Addition method of polyformaldehyde tracer and application of tracer

Abstract

The invention belongs to an adding method and application of a polyformaldehyde tracer agent, and the adding method comprises the following steps: dividing a raw material polyformaldehyde into at least two parts, uniformly mixing the tracer agent with one part of the raw material polyformaldehyde to prepare a master batch, and fully mixing the master batch with the rest of the raw material polyformaldehyde or a composition of the rest of the raw material polyformaldehyde and an additive; the fully mixed materials enter a double-screw extruder to be mixed and granulated; the tracer agent is a metal oxide or salt which does not lose efficacy due to reaction or temperature change in the polyformaldehyde production process; the mass ratio of the mixture of the polyformaldehyde and the additive to the tracer agent is 100: (0.003-0.01); the method has the characteristics that the content of the tracer agent is low, the recognition sensitivity is met, the performance of matrix resin is not influenced, the application environment of the material is not influenced, and meanwhile, the method has the advantages of being high in operability, convenient to quickly recognize and high in precision.

Description

Technical Field

[0001] This invention belongs to the field of polyoxymethylene (POM) production technology, specifically a method for adding a POM tracer and the application of the tracer. Background Technology

[0002] Polyoxymethylene (POM), also known as polyacetal or acetal resin, is hailed as "super steel" or "acetal." Its molecule is a high-density, highly crystalline linear polymer without side chains. POM is a high-performance engineering plastic, often referred to as "super steel" or "steel-like" in some countries. POM possesses metal-like hardness, strength, and rigidity, exhibiting excellent self-lubricating properties, good fatigue resistance, and elasticity over a wide range of temperature and humidity. Furthermore, it has good chemical resistance. At a lower cost than many other engineering plastics, POM is replacing metals in some traditionally metal-dominated markets, such as zinc, brass, aluminum, and steel in the manufacture of many components. Since its introduction, POM has been widely used in electronics, machinery, instrumentation, consumer goods, automobiles, building materials, agriculture, and other fields.

[0003] Despite this, the market is flooded with polyoxymethylene (POM) manufacturers, resulting in significant homogenization of product brands. Products from different manufacturers using the same processes are difficult to distinguish, leading to instances of inferior products being passed off as superior ones, disrupting the market and impacting brand building. To address these technical issues, some companies use fluorescent agents for labeling, anti-counterfeiting, and authentication. However, adding fluorescent substances may degrade the material's performance, and the leaching or leakage of fluorescent markers could be harmful to the environment and organisms. Furthermore, some companies choose to add magnesium oxide for labeling, but insufficient amounts fail to achieve the desired effect, while excessive amounts, while increasing the strength of POM and achieving the labeling function, can cause discoloration and reduced toughness, altering the appearance and properties of the POM.

[0004] For the reasons mentioned above, how to provide a way to label polyoxymethylene (POM) without changing its appearance and properties has become a technical problem that enterprises urgently need to solve. Summary of the Invention

[0005] To overcome the above deficiencies, the present invention provides a method for adding polyoxymethylene tracer and the application of the tracer, so as to solve the technical problems existing in the prior art.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A method for adding a polyoxymethylene tracer includes dividing the raw material polyoxymethylene into at least two parts, uniformly mixing the tracer with one part of the raw material polyoxymethylene to form a masterbatch, and thoroughly mixing the masterbatch with the remaining raw material polyoxymethylene or a composition of the remaining raw material polyoxymethylene and additives; the thoroughly mixed material is fed into a twin-screw extruder for mixing and granulation; the tracer is a metal oxide or salt that will not be deactivated due to reaction or temperature change during the production of polyoxymethylene; the mass ratio between the mixture of polyoxymethylene and additives and the tracer is 100:0.003 to 0.01.

[0008] Preferably, the tracer is an oxide or salt of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium.

[0009] Preferably, the additives include lubricants, formaldehyde absorbents, primary antioxidants, and secondary antioxidants.

