Nucleating agent composition and application thereof

Abstract

The present application relates to the field of polypropylene modification, and specifically to a nucleating agent composition and its application. A nucleating agent composition comprises the following components in parts by weight: 10 parts of aluminum tripolyphosphate, 25-35 parts of lithium stearate, and 10-20 parts of an auxiliary agent; the auxiliary agent comprises at least one of aluminum borate and polyborosiloxane. In this application, aluminum borate or polyborosiloxane is added to the compound of aluminum tripolyphosphate and lithium stearate, thereby increasing the crystallization temperature and crystallization density of polypropylene and improving the flexural modulus of the material. In particular, polyborosiloxane is bonded to aluminum tripolyphosphate to form an "inorganic-organic hybrid network", which can further improve the flexural modulus. After the above-mentioned nucleating agent composition is added to polypropylene, the grain size is reduced, light scattering is reduced, and thus the haze is reduced.

Description

Technical Field

[0001] The present application relates to the field of polypropylene modification, and in particular to a nucleating agent composition and its application. Background Art

[0002] As one of the five most widely produced and consumed general-purpose plastics, polypropylene boasts advantages such as being non-toxic, low-cost, and easy to process. It is widely used in automotive parts, electronic appliances, building materials, medical devices, pipe packaging, and other fields. However, polypropylene is a semi-crystalline resin, and its applications are significantly limited by its slow crystallization rate, large spherulite size, and low rigidity.

[0003] In the prior art, the addition of nucleating agents is often used to effectively shorten the polypropylene molding cycle, refine the polypropylene grains, and increase crystallinity, thereby improving the flexural modulus of polypropylene. Common rigidity-enhancing nucleating agents on the market include sodium organophosphates and aluminum organophosphates, which are all effective in improving the flexural modulus of polypropylene. However, when these nucleating agents are added, excessive amounts of sodium organophosphates and aluminum organophosphates can cause aggregation, which in turn reduces the flexural modulus of polypropylene. Therefore, the flexural modulus of polypropylene added with rigidity-enhancing nucleating agents remains limited, making it difficult to meet the growing demand for rigidity. Summary of the Invention

[0004] In order to solve the problem of limited growth in the flexural modulus of polypropylene after adding a rigidity-enhancing nucleating agent, the present application provides a nucleating agent composition, in which lithium stearate is interspersed between aluminum tripolyphosphate molecules to inhibit their agglomeration and promote dissociation, thereby increasing the density of effective nucleation points; polyborosiloxane and aluminum tripolyphosphate form an "inorganic-organic hybrid network" to provide more heterogeneous nucleation sites; or aluminum borate is coordinated and connected with aluminum tripolyphosphate to enhance the stability of the nucleation sites; through the mutual cooperation among the three, the flexural modulus of polypropylene is better increased and the haze of polypropylene is reduced.

[0005] In a first aspect, the present application provides a nucleating agent composition, which adopts the following technical solution:

[0006] A nucleating agent composition comprises the following components in parts by weight: 10 parts of aluminum tripolyphosphate, 25-35 parts of lithium stearate, and 10-20 parts of an auxiliary agent; the auxiliary agent comprises at least one of aluminum borate and polyborosiloxane.

[0007] By adopting this technical solution, aluminum tripolyphosphate, due to its high aluminum ion charge density, tends to agglomerate in the polypropylene melt when added alone. However, lithium stearate, with its low lithium ion charge density, can intercalate between aluminum tripolyphosphate molecules, inhibiting agglomeration and promoting dissociation, thereby increasing the density of effective nucleation sites. Furthermore, aluminum tripolyphosphate provides a rigid framework in the polypropylene melt, and lithium stearate adsorbs onto the polypropylene to form a "pre-ordered structure," synergistically accelerating heterogeneous nucleation and reducing spherulite size.

[0008] Aluminum borate can form a coordination connection with the aluminum ions in aluminum tripolyphosphate through its aluminum-oxygen bond, strengthening the stability of the nucleation sites and promoting the uniform dispersion of lithium stearate in polypropylene. The boron element on the surface of polyborosiloxane can bond with the phosphate groups of aluminum tripolyphosphate to form an "inorganic-organic hybrid network", providing more heterogeneous nucleation sites.

