The mandatory national standard GB18581-2001 "Restriction of harmful substances in solvent-borne wood coatings for interior decoration materials" has been implemented since 2002, which has greatly promoted the reduction of harmful substances in solvent-based wood coatings and promoted the technological progress of the coatings industry. , For the National Certification and Accreditation Administration to implement solvent-based wood coating 3C certification and quality supervision departments at all levels to regulate the solvent-based wood coatings market provides a basis for the judgment, to reduce environmental pollution and protect people's health has a very positive significance.
However, since 2001 was the first time to formulate limits for hazardous substances in paints, the time was rushed, and it was also related to the technical level at that time, resulting in the low standard level and some problems in the test methods. With the adjustment of the structure of solvent-based wood coating products, advancement of technology, improvement of product quality, and the increasing demand for health and environmental protection products from market consumption, the existing standards cannot meet the continuous development needs of solvent-based wood coatings. Revised in time, advancing with the times and constantly improving to guide the industry to a higher level. To this end, the National Coatings and Pigments “target=”_blank “> Pigments Standardization Technical Committee applied for the standard revision project to the National Standardization Management Committee, and in 2008 it completed the revision and approval of the standard.
In 2010, the introduction of new standards in the solvent-based wood coatings industry has a bearing on all aspects of the wood coating industry. Whether it is procurement or technology, R&D, production, quality inspection, service, engineering, and distributors, all have to be familiar with the new standards. content. This article reviews the main differences between the new and old standards for solvent-based wood coatings and the specific requirements for harmful substances.
The main differences between the new and old standards The current standards apply to solvent-based wood coatings for interior decoration, including three types of resins, namely polyurethane, nitro and alkyd solvent-based wood coatings, not suitable for waterborne wood coatings. .
The current standard does not clearly stipulate the application of solvent-based wood coatings for industrial coating. However, the CNCA has included “solvent wood coatings for furniture factories for furniture manufacturers” in the 3C certification of solvent-based wood coatings. Certification scope. Therefore, the revised standard expands the scope of application to stipulate “applicable to polyurethane, nitro and alkyd solvent-based wood coatings (including primers and topcoats) for interior decoration and industrial painting and Wood-based solvent-based putty." Based on the three types of resin coatings, a category of solvent-based putty for woodware (without resin type) has been added. Clear application areas include interior decoration and industrial painting. In addition, it is no longer necessary to describe water-based wood coatings. However, it is clearly not applicable to radiation-curing coatings and unsaturated polyester putties.
Terms and Definitions Terms and definitions are not given in current standards. Revised standards give "Volatile Organic Compound (VOC)", "Volatile Organic Compound Content", "Polyurethane Coating", "Nitro-based Coating", and "Alkyd paints" Five terms and definitions. Because there are many definitions of volatile organic compounds (VOCs) in the world, the results of VOC content testing are directly related to the specific test methods. Therefore, it is necessary for the standard to define the definitions of these two terms. Volatile organic compounds (VOCs) are defined as "any organic compound with an initial boiling point of less than or equal to 250°C at a standard atmospheric pressure of 101.3 kPa." The volatile organic compound content is defined as "the content of volatile organic compounds obtained by testing the product according to the specified test method".
Due to the non-standard naming of the paint industry, the quality supervision department and consumers often have the wrong understanding of the product categories covered by the standard, so the revised standard gives the definition of three resin type coatings. It should be noted that the coatings used for the coating of wood products include polyurethane (PU), nitro (NC), alkyd (AK), UV-curable (UV), and polyester (PE). Acid-cured coatings (AC) and water-based coatings.
The paint industry customarily refers to three cans of polyurethane coatings as polyester coatings, according to GB/T 2705-2003 "Classification and naming of coating products" and the definition of polyurethane coatings (in terms of polyisocyanates and active hydrogen containing compounds The reacted poly(urethane)
Ester Resin is a type of coating for the main film-forming substance. Such coatings should be classified in the category of polyurethane coatings. Alkyd coating refers to a type of coating that uses alkyd resin or modified alkyd resin as the main film-forming substance and is dried by oxidation to form a coating. This is a consensus in the coating industry. It is confusing to misclassify acid-cured amino wood paint (one-component or two-component) into alkyd or polyurethane paints. The main film-forming substance of the acid-cured amino wood paint is amino resin and alkyd resin. The acid drier is used to increase the curing rate or lower the curing temperature of the paint. According to GB/T 2705-2003 "Classification and nomenclature of paint products", Should belong to the amino resin type coating.
