A laser-weldable and ultraviolet markable color polypropylene composite material and a preparation method thereof

Abstract

The application provides a laser-weldable and ultraviolet-markable color polypropylene composite material and a preparation method thereof, and comprises the following components by weight: polypropylene resin: 93.50-99.75 parts; color organic transparent light powder: 0.05-0.50 parts; wherein the color organic transparent light powder has a characteristic absorption peak in the 400-760 nm visible light band so that the polypropylene composite material presents color, and the light transmittance of the polypropylene composite material is greater than 20% for the 980 nm near-infrared band when the thickness is 2 mm; after the polypropylene composite material is marked by ultraviolet laser, a white mark is formed on the surface of the color base, and the contrast of the white mark and the unmarked area is greater than 80%. Through the reasonable proportioning of the components in the formula, clear white marks are formed on the color polypropylene composite material through ultraviolet marking, and excellent laser welding compatibility is simultaneously achieved, so that the ultraviolet marking and laser welding performance of the color polypropylene base material are compatible.

Description

Technical Field

[0001] This invention belongs to the field of polymer material modification technology, and relates to a colored polypropylene composite material that can be laser welded and UV marked, and its preparation method. Background Technology

[0002] Polypropylene (PP) is widely used in various fields such as automobiles, electronics, home appliances, and medical devices due to its advantages such as low density, excellent mechanical properties, good processing fluidity, and low cost. As high-end products continue to have higher requirements for appearance, connection technology, and marking functions, polypropylene materials are gradually replacing metal parts, and higher requirements are being placed on their surface marking, connection assembly, and signal transmission performance.

[0003] Laser marking offers advantages such as non-contact operation, high precision, permanent marking, and no consumables, and has gradually replaced traditional ink printing and heat transfer processes. Among them, ultraviolet lasers, due to their high single-photon energy and small heat-affected zone, are particularly suitable for fine marking of heat-sensitive polymer materials.

[0004] In existing technologies, laser marking on polypropylene is mainly achieved by adding laser marking additives, that is, by incorporating specific absorbents into the polypropylene matrix, such as carbon black, antimony tin oxide, bismuth oxide, mica-coated pigments, etc., so that the material carbonizes, foams or changes color under laser irradiation to form a mark.

[0005] However, existing ultraviolet laser marking technology still cannot achieve the desired effect for forming clear white marks on colored polypropylene. Even with the use of some organic pigments to achieve near-infrared light transmission in colored polypropylene, conventional ultraviolet marking can only form gray or dark characters on the colored substrate, with extremely low contrast to the colored background. This results in a poor ultraviolet marking effect on colored polypropylene substrates, failing to meet the technical requirements of the corresponding devices.

[0006] In addition, based on the applications of polypropylene materials in automotive interior parts, electronic device housings, precision laser-welded components, and high-end plastic products requiring permanent marking, requirements have been placed on its laser welding performance in application scenarios that demand its connection and assembly. Laser transmission welding is a highly efficient method for joining thermoplastic plastics. Its principle involves the upper layer transmitting laser light, while the lower layer absorbs the laser light and melts, thus fusing the two components together. Polypropylene, due to its high transmittance to near-infrared lasers, is an ideal material for laser welding.

[0007] However, there is a conflict in the optical performance requirements of materials for UV marking and laser welding. UV marking requires materials to effectively absorb ultraviolet light to produce a mark, while welding requires materials to maintain sufficient transmittance in the near-infrared band to achieve energy penetration. In particular, after UV marking forms a white mark, the optical properties of the marked area, such as reflectivity and scattering, may change, thus affecting the subsequent welding quality.

[0008] In view of this, developing a polypropylene composite material that can be clearly marked with white on colored substrates, and has stable laser welding performance, stable processing, controllable cost, and can be industrially mass-produced has significant industrial value and application prospects. Summary of the Invention

[0009] The purpose of this invention is to solve the problem in the prior art that it is difficult to form clear white marks on colored polypropylene matrix by UV marking and that UV marking performance is incompatible with laser welding performance. The invention provides a colored polypropylene composite material that can be laser welded and UV marked, and its preparation method.

[0010] To achieve the above objectives, the present invention proposes the following technical solution: Firstly, a colored polypropylene composite material capable of laser welding and UV marking is proposed, specifically comprising the following components in parts by weight: Polypropylene resin: 93.50~99.75 parts; Colored organic translucent powder: 0.05~0.50 parts; The colored organic light-transmitting powder has a characteristic absorption peak in the 400-760 nm visible light band to make the polypropylene composite material appear colored, and the polypropylene composite material has a transmittance of >20% in the 980 nm near-infrared band when the thickness is 2 mm; The polypropylene composite material is marked with a 355 nm ultraviolet laser to form a white mark on the surface of the colored substrate, and the contrast between the white mark and the unmarked area is >80%.

[0011] Furthermore, the colored organic translucent pigment is selected from one or more of dioxazine, phthalocyanine, isoindolineone, and quinacridone organic pigments.

[0012] Furthermore, the colored organic translucent pigment is selected from at least one of CI pigment violet 23, CI pigment red 122, CI pigment blue 15:3, and CI pigment yellow 110.

[0013] Furthermore, after the polypropylene composite material is marked with an ultraviolet laser with a wavelength of 355 nm, a white mark is formed on the surface of the colored substrate, and the contrast between the white mark and the unmarked area is >80%.

[0014] Furthermore, the polypropylene composite material also includes the following components in parts by weight: Additives: 0.2~1.5 parts; The additives are selected from one or more of antioxidants and lubricants, and the antioxidants are 0.1 to 0.5 parts by weight, and the lubricants are 0.1 to 1.0 parts by weight.

[0015] Furthermore, the polypropylene composite material also includes the following components in parts by weight: UV marking functional component: 0~4.5 parts; The ultraviolet marking functional component is composed of nano zinc oxide and porous nano silica.

[0016] Furthermore, based on weight, the nano zinc oxide comprises 0 to 1.5 parts, and the porous nano silica comprises 0 to 3.0 parts.

[0017] Furthermore, the nano zinc oxide has a particle size of 250~350nm, and its median particle size D50≤300 nm.

[0018] Furthermore, the porous nano-silica has an average particle size of 10-50 nm and a specific surface area of ​​300-500 m². 2 / g.

[0019] Secondly, a method for preparing the aforementioned laser-weldable and UV-markable colored polypropylene composite material is proposed, comprising the following steps: S1. Mix polypropylene resin, colored organic transparent powder, additives and UV marking functional components to obtain a uniform mixture; S2. The mixture is added through the main feed port of a twin-screw extruder, melt-blended and extruded at a temperature of 180~230℃, cooled to room temperature with water, and then air-dried and pelletized to obtain polypropylene composite material particles. S3. The polypropylene composite material particles are injection molded or extruded to obtain the polypropylene composite material.

