Method for evaluating raw material for low-density polyethylene electronic protection film

Abstract

This invention relates to an evaluation method for low-density polyethylene electronic protective film raw materials. By controlling the sample processing method and crystal point testing conditions, and establishing the relationship between the crystal point of the resin blown film and the melt strength, the method can accurately and quickly determine whether the raw material is qualified.

Description

Technical Field

[0001] This invention relates to the field of polymer resin evaluation, and more specifically to an evaluation method for low-density polyethylene electronic protective film raw materials. Background Technology

[0002] Low-density polyethylene (LDPE) is the earliest industrialized and most produced type of polyethylene, primarily used in film products, accounting for 62.3% of its production. Its films possess certain tensile strength, good impact resistance, tear and puncture resistance, and its low crystallinity gives it the best transparency among polyethylenes, with haze as low as 5%. It has excellent processing performance and good bubble stability, making it very suitable for blown film production. Its films are mainly used in packaging films, agricultural films, heavy-duty packaging films, and medical packaging films, with packaging films dominating at approximately 44.6%. With the rapid development of the information industry and the widespread application of high-end optical devices, electronic protective films have become one of the key materials in high-end electronics and optics. During transportation, storage, processing, or assembly, it is often necessary to protect the surfaces of materials and components from dust contamination or scratches caused by mechanical damage. One common method is to apply a protective film to the surface of the object being protected. After transportation, storage, processing, or assembly, the protective film is removed, achieving the purpose of protecting the material surface. It is also used for surface protection of finished products, such as the protection of optical lenses in high-end cameras, tablet computers, and light guide plates.

[0003] Crystal points in LDPE resin are the main reason for substandard quality of LDPE protective films. While the origins of these crystal points vary, most agree that long-chain branching and macromolecular gelation are the primary contributing factors. Existing literature has explored controlling raw material crystal points through optimized polymerization processes, aiming to control product crystal points by controlling the raw material structure. However, rapid and effective methods for detecting crystal points are currently lacking. The effectiveness of structural performance control can only be determined after downstream user testing, resulting in a significant time lag. Poor performance can lead to substantial losses for both manufacturers and downstream users.

[0004] The existing methods for evaluating thin film crystal points are as follows:

[0005] CN105922689A discloses a high-viscosity self-adhesive surface protective film and its manufacturing method. The surface protective film includes a self-adhesive layer, an intermediate layer, and an anti-adhesive layer. The self-adhesive layer comprises ultra-low density polyethylene and flexible polypropylene. The intermediate layer comprises one or a mixture of low-crystal-point ethylene-propylene copolymer and polyethylene. The anti-adhesive layer is made of block copolymer polypropylene. This invention also discloses a method for manufacturing a high-transparency self-adhesive surface protective film, which involves sequentially performing raw material dust removal, automatic weighing and metering of raw materials, heated extrusion, high-efficiency filtration, co-extrusion film formation, cooling and shaping, automatic thickness control, defect detection, edge trimming and winding, aging treatment, and slitting and packaging. This patent controls product quality by controlling the number and size of crystal points in the film.

[0006]

[0007] As can be seen from the table above, crystal points smaller than 0.2mm were not included in the statistics, but these crystal points have a significant impact on the quality of optical protective films, and their size range cannot meet the quality requirements of LDPE raw materials for optical protective films.

[0008] JB / T10437-2004, "Cross-linkable Polyethylene Insulation Material for Wires and Cables," discloses a method for detecting the impurity content of YJ-35 and YJG-35 type cross-linkable polyethylene insulation materials. When the sample strip is irradiated by a light beam, the impurity particles are light-blocking. A constant, continuous, and adjustable light source is used. Under this light beam, the transmitted and blocked light beams of the sample strip are received by an electronic camera, and the impurity particle detector detects the size and number of particles. The resolution of the impurity particle detector should be better than 100 μm. The sample is a strip-shaped sheet material with a thickness of (0.5–0.8) mm, a width of (50 ± 3) mm, and a weight of approximately 1000 g. The sample is prepared using a small extruder method, and the surface of the strip-shaped sheet material is made smooth, clean, and free of contamination by guide rollers and calendering rollers. The number of impurity particles (0.175–0.250) mm on a 1 kg sample strip should not exceed 5, and the number of impurity particles larger than 0.250 mm should be zero. This method does not include statistics on crystal points smaller than 0.175 mm. These crystal points have a significant impact on the quality of optical protective films, and their dimensional accuracy cannot meet the quality requirements of LDPE raw materials for optical protective films.

