Modified polypropylene water-based emulsion as well as preparation method and application thereof

Abstract

The invention discloses a modified polypropylene water-based emulsion and a preparation method and application thereof, and the preparation method comprises the following steps: stirring and premixing raw materials including polypropylene, anhydride monomers, acrylic acid monomers and an initiator, and mixing and melting to obtain modified polypropylene; mixing, melting and emulsifying the modified polypropylene, a composite surfactant and water to obtain modified polypropylene water-based emulsion; the raw materials comprise the following components in parts by mass: 100 parts of polypropylene, 0.2-1.5 parts of an initiator, 1-7.5 parts of an anhydride monomer and 1-7.5 parts of an acrylic acid monomer; the total amount of the anhydride monomer and the acrylic acid monomer in the raw materials is 5-10 parts; the mass ratio of the anhydride monomer to the acrylic acid monomer in the raw materials is 1: (0.8-1.2). According to the method, grafting of polypropylene is achieved by means of a reaction blending method, the emulsion obtained after further emulsification is stable in performance, and the interface bonding strength of glass fibers and polypropylene can be obviously improved when the emulsion is used for treating the glass fibers.

Description

Technical Field

[0001] The invention relates to the technical field of polymer composite material additives, and in particular to a modified polypropylene aqueous emulsion and a preparation method and application thereof. Background Art

[0002] Polypropylene (PP) has become one of the fastest-growing general-purpose thermoplastic polymers today due to its excellent comprehensive properties. It is widely used in electronic devices, automobile manufacturing, medical devices and other fields due to its many advantages such as good processing performance, high thermal stability and recyclability. Glass fiber (GF) has good mechanical strength and heat resistance and is often used as a plastic reinforcement material. Glass fiber reinforced polypropylene (GFRPP) composites have the advantages of high performance and light weight, as well as higher toughness and recyclable processing. However, when the highly polar GF is compounded with the non-polar, low-reactivity PP, the poor interfacial compatibility makes it difficult for the two to form good adhesion at the interface.

[0003] Surface coating modification is the most widely used GF surface treatment method in commercial applications. By coating the GF surface, the interfacial compatibility between the matrix material and the GF can be promoted without changing the main structure of the fiber. Common measures include silane coupling agent infiltration. One end of the coupling agent molecule is bonded to the GF surface through Si-O-Si bonds, and the other end chemically reacts with the matrix material through active groups, thereby improving the interfacial adhesion between the matrix material and the GF. In addition, coating GF with modified epoxy resin can also improve the interfacial bonding force. However, these methods are difficult to effectively improve the interfacial bonding strength of PP / GF composite systems. Because the PP molecular chain does not contain highly reactive groups, it cannot react with coupling agents or modified epoxy resins.

[0004] For PP / GF composite system, an effective method to improve interface bonding is to use interface compatibilizer treatment, that is, to coat a layer of modified PP resin on the surface of GF. Because the skeleton structure of this type of molecule is similar to that of PP matrix material, and it also contains groups that can react with silanol groups on the surface of GF, thus improving interface bonding.

[0005] CN105131874A discloses a method for preparing a water-soluble maleic anhydride modified PP emulsion for fiber surface treatment, wherein maleic anhydride modified polypropylene wax, an organic solvent, an emulsifier and other additives are mixed, heated and dissolved, and then water is added to the solution system for stirring and shearing to finally obtain a modified PP emulsion. However, this method requires the use of a large amount of benzene organic solvents, has a high production cost, and releases volatile organic compounds when the emulsion is used, which is harmful to human health and the environment.

