plastics, some of them have formed their own industry system, and it is customary not to discuss them in the category of processing aids. It should be noted that the modification effect of nano-filled reinforcement materials on plastics that has been widely studied today has gone far beyond the meaning of filling and reinforcement, and their application will bring a new revolution to the plastics industry. Coupling agents are surface modifiers for inorganic and natural filling and reinforcing materials. Since the reinforcing and filling materials in the plastics industry are mostly inorganic materials and the blending quantities are large, direct matching with organic resins often leads to the processing of plastic complexes. Decrease in application performance. As a surface modifier, coupling agents can organicize the surface of inorganic materials through chemical or physical effects, thereby increasing the compounding amount and improving the processing and application properties of the complex. The reported coupling agents generally include long carbon chain fatty acids,Silane compounds, organic chromium compounds, titanate compounds, aluminate compounds, zirconate compounds, and anhydride- grafted polyolefins, etc.

Antistatic agent

The function of antistatic agents is to reduce the surface resistance of polymer products and eliminate electrostatic hazards that may be caused by static electricity accumulation. According to different usage methods, antistatic agents can be divided into two types: internal type and coating type. Internal antistatic agents are added or blended into the plastic formula. After molding, they migrate from the interior of the product to the surface or form a conductive network, thereby reducing surface resistance and discharging charges. Coated antistatic agents adhere to the surface of plastic products by coating or wetting, thereby absorbing moisture in the environment and forming an electrolyte layer that can discharge charges. Judging from the composition of chemical substances, traditional antistatic agents are almost without exception surfactant compounds, including quaternary ammonium salt cationic surfactants, alkyl sulfonate anionic surfactants, alkanolamines, Nonionic surfactants such as alkanolamides and polyol fatty acid esters. However, the newly emerged “high molecular weight permanent antistatic agents ” break this convention. They are generally hydrophilic block copolymers, which are combined with the base resin in the form of a blended alloy to conduct charges by forming conductive channels. Compared with surfactant antistatic agents, this high molecular weight permanent antistatic agent will not be lost due to migration, volatilization and extraction, so the antistatic properties are long-lasting and stable and are rarely affected by environmental humidity.

Lubricants and release agents

Lubricants are processing modification additives that are blended into polymer resins to reduce the friction between resin particles, resin melt and processing equipment, as well as between molecules within the resin melt, and improve the fluidity and release properties during molding., mostly used in the processing and molding process of thermoplastic plastics, including hydrocarbons (such as polyethylene wax, paraffin wax, etc.), fatty acids, fatty alcohols, fatty acid soaps, fatty acid esters and fatty amides, etc. Release agents can be applied to the surface of molds or processing machines, or added to basic resins to make model products easy to release and improve their surface smoothness. The former is called a coating release agent, which is a release agent. The main body, the latter is an internal release agent, which has the characteristics of easy operation. Silicone oil substances are the most widely used type of release agents in industry.

Dispersant

We know that plastic products are actually a mixture of basic resin and various pigments, fillers and additives. The degree of dispersion of pigments, fillers and additives in the resin is crucial to the performance of plastic products. Dispersant is an additive that promotes the uniform dispersion of various auxiliary materials in resin. It is mostly used in masterbatch, colored products and highly filled products. Including hydrocarbons ( paraffin oil, polyethylene wax, oxidized polyethylene wax, etc.), fatty acid soaps, fatty esters and fatty amides, etc.