[0020] The beneficial effects of this invention are: This invention addresses the laser welding requirements of colored polypropylene systems by selecting specific colored organic transparent pigments. Utilizing their inherent ultraviolet laser-responsive whitening properties, a clear white permanent mark with a contrast greater than 80% can be formed on a colored substrate without the need for additional ultraviolet marking components. Simultaneously, it ensures that the transmittance of 2 mm thick colored polypropylene products in the 980 nm near-infrared band is greater than 20%, achieving stable laser penetration welding. This ensures that the substrate breaks after welding and stretching, with no cracks or weld detachment at the weld joint, completely solving the problem of compatibility between coloring and welding in traditional polypropylene materials.

[0021] On the one hand, by using a specific ratio of colored organic transparent light powder to other components, the present invention achieves a permanent white mark on a colored polypropylene matrix using ultraviolet laser. The contrast between the marked and unmarked colored matrix is ​​>80%, the marking is clear and the visual effect is significant, overcoming the technical problem of the difficulty in forming light-colored marks on colored polypropylene in the prior art.

[0022] On the other hand, the colored organic light-transmitting powder selected in this invention is dispersed in the polypropylene matrix at the molecular or submicron level. It only absorbs specific wavelengths of light in the 400~760nm visible light band to present a colored appearance, and has no characteristic absorption peaks in the 800~1100nm near-infrared band, ensuring the near-infrared transmittance of the material. This provides a guarantee for laser welding, thereby ensuring that the transmittance of the colored polypropylene composite material to 980nm near-infrared laser is >20% when the thickness is 2 mm, thus guaranteeing the energy penetration depth and welding strength of laser transmission welding.

[0023] On the other hand, the white markings formed on the surface of the colored polypropylene material prepared by the present invention by ultraviolet laser marking are caused by the intrinsic foaming or crystal change of the material, not by surface coating. They have the permanent characteristics of being abrasion resistant and weather resistant. The markings are not easy to fade or fall off during long-term use or in harsh environments, thus meeting the durability requirements of automobiles, home appliances and other fields.

[0024] On the other hand, the colored polypropylene composite material prepared by this invention is prepared using conventional melt blending processes such as twin-screw extrusion, which requires no special equipment, has a wide process window, and exhibits good compatibility among components during processing, without issues such as stratification or precipitation. The material has excellent mechanical properties and processing fluidity, meeting the requirements of high-end products. The preparation process is simple and controllable, compatible with existing industrial production equipment such as twin-screw extrusion and injection molding, enabling large-scale mass production with high efficiency and controllable costs, and possessing extremely high industrial application value. In addition, ultraviolet laser marking can be performed using commercially available ultraviolet laser marking machines, requiring no additional pre- or post-treatment, and offering fast marking speed, high precision, and no consumables.

[0025] In summary, this invention, through the rational proportioning of each component in the formula, enables the formation of clear white marks on colored polypropylene composite materials via ultraviolet marking, while also possessing excellent laser welding compatibility. This achieves compatibility between ultraviolet marking and laser welding performance of colored polypropylene substrates, allowing them to be directly applied to automotive interior parts, electronic device housings, precision laser-welded components, and high-end plastic products requiring permanent marking. This significantly broadens the high-end application range of colored polypropylene materials, enhances product competitiveness, and enables large-scale industrial production.

[0026] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other. Attached Figure Description

[0027] The accompanying drawings are not drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures can be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings. The embodiments in the drawings do not constitute any limitation on the invention. Other drawings can be obtained by those skilled in the art based on the following drawings without inventive effort, wherein: Figure 1 This is a UV marking effect image of the Clariant BG Blue system colored polypropylene composite material prepared in Example 1 of this invention; Figure 2 This is an image showing the UV marking effect of the colored polypropylene composite material of the Bestar RLS permanent violet system prepared in Example 3 of this invention; Figure 3 This is a UV marking effect image of the Superfast Pink 05 system colored polypropylene composite material prepared in Example 4 of this invention; Figure 4 This is a UV marking effect image of the colored polypropylene composite material prepared in Example 6 of this invention, which is a blend of Sudaperm Yellow 2925K, Clariant BG Blue, and SuperfastPink 05. Figure 5 This is a UV marking effect image of the colored polypropylene composite material prepared by the common organic pigment coloring system in Comparative Example 4 of this invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art.

[0029] The terms "comprising" or "including" or similar words used in the patent application specification and claims of this invention mean that the elements or objects preceding "comprising" or "including" encompass the features, integrals, steps, operations, elements and / or components listed after "comprising" or "including", and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0030] Colored polypropylene materials need to simultaneously meet the core requirements of "laser penetration and weldability, and clear and legible UV marking." However, existing technologies still have many unresolved issues, limiting their application in high-end fields. The preparation and application of colored polypropylene materials mainly face the following problems: (1) Poor compatibility between colored appearance and laser welding: Traditional colored polypropylene is mostly colored with inorganic pigments or carbon black. These colorants have a strong absorption capacity for the 800~1100nm near-infrared band light commonly used in laser welding, which makes it impossible for the laser to penetrate the material and achieve stable laser penetration welding. It is difficult to meet the connection requirements of precision components, especially unsuitable for products that require concealed welding, such as automotive interiors and electronic housings.

[0031] (2) The marking effect of polypropylene is limited: the ultraviolet marking effect of colored substrates is poor. Even if some organic pigments are used to achieve near-infrared light transmission of colored polypropylene, conventional ultraviolet marking can only form gray or dark characters on colored substrates. The contrast with the colored background is extremely low, and it is impossible to form a clear, distinguishable, and high-whiteness permanent mark.

[0032] (3) Colored polypropylene marking depends on additional marking components: In the existing technology, colored polypropylene needs to rely on ultraviolet marking components to achieve effective marking. No technical solution has been found that can achieve ultraviolet marking and whitening by specific colored organic pigments themselves, which leads to increased production costs and complicated processing procedures.

[0033] In summary, existing technologies cannot achieve a synergistic balance between clear white marking on colored polypropylene and laser welding performance. They either only enable marking on single-color substrates or fail to balance marking clarity and laser welding performance, thus failing to meet the diverse needs of high-end products and leaving a significant technological gap.

[0034] In view of this, embodiments of the present invention disclose a laser-weldable and UV-markable colored polypropylene composite material, comprising the following components in parts by weight: Polypropylene resin: 93.50~99.75 parts; Colored organic translucent powder: 0.05~0.50 parts; Additives: 0.2~1.5 parts; Among them, the colored organic light-transmitting powder has a characteristic absorption peak in the visible light band of 400~760 nm to make the polypropylene composite material appear colored, and the polypropylene composite material with a thickness of 2 mm has a transmittance of ≥20% in the near-infrared band of 980 nm.

