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The safety of melamine tableware - unqualified melamine tableware.




The safety of melamine tableware - unqualified melamine tableware.

In view of the current uneven quality of melamine tableware on the market in China, the public's doubts about the melamine tableware and the consumer's doubts about the melamine tableware

In view of the current uneven quality of melamine tableware on the market in China, the public's doubts about the melamine tableware and the consumer's doubts about the melamine tableware, this article from the introduction of melamine tableware, potential safety hazards of unqualified products and how The correct use of melamine tableware and other aspects has been systematically explained to help consumers find confidence in melamine tableware.


Key words: melamine tableware (melamine tableware), melamine formaldehyde resin, urea formaldehyde resin (urea resin), safety of use.


1 Background introduction:


Currently, tableware on the market is generally divided into three types of materials: ceramics, melamine and stainless steel. The safety, color, luster and artistic temperament of ceramic tableware are very attractive, but they are brittle and the price is high, which makes people prefer the melamine tableware (imitation porcelain) which is similar to ceramics, cheap and durable. tableware). However, with the widespread use of melamine tableware and a large demand, there are also many inferior melamine tableware mixed into the market, which brings potential harm to the health of consumers, especially children. A report in the "Beijing News" on November 11, 2008, "The release of melamine from inferior melamine tableware" has aroused the attention of the mass media and the masses on melamine tableware. The major media in China, including CCTV, reported on the issue of unqualified melamine tableware. The AQSIQ also carried out further market research on melamine tableware. While consumers are objectively aware of the problems in the current market, they also lose confidence in the melamine tableware itself, and even the qualified melamine tableware is discouraged. In fact, the use of melamine as a raw material for tableware has been used for more than 50 years and is widely used all over the world. Now it has been suspected that the majority of people are still unqualified products.


2 Conceptual review of melamine tableware


2.1 Definition of melamine tableware


The melamine plastic tableware is a tableware prepared by compression molding using melamine formaldehyde resin as a base material and melamine molding powder with σ-cellulose as a filler as raw material [1]. Such tableware is widely used in the fast food industry, staff canteens and children for its smooth surface, light weight, beautiful appearance, low temperature resistance (can be directly placed in the refrigerator), retort cooking (boiling water boiling), pollution resistance, and not easy to break. The catering industry and other fields.


2.2 Discussion on the safety of melamine tableware


After the dairy pollution incident in 2008, melamine became not only a familiar term for ordinary people, but also a target for people to respect. But what kind of substance is melamine? What do people think when they learn that the main raw material of melamine tableware that they often use in their daily life is melamine formaldehyde resin?


Melamine-Formaldehyde Resin (MF) is prepared by polymerization of melamine and formaldehyde under neutral or weak alkaline conditions, also known as melamine formaldehyde resin, or melamine resin. It has excellent water resistance, heat resistance, arc resistance and flame retardancy. It is the main raw material of melamine plastic tableware [1].


Melamine and formaldehyde form melamine formaldehyde resin reaction formula:


Since the reaction of melamine with formaldehyde to form melamine formaldehyde resin is irreversible, although melamine and formaldehyde are considered to be slightly toxic and highly toxic, respectively, the product after polymerization, melamine formaldehyde resin (melamine resin) Not toxic. The "Synthetic Resin and Plastic Handbook" states that its physicochemical properties are: "No odor, tasteless, non-toxic, bright color, better heat resistance, hot water resistance and electrical properties than urea-formaldehyde plastics... Thermal deformation temperature up to 180oC, continuous use temperature is above 100 °C [2]." "Chemical and Chemical Dictionary" pointed out: "The thermal deformation temperature of melamine formaldehyde molding powder is 140~155 °C [3]." According to the Food Safety of the Government of the Hong Kong Special Administrative Region Dr. Deng Shaoping of the Center---Risk Assessment Team pointed out in the report "Imitation of Porcelain Tableware and Food Safety": "Imitated porcelain tableware can be safely contained in food as long as it is used according to the manufacturer's designated use. Most manufacturers list tableware. Applicable to -30 ° C to 120 ° C, while some indicate up to 140 ° C [4]. " According to the head of the large formal melamine tableware company in China, the melamine formaldehyde resin after curing is colorless and transparent. Stable in boiling water, even at 150 ° C. In summary, qualified melamine tableware products should be safe and harmless as long as they are used under the manufacturer's instructions.


3 Discussion on the problems of unqualified melamine tableware


Since the melamine tableware was put into production in China in the 1960s, with the increasing demand of the market, it has also brought an opportunity for the counterfeit melamine tableware. The counterfeit melamine tableware currently on the market is mainly divided into two categories:


(1) Inferior melamine tableware made of melamine resin but not properly controlled in production and cut corners;


(2) Counterfeit melamine tableware mixed with urea-formaldehyde resin or completely substituted with urea-formaldehyde resin


3.1 Unqualified melamine tableware


The “Production Permit for Food Packaging Containers and Tools” prepared by the Food Production Supervision Department of the General Administration of Quality Supervision, Inspection and Quarantine [5] states that the process links in the production process are essential for the qualification of melamine tableware. The role.