Cross-linking agent

There is not much difference in nature between the cross-linking of plastics and the vulcanization of rubber, but they are not exactly the same in the use of cross-linking aids. There are two main cross-linking methods for resin: radiation cross-linking and chemical cross-linking. Organic peroxide is the most widely used cross-linking agent in industry. Sometimes in order to increase the cross-linking degree and cross-linking speed, it is often necessary to use some co-crosslinking agents and cross-linking accelerators. The co-crosslinking agent is used to inhibit the possible free radical cleavage reaction of the organic peroxide cross-linking agent on the polymer resin main chain during the cross-linking process, improve the cross-linking effect, and improve the performance of the cross-linked products. Its function is to stabilize Polymer radicals. The main function of cross-linking accelerator is to speed up the cross-linking speed and shorten the cross-linking time. Curing agents for thermosetting plastics such as unsaturated polyester and epoxy resin also belong to the category of cross-linking agents. Common types include organic amines and organic acid anhydride compounds. In addition, the photosensitizer used in the ultraviolet radiation cross-linking process can also be regarded as a cross-linking aid.

Foaming agent

The additive used in the polymer compounding system to obtain polymer products with microporous structure by releasing gas and reducing the apparent density of the product is called a foaming agent. According to the different ways of generating gas during the foaming process, foaming agents can be divided into two main types: physical foaming agents and chemical foaming agents. Physical foaming agents generally rely on changes in their own physical state to release gases, which are mostly volatile liquid substances. Chlorofluorocarbons (such as Freon), lower alkanes (such as pentane) and compressed gases are representatives of physical foaming agents. Chemical foaming agents foam based on the gas released by chemical decomposition. According to their different structures, they are divided into inorganic chemical foaming agents and organic chemical foaming agents. Inorganic foaming agents are mainly heat-sensitive carbonates (such as sodium carbonate, ammonium bicarbonate, etc.), nitrites, and boron hydride compounds, which are characterized by endothermic foaming processes. Foaming agent. Organic foaming agents have a very prominent position in the plastic foaming agent market. Representative varieties include azo compounds, N -nitroso compounds and sulfonyl hydrazide compounds. The foaming process of organic foaming agents is often accompanied by exothermic reactions, and they are also known as exothermic foaming agents. In addition, some additives that can adjust the decomposition temperature of the foaming agent, that is, foaming aids, are also included in the foaming agent category.

Antifungal agent

Antifungal agents, also known as microbial inhibitors, are a type of stabilizing agent that inhibits the growth of microorganisms such as mold and prevents polymer resins from being eroded and degraded by microorganisms. Most polymer materials are not sensitive to mold, but they are susceptible to mold due to the addition of plasticizers, lubricants, fatty acid soaps and other substances that can breed mold during processing. Antifungal agents for plastics contain many chemicals. The more common varieties include organic metal compounds (such as organic mercury, organic tin, organic copper, organic arsenic, etc.), nitrogen-containing organic compounds, sulfur-containing organic compounds, and halogen-containing organic compounds. and phenolic derivatives, etc.

Anti-gnaw agent

Anti-bite agents are also called anti-rat bite agents. They can cause the oral mucosa and taste nerves of rodents to be strongly stimulated and avoid chewing and destroying them. It has significant effects on rats, wild animals, birds, cats and dogs and other pets. The bite prevention effect. Especially suitable for agricultural films and pipes, it can replace stainless steel armored shells and greatly reduce production costs.

Product introduction

PVC processing aid is acrylate copolymer (ACR).

The basic function of PVC processing aids is to improve the processing performance of PVC and promote the plasticization of PVC mixtures, so as to obtain well-plasticized materials at the lowest possible temperature and improve the quality of products. We have developed the following five types of processing aids according to the needs of different products.

1. Universal type: promotes the plasticization of materials.

2. Lubricating type: In addition to promoting the plasticization of materials, it also has the function of metal peeling, preventing the adhesion between the melt and the metal surface, and prolonging the driving cycle.

3. Bright type: In addition to promoting the plasticization of materials, it can significantly improve the surface brightness of products, and is suitable for products that require higher surface finish.

4. Super plasticizing type: The ability to promote the plasticization of materials is higher than other types. It is suitable for material formulations that are difficult to plasticize, such as those with high calcium carbonate components, large amounts of lubricants, or the addition of carbon black, fiber and other modifiers. formula.

