PVC low toxicity and heat stabilizers
With the gradual strengthening of environmental awareness, the traditional PVC heat stabilizers such as the powder of lead salt stabilizer, barium, cadmium stabilizer subject to certain restrictions, has accordingly developed a series of low toxicity, non-toxic hot stabilizers, including the clean compound lead salt, the compound calcium, zinc, organic tin, rare earth, organic antimony class, hydrotalcite, etc.. Article mainly reviewed several typical low toxicity, non-toxic, high efficiency, the development status of the composite heat stabilizer, features, stability mechanism and the development direction.
PVC for its excellent flame retardant, insulation, wear-resistant performance to win a broad market, widely used in building materials, light industry, agriculture, packaging, power, utilities and other departments, especially in building plastics, agricultural plastics, plastic packaging materials , household plastics, and other areas plays an important role. 6.492 million tons of PVC resin production in 2005, after the United States, ranking first in the world 2.
As we all know, PVC resin and its products due to their own structural defects, the existence of easy thermal degradation and aging of the shortcomings of its processing temperature (above 160 "C) than the decomposition temperature (120-130 ~ C) is also high, so to PVC turned into products, it is necessary to add heat stabilizers in PVC processing process, in order to delay or prevent the thermal degradation of PVC resin lead salt is the earliest use of heat stabilizer, a strong stabilizing effect, and low prices, but in the production cause some environmental pollution and use of 2000, Norway, Finland, Sweden, Denmark and the United Kingdom and other European countries have adopted the action of the lead salt stabilizer is disabled since 2003, China is also concerned about lead salts, Beijing and Shanghai have adopted the decision to ban lead in water distribution. used in the nationwide water supply pipes, PVC-U pipe must be non-lead salt stabilizers in PVC plastic products in China comprehensive clear that the announcement of the Ministry of Construction in 2004 prelude has been opened to ban lead, PVC plastic heat stabilizer is moving low toxicity, non-toxic, pollution-free, composite, and efficient direction. This article reviewed the development of type heat stabilizer in polyvinyl chloride and low toxicity.
A clean compound lead salt heat stabilizers
Clean compound lead salt heat stabilizer is that there will be synergies in the heating and mixing conditions lead salt stabilizers, auxiliary heat stabilizer with internal and external lubricant fully dispersed mixture made of granules or flakes of lead salt compound stabilizer [1]. This heat stabilizer (pellets, film material and pre-packaging material) to maintain the lead salt thermal stability and good, to overcome the shortcomings of the toxicity of lead salts dust, very favorable to the occupational health and environmental protection. Wenzhou Tiansheng Group Plastic Additives Plant in 1985, the first PVC cable compound of lead salts on the market, and later developed the 301 and 101 compound lead salt thermal stabilizer. Mr Cheng Tak, etc. [2] in the 1994 Uniform experimental design optimization method, with the help of computer-aided design to obtain a better performance of the modified multi-functional low lead
Dust composite heat stabilizer TS-D, performance testing and structural characterization, the TS-D is both a stabilizer and multi-purpose lubricant modified complexes, with a good processability, PVC thermal stability is better than traditional the lead salt stabilizer, and can reach a favorable environment for low dust operation. At present, China uses more clean compound lead salt heat stabilizer German Bear brand SMS318 type, Henkel, Germany (Henke1) Company STA-B II DX2840 type.
Two composite calcium zinc heat stabilizer
Calcium soap heat stabilizers are long-term heat stabilizers, poor stability, coloring and strong, but non-toxic, has excellent lubricity. The poor stability of the zinc soap stabilizer for PVC heat stabilizers are short-acting, but also prone to the "zinc burning" (mainly produced zncl, the phenomenon of strong Lewis acid, with a catalytic role of the de-HC1), but with the early advantages of the excellent coloring, weathering resistance. Composite calcium zinc heat stabilizer is the use of the two has a synergistic effect, making it the most active areas in recent years, composite stabilizer. The world-renowned manufacturer of heat stabilizers are the product launch. Such as the the the Akcros company AkcrostabCZ series, the OM PlastiStab series, Witco Corporation Mark series and so on. China from 90 years of the 20th century in this area, is now to be a great success. Sun Qiping [3] found by the experimental study of Ca / Zn composite heat stabilizer can not only increase the whiteness of the PVC products can also improve the thermal stability of the product; Xujia You [4] found that through the spectra of pentaerythritol and stearyl the formation of complexes of zinc and zinc chloride, to inhibit the catalytic degradation of zinc chloride PVC, thus inhibiting the zinc burning ", pentaerythritol from the auxiliary stabilizer role of calcium zinc stabilizers: Wenzhou Sheng plastic Additives Co., Ltd. developed CZ a 601-type Ca - Zn composite stabilizer, testing, processing properties, thermal stability, and health indicators are equivalent to similar products imported to China in the field to a new level.