[0006] CN113463393A discloses a water-based modified chlorinated polypropylene sizing agent suitable for carbon fiber, and a preparation method and application thereof. The sizing agent comprises: modified chlorinated polypropylene, an emulsifier and deionized water; wherein the modified chlorinated polypropylene is obtained by reacting chlorinated polypropylene, acrylic acid monomer and an initiator, and the chlorine content in the chlorinated polypropylene is replaced by grafting acrylic acid monomer on the chlorinated polypropylene, so that the modified chlorinated polypropylene has good thermal stability; since the modified chlorinated polypropylene can be dissolved in an organic solvent, the water-based modified chlorinated polypropylene sizing agent without organic solvent is obtained by an emulsion solvent volatilization method, and the prepared sizing agent can effectively improve the interface bonding ability of the carbon fiber / polypropylene composite material; but the preparation process of the modified chlorinated polypropylene requires a complex synthesis process. Summary of the invention

[0007] Aiming at the problems of poor interfacial compatibility between glass fiber and polypropylene, residual organic solvent of existing sizing agent and complicated preparation method, the present invention provides a preparation method of modified polypropylene aqueous emulsion for glass fiber. The method realizes grafting of polypropylene by means of reaction blending method, and the emulsion obtained after further emulsification has stable performance. The emulsion is used for treating glass fiber and can significantly improve the interfacial bonding strength between glass fiber and polypropylene.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for preparing a modified polypropylene aqueous emulsion comprises the following steps:

[0010] Step 1, premixing raw materials including polypropylene, anhydride monomers, acrylic monomers and initiators, and mixing and melting to obtain modified polypropylene;

[0011] Step 2, mixing the modified polypropylene, the composite surfactant and water to melt and emulsify to obtain the modified polypropylene aqueous emulsion;

[0012] The raw materials include 100 parts of polypropylene, 0.2-1.5 parts of initiator, 1-7.5 parts of anhydride monomer, and 1-7.5 parts of acrylic acid monomer in parts by mass;

[0013] The total amount of anhydride monomers and acrylic acid monomers in the raw materials is 5-10 parts; the mass ratio of anhydride monomers to acrylic acid monomers in the raw materials is 1:0.8-1.2.

[0014] In the present invention, polypropylene is modified by grafting with anhydride monomers and acrylic monomers to achieve a higher grafting rate, so that more hydrophilic groups are contained in the polypropylene chain segments, and the reaction activity of polypropylene is improved; the preparation method adopts ordinary melt blending, and efficient grafting can be achieved in a short time. After the prepared aqueous emulsion is used for surface treatment of glass fiber, the mechanical properties of the prepared GFRPP composite material are enhanced. Since the main chain structure of the modified polypropylene in the aqueous emulsion is the same as that of polypropylene, the two have good compatibility, and the molecular chains can be entangled with each other; and the side branches composed of copolymerized grafting of anhydride monomers and acrylic monomers can produce hydrogen bonds and chemical bonds with the silicon hydroxyl groups on the surface of the glass fiber, thereby improving the interface compatibility between the glass fiber and the polypropylene matrix material, and enhancing the mechanical properties of the GFRPP composite material.

[0015] The weight average molecular weight of the polypropylene is below 100000. The low molecular weight polypropylene has a lower melt viscosity and a higher grafting efficiency. The modified polypropylene has a stronger hydrophilicity, which is more conducive to the subsequent water phase emulsification and glass fiber surface treatment.

[0016] The anhydride monomers include maleic anhydride and / or methacrylic anhydride;

[0017] The acrylic monomer includes one or more of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, etc.;

[0018] The initiator includes one or more of dicumyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, etc.;

[0019] The raw materials of the modified polypropylene aqueous emulsion in step 2 include 10-30% modified polypropylene, 2-15% composite surfactant, and 55-88% deionized water in terms of mass fraction. The emulsification process of the present invention does not require any organic solvent, and can directly use water as a medium to obtain the aqueous emulsion, thereby avoiding environmental pollution and harm to human body.

[0020] The composite surfactant comprises a nonionic surfactant, an anionic surfactant, an emulsifier and a neutralizing base; the mass ratio of each component is 5-8:0.5-1.5:0.5-1.5:1-3.

[0021] The nonionic surfactant includes one or more of polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, and polyoxyethylene stearate;

[0022] The anionic surfactant includes one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate;

[0023] The auxiliary emulsifier includes one or more of stearic acid, palmitic acid, and oleic acid;

[0024] The neutralizing base includes one or more of ethanolamine, diethanolamine, and triethanolamine.