5. Super melt strength type: In addition to promoting the plasticization of materials, it can also greatly increase the melt strength of materials, improve the stability of production, extend the production cycle, and improve the mechanical properties of products, especially suitable for calcium carbonate. Products with high content (greater than wt30%).

Promote plasticization mechanism

No matter which PVC processing form is used, the PVC mixture must be plasticized evenly. Only materials that are uniformly and well plasticized can have good appearance and mechanical properties.

However, compared with other general plastics, unplasticized PVC can only be plasticized under higher temperature and shear conditions. However, PVC is easy to decompose at high temperatures. In order to ensure uniform plasticization and improve the quality of hard PVC products, it should be Plasticize the material at the lowest possible processing temperature and as high shear force as possible. Generally speaking, PVC processing aids must have the following characteristics to have the function of promoting plasticization.

1. The melting temperature is lower than PVC and melts before PVC during processing.

2. Because it has good compatibility with PVC, it can adhere to PVC particles after melting during processing, increase internal friction, increase shear torque, generate internal heat, make the temperature distribution in the material uniform, and the degree of plasticization is uniform, thus Promotes the uniform plasticization of PVC materials.

3. The processing aid has a large enough molecular weight, which increases the melt viscosity (or strength) and melt pressure during the processing, prevents the material from slipping, thereby increasing the shearing torque and making the melt and metal surface The friction heat increases significantly, which promotes the mixing uniformity and plasticization degree of the PVC mixture.

How to use

The essence of processing aid ACR is a solid plasticizer. If the melting point and molecular weight of ACR decrease further, it will eventually become a plasticizer. In the study, it was found that processing aids (including plasticizers) with low melting points have fast plasticization speed and good melt fluidity, but have low melt viscosity, melt strength, and melt pressure; processing aids with high melting points The plasticizing speed is slower and the melt fluidity is poor, but the melt viscosity is high, the melt pressure is high, the melt strength is high, and the later plasticizing ability is strong. The former reduces the mechanical properties and weather resistance of PVC materials, but the latter hardly affects the mechanical properties of PVC materials and improves its weather resistance.

A certain type of processing ACR with good plasticizing effect will greatly increase the current and torque of the extruder for one PVC formula, and increase the degree of plasticization of PVC, but for another PVC formula, it may cause the PVC products to The color becomes darker and chromatic aberration occurs. Sometimes a processing type ACR that is suitable in a fast extruder may not be suitable in a slow extruder, and vice versa. Therefore, it is almost impossible to make a processing type ACR meet the requirements of different formulas, different products, and different processing equipment. Similarly, it is impossible for the traditional processing aid ACR to meet the processing technology requirements of fast plasticization, high melt strength and high melt pressure. In order to meet the individual requirements of our customers, we have developed a series of new processing aids with different plasticizing properties and other characteristics to adapt to the needs of users. The performance of some of these products can completely replace some imported products. Products, we have conducted detailed research on the performance and usage methods of these processing aids. As long as customers put forward their specific requirements, the company’s New Materials Research Center can recommend applicable product models, dosages and usage methods to you.

Applied technology

Nucleating agent

Nucleating agent is a functional additive used to change the crystallization behavior of polypropylene, thereby changing its crystal morphology, mechanical properties, thermodynamic properties and optical properties.

1. Polypropylene nucleating agent HBP

Polypropylene modified by adding nucleating agents has the characteristics of good transparency, high gloss, excellent mechanical properties and processing properties, and its use range is also relatively wide.

