Method for measuring whiteness of flame-retardant master batch

Abstract

The invention relates to a flame-retardant master batch whiteness detection method which comprises the following steps: (1) according to the diameter of an optical detection channel of an instrument or the specification of a sample holder, selecting a tabletting mold with the corresponding specification of a laboratory infrared tabletting machine; (2) preparing the flame-retardant master batch into tablets through a tabletting mold; and (3) putting the tablets into an instrument for whiteness detection. According to the method for detecting the whiteness of the flame-retardant master batch, a flame-retardant master batch sample to be detected is pressed into a compact and low-scattering tablet through a high-pressure tabletting process based on a Kubelka-Munk optical model, so that the measurement variable coefficient CV of the reflectivity R infinity is reduced to 0.3% or below, and the problem of poor whiteness detection repeatability existing in the industry for a long time is solved.

Description

Technical Field

[0001] This invention belongs to the field of analytical testing technology, specifically relating to a method for determining the whiteness of flame retardant masterbatch based on high-pressure tableting technology, applicable to the field of polymer material quality control. Background Technology

[0002] Flame retardants are chemical substances that reduce the flammability of materials. Adding flame retardants to materials improves their flame-retardant properties and reduces the probability of fire. They are primarily designed for flame retardancy in polymer materials, such as those added to plastic products to enhance their flame-retardant performance.

[0003] Flame retardant masterbatch is a granular product made by organically combining, modifying, and synergistically combining various flame retardant components on the basis of flame retardants, and then mixing, extruding, and granulating it using a twin-screw or triple-screw extruder. Compared to flame retardant powder, it is easier to use. Flame retardant masterbatch is mostly in the size of a tablet, which is comparable to the size of ordinary plastic granules, improving their compatibility and making them easier to disperse and add. It is also hygienic and reduces volatile waste. It is environmentally friendly and dust-free, has good compatibility with plastic resins, and reduces costs, so flame retardant masterbatch is increasingly widely used.

[0004] The whiteness of flame retardant masterbatch is a key indicator affecting the appearance quality of downstream products (such as electronic device housings and automotive interiors). Whiteness not only affects the appearance of the product, but if the color of products is inconsistent between different batches, it may even lead to the scrapping of the entire batch of products, causing incalculable losses to the company.

[0005] Currently, the main types of whiteness measurement methods include visual colorimeters, photoelectric colorimeters, spectrophotometers, spectroradiometers, and whiteness meters. All of these methods work by detecting the reflection of light by an object, requiring the surface to be flat, parallel, and free of defects during testing. However, in actual production, due to the irregular shape and surface roughness of flame-retardant masterbatches, traditional whiteness measurement methods result in significant inconsistencies in light reflection. This leads to fluctuations in whiteness measurement data within the same batch of masterbatches, reaching as high as ±5%, severely impacting product quality control and batch consistency. Statistics show that complaints and returns due to inconsistent whiteness are frequent, and the scrap rate of products produced by downstream customers causes companies millions of yuan in economic losses annually. Therefore, there is an urgent need for a low-cost method for determining the whiteness of flame retardant masterbatches that can be used in various instruments, has good repeatability of test data, and is easy to operate, for batch consistency control of flame retardant masterbatches or for quality monitoring during the masterbatch production process. Summary of the Invention

[0006] The purpose of this invention is to provide a method for determining the whiteness of flame retardant masterbatch. The flame retardant masterbatch is pressed into tablets using an infrared tablet press or a small hydraulic press, so that the surface of the medium is flat and smooth, allowing it to be directly tested without crushing or heating. The method is convenient to operate, generates no dust, and provides accurate, reliable, and repeatable results with high testing efficiency.

[0007] The whiteness value is Hunter Whiteness, calculated using the following formula: Where L represents the lightness value, and a and b represent the chromaticity values. The factors affecting the values ​​of L, a, and b are mainly the color characteristics of the object itself and its surface condition; for example, a rough surface may produce diffuse reflection.