3 Organic tin heat stabilizer
Organotin stabilizers can generally be XnSnY (4-n) (n = 1-3). Among them, the x groups can be alkyl, such as methyl, butyl, octyl ester, such as methyl acrylate, butyl acrylate Y groups can be fatty acids in the root, you can also mercaptan root (thiol ester root). Different alkyl its performance is also different, the thermal stability of the order of methyl> butyl> octyl alkyl phase, while its thermal stability order for the mercaptan tin> maleic acid monoester tin dilaurate.
The mechanism of action of organotin stabilizers in the PVC molecules lively chlorine atoms replaced by groups not easily broken down prolapse. During the reaction, the chlorine atoms with organic tin compounds in PVC molecular chain with coordination complexes, When HC1 exist, prolapse, the chlorine atoms in PVC chain organic tin molecules in the Y group replacement, thus inhibiting the decomposition reaction. Organotin stabilizers advantage of excellent thermal stability, excellent transparency, good compatibility, good liquidity, non-fouling and non-toxic, but the downside is poor lubrication. and the manufacturing cost is relatively expensive.
Organic tin heat stabilizer is the best and most promising development in one of the heat stabilizer of the current of PVC, so its very active, mainly in the research focus of the following aspects.
3.1 to enhance and improve the performance of the original species
The study found that the introduction of epoxy groups in the organotin compounds, can significantly improve the stability effect, even with three alkyl tin and four alkyl tin derivatives have outstanding thermal stability, and other stabilizer compound better use of [6].
3.2 Development of new organotin heat stabilizers
Development of new organotin heat stabilizers, such as the introduction of the benzene ring in the stabilizer molecule.
3-3 to improve the molecular weight of organotin heat stabilizers
Increase the molecular weight of organotin heat stabilizers, and the formation of polymeric organotin heat stabilizers, can avoid the volatilization of the small heat stabilizer, to improve stability [8]. Rong-Bao et al [9] Bis (alkyl carbonyl alkyl) tin dichloride and adipic acid, diol, diol and dithiol interfacial polycondensation reaction, synthesis of a series of organotin polyester, polyether and Polythioether stabilizer. The experimental proof of the stabilizing effect of the order: the organotin Polythioether organic tin polyester organotin polyether.
3-4 the development of new preparation process
TANG Ai-Dong [l0] water phase method synthesis pairs of two (a small oxygen carbamoyl-ethyl) tin (mercaptoacetic acid isooctyl), measured its thermal decomposition temperature of 232 ° C and by theoretical calculations to get the product decomposition reaction The apparent activation energy of 307.53 kJ. mol First, the apparent activation energy of the decomposition reaction of the ester chloride as a raw material (1l 1.24 kJ.mol.) high 196.29 kJ. mol. 1, the thermal stability of the obtained product is better than the ester chloride of tin: through the Hoch et al. [11] in the patent, the bulk polymerization method, synthesized in the presence of benzoyl peroxide (BPO), maleic diethyl tributyltin styrene an acrylic butanol (DBTM-St-BA), terpolymer, better than DBTM copolymer containing the same amount of tin on the thermal stability of effects and processing properties of PVC, can be used as multifunctional of PVC heat stabilizers.
3.5 the development of odor-free organic tin products
Environmental plasticizer is the focus and direction of plastic additives in the development of the new century, the development of organic tin stabilizer is also increasing emphasis on environmental protection, and if improvement in the technical synthesis, try to avoid the trimethyl tin compounds to generate toxic, or eliminate tin products is not the smell.
, But with the world advanced level, there are still many gaps and a wide gap between production and development of heat stabilizers in China achieved considerable results. First, a few varieties, the structure is irrational; the small scale of production, poor product quality.
4 rare earth heat stabilizer
The rare earth thermal stability mechanism is determined by their electronic structure. Rare earth ions according to the theory of quantum mechanics, many of 4f and 5d empty electronic energy levels (electron orbit), they can accept 6 ~ 12 ligands the lone electron pair as a coordination center ion, at the same time they have larger ionic radii , are likely to form the 6-12 bond energies ranging from complexing key. These characteristics make the rare-earth heat stabilizer addition to the formation of ionic bonds with 3-4 HC1 molecules, may also absorbed a number of HC1 molecules to form a bond energy ranging from complex, effectively reduced as the heat
Degradation of the catalyst concentration of HC1, thus effectively reducing the HCI Photocatalytic Degradation of speed demons, while rare earth ion complexation with the unstable chlorine atoms in PVC chain, inhibition of PVC drop relief HC1 reaction.