[0009] CN112710669A discloses a method for rapidly evaluating crystal points in homopolymer polypropylene lithium-ion battery rigid elastic separators, specifically involving a method for evaluating crystal points in homopolymer polypropylene lithium-ion battery rigid elastic separators. The method includes: using a twin-screw extruder to extrude lithium-ion battery separator material through casting rollers; before winding the rigid elastic film, installing an online defect detector at a position after extrusion; before traction winding, stretching and extending the cast film through multiple layers, then flattening it between the last two sets of casting rollers to form a rigid elastic film; using the online defect detector to detect crystal points in the lithium-ion battery rigid elastic separator, collecting crystal point data, and estimating product quality based on the number of crystal point samples collected according to crystal point classification. This invention uses an online defect detector to obtain the relationship between product crystal points and ash content, resilience, and filter permeability, shortening product evaluation time. A preliminary judgment of the performance of lithium-ion battery separator material can be made during the preparation of the lithium-ion battery rigid elastic separator, greatly improving evaluation efficiency. The defect judgment criteria are classified as follows:

[0010] Superior grade: Total number of defects less than 600 per 100m 2 Furthermore, the total number of small crystals and small black dots is ≤300;

[0011] Qualified products: Grade 1 qualified products: 600 < total quantity ≤ 1000 pieces / 100m 2 And 300 / 100m 2 <Total number of small crystals and black dots ≤ 500 / 100m 2 Level 2 qualified products: 1000 < total quantity ≤ 2000 pieces / 100m 2 And 500 / 100m 2 <Total number of small crystals and black dots ≤ 1000 per 100m 2 Level 3 qualified products: 2000 < total quantity ≤ 3000 pieces / 100m 2 And 1000 / 100m 2 <Total number of small crystals and black dots ≤ 1500 / 100m 2 Non-conforming products: Total number > 3000 pieces / 100m 2 Furthermore, the total number of small crystals and small black dots is greater than 1500 per 100m. 2 .

[0012] It can be seen that this method includes the number of black dots, which is not allowed in optical protective films. Furthermore, it does not specify the crystal size, only the quantity requirement, which cannot meet the requirements of optical protective films.

[0013] GB / T11115-2009 specifies only fisheyes and streaks as the appearance criteria for LDPE film materials. Fisheyes are spherical lumps formed by transparent or translucent resin in the film, with a size range of 0.3mm-2mm and a magnification of 0.1mm. Streaks are linear, hammer-shaped, and continuous fisheye-like protrusions in the film, with a size range of ≥1.0cm and a ruler accuracy of 1.0cm. Different raw materials have quantitative indicators, and materials exceeding the standards are considered unqualified.

[0014] It can be seen that the existing crystal point evaluation can enable the timely handling of unqualified products, but the size range and accuracy cannot meet the quality requirements of LDPE raw materials for electronic protective films.

[0015] To date, publicly reported existing technologies regarding electronic protective films mainly focus on improvements in raw material production processes, coating, and formulation. While some testing involves the range of crystal point sizes, the precision of these tests is insufficient to meet the raw material requirements of electronic protective films. Furthermore, merely meeting the crystal point specifications may result in insufficient melt strength, affecting film stability during blown film formation. Currently, the suitability of electronic protective film raw materials produced by manufacturers can only be determined through application by downstream users. Therefore, the evaluation process is lengthy, and poor performance can lead to significant losses for both manufacturers and downstream users. Therefore, a simple and rapid evaluation method for low-density polyethylene (LDPE) electronic protective film raw materials is urgently needed to facilitate resin quality assessment by production units. Summary of the Invention

[0016] The purpose of this invention is to provide an evaluation method for low-density polyethylene electronic protective film raw materials, which can accurately, quickly and conveniently evaluate the quality of optical protective film resin.