(1) Raw material ratio:


If the resin content in the raw material is not enough, or the degree of ball milling of the raw material is not enough, the raw materials are rough, and the amount of raw materials added is insufficient, the structure of the tableware produced will be loose or have obvious defects, so that soy sauce and vinegar in daily life are easily infiltrated. Not easy to remove. The book also pointed out: If the formula is not easy to cause the formaldehyde content to exceed the standard, it can not meet the safety and health requirements.


(2) Mold finish and exhaust control:


In the press molding process of melamine tableware, in order to eliminate small molecules such as formaldehyde and water generated during the crosslinking reaction of melamine-formaldehyde resin, there must be an exhaust process. If the exhaust is improper, it will not only affect the discharge of formaldehyde molecules, but also generate pores on the surface of the tableware, so that the stains will deposit and affect the food hygiene of the tableware.


(3) pressing temperature, pressure and curing time:


If the pressure, temperature is not proper or the curing time is insufficient, it may contain more melamine and formaldehyde residues, which seriously affects the safety and quality of the tableware.


(4) Surface printing ink quality control:


Since the printed ink in the tableware can be directly in contact with the food, it is important to select inks that meet hygiene and safety standards.


3.1.1 Potential hazards of formaldehyde exceeding the standard


"Formaldehyde is a colorless, irritating and suffocating gas [3]." "Chemical and Chemical Dictionary"


The Hazardous Chemical Safety Technology Book describes the health hazards of formaldehyde as follows: "Strong irritant to mucous membranes, upper respiratory tract, eyes and skin... Chronic effects: Long-term exposure to formaldehyde may be mild, eye, nose, Symptoms of pharynx and laryngeal irritation, dry skin, chapped, softened nails, etc. Formaldehyde is carcinogenic to humans [3]. "If free formaldehyde in unqualified tableware exceeds the standard, formaldehyde may migrate into food or release in the air, especially It is easier to free the formaldehyde during the heating process. Long-term use of tableware with excessive formaldehyde will have potential carcinogenic hazards to the human body.


3.1.2 Potential hazards of melamine exceeding the standard


Melamine (English name Melamine) referred to as triamine, also known as melamine, is a low-toxic chemical raw material [3]. The International Chemical Safety Manual, Volume III, and the International Chemical Safety Card, co-edited by the International Chemical Safety Programme and the European Commission in 1994, indicate that long-term or repeated high intakes of melamine may have an effect on the kidneys and bladder, resulting in stone. Long-term intake of melamine in animals can cause damage to the reproductive and urinary systems, bladder and kidney stones, and can further induce bladder cancer [7].


Since melamine is not a highly toxic substance that causes acute poisoning, the chemical term melamine has been silent for a long time. Until the "milk powder incident" in 2008, melamine became famous overnight. In order to strengthen the safety and hygiene supervision of melamine tableware, the newly introduced "Sanitary Standard for Melamine-Formaldehyde Moldings for Food Containers and Packaging Materials" (GB 9690-2009) was also added to the newly added melamine monomer on February 24, 2009. The limit of migration [8].


3.2 Substituting urea-formaldehyde resin for melamine resin


Similarly, considering the relatively expensive price of melamine resin, some unscrupulous companies are not only cutting corners, but also using urea-formaldehyde resins that cannot be used in food packaging products to produce melamine tableware. (Note: There are no urea-formaldehyde resins in the 959 additives in the Hygienic Standard for the Use of Additives for Food Containers and Packaging Materials [11]. For substances not listed in the standard, they cannot be used in food containers and packaging materials. The tableware made of urea-formaldehyde resin may be mixed into the market on the surface, but it will be inferior in use, and it will release formaldehyde, especially when it is used for cooking. Harm to the health of consumers. For the storage tray with urea-formaldehyde resin as the main raw material and a layer of melamine powder on the outer surface, the safety of use has been quite controversial. However, it can be confirmed that two paragraphs in the "Guide to Production License for Food Packaging Container Tools, etc." published in September 2006 clearly indicate:


"Because of the high price of melamine powder, some manufacturers are pursuing profits, directly replacing the melamine raw materials with urea-formaldehyde molding powder to produce tableware; some use urea-formaldehyde molding as raw material to make tableware, and then Apply a layer of melamine powder to the outer surface of the tableware. The chemical analysis of the tableware made of urea-formaldehyde resin is harmful to the human body during use and needs to be stopped. [5]"


"Because of the high price of melamine, manufacturers should not pursue profits. In the production of melamine tableware, the molding powder of urea-formaldehyde is used instead, and then a layer of melamine powder is applied to the outside of the tableware. This is a practice of stealing the column... ... These tableware made of urea-formaldehyde resin or recycled plastic is undoubtedly harmful to human health. The responsible quality of the company should strengthen the supervision of raw material quality and ensure that the materials used by enterprises meet the requirements of the regulations.[5]"


