Calcium carbonate modified polypropylene composite material and preparation method thereof

Abstract

The invention provides a calcium carbonate modified polypropylene composite material and a preparation method thereof.The preparation method comprises the steps that calcium carbonate powder and a surfactant containing double bonds are mixed and stirred at the high temperature for preset time, and surface modified calcium carbonate is obtained; and mixing the surface modified calcium carbonate with polypropylene and an initiator, stirring for a preset time, and carrying out melt extrusion at 170-210 DEG C to obtain the calcium carbonate modified polypropylene composite material. The preparation method provided by the invention has the advantages of rapid activation and simple process, and the prepared surface modified calcium carbonate powder has the advantages of concentrated size distribution, uniform particle size and high activation degree, has good compatibility with polyolefin materials, can enhance the tensile strength and other mechanical properties of a composite material when being filled into a polymer, and has good application prospects. And good economic benefits are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of polypropylene composite materials, and in particular to a calcium carbonate-modified polypropylene composite material and a preparation method thereof. Background Art

[0002] Inorganic calcium carbonate powder is mainly obtained by crushing and grinding natural calcite, marble and other minerals through physical and mechanical methods. It has been widely used in plastics, rubber, inks and coatings due to its wide range of sources, low cost, stable composition, environmental protection and high whiteness. In plastic products, calcium carbonate is a major filling and modification material that can be filled in large quantities in resins such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), and acrylonitrile butadiene-styrene copolymer (ABS).

[0003] However, there are many problems when unmodified calcium carbonate materials are directly applied to products such as polyolefin films. For example, due to its hydrophilic and oleophobic surface characteristics, the unmodified calcium carbonate powder has poor dispersibility in the polypropylene matrix, which causes the calcium carbonate particles in the composite material to easily aggregate and form larger agglomerates, affecting the uniformity and performance of the material; the interface compatibility between unmodified calcium carbonate and polypropylene is poor, resulting in an increase in interface defects in the composite material, thereby affecting the mechanical properties of the material, such as strength and toughness; during the melt extrusion process, unmodified calcium carbonate powder may cause the pressure of the extruder to increase, increase the processing difficulty, and affect production efficiency and product quality. Existing modification methods such as coupling agent modification and grafting modification may involve complex chemical reactions and high technical requirements, resulting in increased production costs, which is not conducive to large-scale industrial production.

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

[0005] In view of the defects of the above-mentioned prior art, the object of the present invention is to provide a calcium carbonate-modified polypropylene composite material and a preparation method thereof, by mixing and modifying calcium carbonate powder with a surfactant containing double bonds, introducing organic functional groups on the surface of calcium carbonate, and filling the surface-modified calcium carbonate powder into a polymer, thereby improving the dispersibility of calcium carbonate in a polypropylene matrix, improving the interface compatibility between calcium carbonate and polypropylene, and enhancing the tensile strength and other mechanical properties of the composite material.

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

[0007] S1. The calcium carbonate powder is mixed with a surfactant containing a double bond and stirred at 100 to 150 ° C for a predetermined time to obtain a 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 to 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 double bonds. The stearic acid containing double bonds 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-butyl peroxyhexane. 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 preparation method of the calcium carbonate modified polypropylene composite material.

[0015] The beneficial effects of the present invention are:

[0016] The present invention provides a calcium carbonate-modified polypropylene composite material and a preparation method thereof, wherein the surface-modified calcium carbonate is obtained by mixing calcium carbonate powder with a surfactant containing double bonds, stirring at high temperature for a predetermined time; the surface-modified calcium carbonate is mixed with polypropylene and an initiator, stirring for a predetermined time, and melt-extruded at 170 to 210° C. to obtain the calcium carbonate-modified polypropylene composite material. Different from the traditional method of activating calcium carbonate with a coupling agent, the surface-modified calcium carbonate prepared by the present invention has the advantages of concentrated size distribution, uniform particle size, high activation degree, and good compatibility with polyolefin materials.

[0017] The preparation method of the present invention has the advantages of rapid activation and simple process. By mixing a surfactant containing a double bond with calcium carbonate powder, organic functional groups can be introduced on the surface of calcium carbonate, and 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 more easily dispersed in the polymer matrix and reducing agglomeration. When the surface-modified calcium carbonate powder is filled into a polymer, the mechanical properties such as tensile strength of the composite material can be enhanced, and it has good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the calcium carbonate modified polypropylene composite material of the present application.

[0019] Figure 2 This is a SEM image of the surface-modified calcium carbonate in Example 1 of the present application. DETAILED DESCRIPTION

[0020] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0022] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0023] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0024] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0025] Calcium carbonate is one of the main filling and modifying materials in plastic products, and can be filled in large quantities in resins such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), acrylonitrile butadiene-styrene copolymer (ABS), etc. However, if unmodified calcium carbonate materials are directly used in, for example, polyolefin films, problems such as many film interface defects, poor structural density, low strength, and poor water resistance will occur.