[0010] Preferably, the lubricant is one or a mixture of several of pentaerythritol stearic acid, polyethylene wax, silicone powder, ethylene bis-stearamide, or stearate; the formaldehyde absorbent is melamine, hydroxymethyl melamine, or melamine-formaldehyde condensate; the primary antioxidant is diethylene glycol ether-di(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylate or pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and the secondary antioxidant is one or a mixture of two of tris[2,4-di-tert-butylphenyl] phosphite and bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate.

[0011] The present invention also provides a method for adding a polyoxymethylene tracer, the method comprising the following steps:

[0012] Step 1: Take the tracer and a portion of polyoxymethylene and mix them in a double cone mixer to prepare a masterbatch. The mass ratio between the portion of polyoxymethylene and the tracer is 10-20: 0.003-0.01.

[0013] Step 2: Divide the remaining polyoxymethylene from Step 1 into two parts, and put one part of the polyoxymethylene and the additives into the masterbatch from Step 1 and mix them evenly to make a premix.

[0014] Step 3: The other part of the polyoxymethylene from Step 2 is added to the above premix and mixed evenly to form a mixture;

[0015] Step 4: Feed the mixture from Step 3 into a twin-screw extruder for granulation via a loss-in-weight feeder;

[0016] Step 5: Place the particulate matter from Step 4 into a drying oven for drying to obtain polyoxymethylene containing tracer.

[0017] Preferably, in step 1, the stirring speed for preparing the masterbatch is 500-1000 rpm and the stirring time is 30-60 min; in step 2, the stirring speed for preparing the premix is ​​500-1000 rpm and the stirring time is 20-40 min; and in step 3, the stirring speed for preparing the mixture is 500-1000 rpm and the stirring time is 15-30 min.

[0018] Preferably, the mass ratio between one part of the polyoxymethylene and the other part of the polyoxymethylene in steps 2 and 3 is 3:4.

[0019] Preferably, in step 4, the controlled temperatures of each zone of the twin-screw extruder are 165℃, 170℃, 175℃, 180℃, 185℃, 185℃, 190℃, 190℃, 190℃, and 190℃, respectively; the die head temperature is 185℃; the main feed rate is 200~500kg / h; the screw speed is 200~500r / min; and the vacuum degree is -0.1~-0.5MPa.

[0020] Preferably, the drying temperature of the drying oven in step 5 is 80-120°C, and the drying time is 2-4 hours.

[0021] The present invention also provides the application of the above-mentioned tracer in polyoxymethylene.

[0022] According to the above scheme, this invention provides a method for adding a polyoxymethylene tracer and its application. In detection, this invention abandons the traditional method of fluorescence irradiation and instead uses spectral analysis to detect metal elements to identify and track polyoxymethylene. Furthermore, in selecting metal elements, this invention uses metal oxides or salts that are highly stable, have good temperature resistance, and will not fail due to reactions or temperature changes during polyoxymethylene production. In practical applications, the metal elements that can be used include oxides and salts of transition metals (d-block in the periodic table), lanthanide metals (rare earth metals, group IIIB of the periodic table), and other stable chemical substances. Oxides, salts, and other stable chemical substances of scandium (Sc), yttrium (Y), and the 15 lanthanide elements (lanthanum La, cerium Ce, praseodymium Pr, neodymium Nd, promethium Pm, samarium Sm, europium Eu, gadolinium Gd, terbium Tb, dysprosium Dy, holmium Ho, erbium Er, thulium Tm, ytterbium Yb, and lutetium Lu) are preferred; oxides, salts, and other stable chemical substances of yttrium Y, lanthanum La, cerium Ce, praseodymium Pr, samarium Sm, gadolinium Gd, terbium Tb, thulium Tm, ytterbium Yb, and lutetium Lu are even more preferred; oxides, salts, and other stable chemical substances of yttrium Y and cerium Ce are even more preferred; the metal elements are detected and identified using spectroscopic analysis. Since the aforementioned metal oxides or salts are used as tracers, the amount used is relatively small. Therefore, Raman spectroscopy can be used for tracking and detection. Raman spectroscopy can accurately detect and identify the characteristic "fingerprint peaks" of metal elements at the ppm level. Quantitative analysis using XRF can further extend the detection range to the ppm level. Furthermore, since the amount of this type of tracer added is at the ppm level, ensuring the tracer is uniformly mixed into the raw materials for subsequent detection becomes a crucial technical problem. To address this problem, this invention employs a stepwise addition method: a masterbatch is prepared by mixing a small amount of polyoxymethylene with the tracer. After the masterbatch is thoroughly mixed, it is then uniformly mixed with other raw materials to achieve the characteristic of uniformly incorporating a small amount of tracer into the raw materials. This method features low tracer content, sufficient identification sensitivity, no impact on the performance of the matrix resin, and no impact on the application environment of the material. It also offers advantages such as high operability, rapid identification, and high accuracy. Detailed Implementation

