Special polypropylene plastic needle material and preparation method thereof

Abstract

The invention provides a special material for a polypropylene plastic needle and a preparation method thereof, and belongs to the technical field of high polymer materials and modification. The special material for the polypropylene plastic needle, provided by the invention, is prepared from the following raw material components in parts by weight: 100 parts of homo-polypropylene, 0.5 to 1.0 part of itaconic acid, 0.05 to 0.1 part of (4E)-4-octylenedioic acid, 0.1 to 0.3 part of nano-zinc oxide, 0.1 to 0.2 part of ethylene bis stearamide and 0.1 to 0.3 part of initiator, the melt flow rate of the homo-polypropylene is 2.5 to 4.5 g / 10 min. The special material for the polypropylene plastic needle has excellent elongation at break, toughness and stiffness, the molding qualification rate and the product quality qualification rate are both considered, and the preparation method is simple and easy to control and suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and modification technology, specifically relating to a special material for polypropylene injection molding and its preparation method. Background Technology

[0002] In the garment hangtag industry, plastic pins have been widely used to replace traditional metal pins. Plastic pins are mainly made of nylon and polypropylene, with polypropylene being the most commonly used due to its relatively simple processing and low material cost. Polypropylene pins are made by first injection molding a preform from polypropylene material, then heating and softening the preform before rapidly stretching it to obtain the finished pin. Structurally, polypropylene pins consist of two parts: the fine needle and the head. The fine needle requires good hardness, strength, and stiffness, and must remain flat and resistant to deformation during long-term use, while also exhibiting good transparency. The head requires good toughness and must not break when pinched. Therefore, the requirements for the special polypropylene material used in polypropylene pin processing are: good melt flowability and high tensile elongation, meaning a high elongation at break under high-speed stretching.

[0003] Common types of polypropylene include homopolymer polypropylene (PPH), random copolymer polypropylene (PPR), and block copolymer polypropylene (PPB). Among them, PPH has excellent rigidity and a high melting point, but poor toughness, making it unsuitable for direct application in high-speed thermoforming scenarios, such as the preparation of glue needles; while PPR and PPB have good toughness, their rigidity and mechanical strength are insufficient, which easily leads to defects such as curling and breakage in polypropylene products.

[0004] In actual production, different types or grades of polypropylene are often used together to make full use of the advantages of various polypropylene materials and make up for their respective shortcomings. However, this also results in complex formulations, poor overall performance, and disadvantages such as low molding pass rate and low product quality pass rate. Summary of the Invention

[0005] The purpose of this invention is to provide a polypropylene compound, its preparation method and application, and a polypropylene injection molding compound. The polypropylene compound provided by this invention has excellent elongation at break, toughness and stiffness, and takes into account both the molding qualification rate and the product quality qualification rate.

[0006] To achieve the objectives of this invention, the following technical solutions are provided: A special material for polypropylene injection molding, comprising the following raw material components: 100 parts of homopolymer polypropylene, 0.5-1.0 parts of itaconic acid, 0.05-0.1 parts of (4E)-4-octenedioic acid, 0.1-0.3 parts of nano zinc oxide, 0.1-0.2 parts of ethylene bis-stearamide, and 0.1-0.3 parts of initiator; The melt flow rate of the homopolymer polypropylene is 2.5~4.5 g / 10 min.

[0007] Preferably, the homopolymer polypropylene has a weight-average molecular weight of 220,000 to 700,000 and a molecular weight distribution range of 5 to 12.

[0008] Preferably, the initiator includes one or more of dicumyl peroxide, dicumyl hydrogen peroxide, and cumyl peroxyhydroxy.

[0009] Preferably, it also includes 0.05 to 0.1 parts of a release agent.

[0010] Preferably, the release agent is polyvinylidene fluoride.

[0011] The present invention also provides a method for preparing the polypropylene compound described in the above technical solution, comprising the following steps: Homopolymer polypropylene, itaconic acid, (4E)-4-octenedioic acid, nano zinc oxide, ethylene bis-stearamide and initiator are mixed; Alternatively, homopolymer polypropylene, itaconic acid, (4E)-4-octenedioic acid, nano zinc oxide, ethylene bis-stearamide, initiator and release agent can be mixed; The resulting mixture is melt-extruded and granulated to obtain the polypropylene injection molding material.