[0026] In order to solve the technical problems of polypropylene film having many interface defects, poor structural density, low strength and poor water barrier properties, the present application provides a calcium carbonate-modified polypropylene composite material and a preparation method thereof, wherein calcium carbonate is modified by using a surfactant containing double bonds, and the surface-modified calcium carbonate is filled into polypropylene, thereby achieving the technical effect of enhancing the mechanical properties such as tensile strength of the composite material.

[0027] In a first aspect, an embodiment of the present application provides a method for preparing a calcium carbonate-modified polypropylene composite material, comprising the following steps:

[0028] S1. The calcium carbonate powder is mixed with a surfactant containing a double bond, and stirred at 100 to 150 ° C for a predetermined time to obtain a surface-modified calcium carbonate having a double bond group 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 to 210° C. to obtain a calcium carbonate-modified polypropylene composite material.

[0030] In the technical scheme of the embodiment of the present application, the dispersibility of calcium carbonate in the polypropylene matrix can be improved by surface-modifying the calcium carbonate powder using a surfactant. The surfactant can reduce the hydrophilicity of the calcium carbonate surface and enhance its compatibility with polypropylene, thereby reducing agglomeration. The interfacial compatibility between the surface-modified calcium carbonate and polypropylene is improved, the interfacial defects are reduced, and the mechanical properties of the composite material are enhanced. The modified calcium carbonate is easier to mix with polypropylene during melt extrusion, which helps to reduce the pressure of the extruder, improve processing efficiency and product quality. This method is relatively simple, does not require complex chemical reactions, and is easy to implement 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 calcium carbonate powder is 50-500 nm. 。The surfactant is stearic acid containing double bonds.

[0032] In the technical scheme of the present application embodiment, nanometer calcium carbonate powder is easier to be evenly dispersed in the polymer matrix due to its small particle size. The addition of surfactant further reduces the agglomeration phenomenon between particles and improves the dispersibility of filler. Chemical bonds are formed by the double bonds in the stearic acid molecules and the active sites on the surface of calcium carbonate, thereby changing the surface properties of calcium carbonate and making it easier to mix with polypropylene. Due to the uniform dispersion of filler and the improvement of interfacial compatibility, the mechanical properties of composite materials are significantly improved.

[0033] Further, in some embodiments, the stearic acid containing double bonds is (n-octadecene acid), (n-hexadecene acid), (n-Tetradecenoic acid), The stirring speed is 5000-5500 r / min, and the stirring time is 10-30 min.

[0034] In the technical solution of the embodiment of the present application, different olefinic acids have different physical and chemical properties. Selecting a suitable olefinic acid can more effectively interact with the surface of calcium carbonate and the polypropylene matrix, thereby improving the interfacial compatibility. High-speed stirring helps the olefinic acid to be better coated on 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-butyl peroxyhexane. The stirring speed is 5000-5500 r / min, and the stirring time is 25-35 min.

[0036] In the technical scheme of the embodiment of the present application, by adjusting the ratio of polypropylene, initiator and modified calcium carbonate, the performance of the composite material can be accurately controlled and the production cost can be reduced. An appropriate amount of modified calcium carbonate can ensure its good dispersion in the polypropylene matrix, avoiding excessive filler from causing agglomeration. The initiator can effectively initiate the free radical polymerization reaction of polypropylene during the melt extrusion process, which helps to improve the performance of the composite material. High-speed stirring helps to ensure uniform mixing between modified calcium carbonate, polypropylene and initiator, reduces the agglomeration of filler particles, improves dispersibility, ensures that the reaction between the initiator and polypropylene is fully carried out, and improves the modification effect.

[0037] Please refer to Figure 1In a second aspect, the present application provides a calcium carbonate-modified polypropylene composite material, wherein: represents calcium carbonate, m is the number of double-bond stearic acid, and n is the number of repeating units of polypropylene. The composite material is prepared by the preparation method of the first aspect, and thus has excellent mechanical properties, broadens its application range, and has high practical value and market potential.

[0038] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer 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 selected and mixed with n-octadecene acid in a mass ratio of 100:5. The mixture was mixed and stirred in a high-speed mixer at 100°C with a stirring speed of 5000 r / min and a treatment time of 30 min to obtain surface-modified calcium carbonate. The SEM image of the mixture is shown in FIG. Figure 2 As shown, it can be seen that the prepared surface-modified calcium carbonate has a concentrated size distribution and uniform particle size.

[0042] Embodiment 2-5

[0043] Examples 2-5 respectively provide a method for preparing a surface-modified calcium carbonate. Compared with Example 1, the only difference is that the particle size of the calcium carbonate powder is different, 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] Embodiment 6-8

[0045] Examples 6-8 respectively provide a method for preparing surface-modified calcium carbonate. Compared with Example 1, the only difference is that the surfactant is different, 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.

[0046] Examples 9-10

[0047] Examples 9-10 respectively provide a method for preparing a surface-modified calcium carbonate. Compared with Example 1, the only difference is that the mass ratio of calcium carbonate powder to surfactant is different, 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.