[0009] This application adds aluminum borate or polyborosiloxane to a composite of aluminum tripolyphosphate and lithium stearate, raising the crystallization temperature and density of polypropylene, thereby improving the material's flexural modulus. In particular, the polyborosiloxane bonds with aluminum tripolyphosphate to form an "inorganic-organic hybrid network," further enhancing the flexural modulus. Adding this nucleating agent composition to polypropylene reduces grain size, reduces light scattering, and thus reduces haze.

[0010] Preferably, the auxiliary agent is polyborosiloxane.

[0011] By adopting this technical solution, compared to aluminum borate, the siloxy backbone of polyborosiloxane interacts with the polypropylene chains through hydrogen bonds, reducing phase separation and inhibiting agglomeration. Furthermore, the refractive index of the siloxy groups in polyborosiloxane is close to that of polypropylene, minimizing interfacial light refraction differences and further reducing haze. Therefore, the addition of polyborosiloxane is more effective than aluminum borate.

[0012] Preferably, the auxiliary agent is a mixture of aluminum borate and polyborosiloxane.

[0013] By adopting this technical solution, aluminum borate can form a coordinated connection with the aluminum ions in aluminum tripolyphosphate through its aluminum-oxygen bond, strengthening the stability of the nucleation sites and promoting the uniform dispersion of lithium stearate in polypropylene. The boron element on the surface of polyborosiloxane can bond with the phosphate groups of aluminum tripolyphosphate, forming an "inorganic-organic hybrid network" and providing more heterogeneous nucleation sites. When both are added to the nucleating agent composition, they can better bond with aluminum tripolyphosphate, providing more and more stable heterogeneous nucleation sites, thereby further improving the flexural modulus of polypropylene and reducing its haze.

[0014] Preferably, the mass ratio of polyborosiloxane to aluminum borate in the mixture is 1:0.3-0.5.

[0015] By adopting the above technical solution, when the proportion of aluminum borate is too low, the stability of the nucleation sites is not improved effectively, resulting in no significant improvement in the performance of polypropylene; when the proportion of aluminum borate is too high, the number of heterogeneous nucleation sites provided by polyborosiloxane and aluminum tripolyphosphate is insufficient, which also results in no significant improvement in the performance of polypropylene; for this reason, after extensive research and experimental verification, the applicant finally determined that the mass ratio of polyborosiloxane and aluminum borate in the mixture of the present application is preferably the above.

[0016] In a second aspect, the present application provides an application of a nucleating agent composition, using the following technical solution:

[0017] An application of a nucleating agent composition for polypropylene modification comprises the following steps:

[0018] Polypropylene, aluminum tripolyphosphate, lithium stearate and additives are mixed and kneaded, the mixture is harvested, and then extruded to obtain modified polypropylene.

[0019] Preferably, the application of the nucleating agent composition comprises the following steps: firstly mixing polypropylene and an auxiliary agent, then adding aluminum tripolyphosphate and lithium stearate and mixing, harvesting the mixture, and then extruding it to obtain modified polypropylene.

[0020] By adopting the above technical solution, polypropylene and the additive are first mixed, which helps to pre-disperse the additive in the polypropylene. Then, aluminum tripolyphosphate and lithium stearate are added. The additive can better combine with aluminum tripolyphosphate, thereby helping lithium stearate to intersperse between aluminum tripolyphosphate molecules, inhibiting their agglomeration and promoting dissociation, thereby increasing the effective nucleation point density, and making the modified polypropylene have a higher flexural modulus and lower haze.

[0021] Preferably, the application of the nucleating agent composition comprises the following steps: firstly mixing polypropylene, an additive and polyethylene wax, then adding aluminum tripolyphosphate and lithium stearate and mixing, harvesting the mixture, and then extruding it to obtain modified polypropylene.

[0022] By adopting the above technical solution, polypropylene, additives and polyethylene wax are first mixed. Polyethylene wax is a good dispersant, which helps the additives to be further dispersed in polypropylene, so that the modified polypropylene has a higher flexural modulus and lower haze.