[0012] Preferably, the temperature of the melt extrusion granulation is 165~220℃.

[0013] Preferably, the melt extrusion granulation is a six-zone temperature-controlled granulation; the temperatures of the six zones are sequentially 165~175℃, 188~192℃, 193~198℃, 199~203℃, 205~215℃ and 205~215℃.

[0014] The present invention also provides a polypropylene injection pin, which is prepared by injection molding a preform from the polypropylene injection pin special material described in the above technical solution or the preparation method described in the above technical solution, and then heating and softening the preform before high-speed stretching to obtain the injection pin.

[0015] This invention provides a special material for polypropylene injection molding, comprising the following raw material components: 100 parts homopolymer polypropylene, 0.5-1.0 parts itaconic acid, 0.05-0.1 parts (4E)-4-octenedioic acid, 0.1-0.3 parts nano zinc oxide, 0.1-0.2 parts ethylene bis-stearamide, and 0.1-0.3 parts initiator; the melt flow rate of the homopolymer polypropylene is 2.5-4.5 g / 10 min. This invention, through crystal form modification, transforms α-crystalline homopolymer polypropylene into β-crystalline polypropylene, significantly improving the toughness and tensile strain at break of polypropylene while maintaining the basic rigidity of the homopolymer polypropylene. In this invention, itaconic acid and nano zinc oxide can generate zinc itaconic acid in situ, and (4E)-4-octenediaic acid and zinc oxide can generate zinc (4E)-4-octenediaic acid. Both have polypropylene β-nucleation effects. Meanwhile, ethylene bis-stearamide, as an amide compound, can further promote β-crystal nucleation, avoiding the limitations of using a single β-crystal nucleating agent. Furthermore, the synergistic induction of crystallization by (4E)-4-octenediaic acid and amide enhances the controllability and repeatability of performance improvement.

[0016] Furthermore, the ethylene bis-stearamide used in this invention is often used for lubrication in other processing systems in the prior art. However, in this invention, thanks to the in-situ grafting reaction of itaconic acid containing unsaturated double bonds and (4E)-4-octenediaic acid, the polarity of the polypropylene matrix is ​​enhanced, significantly improving the dispersibility and crystallization induction efficiency of ethylene bis-stearamide. It exhibits excellent β-crystal nucleation ability, which is significantly different from the conventional use of ethylene bis-stearamide as a single external lubricant. At the same time, in this invention, itaconic acid and (4E)-4-octenediaic acid not only participate in nucleation but also enhance their embedding stability and microdispersion in the polypropylene matrix through the synergistic effect with the initiator to form a grafting reaction. By forming an excellent internal lubrication network with the grafted and modified polar polypropylene matrix, it exhibits a combined effect in promoting nucleation, improving compatibility, and increasing tensile strain at fracture.

[0017] Furthermore, in this invention, itaconic acid and (4E)-4-octenediaic acid exhibit high surface activity, which is beneficial for the dispersion of excess unreacted nano-zinc oxide. Moreover, itaconic acid and (4E)-4-octenediaic acid, after grafting onto polypropylene, have a compatibilizing effect on zinc oxide, improving the compatibility between nano-zinc oxide and polypropylene. This allows the nano-zinc oxide to be fully and uniformly dispersed in the polypropylene composite material, effectively leveraging its reinforcing effect. In conjunction with the foregoing, the grafted polypropylene possesses a certain degree of polarity, which is beneficial for the dispersion and interfacial bonding of zinc oxide, constructing a stable, high-performance β-crystal induction environment, enhancing nucleation efficiency, and further improving the uniformity of the material's crystal structure and molding stability.

[0018] On the other hand, polypropylene injection molding material is used to form a preform. After the preform is stretched into injection molding needles at high speed, the strength and rigidity of the fine needles of the preform are improved because they change from β crystals to α crystals after high-speed stretching. Therefore, the fine needles of the injection molding needles have good stiffness. However, the head of the preform is not stretched and is still a β crystal, so the head of the injection molding needle has good toughness.