[0035] Specifically, the polypropylene resin is selected from one or a blend of two of homopolymer polypropylene, random copolymer polypropylene, and block copolymer polypropylene. Its melt flow index is measured to be 2–30 g / 10 min at 230 °C and 2.16 kg load according to ISO 1133 standard. Selecting polypropylene resin within this melt flow index range balances the material's mechanical properties and processing fluidity, making it suitable for various molding processes such as injection molding and extrusion, meeting the molding requirements of different products, and also exhibiting good laser welding performance.

[0036] Specifically, the colored organic translucent pigments are selected from one or more of the following organic pigments: dioxazine, phthalocyanine, isoindolineone, and quinacridone.

[0037] The aforementioned colored organic translucent pigments are free of carbon black and high near-infrared absorption inorganic pigments, thus avoiding any impact on near-infrared transmittance. These colored organic translucent pigments absorb only specific wavelengths of light in the 400-760 nm visible light band to produce a colored appearance, and have no characteristic absorption peaks in the 800-1100 nm, specifically 980 nm, near-infrared band, ensuring the material's near-infrared transmittance and providing a guarantee for laser welding. Simultaneously, the aforementioned colored organic translucent pigments possess ultraviolet laser-responsive whitening properties, achieving clear white marking without the need for additional ultraviolet marking components.

[0038] The colored organic translucent pigment is selected from at least one of CI pigment violet 23, CI pigment red 122, CI pigment blue 15:3, and CI pigment yellow 110.

[0039] Preferably, the colored organic translucent pigment is selected from at least one of Bestar RLS Permanent Violet, Superfast Pink 05, Clariant BG Blue, and Sudaperm Yellow 2925K. Wherein: Bestar RLS Permanent Violet is a dioxazine organic pigment, specifically CI Pigment Violet 23, CAS number 6358-30-1.

[0040] Superfast Pink 05 is a quinacridone organic pigment, specifically CI Pigment Red 122, with CAS number 980-26-7.

[0041] Clariant BG Blue is a phthalocyanine organic pigment, specifically CI Pigment Blue 15:3, with CAS number 147-14-8, belonging to the β-type copper phthalocyanine.

[0042] Sudaperm Yellow 2925K is an isoindolinone organic pigment, specifically CI Pigment Yellow 110, with CAS number 106276-80-6.

[0043] In some optional embodiments, the colored organic translucent pigment is composed of any two or more of the following: Bestar RLS Permanent Violet, Superfast Pink05, Clariant BG Blue, and Sudaperm Yellow 2925K. The specific blending ratio can be adjusted according to the color matching requirements.

[0044] This invention utilizes the synergistic effect of photochemical fading and thermal decomposition of the aforementioned colored organic transparent pigments under ultraviolet laser irradiation to achieve compatibility between ultraviolet marking and laser welding. When an ultraviolet laser with a wavelength of 340~360nm irradiates the surface of colored polypropylene, the π electrons of the conjugated color-emitting system in the organic pigment molecules absorb high-energy photons and undergo electronic transitions, leading to irreversible chemical bond breakage or rearrangement in the excited state of the molecules. This reduces the degree of conjugation and significantly decreases the absorption capacity of visible light, resulting in color fading or lightening. Simultaneously, the absorbed laser energy is converted into heat energy, causing localized heating of the pigment molecules and the surrounding polypropylene matrix. The pigment undergoes thermal decomposition to generate colorless or light-colored small molecule products, while the polypropylene matrix undergoes micro-area melting and thermal decomposition to release gas, forming submicron-sized microbubbles. The faded light-colored area and the light scattering generated by the microbubbles superimpose to form a white mark on the colored background. The visual contrast comes from the difference in hue and brightness between the marked area and the unilluminated colored background. No other marking additives are needed. It relies entirely on the ultraviolet laser response characteristics of the colored organic light-transmitting powder itself, and has the advantages of simple formulation and low cost.

[0045] Specifically, the additives are selected from one or more of antioxidants and lubricants; by weight, the antioxidants are 0.1 to 0.5 parts and the lubricants are 0.1 to 1.0 parts.

[0046] Preferably, the antioxidant is a combination of antioxidant 168 and antioxidant 1010, which can effectively delay the aging of materials during processing and use, and improve the service life of the product.

[0047] Preferably, the lubricant is selected from at least one of calcium stearate and polyethylene wax, which can improve the processing fluidity of the material and avoid problems such as sticking to the mold and poor material feeding during processing.

[0048] In some preferred embodiments, a laser-weldable and UV-markable colored polypropylene composite material comprises the following components in parts by weight: Polypropylene resin: 93.50~99.75 parts; Colored organic translucent powder: 0.05~0.50 parts; Additives: 0.2~1.5 parts; UV marking functional component: 0~4.5 parts; The UV marking functional component is composed of nano zinc oxide and porous nano silica.

[0049] Specifically, by weight, nano zinc oxide comprises 0 to 1.5 parts, and porous nano silica comprises 0 to 3.0 parts.

[0050] Among them, the particle size of nano-zinc oxide is 250~350nm, and the median particle size D50 ≤ 300 nm; the particle size of porous nano-silica is 10~50 nm, and the specific surface area is 200~500 m². 2 / g.

[0051] Specifically, by limiting the particle size range of nano zinc oxide, the marking effect is enhanced through a triple effect of "photochromism + micro-foaming + light scattering", that is, a white marking effect. Because nano zinc oxide has a significant impact on the reduction of near-infrared transmittance, its addition amount is strictly controlled. When the addition amount is too large, the near-infrared transmittance of 2 mm thick products will drop significantly to below 40%, making it difficult to guarantee the laser penetration welding performance.

[0052] Specifically, nano zinc oxide enhances the marking effect through a triple synergistic effect: first, photochromism, where a reversible color change occurs under ultraviolet laser excitation to form a latent image; second, microbubbling, where laser energy causes local polypropylene decomposition to produce submicron-sized microbubbles, forming white scattering centers; and third, light scattering, where the high refractive index of nano zinc oxide and the microbubble structure synergistically enhance light scattering, making the reflectivity of the marked area significantly higher than that of the colored substrate, presenting a high-contrast white mark.

[0053] Specifically, porous nano-silica can enhance the marking effect through the synergistic effect of "local carbonization contrast + porous light scattering", that is, the contrast of white marking. Because porous nano-silica has a low packing density, is easy to fluff and difficult to process, and has a high cost, controlling its addition amount within the above range can ensure the UV marking effect while taking into account the convenience of processing and reasonable cost. When its addition amount is within this range, the near-infrared transmittance of 2mm thick products fluctuates by no more than 5%, and has a minimal impact on the near-infrared transmittance.