[0008] The Kubelka-Munk (KM) model is a classical two-flow theory describing light scattering and absorption in opaque media, and its equations are as follows:

[0009] In the formula, R ∞ It is the reflectance of an infinitely thick sample (i.e., the intensity of reflected light measured by a whiteness meter). K It is the absorption coefficient (related to the light absorption of the material); S It is the scattering coefficient (related to the material's light scattering ability).

[0010] According to the Kubelka-Munk formula, when S approaches constant, R∞ is determined solely by the material's own absorption coefficient K. However, when the medium surface is rough or the particle distribution is uneven, S An increase in the whiteness value leads to energy attenuation of light in multipath scattering, resulting in diffuse reflection, which is the main reason affecting the detection of whiteness value.

[0011] The technical solution adopted by this invention to solve the above problems is as follows: a method for detecting the whiteness of flame retardant masterbatch, based on the Kubelka-Munk optical model, which involves pressing the flame retardant masterbatch sample to be tested into a dense, low-scattering pellet, comprising the following steps: (1) Select the appropriate tablet mold for the laboratory infrared tablet press according to the diameter of the optical detection channel of the instrument or the specifications of the sample holder; (2) The flame retardant masterbatch is pressed into round sheets using a tableting mold; (3) Place the disc into the instrument for whiteness detection.

[0012] Preferably, the instrument is a whiteness meter or a colorimeter.

[0013] Preferably, the specific steps of step (2) are as follows: a. Mold installation: Assemble the mold sleeve and mold base; b. Sample filling: Place the flame retardant masterbatch into the groove of the tablet press frame and cover it with the upper pressure head; c. Place the mold into the infrared tablet press and tighten the screw to secure the mold. d. Tighten the handle to apply pressure to the sample to the required level; e. Maintain the sample under pressure for a period of time; f. Release the handle and remove the mold; g. Separate the mold and remove the tablet.

[0014] More preferably, the pressure in step d is 30 MPa.

[0015] More preferably, the pressure holding time in step e is 4-6 minutes.

[0016] Compared with the prior art, the advantages of the present invention are as follows: (1) The method for detecting the whiteness of flame retardant masterbatch of the present invention uses a high-pressure pressing process based on the Kubelka-Munk optical model to press the flame retardant masterbatch sample to be tested into a dense and smooth pressing, which significantly reduces the scattering coefficient (S value is reduced by more than 80%) and reduces the coefficient of variation (CV) of reflectance R∞ to below 0.3%, thus solving the problem of poor repeatability of whiteness detection that has existed in the industry for a long time.

[0017] (2) The method for determining the whiteness of flame retardant masterbatch of the present invention uses an infrared tablet press, which does not require high temperature treatment and will not change the discoloration of the material caused by high temperature. It can be directly tableted without crushing or other operations, which is convenient to operate, does not generate dust, and is environmentally friendly. Attached Figure Description

[0018] Figure 1 This is a flowchart for measuring the whiteness of the flame retardant masterbatch of the present invention.

[0019] Figure 2 This is a surface morphology diagram of the decabromodiphenyl ethane masterbatch before it was subjected to high-pressure tableting.

[0020] Figure 3 The image shows the surface morphology of decabromodiphenyl ethane masterbatch after being compressed into tablets at 30 MPa. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0022] like Figure 1 The flowchart shown is for measuring the whiteness of the flame retardant masterbatch of the present invention.

[0023] The whiteness of existing flame retardant masterbatches, namely decabromodiphenyl ethane masterbatch (DB) and brominated polystyrene masterbatch (BPS), was tested. The samples were from Taizhou Baili Chemical Co., Ltd.

