Layering thickness real-time detection method and detection system for multi-layer co-extrusion film

Abstract

The invention relates to a real-time detection method and a real-time detection system for the layering thickness of a multi-layer co-extrusion film. The layering thickness real-time detection method comprises the following steps: (1) adding an infrared spectrum response agent into a target layer raw material, measuring the density of the target layer raw material, and setting the extrusion amount of the target layer raw material, the width of a multi-layer co-extrusion film and the production line speed; (2) continuously measuring the total thickness of the multi-layer co-extruded film by using an X-ray thickness gauge to obtain an average value; continuously measuring the total thickness of the multi-layer co-extruded film by using an infrared thickness gauge to obtain an average value; (3) acquiring a correction value A of the infrared spectral response agent to the measured value of the target layer; and (4) measuring the real-time numerical value of the total thickness of the multi-layer co-extruded film by using an X-ray thickness gauge, and measuring the real-time numerical value of the total thickness of the multi-layer co-extruded film by using an infrared thickness gauge so as to obtain the real-time numerical value TA of the thickness of the target layer.

Description

Technical Field

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

[0002] Multilayer co-extruded films, due to their unique interlayer structure (e.g., the combination of barrier layers, adhesive layers, and other functional layers), are widely used in fields such as food packaging and electronic device packaging. However, because each layer has different functions, and the functional effects are correlated with the thickness of each layer, targeted testing of the thickness of specific layers (target layers) is necessary to ensure that the resulting multilayer co-extruded film meets application requirements.

[0003] Traditional methods rely primarily on mechanical contact measurement (such as micrometers) and radioactive radiation techniques (such as beta radiation and X-rays). While simple and reliable, mechanical methods can only measure total thickness offline and cannot detect delamination. Furthermore, online monitoring is prone to errors due to film deformation. Radioactive techniques estimate thickness based on the material's absorption rate of radiation, but they carry safety risks associated with radioactive materials (such as the half-life limit of promethium-147) and environmental sensitivity (temperature and pressure fluctuations can amplify errors). These techniques are particularly inadequate for measuring delamination in multilayer structures.

[0004] To overcome the bottleneck of delamination detection, optical technology has 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 (USA) can now measure the thickness of layers of materials such as PP, EVOH, and PVDC online. However, this method has limitations. It requires each layer to be made of a different material. For example, in the case of co-extruded films made of both PP and co-PP, this method can only measure the total thickness, not the thickness of each layer individually. This is limited by optical interference effects (such as fringe interference in ultra-thin films), material compatibility (for example, the complex absorption characteristics of the PVDC layer require verification with low-energy X-rays), and the high cost of high-end equipment. Furthermore, the fuzzy interfaces between layers and edge effects (thickness non-uniformity caused by processing stress) in multi-layer co-extruded films further complicate measurement. Optimizing sampling strategies (such as avoiding edge areas and increasing measurement point density in accordance with the GB / T6672 standard) is crucial to improving data representativeness.

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

[0006] The purpose of the present invention is to disclose a real-time detection method and detection system for the layer thickness of a multi-layer co-extruded film, 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] A first aspect of the present invention is to provide a method for real-time detection of layer thickness of a multi-layer co-extruded film.

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

[0009] The method for real-time layer thickness detection according to the first aspect of the present invention comprises the following steps: (1) Add infrared spectroscopy response agent to the target layer raw material, measure the density of the target layer raw material as ρ, set the extrusion amount of the target layer raw 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 multi-layer co-extruded film is continuously measured using an X-ray thickness gauge, and the average value obtained is T x平均 ; Use an infrared thickness gauge to continuously measure the total thickness of the multilayer co-extruded film at a specific wavelength through a filter, and the average value obtained is T 1平均 ; (3) Obtain the correction value A of the infrared spectrum response agent for the target layer measurement value, A=Q / (ρ×k×s)-(T 1平均 -T x平均 ); (4) Use X-ray thickness gauge to measure the total thickness of multi-layer co-extruded film in real time x实时 , use infrared thickness gauge to measure the total thickness of multi-layer co-extruded film real-time value T 1实时 , obtain the real-time value of the target layer thickness T A , when T 1实时 -T x实时 >Q / (ρ×k×s), T A =T 1实时 -T x实时 -A; When T 1实时 -T x实时 <Q / (ρ×k×s), T A =T 1实时 -T x实时 +A.