[0054] Specifically, porous nano-silica enhances the marking effect through a dual synergistic effect: first, it enhances the contrast of local carbonization. The porous structure with a high specific surface area forms local high-temperature hot spots under ultraviolet laser irradiation, which promotes the carbonization of polypropylene micro-areas and forms an outline that contrasts with the white foamed area; second, it enhances light scattering through pores. The difference in refractive index between the mesoporous or hollow structure and the matrix produces strong multiple scattering, which significantly improves the whiteness and coverage of the marking. Thus, in synergy with nano-zinc oxide, it achieves high-contrast white marking under ultraviolet light.

[0055] Specifically, the porous nano-silica is selected from mesoporous silica, hollow silica, or a combination thereof; preferably, the pore size of the mesoporous silica is 10~50 nm, and the hollow silica has a hollow shell structure with a shell thickness of 2~5 nm.

[0056] The above scheme further incorporates nano-zinc oxide and porous nano-silica into the material system based on colored organic transparent light powder, thereby further enhancing the material's ultraviolet absorption efficiency, micro-foaming degree, and light scattering intensity, and synergistically enhancing the laser welding performance of ultraviolet marking performance.

[0057] Specifically, after the polypropylene composite material is marked with an ultraviolet laser with a wavelength of 340~360 nm, a white mark is formed on the surface of the colored substrate, and the contrast between the white mark and the unmarked area is >80%.

[0058] In this invention, the main energy absorber for ultraviolet laser marking of colored polypropylene composite materials is colored organic transparent pigment. To achieve high-contrast white marking, the laser wavelength for ultraviolet marking must meet the following requirements: it should be moderately absorbed by the colored organic transparent pigment to induce molecular fading / decomposition and micro-foaming; it should avoid entering the visible light region, which would cause the marking mechanism to change to thermal carbonization; and it should avoid excessive decomposition of organic colorants or photodegradation of the polypropylene matrix due to excessively short wavelengths.

[0059] Based on the above considerations, the ultraviolet laser wavelength range of this invention is preferably 340~360 nm, and more preferably 355 nm. Within this range, phthalocyanine blue pigment has a characteristic B-band absorption near 340 nm, and other pigments also have ultraviolet absorption tailbands. Laser energy can be efficiently absorbed and converted into fading and foaming effects, forming a high-contrast white mark. If the wavelength is below 340 nm, the organic colorant may undergo irreversible excessive decomposition, affecting the initial color of the matrix; if the wavelength is above 360 ​​nm, excessive absorption of the organic colorant leads to thermal carbonization becoming dominant, resulting in a darker mark color and difficulty in achieving a white effect.

[0060] Preferably, after the polypropylene composite material is marked with an ultraviolet laser with a wavelength of 355 nm, a white mark is formed on the surface of the colored substrate, and the contrast between the white mark and the unmarked area is >80%.

[0061] The aforementioned wavelengths fall within the high-efficiency absorption region of nano-zinc oxide, and industrial lasers are mature and cost-controllable.

[0062] This invention also discloses a method for preparing a laser-weldable and UV-markable colored polypropylene composite material, comprising the following steps: S1. Add 93.50~99.75 parts by weight of polypropylene resin, 0.05~0.50 parts by weight of colored organic transparent powder, and 0.2~1.5 parts by weight of additives to a high-speed mixer and mix. Control the mixing speed to be 800~1200 r / min and the mixing time to be 5~10 min to obtain a uniform mixture.

[0063] S2. The mixture is added through the main feed port of a twin-screw extruder, melt-blended and extruded at a temperature of 180~230℃, cooled to room temperature with water, and then air-dried and pelletized to obtain polypropylene composite material particles. S3. Polypropylene composite material particles are injection molded or extruded to obtain polypropylene composite material.

[0064] In some preferred embodiments, in S1, 93.50-99.75 parts by weight of polypropylene resin, 0.05-0.50 parts by weight of colored organic transparent powder, 0-4.5 parts by weight of UV marking functional component and 0.2-1.5 parts by weight of additives are added to a high-speed mixer and mixed. The mixing speed is controlled at 800-1200 r / min and the mixing time is 5-10 min to obtain a uniform mixture. The remaining preparation steps and related process parameters remain unchanged.

[0065] In a further preferred embodiment, in step S1, 98.0~99.75 parts by weight of polypropylene resin, 0.05~0.50 parts by weight of colored organic transparent powder, 0~4.5 parts by weight of UV marking functional component, and 0.2~1.5 parts by weight of additives are added to a high-speed mixer and mixed. The mixing speed is controlled at 800~1200 r / min and the mixing time is 5~10 min to obtain a uniform mixture. The remaining preparation steps and related process parameters remain unchanged.

[0066] The processing temperature of the twin-screw extruder is set from the feeding section to the die head to 180~230℃. The area between the feeding section and the die head of the twin-screw extruder is divided into at least nine temperature zones. The temperature of zone one is 180~190℃, the temperature of zone two is 190~210℃, the temperature of zones three, four and five is 210~230℃, the temperature of zones six, seven, eight and nine is 210~230℃, and the temperature of the die head is 190~220℃.

[0067] The screw speed of the twin-screw extruder is 300~500 r / min.

[0068] The aforementioned laser-weldable and UV-marked white colored polypropylene composite material can be applied to automotive interior parts, electronic device housings, laser-welded components, UV-marked products, and other fields.

[0069] The following detailed description, with reference to specific embodiments, further illustrates the laser-weldable and UV-markable colored polypropylene composite material and its preparation method disclosed in this invention. Unless otherwise specified, the reagents and materials used in the examples and comparative examples are commercially available. Specific product models and other information in the examples are as follows: The polypropylene resin is one of homopolymer polypropylene, random copolymer polypropylene, and block copolymer polypropylene, and the product model is Zhenhai Z30S, PP4025, SP179.

[0070] Bestar RLS Permanent Violet, produced by Wenzhou Baise Fine Pigment Chemical Co., Ltd., has the CI common name Pigment Violet 23 and CAS registration number 6358-30-1. It belongs to the dioxazine organic pigment class and is a deep green-violet powder with high tinting strength and brightness. It has a heat resistance of up to 250℃ and a lightfastness of grade 8.

[0071] Superfast Pink 05, also known as Superfast® Pink, has a CAS registration number of 980-26-7. It belongs to the quinacridone class of organic pigments and was purchased from Jiangyin Tenghuo Trading Co., Ltd. It is bluish-red in color, with a hue close to magenta. It has a heat resistance of up to 250℃ and a lightfastness rating of 8.