[0023] This invention relates to a method for adding a polyoxymethylene (POM) tracer and the application of the tracer. The method includes dividing the raw material POM into at least two parts; uniformly mixing the tracer with one part of the POM raw material to form a masterbatch; thoroughly mixing the masterbatch with the remaining POM raw material or a composition of the remaining POM raw material and additives; and then granulating the thoroughly mixed material in a twin-screw extruder. The tracer is a metal oxide or salt that will not become ineffective due to reaction or temperature changes during the POM production process. The mass ratio of the mixture of POM and additives to the tracer is 100:0.003–0.01.

[0025] Furthermore, the tracer is an oxide or salt of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium.

[0026] Furthermore, the additives include lubricants, formaldehyde absorbents, primary antioxidants, and secondary antioxidants.

[0027] Further, the lubricant is one or a mixture of several of pentaerythritol stearic acid, polyethylene wax, silicone powder, ethylene bis-stearamide, or stearate; the formaldehyde absorbent is melamine, hydroxymethyl melamine, or melamine-formaldehyde condensate; the primary antioxidant is diethylene glycol ether-di(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylate or pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]; and the secondary antioxidant is one or a mixture of two of tris[2,4-di-tert-butylphenyl] phosphite and bis(2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphate.

[0028] Furthermore, the adding method includes the following steps:

[0029] Step 1: Take the tracer and a portion of polyoxymethylene and mix them in a double cone mixer to prepare a masterbatch. The mass ratio between the portion of polyoxymethylene and the tracer is 10-20: 0.003-0.01.

[0030] Step 2: Divide the remaining polyoxymethylene from Step 1 into two parts, and put one part of the polyoxymethylene and the additives into the masterbatch from Step 1 and mix them evenly to make a premix.

[0031] Step 3: The other part of the polyoxymethylene from Step 2 is added to the above premix and mixed evenly to form a mixture;

[0032] Step 4: Feed the mixture from Step 3 into a twin-screw extruder for granulation via a loss-in-weight feeder;

[0033] Step 5: Place the particulate matter from Step 4 into a drying oven for drying to obtain polyoxymethylene containing tracer.

[0034] Further, in step 1, the stirring speed for preparing the masterbatch is 500-1000 rpm and the stirring time is 30-60 min; in step 2, the stirring speed for preparing the premix is ​​500-1000 rpm and the stirring time is 20-40 min; in step 3, the stirring speed for preparing the mixture is 500-1000 rpm and the stirring time is 15-30 min.

[0035] Furthermore, in steps 2 and 3, the mass ratio between one part of the polyoxymethylene and the other part of the polyoxymethylene is 3:4.

[0036] Furthermore, in step 4, the controlled temperatures of each zone of the twin-screw extruder are 165℃, 170℃, 175℃, 180℃, 185℃, 185℃, 190℃, 190℃, 190℃, and 190℃, respectively; the die head temperature is 185℃; the main feed rate is 200~500kg / h; the screw speed is 200~500r / min; and the vacuum degree is -0.1~-0.5MPa.