2. Polyformaldehyde nucleating agent

Polyoxymethylene (POM) is a highly crystalline engineering plastic with excellent comprehensive properties. It has high strength and hardness, good rigidity, and good wear resistance and fatigue resistance. Therefore, it is used to replace non-ferrous metals and alloys and is widely used in automobiles, electronic appliances, construction, machinery and other industries. Due to the high crystallinity of polyformaldehyde (generally more than 60% crystallinity), there are gaps in the product, low impact strength, and large molding shrinkage, which do not match various other excellent properties and require further improvement. There are two main ways to improve the performance of polyoxymethylene materials: strictly controlling processing conditions and adding nucleating agents. Studies have found that the impact strength of crystalline polymers is related to the size and distribution of spherulites. The experiment mainly involves adding a nucleating agent to polyformaldehyde to change the morphology of polyformaldehyde spherulites, reduce its crystal size and shrinkage during the molding process, improve its impact resistance, and optimize the performance of polyformaldehyde so that it can meet some requirements. Special requests.

Antioxidants

During the manufacturing, processing, storage and use of PP, PE, PS and other plastics, oxidative degradation often occurs due to the effects of light, oxygen, heat and other factors, causing plastic deterioration, causing the plastic to lose weather resistance and durability, affecting the plastic’s durability. Strength and appearance. In order to extend the life of polymer materials and inhibit or delay the oxidative degradation of polymers, antioxidants are usually used.

1. Main antioxidant

Primary antioxidants, also known as free radical scavengers, are the type of antioxidants that play a major role. It can capture oxygen, thereby stopping or slowing down the thermal oxidative aging of polymers.

2. Auxiliary antioxidant

Auxiliary antioxidants are also called hydroperoxide decomposers. It is a type of additive that can decompose polymer hydroperoxides generated during thermal oxidative aging chain reactions to generate inactive compounds, thereby terminating or slowing down thermal oxidative aging. Because it often has a synergistic effect with the main antioxidant and can only exert its maximum effect when used together with the main antioxidant, it is commonly known as the auxiliary antioxidant.

3. Carbon radical scavenger

Carbon free radicals (i.e. alkyl free radicals) are usually generated in the chain reaction of thermal oxidative aging in the absence of oxygen and high temperature.

Plasticizer

Plasticizers are the largest variety of additives in the modern plastics industry and play a decisive role in promoting the development of the plastics industry, especially the polyvinyl chloride industry. Anything that can be mixed with resin will not undergo chemical changes during mixing, but it can reduce the glass transition temperature of the material and the melt viscosity during plastic molding processing, and itself remains unchanged, or it can remain in plastic products for a long time despite chemical changes. Liquid organic compounds or low melting point solids that have these properties and can change some physical properties of the resin are called plasticizers.

Polyester plasticizers are produced through the condensation reaction of dibasic acids and diols. The main types include adipic acid polyester and phthalic anhydride polyester. The biggest difference between polyester plasticizers and commonly used plasticizers is their larger molecular weight. The molecular weight of polyester plasticizer can be comparable to that of PVC, so it has better compatibility with PVC. Moreover, due to its low volatility, resistance to oil and extraction of aliphatic or aromatic hydrocarbons, resistance to migration in paints and rubbers, and excellent aging resistance, polyester plasticizers have Its superior properties such as resistance to extraction, high temperature resistance and low migration make it known as a “permanent plasticizer” and is a type of plasticizer that is developing rapidly.

Heat Stabilizer

1. Thermal stabilization mechanism of rare earth thermal stabilizers

Rare earth elements have numerous orbits that can serve as central ions to accept lone pairs of electrons from ligands. At the same time, rare earth metal ions have large ionic radii and form ionic bonds with inorganic or organic ligands mainly through electrostatic attraction. The HCL reaction released when PVC degrades has a strong catalytic effect. It is generally believed that it is an ionic mechanism catalytic reaction, with [CLHCL] – or [CL] – ions participating in the reaction process, and [CLHCL] – or [CL] – ions. It can be used as a ligand to provide lone pairs of electrons. According to the “soft and hard acid-base principle” proposed by Pearson, hard alkali chloride ions and rare earth metal ions can easily form stable complexes. Therefore, the rare earth atoms have a strong coordination and complexing ability with the chlorine atoms on the PVC chain. [CLHCL] – and [CL] – do not participate in the catalytic de-HCL reaction, so they play a certain stabilizing effect on PVC..