[0072] Clariant BG Blue, also known as Clariant PV Fast Blue BG, is produced by Clariant. Its CI common name is Pigment Blue 15:3, and its CAS registration number is 147-14-8. It belongs to the β-type copper phthalocyanine organic pigment family, exhibiting a greenish-blue hue. It has a heat resistance up to 300℃, a lightfastness rating of 8, and a weather resistance rating of 5. It possesses good dispersibility and excellent fastness. Its average particle size is approximately 74 nm, and its specific surface area is approximately 57 m². 2 / g.

[0073] Sudaperm Yellow 2925K, produced by Sudaperm Corporation of India, is known by its CI generic name Pigment Yellow 110 and CAS registration number 106276-80-6. It belongs to the isoindolinone class of organic pigments and is a translucent reddish-yellow powder. It has a heat resistance of up to 300℃, a lightfastness of 7-8, a weather resistance of 4-5, high tinting strength, and is easy to disperse.

[0074] Antioxidant is a mixture of antioxidant 168 and antioxidant 1010 in a 1:1 ratio.

[0075] The lubricant used is calcium stearate or polyethylene wax.

[0076] Nano zinc oxide, using commercially available product, model AZO66, with a particle size of 250~350nm, and a median particle size D50≤300 nm.

[0077] Porous nano-silica, commercially available product, model CT-200, purchased from Shouguang Changtai New Material Co., Ltd., with an average particle size of 7~40 nm and a specific surface area of ​​200~500 m². 2 / g.

[0078] The specific product models and other information in the comparison examples are as follows: Inorganic violet pigment, using ultramarine violet, its common CI name is CI Pigment Violet 15, CAS registration number is 12769-96-1, belongs to aluminosilicate complex, specifically in the form of a reddish-purple powder, with heat resistance up to 300~350℃.

[0079] Common azo yellow pigment, using permanent yellow GR, its CI common name is CI Pigment Yellow 13, CAS number is 5102-83-0, it belongs to the diazo organic pigment, specifically in the form of reddish-yellow powder, and its heat resistance can reach 180~200℃.

[0080] Colored polypropylene composite materials were prepared according to the above preparation method. The materials obtained in the examples and comparative examples were dried at 100°C for 4 hours and injection molded according to the corresponding index testing standards. After injection molding, the samples were conditioned in a standard laboratory environment with a temperature of 23 ± 2 ℃ and a relative humidity of 50 ± 10 % for no less than 48 hours to eliminate the effects of internal stress and moisture absorption. Subsequently, near-infrared transmittance, laser welding performance, and ultraviolet marking effect were tested, and the processing performance and appearance of the samples were observed and recorded.

[0081] The performance metrics of both the examples and comparative examples were tested using known methods in the prior art. The specific test methods are as follows: 1. Processing performance: Observe the material feeding during the mixing and extrusion process to determine if there are problems such as looseness or blockage.

[0082] 2. Appearance: Visually inspect the color uniformity of the composite material product, whether there are any impurities or color differences.

[0083] 3. Near-infrared transmittance: Tested according to ASTM D1003, the composite material was injection molded into a square sample with dimensions of 60mm × 60mm × 2.0mm. A UV-Vis-NIR spectrophotometer was used to test the transmittance of a 2mm thick sample in the 980nm wavelength range. Specifically, the wavelength range was set to 980nm, the scanning speed to 300 nm / min, and the slit width to 2 nm, with air as a reference. The transmittance of the sample at 980nm was recorded, and three different locations were tested for each sample. The arithmetic mean was taken as the final result.

[0084] 4. Laser welding performance: The composite material was injection molded into welding test pieces with dimensions of 100mm×25mm×2.0mm. The two test pieces were overlapped using a laser transmission welding method with an overlap width of 15mm. The upper layer was the composite material of this invention, and the lower layer was a laser absorption layer. The lower layer was made of polypropylene material with 0.5% carbon black added, which was commercially available.

[0085] A laser welding machine was used with welding parameters of 180W laser power and 500mm / s welding speed to ensure welding quality and efficiency. After welding, the weld was broken to observe whether there were cracks or weld detachment.

[0086] 5. UV Marking Effect Test: A 355nm UV marking machine was used, with marking parameters set as follows: power 4 W, scanning speed 1500 mm / s, sample size 60mm×40mm×2mm color plate, and marking shape of three Chinese characters "polypropylene". The color and clarity of the marking were observed, and the contrast between the marking and the background color was tested.

[0087] Contrast Test: Using a spectrophotometer, under D65 standard light source and a 10° viewing angle, the spectral reflectance of the marked area and the unmarked colored substrate area were measured respectively. The contrast ratio was calculated according to the following formula: C = (R0-R1) / R0 × 100%; In the formula, C represents the contrast ratio (%), R0 represents the average reflectance of the unlabeled area, and R1 represents the average reflectance of the labeled area. Five different locations were measured for each sample, and the arithmetic mean was taken as the final result. Higher contrast ratios indicate clearer labeling.

[0088] Specific embodiments and comparative examples are shown below: Clariant BG Blue System

[0089] Formula (parts by weight): 98.95 parts random copolymer polypropylene, 0.05 parts Clariant BG Blue, 0.4 parts antioxidant, and 0.6 parts calcium stearate.

[0090] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a blue polypropylene composite material based on the Clariant BG Blue system was prepared, and its UV marking and welding performance were tested.

[0091] Performance test results: Appearance: Uniform and vibrant green and blue, without impurities or color differences; Processing performance: High-speed and uniform mixing, smooth feeding from twin-screw extrusion, and no loosening or clogging; Near-infrared transmittance: The transmittance of a 2mm thick product in the 980nm wavelength band is 46%; Laser welding performance: The body breaks after stretching, and there are no cracks or weld failures at the weld joint, indicating stable welding. UV marking effect: After 355nm UV marking, a clear white mark is presented with a contrast of 82%. The edges of the characters are sharp and do not yellow. The mark is wear-resistant and weather-resistant.

[0092] Example 2: Sudaperm Yellow 2925K System Formula (parts by weight): 99.0 parts homopolymer polypropylene, 0.18 parts Sudaperm Yellow 2925K, 0.3 parts antioxidant, 0.52 parts polyethylene wax.

[0093] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a yellow polypropylene composite material of the Sudaperm Yellow 2925K system was prepared, and UV marking and welding performance tests were conducted.

[0094] Performance test results: Appearance: Uniform and pure green-yellow hue, with excellent color stability; Processing performance: Smooth material feeding, no loose or clogged issues, stable mixing and extrusion processes; Near-infrared transmittance: The transmittance of a 2mm thick product in the 980nm wavelength band is 49%; Laser welding performance: The body breaks after stretching, the welding effect is good, and the connection is reliable; UV marking effect: After UV marking, a clear white mark is displayed with a contrast of 83%, no blurring, and excellent whitening effect.

