阅读说明：本技术 一种聚丙烯薄膜用永久抗静电母料及其制备方法和薄膜 (Permanent antistatic master batch for polypropylene film, preparation method thereof and film ) 是由 罗吉江 符书臻 于 2021-11-01 设计创作，主要内容包括：一种聚丙烯薄膜用永久抗静电母料,包括以改性有机硅微球为永久抗静电剂,改性有机硅微球是通过酯化反应将表面处理后的碳纤维接枝于有机硅微球表面,形成有机硅微球-g-碳纤维结构,该结构一端与聚丙烯相容,另一端均匀分散在聚丙烯内。本发明利用碳纤维的表面的界面性能溶于聚丙烯本体中,有机硅微球保持其流动性能,使其能够牢固地埋覆于聚丙烯本体内不易脱出,同时碳纤维利用纤维与纤维形成三维立体交织的网状结构,从而增强了整个薄膜的导电性能,具有永久抗静电性,且还具有抗粘连性良好、高分散性和低摩擦系数等综合性能。(A permanent antistatic mother material for polypropylene film is prepared from the modified organosilicon microspheres as permanent antistatic agent through esterifying reaction to graft the carbon fibres after surface treatment to the surface of organosilicon microspheres to form organosilicon microsphere-g-carbon fibre structure, which has one end compatible with polypropylene and another end uniformly dispersed in polypropylene. The invention utilizes the interfacial property of the surface of the carbon fiber to be dissolved in the polypropylene body, the organosilicon microspheres maintain the flow property of the carbon fiber, so that the carbon fiber can be firmly embedded in the polypropylene body and is not easy to fall off, and simultaneously, the carbon fiber utilizes the fiber and the fiber to form a three-dimensional interwoven net-shaped structure, thereby enhancing the conductivity of the whole film, having permanent antistatic property and also having the comprehensive properties of good adhesion resistance, high dispersibility, low friction coefficient and the like.)

1. A permanent antistatic master batch for a polypropylene film is characterized by comprising modified organic silicon microspheres as a permanent antistatic agent; the modified organic silicon microsphere is of an organic silicon microsphere-g-carbon fiber structure, and carbon fibers are distributed on the surface of the organic silicon microsphere; the permanent antistatic master batch is a dispersion system with polypropylene as a dispersion medium; the dispersion system is a modified organic silicon microsphere-polypropylene dispersion system, and the modified organic silicon microspheres are uniformly dispersed in polypropylene;

the modified organic silicon microsphere takes an organic silicon microsphere with surface carboxylation as a raw material, and carbon fiber with surface hydroxylation is grafted on the surface of the organic silicon microsphere through an esterification reaction to form an organic silicon microsphere-g-carbon fiber structure;

one end of the organic silicon microsphere-g-carbon fiber structure is compatible with polypropylene, and the other end of the organic silicon microsphere-g-carbon fiber structure is uniformly dispersed in the polypropylene.

2. The permanent antistatic masterbatch for polypropylene film according to claim 1,

the surface hydroxylation of the carbon fiber comprises an oxidation-reduction treatment process, wherein the surface roughness is increased through oxidation treatment of concentrated nitric acid, and the hydroxylation is realized through reduction of a reducing agent; the reducing agent is lithium aluminum hydride or sodium borohydride.

3. The permanent antistatic masterbatch for polypropylene film according to claim 2, wherein the carbon fiber has a fiber length of 3 to 6 mm.

4. The permanent antistatic masterbatch for polypropylene film as claimed in claim 1, wherein the surface carboxylation of the silicone microspheres comprises adding equimolar silane coupling agent and succinic anhydride to polysiloxane microspheres to functionalize the surface carboxyl groups of the polysiloxane microspheres.

5. The permanent antistatic masterbatch for polypropylene film according to claim 4, wherein said silane coupling agent is at least one of KH550, KH5501, KH560, KH570, KH 580.

6. The permanent antistatic master batch for the polypropylene film as claimed in any one of claims 1 to 5, wherein the modified organosilicon microspheres are added in an amount of 5 to 30 percent by mass in the modified organosilicon microsphere-polypropylene dispersion system.

7. The permanent antistatic masterbatch for polypropylene film according to any one of claims 1 to 5, comprising the following components in mass percent: 60-85% of polypropylene, 10-30% of permanent antistatic agent and 5-10% of dispersing agent.

8. A preparation method of the permanent antistatic master batch for the polypropylene film as described in any one of claims 1 to 7, which is characterized by comprising the following steps:

(1) hydroxylation of carbon fibers: adding concentrated nitric acid with the mass fraction of 10-20%, carrying out oxidation etching on the carbon fiber at the temperature of 40-80 ℃, increasing the polarity and the roughness of the surface of the fiber, cooling to room temperature, washing to be neutral, and drying;

dispersing the oxidized carbon fiber in tetrahydrofuran, adding lithium aluminum hydride or sodium borohydride, stirring, washing and drying to obtain the surface-hydroxylated carbon fiber, wherein the oxygen-containing group on the surface of the carbon fiber is hydroxyl; the fiber length of the carbon fiber is 3-6 mm;

(2) surface carboxylation of organic silicon microspheres: dispersing the organic silicon microspheres in N, N-dimethylformamide, adding a silane coupling agent and succinic anhydride to obtain organic silicon microspheres with surface carboxyl functionalized, cleaning and drying to obtain carboxylated organic silicon microspheres; wherein the average grain diameter of the organic silicon microspheres is 2-6 microns;