[0048] Comparative Example 1-2

[0049] Comparative Examples 1-2 respectively provide a method for preparing a surface-modified calcium carbonate. Compared with Example 1, the only difference is that the surfactant is different, 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] The characterization of calcium carbonate powder includes oil absorption value, water absorption rate, and activation degree. According to the test standard of GB / T 19590-2011 nano calcium carbonate, the test results are shown in Table 2, where the oil absorption value is the amount of DOP (octyl phthalate) absorbed per 100 grams of sample; the water absorption rate is the test result after the sample is continuously exposed to 85°C and 95% humidity for 72 hours.

[0054] Table 2 Test results of embodiments and comparative examples

[0055]

[0056]

[0057] As can be seen from Table 2, under the same conditions, with the increase of the particle size of nano calcium carbonate, the lower the oil absorption value of the surface-modified calcium carbonate, the higher the activation rate. When the particle size of calcium carbonate exceeds 100 nanometers, its 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%, its water absorption rate remains at a low level; under the same conditions, with the decrease of the carbon atom length in the surfactant, the higher the oil absorption value of its calcium carbonate, which is mainly due to the shorter length of the carbon atom, the more flexible the molecular chain movement, and the more intense the reaction degree of the molecular chain with calcium carbonate under the same activation process conditions, and the better the activation effect. In addition, the shorter the length of the carbon atom, the more molecules there are under the conditions 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. When the same surfactant is used for modification, the more activator is used, the higher the oil absorption value. In Comparative Example 1, calcium carbonate modified with n-dodecanoic acid has a low activation degree, while calcium carbonate modified with n-octadecanoic acid has a low oil absorption value and activation degree, indicating that stearic acid containing double bonds has a better modification effect on calcium carbonate.

[0058] Embodiment 11

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

[0060] Polypropylene was mixed with an initiator and the surface-modified calcium carbonate obtained in Example 1 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 a standard test specimen and the modified performance was tested. The test standard was based on the GB / T1040.2 Determination of tensile properties of plastics Part 2: 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 a calcium carbonate-modified polypropylene composite material. 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 is commercially available T30 (polypropylene resin) material.

[0065] Table 3 Performance test results of composite materials

[0066]

[0067] As can be seen from Table 3, in embodiment 11-13, when the quality of polypropylene and modified calcium carbonate is constant, when the initiator content increases gradually, the tensile yield stress and fracture stress of composite material have a large increase, this is because along with the increase of initiator, the double bonds on the surface of modified calcium carbonate are all reacted completely, calcium carbonate and polypropylene are connected by chemical bond, the tensile stress and fracture stress of material are increased significantly. In addition, due to the addition of inorganic components in the material system, the hardness and rigidity of the material are increased, so that the elongation at break of the pull-up is decreased compared with the unmodified polypropylene material, but still can meet the use needs. In comparative example 3-6, under the same conditions of polypropylene and initiator, along with the increase of calcium carbonate content, the tensile yield stress and tensile fracture stress of composite material are improved less, this is because when the initiator is only 0.05, the initiator content is less, and the double bonds on the surface of nano calcium carbonate are not fully initiated, so that it is further reacted with polypropylene, and other calcium carbonates that do not react with the initiator are directly filled in the polypropylene material interior, so that the tensile yield stress and tensile fracture stress of composite material increase less.

[0068] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. 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 may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a calcium carbonate-modified polypropylene composite material, characterized in that: The following steps are involved: S1. The calcium carbonate powder is mixed with a surfactant containing a double bond and stirred at 100 to 150 ° C for a predetermined time to obtain a surface-modified calcium carbonate; 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 to 210° C. to obtain a calcium carbonate-modified polypropylene composite material.

2. The method for preparing the calcium carbonate-modified polypropylene composite material according to claim 1, characterized in that: In step S1, the mass ratio of the calcium carbonate powder to the surfactant is 100:(1-5).

3. The method for preparing the calcium carbonate-modified polypropylene composite material according to claim 2, characterized in that: The particle size of the calcium carbonate powder is 50 to 500 nm.

4. The method for preparing the calcium carbonate-modified polypropylene composite material according to claim 2, characterized in that: The surfactant is stearic acid containing double bonds.

5. The method for preparing the calcium carbonate-modified polypropylene composite material according to claim 4, characterized in that: The stearic acid containing double bonds is One of them.

6. The method for preparing the 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.

7. The method for preparing the calcium carbonate-modified polypropylene composite material according to claim 1, characterized in that: In step S2, the mass ratio of the polypropylene, the initiator and the surface-modified calcium carbonate is 100:(0.1-5):(1-20).

8. The method for preparing the calcium carbonate-modified polypropylene composite material according to claim 7, characterized in that: The initiator is one of benzoyl peroxide, di-tert-butyl peroxide and 2,4-dimethyl-2,5-di-tert-butyl peroxyhexane.

9. The method for preparing the 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.

10. A calcium carbonate-modified polypropylene composite material, characterized in that: The polypropylene composite material modified with calcium carbonate is prepared by the preparation method of any one of claims 1 to 9.

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