[0095] Example 3: Bestar RLS Permanent Violet System Formula (parts by weight): 98.7 parts random copolymer polypropylene, 0.3 parts Bestos RLS permanent violet, 0.3 parts antioxidant, 0.7 parts calcium stearate.

[0096] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a purple polypropylene composite material of the Bestar RLS permanent purple system was prepared, and UV marking and welding performance were tested.

[0097] Performance test results: Appearance: Uniform, dreamy deep blue-purple hue, soft tone, no impurities; Processing performance: Smooth material feeding, no loose or clogged issues, stable mixing and extrusion processes; Near-infrared transmittance: The transmittance of a 2mm thick product in the 980nm wavelength band is 42%; Laser welding performance: The body breaks after stretching, meeting the connection requirements of high-end products; UV marking effect: UV marking produces high whiteness white markings with a contrast of 85%, excellent whitening effect, and clear lettering.

[0098] Example 4: Superfast Pink 05 System Formula (parts by weight): 97.65 parts random copolymer polypropylene, 0.12 parts Superfast Pink 05, 0.05 parts nano zinc oxide, 1.5 parts porous nano silica, 0.3 parts antioxidant, 0.38 parts polyethylene wax.

[0099] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a pink polypropylene composite material of the Superfast Pink 05 system was prepared, and UV marking and welding performance tests were conducted.

[0100] Performance test results: Appearance: Even and soft pink, vibrant color, no color difference; Processing performance: Smooth feeding, high mixing and extrusion efficiency, fully adapted to industrial production; Near-infrared transmittance: The transmittance of a 2mm thick product in the 980nm wavelength band is 34%; Laser welding performance: The body fractures after stretching, and the welding is stable and reliable; UV marking effect: UV marking produces clear white marks with a contrast of 89% and excellent whitening effect, meeting the marking requirements.

[0101] Example 5: Clariant BG Blue + Sudaperm Yellow 2925K compound system Formula (parts by weight): 98.5 parts block copolymer polypropylene, 0.25 parts Clariant BG Blue, 0.25 parts Sudaperm Yellow 2925K, 0.2 parts antioxidant, and 0.8 parts calcium stearate.

[0102] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a blue-green polypropylene composite material with Clariant BG Blue + Sudaperm Yellow 2925K compound system was prepared, and UV marking and welding performance tests were conducted.

[0103] Performance test results: Appearance: Uniform and bright blue-green, without impurities or color difference; Processing performance: High-speed and uniform mixing; smooth feeding via twin-screw extrusion. Near-infrared transmittance: The transmittance of a 2mm thick product in the 980nm wavelength band is 32%; Laser welding performance: The body fractures after stretching, and the weld is stable; UV marking effect: After 355nm UV marking, a clear white mark is presented with a contrast of 81%, which meets the needs of practical applications.

[0104] Example 6: Sudaperm Yellow 2925K + Clariant BG Blue + Superfast Pink 05 blend Formula (parts by weight): 98.8 parts random copolymer polypropylene, 0.08 parts Sudaperm Yellow 2925K, 0.06 parts Clariant BG Blue, 0.06 parts Superfast Pink 05, 0.3 parts antioxidant, 0.7 parts calcium stearate.

[0105] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a black polypropylene composite material with a blend of Sudaperm Yellow 2925K, Clariant BG Blue, and Superfast Pink 05 was prepared and tested for UV marking and welding performance.

[0106] Performance test results: Appearance: Uniform and pure black, with full color and no impurities, no color difference, and no graying or mottled appearance; Processing performance: High-speed and uniform mixing, smooth feeding during twin-screw extrusion, no loosening or clogging, and stable mixing and extrusion processes; Near-infrared transmittance: The transmittance of a 2mm thick product in the 980nm wavelength band is 46%; Laser welding performance: The body breaks after stretching, and there are no cracks or weld failures at the weld joint, indicating stable and reliable welding. UV marking effect: After 355nm UV marking, a clear and bright white mark is presented with a marking contrast of 91%, and the black background and white mark have a very strong contrast.

[0107] Example 7: Sudaperm Yellow 2925K System Formula (parts by weight): 94.5 parts homopolymer polypropylene, 0.18 parts Sudaperm Yellow 2925K, 1.5 parts nano zinc oxide, 3 parts porous nano silica, 0.3 parts antioxidant, and 0.52 parts polyethylene wax.

[0108] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a yellow polypropylene composite material of the Sudaperm Yellow 2925K system was prepared, and UV marking and welding performance tests were conducted.

[0109] Performance test results: Appearance: Uniform, pure yellow with excellent color stability; Processing performance: Smooth material feeding, no loose or clogged issues, stable mixing and extrusion processes; Near-infrared transmittance: The transmittance of a 2mm thick product in the 980nm wavelength band is 23%; Laser welding performance: The body breaks after stretching, the welding effect is good, and the connection is reliable; UV marking effect: After UV marking, a clear white mark is displayed with a contrast of 90%, no blurring, and excellent whitening effect.

[0110] Comparison Example 1: Clariant BG Blue System Formula (parts by weight): 96.2 parts random copolymer polypropylene, 0.15 parts Clariant BG Blue, 2.0 parts nano zinc oxide, 0.5 parts porous nano silica, 0.4 parts antioxidant, and 0.75 parts calcium stearate.

[0111] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a blue polypropylene composite material based on the Clariant BG Blue system was prepared, and its UV marking and welding performance were tested.

[0112] The difference between Comparative Example 1 and Example 1 is that a UV marking functional additive was added, and the amounts of polypropylene resin, colored organic transparent powder, and additives were adjusted.

[0113] Performance test results: Appearance: Uniform green-blue hue, no obvious abnormalities; Processing performance: Material feeding is smooth, with no obvious processing problems; Near-infrared transmittance: The transmittance of a 2mm thick product in the 980nm wavelength band is 6%; Laser welding performance: Laser penetration welding cannot be achieved, and the welding function is ineffective; UV marking effect: Although it can produce white markings, it cannot meet the needs of practical applications due to the failure of the welding function.

[0114] Comparative Example 2: Sudaperm Yellow 2925K System Formula (parts by weight): 94.8 parts homopolymer polypropylene, 0.18 parts Sudaperm Yellow 2925K, 0.8 parts nano zinc oxide, 4.0 parts porous nano silica, 0.3 parts antioxidant, and 0.72 parts polyethylene wax.

[0115] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a yellow polypropylene composite material of the Sudaperm Yellow 2925K system was prepared, and UV marking and welding performance tests were conducted.

[0116] The difference between Comparative Example 2 and Example 2 is that a UV marking functional additive was added, and the amounts of polypropylene resin, colored organic transparent powder, and additives were adjusted.