The advantages of rare-earth heat stabilizer is good thermal stability, in particular the excellent long-term stability, high transparency, non-toxic, odorless, dispersion, resistant to precipitation, the plasticizing effect, and light stability; The main drawback is with the initial coloring. In 1971, Japan's Takata Yukito [l3] was first to the field of study, and reported that stearic acid lanthanum, cerium and other rare earth organic weak acid salt products of PVC thermal stability of, and that they have low toxicity, good lubricity, high transparency, good light stability and other significant advantages. France, Louis, etc. [14,15] followed by in-depth study of rare earth heat stabilizer, has opened up a new field of PVC heat stabilizers. However, due to the poor of these countries, rare earth resources, subject to considerable restrictions in the field of research and application. China in the early 1980s began to get involved in research in the field, Baotou Institute of Plastic, first developed a solid rare-earth heat stabilizer. Although China started late in the field, made in the field of rare earth rich in natural resources, remarkable achievements have been studied for several systems.
4.1 stearic acid rare earth
Similar to calcium stearate stearic acid in the thermal stability of rare earth, with the characteristics of long-term heat stabilizers, in addition to the rare earth stearate is a way to both lubrication, processing aids, as well as the role of non-toxic transparent wide stabilizer long-term heat stabilizers for PVC. YANG Zhan red [l6] Monostearate synthesis method of the rare earths and rare earth stearate and found that stearic acid rare earth alkaline treatment, not only to improve the products of the rare earth content, can also extend the applications of rare earth .
4.2 maleic acid monoester of rare earth
Similar to the maleic acid monoester of rare earth and stearic acid rare earth, the specimen will produce coloring in the hot early aging, but the role of characteristics of the long-term heat stabilizers, and has a strong ability to inhibit PVC coloring. Wu Maoying [17] study the characteristics of the maleic acid monoester of rare earth, and found that the thermal stability and transparency of the maleic acid monoester rare earth better than stearic acid rare earth pressure analysis and blooming effects are low.
4.3 Epoxy Fatty Acid
Epoxy fatty acid rare earth than stearic rare earth has a better long-term thermal stability, Epoxy Fatty Acid molecules containing epoxy and epoxy compounds auxiliary heat stabilizer, has a stabilizing effect of the auxiliary heat. Wu Maoying [18] by the new technology of the rare earth epoxidized soybean oil synthesis of epoxy fatty acids, epoxidized soybean oil in an aqueous solution in ethanol and NaOH saponification reaction, and then epoxy sodium soap solution generated chloride and The rare earth solution for the metathesis reaction can be synthesized high-purity epoxy epoxy retained intact Fatty Acid.
4.4 carboxylic acid ester of rare earth
Carboxylic esters of rare earth with the polarity of the ester group and a longer alkyl, good compatibility with PVC, and therefore a better thermal stability performance of the play. Liu Yue Jian et al. [19] and compare the carboxylic acid ester of rare earth elements and organic tin photoaging stabilizing effect on PVC, found that carboxylic esters rare earth anti-de-HC1 better than organic tin, antioxidant capacity than the organic tin compound of two stabilizer a synergistic effect.
4.5 salicylic acid rare earth
Salicylic acid rare earth usually refers to the alkali metal or alkaline earth metal salts of salicylic acid rare earth. Liu Ye [20] was prepared by the reaction of rare earth nitrate with salicylic acid sodium salt of rare earth salicylate, thermal stability tests showed that the salicylic acid rare earth stabilizing effect than the commonly used metal soap stabilizers for PVC. Lead stearate and cadmium stearate.
4.6 composite rare earth heat stabilizer
Rare earth heat stabilizer in general with the shortcomings of the initial coloring, generally can not be used alone, but has good synergy with other heat stabilizer or auxiliary heat stabilizer can be complex preparation of compound heat stabilizers. Such as Wu Maoying [21] developed based on stearic acid stearic acid rare earth rare earth. Composite heat stabilizer of a mercaptan of zinc stearate, octyl tin RHS 2 is a highly effective non-toxic transparent PVC heat stabilizers used in place of Ba / Cd class of toxic heat stabilizer in the production of soft transparent PVC products, both can improve product quality, reduce product costs, and expand the products range of applications.
China's rare earth resources in the country (80% share of world total storage), the output of superpower, but also due to the enrichment of ore type of the reasons for easier, lower cost of smelting, these factors are China's development of rare-earth heat stabilizer highly favorable conditions. Comply with the worldwide increasingly stringent environmental protection requirements for the situation, low lead, low toxicity and rare-earth heat stabilizer has a very important economic and social significance.