(3) esterification grafting: dispersing the hydroxylated carbon fiber in the step (1) and the carboxylated organic silicon microsphere in the step (2) in DMF, adding dicyclohexylcarbodiimide and 4-dimethylaminopyridine, and carrying out condensation reflux under magnetic stirring to graft the carbon fiber on the organic silicon microsphere so as to form an organic silicon microsphere-g-carbon fiber structure;

(4) and (3) drying: filtering, cleaning and taking out the organic silicon microspheres reacted in the step (3) and drying to constant weight to obtain modified organic silicon microspheres;

(5) respectively adding the modified organic silicon microspheres prepared in the step (4), the compatilizer and the dispersant into polypropylene, and melting and fully mixing to form a uniform dispersion system; and then putting the uniformly mixed materials into a screw extruder, extruding in a molten state, cooling, and pelletizing to obtain the permanent antistatic master batch for polypropylene.

9. The polypropylene film adopts the permanent antistatic master batch as defined in any one of claims 1 to 8, and is characterized in that the addition amount of the permanent antistatic master batch is 5 to 20 percent by mass.

Technical Field

The invention relates to the technical field of functional additives for polypropylene films, in particular to a permanent antistatic master batch for a polypropylene film, a preparation method thereof and the film.

Background

In the packaging material, PP (polypropylene) film has very wide application in the packaging field, and with the continuous expansion of the market, the production and use of PP film are directed to high speed, high quality andthe automation direction is developed. The surface resistivity is generally 10 due to the good electrical insulation property of the high polymer¹³~10¹⁵In the prior art, the method for solving the net charge on the surface of the film is mainly to add an antistatic agent, and the antistatic agent used on the PP film can be divided into two categories of common antistatic agents and permanent antistatic agents. The aging time of the former is 3-5 months, and the surface resistivity is generally 10¹³~10¹⁵M, this aging time is not satisfactory for particular long-term use articles, and there is a need for film articles having permanent antistatic properties to meet the prior art need for long-term sustained antistatic properties. Carbon fiber is widely applied to the fields of plastics, coatings and films as an excellent antistatic agent, in the prior art, carbon fiber is usually directly added and mixed as the antistatic agent, and static electricity is eliminated by utilizing the conductivity of the carbon fiber, but the effect cannot be lasting, firstly, the dispersion performance of the carbon fiber is poor, the carbon fiber is easy to agglomerate by directly adding, and particularly, when the carbon fiber is extremely high in length for obtaining more excellent conductivity, the longer the fiber, the worse the dispersion performance is, and the more serious the agglomeration is caused. Secondly, the carbon fiber has low surface energy, few active functional groups and chemically inert surface, so that the compatibility with a resin matrix is poor. Therefore, the carbon fibers as an antistatic agent are directly added to the resin, resulting in detachment thereof and disappearance of antistatic properties over a long period of time.

The invention of China patent CN104403175A discloses a permanent antistatic polyolefin master batch, which mainly adopts antistatic agent which is conductive material and reinforced conductive powder as antistatic filler, and is one or a combination of carbon powder, carbon fiber, metal powder and metal fiber, but in actual use, the powdery conductive powder is dispersed and difficult, and the addition amount is very large, so a large amount of dispersant is needed, the processing technology is complex, the cost is high, and the comprehensive performance is poor.

Chinese invention patent CN108084567A discloses a low-haze anti-blocking master batch for polypropylene and a preparation method thereof, wherein an organic silicon microsphere is used as an anti-blocking agent, and the incompatible property and the flowing property of the organic silicon microsphere and a polypropylene film are mainly utilized, so that the organic silicon microsphere can migrate to the surface of the film in the processing process to obtain the polypropylene film with smooth surface. However, in the using process, especially in the use environment with large friction, the organic silicon microspheres are easy to be separated from the surface of the film, so that the film is easy to wear.

Disclosure of Invention

The invention aims to provide a permanent antistatic master batch for a polypropylene film, a preparation method thereof and the film, wherein carbon fibers are grafted on modified organic silicon microspheres, so that the carbon fibers can migrate on the surface of the film and are uniformly distributed, the dispersibility is good, the permanent antistatic performance is formed, and the permanent antistatic master batch has the advantages of smoothness, anti-adhesion performance and good comprehensive performance.

In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows: a permanent antistatic master batch for polypropylene films comprises modified organic silicon microspheres as a permanent antistatic agent; the modified organic silicon microsphere is of an organic silicon microsphere-g-carbon fiber structure, and carbon fibers are distributed on the surface of the organic silicon microsphere.

Furthermore, the permanent antistatic master batch for the polypropylene film is a uniform dispersion system taking polypropylene as a dispersion medium; the dispersion system is a modified organic silicon microsphere-polypropylene dispersion system, and the modified organic silicon microspheres are uniformly dispersed in polypropylene; the modified organic silicon microsphere takes an organic silicon microsphere subjected to surface carboxylation as a raw material, and carbon fiber subjected to surface hydroxylation is grafted on the surface of the organic silicon microsphere through an esterification reaction to form an organic silicon microsphere-g-carbon fiber structure; one end of the organic silicon microsphere-g-carbon fiber structure is compatible with polypropylene, and the other end of the organic silicon microsphere-g-carbon fiber structure is uniformly dispersed in the polypropylene.

Further, the fiber length of the carbon fiber is 3-6 mm.