Specific Requirements for Pests Benzene, Toluene, Ethylbenzene, Xylene, and Methanol Content GB 18581-2001 Standard Test Methods for the sum of benzene and toluene, xylene, and ethylbenzene After several years of actual use, it has been found that there are some areas that need improvement and improvement. The revised standard made the following modifications to the test method:
The chromatographic separation column from packed column to capillary column;
The content of the diluent and each component will be determined separately, and the total amount of the mixed coating will be calculated according to the construction ratio indicated by the product. Instead, the mixed sample shall be prepared according to the construction ratio indicated by the product, and the mixed sample shall be directly tested. The content of
Added methanol test content;
Added provisions for repeatability and reproducibility.
Free diisocyanate (HDI, TDl) content GB18581-2001 standard free ** diisocyanate (TDl) test method used standard GB/T 18446-2001 "gas chromatography determination **** ester prepolymer and coating solution unreacted ** Diisocyanate (TDI) Monomer", which is equivalent to the American Society for Testing and Materials ASTM D3432-1989 "Gas Chromatography Determination of Unreacted ** Diisocyanate in Ester Prepolymers and Coating Solutions ( The national standard formulated by TDI) Monomer is only suitable for the determination of free ** diisocyanate (TDI) monomer content. The revised standard free diisocyanate (HDI, TD1) test adopts the revised standard of GB/T18446-2001. The revised standard was revised and approved in 2008. The revised standard is equivalent to adopting ISO10283:1997. Lacquers for paints and varnishes - Determination of monomeric diisocyanates in polyisocyanate resins". The main technical differences with GB/T18446-2001 are:
The scope of application is wider. The GB/T 18446-2001 standard is only suitable for the determination of free ** diisocyanate (TDI) monomer content. The revised standard is applicable to a variety of diisocyanates (** diisocyanate, hexamethylene diisocyanate, Isophorone diisocyanate, diphenylmethane diisocyanate and other types of diisocyanate) monomer content determination;
The GB/T18446-2001 standard uses a packed column test, and the revised standard uses a capillary column test. The latter has better separation effect than the former.
The GB/T18446-2001 standard uses 1,2,4-trichlorobenzene as an internal standard, and the revised standard uses tetradecane or tritium as an internal standard.
GB/T18446-2001 standard test precision repeatability (the difference between the two results measured by the same operator) is not more than 0.06%, reproducibility (the difference between the results of the same sample measured in different laboratories) is not more than 0.3% .
The precision of the revised standard has been improved, with reproducibility of no more than 0.02% and reproducibility of no more than 0.05%. (Article Source Global Polyurethane Network)
Halogenated Hydrocarbon Content The halogenated hydrocarbon content is a newly added test item for the revised standard. The newly established test method refers to the HJ/T201-2005 appendix for the determination of halogenated hydrocarbons in paints—gas chromatography analysis. The principle is that the sample is directly injected into the gas chromatograph after dilution, and the dichloromethane, dichloroethane, ****, trichloroethane and carbon tetrachloride are completely separated from the other components by the capillary column. It was detected by an electron capture detector and quantified by an internal standard method.
The revised standard for soluble heavy metal content after the revision of soluble heavy metal content directly quoted the test method of the newly published GB18582-2008 "Dangerous Substances in Interior Decoration Materials for Interior Wall Coatings" in Appendix D of soluble heavy metals. This method is a commonly used method at home and abroad. When the GB18582 standard was revised, the original test method was supplemented and improved, mainly including:
Refer to the international standard ISO8124-3:1997 "Toys Safety - Migration of Certain Elements", National Standard GB6675-2003 "National Toy Safety Technical Code" and GB8771 "Maximum Quantity of Soluble Elements in Pencil Coatings" to introduce the elements of soluble heavy metals The analysis of the correction coefficient and the introduction of the analysis and correction coefficient are based on the accuracy of the test method and the numerical coefficients multiplied with the uncorrected test results introduced to compensate for the error of the test result. The purpose is to increase the comparability of the test results and improve the evaluation. Accuracy.
The revised GB18581 standard expands the scope of application on the basis of the original standard, increases the types of control of hazardous substances, and imposes more stringent control requirements for hazardous substances. The overall standard level has reached the international advanced level.
The content of the revised GB18581 standard is a limit value for hazardous substances contained in solvent-based wood coatings for interior use and solvent-based putties for wood use. Its purpose is to reduce pollution to indoor and outdoor environments and to protect people's health. Standard attributes are still mandatory standards.
