Methods for eliminating surface texture defects in MCA flame-retardant nylon molded products and molded products

Abstract

This invention discloses a method for eliminating surface texture defects in MCA flame-retardant nylon molded parts. The molded parts are obtained by injection molding of MCA flame-retardant nylon material without an external mold temperature controller. The MCA flame-retardant nylon material comprises the following raw material components by weight: 40-65 parts nylon resin, 5-13 parts MCA flame retardant, 10-40 parts reinforcing filler, and 0.5-3 parts other additives; wherein the nylon resin is PA6 resin with a relative viscosity of 2.4-3.2. This invention, by constructing a PA6 resin system with a specific viscosity as the matrix resin of the MCA flame-retardant nylon material, endows the MCA flame-retardant nylon material with good injection mold texture replication ability. When injection molding textured parts, a good appearance part without surface texture defects can be obtained without an external mold temperature controller, which saves energy and reduces consumption, and saves plastic part manufacturers the cost of purchasing mold temperature controllers and the water and electricity costs for providing the corresponding mold temperature; it abandons the traditional solution of sacrificing the injection molding production efficiency of molded parts in exchange for good part appearance quality.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a method and molded product for eliminating surface texture defects in MCA flame-retardant nylon molded products. Background Technology

[0002] Halogen-free flame retardant melamine cyanurate (MCA), due to its high nitrogen content, decomposes upon heating to produce non-flammable gases such as NH3, H2O, N2, CO2, and H2NCN. These gases have endothermic, cooling, and diluting effects on flammable gases and oxygen concentrations, making it commonly used as a flame retardant modifier for thermoplastic resins, particularly suitable for flame-retardant nylon systems. Furthermore, because MCA flame retardants are widely available, they offer higher cost-effectiveness compared to traditional bromine-antimony and organophosphorus flame retardants. Therefore, in the low-voltage electrical appliance industry, MCA flame-retardant nylon materials are widely used to manufacture electrical equipment housings, such as miniature circuit breaker (MCB) housings and socket housings.

[0003] Considering both product appearance quality and injection molding efficiency, current plastic MCB housings are not glossy but designed with a textured, matte finish. This textured surface not only avoids the aesthetic drawbacks of glossy surfaces, such as attracting dust or fingerprints, but also improves injection molding performance. For example, it allows less air between the product surface and the mold cavity surface during injection molding, preventing vacuum adhesion and facilitating subsequent demolding; it also improves ejection stability, avoiding shadows caused by sliders or angled ejectors, thus increasing the yield rate of injection molded products. Taking MCB housings as an example, for reasons of production efficiency and processing costs, circuit breaker manufacturers and their subcontractors typically do not use external mold temperature controllers when using MCA flame-retardant nylon for injection molding of MCB housings. If a mold temperature controller is used, its water circuit is directly connected to cooling water to conduct injection molding at a low mold temperature (below 40°C) to shorten the injection molding cycle and increase production capacity. However, as early as 2017, well-known domestic low-voltage electrical appliance manufacturers such as Chint and Delixi reported that when using MCA flame-retardant nylon material to injection mold MCB housings, large areas of inconsistent color, texture, and reflectivity often appeared on the surface of the housings. This was particularly true for the prominently displayed manufacturer logos, which were furthest from the injection gate during injection molding, making them more prone to inconsistent color and texture. After pad printing, obvious delamination occurred, severely affecting the visual appeal of the MCB housings. To address this, Chint and Delixi, together with several MCA flame-retardant nylon material manufacturers, spent considerable time and effort seeking solutions to overcome this defect. The final solution was to increase the mold temperature to over 60°C to ensure the surface quality of the MCB housings. However, for circuit breaker manufacturers and their subcontractors, this solution not only increased the cost of purchasing mold temperature controllers but also increased water and electricity consumption. Most importantly, increasing the mold temperature would correspondingly extend the product injection molding cycle, reducing the production efficiency of the MCB housings. According to statistics from Chint Group, Delixi Group, and their subcontractors, compared to production modes that do not use external mold temperature controllers or control the mold temperature below 40°C, the average production efficiency of injection molding MCB shell parts produced using the above methods is reduced by nearly 15%.

[0004] For five years, eliminating the texture defects in MCB housings made from MCA flame-retardant nylon injection molding has been achieved at the cost of reduced production efficiency due to increased mold temperatures. As a modified engineering plastics manufacturer, if a solution could be developed from the perspective of MCB housing materials, while ensuring acceptable material costs, through material formulation design to eliminate the inconsistent color, texture, and reflectivity defects on the surface of MCB housings produced by injection molding without external mold temperature controllers or at low mold temperatures, it would undoubtedly be highly favored by circuit breaker manufacturers and their subcontractors, possessing significant research and application value.

