Nanocellulose fiber modified core-shell polymer particles and preparation method thereof

Abstract

The invention discloses a nano-cellulose fiber modified core-shell polymer particle and a preparation method thereof, wherein the nano-cellulose fiber modified core-shell polymer particle is composed of nano-cellulose fiber and core-shell polymer particles, and the preparation method includes: the following components by weight are polymerized by free radical initiation: 0.2-20 weight parts of modified nano-cellulose fiber, 20-120 weight parts of soft monomer, 3-40 weight parts of hard monomer, 0.5-3 weight parts of initiator, and 100-600 weight parts of water. The nano-cellulose fiber modified core-shell polymer particles obtained by the present invention have various sources, the inner shell layer of the core-shell polymer particles can be biomass or petroleum-based, and the outer shell layer can increase the formability and functionality of the core-shell particles, and have good toughening effect; nano-cellulose fiber is loaded on the core-shell polymer particles as a reactive emulsifier and has excellent reinforcing efficiency, so polymer toughening and strengthening can be realized simultaneously, and industrial production can be easily realized, and there is a good application prospect in industries such as packaging.

Description

Technical Field

[0001] The invention relates to the technical field of core-shell polymer particles, and in particular to nanocellulose fiber-modified core-shell polymer particles and a preparation method thereof. Background Art

[0002] Core-shell polymer particles refer to a type of structured composite particles obtained by emulsion polymerization of two or more monomers. They are composed of at least two substances with different chemical compositions, showing a double-layer or multi-layer structure, and their properties are jointly determined by the core and shell components. The structure of core-shell polymer particles is highly controllable, and the performance of the matrix can be improved by regulating the particle size, incorporation amount, core-shell ratio and compatibility with the matrix. They have broad development prospects in the field of polymer resin toughening. However, due to the presence of the soft shell layer, the strength of the toughened polymer is inevitably reduced, making it difficult to achieve a simultaneous increase in toughness and strength.

[0003] Based on the above facts, this patent develops a nanocellulose fiber modified core-shell polymer particle, which utilizes the high strength and high modulus characteristics of nanocellulose fibers to achieve an increase in the strength of the toughened polymer. Patents CN 110423434 B and CN 201510362426.6 use soap-free emulsion polymerization to prepare hard core (starch)-soft shell (polyethyl acrylate) particles for toughening polylactic acid. The results show that the toughness of polylactic acid has been significantly improved, but the strength has decreased significantly. Therefore, this patent uniformly loads the modified nanocellulose fibers on the core-shell polymer particles, so that it has both the toughening of the core-shell polymer particles and the strengthening of the nanocellulose fibers, which can not only improve the toughness of the polymer matrix but also enhance the matrix. Therefore, it is of great significance to develop a core-shell polymer particle that has both strengthening and toughening functions and controllable performance. Summary of the invention

[0004] The object of the present invention is to provide a nanocellulose fiber modified core-shell polymer particle and a preparation method thereof. The monomers of the nanocellulose fiber modified core-shell polymer particle of the present invention have a wide range of sources and a wide variety, and can be petroleum-based or bio-based. The addition of nanocellulose fibers helps to improve the reinforcing efficiency of the core-shell polymer particles in the matrix. At the same time, the structure of the core-shell polymer particles is controllable and easy to shape and process, and is suitable for toughening and reinforcing various polymer matrices.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing nanocellulose fiber modified core-shell polymer particles comprises the following steps:

[0007] Step 1: Preparation of pretreated nanocellulose fibers containing double bonds:

[0008] Catalysis of nanocellulose fibers: After the nanocellulose fibers and the solvent are evenly mixed, the catalyst is added dropwise, and then stirred at 20°C-60°C for 0.5-3 hours;

[0009] Modification of nanocellulose fibers: adding a modifier dropwise while stirring, stirring at 20°C-40°C for 0.5-3 hours, adding anhydrous ethanol for washing, filtering and drying to obtain pretreated nanocellulose fibers;

[0010] Wherein, the pretreatment reagent is one or a combination of acryloyl chloride, maleic anhydride, stearyl chloride, methacrylic acid, acrylic acid, methacryloyl chloride, cinnamoyl chloride, and 2-fluoroacryloyl chloride. The degree of substitution of the modified nanocellulose fiber containing double bonds is in the range of 0.01-2.4;

[0011] Step 2: Preparation of nanocellulose fiber modified core-shell polymer particles:

[0012] The pretreated nanocellulose fibers, hard monomers and deionized water are mixed and emulsified, and the temperature is raised;

[0013] Add initiator, polymerize;

[0014] Then, a soft monomer is added, and an initiator is added to prepare a nanocellulose fiber-modified core-shell polymer particle emulsion;

[0015] The emulsion is broken to obtain nanocellulose fiber-modified core-shell polymer particles.

