WO2024114482A1

WO2024114482A1 - Polypropylene composition and preparation method therefor

Info

Publication number: WO2024114482A1
Application number: PCT/CN2023/133451
Authority: WO
Inventors: 唐宇航; 陈平绪; 叶南飚; 陈嘉杰; 钱志军; 郭唐华
Original assignee: 金发科技股份有限公司
Priority date: 2022-11-30
Filing date: 2023-11-22
Publication date: 2024-06-06
Also published as: CN115716961A; CN115716961B

Abstract

The present invention relates to the technical field of high polymer materials. Disclosed are a polypropylene composition and a preparation method therefor. According to the polypropylene composition in the present invention, a cellulose nanofibril having a specific length-diameter ratio is selected to match a maleic anhydride grafted polypropylene modifier having a high grafting rate as components, so that the compatibility of the cellulose nanofibril and a polypropylene resin matrix is remarkably improved; in addition, the cellulose nanofibril has good dispersion in product components, so that the paint adhesion of the product is improved, the damage of the outside to the surface of the product can be effectively resisted, and the scratch resistance of the product is improved. Also disclosed in the present invention are a preparation method for the polypropylene composition and a use of the polypropylene composition in the preparation of automobile plastic parts.

Description

A polypropylene composition and preparation method thereof

Technical Field

The invention relates to the technical field of polymer materials, and in particular to a polypropylene composition and a preparation method thereof.

Background technique

Polypropylene (PP) is one of the five most common thermoplastics in the industry. It is widely used in various industries such as home appliances, packaging, and automobiles due to its balanced performance and high cost-effectiveness. However, the surface hardness and surface tension of general polypropylene products are low, which makes it easy to scratch the surface when touched by hard objects. At the same time, the paint matching is poor, and additional treatments (such as flame treatment, etc.) are required, which increases the production cost.

Cellulose nanofiber (CNF), as one of the fiber reinforcement products, has gradually entered the field of vision of automotive material selection due to its easy availability, low carbon emissions and high stiffness. At present, it is not uncommon to use cellulose nanofiber as a reinforcing component for the preparation of high-rigidity polypropylene products. However, the addition of general cellulose nanofibers cannot improve the scratch resistance of polypropylene products. On the other hand, the polyhydroxyl groups on the surface of cellulose nanofibers cause the solubility parameters of cellulose nanofibers to be mismatched with those of polypropylene resin, and the compatibility and dispersibility after processing are low, which makes it easy for the main body of the product to be delaminated, interface defects and low mechanical properties. The realization of high paint adhesion of polypropylene products requires good dispersibility and bonding between the various material components.

Summary of the invention

Based on the defects of the prior art, the purpose of the present invention is to provide a polypropylene composition, which selects cellulose nanofibers with a specific aspect ratio and a maleic anhydride grafted polypropylene modifier with a high grafting rate as components, so that the compatibility of the cellulose nanofibers with the polypropylene resin matrix is significantly improved. At the same time, the cellulose nanofibers have a good dispersion scale in the product components, which not only improves the paint adhesion of the product, but also can effectively resist external damage to the product surface, thereby improving the scratch resistance of the product.

In order to achieve the above object, the technical solution adopted by the present invention is:

A polypropylene composition comprising the following components in parts by weight:

55-90 parts of polypropylene resin, 5-30 parts of cellulose nanofibers, 5-10 parts of maleic anhydride grafted polypropylene and 0.4-2 parts of processing aid;

The average single-filament aspect ratio of the cellulose nanofiber is 90-220, and the crystallinity is ≥80%; the grafting rate of the maleic anhydride grafted polypropylene is 2-2.5%.

Preferably, the crystallinity of the cellulose nanofibers is 80-90%.