[0025] The temperature of the mixing and melting in step 1 is 150-200° C., and the mixing time is 4-16 min.

[0026] In step 2, the emulsification temperature is 150-180° C., and the emulsification time is 110-200 min.

[0027] The present invention also provides a modified polypropylene aqueous emulsion prepared by the preparation method, wherein the average particle size of the modified polypropylene aqueous emulsion is 100-5000nm.

[0028] The invention also provides application of the modified polypropylene aqueous emulsion in a composite system of polypropylene and glass fiber.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) In the present invention, polypropylene is melt-grafted and modified with anhydride monomers and acrylic acid monomers, and polar groups are introduced into the polypropylene molecular chain to improve the reactivity and hydrophilicity of polypropylene. The modified polypropylene aqueous emulsion is prepared by melt emulsification, and no organic solvents such as benzene and ester are used in the emulsification process, thereby reducing the harm to human health and the environment. By using a nonionic surfactant and an anionic surfactant to form a mixed latex micelle, the solubilization ability of the emulsification system is improved, and the tolerance of the emulsion to electrolytes is enhanced, thereby increasing the stability of the emulsion.

[0031] (2) The modified polypropylene aqueous emulsion in the present invention is a new type of compatibilizer aqueous emulsion for glass fiber surface treatment. The modified polypropylene main chain structure in the modified polypropylene aqueous emulsion is exactly the same as that of the polypropylene matrix material, and the two have good compatibility, and the molecular chains can be entangled with each other; and the side branches composed of copolymerized grafting of anhydride monomers and acrylic monomers can generate hydrogen bonds and chemical bonds with the silanol groups on the surface of the glass fiber, thereby improving the interface compatibility between the glass fiber and the polypropylene matrix material, and enhancing the mechanical properties of the GFRPP composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is the infrared spectrum of polypropylene before and after melt grafting modification in Example 1.

[0033] Figure 2 This is the surface water contact angle diagram of polypropylene before and after melt grafting modification in Example 2.

[0034] Figure 3 It is the non-isothermal melting curve of polypropylene before and after melt grafting modification in Example 2.

[0035] Figure 4 This is the effect of different grafting temperatures on the grafting effect of modified polypropylene in Example 3.

[0036] Figure 5 This is the effect of different grafting times on the grafting effect of modified polypropylene in Example 4.

[0037] Figure 6 This is the effect of different emulsification temperatures on the emulsion particle size during the melt emulsification process in Example 8.

[0038] Figure 7 This is the effect of different emulsification times on the emulsion particle size during the melt emulsification process in Example 9.

[0039] Figure 8 These are SEM images of the glass fiber in Application Example 1 before and after emulsion treatment.

[0040] Fig. 9 This is a comparison of the mechanical properties of GFRPP composite materials in Application Example 2.

[0041] Fig.10 This is a cross-sectional SEM image of the GFRPP composite material in Application Example 2. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art can make modifications or equivalent substitutions based on the understanding of the technical scheme of the present invention without departing from the spirit and scope of the technical scheme of the present invention, and all should be included in the protection scope of the present invention.

[0043] The raw materials used in the following specific embodiments are all purchased from the market, polypropylene PP-S1: number average molecular weight is 7000 g / mol, weight average molecular weight is 14000 g / mol, polypropylene PP-S2: number average molecular weight is 76000 g / mol, weight average molecular weight is 266000 g / mol. Other raw materials are purchased from the market and used directly without treatment.

[0044] The test characterization methods used in the following examples are:

[0045] Infrared spectrum test: The samples were analyzed by infrared spectrometer, and the sample was prepared by potassium bromide tablet method. The scanning range was 4000-400cm -1 .

[0046] Water contact angle test: The sample is pressed into a thin sheet, and the static contact angle of the sample surface is tested by a video optical contact angle meter. The contact liquid is deionized water.