[0016] As a further solution of the present invention: the raw material of the nanocellulose fiber is selected from at least one of cotton pulp, wood pulp and bamboo pulp.

[0017] As a further embodiment of the present invention: the solvent is at least one of dimethylformamide, chloroform, tetrahydrofuran, ethyl acetate, butyl acetate and methyl acetate.

[0018] As a further embodiment of the present invention: the catalyst is at least one of pyridine, pyrrole, ethylenediamine, trimethylamine and triethylamine.

[0019] As a further embodiment of the present invention: the modifier is at least one of an acid containing a double bond, an amide, a silane coupling agent, an isocyanate and an epoxy compound containing a double bond.

[0020] As a further embodiment of the present invention, the soft monomer comprises one or a combination of itaconic acid, oleic acid, fumaric acid, linoleic acid, linolenic acid, ricinoleic acid, itaconic acid fatty esters, oleic acid fatty esters, fumaric acid fatty esters, linoleic acid fatty esters, linolenic acid fatty esters, undecylenic acid, undecylenal, citronellal, citronellol, citronellyl acetate, muconic acid, muconic acid esters, myrcene, citral, nerol, undecylenic acid esters, ethyl acrylate, butyl acrylate, isooctyl acrylate, ethylene, lauryl acrylate, 2-ethylhexyl acrylate, and lauryl methacrylate.

[0021] As a further embodiment of the present invention: the hard monomer includes one or a combination of methyl acrylate, vinyl acetate, styrene, vinyl chloride, acrylonitrile, methyl methacrylate, acrylamide, glycidyl methacrylate, glycidyl linoleate, glycidyl linolenate, glycidyl oleate, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-methacryloxymethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, and vinyltriacetoxysilane.

[0022] As a further solution of the present invention: the diameter of the hard core of the core-shell polymer particle is 30-250 nm, and the thickness of the soft shell layer is 10-80 nm.

[0023] A nanocellulose fiber-modified core-shell polymer particle, comprising a core-shell polymer particle and loaded nanocellulose fibers;

[0024] The core-shell polymer particles consist of a hard core and a soft shell; the hard core is formed by free radical polymerization of bio-based or petroleum-based hard monomers, and the shell is formed by copolymerization of bio-based or petroleum-based soft monomers;

[0025] The inner shell and the outer shell are formed by soap-free emulsion polymerization.

[0026] The invention discloses nanocellulose fiber modified core-shell polymer particles, which are prepared by polymerizing raw materials including the following components: 0.2-20 parts by weight of nanocellulose fiber, 20-120 parts by weight of soft monomer, 3-40 parts by weight of hard monomer, 0.5-3 parts by weight of initiator and 100-600 parts by weight of water.

[0027] Beneficial effects of the present invention:

[0028] The invention first prepares pretreated nanocellulose fibers containing double bonds by catalyzing and modifying nanocellulose fibers; then, the pretreated nanocellulose fibers, hard monomers and deionized water are mixed and emulsified, and the temperature is increased; an initiator is added to polymerize; then, a soft monomer is added and an initiator is supplemented to prepare a nanocellulose fiber modified core-shell polymer particle emulsion; and the emulsion is broken to obtain nanocellulose fiber modified core-shell polymer particles;

[0029] The nanocellulose fiber-modified core-shell polymer particles obtained by the preparation method provided by the present invention use nanocellulose as a reactive emulsifier to avoid the use of traditional emulsifiers in the core-shell polymer emulsion polymerization process, and give the core-shell polymer particles enhanced performance. The particles use a wide range of raw materials, have controllable structures and properties, and have both toughening and strengthening functions. The nanocellulose fiber-modified core-shell polymer particles of the present invention are suitable for toughening and strengthening of various polymers, and can be mixed with polymers on traditional simple synthesis equipment, with a simple process and easy industrial production;

[0030] The nanocellulose fiber modified core-shell polymer particles of the present invention include modified nanocellulose fibers and core-shell polymer particles having an inner core and an outer shell. Both the inner shell and the outer shell can be prepared by copolymerization of bio-based monomers or petroleum-based monomers. At the same time, the core-shell structure is controllable, the particles are easy to shape and process, and are suitable for blending, toughening, and strengthening of various polymers. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] 1. Preparation of pretreated nanocellulose fibers

[0033] Example 1

[0034] 10 parts by weight of nanocellulose fibers and 30 parts by weight of chloroform were mixed and stirred thoroughly, then 1.0 parts by weight of pyridine was gradually added dropwise, and the mixture was heated to 20°C-60°C and stirred thoroughly for 0.5-3 hours, then 1.5 parts by weight of acryloyl chloride was added dropwise and stirred at 20°C-40°C for 0.5-3 hours, then anhydrous ethanol was added for washing, and the mixture was filtered and dried to obtain pretreated nanocellulose fibers.