[0117] Performance test results: Appearance: Uniform greenish-yellow color, with no obvious abnormalities; Processing performance: Porous nano-silica is extremely fluffy, easily separates during high-speed mixing, and has uneven feeding during extrusion, resulting in extremely low production efficiency; Near-infrared transmittance: The transmittance of the 2mm thick product in the 980nm band is 31%, with no significant decrease in transmittance; Laser welding performance: The body fractures after stretching, and the welding effect is good; UV marking effect: The marking is white with a contrast of 87%, which is considered satisfactory.

[0118] Comparative Example 3: Traditional Inorganic Pigment Coloring System Formula (parts by weight): 98.7 parts random copolymer polypropylene, 0.3 parts inorganic purple pigment, 0.3 parts antioxidant, 0.7 parts calcium stearate.

[0119] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a purple polypropylene composite material with an inorganic purple pigment system was prepared, and its UV marking and welding performance were tested.

[0120] The difference between Comparative Example 3 and Example 3 is that the colored organic translucent pigment, Bestar RLS Permanent Violet, is replaced with an inorganic purple pigment.

[0121] Performance test results: Appearance: Purple, but the color is dull, has impurities, and the color difference is obvious; Processing performance: Material feeding is smooth, with no obvious processing problems; Near-infrared transmittance: The transmittance of a 2mm thick product in the 980nm wavelength band is 0.05%; Laser welding performance: Laser welding cannot be performed; welding function is ineffective. UV marking effect: The marking is a blurry gray with a contrast of 33%, and it cannot form a clear white marking, which does not meet the usage requirements.

[0122] Comparative Example 4: Common Organic Pigment Coloring System Formula (parts by weight): 98.7 parts random copolymer polypropylene, 0.3 parts common azo yellow pigment, 0.3 parts antioxidant, 0.7 parts calcium stearate.

[0123] Following the above-mentioned method for preparing laser-weldable and UV-markable colored polypropylene composite materials, a yellow polypropylene composite material based on a common azo yellow pigment system was prepared, and its UV marking and welding performance were tested.

[0124] The difference between Comparative Example 4 and Example 2 is that the colored organic translucent pigment Sudaperm Yellow 2925K was replaced with a common azo yellow pigment.

[0125] Performance test results: Appearance: Yellow, but the color is uneven; Processing performance: Material feeding is smooth, with no obvious processing problems; Near-infrared transmittance: The transmittance of a 2mm thick product in the 980nm wavelength band is 42%; Laser welding performance: The body fractures after stretching, and the welding effect is good; UV marking effect: No clear markings are visible, only blurry gray traces are shown, with a contrast of 28%, which does not meet the usage requirements.

[0126] The composition and dosage of the laser-weldable and UV-markable colored polypropylene composite materials of Examples 1-7 and Comparative Examples 1-4 are summarized in Tables 1 and 2, respectively.

[0127] Table 1. Weight proportions of each component in Examples 1-7 Polypropylene resin 98.95 99.0 98.7 97.65 98.5 98.8 94.5 Best RLS Permanent Purple —— —— 0.3 —— —— —— —— Superfast Pink 05 —— —— —— 0.12 —— 0.06 —— Clariant BG Blue 0.05 —— —— —— 0.25 0.06 —— Sudaperm Yellow 2925K —— 0.18 —— —— 0.25 0.08 0.18 Nano zinc oxide —— —— —— 0.05 —— —— 1.5 Porous nano silica —— —— —— 1.5 —— —— 3.0 antioxidants 0.4 0.3 0.3 0.3 0.2 0.3 0.3 lubricant 0.6 0.52 0.7 0.38 0.8 0.7 0.52 Table 2. Weight proportions of each component in Comparative Examples 1-4 Polypropylene resin 96.2 94.8 98.7 99.0 Inorganic purple pigment —— —— 0.3 —— Common azo yellow pigment 0.18 Clariant BG Blue 0.15 —— —— —— Sudaperm Yellow 2925K —— 0.18 —— —— Nano zinc oxide 2.0 0.8 —— —— Porous nano silica 0.5 4.0 —— —— antioxidants 0.4 0.3 0.3 0.3 lubricant 0.75 0.72 0.7 0.52 See attached document Figure 1 The sample of Example 1 has a uniform and bright green-blue appearance, with no impurities or color difference; after ultraviolet marking, it shows a clear white mark with sharp edges.

[0128] See attached document Figure 2 The sample in Example 3 has a uniform, dreamy deep blue-purple appearance with a soft tone and no impurities; after ultraviolet marking, it presents a high-whiteness white mark with the best whitening effect and clear lettering.

[0129] See attached document Figure 3 The sample in Example 4 has a uniform and soft pink appearance with bright color and no color difference; after ultraviolet marking, it shows a clear white mark, which meets the marking requirements.

[0130] See attached document Figure 4 The sample in Example 6 has a uniform and pure black appearance, with a full color without impurities or color difference, and no graying or mottled phenomenon. A stable black appearance is achieved by mixing red, yellow and blue three colors, without the need to add extra carbon black; after ultraviolet marking, it presents a clear and bright white mark.

[0131] See attached document Figure 5 The sample in Comparative Example 4 was yellow in appearance, but the color was uneven; after UV marking, there was no obvious and clear mark, only a blurry gray trace, and the contrast was low, which could not meet the usage requirements.

[0132] The specific test results of Examples 1-7 and Comparative Examples 1-4 are shown in Tables 3 and 4, respectively.

[0133] Table 3. Performance test results of colored polypropylene composite materials obtained in Examples 1-7 Near-infrared transmittance % 46 49 42 34 32 46 23 Contrast % 82 83 85 89 81 91 90 Table 4. Performance test results of colored polypropylene composite materials obtained in Comparative Examples 1-4 Near-infrared transmittance % 6 31 0.05 42 Contrast % 90 87 33 28 As can be seen from the results in Tables 3 and 4 combined with the above content, Examples 1-7 can achieve uniform and bright color appearance, stable laser welding performance and high-contrast white marking performance, with a specific contrast ratio > 80%. Among them, Examples 1-3 and 5-6 can still achieve clear white marking without adding additional ultraviolet marking functional components. After adding ultraviolet marking functional components in Examples 4 and 7, the marking contrast is further improved and the near-infrared transmittance is significantly reduced, which is suitable for high-end scene requirements.

[0134] Examples 4 and 7 demonstrate the synergistic effect of combining nano-zinc oxide and porous nano-silica to achieve excellent UV marking and welding performance. The nano-zinc oxide primarily absorbs UV laser energy and induces micro-bubbling, generating white scattering centers. The porous nano-silica promotes localized micro-carbonization to form contrasting contours and enhances light scattering through its porous structure. The well-matched particle size and dispersibility of both components form a uniform "two-component marking network" within the polypropylene matrix, significantly improving the contrast and white saturation of the markings.