[0017] To achieve the above objectives, the present invention provides a method for evaluating low-density polyethylene electronic protective film raw materials, comprising the following steps:

[0018] (1) Blow low-density polyethylene electronic protective film raw material into a film with a thickness of 0.01 to 0.08 mm;

[0019] (2) The thin film is irradiated by a light beam generated by a constant, continuous, and adjustable light source. The light beams that are transmitted and blocked are received by an optical camera. The crystal particle detector detects the size and number of crystal particles with a size greater than or equal to 0.02 mm at a resolution greater than or equal to 20 μm. When there are crystal particles with a diameter ≥ 1.0 mm, or a number of crystal particles > 5 / m 2 If the product is unqualified, it is considered a substandard product; otherwise, it is considered a preliminarily qualified product.

[0020] (3) The number of crystal points and the melt strength of the LDPE resin raw material of the obtained preliminary qualified product are calculated. The relationship between the two satisfies the following formula and can be used as a raw material for optical protective films:

[0021] y≤20.29478x 2 +26.25208x-0.3116

[0022] Where x is the melt strength, calculated in Newtons based on a test at 190°C, with a value ranging from 0.07 to 0.18.

[0023] y represents the number of crystal points, expressed as the total number of crystal points per square meter of film.

[0024] The evaluation method for the low-density polyethylene electronic protective film raw material of the present invention has a melt strength value of 0.08 to 0.15.

[0025] The melt strength is measured using a direct measurement method known in the art. This method is common knowledge in the field. Wu Chunshuang described the direct measurement method of polyethylene melt strength in "Rheological Characterization of Long-Chain Branched Materials for PERT Pipes" (Shanghai Plastics, 2017, 177(1):31-36) and "Test Method and Influencing Factors of Polyethylene Melt Strength" (Shanghai Plastics, 2015, (3):55-60), CN201180013377.5: Method for Preparing Polyethylene with High Melt Strength. The melt strength testing conditions recommended in this invention are as follows: testing is performed using a Goettfert RT-2000 melt tensile rheometer at a temperature of 190℃, capillary orifice aspect ratio of any one of 20 / 2, 10 / 1, 20 / 1, or 30 / 1 (preferably 20 / 2), and shear rate of 45s. -1 The traction roller spacing is 0.4mm to 1mm, preferably 0.5mm to 0.7mm, and the traction acceleration is 6mm / s². 2 .

[0026] The method described in step (2) is a well-known technique in the field. For example, the method of detecting the impurity content of cross-linkable polyethylene insulation materials YJ-35 and YJG-35 can be used, as specified in JB / T1043 7-2004 "Cross-linkable polyethylene insulation materials for wires and cables". This method counts the crystal points on the sheet. There are also online systems for counting crystal points on thin films. For example, the SMASH roll system of the German ISRA company is a powerful tool for finding defects on uniform and continuous roll products. This application can perform crystal point detection if the sample preparation meets the requirements of thickness in step (1) and resolution in step (2).

[0027] The evaluation method for low-density polyethylene electronic protective film raw materials described in this invention has a film thickness of 0.02 to 0.06 mm.

[0028] In the evaluation method for low-density polyethylene electronic protective film raw materials described in this invention, the number of crystal points in step (3) is the average value of 3 to 5 parallel tests on the same film. Using this average value can effectively eliminate errors.

[0029] The evaluation method for the low-density polyethylene electronic protective film raw material of the present invention specifies that the melt flow rate of the low-density polyethylene electronic protective film raw material is 1.5 g / 10 min to 5.5 g / 10 min; preferably 2.0 g / 10 min to 5.0 g / 10 min. The melt flow rate is tested according to GB / T3682-2000.

[0030] The evaluation method for low-density polyethylene (LDPE) electronic protective film raw materials of this invention refers to granular materials that are free of powder, black particles, and / or yellow particles. Before being blown into a film, the appearance of the LDPE electronic protective film raw material granules is visually inspected. Only raw materials free of powder, black particles, and / or yellow particles can be blown into a film and subjected to subsequent testing; raw materials containing powder, black particles, and / or yellow particles are judged to be unqualified.

[0031] In the evaluation method for the low-density polyethylene electronic protective film raw material of the present invention, step (2) involves statistically analyzing the number of crystal points with sizes ranging from 0.02 to 0.1 mm, 0.1 to 0.2 mm, 0.2 to 0.3 mm, 0.3 to 0.4 mm, 0.4 to 0.5 mm, 0.5 to 0.6 mm, 0.6 to 0.7 mm, 0.7 to 0.8 mm, 0.8 to 0.9 mm, 0.9 to 1.0 mm, and ≥1.0 mm. Since electronic protective films have high requirements for film appearance, fewer crystal points are preferable. Because they are low-viscosity, given the same number of crystal points, smaller crystal point sizes are better, as they have less impact on the protected object.