In general, due to the poor size distribution of existing cellulose nanofibers and the presence of more hydroxyl groups on the surface, when used as a reinforcing component, it is not only impossible to provide effective surface hardness for the product, but it will cause the compatibility of the components of the product to deteriorate, and the paint adhesion of the product is reduced; in the prior art, a solubilizing agent is also used to improve the compatibility of cellulose nanofibers in a polypropylene resin matrix, but based on the generally small size of cellulose nanofibers (much lower than other reinforcing fillers), the actual improvement effect is very limited. In the polypropylene composition of the present invention, the inventors have preferably selected cellulose nanofibers with a special aspect ratio to first improve the degree of dispersion and arrangement sequence in the polypropylene resin at a physical level, so that it can be effectively distributed on the surface of the product to resist external collisions, and at the same time, maleic anhydride grafted polypropylene with a high grafting rate is used as a modified component to synergize with cellulose nanofibers, and the compatibility of the overall product is improved, and its surface hardness is further improved, and the adhesion of the paint is also significantly increased. However, if the grafting rate of maleic anhydride grafted polypropylene is too high, exceeding 2.5%, a large amount of free monomer will inevitably appear in the product. The content of the monomer will increase nonlinearly, and the performance of the processed product will decay, and the expected effect will also fail to be achieved.

The grafting rate of maleic anhydride grafted polypropylene is referred to "Preparation of High Grafting Rate Polypropylene Grafted Maleic Anhydride" - "Plastic Industry" 2018, and can be confirmed by the following method: 0.5g sample is mixed with 50mL xylene and heated until completely dissolved, then N, N-dimethylformamide is dripped into it to dissolve evenly, and then a small amount of water is added in batches to stir evenly, and phenolphthalein solution is dripped into it, and a methanol solution of potassium hydroxide with a molar concentration of 0.045mol/L (titration solution) is used for titration until the solution turns red and does not fade for 30s, which is the end point; at the same time, a blank sample without grafting is set for the same test, and the grafting rate GD (%) is calculated according to the following formula:

Where C is 0.045 mol/L, _V1 is the volume of the titrant used to titrate the blank sample (mL), _V2 is the volume of the titrant used to titrate the sample (mL), and m is the sample mass, 0.5 g.

It should be noted that, in the product of the present invention, whether it is a commercial maleic anhydride grafted polypropylene purchased directly or a self-made maleic anhydride grafted polypropylene product, the above method or other methods known to those skilled in the art can be selected according to actual conditions to test and verify the grafting rate, so as to select an accurate A method with higher accuracy and simpler operation is implemented.

In addition, the inventors have found through experiments that the crystallinity of cellulose nanofibers also affects the scratch resistance and paint adhesion of the product. If the crystallinity is low, it is likely to weaken the two properties of the product.

Preferably, the cellulose nanofibers have an average monofilament diameter of 3 to 8 nm and an average length of 600 to 800 nm.

The test method for the monofilament diameter and length of the cellulose nanofiber in the components of the polypropylene composition of the present invention is as follows: the polypropylene composition is soaked in a xylene solution at 80°C for 4h, and the remaining solid is filtered and dried and then measured by the following method: Length test, take about 0.5-1g of the dried product solid with tweezers, use a surface dish with a diameter of 100mm for loading, add distilled water to the surface dish until the sample is immersed on the surface, gently shake the cellulose to slightly disperse, and finally use a microscope to statistically observe the fiber length, with a magnification of 2000. Diameter test, using SEM electronic scanning electron microscope, take the particle interface for gold spraying and electron microscope observation to calculate the fiber diameter. At the same time, the crystallinity of the cellulose nanofiber can be directly tested and characterized by X-ray diffraction method (according to the general method, the cellulose nanofiber is placed in an X-ray diffractometer to test and obtain a scanning curve, and the crystallinity Cr is calculated according to Cr=(I-Iam)×100%/I based on the maximum intensity I of the characteristic peak lattice diffraction and the scattering intensity Iam of the non-crystalline background diffraction).

For cellulose nanofibers, the aspect ratio determines their distribution order in polypropylene resin. When the aspect ratio of cellulose nanofibers is too small, their nano characteristics are more obvious, and the degree of improvement in the product's scratch resistance is more limited. When the aspect ratio is too large, the processing difficulty of the product increases, the dispersion of the product's components deteriorates, and the yield decreases. On the other hand, if the size of the cellulose nanofibers themselves is large or small, it is also difficult to achieve the ideal technical effect.

Preferably, the polypropylene resin is a copolymer polypropylene resin, and the melt mass flow rate of the copolymer polypropylene resin at 230°C and 2.16kg load according to ISO1133-2011 is 1-100g/10min; more preferably, the melt mass flow rate of the copolymer polypropylene resin at 230°C and 2.16kg load is 5-95g/10min.

Preferably, the processing aid is at least one of an antioxidant and a lubricant.