[0047] Differential scanning calorimetry test: The samples were characterized by differential scanning calorimetry. The samples were first heated to 200°C at a heating rate of 30°C / min and kept at this temperature for 5 minutes to eliminate the thermal history. Then, they were cooled from 200°C to 50°C at a cooling rate of 10°C / min to test their crystallization behavior. Finally, they were heated from 50°C to 200°C at a heating rate of 10°C / min to test their melting behavior.

[0048] Particle size distribution test: The particle size distribution of the sample was tested by a nanoparticle size potential analyzer. The emulsion was diluted to a certain concentration using deionized water. The measurement range was 1-10000nm.

[0049] Microscopic morphology observation: The microscopic morphology of the sample was observed by scanning electron microscopy. Before observation, the sample was dried and the surface of the sample was sprayed with gold.

[0050] Mechanical properties test: The mechanical properties of the samples were characterized by a universal material testing machine and a pendulum impact tester. The tensile performance test was based on the GB / T 1040.1-2018 standard, the bending performance test was based on the GB / T9341-2008 standard, and the impact performance test was based on the GB / T 1843-2008 standard.

[0051] Example 1

[0052] 100 parts of polypropylene PP-S1, 5 parts of maleic anhydride, 5 parts of acrylic acid, and 0.5 parts of dicumyl peroxide were stirred and pre-mixed, and then put into a mixer for melt grafting reaction. The mixing temperature was set to 180° C., the mixing time was 10 min, and the rotor speed was 20 r / min.

[0053] After the reaction is completed, the grafted product is taken out, heated with xylene to dissolve the grafted product, acetone is added for precipitation, filtered and dried to obtain purified modified polypropylene. The raw polypropylene and the purified modified polypropylene are tested by infrared spectroscopy. The results are as follows: Figure 1 shown.

[0054] Compared with the pure PP sample, the purified grafted modified PP has a -1 、1782cm -1 and 1716cm -1 A new infrared absorption peak appeared. 1866cm -1 、1782cm -1 The absorption peak at 1716cm is generated by the C=O of the five-membered cyclic anhydride, while the absorption peak at 1716cm -1 The absorption peak is generated by the C=O of the carboxyl group, which indicates that the MAH and AA monomers are successfully grafted onto the PP molecular chain.

[0055] Example 2

[0056] 100 parts of polypropylene PP-S1 and 0.5 parts of diisopropylbenzene peroxide were premixed, the ratio of maleic anhydride monomer to acrylic acid monomer was fixed at 1:1, and 2, 8, and 10 parts of the total monomer were added respectively, and then put into the mixer for melt grafting reaction. The grafted products were recorded as grafted modified PP-1, grafted modified PP-2, and grafted modified PP-3 respectively. The mixing temperature was set to 180°C, the mixing time was 10min, and the rotor speed was 20r / min. After the reaction, the grafted product was taken out, the grafted product was heated and dissolved with xylene, acetone was added for precipitation, and filtered and dried to obtain purified modified polypropylene. The polypropylene raw material and the purified modified polypropylene were tested for water contact angle and differential scanning calorimetry.

[0057] Water contact angle data such as Figure 2 As shown in the figure, it can be seen that with the increase in the amount of grafted monomer, the hydrophilicity of the grafted modified polypropylene gradually increases and the water contact angle decreases. The unmodified PP shows typical hydrophobic properties, and its water contact angle is 118°. After the PP is grafted and modified with MAH and AA monomers, the water contact angle of the grafted modified PP decreases. This shows that the introduction of MAH and AA polar monomers can effectively improve the surface hydrophilicity of PP and reduce the difficulty of emulsification and dispersion.

[0058] Differential scanning calorimetry data such as Figure 3 As shown in the figure, it can be seen that with the increase of the total amount of monomers, the acid value of the grafted modified PP increases, and with the increase of the grafting rate of MAH and AA monomers, the melting peak area of ​​the grafted modified PP decreases and the crystallinity decreases. This is because the introduction of anhydride and carboxyl groups will destroy the regularity of the propylene unit sequence, causing the orderly arrangement of the polypropylene molecular chain to decrease and the crystallization area to become smaller. The reduction of crystallinity is conducive to the melt emulsification of the modified PP.

