A method and system for real-time detection of the layer thickness of multilayer co-extruded films.

Abstract

This invention relates to a method and system for real-time detection of the layer thickness of a multilayer co-extruded film. The real-time layer thickness detection method includes the following steps: (1) adding an infrared spectral responsor to the target layer raw material, determining the density of the target layer raw material, and setting the extrusion amount of the target layer raw material, the width of the multilayer co-extruded film, and the production line speed; (2) continuously measuring the total thickness of the multilayer co-extruded film using an X-ray thickness gauge and obtaining the average value; continuously measuring the total thickness of the multilayer co-extruded film using an infrared thickness gauge and obtaining the average value; (3) obtaining the correction value A of the infrared spectral responsor for the measured value of the target layer; (4) measuring the real-time value of the total thickness of the multilayer co-extruded film using an X-ray thickness gauge and measuring the real-time value of the total thickness of the multilayer co-extruded film using an infrared thickness gauge, thereby obtaining the real-time value T of the target layer thickness. A .

Description

Technical Field

[0001] This invention relates to the field of optical measurement technology, and in particular to a method and system for real-time detection of the layer thickness of a multilayer co-extruded film. Background Technology

[0002] Multilayer co-extruded films are widely used in food packaging, electronic device encapsulation, and other fields due to their unique interlayer structure (such as the combination of functional layers like barrier layers and adhesive layers). However, since each layer has different functions, and the functional effect is related to the thickness of that layer, it is necessary to specifically test the thickness of a particular layer (target layer) to ensure that the produced multilayer co-extruded film meets the application requirements.

[0003] Traditional methods primarily rely on mechanical contact measurements (such as micrometers) and radiographic techniques (such as beta rays and X-rays). While mechanical methods are simple and reliable, they can only measure the total thickness offline and cannot perform layered detection. Furthermore, online monitoring is prone to errors due to film deformation. Radiographic techniques estimate thickness by measuring the absorption rate of radiation by the material, but they suffer from drawbacks such as the safety risks associated with radioactive materials (e.g., the half-life limitation of promethium-147) and environmental sensitivity (temperature and pressure fluctuations amplify errors). They are particularly ineffective for layered measurements of multi-layered structures.

[0004] To overcome the bottleneck in layer thickness detection, optical technology has gradually become a research hotspot. For example, near-infrared spectroscopy utilizes the absorption characteristics of different resins at specific wavelengths to measure layer thickness. The FG-710 thickness gauge from NDC Corporation in the United States can already detect the layer thickness of materials such as PP, EVOH, and PVDC online. However, this method has limitations. It requires that each layer be made of different materials. Taking a co-extruded film of homogeneous PP and copolymer PP as an example, this method can only measure the total thickness and cannot measure the thickness of each individual layer. It is also limited by optical interference effects (such as stripe interference in ultrathin films) and material applicability (such as the complex absorption characteristics of PVDC layers, which require verification with low-energy X-rays), and the high cost of high-end equipment. In addition, the ambiguity of the interlayer interfaces and edge effects (thickness non-uniformity caused by processing stress) of multilayer co-extruded films further exacerbate the measurement difficulty, requiring optimization of sampling strategies (such as avoiding edge areas based on the GB / T6672 standard and increasing the density of measurement points) to improve data representativeness.

[0005] In summary, although existing technologies have made progress in layered detection and dynamic monitoring, they still face multiple challenges in terms of material compatibility, equipment economy, and the ability to analyze complex structures. There is an urgent need to develop innovative solutions that balance high precision, low cost, and wide applicability. Summary of the Invention

[0006] The purpose of this invention is to disclose a method and system for real-time detection of the layer thickness of multilayer co-extruded films, so as to solve one or more technical problems existing in the prior art and provide at least one beneficial option or create conditions.

[0007] The first aspect of this invention is to provide a method for real-time detection of the layer thickness of a multilayer co-extruded film.

[0008] A second aspect of the present invention is to provide a detection system that applies the real-time layer thickness detection method described in the first aspect of the present invention.

[0009] The real-time layer thickness detection method of the first aspect of this invention includes the following steps:

[0010] (1) Add an infrared spectroscopy responder to the target layer material, determine the density of the target layer material as ρ, set the extrusion amount of the target layer material as Q, the width of the multilayer co-extruded film as k, and the production line speed as s;

[0011] (2) The total thickness of the multilayer co-extruded film was continuously measured using an X-ray thickness gauge, and the average value obtained was T. x平均 The total thickness of the multilayer co-extruded film was continuously measured at a specific wavelength using an infrared thickness gauge through a filter. The average value obtained was T. 1平均 ;

[0012] (3) Obtain the correction value A for the measured values ​​of the target layer by the infrared spectral responsor.