More preferably, the antioxidant is a mixture of a hindered phenol antioxidant and a phosphite antioxidant, and the mass ratio of the two is (0.8-1.2):(0.8-1.2).

Preferably, the lubricant is at least one of oleamide, erucamide, zinc stearate and calcium stearate.

Preferably, the polypropylene composition also includes 0 to 1 part of color powder.

According to the actual color matching requirements of the product, those skilled in the art may add a certain amount of color powder to the product, and this component will basically not cause changes in the performance of the product.

More preferably, the toner is at least one of titanium white, carbon black, phthalocyanine blue, azo red, and phthalocyanine purple red.

Another object of the present invention is to provide a method for preparing the polypropylene composition, comprising the following steps:

The components are placed in a twin-screw extruder for mixing and heating for melt extrusion to obtain the polypropylene composition.

The preparation method of the product of the present invention has simple operation steps and can realize industrial-scale production.

Preferably, the heating temperature of the twin-screw extruder during the heating and melt extrusion process is set to 190-210° C., and the screw speed is set to 800-850 rpm.

Another object of the present invention is to provide application of the polypropylene composition in the preparation of automobile plastic parts.

Preferably, the automobile plastic parts include automobile door trim panels, spare tire covers, and seat guard panels.

Among existing reinforced polypropylene materials, cellulose nanofiber reinforced polypropylene materials have a larger usage share than other finished products due to their high rigidity and high production cost performance, but people currently pay less attention to their actual key performance when used in decorative shells, especially in the field of automotive plastic parts: scratch resistance and paint adhesion, resulting in such products often being prone to scratches and serious paint loss after use. The polypropylene composition of the present invention retains cellulose nanofibers as a reinforcing component while having good scratch resistance and high paint adhesion. In the scratch resistance test, the product surface color difference change △L after testing with a load of 10N is no more than 1.5, and the paint adhesion in the paint adhesion test is much higher than that of ordinary polypropylene products, which is very suitable for the field of automotive plastic parts.

The beneficial effect of the present invention is that the present invention provides a polypropylene composition, which selects cellulose nanofibers with a specific aspect ratio and a maleic anhydride grafted polypropylene modifier with a high grafting rate as components, so that the compatibility of the cellulose nanofibers with the polypropylene resin matrix is significantly improved, and the cellulose nanofibers have a good dispersion scale in the product components, which not only improves the paint adhesion of the product, but also can effectively resist external damage to the product surface, and improve the scratch resistance of the product.

Detailed ways

In order to better illustrate the purpose, technical solutions and advantages of the present invention, the following will be combined with specific embodiments The present invention is further described in the following examples and comparative examples, which are intended to provide a detailed understanding of the present invention rather than to limit the present invention. All other embodiments obtained by a person of ordinary skill in the art without creative work are within the scope of protection of the present invention. The experimental reagents and instruments involved in the implementation of the present invention are all commonly used ordinary reagents and instruments unless otherwise specified.

Examples 1 to 8

The embodiments of the polypropylene composition and the preparation method thereof of the present invention, the components of the polypropylene composition are shown in Table 1.

The method for preparing the polypropylene composition comprises the following steps:

The components except the cellulose nanofibers are simultaneously placed into a twin-screw extruder from a main feeding port and the cellulose nanofibers are simultaneously placed into a twin-screw extruder from a side feeding port for mixing and heating and melting and extruding to obtain the polypropylene composition.

The heating temperature of the twin-screw extruder during the heating and melting extrusion process is set to 190-210° C., and the screw speed is set to 800-850 rpm.

Comparative Examples 1 to 8

The difference between the comparative examples and the embodiments is only in the types and proportions of components, as shown in Table 2.

Among the components described in each embodiment and comparative example,

Polypropylene resin 1 is PP EP300M produced by CNOOC Shell, and the melt mass flow rate is 8 g/10 min at 230°C and 2.16 kg load.

Polypropylene resin 2 is PP EP640V produced by CNOOC Shell, and the melt mass flow rate is 95 g/10 min at 230°C and 2.16 kg load.

The cellulose nanofiber 1 is FLCF-DRY produced by Osaka Gas, with an average single fiber diameter of 8 nm, an average length of 800 nm, an average aspect ratio of 100, and a crystallinity of 82%. The crystallinity of each example after the product is prepared is 82-84%.