[0024] 1. Materials Decabromodiphenyl ethane masterbatch, manufacturer: Taizhou Baili Chemical Co., Ltd.; batch number begins with DB. Brominated polystyrene masterbatch, manufacturer: Taizhou Baili Chemical Co., Ltd.; batch number begins with BPS. 2. Instruments and equipment Electronic balance: Sensitivity 0.0001g Density component for analytical balance Whiteness meter: YP-Z-48A Tableting machine: YP-12 infrared tableting machine Tableting mold specifications: 40mm 3. Operating Steps A method for detecting the whiteness of flame retardant masterbatch includes the following steps: (1) Select the corresponding 40mm tableting mold for the YP-12 infrared tablet press according to the specifications of the sample holder of the YQ-Z-48A whiteness color measuring instrument (the diameter of the sample holder is 40mm). (2) The flame retardant masterbatch is prepared into tablets using a tableting mold, specifically as follows: a. Mold installation: Assemble the mold sleeve and mold base, and place the mold piece on top; b. Sample filling: Weigh 10g of masterbatch sample and spread the particles into the groove of the mold pressing frame, then cover with the upper pressing head; c. Place the mold into the tablet press and tighten the screw to secure the mold. d. Tableting: Tighten the handle, apply pressure to the sample, and hold for 5 minutes; e. Release the handle and remove the mold.

[0025] f. Separate the mold and take out the pressed sample, which is a 5mm thick, 40mm diameter round piece.

[0026] (3) Place the tablet into a YQ-Z-48A whiteness color measuring instrument for whiteness testing.

[0027] The surface smoothness, flatness, and density of the sheets formed under different pressures within a 5-minute pressurization period varied. The surface roughness Sa values ​​of the same sample under different pressures are shown in Tables 1 and 2. Table 1. Whiteness values ​​of decabromodiphenyl ethane masterbatch (DB) under different pressures.

[0028] Table 2. Whiteness values ​​of brominated polystyrene masterbatch (BPS) under different pressures.

[0029] As shown in Tables 1 and 2, through comparative analysis of tablet whiteness data under different pressure conditions at a 5-minute pressurization time, 30 MPa was determined to be the optimal pressurization pressure. This was further analyzed using the Kubelka-Munk model. a. When the pressure increases from 10 MPa to 30 MPa, the surface roughness Sa value of the brominated polystyrene masterbatch decreases from 12.117 μm to 1.989 μm; the surface roughness Sa value of the decabromodiphenyl ethane masterbatch decreases from 13.574 μm to 1.899 μm, causing the scattering coefficient (S) to decrease. b. According to the formula k / S, decreasing S significantly improves the measurement stability of reflectivity R∞ (the coefficient of variation CV decreases from 0.62% to 0.26%). This phenomenon is completely consistent with theoretical predictions, confirming the optimizing effect of the tablet pressing process on the consistency of optical detection.

[0030] Figure 2 The image shows the surface morphology of the decabromodiphenyl ethane masterbatch before high-pressure tableting (i.e., 0 MPa). The surface is relatively rough, with a surface roughness Sa value of 22.409 μm. Figure 3 The image shows the surface morphology of decabromodiphenyl ethane masterbatch after being compressed under high pressure at 30 MPa. The surface is smooth and flat, with a surface roughness Sa value of 2.059 μm. It can be seen that the surface of decabromodiphenyl ethane masterbatch becomes smooth and flat through the high-pressure compression process, and the surface roughness Sa value is reduced, which in turn reduces the scattering coefficient (S). The decabromodiphenyl ethane masterbatch used is from batch DB20250317. Example

[0031] A method for detecting the whiteness of flame retardant masterbatch includes the following steps: (1) Select the corresponding 40mm tableting mold for the YP-12 infrared tablet press according to the specifications of the sample holder of the YQ-Z-48A whiteness color measuring instrument (the diameter of the sample holder is 40mm). (2) The flame retardant masterbatch is prepared into tablets using a tableting mold, specifically as follows: a. Mold installation: Assemble the mold sleeve and mold base, and place the mold piece on top; b. Sample filling: Weigh 10g of masterbatch sample and spread the particles into the groove of the mold pressing frame, then cover with the upper pressing head; c. Place the mold into the tablet press and tighten the screw to secure the mold. d. Tableting: Tighten the handle, apply pressure to the sample to 30 MPa, and maintain for 5 minutes; e. Release the handle and remove the mold.