[0013] A=Q / (ρ×k×s)-(T 1平均 -T x平均 );

[0014] (4) The real-time value of the total thickness T of the multilayer co-extruded film was measured using an X-ray thickness gauge. x实时 The real-time value T of the total thickness of the multilayer co-extruded film was measured using an infrared thickness gauge. 1实时 Obtain the real-time numerical value T of the target layer thickness. A When T 1实时 -T x实时 When Q / (ρ×k×s) >

[0015] T A =T 1实时 -T x实时 -A;

[0016] When T 1实时 -T x实时 When < Q / (ρ×k×s),

[0017] T A =T 1实时 -T x实时 +A.

[0018] The target layer, doped with the infrared spectral responsor, causes a measurement difference between the X-ray thickness gauge and the infrared thickness gauge. Using a correction value A, the total real-time thickness measured by the X-ray and infrared thickness gauges can be converted into the single-layer thickness of the target layer, thereby enabling real-time detection of the layer thickness of the multilayer co-extruded film.

[0019] In a further application embodiment, the infrared absorption wavelength range of the infrared spectral responder does not overlap with the infrared absorption wavelength range of the target layer raw material, and the wavelength range retained by the filter includes the infrared absorption wavelength range of the infrared spectral responder. For example, when the target layer is polypropylene (PP) material, it is known that PP absorbs infrared light at wavelengths of 2700~3000 nm, around 1460 nm, and around 1380 nm. Therefore, polythiophene with an absorption wavelength of 450~550 nm can be selected as the infrared spectral responder. Meanwhile, the wavelength range retained by the filter is 350~1500 nm.

[0020] In a further application implementation, when there is more than one target layer to be detected in the multilayer co-extruded film, different infrared spectral response agents can be added to the raw materials of each target layer.

[0021] In a further application implementation, when there are multiple target layers to be detected, each target layer needs to be equipped with at least one infrared thickness gauge adapted to the absorption peak wavelength of the target layer for detection.

[0022] In further application embodiments, the optional infrared spectral responders include halogenated polythiophene derivatives, polyether polymers, aromatic ketones, and aliphatic polyacrylamide chlorides. Different compounds are selected as infrared spectral responders based on different target layer materials to avoid interference in measurement data caused by overlapping absorption peak ranges.

[0023] In a further application embodiment, the polythiophene or polythiophene derivative is selected from poly-3-bromothiophene, poly-3-bromo-4-methylthiophene, or poly-3,4-dibromothiophene, with absorption wavelengths below 1100 nm and around 1480 nm. Taking polythiophene as an example, it can act as a nucleating agent for PP, improving crystallinity and enhancing the mechanical properties of PP films. Therefore, the infrared spectral responsor, in addition to influencing the measurement values ​​of infrared thickness gauges, can also improve the product quality of multilayer co-extruded films.

[0024] In a further application embodiment, the polyether polymer is selected from polyethylene oxide or polyphenylene ether, and its absorption wavelength is around 1150~1060 nm.

[0025] In a further application embodiment, the aromatic ketone compound is selected from xylyldibutylbenzofuranone, p-hydroxyacetophenone or 2-phenylchromone, and its absorption wavelength is around 1680~1750 nm, 1150~1300 nm and 1030~1140 nm.

[0026] In a further application embodiment, the aliphatic polyacryl chloride compound is selected from terephthaloyl chloride, stearyl chloride and pyromellitic trimethylol chloride, and its absorption wavelength is around 1740~1800 nm.

[0027] To avoid excessive variations in the measurement values ​​of the infrared thickness gauge, the amount of the infrared spectral response agent is kept below 5 wt%.

[0028] The detection system of the second aspect of this invention includes an extrusion mechanism, a cooling and shaping mechanism, a traction and winding mechanism, an X-ray thickness gauge, a data processing module, and at least one infrared thickness gauge. The extrusion mechanism, the cooling and shaping mechanism, and the traction and winding mechanism are arranged sequentially. The X-ray thickness gauge and the infrared thickness gauge are located next to the cooling and shaping mechanism. The X-ray thickness gauge and the infrared thickness gauge are electrically connected to the data processing module. The data processing module has an interactive interface, through which it outputs the real-time value T of the target layer thickness. A .