[0019] This invention achieves comprehensive optimization of the β-crystal induction efficiency, lubrication behavior, and mechanical properties of polypropylene through the rational design of the structure and functional synergy of a multi-component system. It solves the problems of insufficient stiffness, poor toughness, and poor processing stability in traditional glue needle materials, and possesses significant practical value and application prospects. Detailed Implementation

[0020] In this invention, if a special material for polypropylene injection molding is provided, it includes the following raw material components: 100 parts of homopolymer polypropylene, 0.5-1.0 parts of itaconic acid, 0.05-0.1 parts of (4E)-4-octenedioic acid, 0.1-0.3 parts of nano zinc oxide, 0.1-0.2 parts of ethylene bis-stearamide, and 0.1-0.3 parts of initiator; The melt flow rate of the homopolymer polypropylene is 2.5~4.5 g / 10 min.

[0021] Unless otherwise specified, all raw materials used in the preparation are commercially available products well known to those skilled in the art.

[0022] In this invention, the raw material components of the polypropylene injection molding compound, by mass, include 100 parts of homopolymer polypropylene; the melt flow rate of the homopolymer polypropylene is 2.5~4.5 g / 10 min, and in specific embodiments, it can be 2.9 or 3.4 g / 10 min; the weight-average molecular weight of the homopolymer polypropylene is 220,000~700,000, and the molecular weight distribution range is 5~12. This invention controls melt flow and stretching adaptability. During the solid-phase grafting process of polypropylene, molecular chains break. To reduce this side effect, existing technologies require the addition of antioxidants to reduce polypropylene degradation, but this invention utilizes this degradation effect to reduce the molecular weight of a portion of the polypropylene. Specifically, the higher the molecular weight of polypropylene, the better its toughness, but the higher the molecular weight, the poorer the melt flow. On the other hand, injection molding compound production involves high-temperature and high-speed stretching. High molecular weight molecules have more intermolecular entanglement, and the molecular chains are easily broken during rapid stretching. However, low molecular weight molecules have low impact strength. By degrading a small amount, a portion of lower molecular weight can be produced, which is beneficial for high-speed stretching while maintaining high toughness. Meanwhile, the moderate degradation effect initiated by the initiator can reduce some of the molecular weight and improve the overall melt flowability of the system; at the same time, the high molecular weight part is retained to provide skeletal support, thus synergistically ensuring the triple characteristics of high flowability, high strength and high toughness of the material.

[0023] In this invention, the raw material components of the polypropylene injection molding compound include 0.5 to 1.0 parts of itaconic acid, which can be 0.6, 0.7 or 0.8 parts in specific embodiments.

[0024] In this invention, the raw material components of the polypropylene injection molding compound include 0.05 to 0.1 parts of (4E)-4-octenedioic acid, which may be 0.06, 0.07 or 0.08 parts in specific embodiments.

[0025] In this invention, the raw material components of the polypropylene injection molding compound include 0.1 to 0.3 parts by mass of nano-zinc oxide; the particle size of the nano-zinc oxide can be 20 to 100 nm, and in specific embodiments, it can be 30 or 50 nm. In this invention, itaconic acid and nano-zinc oxide can generate zinc itaconic acid in situ, and (4E)-4-octenediaic acid and zinc oxide can generate zinc (4E)-4-octenediaic acid. Both have a β-nucleation effect on polypropylene. At the same time, ethylene bis-stearamide, as an amide compound, can further promote β-crystal nucleation, avoiding the limitations of using a single β-crystal nucleating agent; and through the synergistic induction of crystallization by (4E)-4-octenediaic acid and amide, the controllability and repeatability of performance improvement are enhanced.

[0026] In this invention, the raw material components of the polypropylene injection molding compound further include 0.05-0.1 parts of a release agent by weight, which in specific embodiments may be 0.08 or 0.1 parts; the release agent is polyvinylidene fluoride (PVDF). This invention uses PVDF as a release agent, which has excellent thermal stability and lubrication properties, significantly reducing the adhesion of the polypropylene melt and improving the demolding efficiency of the preform.

[0027] In this invention, the raw material components of the polypropylene injection molding compound include 0.1 to 0.3 parts by weight, and in a specific embodiment, 0.2 parts; the initiator includes one or more of dicumyl peroxide, dicumyl hydroperoxide, and peroxyhydroxycumyl peroxide. The initiator of this invention can initiate the grafting reaction between polypropylene resin and itaconic acid and (4E)-4-octenedioic acid.