[0023] In summary, this application has the following beneficial effects:

[0024] Because the present invention adds aluminum borate or polyborosiloxane to the composite of aluminum tripolyphosphate and lithium stearate, the crystallization temperature of polypropylene increases, the crystallization density increases, and the flexural modulus of the material is improved; in particular, the polyborosiloxane is bonded with aluminum tripolyphosphate to form an "inorganic-organic hybrid network", which can further improve the flexural modulus; after the above-mentioned nucleating agent composition is added to polypropylene, the grain size is reduced, light scattering is reduced, and thus the haze is reduced;

[0025] The auxiliary agent of the present application is preferably a mixture of polyborosiloxane and aluminum borate, because aluminum borate can enhance the stability of nucleation sites and promote the uniform dispersion of lithium stearate in polypropylene, and polyborosiloxane can provide more heterogeneous nucleation sites. The two work together to better increase the flexural modulus of polypropylene and reduce the haze of polypropylene. DETAILED DESCRIPTION

[0026] The raw materials in this application include the following parts:

[0027] Polypropylene: commercially available product with CAS number 9003-07-0 was used;

[0028] Aluminum tripolyphosphate: a commercially available product with CAS number 29196-72-3 is used;

[0029] Lithium stearate: a commercially available product with CAS number 4485-12-5;

[0030] Aluminum borate: a commercially available product with CAS number 11121-16-7 is used;

[0031] Polyborosiloxane: a commercially available product from Guangdong Wengjiang Chemical Reagent Co., Ltd.

[0032] Polyethylene wax: a commercially available product with CAS number 9002-88-4 is used;

[0033] The present application is further described in detail below with reference to examples and comparative examples. Example 1

[0034] An application of a nucleating agent composition comprises the following steps:

[0035] 1500g of polypropylene, 1g of aluminum tripolyphosphate, 3g of lithium stearate, and 1.5g of polyborosiloxane were mixed in a high-speed mixer for 10 minutes. The mixture was then extruded through a twin-screw extruder to produce modified polypropylene. The temperatures of the twin-screw extruder from the feed port to the die were 190°C, 210°C, 228°C, 242°C, 230°C, 210°C, and 200°C, respectively.

[0036] Example 2-3

[0037] In Example 2-3, based on the preparation method of Example 1, the content of each component of the modified polypropylene was adjusted. The specific adjustments are shown in Table 1.

[0038] Comparative Examples 1-3

[0039] Comparative Examples 1-3 are based on the preparation method of Example 1, except that the content of each component of the modified polypropylene is adjusted. The specific adjustments are shown in Table 1.

[0040] Table 1 Content and performance test table of each component of modified polypropylene of Examples 1-3 and Comparative Examples 1-3

[0041] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Polypropylene / g 1500 1500 1500 1500 1500 1500 Aluminum tripolyphosphate / g 1 1 1 / 1 1 Lithium stearate / g 3 2.5 3.5 3 / 3 Polyborosiloxane / g 1.5 1 2 1.5 1.5 / Flexural modulus / MPa 1627 1436 1593 1186 1237 1258 Haze / % 14.3 23.2 15.6 34.8 29.2 28.4

[0042] Performance testing

[0043] The modified polypropylene samples of Examples 1-3 and Comparative Examples 1-3 were subjected to the following performance tests. The test results are shown in Table 1.

[0044] 1. Flexural modulus

[0045] The modified polypropylene was prepared into specimens with a specification of 80 mm × 10 mm × 4 mm and tested according to the standard of GB / T9341-2008.

[0046] 2. Haze

[0047] The modified polypropylene was prepared into specimens with a specification of 50 mm×50 mm×1 mm and tested according to the standard of ASTM D1003-07.

[0048] As shown in Table 1, comparing Examples 1-3 with Comparative Examples 1-3, it can be seen that, compared with Comparative Example 1, the modified polypropylene in Example 1, which lacks the addition of aluminum tripolyphosphate, exhibits a lower flexural modulus and higher haze. This is likely due to the absence of aluminum tripolyphosphate, which lacks a rigid framework in the polypropylene melt. Furthermore, polyborosiloxane is unable to form an "inorganic-organic hybrid network" with aluminum tripolyphosphate, reducing the density of heterogeneous nucleation sites.