[0035] Example 2

[0036] 10 parts by weight of nanocellulose fibers and 15 parts by weight of ethyl acetate were mixed and stirred thoroughly, then 2.0 parts by weight of pyridine were gradually added dropwise, and the mixture was heated to 20°C-60°C and stirred thoroughly for 0.5-3 hours, then 1.0 parts by weight of maleic anhydride was added dropwise and stirred at 20°C-40°C for 0.5-3 hours, then anhydrous ethanol was added for washing, and the mixture was filtered and dried to obtain pretreated nanocellulose fibers.

[0037] 2. Preparation of Nanocellulose Modified Core-Shell Polymer Particles

[0038] Example 3

[0039] 5 parts by weight of the pretreated nanocellulose fibers in Example 1 were mixed with 60 parts by weight of styrene and added to 400 parts by weight of deionized water. The mixture was stirred at room temperature for 30 minutes. Then, 0.5 parts by weight of initiator potassium persulfate was added. The temperature was raised, stirred and polymerization was initiated. The reaction was continued for 6 hours. 150 parts of butyl acrylate was added and the reaction was continued for 6 hours. Ethanol was added for washing. The nanocellulose modified core-shell polymer particles were filtered and dried to prepare the nanocellulose modified core-shell polymer particles. The particle sizes were measured and listed in Table 1.

[0040] Example 4

[0041] 10 parts by weight of the pretreated nanocellulose fibers in Example 1 were mixed with 50 parts by weight of vinyl chloride and added to 500 parts by weight of deionized water. The mixture was stirred at room temperature for 30 minutes. Then, 2 parts by weight of initiator azobisisobutyronitrile were added. The temperature was raised, stirred and polymerization was initiated. The reaction lasted for 6 hours. 300 parts by weight of acrylonitrile were added and the reaction was continued for 6 hours. Ethanol was added for washing. The nanocellulose modified core-shell polymer particles were filtered and dried to prepare the nanocellulose modified core-shell polymer particles. The particle sizes were measured and listed in Table 1.

[0042] Example 5

[0043] 10 parts by weight of the pretreated nanocellulose fibers in Example 2 were mixed with 180 parts by weight of methyl acrylate and added to 600 parts by weight of deionized water. The mixture was stirred at room temperature for 30 minutes. Then, 3 parts by weight of initiator potassium persulfate were added. The temperature was raised, stirred and polymerization was initiated. The reaction was continued for 6 hours. 60 parts by weight of butyl acrylate was added and the reaction was continued for 6 hours. Ethanol was added for washing. The nanocellulose modified core-shell polymer particles were filtered and dried to prepare the nanocellulose modified core-shell polymer particles. The particle sizes were measured and listed in Table 1.

[0044] Example 6

[0045] In Example 2, 20 parts by weight of pretreated nanocellulose fibers and 100 parts by weight of styrene were mixed and added to 300 parts by weight of deionized water, and stirred at room temperature for 30 minutes. Then, 1 part by weight of initiator potassium persulfate was added, the temperature was raised, stirred and polymerization was initiated, and the reaction was carried out for 6 hours. 200 parts by weight of ethyl acrylate was added, and the reaction was continued for 6 hours. Ethanol was added for washing, and the nanocellulose modified core-shell polymer particles were filtered and dried to prepare the nanocellulose modified core-shell polymer particles. The measured particle size is listed in Table 1.

[0046] Comparative Example 1

[0047] 10 parts by weight of untreated nanocellulose fibers and 40 parts by weight of styrene were mixed and added to 150 parts by weight of deionized water, and stirred at room temperature for 30 minutes. Then, 1.5 parts by weight of initiator potassium persulfate were added, the temperature was raised, stirred and polymerization was initiated, and the reaction was carried out for 6 hours. 120 parts by weight of ethyl acrylate was added and the reaction was continued for 6 hours. Ethanol was added for washing, and the nanocellulose fiber-modified core-shell polymer particles were prepared by suction filtration and drying. The particle size was measured and listed in Table 1.