[0059] Example 3

[0060] 100 parts of polypropylene PP-S1, 5 parts of maleic anhydride, 5 parts of acrylic acid, and 0.5 parts of diisopropylbenzene peroxide were stirred and pre-mixed, and then put into a mixer for melt grafting reaction. The mixing temperatures were set to 150°C, 160°C, 170°C, 180°C, and 190°C, respectively. The mixing time was 10 min and the rotor speed was 20 r / min.

[0061] After the reaction is completed, the grafted product is taken out, heated with xylene to dissolve the grafted product, acetone is added for precipitation, filtered and dried to obtain purified modified polypropylene. The purified modified polypropylene is subjected to acid-base chemical titration test, and the results are as follows: Figure 4As shown. It can be seen that with the increase of grafting temperature, the decomposition rate of the initiator is accelerated, the concentration of free radicals increases, the collision probability of the grafted monomer and the polypropylene free radical increases, and the acid value of the modified PP increases. However, too high a grafting temperature will cause the initiator to decompose too quickly, the concentration of the generated free radicals is too high, aggravating side reactions such as monomer self-polymerization, and the acid value of the modified PP is reduced. The preferred grafting temperature is 180°C.

[0062] Example 4

[0063] 100 parts of polypropylene PP-S1, 5 parts of maleic anhydride, 5 parts of acrylic acid, and 0.5 parts of diisopropylbenzene peroxide were stirred and pre-mixed, and then put into a mixer for melt grafting reaction. The mixing temperature was set to 180°C, the mixing times were 4 min, 8 min, 10 min, 12 min, and 16 min respectively, and the rotor speed was 20 r / min.

[0064] After the reaction is completed, the grafted product is taken out, heated with xylene to dissolve the grafted product, acetone is added for precipitation, filtered and dried to obtain purified modified polypropylene. The purified modified polypropylene is subjected to acid-base chemical titration test, and the results are as follows: Figure 5 As shown. Since the half-life of the initiator DCP at 180°C is less than 1 minute, the grafting reaction reaches a high rate at the initial stage of the reaction, and the acid value of the modified PP increases. However, as the reaction time increases, the side reactions intensify, causing the PP molecular chain to degrade and the grafted side chains to break. The preferred grafting time is 10 minutes.

[0065] Example 5

[0066] 100 parts of polypropylene PP-S2, 5 parts of maleic anhydride, 5 parts of acrylic acid, and 0.5 parts of diisopropylbenzene peroxide were stirred and pre-mixed, and then put into a mixer for melt grafting reaction. The mixing temperature was set to 180°C, the mixing time was 10 minutes, and the rotor speed was 20r / min. After the reaction, the grafted product was taken out, heated and dissolved with xylene, acetone was added for precipitation, filtered and dried to obtain purified modified polypropylene. The purified modified polypropylene was subjected to acid-base chemical titration test. The results are shown in Table 1. The modified polyacrylic acid value obtained from high molecular weight polypropylene is lower, which is not conducive to aqueous emulsification and dispersion.

[0067] Table 1 Comparison of acid values ​​of grafted products of PP with different molecular weights

[0068]

[0069] Example 6

[0070] 100 parts of polypropylene PP-S1, 10 parts of maleic anhydride, and 0.5 parts of diisopropylbenzene peroxide were stirred and pre-mixed, and then put into a mixer for melt grafting reaction. The mixing temperature was set to 180°C, the mixing time was 10 minutes, and the rotor speed was 20r / min. After the reaction, the grafted product was taken out, heated and dissolved with xylene, acetone was added for precipitation, filtered and dried to obtain purified modified polypropylene. The purified modified polypropylene was subjected to acid-base chemical titration test. The results are shown in Table 2. The grafting effect of using maleic anhydride monomer alone to graft and modify polypropylene is not ideal.