Further, the surface hydroxylation of the carbon fiber comprises an oxidation-reduction treatment process, wherein the oxidation treatment is performed by concentrated nitric acid to increase the surface roughness, and then the reduction is performed by a reducing agent to realize hydroxylation; the reducing agent is lithium aluminum hydride or sodium borohydride. The surface hydroxylation treatment process can effectively improve the interface bonding property of the carbon fiber reinforcement and the matrix of the organic silicon microsphere, increase the grafting rate with the organic silicon microsphere and obviously improve the antistatic property.

Further, the surface carboxylation of the organic silicon microsphere comprises the steps of dispersing the organic silicon microsphere in DMF and adding silane coupling agent and succinic anhydride in an equal molar ratio to functionalize the carboxyl on the surface of the polysiloxane microsphere. The silane coupling agent is at least one of KH550, KH5501, KH560, KH570 and KH 580.

Further, the dispersing agent comprises one or more of silane, polypropylene wax, hexenyl bis stearamide and erucamide.

Further, the paint comprises the following components in percentage by mass: 60-85% of polypropylene, 10-30% of modified organic silicon resin and 5-10% of dispersing agent. The invention takes polypropylene as a main body as a dispersion medium, adds modified organic silicon microspheres as a permanent antistatic agent and is assisted by a dispersant, and improves the dispersibility of the organic silicon microspheres, thereby forming a uniform dispersion system. The silicone microspheres are not compatible with polypropylene and are free-flowing in nature, so that the ungrafted silicone microspheres will flow automatically to the surface of the polypropylene. The compatibility of the grafted organosilicon microsphere end and polypropylene is still poor, but the interface polarity of the carbon fiber end is reduced on the surface of the carbon fiber after oxidation treatment, so that the interface wettability and compatibility between the carbon fiber and a polymer matrix are improved, and the carbon fiber end can be compatible with the polypropylene. On the other hand, the carbon fiber after oxidation treatment has large surface roughness, so that interface bonding action is generated between the fiber and the fiber, the fiber and the fiber are mutually interwoven to form a three-dimensional structure and are dispersed in the polypropylene body, and the organic silicon microspheres grafted with the fiber and the organic silicon microspheres can be uniformly dispersed in the polypropylene body to form a uniform system.

In the technical scheme, the carbon fiber composite material can further comprise a compatilizer to improve the compatibility of the carbon fiber and polypropylene, wherein the compatilizer is at least one of PP graft copolymer PP-g-MAH, PP-g-MI, PP-g-AA, PP-g-GMA and derivatives of PP graft maleic anhydride, and the addition amount of the compatilizer is 0-10%.

The invention has the following function principle:

the organic silicon microsphere is a multifunctional special organic silicon resin microsphere, is white regular free-flowing spherical fine micro powder, has a three-dimensional cross-linked reticular molecular structure, and shows excellent heat resistance and dispersion performance. However, the surface of the organic silicon microsphere has strong inorganic silicon-oxygen bonds, which causes the problem of compatibility when the siloxane microsphere is applied to most organic polymer materials, and if the carbon fibers are directly grafted on the organic silicon microsphere, the carbon fibers are poor in compatibility with the polypropylene body, so that the carbon fibers and the polypropylene film are separated from each other at an interface, and permanent antistatic performance cannot be achieved. Therefore, the technical problem to be solved by the invention is to improve the compatibility problem of the organic silicon microspheres and the polypropylene matrix and simultaneously maintain the flow property of the organic silicon microspheres so that the organic silicon microspheres can be distributed on the surface of a film to keep the smooth anti-adhesion property of the organic silicon microspheres on the basis of permanent antistatic.

The organic silicon microsphere adopts polysiloxane microsphere (PSQ for short), and has a chemical formula of RSiO_3/2The polymer is a polymer which takes a repeated-Si-O-Si-bond as a main chain and directly connects various organic groups on a silicon atom, wherein the organic groups can be methyl, vinyl, phenyl, mercaptopropyl, aminopropyl and the like, and the organic groups are spherical microspheres with the diameter from a few nanometers to thousands of nanometers in geometric form. The average grain size of the organic silicon microspheres is 2-5 microns.

The carbon fiber is composed of graphite sheet layers formed by condensed polycyclic aromatic hydrocarbon, belongs to a two-dimensional disordered-layer graphite structure, graphite microcrystals are distributed unevenly in the whole body and present a skin-core structure distribution, the microcrystals of an internal core layer have smaller size and a loose structure and contain cracks and holes; the surface 'skin' layer is a homogeneous polycrystalline structure with preferred orientation along the fiber axis, and the microcrystals have larger size, are arranged orderly and have higher degree of order. Therefore, the untreated carbon fiber has smooth surface, high inertness, low surface energy, few types and numbers of active functional groups and poor interface bonding performance with resin, and the carbon fiber is directly added into the base material, so that the carbon fiber is incompatible with the resin, and permanent antistatic performance cannot be obtained.