[0028] This invention also provides a method for preparing the polypropylene injection molding compound described in the above technical solution, comprising the following steps: Homopolymer polypropylene, itaconic acid, (4E)-4-octenedioic acid, nano zinc oxide, ethylene bis-stearamide and initiator are mixed; Alternatively, homopolymer polypropylene, itaconic acid, (4E)-4-octenedioic acid, nano zinc oxide, ethylene bis-stearamide, initiator and release agent can be mixed; The resulting mixture is melt-extruded and granulated to obtain the polypropylene injection molding material.

[0029] In this invention, the mixing temperature is 25~50℃, and in specific embodiments it can be 30, 38, 42 or 45℃; the mixing time is 10~15min, and in specific embodiments it can be 11 or 13min; the mixing is carried out under stirring conditions, and this invention does not have a special limitation on the stirring rate, as long as the components in the mixture are fully mixed.

[0030] In this invention, the melt extrusion granulation is carried out in a twin-screw extruder with an aspect ratio of 32 and six-zone temperature control.

[0031] In this invention, the screw speed during the melt extrusion granulation process is 150~300 r / min, and in specific embodiments it can be 160, 190 or 230 r / min.

[0032] In this invention, the temperature of the melt extrusion granulation is 165~220℃; the extrusion granulation is a six-zone temperature-controlled granulation, and the temperatures of the six zones are sequentially 165~175℃, 88~192℃, 193~198℃, 199~203℃, 205~215℃, and 205~215℃. In specific embodiments, the temperatures can be 170℃, 190℃, 195℃, 200℃, 210℃, 205℃; 170℃, 190℃, 195℃, 200℃, 210℃, 210℃; or 175℃, 195℃, 195℃, 200℃, 210℃, 215℃.

[0033] In this invention, the pelletizing speed during the melt extrusion granulation process is 300~600 r / min, and in specific embodiments, it can be 350, 400, 500 or 550 r / min.

[0034] The present invention also provides a polypropylene injection pin, which is prepared by injection molding a preform from the polypropylene injection pin special material described in the above technical solution or the preparation method described in the above technical solution, and then heating and softening the preform before high-speed stretching to obtain the injection pin.

[0035] To further illustrate the present invention, the following detailed description of the polypropylene injection molding material and preparation method provided by the present invention is provided in conjunction with the embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0036] Example 1 The homopolymer polypropylene is produced by Daqing Petrochemical and is designated as T30S, with a melt flow rate (MFR) of 2.9 g / 10 min.

[0037] 100 parts of homopolymer polypropylene, 0.05 parts of polyvinylidene fluoride, 0.5 parts of itaconic acid, 0.1 parts of (4E)-4-octenedioic acid, 0.1 parts of nano zinc oxide (particle size 50nm), 0.2 parts of dicumyl peroxide, and 0.1 parts of ethylene bis-stearamide were premixed for 15 minutes. The resulting premix was then subjected to reactive extrusion granulation in a twin-screw extruder with a length-to-diameter ratio of 32 and six temperature-controlled zones. The processing temperatures of zones one to six were 170℃, 190℃, 195℃, 200℃, 210℃, and 205℃, respectively. The die head temperature was 210℃, the screw speed was 180 r / min, and the pelletizing speed was 400 r / min. After granulation, the resulting pellets were dried to obtain polypropylene injection molding material.

[0038] Example 2 The homopolymer polypropylene is produced by Yangzi Petrochemical and is designated as F401, with a melt flow rate (MFR) of 3.4 g / 10 min (230℃ / 2.16 kg).

[0039] 100 parts of homopolymer polypropylene, 0.1 parts of polyvinylidene fluoride, 1.0 part of itaconic acid, 0.05 parts of (4E)-4-octenedioic acid, 0.1 parts of nano zinc oxide (particle size 50nm), 0.2 parts of hydroxypropylbenzene peroxide, and 0.2 parts of ethylene bis-stearamide were premixed. The resulting premix was reactively extruded and granulated in a twin-screw extruder with a length-to-diameter ratio of 32 and six temperature-controlled zones. The processing temperatures of zones one to six were 170℃, 190℃, 195℃, 200℃, 210℃, and 210℃, respectively. The die head temperature was 210℃, the screw speed was 250r / min, and the pelletizing speed was 450r / min. After granulation, the resulting granules were dried to obtain polypropylene injection molding material.

[0040] Comparative Example 1 Polypropylene injection molding material was prepared according to the scheme described in Example 1, the only difference being that the homopolymer polypropylene was produced by Fujian Petrochemical with the grade 1714E1 and the melt flow rate (MFR) was 12.1 g / 10 min.