[0071] Table 2 Comparison of acid values ​​of grafted products of different monomer types

[0072]

[0073] Example 7

[0074] The three modified polypropylenes prepared in Example 2 were used to prepare modified polypropylene aqueous emulsions. The components in the emulsions were composed of the following components by mass fraction: 20% modified polypropylene, 3% polyoxyethylene stearate, 0.5% sodium dodecylbenzene sulfonate, 0.5% stearic acid, 1% diethanolamine, and 75% deionized water. The above raw materials were put into a high-pressure reactor at one time, and the emulsification temperature was set to 170°C and the emulsification time was 140min. After the emulsification was completed, the emulsion was taken out and the particle size distribution of the emulsion particles was measured. The results are shown in Table 3. As the acid value of the grafted modified PP increases, the hydrophilicity of the grafted modified polypropylene is enhanced, the difficulty of being emulsified and dispersed by the water phase is reduced, and the particle size of the emulsion particles is reduced.

[0075] Table 3 Melt emulsification results of grafted modified PP with different acid values

[0076]

[0077] Example 8

[0078] The modified polypropylene prepared in Example 1 is used to prepare a modified polypropylene aqueous emulsion. The components in the emulsion are composed of the following components by mass fraction: 20% modified polypropylene, 3% polyoxyethylene stearate, 0.5% sodium dodecylbenzene sulfonate, 0.5% stearic acid, 1% diethanolamine, and 75% deionized water. The above raw materials are put into a high-pressure reactor at one time, and the emulsification temperatures are set to 150°C, 160°C, 170°C, and 180°C, respectively, and the emulsification time is 140 minutes. After the emulsification is completed, the emulsion is taken out and the particle size distribution of the emulsion particles is measured. The results are as follows: Figure 6 shown.

[0079] like Figure 6 As shown in Figure 2, as the emulsification temperature increases, the average particle size of the emulsion decreases. Figure 3It can be seen that the melting temperature range of modified PP is 140-160℃. The melt emulsification process requires the modified PP to be transformed from a solid state to a molten state. When the emulsification temperature is low, it is difficult for the modified PP to absorb enough heat in a short time to completely transform into a molten state. The melt viscosity is large, resulting in a larger emulsion particle size. The preferred emulsification temperature is 160-180℃.

[0080] Example 9

[0081] The modified polypropylene prepared in Example 1 is used to prepare a modified polypropylene aqueous emulsion. The components in the emulsion are composed of the following components by mass fraction: 20% modified polypropylene, 3% polyoxyethylene stearate, 0.5% sodium dodecylbenzene sulfonate, 0.5% stearic acid, 1% diethanolamine, and 75% deionized water. The above raw materials are put into a high-pressure reactor at one time, and the emulsification temperature is set to 170°C. The emulsification time is 110min, 140min, 170min, and 200min respectively. After the emulsification is completed, the emulsion is taken out and the particle size distribution of the emulsion particles is measured. The results are as follows: Figure 7 shown.

[0082] like Figure 7 As shown in the figure, as the emulsification time increases, the average particle size of the emulsion decreases. During the emulsification process, the modified PP comes into contact with the high-temperature water phase, the particles gradually melt from the outside to the inside, and the surface melt is continuously peeled off by the water phase. The preferred emulsification time is 140-200 minutes.

[0083] Application Example 1

[0084] The surface of the glass fiber was coated with the modified polypropylene aqueous emulsion prepared at an emulsification temperature of 170°C and an emulsification time of 140 min in Example 8, and then dried in an oven to remove water, and then heat treated at 200°C. The microscopic morphology of the original glass fiber and the modified glass fiber was observed, and the results were as follows: Figure 8 As shown in the figure, the surface roughness of the glass fiber treated with PP emulsion coating is significantly increased, which is beneficial to the composite molding of the fiber and the matrix material.