[0005] For manufacturers and sellers of modified engineering plastics, in today's increasingly homogenized market, even a reduction of just 1-2 seconds in the molding cycle of a particular material can significantly increase downstream customer partnerships, secure more orders, and provide a substantial advantage in market promotion. Therefore, designing material formulations to eliminate surface texture defects in injection-molded products made from MCA flame-retardant nylon materials at low mold temperatures or without external mold temperature controllers is of paramount practical importance. Summary of the Invention

[0006] The purpose of this invention is to address the technical challenge of surface texture defects in injection-molded plastic products made of existing MCA flame-retardant nylon materials, which are prone to occur at low mold temperatures or without an external mold temperature controller. This invention provides a method to eliminate surface texture defects in MCA flame-retardant nylon molded products.

[0007] The above-mentioned objectives of the present invention are achieved through the following technical solutions:

[0008] A method for eliminating surface texture defects in MCA flame-retardant nylon molded articles, wherein the molded articles are injection molded from MCA flame-retardant nylon material without an external mold temperature controller, the MCA flame-retardant nylon material comprising the following raw material components in parts by weight: 40-65 parts of nylon resin, 5-13 parts of MCA flame retardant, 10-40 parts of reinforcing filler and 0.5-3 parts of other additives; wherein the nylon resin is a medium-high viscosity PA6 resin with a relative viscosity of 2.4-3.2.

[0009] In this invention, the relative viscosity test is performed in accordance with GB12006.1-2009, the method for determining the viscosity of polyamide, and the relative viscosity of a nylon solution with a concentration of 10 mg / mL is measured in concentrated sulfuric acid at 25°C with a concentration of 96% ± 0.20% (mass fraction).

[0010] The reinforcing filler is glass fiber or a mixture of glass fiber and powder reinforcing filler.

[0011] Optionally, the MCA flame-retardant nylon material comprises the following raw material components in parts by weight: 40-65 parts of PA6 resin, 5-13 parts of MCA flame retardant, 10-30 parts of glass fiber, and 0.5-3 parts of other additives.

[0012] Optionally, the MCA flame-retardant nylon material comprises the following raw material components in parts by weight: 40-65 parts PA6 resin, 5-13 parts MCA flame retardant, 15-25 parts glass fiber, 10-20 parts powder reinforcing filler, and 0.5-3 parts other additives; wherein the PA6 resin is a blend of two or more PA6 resins with a relative viscosity of 2.4-3.2.

[0013] In the above technical solution, the PA6 resin is a blend of PA6 resin with a relative viscosity of 2.4 and PA6 resin with a relative viscosity of 2.8, and the weight percentage of the PA6 resin with a relative viscosity of 2.4 and the PA6 resin with a relative viscosity of 2.8 is 5:1 to 1:3.

[0014] In the above technical solution, the PA6 resin is a blend of PA6 resin with a relative viscosity of 2.4 and PA6 resin with a relative viscosity of 3.2, and the weight percentage of the PA6 resin with a relative viscosity of 2.4 and the PA6 resin with a relative viscosity of 3.2 is 6:1 to 1:1.

[0015] Preferably, the powder reinforcing filler is selected from one or more of the following: wollastonite, kaolin, mica, talc, clay, bentonite, montmorillonite, titanium dioxide, calcium carbonate, magnesium carbonate, dolomite, calcium sulfate, barium sulfate, glass beads, glass powder, ceramic beads, and ground glass fibers.

[0016] Another object of the present invention is to provide a plastic molded article prepared by the above-described method for eliminating surface texture defects of MCA flame-retardant nylon molded articles.

[0017] In practical applications, the plastic molded product protected by this invention is a circuit breaker housing component, the surface of which is free of texture defects; after pad printing marking is applied to the surface of the circuit breaker housing component, there is no problem of texture delamination.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention uses a PA6 resin system with a specific viscosity as the matrix resin of MCA flame-retardant nylon material, which endows the MCA flame-retardant nylon material with good ability to replicate the texture of injection molds. When injection molding textured parts, no external mold temperature controller is required to obtain parts with good appearance without texture defects. This saves energy and reduces consumption, and also saves plastic parts manufacturers the cost of purchasing mold temperature controllers and the water and electricity costs for providing the corresponding mold temperature. It also abandons the traditional solution of sacrificing the production efficiency of injection molding to obtain good part appearance quality. Attached Figure Description

[0019] Figure 1 This is a real-world image of the surface of the MCB housing part injection molded by the method of Example 1.

