Calcium carbonate modified polypropylene composite material and its preparation method

Abstract

This invention provides a calcium carbonate-modified polypropylene composite material and its preparation method. The method involves mixing calcium carbonate powder with a surfactant containing double bonds and stirring at high temperature for a predetermined time to obtain surface-modified calcium carbonate. The surface-modified calcium carbonate is then mixed with polypropylene and an initiator, stirred for a predetermined time, and melt-extruded at 170–210°C to obtain the calcium carbonate-modified polypropylene composite material. The preparation method of this invention has the advantages of rapid activation and simple process. The surface-modified calcium carbonate powder obtained has the advantages of concentrated size distribution, uniform particle size, and high activation degree. It also exhibits good compatibility with polyolefin materials. When filled into polymers, it can enhance the tensile strength and other mechanical properties of the composite material, resulting in significant economic benefits.

Description

Technical Field

[0001] This invention relates to the field of polypropylene composite materials technology, and in particular to a calcium carbonate modified polypropylene composite material and its preparation method. Background Technology

[0002] Inorganic calcium carbonate powder is mainly produced by physical and mechanical methods from natural minerals such as calcite and marble through crushing and grinding. Due to its wide availability, low cost, stable composition, environmental friendliness, and high whiteness, it has been widely used in plastics, rubber, inks, and coatings. In plastic products, calcium carbonate serves as a major filler and modifier, and can be extensively incorporated into resins such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), and acrylonitrile butadiene-styrene copolymer (ABS).

[0003] However, the direct application of unmodified calcium carbonate materials to products such as polyolefin films presents numerous problems. For example, due to its hydrophilic and oleophobic surface properties, unmodified calcium carbonate powder exhibits poor dispersibility in a polypropylene matrix, leading to the easy aggregation of calcium carbonate particles in the composite material, forming large agglomerates and affecting the material's uniformity and performance. Furthermore, the poor interfacial compatibility between unmodified calcium carbonate and polypropylene results in increased interfacial defects in the composite material, thus affecting its mechanical properties, such as strength and toughness. During melt extrusion, unmodified calcium carbonate powder may cause increased extruder pressure, increasing processing difficulty and impacting production efficiency and product quality. Existing modification methods, such as coupling agent modification and graft modification, may involve complex chemical reactions and high technical requirements, leading to increased production costs and hindering large-scale industrial production.

[0004] In view of this, it is necessary to design an improved calcium carbonate-modified polypropylene composite material and its preparation method to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of the prior art, the present invention aims to provide a calcium carbonate-modified polypropylene composite material and its preparation method. By mixing and modifying calcium carbonate powder with a surfactant containing double bonds, organic functional groups are introduced onto the surface of calcium carbonate. The surface-modified calcium carbonate powder is then filled into the polymer, thereby improving the dispersibility of calcium carbonate in the polypropylene matrix, enhancing the interfacial compatibility between calcium carbonate and polypropylene, and strengthening the tensile strength and other mechanical properties of the composite material.

[0006] To achieve the above objectives, the present invention provides a method for preparing calcium carbonate modified polypropylene composite material, comprising the following steps:

[0007] S1. Calcium carbonate powder is mixed with a surfactant containing double bonds and stirred at 100-150°C for a predetermined time to obtain surface-modified calcium carbonate;

[0008] S2. The surface-modified calcium carbonate obtained in step S1 is mixed with polypropylene and an initiator, stirred for a predetermined time, and melt-extruded at 170-210°C to obtain a calcium carbonate-modified polypropylene composite material.

[0009] As a further improvement of the present invention, in step S1, the mass ratio of the calcium carbonate powder to the surfactant is 100:(1-5). The particle size of the calcium carbonate powder is 50-500 nm.

[0010] Furthermore, the surfactant is stearic acid containing a double bond. The stearic acid containing a double bond is... One of them.

[0011] As a further improvement of the present invention, in step S1, the stirring speed is 5000-5500 r / min and the stirring time is 10-30 min.

[0012] As a further improvement of the present invention, in step S2, the mass ratio of the polypropylene, the initiator and the surface-modified calcium carbonate is 100:(0.1-5):(1-20).

[0013] Furthermore, the initiator is one of benzoyl peroxide, di-tert-butyl peroxide, and 2,4-dimethyl-2,5-di-tert-butylperoxyhexane. The stirring speed is 5000–5500 r / min, and the stirring time is 25–35 min.

[0014] The present invention also provides a calcium carbonate modified polypropylene composite material, which is prepared by the above-described method for preparing calcium carbonate modified polypropylene composite material.