[0029] This invention solves the problem of difficulty in online detection and monitoring of the thickness of each layer in multilayer co-extruded films. The described real-time layer thickness detection method is of great value for improving the quality control of multilayer co-extruded films. By combining infrared light and X-rays, it is possible to determine the thickness of the product not only qualitatively but also quantitatively, accurately identifying thickness fluctuations. The methods and tools used have the advantages of non-contact and non-destructive testing, and can play an important role in the fields of materials science, thin film technology, and online detection technology. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the detection system in Example 1;

[0031] Figure 2 This is a screenshot of the software interface for measuring real-time values ​​using an X-ray thickness gauge in Example 1;

[0032] Figure 3 This is a screenshot of the software interface for measuring real-time values ​​using an infrared thickness gauge in Example 1;

[0033] Figure 4 These are photographs taken offline using a microscope to measure the bilayer co-extruded film in Example 1;

[0034] Figure 5 This is a schematic diagram of the detection system in Example 2;

[0035] Figure 6 This is a screenshot of the software interface for measuring real-time values ​​using an X-ray thickness gauge in Example 2;

[0036] Figure 7 This is a screenshot of the software interface for measuring real-time values ​​using infrared thickness gauge No. 1 in Example 2;

[0037] Figure 8 This is a screenshot of the software interface for measuring real-time values ​​using infrared thickness gauge No. 2 in Example 2;

[0038] Figure 9 This is a photograph of a three-layer co-extruded film measured offline using a microscope in Example 2. Detailed Implementation

[0039] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Any modifications and substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the present invention are within the scope of the present invention.

[0040] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0041] Example 1: Real-time detection of the layer thickness of a double-layer co-extruded polypropylene film.

[0042] A schematic diagram of a real-time thickness detection system for preparing double-layer co-extruded polypropylene films is shown below. Figure 1 As shown, the operating wavelength of the filter used is 350~1500 nm.

[0043] A twin-screw extruder with an in-mold composite double-layer die was used to prepare a double-layer co-extruded polypropylene film. Layer A consisted of 5% polythiophene (as an infrared spectroscopy responder) and 95% copolymerized PP, while layer B was composed of 100% homopolymerized PP. Layer B primarily provides support and mechanical strength, while layer A mainly serves for heat sealing.

[0044] (1) The density of the raw material in layer A was determined to be ρ = 0.90 g / cm³. 3 The target layer raw material extrusion rate was set to Q = 400 kg / hour, the width of the multilayer co-extruded film was set to k = 4.8 m, and the production line speed was set to s = 100 m / min.

[0045] (2) An X-ray thickness gauge and an infrared thickness gauge are installed in front of the winding machine. After the extrusion mechanism is running stably, the thickness T is measured. x平均 =68.31 μm, T was measured 1平均 =83.12 μm;

[0046] (3) After conversion, the correction value A = 0.62 μm is obtained;

[0047] (4) The real-time value of the total thickness T of the multilayer co-extruded film was measured using an X-ray thickness gauge. x实时 =68.72 μm (e.g.) Figure 2 As shown), the real-time value T of the total thickness of the multilayer co-extruded film was measured using an infrared thickness gauge. 1实时 =84.52 μm (e.g.) Figure 3 As shown), due to T 1实时 -T x实时 =15.80 μm, Q / (ρ×k×s)=15.43 μm, therefore T A =T 1实时 -T x实时 -A, obtains the real-time numerical value T of the target layer thickness. A =15.18 μm.

[0048] Meanwhile, since the real-time value of the total thickness T is known... x实时 =68.72 μm, so the thickness of layer B can also be calculated as T. B =T x实时 -T A =53.54 μm.

[0049] Marking step (4): For the currently measured area of ​​the double-layer co-extruded polypropylene film, take a sample for offline metallographic microscopy thickness measurement. Place the double-layer co-extruded polypropylene film sample into the clamp plane, lock the clamp to fix the sample, and use a tool to cut off the sample protruding from the clamp plane to expose the cross-section. Microscopic inspection results are as follows. Figure 4 As shown, the measured thickness of layer A was 15.1 μm and the thickness of layer B was 53.5 μm, which is basically consistent with the measurement results of the real-time layer thickness detection method. This proves that the real-time layer thickness detection method has high accuracy, can obtain measurement results in real time, and meets the requirements of non-contact and non-destructive testing.

[0050] Example 2: Real-time detection of the layer thickness of a three-layer co-extruded polyethylene film.

[0051] A schematic diagram of a real-time detection system for the delamination thickness of a three-layer co-extruded polyethylene film is shown below. Figure 5 As shown, the working wavelength of the filter used in infrared thickness gauge No. 1 is 350~1500 nm, and the working wavelength of the filter used in infrared thickness gauge No. 2 is 1500~2700 nm.