[0020] Figure 2 The image shows the surface of the MCB housing part injection molded by the method in Comparative Example 1.

[0021] Figure 3 The image shows the surface of the MCB housing after the markings have been applied, obtained by the methods of Comparative Example 1 and Example 1.

[0022] Figure 4 This is a real-world image of the surface of the MCB housing part injection molded by the method of Example 2.

[0023] Figure 5 This is a real-world image of the surface of the MCB housing part injection molded by the method of Example 3.

[0024] Figure 6 This is a real-world image of the surface of the MCB housing part injection molded by the method of Example 4.

[0025] Figure 7 The image shows the surface of the MCB housing part injection molded by the method in Comparative Example 2.

[0026] Figure 8 This is a real-world image of the surface of the MCB housing part injection molded by the method of Example 5.

[0027] Figure 9 This is a real-world image of the surface of the MCB housing part injection molded by the method of Example 6.

[0028] Figure 10 This is a real-world image of the surface of the MCB housing part injection molded by the method in Comparative Example 3. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. The following embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0030] Evaluation method for leather texture defects in products:

[0031] MCB housing parts with matte texture were injection molded using the methods of the examples and comparative examples. The surface condition of the housing was observed visually to evaluate the texture defects.

[0032] Example 1

[0033] For the first time, MCA flame-retardant nylon material was prepared by premixing 64 parts by weight of PA6 resin (relative viscosity 2.4), 6 parts by weight of MCA flame retardant, 0.5 parts by weight of calcium stearate, and 0.6 parts by weight of antioxidant 1098, and then feeding the mixture into the main feed port of a twin-screw extruder. 30 parts by weight of glass fiber were fed into the side feed port of the twin-screw extruder. The mixture was then melt-blended, extruded, drawn into strands, cooled, and pelletized to obtain the MCA flame-retardant nylon material. The twin-screw extruder had a screw length-to-diameter ratio of 40–48:1, a melt plasticizing temperature of 220℃–265℃, and a screw speed of 220 r / min–400 r / min.

[0034] Then, the prepared MCA flame-retardant nylon material was put into the injection molding machine, and the MCB shell part was injection molded without an external mold temperature controller. At this time, the surface condition of the MCB shell part is shown in the figure. Figure 1 .

[0035] Comparative Example 1

[0036] Compared to Example 1, the relative viscosity of PA6 resin in Comparative Example 1 was 2.0, and everything else was exactly the same as in Example 1. The surface condition of the MCB housing obtained in Comparative Document 1 is shown in [reference needed]. Figure 2 .

[0037] Pad printing marking was performed on the MCB housing parts prepared using the methods of Example 1 and Comparative Example 1. The surface condition of the pad printing area of ​​the MCB housing parts of Comparative Example 1 and Example 1 is shown in the figure. Figure 3 .

[0038] Example 2

[0039] First, MCA flame-retardant nylon material is prepared by premixing 40 parts by weight of PA6 resin (relative viscosity 2.4), 20 parts by weight of PA6 resin (relative viscosity 2.8), 10 parts by weight of MCA flame retardant, 20 parts by weight of glass fiber, 0.5 parts by weight of calcium stearate, and 0.6 parts by weight of antioxidant 245. The mixture is then fed into a twin-screw extruder through the main feed port, and 10 parts by weight of wollastonite is fed into the twin-screw extruder through the side feed port. The process involves melting, blending, extrusion, stranding, cooling, and pelletizing to obtain the MCA flame-retardant nylon material. The twin-screw extruder has a screw length-to-diameter ratio of 40–48:1, a melt plasticizing temperature of 220℃–265℃, and a screw speed of 220 r / min–400 r / min.

[0040] Then, the prepared MCA flame-retardant nylon material was put into the injection molding machine, and the MCB shell part was injection molded without an external mold temperature controller. At this time, the surface condition of the MCB shell part is shown in the figure. Figure 4 .

[0041] Example 3

[0042] First, MCA flame-retardant nylon material is prepared by premixing 54 parts by weight of PA6 resin (relative viscosity 2.8), 11 parts by weight of MCA flame retardant, 5 parts by weight of glass fiber, 0.5 parts by weight of calcium stearate, and 0.6 parts by weight of antioxidant 245. The mixture is then fed into a twin-screw extruder through the main feed port, and 30 parts by weight of wollastonite is fed into the twin-screw extruder through the side feed port. The process involves melting, blending, extrusion, stranding, cooling, and pelletizing to obtain the MCA flame-retardant nylon material. The twin-screw extruder has a screw length-to-diameter ratio of 40–48:1, a melt plasticizing temperature of 220℃–265℃, and a screw speed of 220 r / min–400 r / min.