3.2.1 Urea-formaldehyde resin:


Urea-Formaldehyde Resin (UF) is a polymer obtained by reacting urea with formaldehyde. After curing, it is semi-transparent, resistant to weak acid, weak alkali, good insulation, excellent wear resistance and low price, but it is easy to decompose in the presence of strong acid and alkali, and has poor weatherability [10]. The physicochemical properties of urea-formaldehyde molding powder in the Handbook of Synthetic Resins and Plastics are described as follows: "No odorless, odorless, brightly colored solid with a heat distortion temperature of 130 oC and a long-term use temperature of 80 oC. [2]" Urea reacts with formaldehyde The reaction to form a urea formaldehyde resin is reversible. According to the person in charge of a large-scale qualified melamine tableware production enterprise in China, the larger the amount of formaldehyde, the larger the unreacted part of formaldehyde, that is, the residual formaldehyde, and the higher the free formaldehyde content.


The hazards of formaldehyde have been described in Section 3.1.1. Due to the reversibility of urea and formaldehyde reactions, potential problems with urea release should also be considered. Description of urea in the Handbook of Common Chemical Materials: "Colorless or white crystal, odorless, salty. Heated to 160 °C to decompose to produce ammonia and turn into cyanic acid [9]"; "Chemical and Chemical Dictionary" Description of urea: "Urea, also known as carboxamide, urea. Pure product is colorless, odorless, needle-like or prismatic crystal... melting point 132.7oC, starting to decompose beyond the melting point temperature. [3]" "Food packaging The production permit guide for containers and other products indicates that a tableware made of urea-formaldehyde resin can be smelled with a hot smell of more than 80oC [5]. It can be inferred from this that: Unlike melamine tableware, tableware made of urea-formaldehyde resin cannot be used for cooking or holding higher-temperature foods. However, the urinary taste mentioned in the book requires further analysis by the relevant technical department.


4 Misuse of melamine tableware


Because melamine tableware is resistant to falling, durable, and resistant to cooking, many people use it as a universal tableware. However, melamine tableware is not microwave-heatable, depending on its temperature limitations. When the microwave oven is heated, there is no fixed temperature. It depends on the ability of the heated object to absorb microwaves, so the heating temperature of the microwave oven is uncontrollable. Article 2.2 indicates that the heat distortion temperature of melamine formaldehyde molding powder is 140~155 oC, and the safe use temperature of qualified melamine tableware should not exceed 150 oC, so it cannot be heated by microwave oven. Considering that the unqualified tableware produced with urea-formaldehyde resin can only withstand temperature up to 80 oC, it should avoid high-temperature heating when it is used. In this section, the qualified dense amine tableware and the tableware made of urea-formaldehyde resin are placed in a microwave oven for verification test to observe the phenomenon.


4.1.1 Test equipment and materials: microwave oven, qualified melamine tableware, tableware made of urea-formaldehyde resin


4.1.2 Test method: The samples were placed in a microwave oven and adjusted to high heat (800 watts) for 3 minutes to observe the phenomenon.


4.1.3 Test phenomenon:


(1) Qualified melamine tableware test photo comparison chart


(1) Melamine resin bowl: After 1 and a half minutes of heating, there is a popping sound, and after 2 minutes, the smell can be smelled, but there is no obvious irritation. Partially burnt color, the color change part is peeled (fish scale), and can be peeled off by hand. There is also a large piece of peeling on the back of the bowl and cracking can be seen.


(2) Urea-formaldehyde resin cup: After half a minute, a continuous slight popping sound can be heard. After 1 minute, the sound begins to be noticeable, and then the disgusting smell can be smelled, and the irritation is obvious, the tears in the eyes are unbearable. There is no obvious burnt mark on the cup, but the cup body has been obviously deformed, uneven, and the color is obviously uneven.


At present, there is no research report on the change of melamine tableware in a microwave oven after heating at a high temperature. Because this paper is not experimental, its toxicity and physical changes need further research. For the enhanced control of the safety of melamine tableware, the "Sanitary Standard for Melamine-Formaldehyde Moldings for Food Containers and Packaging Materials" requires that the melamine tableware must be marked with the product material and marked with the words "The use of heating in a microwave oven is strictly prohibited". For those products that are not expressly stated, they will no longer meet the standards after September 1, 2009.


5 Conclusion


The melamine formaldehyde resin is the main raw material, and the qualified tableware produced according to national standards is safe and reliable within the normal scope of its application. At present, the melamine winds on the market are mainly caused by unqualified counterfeit and shoddy products. This paper makes a systematic introduction to the classification, causes and harms of counterfeit and shoddy products. It is hoped that consumers can conceptually understand the existence of unqualified products and the harm to the human body caused by improper use.


At present, melamine plastic tableware is implemented in China.