[0010] The target layer doped with the infrared spectroscopy agent causes a difference in measurements between the X-ray thickness gauge and the infrared thickness gauge. Using the correction value A, the total thickness measured by the X-ray and infrared thickness gauges can be converted to the thickness of a single target layer, enabling real-time detection of the layer thickness of a multilayer co-extruded film.

[0011] In further embodiments, the infrared light absorption wavelength range of the infrared spectrum responsive agent does not overlap with that of the target layer's raw material, and the filter retains a wavelength range encompassing the infrared light absorption wavelength range of the infrared spectrum responsive agent. For example, when the target layer is made of polypropylene (PP), PP is known to absorb infrared light at wavelengths between 2700 and 3000 nm, as well as near 1460 nm and 1380 nm. Therefore, polythiophene, which absorbs at wavelengths between 450 and 550 nm, can be selected as the infrared spectrum responsive agent. Furthermore, the filter retains a wavelength range between 350 and 1500 nm.

[0012] In a further application embodiment, when there is more than one target layer to be detected in the multi-layer co-extruded film, different infrared spectrum response agents can be added to the raw materials of each target layer.

[0013] 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.

[0014] In further embodiments, the infrared spectroscopy agents that can be selected include halogenated polythiophene derivatives, polyether polymers, aromatic ketone compounds, and aliphatic polyacyl chloride compounds. Different compounds are selected as the infrared spectroscopy agents based on the target layer material to avoid interference with the measurement data caused by overlapping absorption peaks.

[0015] In further application embodiments, the polythiophene or polythiophene derivative is selected from poly-3-bromothiophene, poly-3-bromo-4-methylthiophene, or poly-3,4-dibromothiophene, and has an absorption wavelength below 1100 nm and near 1480 nm. For example, polythiophene can act as a nucleating agent in polypropylene (PP), increasing crystallinity and improving the mechanical properties of PP films. Therefore, in addition to affecting the measured values of an infrared thickness gauge, the infrared spectroscopy responsive agent can also improve the product quality of multilayer co-extruded films.

[0016] 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.

[0017] 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.

[0018] In a further application embodiment, the aliphatic polybasic acyl chloride compound is selected from terephthaloyl chloride, stearoyl chloride and trimesoyl chloride, and its absorption wavelength is around 1740-1800 nm.

[0019] In order to avoid excessive changes in the measured values of the infrared thickness gauge, the amount of the infrared spectrum response agent is within 5wt%.

[0020] The detection system of the second aspect of the present 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, wherein the extrusion mechanism, the cooling and shaping mechanism and the traction and winding mechanism are arranged in sequence, the X-ray thickness gauge and the infrared thickness gauge are arranged 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, and the data processing module has an interactive interface, and outputs a real-time numerical value T of the target layer thickness through the interactive interface. A .

[0021] The present invention solves the problem of difficulty in online detection and monitoring of the thickness of each layer of multilayer co-extruded films. The real-time layer thickness detection method is of great value in improving the quality control of multilayer co-extruded films. Through a combination of infrared light and X-rays, it can not only qualitatively and quantitatively determine product thickness issues and accurately identify thickness fluctuations. The methods and tools employed offer the advantages of non-contact, non-destructive testing and are expected to play an important role in the fields of materials science, thin film technology, and online detection technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the detection system in Example 1; Figure 2 This is a screenshot of the software interface for measuring real-time values using an X-ray thickness gauge in Example 1; Figure 3 This is a screenshot of the software interface for measuring real-time values using an infrared thickness gauge in Example 1; Figure 4 This is a photograph of the double-layer co-extruded film measured offline using a microscope in Example 1; Figure 5 is a schematic diagram of the detection system in Example 2; Figure 6 This is a screenshot of the software interface for measuring real-time values using an X-ray thickness gauge in Example 2; Figure 7 This is a screenshot of the software interface for measuring real-time values using infrared thickness gauge No. 1 in Example 2; Figure 8 This is a screenshot of the software interface for measuring real-time values using infrared thickness gauge No. 2 in Example 2; Figure 9 This is a photograph of the three-layer co-extruded film measured offline using a microscope in Example 2. DETAILED DESCRIPTION

[0023] The following examples further illustrate the present invention, but should not be construed as limiting the present invention. Without departing from the spirit and substance of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention are within the scope of the present invention.

[0024] Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art.

[0025] Example 1: Real-time detection of layer thickness of double-layer co-extruded polypropylene film.

[0026] Schematic diagram of the real-time detection system for the layer thickness of the double-layer co-extruded polypropylene film Figure 1 As shown in the figure, the filter used has an operating band of 350~1500 nm.