[0085] Application Example 2

[0086] The surface of the glass fiber was coated with the modified polypropylene aqueous emulsion prepared at an emulsification temperature of 170°C and an emulsification time of 140 min in Example 8, 30 parts of glass fiber were stirred and mixed with 20 parts of the modified polypropylene aqueous emulsion, dried in an oven to remove water, and then 100 parts of polypropylene resin material were added and put into a mixer for melt mixing at one time. The mixing temperature was set to 200°C, the mixing time was set to 10 min, and the rotor speed was set to 20 r / min to obtain a GFRPP composite material.

[0087] After mixing, the composite material was taken out and a standard specimen was prepared using a micro injection molding machine to measure the mechanical properties of the composite material. The results are as follows Fig. 9 As shown, the cross-sectional microstructure of the composite material was observed. Fig.10 shown.

[0088] It can be seen that compared with the untreated GFRPP composite material, the GFRPP composite material with the modified polypropylene aqueous emulsion has improved tensile strength, flexural strength and notched impact strength. Fig.10 As shown, from the cross-sectional morphology of the composite material, it can be found that the surface of the glass fiber in the untreated GFRPP is smooth and the interface compatibility between the fiber and the matrix material is poor; while in the GFRPP with the addition of modified polypropylene aqueous emulsion, the interface bonding between the fiber and the matrix material is stronger.

Claims

1. A method for preparing a modified polypropylene aqueous emulsion, characterized in that: Includes steps: Step 1, premixing raw materials including polypropylene, anhydride monomers, acrylic monomers and initiators, and mixing and melting to obtain modified polypropylene; Step 2, mixing the modified polypropylene, the composite surfactant and water to melt and emulsify to obtain the modified polypropylene aqueous emulsion; The raw materials include 100 parts of polypropylene, 0.2-1.5 parts of initiator, 1-7.5 parts of anhydride monomer, and 1-7.5 parts of acrylic acid monomer in parts by mass; The total amount of anhydride monomers and acrylic acid monomers in the raw materials is 5-10 parts; the mass ratio of anhydride monomers to acrylic acid monomers in the raw materials is 1:0.8-1.

2.

2. The method for preparing the modified polypropylene aqueous emulsion according to claim 1, characterized in that: The weight average molecular weight of the polypropylene is less than 100,000.

3. The method for preparing the modified polypropylene aqueous emulsion according to claim 1, characterized in that: The anhydride monomers include maleic anhydride and / or methacrylic anhydride; The acrylic monomer includes one or more of acrylic acid, methacrylic acid, methyl acrylate, and methyl methacrylate; The initiator includes one or more of dicumyl peroxide, di-tert-butyl peroxide, and benzoyl peroxide.

4. The method for preparing the modified polypropylene aqueous emulsion according to claim 1, characterized in that: The raw materials of the modified polypropylene aqueous emulsion in step 2 include 10-30% modified polypropylene, 2-15% composite surfactant, and 55-88% deionized water according to mass fraction.

5. The method for preparing the modified polypropylene aqueous emulsion according to claim 1, characterized in that: The composite surfactant comprises a nonionic surfactant, an anionic surfactant, an emulsifier and a neutralizing base; the mass ratio of each component is 5-8:0.5-1.5:0.5-1.5:1-3.

6. The method for preparing the modified polypropylene aqueous emulsion according to claim 5, characterized in that: The nonionic surfactant includes one or more of polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, and polyoxyethylene stearate; The anionic surfactant includes one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate; The auxiliary emulsifier includes one or more of stearic acid, palmitic acid, and oleic acid; The neutralizing base includes one or more of ethanolamine, diethanolamine, and triethanolamine.

7. The method for preparing the modified polypropylene aqueous emulsion according to claim 1, characterized in that: The temperature of the mixing and melting in step 1 is 150-200° C., and the mixing time is 4-16 min.

8. The method for preparing the modified polypropylene aqueous emulsion according to claim 1, characterized in that: In step 2, the emulsification temperature is 150-180° C., and the emulsification time is 110-200 min.

9. The modified polypropylene aqueous emulsion prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The average particle size of the modified polypropylene aqueous emulsion is 100-5000nm.

10. Use of the modified polypropylene aqueous emulsion according to claim 9 in a composite system of polypropylene and glass fiber.

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