[0037] Furthermore, in step 5, the drying temperature of the drying oven is 80–120°C, and the drying time is 2–4 hours.

[0038] The present invention also provides the application of the above-mentioned tracer in polyoxymethylene.

[0039] The key feature of this invention is that it provides metal oxides or salts that do not become ineffective due to reactions or temperature changes during the production of polyoxymethylene (POM), serving as tracers in POM. Specifically, the tracers may include oxides or salts of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium. These metal oxides or salts are characterized by their small dosage, their ability to maintain the appearance and properties of POM, and the ability to identify and track POM by detecting metal elements. Furthermore, since the tracer is added at the ppm level, Raman spectroscopy can be used to accurately detect the characteristic "fingerprint peaks" of metal elements at the ppm level for identification, while XRF can be used for quantitative analysis. The detection range can reach the ppm level. Furthermore, the amount of the tracer added is relatively small. To ensure accurate time detection, this invention also provides a method for adding this type of tracer, preferably using a three-stage addition method. The core of this addition method is to determine the mixing order based on the amount of raw materials. Specifically, the amount of tracer is the smallest, the amount of additive is slightly larger, and the amount of polyoxymethylene raw material is the largest. Based on this, in actual operation, the tracer is first thoroughly mixed with a small amount of polyoxymethylene raw material to prepare a masterbatch. Then, polyoxymethylene raw material containing additives is added to the masterbatch to ensure thorough mixing. Finally, the remaining polyoxymethylene raw material is added to the aforementioned mixture to achieve uniform mixing of the entire material, thereby ensuring accurate identification of polyoxymethylene by detecting metal elements.

[0040] To explain the present invention in more detail, the invention will now be further described with reference to embodiments. Specific embodiments are as follows:

[0041] Example 1

[0042] A method for adding a polyoxymethylene tracer includes dividing the raw material polyoxymethylene into at least two parts, uniformly mixing the tracer with one part of the raw material polyoxymethylene to prepare a masterbatch, and fully mixing the masterbatch with the remaining raw material polyoxymethylene or a composition of the remaining raw material polyoxymethylene and additives; the fully mixed material is fed into a twin-screw extruder for mixing and granulation; the raw material polyoxymethylene is divided into two parts with a weight ratio of 3:7, and the tracer is uniformly mixed with the raw material polyoxymethylene with the smaller weight ratio to prepare a masterbatch; in this embodiment, the tracer is a lutetium salt compound (Lu(OH)3), and the additives include a lubricant, a formaldehyde absorbent, a primary antioxidant, and a secondary antioxidant; the lubricant is pentaerythritol stearic acid, the formaldehyde absorbent is melamine, the antioxidant is diethylene glycol ether-di(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylic acid, and the secondary antioxidant is tris[2,4-di-tert-butylphenyl]phosphite.

[0043] Example 2

[0044] A method for adding a polyoxymethylene tracer, the method comprising the following steps:

[0045] Step 1: Take the tracer and a portion of polyoxymethylene and put them into a double cone mixer to mix and prepare a masterbatch. The mass ratio between the portion of polyoxymethylene and the tracer is 10:0.003.

[0046] Step 2: Divide the remaining polyoxymethylene from Step 1 into two parts, and put one part of the polyoxymethylene and the additives into the masterbatch from Step 1 and mix them evenly to make a premix.

[0047] Step 3: The other part of the polyoxymethylene from Step 2 is added to the above premix and mixed evenly to form a mixture;

[0048] Step 4: Feed the mixture from Step 3 into a twin-screw extruder for granulation via a loss-in-weight feeder;

[0049] Step 5: Place the particulate matter from Step 4 into a drying oven for drying to obtain polyoxymethylene containing tracer.

[0050] In step 1, the stirring speed for preparing the masterbatch is 500-1000 rpm, and the stirring time is 30 min.

[0051] In step 2, the stirring speed for preparing the premix is ​​500-1000 rpm, and the stirring time is 20 min.