[0032] The evaluation method for low-density polyethylene electronic protective film raw materials of the present invention involves blowing low-density polyethylene film using a blown film machine. The blown film machine includes an extrusion main unit and a traction auxiliary unit. The processing temperature of the extrusion main unit is 150-190℃, and the rotation speed is 20-60 rpm. The traction speed of the traction auxiliary unit is 8-40 m / min.

[0033] The evaluation method for low-density polyethylene electronic protective film raw materials described in this invention uses an extruder with a processing temperature of 160℃~180℃ and a rotation speed of 25~45rpm, and a traction speed of 9.0~30m / min.

[0034] The evaluation method for low-density polyethylene electronic protective film raw materials of the present invention uses a single-screw extruder or a twin-screw extruder as the extrusion host.

[0035] The evaluation method for low-density polyethylene electronic protective film raw materials described in this invention includes a blown film machine equipped with a winding device. The winding device ensures that the blown film can be stretched without wrinkles and is not deformed, as both stretching deformation and wrinkles will lead to inaccurate crystal point test results. This technique is common knowledge in the field and is referred to as effective synergy. Specifically, the blown film process involves plasticizing and extruding the low-density polyethylene electronic protective film raw material to form a ring tube, blowing it into shape, and then cooling, traction, and winding it to blow the raw material into a film with a thickness of 0.01–0.08 mm. More specifically, a blown film machine includes an extruder, a traction auxiliary machine, an air ring and die head, an air compressor, a distribution box blower, and a winding device. The blown film process is a flat extrusion top-blowing method, meaning the extruder head's discharge direction is perpendicular to the extruder, the extruded annular tube faces upwards, and after being pulled a certain distance by the traction auxiliary machine, it is clamped by a herringbone plate. The extruded annular tube is inflated into a bubble tube by compressed air introduced from the bottom. The transverse dimension is controlled by the amount of compressed air, and the longitudinal dimension is controlled by the traction speed. After the bubble tube is cooled and shaped, a blown film is obtained. This process, including traction and inflation, more closely resembles the processing technology used by users, allowing for a more accurate evaluation of the raw materials.

[0036] A crystal point testing device consists of a light source, an optical camera, and a crystal point particle detector. This device can be a commercially available one or assembled independently. It only needs to be installed after the blown film machine to test the film, preferably between the blown film machine and the winding machine.

[0037] The beneficial effects of this invention are:

[0038] This invention discloses an evaluation method for low-density polyethylene electronic protective film raw materials. By controlling the sample processing method and crystal point testing conditions, and establishing the relationship between the crystal point of the resin blown film and the melt strength, it can accurately and quickly determine whether the raw material is qualified. Compared with existing technologies, it is especially faster and more accurate than existing post-testing methods. When using the preferred blown film temperature and film thickness, the crystal point test results may be more accurate and the effect may be better due to the properties of the raw material and the surface condition of the film. Detailed Implementation

[0039] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0040] Raw material source:

[0041] Imported LDPE electronic protective film material: melt flow rate 2.08g / 10min, commercially available product.

[0042] Special material for electronic protective films from a PetroChina company:

[0043] Trial production sample 1, melt mass flow rate 4.10 g / 10 min;

[0044] Sample 2 of the trial production had a melt flow rate of 2.21 g / 10 min.

[0045] Trial production sample 3, melt mass flow rate 3.81 g / 10 min;

[0046] The trial production sample 4 had a melt flow rate of 3.62 g / 10 min.

[0047] The trial production sample 5 had a melt flow rate of 2.15 g / 10 min.

[0048] The melt flow rate of the trial production sample 6 was 2.09 g / 10 min.

[0049] The trial production sample 7 had a melt flow rate of 1.83 g / 10 min.

[0050] Analysis method:

[0051] Melt mass flow rate: MELTVIS type from CEAST, Italy.

[0052] Melt strength: Tested using a Goettfert RT-2000 melt tensile rheometer at a temperature of 190℃.

[0053] Film blowing machine: COLLIN E45P film blowing machine from Germany.

[0054] Crystal points: Detected using the SMASH crystal point detector from ISRA GmbH, Germany.

