A nucleating agent composition containing 3,4-dimethylbenzylidene sorbitol and a preparation method thereof

Abstract

The present invention relates to the technical field of nucleating agents, and in particular to a composition containing a 3,4-dimethylbenzylidene sorbitol nucleating agent and a preparation method thereof. The composition comprises a stearic acid-modified molecular sieve, hydrogenated styrene-butadiene rubber and a 3,4-dimethylbenzylidene sorbitol nucleating agent. When the composition of the present invention is used in polypropylene, it can not only increase the transparency of polypropylene, but also increase the toughness of polypropylene, and increase its low-temperature toughness to a certain extent.

Description

Technical Field

[0001] The invention relates to the technical field of nucleating agents, and in particular to a nucleating agent composition containing 3,4-dimethylbenzylidene sorbitol and a preparation method thereof. Background Art

[0002] Polypropylene nucleating agent is a polymer material additive used to increase the crystallinity of incompletely crystalline resin materials such as polypropylene (PP) and accelerate its crystallization rate. This additive can significantly improve the optical and mechanical properties of polypropylene products, enhance the visibility and aesthetics of the products, and enhance their rigidity or impact resistance. In other words, polypropylene nucleating agent is an indispensable and important additive in the polypropylene processing process. By selecting the appropriate type and brand of nucleating agent and optimizing the processing conditions, the performance and quality of polypropylene products can be significantly improved to meet the ever-changing needs of the market.

[0003] 3,4-Dimethylbenzylidene sorbitol nucleating agent, also known as DMDBS or nucleating agent 3988, is the third generation product of dibenzylidene sorbitol (DBS). It performs well in the field of clarifiers, has excellent haze and finish, and can effectively improve scaling and odor problems. This nucleating agent is suitable for various processing techniques, has high dispersion and nucleation efficiency, and is recognized as representing a new level of development of world clarifiers.

[0004] 3,4-Dimethylbenzylidene sorbitol nucleating agent belongs to α nucleating agent. Although α nucleating agent can improve the crystal morphology and mechanical properties of polypropylene products, as the content of α nucleating agent increases, although the crystal morphology remains unchanged, the spherulite size decreases, the α crystal crystallinity increases, and the tensile strength of the product increases, the impact strength decreases. In addition, the use of α nucleating agent alone may not give full play to its optimal effect. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects in the prior art that single 3,4-dimethylbenzylidene sorbitol cannot fully exert its optimal effect and reduces the impact strength of polypropylene products, and to provide a nucleating agent composition containing 3,4-dimethylbenzylidene sorbitol and a preparation method thereof.

[0006] In order to achieve the above object, the first aspect of the present invention provides a 3,4-dimethylbenzylidene sorbitol nucleating agent composition, which comprises stearic acid modified molecular sieve, hydrogenated styrene butadiene rubber and 3,4-dimethylbenzylidene sorbitol nucleating agent.

[0007] As a preferred technical solution of the present invention, the weight ratio of the stearic acid modified molecular sieve to the hydrogenated styrene butadiene rubber is 20-50:100, for example, 20:100, 25:100, 30:100, 35:100, 40:100, 45:100, 50:100, preferably 25-30:100.

[0008] As a preferred technical solution of the present invention, the weight ratio of the 3,4-dimethylbenzylidene sorbitol nucleating agent to the hydrogenated styrene butadiene rubber is 30-60:100, for example, 30:100, 35:100, 40:100, 45:100, 50:100, 55:100, 60:100, preferably 40-45:100.

[0009] 3,4-dimethylbenzylidene sorbitol nucleating agent is an α-nucleating agent. Although it can increase the rigidity of polypropylene to a certain extent, it cannot increase the toughness of polypropylene well. The inventors of the present invention have found through research that the composition of the present invention containing stearic acid modified molecular sieve, hydrogenated styrene butadiene rubber and 3,4-dimethylbenzylidene sorbitol nucleating agent acts on polypropylene together, and the ratio between each component is controlled at the same time, which can increase the rigidity and toughness of polypropylene at the same time, so that a balanced effect is achieved. This may be because the stearic acid modified molecular sieve can be evenly dispersed in the polypropylene system to play a role in toughening and strengthening.

[0010] As a preferred technical solution of the present invention, the average particle size of the hydrogenated styrene butadiene rubber is 60-80 meshes.