Therefore, the invention carries out surface modification on the carbon fiber and the organosilicon microsphere respectively, introduces active groups respectively and then carries out esterification reaction, thereby grafting the carbon fiber on the organosilicon microsphere to form an organosilicon microsphere-g-carbon fiber structure which is uniformly dispersed in a polypropylene main body, and the grafted organosilicon microsphere and the polypropylene form a uniform dispersion system, in short, in the organosilicon microsphere-g-carbon fiber structure, the carbon fiber can be compatible with the polypropylene to form a whole, but the organosilicon microsphere keeps the flow property of the organosilicon microsphere and is incompatible with the polypropylene, therefore, in the dispersion system, the organosilicon microsphere can carry the carbon fiber to flow and migrate in the system, namely, the problem that the organosilicon microsphere is easy to fall out of the main body due to poor compatibility is solved, and the problem that the carbon fiber is poor in dispersibility and easy to agglomerate is also solved, meanwhile, the organic silicon microsphere-g-carbon fiber structure also has permanent antistatic performance.

Specifically, the structure of the organic silicon microsphere-g-carbon fiber is similar to the core-shell structure of a high-molecular permanent antistatic agent, when the permanent antistatic agent and a polymer body are in a molten state, molecules of the antistatic agent form the densest orientation arrangement at the interface of resin and air, hydrophilic groups extend to the outside of the resin, and a monomolecular conducting layer is formed by arranging the hydrophilic groups towards the air side, so that the higher the environmental humidity is, the stronger the water absorption of the molecules of the antistatic agent is, and the more remarkable the antistatic performance is.

After the surface of the carbon fiber is subjected to oxidation etching treatment, the surface appearance of the carbon fiber becomes uneven and has certain roughness, the wettability and chemical bonding between the fiber and resin are increased, and the mechanical engagement between the fiber and the resin and between the fiber and the fiber is also increased, so that the interface bonding performance of the composite material is improved on both chemical and physical aspects, and the fusion performance between the carbon fiber and the resin is effectively enhanced. Therefore, even under the condition that the organic silicon microspheres are incompatible with the resin, the fibers and the resin are mechanically meshed, so that the modified organic silicon microspheres can be uniformly dispersed in the polypropylene body, meanwhile, the fibers and the fibers are mutually interwoven to form a three-dimensional net structure to be dissolved in the polypropylene body, and the carbon fibers and the polypropylene body have good compatibility, so that the organic silicon microspheres cannot be separated from the polypropylene body, the whole dispersion system has extremely strong conductivity, and the stability can be maintained.

Generally, the longer the fiber length of the carbon fiber is, the stronger the conductivity performance is, but the longer the fiber is, the more difficult the fiber is to disperse, so that the maximum 3mm is usually selected in the prior art, and more than 3mm cannot obtain a more antistatic effect due to agglomeration. In the invention, the carbon fiber can be pulled by the fluidity of the organic silicon microsphere, and when the mechanical meshing force between the fibers and the flow of the organic silicon microsphere reach balance, the organic silicon microsphere-g-carbon fiber structure can form a uniform and stable dispersion system in the polypropylene. The length of the carbon fiber is 3-6 mm.

More importantly, the polypropylene film prepared by the master batch prepared by the invention can still migrate to the surface of the film due to the incompatibility of the organic silicon microspheres and the polypropylene, so that the organic silicon microspheres grafted on the organic silicon microspheres can migrate along with the organic silicon microspheres, and the carbon fibers can be uniformly distributed on the surface of the film in the length direction, so that the film has permanent antistatic property; meanwhile, a large number of carbon fibers are mechanically meshed in the film to form a three-dimensional interwoven mesh structure, so that the conductivity of the whole film is enhanced.

Compared with the method of directly adding carbon fibers into a polypropylene system, the method has the advantages that the carbon fibers are poor in dispersing performance, even if a dispersing agent is added to increase the dispersing performance, only the carbon fibers are dispersed into the system and cannot migrate to the surface of the membrane and be uniformly distributed, the carbon fibers are randomly distributed in the system, only part of the carbon fibers are randomly dispersed on the surface of the membrane, and the carbon fibers cannot be uniformly distributed on the surface of the membrane along the length direction, so that the polypropylene membrane can have antistatic performance by directly adding the carbon fibers as an antistatic agent, but the antistatic performance is poor, and the antistatic performance disappears along with the prolonging of the service time.

The master batch prepared by adding the modified organic silicon microspheres into the polypropylene not only has an antistatic effect, but also can form a plurality of bulges or different loose concave-convex shapes on the surface of the film, and a certain amount of air can be reserved between layers, so that the function of preventing the layers from being adhered to each other is achieved; meanwhile, the organic silicon microspheres have small particle size, have good compatibility with a polypropylene matrix, are uniformly dispersed in the matrix, and effectively avoid the agglomeration phenomenon easily caused by inorganic fillers. The organic silicon microspheres can be uniformly dispersed in the polypropylene body, and carbon fibers grafted on the organic silicon microspheres can be uniformly dispersed, so that the carbon fibers are distributed on the surface of the film in the length direction, and the film has antistatic performance. Moreover, the organic silicon microspheres and the polypropylene are incompatible, but the surface of the modified organic silicon microspheres is added with carbon fibers, so that the compatibility of the organic silicon microspheres and the polypropylene is improved, and meanwhile, the organic silicon microspheres still have good flowing and slipping performances.

In conclusion, the modified organic silicon microspheres not only have excellent permanent antistatic performance, but also have high dispersibility, low friction coefficient and anti-blocking performance.