[0052] A three-layer co-extruded polyethylene film was prepared using a single-screw extruder with an in-mold composite three-layer die. Layer A consisted of 5% polythiophene and 95% LLDPE, layer B was 100% HDPE, and layer C consisted of 5% xylyldibutylbenzofuranone and 95% LLDPE. Polythiophene and xylyldibutylbenzofuranone were used as infrared spectral responders for layers A and C, respectively.

[0053] (1) The density of the raw material in layer A was measured to be ρ = 0.921 g / cm³. 3 The target layer raw material extrusion rate is set to Q = 90 kg / hour, the width of the multilayer co-extruded film is set to k = 2 m, and the production line speed is set to s = 40 m / min.

[0054] (2) The density of the raw material in layer C was determined to be ρ = 0.921 g / cm³. 3 The target layer raw material extrusion rate is set to Q = 90 kg / hour, the width of the multilayer co-extruded film is set to k = 2 m, and the production line speed is set to s = 40 m / min.

[0055] (3) One X-ray thickness gauge and two infrared thickness gauges are installed in front of the winding machine. After the extrusion mechanism is running stably, the thickness T is measured. x平均 =42.34 μm, T was measured 1平均 =45.24 μm, T was measured 2平均 =43.86 μm;

[0056] (4) After conversion, the correction value for layer A is A=17.46 μm; the correction value for layer C is C=18.84 μm;

[0057] (5) The real-time value of the total thickness T of the multilayer co-extruded film was measured using an X-ray thickness gauge. x实时 =42.44 μm (e.g.) Figure 6 As shown in the figure, the real-time value T of the total thickness of the multilayer co-extruded film was measured using an infrared thickness gauge No. 1. 1实时 =44.91 μm (e.g.) Figure 7 As shown in the figure, the real-time value T of the total thickness of the multilayer co-extruded film was measured using an infrared thickness gauge No. 2. 2实时 =44.13μm (e.g.) Figure 8 (as shown)

[0058] (6) Due to T 1实时 -T x实时 =2.47 μm, layer A parameter Q / (ρ×k×s)=20.36 μm, therefore T A =T 1实时 -T x实时 +A, obtain the real-time value T of the thickness of layer A. A =19.93 μm; C-layer parameter Q / (ρ×k×s)=20.36 μm, therefore TC =T 1实时 -T x实时 +C, to obtain the real-time value T of the C layer thickness. C =20.53 μm.

[0059] Meanwhile, since the real-time value of the total thickness T is known... x实时 =42.44 μm, so the thickness of layer B can also be calculated as T. B =T x实时 -T A -T C =1.98 μm.

[0060] Marking step (6): For the currently measured double-layer co-extruded polyethylene film area, take a sample for offline metallographic microscopy thickness measurement. Place the triple-layer co-extruded polyethylene film sample into the clamp plane, lock the clamp to fix the sample, and use a tool to cut off the sample protruding from the clamp plane to expose the cross-section. Microscopic inspection results are as follows. Figure 9 As shown, the thickness of layer A was measured to be 20.2 mm, layer B to be 2.0 mm, and layer C to be 20.5 mm, which is basically consistent with the measurement results of the real-time layer thickness detection method.

[0061] Example 3: Real-time detection of the layer thickness of a three-layer co-extruded polypropylene film.

[0062] A three-layer co-extruded polypropylene film was prepared using a twin-screw extruder with an in-mold composite three-layer die. The A layer consisted of 5% polythiophene and 95% copolymer PP, the B layer consisted of 100% homopolymer PP, and the C layer consisted of 5% xylyl dibutylbenzofuranone and 95% copolymer PP.

[0063] (1) The density of the raw material in layer A was determined to be ρ = 0.90 g / cm³. 3 The target layer raw material extrusion rate was set to Q = 70 kg / hour, the width of the multilayer co-extruded film was set to k = 4.8 m, and the production line speed was set to s = 140 m / min.

[0064] (2) The density of the raw material in layer C was determined to be ρ = 0.90 g / cm³. 3 The target layer raw material extrusion rate was set to Q = 60 kg / hour, the width of the multilayer co-extruded film was set to k = 4.8 m, and the production line speed was set to s = 140 m / min.