[0011] The hydrogenated styrene butadiene rubber in the present invention can be obtained commercially, preferably purchased from Shenzhen Wansuyuan Rubber & Plastic Co., Ltd., with the brand name PNBR-830.

[0012] In the present invention, further research found that the addition of hydrogenated styrene butadiene rubber can not only synergistically increase the toughness of polypropylene with stearic acid-modified molecular sieves and hydrogenated styrene butadiene rubber, but also further increase its low-temperature toughness. The inventors speculate that in a low-temperature environment, the chain segments in the hydrogenated styrene butadiene rubber have a certain flexibility and can move freely. When subjected to external impact, the system can absorb more capacity.

[0013] As a preferred technical solution of the present invention, the preparation method of the stearic acid modified molecular sieve comprises:

[0014] (1) etching the acidic molecular sieve with alkali, filtering it, and washing it with water for multiple times until the filtrate is neutral to obtain a modified molecular sieve;

[0015] (2) The modified molecular sieve, water and stearic acid are mixed and heated for reaction, followed by centrifugation and solid drying to obtain the stearic acid modified molecular sieve.

[0016] The inventors of the present invention have found that when an acidic molecular sieve is alkali-etched and then modified with stearic acid, the light transmittance of polypropylene can be better increased. On the one hand, this may be because the stearic acid-modified molecular sieve can be well dispersed in the polypropylene system, and the molecular sieve can act as a nucleating agent to refine the grain size of polypropylene and increase the number of polypropylene crystallites; on the other hand, the molecular sieve after alkali etching has special pores, which allows light to better penetrate the polypropylene product.

[0017] In the present invention, in order to form molecular sieve channels that are more conducive to light transmission, as a preferred technical solution of the present invention, the alkali etching method is: an alkaline aqueous solution of N,N-diisopropylethylamine with a concentration of 0.01-0.05 mol / L and triethylamine with a concentration of 0.1-0.2 mol / L is stirred with an acidic molecular sieve at 65-70°C for 5-7 hours.

[0018] As a more preferred embodiment of the present invention, the weight ratio of the alkaline aqueous solution to the acidic molecular sieve is 100:8-20, preferably 100:10-15.

[0019] As a more preferred embodiment of the present invention, the molar ratio of silicon to aluminum of the acidic molecular sieve is 30-300, preferably 50-80, and more preferably 70.

[0020] As a more preferred embodiment of the present invention, the D50 particle size of the acidic molecular sieve is 2-6 microns, preferably 4 microns.

[0021] The acidic molecular sieve is at least one selected from h-beta molecular sieve, ZSM-S molecular sieve, SBA-15 molecular sieve and HY molecular sieve, preferably h-beta molecular sieve.

[0022] The acidic molecular sieve in the present invention can be obtained commercially, for example, h-beta molecular sieve is purchased from Zhuoran Environmental Protection Technology (Dalian) Co., Ltd., with a silicon-aluminum molar ratio of 70 and a D50 particle size of 4 microns.

[0023] As a preferred technical solution of the present invention, in step (2), the weight ratio of the modified molecular sieve, water and stearic acid is 30-50:100:0.5-1.

[0024] As a preferred technical solution of the present invention, in step (2), the heating reaction conditions are: stirring the reaction at 80-90° C. for 1-2 hours.

[0025] In the present invention, in step (2), the solid is dried in a conventional manner in the art, preferably at 110-120° C. to a constant weight.

[0026] The second aspect of the present invention provides a method for preparing the composition containing 3,4-dimethylbenzylidene sorbitol nucleating agent according to the first aspect of the present invention, the preparation method comprising: mixing and grinding stearic acid modified molecular sieve, hydrogenated styrene butadiene rubber and 3,4-dimethylbenzylidene sorbitol nucleating agent in a ball mill, and then mixing them in a two-dimensional mixer to obtain.

[0027] As a preferred technical solution of the present invention, the mixed grinding conditions are: ball milling at a rotation speed of 400-600 rpm for 4-6 hours, and the diameter of the grinding balls is 5 mm.

[0028] As a preferred technical solution of the present invention, the mixing time in the two-dimensional mixer is 20-40 minutes.

[0029] The composition of the present invention can be used in polypropylene, and is particularly suitable for toughening homopolypropylene, and its usage is generally 0.5-3% by weight.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] 1. Compared with a single 3,4-dimethylbenzylidene sorbitol nucleating agent, the synergistic effect between the compositions of the present invention can better improve the transparency of polypropylene.