2. Antioxidant F has thermal stabilizing effect on polyformaldehyde

Polyoxymethylene (POM), as an engineering plastic with excellent comprehensive properties, is widely used. However, due to its special molecular structure, POM has poor thermal stability. During its melting process, it is easy to undergo chain scission under the action of heat and oxygen, undergo thermal degradation according to free radical decomposition, and then undergo continuous formaldehyde removal reactions. Antioxidants are usually added to capture free radicals generated by the system, interrupt the auto-oxidation cycle of the entire system, and play an antioxidant stabilizing role. Phenolic antioxidants with brands Irganox259 and Irganox245 from Swiss Ciba Company are commonly used in POM production and applications, which can greatly improve the thermal stability of POM.

The experimenters selected the high relative molecular mass hindered phenolic antioxidant F as the POM antioxidant. In addition to providing efficient thermal stabilization, it can also reduce the amount of antioxidants and reduce the cost of POM production.

(1) The test results using thermal weight loss rate, thermal weight loss rate, and balance torque analysis show that when the dosage of antioxidant F is 0.3~0.4, it can achieve a thermal stabilization effect on POM that is equivalent to or even better than 0.5% Irganox245.

(2) Antioxidant F can effectively inhibit the degradation of POM resin caused by heat, oxygen, and stress during high-temperature processing, effectively extending the long-term thermal and oxygen life of POM products, and using a smaller amount of antioxidant F (0.3%) Thermal and oxygen stabilization efficiency reaches the level of 0.5% Irganox245, which can be promoted and used in POM production to further improve POM thermal stability and reduce production costs.

Regulator

The YM- and YP- series PVC foaming regulators developed by the company are actually acrylate processing aids. They have all the basic characteristics of PVC processing aids. The only difference from PVC general processing aids is the molecular weight. PVC The molecular weight of foaming regulators is much higher than that of general-purpose processing aids.

Foaming regulation mechanism

The purpose of adding ultra-high molecular weight polymers to PVC foam products is: first, to promote the plasticization of PVC; second, to improve the melt strength of PVC foam materials and prevent the merging of bubbles to obtain uniformly foamed products.; The third is to ensure that the melt has good fluidity to obtain products with good appearance. Since different foam product manufacturers have different products and use different equipment, processes, raw materials and lubrication systems, we have developed foaming regulators with different properties to meet the different needs of users.

How to use

1. Principles for selecting foaming regulator:

① PVC with different degrees of polymerization, such as S-700, S-800 and S-1000, have different processing temperatures, melt viscosity and melt fluidity, and appropriate foaming regulators should be selected accordingly.

② The plasticizing speed should be appropriate

③ The melt strength must be sufficient

④ The melt fluidity should be better

⑤ Different products, such as foam boards, foam thick boards, foam thin boards, wood-plastic foam boards, steel-plastic foam boards, etc., require different process conditions, and should be selected according to the basic characteristics of each type of foaming regulator Different models.

⑥ Choose a foaming regulator that can disperse well with the corresponding PVC to ensure the uniformity of the melt and good board quality.

⑦ Choose good internal and external lubricants

⑧ Add enough heat stabilizer

2. Usage and dosage

Based on the above principles, it is possible to determine the most suitable model and dosage only after full communication between the technical personnel of both parties.

New additives

Performance characteristics

PVC processing modifier YMs-series products are a new type of PVC modified processing aid developed by the company by combining advanced polymer synthesis technology with nanotechnology from the Chemical Engineering Research Laboratory of the Department of Engineering of Tsinghua University. It makes full use of It has the characteristics of large specific surface area and large surface free energy of nanomaterials, and overcomes the shortcomings of traditional PVC processing aids that have poor plasticizing performance when the temperature decreases. During the processing, the strong surface tension of nanomaterials is converted into internal friction with PVC molecules, because this internal friction increases as the temperature decreases, which improves the plasticizing performance of traditional ACR as the temperature decreases. And the problem has become significantly worse.