[0052] In step 3, the mixing speed for preparing the mixture is 500-1000 rpm, and the mixing time is 15 min.

[0053] In steps 2 and 3, the mass ratio between one part of the polyoxymethylene and the other part of the polyoxymethylene is 3:4.

[0054] In step 4, the controlled temperatures of each zone of the twin-screw extruder are 165℃, 170℃, 175℃, 180℃, 185℃, 185℃, 190℃, 190℃, 190℃, and 190℃, respectively; the die head temperature is 185℃; the main feed rate is 200–500 kg / h; the screw speed is 200–500 r / min; and the vacuum degree is -0.1–

[0055] -0.5MPa;

[0056] In step 5, the drying temperature of the drying oven is 80-120℃, and the drying time is 2 hours.

[0057] In this embodiment, the tracer is yttrium oxide (Y₂O₃), and the additives include a lubricant, a formaldehyde absorbent, a primary antioxidant, and a secondary antioxidant. The lubricant is polyethylene wax, the formaldehyde absorbent is hydroxymethyl melamine, the primary antioxidant is pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and the secondary antioxidant is bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate.

[0058] Example 3

[0059] A method for adding a polyoxymethylene tracer, the method comprising the following steps:

[0060] Step 1: Take the tracer and a portion of polyoxymethylene and put them into a double cone mixer to mix and prepare a masterbatch. The mass ratio between the portion of polyoxymethylene and the tracer is 20:0.01.

[0061] Step 2: Divide the remaining polyoxymethylene from Step 1 into two parts, and put one part of the polyoxymethylene and the additives into the masterbatch from Step 1 and mix them evenly to make a premix.

[0062] Step 3: The other part of the polyoxymethylene from Step 2 is added to the above premix and mixed evenly to form a mixture;

[0063] Step 4: Feed the mixture from Step 3 into a twin-screw extruder for granulation via a loss-in-weight feeder;

[0064] Step 5: Place the particulate matter from Step 4 into a drying oven for drying to obtain polyoxymethylene containing tracer.

[0065] In step 1, the stirring speed for preparing the masterbatch is 500-1000 rpm and the stirring time is 60 min; in step 2, the stirring speed for preparing the premix is ​​500-1000 rpm and the stirring time is 40 min; in step 3, the stirring speed for preparing the mixture is 500-1000 rpm and the stirring time is 30 min.

[0066] In steps 2 and 3, the mass ratio between one part of the polyoxymethylene and the other part of the polyoxymethylene is 3:4.

[0067] In step 4, the controlled temperatures of each zone of the twin-screw extruder are 165℃, 170℃, 175℃, 180℃, 185℃, 185℃, 190℃, 190℃, 190℃, and 190℃, respectively; the die head temperature is 185℃; the main feed rate is 200–500 kg / h; the screw speed is 200–500 r / min; and the vacuum degree is -0.1–

[0068] -0.5MPa;

[0069] In step 5, the drying temperature of the drying oven is 80-120℃, and the drying time is 4 hours.

[0070] In this embodiment, the tracer is cerium oxide (cerium dioxide), and the additives include a lubricant, a formaldehyde absorbent, a primary antioxidant, and a secondary antioxidant. The lubricant is silicone powder, the formaldehyde absorbent is melamine-formaldehyde condensate, the primary antioxidant is diethylene glycol ether-di(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylic acid, and the secondary antioxidant is a mixture of tris[2,4-di-tert-butylphenyl]phosphite and bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate.

[0071] Example 4

[0072] A method for adding a polyoxymethylene tracer, the method comprising the following steps:

[0073] Step 1: Take the tracer and a portion of polyoxymethylene and put them into a double cone mixer to mix and prepare a masterbatch. The mass ratio between the portion of polyoxymethylene and the tracer is 15:0.05.

[0074] Step 2: Divide the remaining polyoxymethylene from Step 1 into two parts, and put one part of the polyoxymethylene and the additives into the masterbatch from Step 1 and mix them evenly to make a premix.