The invention also provides a preparation method of the permanent antistatic master batch for preparing the polypropylene film by using the modified organic silicon microspheres, which comprises the following steps:

(1) hydroxylation of carbon fibers: adding concentrated nitric acid with the mass fraction of 10-20%, carrying out oxidation etching on the carbon fiber at the temperature of 40-80 ℃, increasing the polarity and the roughness of the surface of the fiber, cooling to room temperature, washing to be neutral, and drying;

dispersing the oxidized carbon fiber in tetrahydrofuran, adding lithium aluminum hydride or sodium borohydride, stirring, washing and drying to obtain the surface-hydroxylated carbon fiber, wherein the oxygen-containing group on the surface of the carbon fiber is hydroxyl;

(2) surface carboxylation of organic silicon microspheres: dispersing the organic silicon microspheres in N, N-dimethylformamide, adding a silane coupling agent and succinic anhydride to obtain organic silicon microspheres with surface carboxyl functionalized, cleaning and drying to obtain carboxylated organic silicon microspheres; wherein the average grain diameter of the organic silicon microspheres is 2-6 microns;

(3) esterification grafting: dispersing the hydroxylated carbon fibers in the step (1) and the carboxylated organic silicon microspheres in the step (2) in N, N-dimethylformamide, adding dicyclohexylcarbodiimide and 4-dimethylaminopyridine, and performing condensation reflux under magnetic stirring to graft the carbon fibers on the organic silicon microspheres to form an organic silicon microsphere-g-carbon fiber structure;

(4) and (3) drying: filtering, taking out, cleaning and drying the organic silicon microspheres reacted in the step (3) to constant weight to obtain modified organic silicon microspheres;

(5) respectively adding the modified organic silicon microspheres prepared in the step (4) and a dispersing agent into polypropylene, and melting, fully and uniformly mixing to form a uniform dispersion system; and then putting the uniformly mixed materials into a screw extruder, extruding in a molten state, cooling, and pelletizing to obtain the permanent antistatic master batch for polypropylene.

The surface carboxylation principle of the organic silicon microsphere (the silane coupling agent takes KH550 as an example) is as follows:

the permanent antistatic master batch can eliminate static electricity generated by the insulating property of the high polymer by adding the permanent antistatic master batch into the high polymer or the high polymer mixture, and has good effect on dust prevention of the surface of the film.

The invention simultaneously claims the application of the master batch as a permanent antistatic agent in bidirectional polypropylene films, polypropylene cast films and polypropylene blown films. Specifically, the usage amount of the master batch is 5-20 wt% in the production of the polypropylene film.

The permanent antistatic master batch prepared by the invention is added into a polypropylene film, the organic silicon microspheres are incompatible with polypropylene and can migrate to the surface of the film, carbon fibers grafted on the organic silicon microspheres can form an antistatic agent molecular layer with orientation characteristics, the organic silicon microspheres are partially embedded on the surface layer of polypropylene resin, the outward side of the carbon fibers can adsorb moisture in the air to form a very thin conductive layer, the electrostatic charges are effectively dispersed, the attraction of static electricity to dust and particles is reduced, the antistatic effect is achieved, and meanwhile, the internal fibers are interwoven to form a three-dimensional structure, so that the whole polypropylene film has permanent antistatic performance. Meanwhile, as the surface of the organic silicon resin is not completely and deeply embedded in the polypropylene resin, bulges or different loose concave-convex shapes can be formed on the surface of the film, so that the surface of the film becomes rough, and a certain amount of air can be reserved between layers, thereby playing a role in preventing the layers from being adhered to each other.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

1. according to the invention, the organosilicon microspheres and the carbon fibers are respectively modified and grafted to form an organosilicon microsphere-g-carbon fiber structure, the organosilicon microspheres are dissolved in the polypropylene body by utilizing the interfacial properties of the surfaces of the carbon fibers, the organosilicon microspheres keep the flow properties of the organosilicon microspheres, so that the organosilicon microspheres can be firmly embedded in the polypropylene body and are not easy to fall off, and meanwhile, the carbon fibers form a three-dimensional interwoven mesh structure by utilizing the fibers and the fibers, so that the conductivity of the whole film is enhanced, and the film has permanent antistatic property.

2. The master batch with permanent antistatic property is obtained by adding the modified organic silicon microspheres into the polypropylene, compared with the prior art, the master batch has the characteristics of small addition amount, lasting antistatic time and simple preparation method, and the permanent antistatic master batch prepared by the technical scheme of the invention also has the comprehensive properties of good blocking resistance, high dispersity, high gloss, low friction coefficient and the like.

3. According to the invention, the organic silicon microspheres are modified, and the carbon fibers are grafted on the organic silicon microspheres, so that the grafted organic silicon microspheres not only have anti-adhesion performance, but also can migrate to the surface of the film, thereby driving the organic silicon microspheres grafted on the surface of the film to migrate therewith, and enabling the organic silicon microspheres grafted on the surface of the film to be uniformly distributed on the surface of the film in the length direction, thereby enabling the film to have permanent antistatic performance.

4. The permanent antistatic master batch prepared by the invention takes polypropylene as a main body, has good compatibility when preparing a polypropylene film, and has simple preparation method, easy realization and suitability for popularization and application.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the specific contents of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a preparation method of a permanent antistatic master batch for a polypropylene film, which comprises two parts of preparation of a permanent antistatic agent and preparation of the master batch, wherein the preparation of the permanent antistatic agent comprises modified carbon fibers and modified organic silicon microspheres, and the modified carbon fibers are grafted to the organic silicon microspheres to form a carbon fiber-g-organic silicon microsphere structure.