[0015] The beneficial effects of this invention are:

[0016] This invention provides a calcium carbonate-modified polypropylene composite material and its preparation method. The method involves mixing calcium carbonate powder with a surfactant containing double bonds and stirring at high temperature for a predetermined time to obtain surface-modified calcium carbonate. The surface-modified calcium carbonate is then mixed with polypropylene and an initiator, stirred for a predetermined time, and melt-extruded at 170–210°C to obtain the calcium carbonate-modified polypropylene composite material. Unlike traditional methods of activating calcium carbonate with coupling agents, the surface-modified calcium carbonate prepared by this invention has advantages such as concentrated size distribution, uniform particle size, high activation degree, and good compatibility with polyolefin materials.

[0017] The preparation method of this invention has the advantages of rapid activation and simple process. By mixing a surfactant containing double bonds with calcium carbonate powder, organic functional groups can be introduced onto the surface of calcium carbonate. These functional groups can form better chemical bonds with the polymer matrix, thereby improving interfacial compatibility. High-temperature stirring helps the surfactant to be better adsorbed on the surface of calcium carbonate particles, making the particles easier to disperse in the polymer matrix and reducing agglomeration. When the surface-modified calcium carbonate powder is filled into the polymer, it can enhance the tensile strength and other mechanical properties of the composite material, resulting in good economic benefits. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the calcium carbonate modified polypropylene composite material of this application.

[0019] Figure 2 This is a SEM image of the surface-modified calcium carbonate in Example 1 of this application. Detailed Implementation

[0020] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0022] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0023] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0024] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0025] Calcium carbonate is one of the main filler and modifier materials in plastic products, and it can be used extensively in resins such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), and acrylonitrile butadiene-styrene copolymer (ABS). However, the direct application of unmodified calcium carbonate materials to materials such as polyolefin films can lead to problems such as numerous interfacial defects, poor structural density, low strength, and reduced water resistance.

[0026] To address the technical problems of polypropylene films, such as numerous interface defects, poor structural density, low strength, and deteriorated water resistance, this application provides a calcium carbonate-modified polypropylene composite material and its preparation method. The method involves modifying calcium carbonate with a surfactant containing double bonds and then filling the surface-modified calcium carbonate into the polypropylene, thereby achieving the technical effect of enhancing the tensile strength and other mechanical properties of the composite material.

[0027] In a first aspect, embodiments of this application provide a method for preparing a calcium carbonate-modified polypropylene composite material, comprising the following steps:

[0028] S1. Calcium carbonate powder is mixed with a surfactant containing double bonds and stirred at 100-150°C for a predetermined time to obtain surface-modified calcium carbonate with double bond groups on its surface.

[0029] S2. The surface-modified calcium carbonate obtained in step S1 is mixed with polypropylene and an initiator, stirred for a predetermined time, and melt-extruded at 170-210°C to obtain a calcium carbonate-modified polypropylene composite material.

[0030] In the technical solution of this application embodiment, the dispersibility of calcium carbonate in a polypropylene matrix can be improved by using a surfactant to modify the surface of calcium carbonate powder. The surfactant reduces the hydrophilicity of the calcium carbonate surface, enhances its compatibility with polypropylene, and thus reduces agglomeration. The interfacial compatibility between the surface-modified calcium carbonate and polypropylene is improved, reducing interfacial defects and enhancing the mechanical properties of the composite material. The modified calcium carbonate is easier to mix with polypropylene during melt extrusion, which helps reduce extruder pressure, improve processing efficiency, and enhance product quality. This method is relatively simple, does not require complex chemical reactions, and is easily implemented in industrial production.

[0031] Furthermore, in some embodiments, in step S1, the mass ratio of calcium carbonate powder to surfactant is 100:(1-5). The particle size of the calcium carbonate powder is 50-500 nm. 。The surfactant is stearic acid, which contains a double bond.

[0032] In the technical solution of this application embodiment, nano-sized calcium carbonate powder, due to its small particle size, is more easily and uniformly dispersed in the polymer matrix. The addition of surfactant further reduces particle agglomeration and improves the dispersibility of the filler. Through the chemical reaction between the double bonds in stearic acid molecules and the active sites on the surface of calcium carbonate, chemical bonds are formed, thereby changing the surface properties of calcium carbonate and making it easier to mix with polypropylene. Due to the uniform dispersion of the filler and the improved interfacial compatibility, the mechanical properties of the composite material are significantly improved.

[0033] Furthermore, in some embodiments, stearic acid containing double bonds is... (octadecylene acid) (n-hexadecene acid) (n-tetradecenoic acid) One of (n-dodecenoic acid). The stirring speed is 5000-5500 r / min, and the stirring time is 10-30 min.