Compared with traditional ACR, HLn-series products have the following characteristics:

(1) Static stability is better than traditional processing aids.

(2) When the temperature changes, the shear force changes accordingly, which can keep the plasticization degree of PVC basically unchanged.

(3) It can greatly improve the processing performance of PVC and improve the surface finish of products.

Quality standards

Inspection method:

(1) Visual inspection of appearance

(2) Volatilization is measured according to GB/T2914

(3) Particle size is measured according to GB/2916

(4) The processing performance is measured with RM-200 torque rheometer, the rotation speed is 35rpm, the temperature is 165℃, and the feeding amount is 61g;

Performance evaluation formula: PVC, 100g; CaCO3, 5g; TiO2, 4g; PE, 0.15g; stearic acid, 0.2g; disalt, 2.5g; hard lead, 1.5g; hard calcium, 0.7g; CPE, 9g; Processing aid, 2g.

Processing performance of processing aids:

The function of PVC processing aids is to increase the friction between the internal molecules of the mixture and the surface friction between the mixture and the screw and barrel, thereby increasing the current and torque of the PVC processing equipment, so that PVC can be plasticized evenly at the lowest possible processing temperature. In order to obtain PVC hard products with the lowest degree of decomposition and the best appearance and mechanical properties. If the processing temperature of PVC is lowered, the residual amount of stabilizer in PVC products will be greater, the amount of balanced HCI will be lower, and the stability or weather resistance of the product will be better! One of the conditions for low-temperature processing is that high shear must be ensured, that is, high current and torque must be ensured. Therefore, the performance of PVC processing aids must be evaluated by torque and current, and the testing equipment that can reflect torque is a torque rheometer. Therefore, the company uses flow instead of viscosity in the quality indicators of HLn-series products. Variometer is used to characterize the processing performance of processing aids. All products are tested with a rheometer before leaving the factory. If the rheological curves overlap, the processing properties of the two batches of products are the same, thus ensuring the stability of customers during production and use.

Things to note

In order to achieve smooth production, first select CaCO3 with moderate particle size and uniform particle size distribution, and then consider the following five points based on the principle of lubrication balance.

1. Insufficient internal and external lubrication: the melt viscosity is large, the plasticizing torque is large, the melt wall sticking phenomenon is serious, there are yellow decomposition lines on the material surface, the surface smoothness is poor, and the mechanical properties of the product are low.

2. Both internal and external lubricants are excessive: the plasticizing torque is small and the melt plasticization is obviously insufficient. Although the smoothness of the product is very good, the pressure point adhesion is poor, which seriously affects the mechanical properties of the product.

3. With less internal lubricant and more external lubricant, the plasticizing time is significantly prolonged, the plasticizing torque is reduced, and the product becomes difficult to form and becomes brittle.

4. There is more internal lubricant and less external lubricant, the plasticizing time is obviously shortened, there is serious wall sticking phenomenon, the thermal stability time is shortened, and there are decomposition yellow lines on the surface of the product.

5. When the CaCO3 particle size is too large, the plasticization time of the mixture is significantly delayed, the screw torque is low and the friction heat generated is too little, and the melt strength is low and the product is difficult to form. In order to increase melt strength and promote plasticization, a certain amount of new JL-M01 polymerization processing modifier is added. The new JL-M01 polymerization processing modifier can increase the melt viscosity and adhesion of the mixture, and improve the conversion of shear force to frictional heat.

Development direction

1. Green plasticizers are ushering in a wave of production expansion

2. Rapid development of demand promotes “green” changes in heat stabilizers

3. Additive products are changing from single products to multi-functional products and composite materials.

4. Processing and impact modifiers gradually replace PP/PE materials