[0027] A twin-screw extruder with an in-mold composite double-layer die is used to produce a two-layer co-extruded polypropylene film. Layer A is composed of 5% polythiophene (as an infrared spectroscopy agent) and 95% copolymerized PP, while layer B is 100% homopolymerized PP. Layer B primarily provides support and mechanical strength, while layer A primarily acts as a heat seal.

[0028] (1) Determine the density of the A layer material ρ = 0.90 g / cm 3 , set the extrusion rate of the target layer raw material Q = 400 kg / hour, the width of the multilayer co-extruded film k = 4.8 m, and the production line speed s = 100 m / min; (2) An X-ray thickness gauge and an infrared thickness gauge are installed in front of the winder. After the extrusion mechanism runs stably, the T x平均 =68.31 μm, T 1平均 =83.12 μm; (3) After conversion, the correction value A = 0.62 μm is obtained; (4) Use X-ray thickness gauge to measure the total thickness of multi-layer co-extruded film in real time x实时 =68.72 μm (e.g. Figure 2 As shown), the total thickness of the multi-layer co-extruded film is 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, so T A =T 1实时 -T x实时 -A, obtain the real-time value of the target layer thickness T A =15.18 μm.

[0029] At the same time, 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.

[0030] Mark the area of the double-layer co-extruded polypropylene film currently being measured in step (4), and take a sample for offline thickness measurement using a metallographic microscope. Place the double-layer co-extruded polypropylene film sample into the fixture plane, lock the fixture to fix the sample, and use a tool to cut off the sample protruding from the fixture plane to expose the cross section. The microscope inspection results are as follows: Figure 4 As shown, the measured thickness of layer A is 15.1 μm and the thickness of layer B is 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 is highly accurate and can obtain measurement results in real time, meeting the requirements of non-contact and non-destructive testing.

[0031] Example 2: Real-time detection of layer thickness of three-layer co-extruded polyethylene film.

[0032] Schematic diagram of the real-time detection system for the layer thickness of the three-layer co-extruded polyethylene film Figure 5 As shown in the figure, the working band of the filter used by No. 1 infrared thickness gauge is 350~1500 nm, and the working band of the filter used by No. 2 infrared thickness gauge is 1500~2700 nm.

[0033] A three-layer coextruded polyethylene film was produced using a single-screw extruder and an in-mold three-layer die. Layer A consisted of 5% polythiophene and 95% LLDPE, layer B was 100% HDPE, and layer C was 5% xylyldibutylbenzofuranone and 95% LLDPE. Polythiophene and xylyldibutylbenzofuranone served as infrared spectroscopy agents in layers A and C, respectively.

[0034] (1) Determine the density of the A layer material ρ = 0.921 g / cm 3 , set the extrusion rate of the target layer raw material Q = 90 kg / hour, the width of the multilayer co-extruded film k = 2 m, and the production line speed s = 40 m / min; (2) Determine the density of the C layer material ρ = 0.921 g / cm 3 , set the extrusion rate of the target layer raw material Q = 90 kg / hour, the width of the multilayer co-extruded film k = 2 m, and the production line speed s = 40 m / min; (3) An X-ray thickness gauge and two infrared thickness gauges are installed in front of the winder. After the extrusion mechanism runs stably, the T x平均 =42.34 μm, T 1平均 =45.24 μm, T 2平均 =43.86 μm; (4) After conversion, the correction value of layer A is A=17.46 μm; the correction value of layer C is C=18.84 μm; (5) Use X-ray thickness gauge to measure the total thickness of multi-layer co-extruded film in real time x实时 =42.44 μm (e.g. Figure 6 As shown), the total thickness of the multi-layer co-extruded film is measured using a No. 1 infrared thickness gauge. 1实时 =44.91 μm (e.g. Figure 7 As shown in the figure), the total thickness of the multi-layer co-extruded film is measured using a No. 2 infrared thickness gauge. 2实时 =44.13μm (e.g. Figure 8 shown); (6) Due to T 1实时 -T x实时 =2.47 μm, the A layer parameter Q / (ρ×k×s)=20.36 μm, so T A =T 1实时 -T x实时 +A, get the real-time value of the thickness of layer A T A =19.93 μm; C layer parameter Q / (ρ×k×s)=20.36 μm, so T C =T 1实时 -T x实时 +C, get the real-time value of the C layer thickness T C =20.53 μm.

[0035] At the same time, 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.