[0135] In addition, the composite materials prepared in Examples 1-7 exhibit near-infrared transmittance >20% at a sample thickness of 2 mm, ensuring that laser energy penetrates the upper material and is absorbed by the lower absorbing layer, generating sufficient heat to melt the welding interface. Furthermore, the composite materials prepared in Examples 1-7 showed good weldability after laser welding and lap jointing, with tensile testing resulting in bulk failure.

[0136] As can be seen from Examples 1-7 and Comparative Example 1 and the corresponding test results, the amount of nano zinc oxide used in Comparative Example 1 was too large, and the near-infrared transmittance of the sample dropped significantly to 6%, which made it difficult to guarantee the laser penetration welding performance and could not meet the actual application requirements.

[0137] As can be seen from Examples 1-7 and Comparative Example 2 and the corresponding test results, the amount of porous nano-silica used in Comparative Example 2 was too large, the UV marking effect was no longer significantly improved, the cost increased, the processing became difficult, the production efficiency was low, and the raw material cost increased significantly, making it impossible to achieve industrial mass production.

[0138] The results of Example 3 and Comparative Example 3 and their corresponding test results show that the near-infrared transmittance and marking contrast index of Comparative Example 3 are significantly different from those of Example 3, indicating that traditional inorganic pigment coloring cannot achieve the synergistic unity of colored appearance, laser welding, and ultraviolet marking whitening.

[0139] Specifically, in Comparative Example 3, ordinary inorganic violet pigment was used to replace the Bestar RLS permanent violet in Example 3. Inorganic violet pigment belongs to aluminosilicate complex, and its particle size is usually 1~5μm, which is much larger than that of organic pigments (0.01~0.5μm). In the polypropylene matrix, it will produce strong Mie scattering, causing the near-infrared transmittance to drop sharply from 42% in Example 3 to 0.05%, and the laser welding strength to decrease by more than 90%. At the same time, the contribution of inorganic pigment to tinting strength is much lower than that of organic pigment, resulting in insufficient tinting, which in turn leads to a significant decrease in marking contrast, blurred marking edges and uneven color, and failure to obtain clear and uniform white markings.

[0140] The results of Example 2 and Comparative Example 4 and their corresponding test results show that the near-infrared transmittance of Comparative Example 4 is slightly lower than that of Example 2, but the marking contrast index is significantly different from that of Example 2. This indicates that although ordinary organic pigments that do not have their own UV marking whitening performance can achieve near-infrared transmittance of colored polypropylene, conventional UV marking can only form gray characters on colored substrates with extremely low contrast to the colored background. It is impossible to form a clear, distinguishable, high-whiteness permanent mark, and it is impossible to achieve the synergistic unity of colored appearance, laser welding, and UV marking whitening.

[0141] Specifically, in Comparative Example 4, ordinary azo yellow pigment was used instead of Sudaperm Yellow 2925K in Example 2. The azo chromophores of ordinary azo yellow pigment are prone to breakage and decomposition at processing temperatures of 180~230℃, producing colored amine byproducts, resulting in uneven matrix color. At the same time, the near-infrared transmittance is slightly reduced, which slightly impairs the laser welding performance. In addition, the decomposition products will also form uneven carbonized spots during laser marking, reducing the marking contrast to 28%, which is completely unable to meet the industrial application requirements for high-definition white marking.

[0142] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0143] The preparation method of a laser-weldable and UV-markable colored polypropylene composite material provided in the embodiments of this application has been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A colored polypropylene composite material that can be laser-welded and UV-marked, characterized in that, The components include the following parts by weight: Polypropylene resin: 93.50~99.75 parts; Colored organic translucent powder: 0.05~0.50 parts; The colored organic light-transmitting powder has a characteristic absorption peak in the 400-760 nm visible light band to make the polypropylene composite material appear colored, and the polypropylene composite material has a transmittance of >20% in the 980 nm near-infrared band when the thickness is 2 mm; The polypropylene composite material is marked with a 355 nm ultraviolet laser to form a white mark on the surface of the colored substrate, and the contrast between the white mark and the unmarked area is >80%.

2. The laser-weldable and UV-markable colored polypropylene composite material according to claim 1, characterized in that, The colored organic translucent pigment is selected from one or more of dioxazine, phthalocyanine, isoindolineone, and quinacridone organic pigments.

3. The laser-weldable and UV-markable colored polypropylene composite material according to claim 2, characterized in that, The colored organic translucent pigment is selected from at least one of CI pigment violet 23, CI pigment red 122, CI pigment blue 15:3, and CI pigment yellow 110.

4. The laser-weldable and UV-markable colored polypropylene composite material according to claim 1, characterized in that, The colored organic translucent pigment is selected from at least one of Bestar RLS Permanent Violet, Superfast Pink 05, Clariant BG Blue, and Sudaperm Yellow 2925K.

5. A laser-weldable and UV-markable colored polypropylene composite material according to claim 1, characterized in that, The polypropylene composite material also includes the following components in parts by weight: Additives: 0.2~1.5 parts; The additives are selected from one or more of antioxidants and lubricants, and the antioxidants are 0.1 to 0.5 parts by weight, and the lubricants are 0.1 to 1.0 parts by weight.

6. A laser-weldable and UV-markable colored polypropylene composite material according to claim 1, characterized in that, The polypropylene composite material also includes the following components in parts by weight: UV marking functional component: 0~4.5 parts; The ultraviolet marking functional component is composed of nano zinc oxide and porous nano silica.

7. A laser-weldable and UV-markable colored polypropylene composite material according to claim 6, characterized in that, The nano zinc oxide comprises 0 to 1.5 parts by weight, and the porous nano silica comprises 0 to 3.0 parts by weight.

8. A laser-weldable and UV-markable colored polypropylene composite material according to claim 6, characterized in that, The nano zinc oxide has a particle size of 250~350 nm, and its median particle size D50 ≤ 300 nm.

9. A laser-weldable and UV-markable colored polypropylene composite material according to claim 6, characterized in that, The porous nano-silica has an average particle size of 10-50 nm and a specific surface area of ​​300-500 m². 2 / g.

10. A method for preparing a laser-weldable and UV-markable colored polypropylene composite material as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Mix polypropylene resin, colored organic transparent powder, additives and UV marking functional components to obtain a uniform mixture; S2. The mixture is added through the main feed port of a twin-screw extruder, melt-blended and extruded at a temperature of 180~230℃, cooled to room temperature with water, and then air-dried and pelletized to obtain polypropylene composite material particles. S3. The polypropylene composite material particles are injection molded or extruded to obtain the polypropylene composite material.

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