[0041] Comparative Example 2 Polypropylene injection molding material was prepared according to the scheme described in Example 1, the only difference being that the homopolymer polypropylene was produced by Huajin Chemical with the grade YD50G and the melt flow rate (MFR) was 0.3 g / 10 min.

[0042] Comparative Example 3 Polypropylene injection molding material was prepared according to the scheme described in Example 1, except that an initiator was not used.

[0043] Comparative Example 4 Polypropylene needle-specific material was prepared according to the scheme described in Example 1, the only difference being that nano zinc oxide was not used.

[0044] Comparative Example 5 Polypropylene injection molding material was prepared according to the scheme described in Example 1, except that itaconic acid was not used.

[0045] Comparative Example 6 Polypropylene injection molding material was prepared according to the scheme described in Example 1, except that (4E)-4-octenedioic acid was not used.

[0046] Comparative Example 7 Polypropylene injection molding material was prepared according to the scheme described in Example 1, except that ethylene bis-stearamide was not used.

[0047] Application examples The polypropylene glue needle special materials prepared in Examples 1-2 and Comparative Examples 1-7 were used in the glue needle production line for production, requiring a glue needle stretching ratio of 5 times.

[0048] The performance of the obtained glue needles was tested as follows: 1. The rate at which the fine needles of the preform cannot be pulled apart is used as the molding qualification rate.

[0049] 2. Test on the breakage rate of the glue needle tip: Fix the glue needle tip on the Y-shape, pull down the thin needle quickly, and record the number of glue tips that break brittlely. This number is used as the product quality pass rate. The results are shown in the table.

[0050] Table 1. Performance test results of the polypropylene glue needles prepared from the special materials of Examples 1-2 and Comparative Examples 1-7

[0051] As shown in Table 1, the molding qualification rate of the polypropylene injection molding material is over 99.5%, and the product quality qualification rate is also over 99.5%. Furthermore, since the raw material in this invention is homopolymer polypropylene, the resulting injection molding needles also exhibit excellent stiffness.

[0052] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A special material for polypropylene injection molding, characterized in that, Includes the following raw material components: 100 parts of homopolymer polypropylene, 0.5-1.0 parts of itaconic acid, 0.05-0.1 parts of (4E)-4-octenedioic acid, 0.1-0.3 parts of nano zinc oxide, 0.1-0.2 parts of ethylene bis-stearamide, and 0.1-0.3 parts of initiator; The melt flow rate of the homopolymer polypropylene is 2.5~4.5 g / 10 min.

2. The polypropylene injection molding material according to claim 1, characterized in that, The homopolymer polypropylene has a weight-average molecular weight of 220,000 to 700,000 and a molecular weight distribution range of 5 to 12.

3. The polypropylene injection molding material according to claim 1, characterized in that, The initiator includes one or more of dicumyl peroxide, dicumyl hydrogen peroxide, and peroxyhydroxycumyl.

4. The polypropylene injection molding material according to claim 1, characterized in that, It also includes 0.05 to 0.1 parts of release agent.

5. The polypropylene injection molding material according to claim 4, characterized in that, The release agent is polyvinylidene fluoride.

6. A method for preparing the polypropylene compound according to any one of claims 1 to 5, characterized in that, Includes the following steps: Homopolymer polypropylene, itaconic acid, (4E)-4-octenedioic acid, nano zinc oxide, ethylene bis-stearamide and initiator are mixed; Alternatively, homopolymer polypropylene, itaconic acid, (4E)-4-octenedioic acid, nano zinc oxide, ethylene bis-stearamide, initiator and release agent can be mixed; The resulting mixture is melt-extruded and granulated to obtain the polypropylene injection molding material.

7. The preparation method according to claim 6, characterized in that, The temperature for melt extrusion granulation is 165~220℃.

8. The preparation method according to claim 6, characterized in that, The melt extrusion granulation is a six-zone temperature-controlled granulation; the temperatures of the six zones are sequentially 165~175℃, 188~192℃, 193~198℃, 199~203℃, 205~215℃ and 205~215℃.

9. A polypropylene gel needle, characterized in that, The polypropylene injection molding material prepared by any one of claims 1 to 5 or by any one of claims 6 to 8 is injection molded into a preform, and the preform is heated and softened and then stretched at high speed to obtain the final product.

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