[0036] Mark the area of the double-layer co-extruded polyethylene film currently being measured in step (6), and take a sample for offline thickness measurement using a metallographic microscope. Place the three-layer co-extruded polyethylene film sample into the fixture plane, lock the fixture to fix the sample, and use a tool to cut off the sample protruding from the fixture plane to expose the cross section. The microscope inspection results are as follows: Figure 9 As shown, the thickness of layer A was measured to be 20.2 mm, the thickness of layer B was 2.0 mm, and the thickness of layer C was 20.5 mm, which is basically consistent with the measurement results of the real-time layer thickness detection method.

[0037] Example 3: Real-time detection of layer thickness of three-layer co-extruded polypropylene film.

[0038] A three-layer co-extruded polypropylene film was produced using a twin-screw extruder with an in-mold composite three-layer die. Layer A consisted of 5% polythiophene and 95% copolymerized PP, layer B was 100% homopolymerized PP, and layer C was 5% xylyl dibutylbenzofuranone and 95% copolymerized PP.

[0039] (1) Determine the density of the A layer material ρ = 0.90 g / cm 3 , set the extrusion rate of the target layer raw material Q = 70 kg / hour, the width of the multilayer co-extruded film k = 4.8 m, and the production line speed s = 140 m / min; (2) Determine the density of the C layer material ρ = 0.90 g / cm 3 , set the extrusion rate of the target layer raw material Q = 60 kg / hour, the width of the multilayer co-extruded film k = 4.8 m, and the production line speed s = 140 m / min; (3) An X-ray thickness gauge and two infrared thickness gauges are installed in front of the winder. After the extrusion mechanism runs stably, the T x平均 =22.57 μm, T 1平均 =24.35 μm, T 2平均 =24.11 μm; (4) After conversion, the correction value of layer A is A=0.15 μm; the correction value of layer C is C=0.11 μm; (5) Use X-ray thickness gauge to measure the total thickness of multi-layer co-extruded film in real time x实时 =22.55 μm, using infrared thickness gauge to measure the total thickness of multi-layer co-extruded film real-time value T 1实时 =24.48μm, and obtain the real-time value of the thickness of layer A T A =1.78 μm; (6) Use X-ray thickness gauge to measure the total thickness of multi-layer co-extruded film in real time x实时 =22.55 μm, using infrared thickness gauge to measure the total thickness of multi-layer co-extruded film real-time value T 2实时=24.25 μm, and obtain the real-time value of the C layer thickness T C =1.59 μm.

[0040] At the same time, 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.

[0041] 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 embodied 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 illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

Claims

1. A method for real-time detection of layer thickness of a multi-layer co-extruded film, characterized in that: Including steps: (1) Add infrared spectroscopy response agent to the target layer raw material, measure the density of the target layer raw material as ρ, set the extrusion amount of the target layer raw 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 multi-layer co-extruded film is continuously measured using an X-ray thickness gauge, and the average value obtained is T x平均 ; Use an infrared thickness gauge to continuously measure the total thickness of the multilayer co-extruded film at a specific wavelength through a filter, and the average value obtained is T 1平均 ; (3) Obtain the correction value A of the infrared spectrum response agent for the target layer measurement value, A=Q / (ρ×k×s)-(T 1平均 -T x平均 ); (4) Use X-ray thickness gauge to measure the total thickness of multi-layer co-extruded film in real time x实时 , use infrared thickness gauge to measure the total thickness of multi-layer co-extruded film real-time value T 1实时 , obtain the real-time value of the target layer thickness T A , when T 1实时 -T x实时 >Q / (ρ×k×s), T A =T 1实时 -T x实时 -A; When T 1实时 -T x实时 <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 spectrum response agent 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 spectrum response agent.

3. The method for real-time detection of layer thickness according to claim 2, characterized in that: The infrared spectrum response agent is selected from one or more of halogenated polythiophene derivatives, polyether polymers, aromatic ketone compounds and aliphatic polyacyl chloride 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 dimethylbenzene dibutylbenzofuranone, p-hydroxyacetophenone or 2-phenylchromone.

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

8. The method for real-time detection of layer thickness according to any one of claims 1 to 7, characterized in that: When there are multiple target layers, the infrared spectrum responsive agent added to the raw material 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 the infrared thickness gauges configured is greater than or equal to the number of the 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 apparatus comprises 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 in sequence. The X-ray thickness gauge and the infrared thickness gauge are arranged 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, and outputs a real-time value T of the target layer thickness through the interactive interface. A .

Images