[0075] Step 3: The other part of the polyoxymethylene from Step 2 is added to the above premix and mixed evenly to form a mixture;

[0076] Step 4: Feed the mixture from Step 3 into a twin-screw extruder for granulation via a loss-in-weight feeder;

[0077] Step 5: Place the particulate matter from Step 4 into a drying oven for drying to obtain polyoxymethylene containing tracer.

[0078] In step 1, the stirring speed for preparing the masterbatch is 500-1000 rpm and the stirring time is 45 min; in step 2, the stirring speed for preparing the premix is ​​500-1000 rpm and the stirring time is 30 min; in step 3, the stirring speed for preparing the mixture is 500-1000 rpm and the stirring time is 22 min.

[0079] In steps 2 and 3, the mass ratio between one part of the polyoxymethylene and the other part of the polyoxymethylene is 3:4.

[0080] In step 4, the controlled temperatures of each zone of the twin-screw extruder are 165℃, 170℃, 175℃, 180℃, 185℃, 185℃, 190℃, 190℃, 190℃, and 190℃, respectively; the die head temperature is 185℃; the main feed rate is 200–500 kg / h; the screw speed is 200–500 r / min; and the vacuum degree is -0.1–

[0081] -0.5MPa;

[0082] Furthermore, in step 5, the drying temperature of the drying oven is 80–120°C, and the drying time is 3 hours.

[0083] In this embodiment, the tracer is a lanthanum salt compound (La(NO3)3), and the additives include a lubricant, a formaldehyde absorbent, a primary antioxidant, and a secondary antioxidant. The lubricant is ethylene bis-stearamide, the formaldehyde absorbent is hydroxymethyl melamine, the primary antioxidant is diethylene glycol ether-di(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylic acid, and the secondary antioxidant is tris[2,4-di-tert-butylphenyl]phosphite.

[0084]

[0085]

[0086]

[0087] The addition methods in Examples 5-17 are the same as those in Example 4, so they will not be described again.

[0088] Test case

[0089] Blank group 1 uses the addition method described in Example 2 above, without adding tracer yttrium oxide (Y2O3);

[0090] Control group 1, using the addition method described in Example 2 above, added 40 ppm of tracer yttrium oxide (Y2O3);

[0091] Blank group 2 uses the addition method described in Example 3 above, without adding tracer cerium oxide (cerium dioxide);

[0092] Control group 3, using the addition method described in Example 3 above, added 40 ppm of tracer cerium oxide (cerium dioxide);

[0093] Blank group 3 uses the addition method described in Example 4 above, without adding the tracer lanthanum salt compound (La(NO3)3);

[0094] Control group 3, using the addition method described in Example 3 above, added 40 ppm of the tracer lanthanum salt compound (La(NO3)3);

[0095] The spectral detection data are as follows:

[0096]

[0097] The data in the table above show that the errors in the Y₂O₃ / cerium dioxide / La(NO₃)₃ content can be detected by X-ray fluorescence spectrometry (XRF) within the range of 0–5 ppm; the characteristic fingerprint peaks of yttrium oxide / cerium oxide with a content of 30–40 ppm can be detected by Raman spectroscopy, with a Raman shift of 377 cm⁻¹. -1 The characteristic peak of YO bond bending vibration is present at 477 cm⁻¹, and the Raman shift is at 477 cm⁻¹. -1 The Raman shift peak area exhibits a characteristic peak of Ce-O symmetric stretching vibration, and increases with increasing Y₂O₃ / cerium dioxide / La(NO₃)₃ content. The polyoxymethylene (POM) products produced using this method can be tracked and tested, preventing counterfeit and substandard products from entering the market. Furthermore, the inventors prepared three blank groups using the same additive method and conducted comparative tests, finding that the Raman spectra of these products were at 377 cm⁻¹. -1 and 477cm -1 No characteristic scattering peaks were observed at any point, indicating that this method is identifiable and meets the tracking requirements. Furthermore, it proves that the addition method of the present invention can achieve uniform mixing of tracers at the ppm level into the raw materials, thereby achieving the characteristics of tracking detection and anti-counterfeiting.