[0049] Comparing Example 1 with Comparative Example 2, it can be seen that the modified polypropylene without the addition of lithium stearate exhibits a lower flexural modulus and higher haze. This may be due to the absence of lithium stearate. ATP, due to its high charge density, tends to agglomerate in the polypropylene melt, reducing the density of heterogeneous nucleation sites.

[0050] Comparing Example 1 with Comparative Example 3, it can be seen that the modified polypropylene without the addition of polyborosiloxane exhibits a lower flexural modulus and higher haze. This is likely due to the absence of polyborosiloxane, which prevents it from forming an "inorganic-organic hybrid network" with aluminum tripolyphosphate, reducing the density of heterogeneous nucleation sites.

[0051] In addition, by comparing Examples 1-3, it is found that Example 1 has the best performance, so Example 1 is preferred.

[0052] Examples 4-5

[0053] Example 4 Based on the preparation method of Example 1, 1.5g of polyborosiloxane was replaced with 1.5g of aluminum borate.

[0054] Example 5 Based on the preparation method of Example 1, 1.5 g of polyborosiloxane was replaced with 1.5 g of a mixture of polyborosiloxane and aluminum borate, and the mass ratio of polyborosiloxane to aluminum borate in the mixture was 1:0.4.

[0055] The modified polypropylene samples of Examples 4-5 were subjected to the above performance tests. The test results are shown in Table 2.

[0056] Table 2 Types of additives and performance test table of Example 1 and Example 4-5

[0057] project Example 1 Example 4 Example 5 Types of additives Polyborosiloxane Aluminum borate Polyborosiloxane + aluminum borate Flexural modulus / MPa 1627 1604 1655 Haze / % 14.3 15.4 13.2

[0058] Referring to Table 2, it can be seen from the comparison between Example 1 and Examples 4-5 that the use of polyborosiloxane as an auxiliary agent will result in a higher flexural modulus and lower haze for the modified polypropylene prepared than with aluminum borate. The reason is that, compared to aluminum borate, the siloxy skeleton of polyborosiloxane interacts with the polypropylene chain through hydrogen bonds, reducing phase separation and inhibiting agglomeration. In addition, the refractive index of the siloxy group of polyborosiloxane is close to that of polypropylene, reducing the difference in interfacial light refraction and further reducing haze. Therefore, the effect of adding polyborosiloxane is better than that of aluminum borate.

[0059] The auxiliary agent is a mixture of polyborosiloxane and aluminum borate. Compared with adding either of them separately, the modified polypropylene prepared has a higher flexural modulus and lower haze. The reason is that aluminum borate can form a coordination connection with the aluminum ions in aluminum tripolyphosphate through its aluminum-oxygen bond, thereby strengthening the stability of the nucleation site and promoting the uniform dispersion of lithium stearate in polypropylene. The boron element on the surface of polyborosiloxane can bond with the phosphate group of aluminum tripolyphosphate to form an "inorganic-organic hybrid network" and provide more heterogeneous nucleation sites. When both are added to the nucleating agent composition at the same time, they can better bond with aluminum tripolyphosphate, provide more and more stable heterogeneous nucleation sites, thereby better increasing the flexural modulus of polypropylene and reducing the haze of polypropylene.

[0060] Examples 6-8

[0061] In Examples 6-8, based on the preparation method of Example 5, the mass ratio of polyborosiloxane to aluminum borate in the mixture was adjusted. The specific adjustments are shown in Table 3.

[0062] The modified polypropylene samples of Examples 6-8 were subjected to the above performance tests. The test results are shown in Table 3.

[0063] Table 3 Mass ratio and performance test table of polyborosiloxane and aluminum borate of Example 1 and Examples 5-8

[0064] project Example 1 Example 5 Example 6 Example 7 Example 8 Proportion / 1:0.4 1:0.2 1:0.3 1:0.5 Flexural modulus / MPa 1627 1655 1631 1642 1649 Haze / % 14.3 13.2 14.1 13.7 13.4

[0065] Referring to Table 3, a comparison of Example 1 and Examples 5-8 shows that as the proportion of aluminum borate increases, the flexural modulus of the modified polypropylene shows a trend of first increasing and then decreasing, while the haze shows a trend of first decreasing and then increasing. This is likely because as the proportion of aluminum borate increases, the stability of the nucleation sites improves, thereby increasing the flexural modulus of the modified polypropylene and reducing the haze of the modified polypropylene. When the proportion exceeds a certain range, the "inorganic-organic hybrid network" formed by polyborosiloxane and aluminum tripolyphosphate is affected, reducing the number of heterogeneous nucleation sites, and in turn reducing the flexural modulus of the modified polypropylene and increasing the haze of the modified polypropylene.