[0032] 2. The synergistic effect between the various components in the composition of the present invention can overcome the defect that a single 3,4-dimethylbenzylidene sorbitol nucleating agent cannot improve the toughness of polypropylene well, and can better increase the toughness of polypropylene.

[0033] 3. The various components in the present invention work synergistically with each other, especially the hydrogenated styrene-butadiene rubber and the stearic acid-modified molecular sieve, which can not only further increase the toughness of polypropylene, but also increase the low temperature resistance of polypropylene to a certain extent. DETAILED DESCRIPTION

[0034] The present invention is described in detail below through examples. The following examples are only illustrative of the specific technical solutions of the present invention and do not limit the scope of the present invention. That is, it should be understood that non-essential simple corrections, adjustments and combinations made by those skilled in the art based on the inventive concept of the present invention are all within the scope of protection claimed by the present invention.

[0035] In the following examples, unless otherwise specified, all raw materials are commercially available. Example

[0036] This embodiment provides a composition containing a 3,4-dimethylbenzylidene sorbitol nucleating agent, the composition is a stearic acid modified molecular sieve, hydrogenated styrene-butadiene rubber and a 3,4-dimethylbenzylidene sorbitol nucleating agent;

[0037] The weight ratio of stearic acid modified molecular sieve to hydrogenated styrene butadiene rubber is 28:100;

[0038] The weight ratio of 3,4-dimethylbenzylidene sorbitol nucleating agent to hydrogenated styrene butadiene rubber is 42:100;

[0039] Hydrogenated styrene butadiene rubber was purchased from Shenzhen Wansuyuan Rubber & Plastic Co., Ltd., with the brand name PNBR-830 ​​and an average particle size of 70 mesh;

[0040] The preparation method of stearic acid modified molecular sieve is as follows: (1) stirring an alkaline aqueous solution of N,N-diisopropylethylamine with a concentration of 0.03 mol / L and triethylamine with a concentration of 0.15 mol / L with an acidic molecular sieve at 70°C for 6 hours for alkaline etching, then filtering, and washing with water for multiple times until the filtrate is neutral to obtain a modified molecular sieve; (2) mixing the modified molecular sieve, water, and stearic acid, and heating the mixture for reaction, then centrifuging, and drying the solid to obtain the stearic acid modified molecular sieve;

[0041] In step (1), the weight ratio of the alkaline aqueous solution to the acidic molecular sieve is 100:12; the acidic molecular sieve is h-beta molecular sieve purchased from Zhuoran Environmental Protection Technology (Dalian) Co., Ltd., with a silicon-aluminum molar ratio of 70 and a D50 particle size of 4 microns;

[0042] In step (2), the weight ratio of modified molecular sieve, water and stearic acid is 40:100:0.6; the heating reaction conditions are: stirring the reaction at 85°C for 1.5 hours; the drying conditions are: drying at 115°C to constant weight;

[0043] The preparation method of the composition containing 3,4-dimethylbenzylidene sorbitol nucleating agent is as follows: stearic acid modified molecular sieve, hydrogenated styrene butadiene rubber and 3,4-dimethylbenzylidene sorbitol nucleating agent are mixed and ground in a ball mill, and then mixed in a two-dimensional mixer for 30 minutes to obtain;

[0044] The mixing and grinding conditions were as follows: ball milling for 5 h at a rotation speed of 520 rpm and a grinding ball diameter of 5 mm.

[0045] Example 2

[0046] This embodiment provides a composition containing a 3,4-dimethylbenzylidene sorbitol nucleating agent, the composition is a stearic acid modified molecular sieve, hydrogenated styrene-butadiene rubber and a 3,4-dimethylbenzylidene sorbitol nucleating agent;

[0047] The weight ratio of stearic acid modified molecular sieve to hydrogenated styrene butadiene rubber is 30:100;

[0048] The weight ratio of 3,4-dimethylbenzylidene sorbitol nucleating agent to hydrogenated styrene butadiene rubber is 45:100;

[0049] Hydrogenated styrene butadiene rubber was purchased from Shenzhen Wansuyuan Rubber & Plastic Co., Ltd., with the brand name PNBR-830 ​​and an average particle size of 70 mesh;

[0050] The preparation method of stearic acid modified molecular sieve is as follows: (1) stirring an alkaline aqueous solution of N,N-diisopropylethylamine with a concentration of 0.01 mol / L and triethylamine with a concentration of 0.2 mol / L with an acidic molecular sieve at 65°C for 7 hours for alkaline etching, then filtering, and washing with water for multiple times until the filtrate is neutral to obtain a modified molecular sieve; (2) mixing the modified molecular sieve, water, and stearic acid, heating the mixture for reaction, and then centrifuging and drying the solid to obtain the stearic acid modified molecular sieve;