[0065] (3) One X-ray thickness gauge and two infrared thickness gauges are installed in front of the winding machine. After the extrusion mechanism is running stably, the thickness T is measured. x平均 =22.57 μm, T was measured 1平均 =24.35 μm, T was measured 2平均 =24.11 μm;

[0066] (4) After conversion, the correction value for layer A is A=0.15 μm; the correction value for layer C is C=0.11 μm;

[0067] (5) The real-time value of the total thickness T of the multilayer co-extruded film was measured using an X-ray thickness gauge. x实时 =22.55 μm, the real-time value of the total thickness T of the multilayer co-extruded film was measured using an infrared thickness gauge. 1实时 =24.48μm, the real-time numerical value T of the thickness of layer A was obtained. A =1.78 μm;

[0068] (6) The real-time value of the total thickness T of the multilayer co-extruded film was measured using an X-ray thickness gauge. x实时 =22.55 μm, the real-time value of the total thickness T of the multilayer co-extruded film was measured using an infrared thickness gauge. 2实时 =24.25 μm, and the real-time numerical value T of the C layer thickness was obtained. C =1.59 μm.

[0069] Meanwhile, since the real-time value of the total thickness T is known... x实时 =22.55 μm, so the thickness of layer B can also be calculated as T. B =T x实时 -T A -T C =19.18 μm.

[0070] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for real-time detection of the layer thickness of a multilayer co-extruded film, characterized in that, Including the following steps: (1) Add an infrared spectroscopy responder to the target layer material, determine the density of the target layer material as ρ, set the extrusion amount of the target layer material as Q, the width of the multilayer co-extruded film as k, and the production line speed as s; (2) The total thickness of the multilayer co-extruded film was continuously measured using an X-ray thickness gauge, and the average value obtained was T. x平均 The total thickness of the multilayer co-extruded film was continuously measured at a specific wavelength using an infrared thickness gauge through a filter. The average value obtained was T. 1平均 ; (3) Obtain the correction value A of the infrared spectral responsor to the measured value of the target layer. A=Q / (ρ×k×s)-(T 1平均 -T x平均 ); (4) The real-time value of the total thickness T of the multilayer co-extruded film was measured using an X-ray thickness gauge. x实时 The real-time value T of the total thickness of the multilayer co-extruded film was measured using an infrared thickness gauge. 1实时 Obtain the real-time numerical value T of the target layer thickness. A When T 1实时 -T x实时 When Q / (ρ×k×s) > T A =T 1实时 -T x实时 -A; When T 1实时 -T x实时 When < Q / (ρ×k×s), T A =T 1实时 -T x实时 +A。 2. The method for real-time detection of layer thickness according to claim 1, characterized in that, The infrared light absorption wavelength range of the infrared spectral responder does not overlap with the infrared light absorption wavelength range of the target layer raw material, and the wavelength range retained by the filter includes the infrared light absorption wavelength range of the infrared spectral responder.

3. The method for real-time detection of layer thickness according to claim 2, characterized in that, The infrared spectral responder is selected from one or more of halogenated polythiophene derivatives, polyether polymers, aromatic ketones, and aliphatic polyacrylamide compounds.

4. The method for real-time detection of layer thickness according to claim 3, characterized in that, The polythiophene, or polythiophene derivative, is selected from polythiophene, poly-3-bromothiophene, poly-3-bromo-4-methylthiophene, or poly-3,4-dibromothiophene.

5. The method for real-time detection of layer thickness according to claim 3, characterized in that, The polyether polymer is selected from polyethylene oxide or polyphenylene ether.

6. The method for real-time detection of layer thickness according to claim 3, characterized in that, The aromatic ketone compound is selected from xylyldibutylbenzofuranone, p-hydroxyacetophenone, or 2-phenylchromone.

7. The method for real-time detection of layer thickness according to claim 3, characterized in that, The aliphatic polyacryl chloride compound is selected from terephthaloyl chloride, stearoyl chloride, and pyromellitic trimethylol chloride.

8. The method for real-time detection of layer thickness according to any one of claims 1 to 7, characterized in that, When multiple target layers exist, the infrared spectral responder added to the raw materials of each target layer is different.

9. The method for real-time detection of layer thickness according to claim 8, characterized in that, The number of infrared thickness gauges configured is greater than or equal to the number of target layers.

10. A detection system based on the real-time layer thickness detection method according to any one of claims 1 to 9, characterized in that, The system includes an extrusion mechanism, a cooling and shaping mechanism, a traction and winding mechanism, an X-ray thickness gauge, a data processing module, and at least one infrared thickness gauge. The extrusion mechanism, the cooling and shaping mechanism, and the traction and winding mechanism are arranged sequentially. The X-ray thickness gauge and the infrared thickness gauge are located next to the cooling and shaping mechanism and are electrically connected to the data processing module. The data processing module has an interactive interface through which it outputs the real-time value T of the target layer thickness. A .

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