Cellulose nanofiber 2 is a product of the NCCel series produced by Northern Century, with an average monofilament diameter of 3nm, an average length of 600nm, an average aspect ratio of 200, and a crystallinity of 88%. The crystallinity of the products prepared in each embodiment and comparative example is 87-90%

Cellulose nanofiber 3 is a CNF series product produced by Shengquan Group, with an average monofilament diameter of 10nm, an average length of 1000nm, an average aspect ratio of 100, and a crystallinity of 85%. The crystallinity of the product after preparation is 86-87%.

Cellulose nanofiber 4 is the ELLEX series product produced by Daio Paper, Japan, with an average monofilament diameter of 2nm, average length is 200nm, average aspect ratio is 200, and crystallinity is 86%. The crystallinity of the product after preparation is 87-88%

Cellulose nanofiber 5 is a BFDP series product produced by SUGINO Machinery, with an average monofilament diameter of 5nm, an average length of 500nm, an average aspect ratio of 100, and a crystallinity of 76%. The crystallinity of the comparative example after preparation is 76-78%

Cellulose nanofiber 6 is a NBKP series product produced by Ehime Paper Co., Ltd. of Japan, with an average monofilament diameter of 25 nm, an average length of 1500 nm, an average aspect ratio of 60, and a crystallinity of 75%. The crystallinity of the comparative example after preparation is 74-76%

Cellulose nanofiber 7 is a FC series product produced by Daicel Japan, with an average monofilament diameter of 6nm, an average length of 1800nm, an average aspect ratio of 300, and a crystallinity of 85%. The crystallinity of the comparative example after preparation is 86-87%

Maleic anhydride grafted polypropylene 1: Polyram produces Bondyram 1201 with a grafting rate of 2%.

Maleic anhydride grafted polypropylene 2: MB25 produced by Kingfa Technology, with a grafting rate of 2.5%.

Maleic anhydride grafted polypropylene 3: T5001-G produced by Jiayirong, with a grafting rate of 1%.

Maleic anhydride grafted polypropylene 4: Dow Chemical produces MGP-3 with a grafting rate of 3%.

Antioxidant: A mixture of commercially available hindered phenol antioxidants and commercially available phosphite antioxidants, with the mass ratio of the two being 1:1.

Lubricant: Commercially available erucamide.

Toner: Commercially available carbon black.

Unless otherwise specified, the components and raw materials used in the embodiments and comparative examples of the present invention are all commercially available raw materials, and the components and raw materials used in each parallel experiment are all of the same kind.

It should also be noted that the monofilament diameter and length of the cellulose nanofibers were tested after the treatment of the products of each embodiment and comparative example. It was found that the maximum size change rate of the cellulose nanofibers in the product components before and after the preparation of the preparation method of the present invention did not exceed 5%. Therefore, it is believed that the monofilament diameter, length and aspect ratio of the cellulose nanofibers in the prepared product are basically unchanged compared with the raw material. At the same time, the crystallinity of the cellulose nanofibers in the product was tested and parallel statistics were performed (to ensure accuracy, 5 groups of products were prepared in parallel for each embodiment and comparative example and the crystallinity of the cellulose nanofibers in the product was tested and statistics were performed). The results are as described above. It can be seen that the crystallinity of the cellulose nanofibers 1 to 7 used in the present invention has almost no change before and after the product preparation, and the comprehensive change rate does not exceed 5%, and the amplitude does not exceed 3%. Therefore, it can be considered that the crystallinity of the cellulose nanofibers in the prepared product is basically unchanged. Table 1

Table 2

Effect Example 1

In order to verify the performance of the polypropylene material of the present invention, the products of each embodiment and comparative example were subjected to the following performance tests, and the specific steps are as follows:

(1) Scratch resistance test: The test was performed according to Volkswagen PV3952 standard. The products of each embodiment and comparative example were injection molded into Ford Stucco leather grain plates and conditioned under standard conditions for 48 hours and placed on an Erichsen model 430 cross scratch resistance tester. The scratch test was performed at 23±5°C to scratch a grid of at least 40*40mm. Among them, the contact force F=10N, the scratching speed V=1000mm/min, the cross scratching grid side length was 2mm, and the scratching gouge had a diameter of 1mm. After scratching the product, a colorimeter was used to obtain the test value ΔL (brightness change), and the test value was used for evaluation (test value=the average value obtained after 5 measurements of each value). The illumination during measurement was D65/10 degrees, and the diameter of the measurement area was greater than or equal to 7mm.