[0051] In step (1), the weight ratio of the alkaline aqueous solution to the acidic molecular sieve is 100:15; the acidic molecular sieve is h-beta molecular sieve purchased from Zhuoran Environmental Protection Technology (Dalian) Co., Ltd., with a silicon-aluminum molar ratio of 70 and a D50 particle size of 4 microns;

[0052] In step (2), the weight ratio of the modified molecular sieve, water and stearic acid is 50:100:0.5; the heating reaction conditions are: stirring the reaction at 80°C for 2 hours; the drying conditions are: drying at 120°C to constant weight;

[0053] The preparation method of the composition containing 3,4-dimethylbenzylidene sorbitol nucleating agent is as follows: stearic acid modified molecular sieve, hydrogenated styrene butadiene rubber and 3,4-dimethylbenzylidene sorbitol nucleating agent are mixed and ground in a ball mill, and then mixed in a two-dimensional mixer for 40 minutes to obtain;

[0054] The mixing and grinding conditions were as follows: ball milling at a rotation speed of 400 rpm for 6 h and a grinding ball diameter of 5 mm.

[0055] Comparative Example 1

[0056] This comparative example provides a composition containing a 3,4-dimethylbenzylidene sorbitol nucleating agent, which is a stearic acid-modified molecular sieve and a 3,4-dimethylbenzylidene sorbitol nucleating agent;

[0057] The weight ratio of stearic acid modified molecular sieve to 3,4-dimethylbenzylidene sorbitol nucleating agent is 7:6;

[0058] The preparation method of stearic acid modified molecular sieve is:

[0059] (1) an alkaline aqueous solution of 0.03 mol / L N,N-diisopropylethylamine and 0.15 mol / L triethylamine was stirred and reacted with an acidic molecular sieve at 70°C for 6 hours for alkaline etching, and then filtered and washed with water for multiple times until the filtrate was neutral to obtain a modified molecular sieve;

[0060] (2) mixing the modified molecular sieve, water and stearic acid and heating them for reaction, then centrifuging and drying the solid to obtain the stearic acid modified molecular sieve;

[0061] In step (1), the weight ratio of the alkaline aqueous solution to the acidic molecular sieve is 100:12; the acidic molecular sieve is h-beta molecular sieve purchased from Zhuoran Environmental Protection Technology (Dalian) Co., Ltd., with a silicon-aluminum molar ratio of 70 and a D50 particle size of 4 microns;

[0062] In step (2), the weight ratio of modified molecular sieve, water and stearic acid is 40:100:0.6; the heating reaction conditions are: stirring the reaction at 85°C for 1.5 hours; the drying conditions are: drying at 115°C to constant weight;

[0063] The preparation method of the composition containing 3,4-dimethylbenzylidene sorbitol nucleating agent is as follows: the stearic acid modified molecular sieve and the 3,4-dimethylbenzylidene sorbitol nucleating agent are mixed and ground in a ball mill, and then mixed in a two-dimensional mixer for 30 minutes to obtain;

[0064] The mixing and grinding conditions were as follows: ball milling for 5 h at a rotation speed of 520 rpm and a grinding ball diameter of 5 mm.

[0065] Comparative Example 2

[0066] This comparative example provides a composition containing a 3,4-dimethylbenzylidene sorbitol nucleating agent, which is a hydrogenated styrene-butadiene rubber and a 3,4-dimethylbenzylidene sorbitol nucleating agent;

[0067] The weight ratio of 3,4-dimethylbenzylidene sorbitol nucleating agent to hydrogenated styrene butadiene rubber is 42:100;

[0068] Hydrogenated styrene butadiene rubber was purchased from Shenzhen Wansuyuan Rubber & Plastic Co., Ltd., with the brand name PNBR-830 ​​and an average particle size of 70 mesh;

[0069] The preparation method of the composition containing 3,4-dimethylbenzylidene sorbitol nucleating agent is as follows: hydrogenated styrene-butadiene rubber and 3,4-dimethylbenzylidene sorbitol nucleating agent are mixed and ground in a ball mill, and then mixed in a two-dimensional mixer for 30 minutes to obtain;

[0070] The mixing and grinding conditions were as follows: ball milling for 5 h at a rotation speed of 520 rpm and a grinding ball diameter of 5 mm.