Organic antimony heat stabilizers
Organic antimony heat stabilizers generally refers to trivalent antimony mercaptide, the product of foreign industrial production in the late 1970s, the United States 1988 60% of the PVC pipes in the organic antimony heat stabilizers. 1986 Beijing aids developed by the Institute of trivalent antimony mercaptide 1990s, Central South University of Technology and other units have been put into the organic antimony heat stabilizer. Heat stabilizer of organic antimony resistance early coloring and excellent thermal stability than organic tin heat stabilizer in low volume, but also has the versatility and enhance and improve the physical properties and machining performance advantages [22].
Organic antimony heat stabilizers in PVC stabilization mechanisms in addition to resistance to de-HC1, but also by esterification reaction so that the molecules in the carboxyl or thiol with the PVC molecules in unstable chlorine atoms, or addition to the instability of carbon atoms in the PVC molecules, or addition to the unstable molecular structure of PVC thermal decomposition. In recent years, Liu et al [23] were synthesized (stearic acid mercapto ethyl) antimony, antimony five (mercaptoacetic acid isooctyl), carboxylic acid thiol ethyl antimony, and studied the thermal stability of PVC role to obtain satisfactory results. Liu Jianping et al. [24] synthesis of a sulfur-containing organic antimony stabilizer, with good early color, light transmission and processing, and long storage period, the efficiency of thermal stability and early, long-term stability than liquid calcium / zinc compound stabilizer.
6 hydrotalcite heat stabilizers
Typical hydrotalcite-like compounds Mg6 AI (OH) 16C03.4H2O the first in 1842 by Circa, Sweden, found that its structure is very similar to brucite Mg (OH) 2, by MgO6 octahedra share edges to form a cell layer located in the layer on Mg2 + can be within a certain range of isomorphous replace, making of Mg2 +, Al3 +, OH 'layer with a positive charge, the interlayer exchangeable anion CO3 2 - and the layer of positive charge balance, making this structure was in power [25].
Hydrotalcite heat stabilizer on the thermal stability of PVC from the reaction of the the hydrotalcite PVC degradation process of HC1. Hydrotalcite with HC1 reaction in two steps: First, HC1, and the interlayer anion reaction, Cl - into the interlayer to achieve the purpose of absorption of HC1: Then, hydrotalcite reaction with HC1, the pillared structure was completely destroyed the formation of metal chloride, absorbed HC1.
Hydrotalcite-like heat stabilizer first originated in Japan, Kyowa Chemical Company in Japan in the 1980s, the first filled with hydrotalcite used as a heat stabilizer [26] to the PVC, Adeka at Argus company followed. Their research shows that hydrotalcite and p. Dione and other metal salts, can be given to the PVC and better electrical properties and thermal stability [27]. Due to its non-toxic, inexpensive, and also has good lubricity and flame resistance [28], has been U.S. FDA approved, JI-I A and European countries also recognized their safety.
China is now the the Hydrotalcite heat stabilizers and other heat stabilizers or additives complex research and development, and achieved good results. Zhang Qiang, et al. [29] studied the influence of different surface modification of hydrotalcite PVC heat stabilizers, the results show that the thermal stability of titanate modified hydrotalcite best results; study has also found the hydrotalcite and the organotin compound use effect of the thermal stability of PVC was significantly better than the effect of the use of lead salt stabilizer compound. Liu Xin [30] prepared by roasting recovery of a new type of PVC heat stabilizers - dodecylbenzene sulfonic acid Pillared Hydrotalcite and hydrotalcite complex dubbed Rare Earth Zn heat stabilizers, by The stabilizer structure and performance characterization, the results show that: dodecylbenzene sulfonic acid Pillared Hydrotalcite-like compound
The beginning of the heat stabilizer with good thermal stability, and Japanese production of rare earth compound stabilizer, long-term thermal stability than domestic rare earth compound stabilizer.
7 Conclusion and outlook
A good heat stabilizer, not only should have good thermal stability of static, but also excellent dynamic stability: not only have excellent initial stability, but also have excellent long-term stability; not only to withstand processing of high-temperature test, but also stand the test of time in the application of plastic products. Few products to meet all these requirements. Therefore, in future research, to ensure low toxicity, the basis of non-toxic, not only to focus on the development of new products of PVC heat stabilizers, should take full advantage of the synergies between the existing stabilizer compound, weaknesses development of efficient compound heat stabilizers.
| Updated:2012.02.03 Source: Clicks:2123