Specifically, the method comprises the following steps:

(1) hydroxylation of carbon fibers: adding concentrated nitric acid with the mass fraction of 10-20%, carrying out oxidation etching on the carbon fiber at the temperature of 40-80 ℃, increasing the polarity and the roughness of the surface of the fiber, cooling to room temperature, washing to be neutral, and drying;

dispersing the oxidized carbon fiber in Tetrahydrofuran (THF), adding lithium aluminum hydride or sodium borohydride, stirring, washing and drying to obtain hydroxylated carbon fiber, wherein the oxygen-containing group on the surface of the carbon fiber is hydroxyl;

(2) surface carboxylation of organic silicon microspheres: dispersing the organic silicon microspheres in N, N-Dimethylformamide (DMF), adding a silane coupling agent and succinic anhydride in an equal molar ratio to obtain organic silicon microspheres with surface carboxyl functionalized, cleaning, and drying to obtain carboxylated organic silicon microspheres with the average particle size of 2-6 microns;

(3) esterification grafting: dispersing the hydroxylated carbon fiber in the step (1) and the carboxylated organic silicon microsphere in the step (2) in DMF, adding Dicyclohexylcarbodiimide (DCC) and 4-Dimethylaminopyridine (DMAP), and condensing and refluxing under magnetic stirring to graft the carbon fiber on the organic silicon microsphere to form an organic silicon microsphere-g-carbon fiber structure;

(4) and (3) drying: filtering the organic silicon microspheres reacted in the step (3), taking out, washing with ethanol for 2-3 times, and drying to constant weight to obtain modified organic silicon microspheres, wherein carbon fibers are distributed on the surfaces of the organic silicon microspheres;

(5) respectively adding the modified organic silicon microspheres prepared in the step (4), the compatilizer and the dispersant into polypropylene, and melting and fully mixing to form a uniform dispersion system; and then putting the uniformly mixed materials into a screw extruder, extruding in a molten state, cooling, and pelletizing to obtain the permanent antistatic master batch for polypropylene.

Wherein the organic silicon microspheres are organic silicon microspheres, and the average particle size is 2-6 microns.

The carbon fiber is polyacrylonitrile carbon fiber, is T700 carbon fiber of Dongli corporation, and has a length of 3-6 mm.

The polypropylene is homopolymerized polypropylene, the melt flow rate is 1-2000 g/10min, the temperature is 230 ℃, and the weight is 2.16 kg.

The silane coupling agent is at least one of KH550, KH5501, KH560, KH570 and KH 580.

The compatilizer is PP graft copolymer, can be at least one of PP-g-MAH, PP-g-MI, PP-g-AA, PP-g-GMA and derivatives of PP graft maleic anhydride, and is added in an amount of 0-10%.

The dispersant is one or more of silane, polypropylene wax, hexenyl bis stearamide and erucamide.

The preparation method of the organic silicon microspheres comprises the following specific steps: adding 100g of vinyl tri (dimethylsiloxane) silane into a reactor, stirring and mixing uniformly, adding 25g of 1,1,3, 3-tetramethyldisiloxane, stirring and mixing for 60min at 50 ℃, adding 1000g of deionized water, 2g of potassium trichlorovinyl platinate (II) and 2g of lecithin acid, and 1g of 1, 4-dibromoacetoxy-2-butene, stirring and mixing at a high speed for 25min, performing ultrasonic dispersion for 10min to form a microemulsion, heating to 50 ℃, and reacting for 180min to complete the reaction; adding 100g of ammonia water, heating to 69 ℃, and continuing to react for 40 min; and after the reaction is finished, carrying out centrifugal sedimentation, filtering and drying to obtain the organic silicon resin microspheres, wherein the average particle size is 2-6 microns.

Other prior arts can also be used to prepare the above-mentioned silicone resin microspheres, for example, a preparation method of copolymerized silicone resin microspheres disclosed in chinese patent CN 111234231 a. Or using the commercial organic silicon resin microspheres.

The present invention will be further described with reference to the following examples.

Example 1

1. Preparation of permanent antistatic Agents

(1) Hydroxylation of carbon fibers: adding 500mL of concentrated nitric acid with the mass fraction of 10-20% into 100g of carbon fiber, carrying out oxidation etching on the carbon fiber at the temperature of 40-80 ℃, refluxing for 40min, cooling to room temperature, washing to be neutral, and drying;

dispersing the oxidized carbon fiber in 1000mL tetrahydrofuran, adding lithium aluminum hydride or sodium borohydride, stirring, washing and drying to obtain the hydroxylated carbon fiber, wherein the oxygen-containing group on the surface of the carbon fiber is hydroxyl.

(2) Surface carboxylation of organic silicon microspheres: dispersing 50g of organic silicon microspheres with the average particle size of 2 microns in 500mLN, N-Dimethylformamide (DMF), adding 66gKH550 and 3g of succinic anhydride to obtain organic silicon microspheres with surface carboxyl functionalized, cleaning and drying to obtain carboxylated organic silicon microspheres;

(3) grafting: dispersing the hydroxylated carbon fibers in the step (1) and the carboxylated organic silicon microspheres in the step (2) in 500mLN, N-Dimethylformamide (DMF), adding 5g of Dicyclohexylcarbodiimide (DCC) and 0.5g of 4-Dimethylaminopyridine (DMAP), condensing and refluxing for 2-12 h under magnetic stirring, and carrying out esterification reaction to distribute the carbon fibers on the surfaces of the organic silicon microspheres to form modified organic silicon resin with an organic silicon microsphere-g-carbon fiber structure;

(4) and (3) drying: and (4) filtering the organic silicon microspheres reacted in the step (3), taking out, washing with ethanol for 2-3 times, and drying to constant weight to obtain modified organic silicon microspheres, namely the permanent antistatic agent.