[0098] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for adding a polyoxymethylene tracer, characterized in that: The addition method includes dividing the raw material polyoxymethylene into at least two parts, uniformly mixing the tracer with one part of the raw material polyoxymethylene to prepare a masterbatch, and fully mixing the masterbatch with the remaining raw material polyoxymethylene or a combination of the remaining raw material polyoxymethylene and the additive; the fully mixed material is then fed into a twin-screw extruder for mixing and granulation. The tracer is a metal oxide or salt that will not become ineffective due to reaction or temperature changes during the production of polyoxymethylene; The mass ratio of the mixture of polyoxymethylene and additives to the tracer is 100:0.003 to 0.

01.

2. The method for adding a polyoxymethylene tracer according to claim 1, characterized in that: The tracer is an oxide or salt of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium.

3. The method for adding a polyoxymethylene tracer according to claim 1, characterized in that: The additives include lubricants, formaldehyde absorbents, primary antioxidants, and secondary antioxidants.

4. The method for adding a polyoxymethylene tracer according to claim 3, characterized in that: The lubricant is one or a mixture of several of pentaerythritol stearic acid, polyethylene wax, silicone powder, ethylene bis-stearamide, or stearate; the formaldehyde absorbent is melamine, hydroxymethyl melamine, or melamine-formaldehyde condensate; the primary antioxidant is diethylene glycol ether-di(3-tert-butyl-4-hydroxy-5-methylphenyl)acrylic acid or tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] pentaerythritol ester; and the secondary antioxidant is one or a mixture of two of tris[2,4-di-tert-butylphenyl]phosphite and bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphate.

5. The method for adding a polyoxymethylene tracer according to claim 3, characterized in that: The addition method includes the following steps: Step 1: Take the tracer and a portion of polyoxymethylene and put them into a double cone mixer to mix and prepare a masterbatch. The mass ratio between the portion of polyoxymethylene and the tracer is 10-20: 0.003-0.

01. Step 2: Divide the remaining polyoxymethylene from Step 1 into two parts, and put one part of the polyoxymethylene and the additives into the masterbatch from Step 1 and mix them evenly to make a premix. Step 3: The other part of the polyoxymethylene from Step 2 is added to the above premix and mixed evenly to form a mixture; Step 4: Feed the mixture from Step 3 into a twin-screw extruder for granulation via a loss-in-weight feeder; Step 5: Place the particulate matter from Step 4 into a drying oven for drying to obtain polyoxymethylene containing tracer.

6. The method for adding a polyoxymethylene tracer according to claim 5, characterized in that: The stirring speed for preparing the masterbatch in step 1 is 500-1000 rpm, and the stirring time is 30-60 min. In step 2, the stirring speed for preparing the premix is ​​500-1000 rpm, and the stirring time is 20-40 min. In step 3, the mixing speed for preparing the mixture is 500-1000 rpm, and the mixing time is 15-30 min.

7. The method for adding a polyoxymethylene tracer according to claim 5, characterized in that: In steps 2 and 3, the mass ratio between one part of the polyoxymethylene and the other part of the polyoxymethylene is 3:

4.

8. The method for adding a polyoxymethylene tracer according to claim 5, characterized in that: In step 4, the controlled temperatures of each zone of the twin-screw extruder are 165℃, 170℃, 175℃, 180℃, 185℃, 185℃, 190℃, 190℃, 190℃, and 190℃, respectively. The die head temperature is 185℃, the main feed rate is 200~500kg / h, the screw speed is 200~500r / min, and the vacuum degree is -0.1~-0.5MPa.

9. The method for adding a polyoxymethylene tracer according to claim 5, characterized in that: In step 5, the drying temperature of the drying oven is 80-120℃, and the drying time is 2-4 hours.

10. The use of the tracer as described in any one of claims 1-9 in polyoxymethylene.

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