[0055] Example 1

[0056] The pilot production sample 1 was blown into a film at a die head temperature of 170℃ using a blown film machine, with a blow-up ratio of 2.0, a rotation speed of 28 rpm, a traction speed of 8.5 m / min, and a film thickness of 20 μm. A crystal point detector was used to measure 200 μm of the film at a resolution of 20 μm. 2 The number of crystal points on the sample was measured in parallel four times, and the average value was taken. The results are shown in Table 1.

[0057] Table 1

[0058]

[0059] The melt strength test result of the trial production sample 1 was 0.081 N, according to formula 20.29478x 2 The calculation result of +26.25208x - 0.3116 is 1.95, and the crystal point test result is 1.80, which means it meets the condition y ≤ 20.29478x. 2 The result of +26.25208x-0.3116 indicates that the product is qualified. It has been applied in electronic protective film manufacturers, and the results show that the blown film process is stable and can meet the requirements for use in electronic protective films.

[0060] Example 2

[0061] The pilot production sample 2 was blown into a film at a blown film machine head temperature of 150℃, a blow-up ratio of 2.0, a rotation speed of 30 rpm, a traction speed of 9.0 m / min, and a film thickness of 30 μm. A crystal point detector was used to measure 200 μm of the film at a resolution of 20 μm. 2 The number of crystal points on the sample was measured in parallel four times, and the average value was taken. The results are shown in Table 2.

[0062] Table 2

[0063]

[0064] The melt strength test result of the trial production sample 2 was 0.12 N, according to formula 20.29478x 2 The calculation result of +26.25208x - 0.3116 is 3.13, and the crystal point test result is 3.0, which means it meets the condition y ≤ 20.29478x. 2 The result of +26.25208x-0.3116 indicates that the product is qualified. It has been applied in electronic protective film manufacturers, and the results show that the blown film process is stable and can meet the requirements for use in electronic protective films.

[0065] Example 3

[0066] The pilot production sample 3 was blown into a film at a blown film machine head temperature of 160℃, a blow-up ratio of 2.0, a rotation speed of 30 rpm, a traction speed of 9.4 m / min, and a film thickness of 30 μm. A crystal point detector was used to measure 200 μm of the film at a resolution of 20 μm. 2 The number of crystal points on the sample was measured in parallel four times, and the results are shown in Table 3.

[0067] Table 3

[0068]

[0069] The melt strength test result of the trial production sample 3 was 0.101 N, according to formula 20.29478x 2 The calculation result of +26.25208x - 0.3116 is 2.55, and the crystal point test result is 2.50, which means it meets the condition y ≤ 20.29478x. 2 The result of +26.25208x-0.3116 indicates that the product is qualified. It has been applied in electronic protective film manufacturers, and the results show that the blown film process is stable and can meet the requirements for use in electronic protective films.

[0070] Example 4

[0071] The pilot production sample 4 was blown into a film at a die head temperature of 160℃, a blow-up ratio of 2.5, a rotation speed of 39 rpm, a traction speed of 22 m / min, and a film thickness of 20 μm. A crystal point detector was used to measure 200 μm of the film at a resolution of 20 μm. 2 The number of crystal points on the sample was measured in parallel four times, and the average value was taken. The results are shown in Table 4.

[0072] Table 4

[0073]

[0074]

[0075] The melt strength test result of trial production sample 4 was 0.112 N, according to formula 20.29478x 2The calculation result of +26.25208x - 0.3116 is 2.88, and the crystal point test result is 2.20, which means it meets the condition y ≤ 20.29478x. 2 +26.25208x-0.3116 indicates the product is qualified. Its application at the electronic protective film manufacturer demonstrates that the blown film process is stable and meets the requirements for electronic protective film use.

[0076] Example 5

[0077] The pilot production sample 5 was blown into a film at a blown film machine head temperature of 180℃, a blow-up ratio of 2.5, a rotation speed of 39 rpm, a traction speed of 20 m / min, and a film thickness of 30 μm. A crystal point detector was used to measure 200 μm of the film at a resolution of 20 μm. 2 The number of crystal points on the sample was measured in parallel four times, and the results are shown in Table 5.

[0078] Table 5

[0079]

[0080]

[0081] The melt strength test result of trial production sample 5 was 0.124 N, according to formula 20.29478x 2 The calculation result of +26.25208x - 0.3116 is 3.26, and the crystal point test result is 3.1, which means it meets the condition y ≤ 20.29478x. 2 The result of +26.25208x-0.3116 indicates that the product is qualified. It has been applied in electronic protective film manufacturers, and the results show that the blown film process is stable and can meet the requirements for use in electronic protective films.