2. Preparation of the masterbatch

The raw material proportion of the master batch is 10 percent of permanent antistatic agent, 10 percent of dispersing agent and 80 percent of polypropylene.

The permanent antistatic agent is the modified organic silicon microsphere in the step 1-4.

Respectively adding the permanent antistatic agent and the dispersing agent into polypropylene, melting at 200-220 ℃, fully mixing and dispersing to form a uniform dispersion system; and then putting the uniformly mixed materials into a double-screw extruder, extruding in a molten state, cooling, and pelletizing to obtain the permanent antistatic master batch for polypropylene. The temperature of the head of the double-screw extruder is 200-260 ℃, the rotating speed of the double-screw extruder is 210r/min, and the temperature of each zone is 190-240 ℃;

wherein, tetrahydrofuran, DMF and ethanol are analytically pure and are produced by Shanghai Borer chemical reagent factory. Lithium aluminum hydride and sodium borohydride, DCC and DMAP were analytically pure with a purity of 99.98%, which is a chemical reagent factory in Tianjin Fuchen. The carbon fiber is T700 carbon fiber of Tolli corporation, and has a length of 3-6 mm.

Example 2

This example is different from example 1 in that the amount of carbon fibers added in step 1-1 was 200 g.

Example 3

This example is different from example 1 in that the amount of carbon fibers added in step 1-1 was 250 g.

Example 4

This example differs from example 1 in that the average particle size of the silicone microspheres in step 1-2 was 5 μm.

Example 5

This example differs from example 1 in that the added silicone microspheres of step 1-2 have an average particle size of 6 microns.

Example 6

The difference between this example and example 1 is that the raw material ratio in the masterbatch in step 2 is 20% of permanent antistatic agent, 10% of dispersant and 70% of polypropylene.

Example 7

The difference between this example and example 1 is that the raw material ratio in the masterbatch in step 2 is 20% of permanent antistatic agent, 8% of dispersant and 72% of polypropylene.

Example 8

The difference between this example and example 1 is that the raw material ratio in the masterbatch in step 2 is 20% of permanent antistatic agent, 5% of dispersant and 75% of polypropylene.

Example 9

The difference between this example and example 1 is that the raw material ratio in the masterbatch in step 2 is 10% of permanent antistatic agent, 5% of dispersant and 85% of polypropylene.

Example 10

The difference between this example and example 1 is that the raw material ratio in the masterbatch in step 2 is 30% of permanent antistatic agent, 10% of dispersant and 60% of polypropylene.

Example 11

The difference between this example and example 1 is that the raw material ratio in the masterbatch in step 2 is 25% of permanent antistatic agent, 10% of dispersant and 65% of polypropylene.

Example 12

The difference between this example and example 1 is that the raw material ratio in the masterbatch in step 2 is 10% of permanent antistatic agent, 10% of dispersant, 70% of polypropylene and 10% of compatilizer.

The compatilizer is at least one of PP graft copolymer PP-g-MAH, PP-g-MI, PP-g-AA, PP-g-GMA and derivatives of PP graft maleic anhydride.

Example 13

The difference between this example and example 1 is that the raw material ratio in the masterbatch in step 2 is 10% of permanent antistatic agent, 10% of dispersant, 79% of polypropylene and 1% of compatilizer.

The compatilizer is at least one of PP graft copolymer PP-g-MAH, PP-g-MI, PP-g-AA, PP-g-GMA and derivatives of PP graft maleic anhydride.

Example 14

The difference between this example and example 1 is that the raw material ratio in the masterbatch in step 2 is 10% of permanent antistatic agent, 10% of dispersant, 75% of polypropylene and 5% of compatilizer.

The compatilizer is at least one of PP graft copolymer PP-g-MAH, PP-g-MI, PP-g-AA, PP-g-GMA and derivatives of PP graft maleic anhydride.

Comparative example 1

Carbon fiber is used as an antistatic agent, the addition amount of the carbon fiber is 10%, the carbon fiber and 10% of dispersing agent are added into 80% of polypropylene together, and the mixture is melted at 200-220 ℃, fully mixed and dispersed to form a uniform dispersion system; and then putting the uniformly mixed materials into a double-screw extruder, extruding in a molten state, cooling, and pelletizing to obtain the antistatic master batch for polypropylene. The temperature of the head of the double-screw extruder is 200-260 ℃, the rotating speed of the double-screw extruder is 210r/min, and the temperature of each zone is 190-240 ℃.

Comparative example 2

Carbon fiber is used as an antistatic agent, the addition amount of the carbon fiber is 10%, the carbon fiber, 10% of organic silicon microspheres and 10% of dispersing agent are added into 70% of polypropylene together, and the mixture is melted at 200-220 ℃, fully mixed and dispersed to form a uniform dispersion system; and then putting the uniformly mixed materials into a double-screw extruder, extruding in a molten state, cooling, and pelletizing to obtain the antistatic master batch for polypropylene. The temperature of the head of the double-screw extruder is 200-260 ℃, the rotating speed of the double-screw extruder is 210r/min, and the temperature of each zone is 190-240 ℃.

Comparative example 3

This comparative example differs from example 1 in that the added silicone microspheres of step 1-2 have an average particle size of 7 microns.