[0071] Comparative Example 3

[0072] This comparative example provides a composition containing a 3,4-dimethylbenzylidene sorbitol nucleating agent, which is a stearic acid-modified molecular sieve, hydrogenated styrene-butadiene rubber and a 3,4-dimethylbenzylidene sorbitol nucleating agent;

[0073] The weight ratio of stearic acid modified molecular sieve to hydrogenated styrene butadiene rubber is 28:100;

[0074] The weight ratio of 3,4-dimethylbenzylidene sorbitol nucleating agent to hydrogenated styrene butadiene rubber is 42:100;

[0075] Hydrogenated styrene butadiene rubber was purchased from Shenzhen Wansuyuan Rubber & Plastic Co., Ltd., with the brand name PNBR-830 ​​and an average particle size of 70 mesh;

[0076] The preparation method of the stearic acid modified molecular sieve is as follows: the acidic molecular sieve, water and stearic acid are mixed and heated for reaction, and then centrifuged and the solid is dried to obtain the stearic acid modified molecular sieve;

[0077] The acidic molecular sieve is h-beta molecular sieve, purchased from Zhuoran Environmental Protection Technology (Dalian) Co., Ltd., with a silicon-aluminum molar ratio of 70 and a D50 particle size of 4 microns; the weight ratio of the acidic molecular sieve, water and stearic acid is 40:100:0.6; the heating reaction conditions are: stirring the reaction at 85°C for 1.5 hours; the drying conditions are: drying at 115°C to constant weight;

[0078] The preparation method of the composition containing 3,4-dimethylbenzylidene sorbitol nucleating agent is as follows: stearic acid modified molecular sieve, hydrogenated styrene butadiene rubber and 3,4-dimethylbenzylidene sorbitol nucleating agent are mixed and ground in a ball mill, and then mixed in a two-dimensional mixer for 30 minutes to obtain;

[0079] The mixing and grinding conditions were as follows: ball milling for 5 h at a rotation speed of 520 rpm and a grinding ball diameter of 5 mm.

[0080] Comparative Example 4

[0081] This comparative example provides a composition containing a 3,4-dimethylbenzylidene sorbitol nucleating agent, which is a modified molecular sieve, hydrogenated styrene-butadiene rubber and a 3,4-dimethylbenzylidene sorbitol nucleating agent;

[0082] The weight ratio of the modified molecular sieve to hydrogenated styrene-butadiene rubber is 28:100;

[0083] The weight ratio of 3,4-dimethylbenzylidene sorbitol nucleating agent to hydrogenated styrene butadiene rubber is 42:100;

[0084] Hydrogenated styrene butadiene rubber was purchased from Shenzhen Wansuyuan Rubber & Plastic Co., Ltd., with the brand name PNBR-830 ​​and an average particle size of 70 mesh;

[0085] The preparation method of the modified molecular sieve is as follows: an alkaline aqueous solution of N,N-diisopropylethylamine with a concentration of 0.03 mol / L and triethylamine with a concentration of 0.15 mol / L is stirred and reacted with an acidic molecular sieve at 70°C for 6 hours for alkaline etching, then filtered, washed with water for multiple times until the filtrate is neutral, and the solid is dried to obtain the modified molecular sieve; the weight ratio of the alkaline aqueous solution to the acidic molecular sieve is 100:12;

[0086] The acidic molecular sieve is h-beta molecular sieve purchased from Zhuoran Environmental Protection Technology (Dalian) Co., Ltd., with a silicon-aluminum molar ratio of 70 and a D50 particle size of 4 μm; the drying conditions are: drying at 115°C to constant weight;

[0087] The preparation method of the composition containing 3,4-dimethylbenzylidene sorbitol nucleating agent is as follows: the modified molecular sieve, hydrogenated styrene-butadiene rubber and 3,4-dimethylbenzylidene sorbitol nucleating agent are mixed and ground in a ball mill, and then mixed in a two-dimensional mixer for 30 minutes to obtain;

[0088] The mixing and grinding conditions were as follows: ball milling for 5 h at a rotation speed of 520 rpm and a grinding ball diameter of 5 mm.

[0089] Comparative Example 5

[0090] This comparative example provides a composition containing 3,4-dimethylbenzylidene sorbitol as a nucleating agent, which contains 3,4-dimethylbenzylidene sorbitol as a nucleating agent alone.