[0082] Example 6

[0083] Imported electronic protective film material was blown into a thin film at a blown film machine head temperature of 160℃, with a blow-up ratio of 2.0, a rotation speed of 30 rpm, a traction speed of 8.9 m / min, and a film thickness of 30 μm. A crystal point detector was used to measure a 200 μm film at a resolution of 20 μm. 2 The number of crystal points on the sample was measured in parallel four times, and the results are shown in Table 6.

[0084] Table 6

[0085]

[0086] The melt strength test result of the electronic protective film raw material was 0.132N, according to formula 20.29478x 2 The calculation result of +26.25208x - 0.3116 is 3.5, and the crystal point test result is 2.9, which means it meets the condition y ≤ 20.29478x.2 The result of +26.25208x-0.3116 indicates that the product is qualified. It has been applied in electronic protective film manufacturers, and the results show that the blown film process is stable and can meet the requirements for use in electronic protective films.

[0087] Example 7

[0088] The pilot production sample 6 was blown into a film at a die head temperature of 155℃ using a blown film extrusion machine, with a blow-up ratio of 2.0, a rotation speed of 25 rpm, a traction speed of 14.8 m / min, and a film thickness of 15 μm. A crystal point detector was used to measure 200 μm of the film at a resolution of 20 μm. 2 The number of crystal points on the sample was measured in parallel four times, and the results are shown in Table 7.

[0089] Table 7

[0090]

[0091] The melt strength test result of the trial production sample 6 was 0.130 N, according to the formula 20.29478x 2 The calculation result of +26.25208x - 0.3116 is 3.44, and the crystal point test result is 2.78, which means it meets the condition y ≤ 20.29478x. 2 The result of +26.25208x-0.3116 indicates that the product is qualified. It has been applied in electronic protective film manufacturers, and the results show that the blown film process is stable and can meet the requirements for use in electronic protective films.

[0092] Example 8

[0093] The pilot production sample 7 was blown into a film at a die head temperature of 175℃ using a blown film machine, with a blow-up ratio of 1.5, a rotation speed of 30 rpm, a traction speed of 9.0 m / min, and a film thickness of 30 μm. A crystal point detector was used to measure 200 μm of the film at a resolution of 20 μm. 2 The number of crystal points on the sample was measured in parallel four times, and the results are shown in Table 8.

[0094] Table 8

[0095]

[0096] The melt strength test result of the trial production sample 7 was 0.143 N, according to the formula 20.29478x 2 The calculated value of +26.25208x - 0.3116 is 3.86, while the crystal point test result is 4.2, which does not meet the requirement of y ≤ 20.29478x. 2 The result of +26.25208x-0.3116 indicates that the product is substandard. When applied to the electronic protective film manufacturer, the results show that the number of crystal points varies greatly and cannot meet the requirements for use in electronic protective films.

[0097] Comparative Example 1

[0098] The pilot production sample 7 was blown into a film at a blown film machine head temperature of 175℃, with a blow-up ratio of 1.5, a rotation speed of 30 rpm, a traction speed of 9.0 m / min, and a film thickness of 30 μm. According to the crystal point range specified in CN105922689A, a crystal point detector was used to measure 200 μm of the film at a resolution of 20 μm. 2 The number of crystal points on the sample was measured in parallel four times, and the average value was taken. The results are shown in Table 9.

[0099] Table 9

[0100] Crystal point diameter index 1st time 2nd time 3rd 4th <![CDATA[Test value, per m 2 > >2mm none 0 0 0 0 0 (0.8-2)mm none 0 0 0 0 0 (0.6-0.8)mm ≤1 0.15 0.11 0.1 0.07 0.11 (0.2-0.6)mm ≤5 0.71 0.42 0.33 0.48 0.49

[0101] The test was conducted within the specified range and met the required specifications. However, as can be seen from Example 8, it did not meet the manufacturer's requirements because many small crystal points smaller than 0.2 mm were ignored.

