CN114211664A

CN114211664A - Preparation method of toughened thermoplastic plastic

Info

Publication number: CN114211664A
Application number: CN202111345645.5A
Authority: CN
Inventors: 韩辉升; 丁阳; 季捷; 张红梅; 王武光; 华建军
Original assignee: Ji'an Chuangde Precision Electronics Co ltd
Current assignee: Ji'an Chuangde Precision Electronics Co ltd
Priority date: 2021-11-15
Filing date: 2021-11-15
Publication date: 2022-03-22

Abstract

The invention discloses a preparation method of toughened thermoplastic plastics, which belongs to the field of high polymer materials and comprises the steps of coating a photocurable coating on the surface of thermoplastic plastics to be toughened, curing the photocurable coating on the surface of the thermoplastic plastics to be toughened through UV irradiation treatment, and then shearing and mixing through a granulator, an injection molding machine or an extruder to obtain the toughened thermoplastic plastics. In the photocurable oligomers and monomers used in the present invention, at least one of the oligomers or monomers has a polymer glass transition temperature of less than 0 ℃. The toughness or impact strength of the toughened thermoplastic plastic prepared by the invention is obviously improved compared with that of the non-toughened thermoplastic plastic, and the properties such as Vicat softening temperature and the like are not obviously changed.

Description

Preparation method of toughened thermoplastic plastic

Technical Field

The invention belongs to the technical field of high polymer materials, and particularly relates to a toughening modification method of thermoplastic plastics.

Background

Many thermoplastics exhibit brittleness or insufficient impact resistance at service temperatures, thus greatly reducing their use value. The skilled worker has made numerous efforts to reduce the brittleness and to increase the toughness or impact resistance of thermoplastics. The method for improving the toughness of the thermoplastic plastics by blending modification has the advantages of good availability of raw materials, convenience in production, low cost, good toughening effect and the like, thereby receiving wide attention.

The chinese patent No. 00130385.6 entitled "toughened plastic and its preparation method" relates to a mixed rubber component prepared by mixing brittle or less brittle plastics (such as polystyrene, acrylonitrile-styrene resin, polyvinyl acetate, polymethyl methacrylate, polyvinyl chloride, polypropylene or polyoxymethylene) and powdered rubber with a cross-linked structure, and at least one of unvulcanized rubber and thermoplastic elastomer, and the obtained toughened plastic has good toughness and processability, and simultaneously maintains good strength and rigidity.

The Chinese patent with application number of 201310268556.4 relates to a high polymer material refill and a pencil, which uses thermoplastic plastics PFA, PVDF, EPFE, nylon, POM, PC, PBT, ABS and HIPS as base materials, uses a copolymer of styrene and butadiene as a toughening agent and uses graphite and/or carbon black as a filler.

The Chinese patent with the application number of 201410087316.9, namely 'a flexibilizer with chain extension function and application thereof in engineering plastic processing' discloses a flexibilizer with chain extension function for hydroxyl-terminated carboxyl-terminated polycondensates of PET, PBT and the like, which is used for chain extension and toughening of polyester recycled materials. Chinese patent application 201811247076.9 "a rubber toughened plastic and a method for preparing the same" relates to toughening a thermoplastic resin with unvulcanized rubber in the presence of a thermoplastic elastomer and a mixing aid containing a crosslinking agent.

Chinese patent application 201910758354.5 "dendritic polymer, its preparation method and application" relates to a dendritic polymer prepared from hyperbranched polyesteramide, having good lubricating property, good toughening effect and high temperature resistance, and its application as modifier in modification of engineering plastic systems including polyester, polyterephthalamide, polyetherimide, polysulfone, polyethersulfone, polyimide and polyphenylene sulfide.

Chinese patent application 201911264813.0 entitled "high-fluidity toughener and its application in engineering plastics processing" relates to a high-fluidity toughener composed of a core-layer structure and a shell-layer structure and its application in engineering plastics ABS, PC, PBT, ASA and their composites.

Chinese patent application 202010071047.2, "a recycled plastic recycled material, recycled product and recycling method thereof", relates to a recycled plastic recycled material which is prepared by using epoxy vegetable oil and/or modified epoxy vegetable oil as a toughening agent, and maleic anhydride grafted polymer as a compatilizer, and is improved in comprehensive properties in various aspects, and is prepared from one or more of polyethylene, polypropylene, acrylonitrile-butadiene-styrene copolymer, styrene-acrylonitrile copolymer, polycarbonate, polyvinyl chloride, poly (tetramethylene terephthalate) and poly (methyl methacrylate).

Chinese patent application No. 202010617124.X "a plastic pipe for ship and its preparation method" relates to at least one of polyethylene, homo-polypropylene, co-polypropylene and polybutylene toughened by copolymer of ethylene and alpha-olefin.

Chinese patent application 202010339384.5 "an electromagnetic shielding composite material and its preparation method" relates to an electromagnetic shielding composite material using maleic anhydride grafted ethylene-octene copolymer or ethylene-acrylate-maleic anhydride copolymer as toughening agent and using PA11, PA12 or PETG as matrix resin.

Chinese patent application 202010656671.9, plastic toughening agent, reinforced and toughened polypropylene plastic and its preparation method, relates to a toughening agent prepared from dimethyl azodiisobutyrate, acrylonitrile (or acrylamide, acrylic acid), lauryl acrylate (or acrylic acid-2-ethylhexyl), and its application in polypropylene, PET, PBT, PA and PC plastic.