[0032] f. Separate the mold and take out the pressed sample, which is a 5mm thick, 40mm diameter round piece.

[0033] (3) Place the tablet into a YQ-Z-48A whiteness color measuring instrument for whiteness testing.

[0034] Five batches of each product were tested five times. The test results are shown in Table 3. Table 3. Whiteness test results of flame retardant masterbatch from the examples

[0035] Comparative Example The flame retardant masterbatch was directly spread onto a YQ-Z-48A whiteness colorimeter for whiteness testing. Five batches of each product were tested five times. The results are shown in Table 4. Table 4 Whiteness test values ​​of comparative flame retardant masterbatches

[0036] As shown in Tables 3 and 4, the method for determining the whiteness of flame retardant masterbatch according to the present invention involves pressing the flame retardant masterbatch into tablets using an infrared press and then directly testing it. The coefficient of variation is between (0.1)% and (0.3)%, which is significantly better than the coefficient of variation of the original method (0.69-1.85)%. The results are accurate, reliable, have good repeatability, and high detection efficiency.

[0037] Therefore, according to the Kubelka-Munk formula, tablet compression improves detection accuracy through the following mechanisms: a. Pore elimination: High pressure (30MPa) reduces the gaps between particles, decreases the difference in refractive index, and significantly reduces the scattering coefficient (S); b. Surface mirroring: A smooth surface reduces diffuse reflection and increases the proportion of specular reflection, which conforms to Fresnel's law of reflection.

[0038] By using a physical compression method, flame retardant masterbatch is compressed into dense, smooth tablets, significantly reducing the scattering coefficient (S value) and greatly decreasing the coefficient of variation (CV) of reflectance (R∞). Furthermore, the surface roughness value is reduced by over 90% after compression, greatly improving the accuracy and repeatability of whiteness testing.

[0039] In addition to the above embodiments, the present invention also includes other embodiments. All technical solutions formed by equivalent transformation or equivalent substitution should fall within the protection scope of the claims of the present invention.

Claims

1. A method for detecting the whiteness of flame retardant masterbatch, characterized in that: Based on the Kubelka-Munk optical model, the flame retardant masterbatch sample to be tested is compressed into a dense, low-scattering pellet, including the following steps: (1) Select the appropriate tableting mold for the laboratory infrared tablet press according to the diameter of the instrument's optical detection channel or the specifications of the sample holder; (2) The flame retardant masterbatch sample to be tested is prepared into tablets using a tableting mold; (3) Place the tablet into the instrument for whiteness testing.

2. The method for detecting the whiteness of flame retardant masterbatch according to claim 1, characterized in that: The instrument is a whiteness meter or a colorimeter.

3. The method for detecting the whiteness of flame retardant masterbatch according to claim 1, characterized in that: The specific steps of step (2) are as follows: a. Mold installation: Assemble the mold sleeve and mold base; b. Sample filling: Place the flame retardant masterbatch sample to be tested into the groove of the tablet press frame and cover it with the upper pressure head; c. Place the mold into the infrared tablet press and tighten the screw to secure the mold. d. Tighten the handle to apply pressure to the sample to the required level; e. Maintain the sample under pressure for a period of time; f. Release the handle and remove the mold; g. Separate the mold and remove the tablet.

4. The method for detecting the whiteness of flame retardant masterbatch according to claim 3, characterized in that: The pressure mentioned in step d is 30 MPa.

5. The method for detecting the whiteness of flame retardant masterbatch according to claim 3, characterized in that: The pressure holding time in step e is 4-6 minutes.

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