The master batches prepared in the above examples 1 to 14 and comparative examples 1 to 3 are respectively added into polypropylene to prepare the biaxially oriented polypropylene film, and the formula is as follows:

80wt% of polypropylene (Table plastic 2020S, melt flow rate of 3g/10min, Vicat softening point 150 ℃ C.), and 20wt% of the masterbatch produced in this example or comparative example. The results of the performance measurements are shown in Table 1.

Or 95wt% of polypropylene, and the amount of the master batch produced in this example or comparative example was 5 wt%. The results of the performance measurements are shown in Table 2.

The production process of the biaxially oriented film comprises the following steps:

1) feeding the raw materials into an extruder according to a formula through a feeding device, and heating and melting the raw materials into a viscous state; (ii) a Three melts are filtered and then extruded in a die head, and the temperature of the melts is controlled at 220-230 ℃;

2) cooling the extruded melt by cooling water (16-22 ℃) to form a casting sheet;

3) the casting sheet is longitudinally stretched at first, the preheating temperature is maintained at 125-155 ℃, the stretching temperature is maintained at 80-90 ℃, the stretching ratio is 5.7 times, and the shaping temperature is maintained at 90-95 ℃; then, transverse stretching is carried out, the preheating temperature is maintained at 160-180 ℃, the stretching temperature is maintained at 150-160 ℃, the stretching multiple is 6.5 times, and the setting temperature is maintained at 100-120 ℃;

4) and (3) enabling the film to enter a tractor, maintaining the temperature of a traction roller at 20-40 ℃, flattening and then rolling, and performing performance measurement on the obtained film after aging for one week.

The tensile strength is measured according to the method for measuring the tensile strength in the national standard GB 13022-91 Plastic film tensile property test method.

Young's modulus was measured by tensile method.

The surface resistance is detected by GB/T1410-2006 test method for volume resistivity and surface resistivity of solid insulating material. And (3) carrying out two-time detection on the surface resistance, wherein the detection time is not as follows: the first test is one week after the production of the film, and the second test is three months after the production of the film.

The coefficient of friction (including static coefficient of friction and kinetic coefficient of friction) of the film surface was measured by GBT 10006-2021 "coefficient of friction between Plastic film and sheet" (this standard was carried out at 10.1.2021)

The properties of the biaxially oriented polypropylene film thus obtained are shown in the following table.

As can be seen from the detection results in tables 1 and 2, the addition amount of the master batch prepared by the invention is 5-20 wt%, and compared with the comparative example 1-2, the surface resistance, the friction coefficient, the tensile strength and the Young modulus of the master batch prepared by the invention in examples 1-12 meet the requirements, and the surface of the film has permanent antistatic performance and excellent smoothness, namely, the comprehensive performance of the master batch is better than that of the master batch prepared by singly adding carbon fibers and organic silicon microspheres.

Specifically, in examples 1 to 3, the ratio of carbon fiber to silicone microsphere in the permanent antistatic agent is in the range of 2-5: 1, the surface resistance and the friction coefficient of the film are both significantly better than those of the comparative example, and optimally, the ratio of carbon fiber to silicone microsphere is 4: 1.

example 1 and examples 4-5, except that the average particle size of the added silicone microspheres was different. In the Chinese invention patent CN108084567A, the smoothness of the film is improved by adopting the organic silicon microspheres with the average particle size of 1-4.99 microns, but when the particle size of the organic silicon microspheres is 5 microns, the friction coefficient of the organic silicon microspheres is obviously increased, and the smoothness is reduced. But it was found in the examples of the present invention that it has the opposite effect. Thus, the present inventors carried out control tests (example 5 and control example 3) for an average particle size of 6 μm and 7 μm, respectively, and found that the slip property began to decrease at an average particle size of 6 μm and that the electrical resistance of the film significantly increased at 7 μm. For analysis reasons, with the increase of the particle size, the surface of the organic silicon microsphere can carry more carboxyl groups in the carboxylation process, so more carbon fibers can be grafted after esterification, and the interaction force of the carbon fibers and the flow property of the organic silicon microsphere can reach a balance to ensure that the whole effect is optimal. When the average particle size of the organic silicon microspheres is too large, the flow performance is poor due to self resistance in a polypropylene system, and the dispersion performance is poor and even agglomerated due to interaction among carbon fibers, so that the number of the organic silicon microspheres migrating to the surface of the film is reduced, the carbon fibers are concentrated in the film, the surface resistance is increased, and the friction coefficient is increased.

The test results of examples 5-11 show that the addition ratio of the permanent antistatic agent to the dispersant in the masterbatch is 1-4: 1, wherein the two surface resistance values of examples 6, 7 and 9 are 5.4 × 10³、6.5×10³And 9.3X 10³、8.5×10³. It is apparent that when the addition ratio of the permanent antistatic agent to the dispersant is 2:1 or close to 2:1, the antistatic property is more excellent. Example 7 and example 11 ratios were 2.5:1, example 1 ratio was 1:1, all times.

In examples 12 to 14, all of which are added with a compatibilizer, it is clear that the surface resistance and the friction coefficient thereof are not greatly changed compared with those of example 1, and it can be seen that in the dispersion system of the present invention, the carbon fibers are well compatible with the polypropylene without adding the compatibilizer.

TABLE 1 comparison table of master batch addition ratio of 20wt%

TABLE 2 comparison table of master batch addition ratio of 5wt%

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.