(2) Each product was injection molded into a 100*100*3 mm sample and allowed to stand for 24 h. The surface was then wiped with isopropyl alcohol and then sprayed with Kansai water-based primer ASX-3807CD. After spraying, the paint adhesion test was performed according to M0141-2016.

The test results are shown in Tables 3 and 4.

table 3

Table 4

It can be seen from Tables 3 and 4 that the products of each embodiment have good scratch resistance and paint adhesion, wherein the scratch resistance △L of each product can be maintained at ≤1.5, and the paint adhesion can reach 850N and above. From the comparison of the products of Examples 4 to 7, it can be seen that when the monofilament aspect ratio of the cellulose nanofibers is similar, its size itself will also affect the scratch resistance and paint adhesion of the product. The comprehensive performance of the product is best when the average monofilament diameter of the cellulose nanofibers in the component is 3 to 8nm and the average length is 600 to 800nm; in contrast, the performance of the products of each comparative example cannot reach the use index, wherein the product of Comparative Example 2 introduces cellulose nanofibers compared to the product of Comparative Example 1, but does not contain maleic anhydride grafted polypropylene, and the scratch resistance and paint adhesion improvement effect of the product are very limited; although the products of Comparative Examples 3 to 5 contain both cellulose nanofibers and maleic anhydride grafted polypropylene, the product performance is poor because the crystallinity and/or monofilament aspect ratio of the cellulose nanofibers are not within the specified range; the products of Comparative Examples 6 to 7 contain maleic anhydride grafted polypropylene. If the grafting rate of maleic anhydride grafted polypropylene is too high or too low, the product cannot reach the performance level of the example product. Even if large-sized cellulose nanofibers are further compounded with maleic anhydride grafted polypropylene with a low grafting rate, the product of comparative example 8 still does not achieve a good scratch resistance effect.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

A polypropylene composition, characterized in that it comprises the following components in parts by weight:

55-90 parts of polypropylene resin, 5-30 parts of cellulose nanofibers, 5-10 parts of maleic anhydride grafted polypropylene and 0.4-2 parts of processing aid;

The average single-filament aspect ratio of the cellulose nanofiber is 90-220, and the crystallinity is ≥80%; the grafting rate of the maleic anhydride grafted polypropylene is 2-2.5%.
The polypropylene composition according to claim 1 is characterized in that the average monofilament diameter of the cellulose nanofibers is 3 to 8 nm and the average length is 600 to 800 nm.
The polypropylene composition according to claim 1, wherein the cellulose nanofibers have a crystallinity of 80 to 90%.
The polypropylene composition according to claim 1, characterized in that the polypropylene resin is a copolymer polypropylene resin, and the melt mass flow rate of the copolymer polypropylene resin at 230°C and a load of 2.16 kg is 1 to 100 g/10 min; preferably, the melt mass flow rate of the copolymer polypropylene resin at 230°C and a load of 2.16 kg is 5 to 95 g/10 min.
The polypropylene composition according to claim 1, characterized in that the processing aid is at least one of an antioxidant and a lubricant.
The polypropylene composition as claimed in claim 1 is characterized in that the antioxidant is a mixture of a hindered phenol antioxidant and a phosphite antioxidant, and the mass ratio of the two is (0.8-1.2): (0.8-1.2); the lubricant is at least one of oleamide, erucamide, zinc stearate, and calcium stearate.
The polypropylene composition according to claim 1 is characterized in that the components of the polypropylene composition also include 0 to 1 parts of color powder; the color powder is at least one of titanium white, carbon black, phthalocyanine blue, azo red, and phthalocyanine purple red.
The method for preparing the polypropylene composition according to any one of claims 1 to 7, characterized in that it comprises the following steps:

The components are placed in a twin-screw extruder for mixing and heating for melt extrusion to obtain the polypropylene composition.
The method for preparing a polypropylene composition as claimed in claim 8, characterized in that the heating temperature of the twin-screw extruder during the heating and melt extrusion process is set to 190-210°C, and the screw speed is set to 800-850rpm.
Use of the polypropylene composition according to any one of claims 1 to 7 in the preparation of automotive plastic parts.