[0043] Then, the prepared MCA flame-retardant nylon material was put into the injection molding machine, and the MCB shell part was injection molded without an external mold temperature controller. At this time, the surface condition of the MCB shell part is shown in the figure. Figure 5 .

[0044] Example 4

[0045] First, MCA flame-retardant nylon material is prepared by premixing 50 parts by weight of PA6 resin (relative viscosity 2.4), 10 parts by weight of PA6 resin (relative viscosity 3.2), 10 parts by weight of MCA flame retardant, 10 parts by weight of glass fiber, 0.5 parts by weight of lubricant A-C540A, and 0.6 parts by weight of antioxidant 1098. The mixture is then fed into a twin-screw extruder through the main feed port, and 20 parts by weight of glass powder is fed into the twin-screw extruder through the side feed port. The process involves melting, blending, extrusion, stranding, cooling, and pelletizing to obtain the MCA flame-retardant nylon material. The twin-screw extruder has a screw length-to-diameter ratio of 40–48:1, a melt plasticizing temperature of 220℃–265℃, and a screw speed of 220 r / min–400 r / min.

[0046] Then, the prepared MCA flame-retardant nylon material was put into the injection molding machine, and the MCB shell part was injection molded without an external mold temperature controller. At this time, the surface condition of the MCB shell part is shown in the figure. Figure 6 .

[0047] Comparative Example 2

[0048] Compared to Example 4, the PA6 resin in Comparative Example 2 was a single PA6 resin with a relative viscosity of 2.3. A mold temperature of 40°C was used when injection molding the MCB housing part. Everything else was exactly the same as in Example 4. The surface condition of the MCB housing part obtained in Comparative Example 2 is shown in [reference needed]. Figure 7 .

[0049] Example 5

[0050] First, MCA flame-retardant nylon material was prepared by premixing 21 parts by weight of PA6 resin (relative viscosity 2.4), 42 parts by weight of PA6 resin (relative viscosity 2.8), 7 parts by weight of MCA flame retardant, 15 parts by weight of glass fiber, 0.5 parts by weight of lubricant A-C540A, and 0.6 parts by weight of antioxidant 1098. The mixture was then fed into a twin-screw extruder through the main feed port, and 20 parts by weight of glass powder were fed into the twin-screw extruder through the side feed port. The process involved melting, blending, extrusion, stranding, cooling, and pelletizing to obtain the MCA flame-retardant nylon material. The twin-screw extruder had a screw length-to-diameter ratio of 40–48:1, a melt plasticizing temperature of 220℃–265℃, and a screw speed of 220 r / min–400 r / min.

[0051] Then, the prepared MCA flame-retardant nylon material was put into the injection molding machine, and the MCB shell part was injection molded without an external mold temperature controller. At this time, the surface condition of the MCB shell part is shown in the figure. Figure 8 .

[0052] Example 6

[0053] First, MCA flame-retardant nylon material is prepared by premixing 30 parts by weight of PA6 resin (relative viscosity 2.4), 30 parts by weight of PA6 resin (relative viscosity 2.8), 10 parts by weight of MCA flame retardant, 20 parts by weight of glass fiber, 0.5 parts by weight of lubricant A-C540A, 0.6 parts by weight of antioxidant 1098, and 1 part by weight of black masterbatch. The mixture is then fed into a twin-screw extruder through the main feed port, and 10 parts by weight of glass powder is fed into the twin-screw extruder through the side feed port. The process involves melting, blending, extrusion, stranding, cooling, and pelletizing to obtain the MCA flame-retardant nylon material. The twin-screw extruder has a screw length-to-diameter ratio of 40–48:1, a melt plasticizing temperature of 220℃–265℃, and a screw speed of 220 r / min–400 r / min.

[0054] Then, the prepared MCA flame-retardant nylon material was put into the injection molding machine, and the MCB shell part was injection molded without an external mold temperature controller. At this time, the surface condition of the MCB shell part is shown in the figure. Figure 9 .

[0055] Comparative Example 3

[0056] Compared to Example 6, the PA6 resin in Comparative Example 3 was a single PA6 resin with a relative viscosity of 2.0. A mold temperature of 40°C was used when injection molding the MCB housing part; otherwise, it was identical to Example 6. The surface condition of the MCB housing part obtained in Comparative Example 3 is shown in [reference needed]. Figure 10 .