[0034] In the technical solutions of this application embodiment, different olefinic acids have different physical and chemical properties. Selecting a suitable olefinic acid can more effectively interact with the calcium carbonate surface and the polypropylene matrix, thereby improving interfacial compatibility. High-speed stirring helps the olefinic acid to better coat the surface of calcium carbonate particles, improve its dispersibility in polypropylene, reduce the agglomeration of calcium carbonate particles, and ensure the uniform distribution of fillers.

[0035] Further, in some embodiments, in step S2, the mass ratio of polypropylene, initiator, and surface-modified calcium carbonate is 100:(0.1-5):(1-20). The initiator is one of benzoyl peroxide, di-tert-butyl peroxide, and 2,4-dimethyl-2,5-di-tert-butylperoxyhexane. The stirring speed is 5000-5500 r / min, and the stirring time is 25-35 min.

[0036] In the technical solution of this application embodiment, by adjusting the ratio of polypropylene, initiator, and modified calcium carbonate, the performance of the composite material can be precisely controlled, reducing production costs. An appropriate amount of modified calcium carbonate ensures good dispersion in the polypropylene matrix, avoiding agglomeration caused by excessive filler. The initiator effectively initiates the free radical polymerization reaction of polypropylene during melt extrusion, contributing to improved composite material performance. High-speed stirring helps ensure uniform mixing between modified calcium carbonate, polypropylene, and the initiator, reducing filler particle agglomeration, improving dispersibility, ensuring sufficient reaction between the initiator and polypropylene, and enhancing the modification effect.

[0037] Please refer to Figure 1Secondly, embodiments of this application provide a calcium carbonate-modified polypropylene composite material, wherein... Let m represent calcium carbonate, n represent the number of stearic acid units with double bonds, and n represent the number of repeating units in polypropylene. This composite material, prepared by the method described in the first aspect, possesses excellent mechanical properties, broadens its application range, and has high practical value and market potential.

[0038] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0039] Example 1

[0040] Example 1 provides a method for preparing surface-modified calcium carbonate, comprising the following steps:

[0041] Calcium carbonate powder with a particle size of 50 nm was mixed with n-octadecene acid at a mass ratio of 100:5. The mixture was stirred in a high-speed mixer at 100°C for 5000 r / min for 30 min to obtain surface-modified calcium carbonate. The SEM image is shown below. Figure 2 As shown in the figure, the prepared surface-modified calcium carbonate has a concentrated size distribution and uniform particle size.

[0042] Examples 2-5

[0043] Examples 2-5 provide a method for preparing surface-modified calcium carbonate. Compared with Example 1, the only difference is the particle size of the calcium carbonate powder, as shown in Table 1. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0044] Examples 6-8

[0045] Examples 6-8 provide a method for preparing surface-modified calcium carbonate. The only difference from Example 1 is the different surfactants, as shown in Table 1. Other experimental parameters and conditions are basically the same as in Example 1 and will not be repeated here.

[0046] Examples 9-10

[0047] Examples 9-10 provide a method for preparing surface-modified calcium carbonate. Compared with Example 1, the only difference is the mass ratio of calcium carbonate powder to surfactant, as shown in Table 1. Other experimental parameters and conditions are basically the same as in Example 1, and will not be repeated here.

[0048] Comparative Examples 1-2

[0049] Comparative Examples 1 and 2 provide methods for preparing surface-modified calcium carbonate. The only difference between them and Example 1 is the different surfactants, as shown in Table 1. Other experimental parameters and conditions are basically the same as those in Example 1, and will not be repeated here.

[0050] Table 1 Comparison of experimental parameters

[0051]

[0052]

[0053] Characterization of calcium carbonate powder includes oil absorption value, water absorption rate, and activation degree. Tests were conducted according to the GB / T 19590-2011 standard for nano-calcium carbonate, and the results are shown in Table 2. The oil absorption value is the amount of DOP (octyl phthalate) absorbed per 100 grams of sample; the water absorption rate is the result of the sample being continuously exposed at 85℃ and 95% humidity for 72 hours.

[0054] Table 2. Test results of the examples and comparative examples.

[0055]

[0056]

[0057] As shown in Table 2, under the same conditions, with the increase of the particle size of nano-calcium carbonate, the oil absorption value of the surface-modified calcium carbonate decreases and the activation rate increases. When the particle size of calcium carbonate exceeds 100 nanometers, the activation rate reaches 100%. The water absorption rate of modified nano-calcium carbonate is related to the particle size and activation degree of the material. When the activation rate reaches 100%, the water absorption rate remains at a low level. Under the same conditions, with the decrease of carbon atom length in the surfactant, the oil absorption value of the calcium carbonate increases. This is mainly because the shorter the carbon atom length, the more flexible the molecular chain movement. Under the same activation process conditions, the reaction between the molecular chain and calcium carbonate is more intense, and the activation effect is better. In addition, the shorter the carbon atom length, the more molecules there are under the condition of the same mass of activator, resulting in a higher molar ratio of surfactant to calcium carbonate, better activation effect, and higher oil absorption value. Furthermore, using the same surfactant for modification, the higher the amount of activator, the higher the oil absorption value. Comparative Example 1 used dodecanoic acid to modify calcium carbonate, resulting in a low activation degree. Comparative Example 2 used n-octadecanoic acid to modify calcium carbonate, resulting in both low oil absorption value and low activation degree. This indicates that stearic acid, which contains double bonds, has a better modification effect on calcium carbonate.