[0066] Examples 9-10

[0067] Example 9 Based on the preparation method of Example 1, 1500 g of polypropylene and 1.5 g of polyborosiloxane were mixed in a high-speed mixer for 3 min, and then 1 g of aluminum tripolyphosphate and 3 g of lithium stearate were added to the high-speed mixer and mixed for 7 min. The mixture was then extruded through a twin-screw extruder to obtain modified polypropylene.

[0068] Example 10 Based on the preparation method of Example 1, 1500 g of polypropylene, 1.5 g of polyborosiloxane and 0.5 g of polyethylene wax were mixed in a high-speed mixer for 3 min, and then 1 g of aluminum tripolyphosphate and 3 g of lithium stearate were added to the high-speed mixer and mixing was continued for 7 min. The mixture was then extruded through a twin-screw extruder to obtain modified polypropylene.

[0069] The modified polypropylene samples of Examples 9-10 were subjected to the above performance tests, and the test results are shown in Table 4.

[0070] Table 4 Performance test table of Example 1 and Examples 9-10

[0071] project Example 1 Example 9 Example 10 Whether two-step mixing / yes yes Whether to add polyethylene wax / / yes Flexural modulus / MPa 1627 1635 1644 Haze / % 14.3 13.9 13.7

[0072] Referring to Table 4, by comparing Example 1 with Examples 9-10, it can be seen that mixing the polypropylene and polyborosiloxane first helps to pre-disperse the polyborosiloxane in the polypropylene, and then adding aluminum tripolyphosphate and lithium stearate. The polyborosiloxane can better combine with the aluminum tripolyphosphate, thereby helping the lithium stearate to intercalate between the aluminum tripolyphosphate molecules, inhibiting their agglomeration and promoting dissociation, thereby increasing the effective nucleation point density, and making the modified polypropylene have a higher flexural modulus and lower haze.

[0073] Polypropylene, polyborosiloxane and polyethylene wax are first mixed, and the polyethylene wax helps the polyborosiloxane to be further dispersed in the polypropylene, so that the modified polypropylene has a higher flexural modulus and lower haze.

[0074] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A nucleating agent composition, characterized in that The invention comprises the following components in parts by weight: 10 parts of aluminum tripolyphosphate, 25-35 parts of lithium stearate, and 10-20 parts of an auxiliary agent; the auxiliary agent comprises at least one of aluminum borate and polyborosiloxane.

2. The nucleating agent composition according to claim 1, characterized in that: The auxiliary agent is polyborosiloxane.

3. The nucleating agent composition according to claim 1, characterized in that: The auxiliary agent is a mixture of aluminum borate and polyborosiloxane.

4. The nucleating agent composition according to claim 3, characterized in that: The mass ratio of polyborosiloxane to aluminum borate in the mixture is 1:0.3-0.

5.

5. A use of the nucleating agent composition according to any one of claims 1 to 4, characterized in that: It is used in polypropylene modification.

6. The use of the nucleating agent composition according to claim 5, characterized in that: The method comprises the following steps: mixing polypropylene, aluminum tripolyphosphate, lithium stearate and an auxiliary agent, harvesting the mixture, and then extruding the mixture to obtain modified polypropylene.

7. The use of the nucleating agent composition according to claim 6, characterized in that: The method comprises the following steps: mixing polypropylene and an auxiliary agent first, then adding aluminum tripolyphosphate and lithium stearate and mixing, harvesting the mixture, and then extruding the mixture to obtain the modified polypropylene.

8. The use of the nucleating agent composition according to claim 6, characterized in that: The method comprises the following steps: firstly mixing polypropylene, an auxiliary agent and polyethylene wax, then adding aluminum tripolyphosphate and lithium stearate and mixing, harvesting the mixture, and then extruding the mixture to obtain modified polypropylene.