[0048] Comparative Example 2

[0049] 20 parts by weight of untreated nanocellulose fibers and 100 parts by weight of vinyl chloride were mixed into 600 parts by weight of deionized water, and stirred at room temperature for 30 minutes. Then, 3.0 parts by weight of initiator potassium persulfate were added, the temperature was raised, and the polymerization was initiated by stirring. The reaction lasted for 6 hours. 250 parts by weight of methyl undecylenate were added, and the reaction was continued for 6 hours. Ethanol was added for washing, and the nanocellulose fiber-modified core-shell polymer particles were prepared by suction filtration and drying. The particle sizes were measured and listed in Table 1.

[0050] Comparative Example 3

[0051] 50 parts by weight of methyl acrylate were added to 500 parts by weight of deionized water, and an emulsifier, sodium stearate, was added, and the mixture was stirred at room temperature for 30 minutes. Then, 1.5 parts by weight of an initiator, ammonium persulfate, was added, the temperature was raised, and the polymerization was initiated by stirring. The reaction was continued for 6 hours. 100 parts by weight of butyl acrylate was added, and the reaction was continued for 6 hours. Ethanol was added for washing, and the mixture was filtered and dried to prepare core-shell polymer particles. The particle sizes were measured and listed in Table 1.

[0052] 3. Preparation of polylactic acid composition

[0053] Example 7

[0054] The nanocellulose modified core-shell polymer particles prepared in Example 3 were melt-blended with polylactic acid at a mass ratio of 20:80, with a processing temperature of 175° C. and a blending time of 5 min.

[0055] Example 8

[0056] The nanocellulose modified core-shell polymer particles prepared in the example were melt-blended with polylactic acid at a mass ratio of 20:80, with a processing temperature of 175° C. and a blending time of 5 min.

[0057] Comparative Example 4

[0058] The nanocellulose modified core-shell polymer particles prepared in Comparative Example 2 were melt-blended with polylactic acid at a mass ratio of 20:80, with a processing temperature of 175° C. and a blending time of 5 min.

[0059] Comparative Example 5

[0060] The nanocellulose modified core-shell polymer particles prepared in Comparative Example 3 were melt-blended with polylactic acid at a mass ratio of 20:80, with a processing temperature of 175° C. and a blending time of 5 min.

[0061] Comparative Example 6

[0062] 50 parts by weight of polylactic acid were weighed and melt-blended using a Hake internal mixer at a processing temperature of 175° C. for a blending time of 5 min.

[0063] The polylactic acid compositions obtained in the above-mentioned Examples 7-8 and Comparative Examples 4-6 were hot pressed into sheets, and their tensile properties and impact properties were tested. The test methods and implementation standards selected by the present invention are as follows:

[0064] The tensile performance test was carried out in accordance with GB / T1040.2-2006, with a tensile rate of 10 mm / min; the impact performance test was carried out in accordance with GB / T1043.1-2008, using the simply supported beam notched specimen impact method. The results are shown in Table 2:

[0065] Table 1

[0066] sample Particle size Particle Formability Comparative Example 1 220nm Difference Comparative Example 2 195nm Difference Comparative Example 3 150nm Difference Example 3 175nm good Example 4 330nm good Example 5 180nm good Example 6 205nm good

[0067] Table 2

[0068]

[0069] As can be seen from Table 1, the final particles in Comparative Examples 1-3 have poor formability, while the nanocellulose modified core-shell polymer particles in the present invention have good formability. This is because nanocellulose has hydrophilic and lipophilic amphiphilic characteristics after modification, which can better prevent monomer aggregation during emulsion polymerization. As can be seen from Table 2, the nanocellulose modified core-shell polymer particles in Examples 7-8 of the present invention and Comparative Examples 4-6 have different degrees of effect on the toughening and strengthening of polylactic acid, but it is obvious that the modified nanocellulose fiber modified core-shell particles of the present invention have better toughening and strengthening effects on polylactic acid. This is because nanocellulose itself has high strength and modulus, and after being compounded with core-shell particles, it has a better strengthening effect on polylactic acid.

[0070] The monomers used in the nanocellulose modified core-shell particles obtained by the present invention are widely sourced and diverse in type, and the core-shell particle structure, particle size, glass transition temperature and other properties are controllable. The core and shell of the core-shell particles can synergistically strengthen polylactic acid, and the nanocellulose fibers loaded on the core-shell polymer particles as a reactive emulsifier have excellent strengthening performance, so polymer toughening and strengthening can be achieved at the same time.