[0058] Example 11

[0059] Example 11 provides a method for preparing a calcium carbonate-modified polypropylene composite material, comprising the following steps:

[0060] Polypropylene, initiator, and surface-modified calcium carbonate obtained in Example 1 were mixed at a mass ratio of 100:1:15, stirred at 5000 r / min for 30 min, and then melt-extruded at 180°C to prepare a calcium carbonate-modified polypropylene composite material.

[0061] The composite material was prepared into standard test specimens, and the modified properties were tested. The testing standard referred to Part 2 of GB / T1040.2 Determination of Tensile Properties of Plastics: Test Conditions for Molded and Extruded Plastics. The test results are shown in Table 3.

[0062] Examples 12-13 and Comparative Examples 3-6

[0063] Examples 12-13 and Comparative Examples 3-6 provide a method for preparing calcium carbonate modified polypropylene composite materials. Compared with Example 11, the only difference is that the mass ratio of polypropylene to initiator and surface-modified calcium carbonate obtained in Example 1 is different, as shown in Table 3. Other experimental parameters and conditions are basically the same as those in Example 11, and will not be repeated here.

[0064] Comparative Example 7 uses commercially available T30 (polypropylene resin) material.

[0065] Table 3 Performance test results of composite materials

[0066]

[0067] As shown in Table 3, in Examples 11-13, when the mass of polypropylene and modified calcium carbonate remained constant and the initiator content gradually increased, the tensile yield stress and tensile fracture stress of the composite material increased significantly. This is because with the increase of initiator, the double bonds on the surface of modified calcium carbonate were completely reacted, and calcium carbonate and polypropylene were linked by chemical bonds, resulting in a significant increase in the tensile stress and tensile fracture stress of the material. In addition, the addition of inorganic components to the material system increased the hardness and rigidity of the material, resulting in a slight decrease in the elongation at break compared to the unmodified polypropylene material, but still meeting the requirements for use. In Comparative Examples 3-6, under the same conditions of polypropylene and initiator, the increase in tensile yield stress and tensile fracture stress of the composite material was relatively small with the increase of calcium carbonate content. This is because when the initiator content was only 0.05%, the initiator content was low and failed to fully initiate the double bonds on the surface of nano-calcium carbonate, allowing it to further react with polypropylene. The remaining calcium carbonate that did not react with the initiator directly filled the interior of the polypropylene material, resulting in a smaller increase in the tensile yield stress and tensile fracture stress of the composite material.

[0068] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a calcium carbonate-modified polypropylene composite material, characterized in that, Includes the following steps: S1. Calcium carbonate powder is mixed with a surfactant containing double bonds and stirred at 100~150°C for a predetermined time to obtain surface-modified calcium carbonate; the mass ratio of the calcium carbonate powder to the surfactant is 100:(1~5); the particle size of the calcium carbonate powder is 50~500nm; The surfactant containing double bonds is , , , One of them; S2. The surface-modified calcium carbonate obtained in step S1 is mixed with polypropylene and an initiator, stirred for a predetermined time, and melt-extruded at 170~210°C to obtain a calcium carbonate-modified polypropylene composite material. The mass ratio of the polypropylene, the initiator and the surface-modified calcium carbonate is 100:(0.1~5):(1~20).

2. The method for preparing calcium carbonate modified polypropylene composite material according to claim 1, characterized in that, In step S1, the stirring speed is 5000~5500 r / min, and the stirring time is 10~30 min.

3. The method for preparing calcium carbonate modified polypropylene composite material according to claim 1, characterized in that, In step S2, the initiator is one of benzoyl peroxide, di-tert-butyl peroxide, and 2,4-dimethyl-2,5-di-tert-butylperoxyhexane.

4. The method for preparing calcium carbonate modified polypropylene composite material according to claim 1, characterized in that, In step S2, the stirring speed is 5000~5500 r / min, and the stirring time is 25~35 min.

5. A calcium carbonate-modified polypropylene composite material, characterized in that, The calcium carbonate modified polypropylene composite material is prepared by the method described in any one of claims 1-4.

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