[0102] Comparative Example 2

[0103] For pilot production sample 7, a film was blown into shape at a blown film machine head temperature of 175℃, a blow-up ratio of 1.5, a rotation speed of 30 rpm, a traction speed of 9.0 m / min, and a film thickness of 30 μm. Crystal point detection was performed at a resolution of 20 μm, and statistical analysis was conducted according to the crystal point grading method in CN112710669A. Four parallel tests were performed, and the average value was taken. The results are shown in Table 10.

[0104] Table 10

[0105]

[0106] According to the statistical method of CN112710669A, the result can be judged as a superior grade product. However, as can be seen from Example 8, it cannot meet the manufacturer's requirements because the crystal point requirement is relatively low and cannot meet the requirements of electronic protective film.

[0107] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for evaluating low-density polyethylene electronic protective film raw materials, characterized in that, Includes the following steps: (1) Blow low-density polyethylene electronic protective film raw material into a film with a thickness of 0.01 to 0.08 mm; (2) The film is irradiated by the light beam generated by constant, continuous and controllable light source, and the light beam is received by the optical camera. The crystal point particle detector detects the size and number of crystal point particles with a size greater than or equal to 0.02 mm under the condition that the resolution is greater than or equal to 20 um. When the diameter of the crystal point particle is greater than or equal to 1.0 mm, or the number of crystal points is greater than 5 / m 2 , the raw material is unqualified product; otherwise, it is a preliminary qualified product; (3) The number of crystal points and the melt strength of the low-density polyethylene electronic protective film raw material of the obtained preliminary qualified product are calculated. The relationship between the two satisfies the following formula and can be used for electronic protective film raw materials: y≤20.29478x 2 +26.25208x-0.3116 Where x is the melt strength, calculated in Newtons based on a test at 190°C, with a value ranging from 0.07 to 0.

18. y represents the number of crystal points, expressed as the total number of crystal points per square meter of film.

2. The evaluation method for low-density polyethylene electronic protective film raw materials according to claim 1, characterized in that, The melt strength value is 0.08 to 0.

15.

3. The evaluation method for low-density polyethylene electronic protective film raw materials according to claim 1, characterized in that, The film thickness is 0.02 to 0.06 mm.

4. The evaluation method for low-density polyethylene electronic protective film raw materials according to claim 1, characterized in that, The number of crystal points in step (3) is the average value of 3 to 5 parallel tests on the same thin film.

5. The evaluation method for low-density polyethylene electronic protective film raw materials according to claim 1, characterized in that, The melt flow rate of the low-density polyethylene electronic protective film raw material is 1.5 g / 10 min to 5.5 g / 10 min.

6. The evaluation method for low-density polyethylene electronic protective film raw materials according to claim 1, characterized in that, The melt flow rate of the low-density polyethylene electronic protective film raw material is 2.0 g / 10 min to 5.0 g / 10 min.

7. The evaluation method for low-density polyethylene electronic protective film raw materials according to claim 1, characterized in that, The raw material for the low-density polyethylene electronic protective film is a granular material with no powder, black particles, and / or yellow particles in appearance.

8. The evaluation method for low-density polyethylene electronic protective film raw materials according to claim 1, characterized in that, In step (2), the number of crystal points with sizes ranging from 0.02 to 0.1 mm, 0.1 to 0.2 mm, 0.2 to 0.3 mm, 0.3 to 0.4 mm, 0.4 to 0.5 mm, 0.5 to 0.6 mm, 0.6 to 0.7 mm, 0.7 to 0.8 mm, 0.8 to 0.9 mm, 0.9 to 1.0 mm, and ≥1.0 mm are counted respectively.

9. The evaluation method for low-density polyethylene electronic protective film raw materials according to claim 1, characterized in that, Low-density polyethylene film is blown using a blown film machine, which includes an extrusion main unit and a traction auxiliary unit. The processing temperature of the extrusion main unit is 150-190℃ and the rotation speed is 20-60 rpm. The traction speed of the traction auxiliary unit is 8-40 m / min.

10. The evaluation method for low-density polyethylene electronic protective film raw materials according to claim 9, characterized in that, The processing temperature of the extrusion main unit is 160℃~180℃, the rotation speed is 25~45rpm, and the traction speed of the traction auxiliary machine is 9.0~30m / min.

11. The evaluation method for low-density polyethylene electronic protective film raw materials according to claim 9, characterized in that, The extrusion machine is a single-screw extruder or a twin-screw extruder, and the blown film machine is equipped with a winding device.

Images