[0071] The above is a detailed description of an embodiment of the present invention, but the content is only a preferred embodiment of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing nanocellulose fiber modified core-shell polymer particles, characterized in that: The following steps are involved: Step 1: Preparation of pretreated nanocellulose fibers containing double bonds: Catalysis of nanocellulose fibers: After the nanocellulose fibers and the solvent are evenly mixed, the catalyst is added dropwise, and then stirred at 20°C-60°C for 0.5-3 hours; Modification of nanocellulose fibers: adding a modifier dropwise while stirring, stirring at 20°C-40°C for 0.5-3 hours, adding anhydrous ethanol for washing, filtering and drying to obtain pretreated nanocellulose fibers; Wherein, the modifier is one or a combination of acryloyl chloride, maleic anhydride, stearyl chloride, methacrylic acid, acrylic acid, methacryloyl chloride, cinnamoyl chloride, and 2-fluoroacryloyl chloride; the degree of substitution of the modified nanocellulose fiber containing double bonds is in the range of 0.01-2.4; Step 2: Preparation of nanocellulose fiber modified core-shell polymer particles: The pretreated nanocellulose fibers, hard monomers and deionized water are mixed and emulsified, and the temperature is raised; Add initiator, polymerize; Then, a soft monomer is added, and an initiator is added to prepare a nanocellulose fiber-modified core-shell polymer particle emulsion; Demulsification to obtain nanocellulose fiber-modified core-shell polymer particles; The soft monomer includes one or a combination of itaconic acid, oleic acid, fumaric acid, linoleic acid, linolenic acid, ricinoleic acid, itaconic acid fatty esters, oleic acid fatty esters, fumaric acid fatty esters, linoleic acid fatty esters, linolenic acid fatty esters, undecylenic acid, undecylenal, citronellal, citronellol, citronellyl acetate, muconic acid, muconic acid esters, myrcene, citral, nerol, undecylenic acid esters, ethyl acrylate, butyl acrylate, isooctyl acrylate, ethylene, lauryl acrylate, 2-ethylhexyl acrylate, and lauryl methacrylate; The hard monomers include one or a combination of methyl acrylate, vinyl acetate, styrene, vinyl chloride, acrylonitrile, methyl methacrylate, acrylamide, glycidyl methacrylate, glycidyl linoleate, glycidyl linolenate, glycidyl oleate, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-methacryloxymethyldimethoxysilane, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, and vinyltriacetoxysilane.

2. The method for preparing nanocellulose fiber modified core-shell polymer particles according to claim 1, characterized in that: The raw material of the nanocellulose fiber is selected from at least one of cotton pulp, wood pulp and bamboo pulp.

3. The method for preparing nanocellulose fiber modified core-shell polymer particles according to claim 1, characterized in that: The solvent is at least one of dimethylformamide, chloroform, tetrahydrofuran, ethyl acetate, butyl acetate, and methyl acetate.

4. The method for preparing nanocellulose fiber modified core-shell polymer particles according to claim 1, characterized in that: The catalyst is at least one of pyridine, pyrrole, ethylenediamine, trimethylamine and triethylamine.

5. The method for preparing nanocellulose fiber modified core-shell polymer particles according to claim 1, characterized in that: The modifier is at least one of an acid containing a double bond, an amide, a silane coupling agent, an isocyanate and an epoxy compound containing a double bond.

6. The method for preparing nanocellulose fiber modified core-shell polymer particles according to claim 1, characterized in that: The diameter of the hard core of the core-shell polymer particles is 30-250 nm, and the thickness of the soft shell layer is 10-80 nm.

7. A nanocellulose fiber modified core-shell polymer particle, characterized in that: The nanocellulose fiber-modified core-shell polymer particles prepared by the method described in any one of claims 1 to 6 above; comprising core-shell polymer particles and loaded nanocellulose fibers; The core-shell polymer particles consist of a hard core and a soft shell; the hard core is formed by free radical polymerization of bio-based or petroleum-based hard monomers, and the shell is formed by copolymerization of bio-based or petroleum-based soft monomers; The inner shell and the outer shell are formed by soap-free emulsion polymerization.

8. The nanocellulose fiber-modified core-shell polymer particles according to claim 7, characterized in that: The nano-cellulose fiber modified core-shell polymer particles are polymerized from raw materials including the following components: 0.2-20 parts by weight of nano-cellulose fiber, 20-120 parts by weight of soft monomer, 3-40 parts by weight of hard monomer, 0.5-3 parts by weight of initiator and 100-600 parts by weight of water.

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