[0057] from Figure 1 , Figure 4 , Figure 5 , Figure 6 , Figure 8 and Figure 9 It is evident that when using PA6 resin with a higher viscosity (relative viscosity value of 2.4~3.2) as the matrix resin in the preparation of MCA flame-retardant nylon materials, even without an external mold temperature controller, the surface color, texture, and reflectivity of the injection-molded MCB shell parts are consistent, with no skin texture defects; while when using PA6 resin with a relative viscosity value lower than 2.4 as the matrix resin (such as...), the surface color, texture, and reflectivity of the injection-molded MCB shell parts are consistent, with no skin texture defects. Figure 2 , Figure 7 , Figure 10 When preparing MCA flame-retardant nylon material and using it for injection molding MCB shell parts, obvious watermark-like uneven color texture defects appeared on the surface of the injection-molded MCB shell parts, under conditions of no external mold temperature controller or a mold temperature set to 40℃. This demonstrates that preparing MCA flame-retardant PA6 material by constructing a PA6 resin system with a specific viscosity can indeed eliminate the surface texture defects of MCA flame-retardant PA6 material molded parts.

[0058] from Figure 3 It is evident that, after the MCB housing obtained using the technical solution of this application is marked with pad printing, no delamination occurs on the surface of the pad-printed area. Figure 3 b), while the MCB shell parts made of MCA flame-retardant nylon material prepared with PA6 resin with a relative viscosity value of less than 2.4 as the matrix resin exhibited obvious watermark-like texture defects in the pad printing area before pad printing, resulting in obvious delamination after pad printing. Figure 3 a).

[0059] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for eliminating surface texture defects in MCA flame-retardant nylon molded products, characterized in that, The molded article is obtained by injection molding of MCA flame-retardant nylon material without an external mold temperature controller. The MCA flame-retardant nylon material comprises the following raw material components in parts by weight: 40-65 parts nylon resin, 5-13 parts MCA flame retardant, 10-40 parts reinforcing filler, and 0.5-3 parts other additives; wherein the nylon resin is PA6 resin with a relative viscosity of 2.4-3.2, and the PA6 resin is a blend of two or more PA6 resins with a relative viscosity of 2.4-3.

2.

2. The method for eliminating surface texture defects in MCA flame-retardant nylon molded products according to claim 1, characterized in that, The reinforcing filler is glass fiber or a mixture of glass fiber and powder reinforcing filler.

3. The method for eliminating surface texture defects in MCA flame-retardant nylon molded products according to claim 2, characterized in that, The MCA flame-retardant nylon material comprises the following raw material components in parts by weight: 40-65 parts PA6 resin, 5-13 parts MCA flame retardant, 10-30 parts glass fiber, and 0.5-3 parts other additives.

4. The method for eliminating surface texture defects in MCA flame-retardant nylon molded products according to claim 2, characterized in that, The MCA flame-retardant nylon material comprises the following raw material components in parts by weight: 40-65 parts PA6 resin, 5-13 parts MCA flame retardant, 15-25 parts glass fiber, 10-20 parts powder reinforcing filler, and 0.5-3 parts other additives.

5. The method for eliminating surface texture defects in MCA flame-retardant nylon molded products according to claim 4, characterized in that, The PA6 resin is a blend of PA6 resin with a relative viscosity of 2.4 and PA6 resin with a relative viscosity of 2.8, and the weight percentage of the PA6 resin with a relative viscosity of 2.4 and PA6 resin with a relative viscosity of 2.8 is 5:1 to 1:

3.

6. The method for eliminating surface texture defects in MCA flame-retardant nylon molded products according to claim 4, characterized in that, The nylon resin is a blend of PA6 resin with a relative viscosity of 2.4 and PA6 resin with a relative viscosity of 3.2, and the weight percentage of the PA6 resin with a relative viscosity of 2.4 and PA6 resin with a relative viscosity of 3.2 is 6:1 to 1:

1.

7. The method for eliminating surface texture defects in MCA flame-retardant nylon molded products according to any one of claims 4 to 6, characterized in that, The powder reinforcing filler is selected from one or more of the following: wollastonite, kaolin, mica, talc, clay, bentonite, montmorillonite, titanium dioxide, calcium carbonate, magnesium carbonate, dolomite, calcium sulfate, barium sulfate, glass beads, glass powder, ceramic beads, and ground glass fiber.

8. A plastic molded article, characterized in that, The molded article is prepared by the method for eliminating surface texture defects of MCA flame-retardant nylon molded articles as described in any one of claims 1 to 7.

9. The plastic molded article according to claim 8, characterized in that, The plastic molded product is a circuit breaker housing component, and the surface of the circuit breaker housing component is free of texture defects.

10. The plastic molded article according to claim 9, characterized in that, After the circuit breaker housing is marked with pad printing, there is no issue of delamination of the texture.

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