[0091] Test Case

[0092] The compositions in the examples and comparative examples were used to prepare polypropylene sheets, respectively, and the preparation method was as follows:

[0093] S1 1.2 parts by weight of the composition and 100 parts by weight of homopolymer polypropylene (T30S, Dushanzi Petrochemical, Xinjiang) were extruded into pellets in a twin-screw extruder at a melt extrusion temperature of 160-200°C. After the blend pellets were dried, they were made into sheets with a thickness of 1 mm on an injection molding machine, and then the sheets were tested.

[0094] 1. Test the light transmittance of the plate according to GB / T2410.

[0095] 2. Test the notched impact toughness of the sample at room temperature (23°C), then place the sample in an environment of -8°C for 24 hours and test the notched impact toughness. The notched impact toughness is tested in accordance with GB / T1843-2008.

[0096] The test results are shown in Table 1.

[0097] 1mm light transmittance <![CDATA[Notch impact toughness (KJ / m 2 )]]> <![CDATA[Charpy impact toughness (-8 °C) (KJ / m 2 )]]> Example 1 85.50% 5.15 2.66 Example 2 84.40% 5.05 2.38 Comparative Example 1 84.70% 3.59 0.85 Comparative Example 2 70.80% 3.1 1.67 Comparative Example 3 74.80% 5.01 2.56 Comparative Example 4 76.90% 3.95 1.6 Comparative Example 5 68.20% 2.51 0.49

[0098] It can be seen from the test results in Table 1 that when the composition of the present invention is used in polypropylene, it can not only increase the transparency of polypropylene, but also increase the toughness of polypropylene, and increase its low-temperature toughness to a certain extent.

Claims

1. A nucleating agent composition containing 3,4-dimethylbenzylidene sorbitol, characterized in that: The composition comprises stearic acid modified molecular sieve, hydrogenated styrene-butadiene rubber and 3,4-dimethylbenzylidene sorbitol nucleating agent; The weight ratio of the stearic acid modified molecular sieve to the hydrogenated styrene butadiene rubber is 20-50:100; the weight ratio of the 3,4-dimethylbenzylidene sorbitol nucleating agent to the hydrogenated styrene butadiene rubber is 30-60:100; The preparation method of the stearic acid modified molecular sieve comprises: (1) etching the acidic molecular sieve with alkali, filtering it, and washing it with water for multiple times until the filtrate is neutral to obtain a modified molecular sieve; (2) The modified molecular sieve, water and stearic acid are mixed and heated for reaction, followed by centrifugation and solid drying to obtain the stearic acid modified molecular sieve.

2. The composition according to claim 1, characterized in that The average particle size of the hydrogenated styrene butadiene rubber is 60-80 meshes.

3. The composition according to claim 1, characterized in that The alkaline etching method is: stirring an alkaline aqueous solution of 0.01-0.05 mol / L N,N-diisopropylethylamine and 0.1-0.2 mol / L triethylamine with an acidic molecular sieve at 65-70° C. for 5-7 hours.

4. The composition according to claim 3, characterized in that The weight ratio of the alkaline aqueous solution to the acidic molecular sieve is 100:8-20.

5. The composition according to claim 3, characterized in that The silicon-aluminum molar ratio of the acidic molecular sieve is 30-300; the D50 particle size of the acidic molecular sieve is 2-6 microns; the acidic molecular sieve is selected from at least one of h-beta molecular sieve, ZSM-S molecular sieve, SBA-15 molecular sieve and HY molecular sieve.

6. The composition according to claim 3, characterized in that The weight ratio of the modified molecular sieve, water and stearic acid is 30-50:100:0.5-1; the heating reaction conditions are: stirring the reaction at 80-90° C. for 1-2 hours.

7. A method for preparing the 3,4-dimethylbenzylidene sorbitol nucleating agent composition according to any one of claims 1 to 6, characterized in that: The preparation method comprises: mixing and grinding stearic acid modified molecular sieve, hydrogenated styrene butadiene rubber and 3,4-dimethylbenzylidene sorbitol nucleating agent in a ball mill, and then mixing them in a two-dimensional mixer to obtain the product.

8. The preparation method according to claim 7, characterized in that: The mixing and grinding conditions are as follows: ball milling for 4-6 hours at a rotation speed of 400-600 rpm, with a grinding ball diameter of 5 mm; and mixing time in a two-dimensional mixer for 20-40 minutes.