U.S. Pat. No. 4, 5859146 "Impact-resistant thermoplastic molding materials" discloses Impact-resistant thermoplastic molding materials composed of thermoplastics (polyoxymethylene, polyolefin, polyester, polycarbonate, polystyrene, ABS, ASA, SAN, polyamide or polymethacrylate), polyurethanes having a melting point of less than 200 ℃, fibrous or particulate fillers, and conventional additives and processing aids.

U.S. Pat. No. 7041741 "Toughened polymer compositions" relates to the incorporation of thermoplastic elastomers comprising particles of dynamically vulcanized rubber to achieve toughening of thermoplastic polyesters or polyamides.

U.S. Pat. No. 6670419 "Method of grafting thermoplastic polymers and thermoplastic compositions produced by" relates to a process for toughening polyvinyl halides, ABS, styrene-acrylonitrile polymers, styrene-acrylonitrile-acrylate polymers, polyarylene ethers, polyvinyl acetate, polyvinyl methyl ether, chlorinated polyethylene, phenoxy (bisphenol A polyhydroxypropyl ether), polymethyl methacrylate, styrene-maleic anhydride polymers, ethylene-vinyl acetate polymers, polyesters, polyamides, polyoxymethylene, polyurethanes, polyolefins, polycarbonates by comb graft copolymers.

There are not only many patents relating to the toughening of thermoplastics, but also many literature documents such as books and papers relating to the toughening of thermoplastics.

Thus, toughening of thermoplastics is a subject of great concern. The invention provides a novel method for preparing toughened thermoplastic plastics.

Disclosure of Invention

The invention aims to provide a preparation method of toughened thermoplastic plastics, which can improve the toughness or impact strength of the thermoplastic plastics. Incidentally, unless otherwise specified, the parts in the present invention are parts by weight, percentages are percentages by weight, and proportions are percentages by weight.

The method comprises the following steps:

step 1, preparing a photocurable coating:

the photocurable coating is prepared by mixing and uniformly stirring a photocurable oligomer, a photocurable monomer, a photoinitiator and raw materials which need to be added according to the requirements of process, performance or cost, such as an auxiliary initiator, a solvent, a diluent, a plasticizer, a pigment, a color paste, a filler, an antifoaming agent, a leveling agent, a coupling agent, a wetting dispersant and the like.

For example, 100 parts of photocurable oligomer, 0.5-10 parts of photoinitiator, 0-100 parts of photocurable monomer, 0-10 parts of co-initiator, 0-100 parts of solvent, 0-100 parts of diluent, 0-50 parts of plasticizer, 0-5 parts of pigment, 0-5 parts of color paste, 0-50 parts of filler, 0-2.5 parts of defoaming agent, 0-2.5 parts of leveling agent, 0-2.5 parts of coupling agent and 0-2.5 parts of wetting dispersant are mixed and stirred uniformly to prepare the photocurable coating.

The photocurable coating is in a transparent or semitransparent liquid state, paste state or paste state and has flowability. The photocureable coating contains at least one photocureable oligomer or monomer with the glass transition temperature lower than 0 ℃; the average functionality of the photocurable oligomer and the photocurable monomer constituting the photocurable coating is greater than 1.0. The purpose of the average functionality of greater than 1.0 is to render the photocurable coating three-dimensional network upon photocuring.

In the present invention, the functionality refers to the number of functional groups participating in a photocuring reaction (including photocuring polymerization and photocuring crosslinking) in an oligomer or monomer. More specifically, functionality refers to the number of carbon-carbon double bond functional groups in the oligomer or monomer that participate in the photocuring reaction (including photocuring polymerization and photocuring crosslinking).

Step 2, coating:

coating 100 parts of thermoplastic to be toughened with 2.5-50 parts of the photocurable coating obtained in the step 1, so that the surface or part of the surface of the thermoplastic to be toughened is coated with a coating layer with the average thickness of not more than 1 mm; the thermoplastic to be toughened is thermoplastic granules with the weight of each granule not more than 2g, thermoplastic sheets with the thickness not more than 5mm, thermoplastic wires with the diameter not more than 6mm, thermoplastic strips with the thickness not more than 5mm, and thermoplastic nozzle materials or reclaimed materials; the coating mode of the granules is spraying, dipping, curtain coating and brush coating; the coating mode of the sheet or the strip is coating by a drawing coating, a roller coating, a dip coating, a knife coating, a spray coating, a curtain coating or a screen printing method; or, putting the photo-curable coating obtained in the step 1 and the thermoplastic to be toughened together and uniformly stirring the mixture to ensure that the photo-curable coating is adhered to the surface of the thermoplastic to be toughened;

the thermoplastic to be toughened may be crushed or comminuted using a crusher or comminutor either before or after being coated with the photocurable coating. For nozzle or reclaimed materials of different sizes and shapes, it is preferable to crush or pulverize them before coating.

Step 3, photocuring:

irradiating the coated thermoplastic plastic obtained in the step 2 with ultraviolet rays to partially or completely cure the coating material coated on the surface of the thermoplastic plastic; the coated thermoplastic is continuously or intermittently flipped, twisted, agitated, vibrated, rotated or blown while or during irradiating the coated thermoplastic with one or more directional sources of ultraviolet light; after the curing is finished, or drying is carried out at 50-120 ℃ to remove or partially remove low molecular organic matters in the coating, including solvents, diluents, unpolymerized monomers, photoinitiators and low molecular compounds after the decomposition of the photoinitiators, and also remove moisture in the thermoplastic and the coating.

Upon photocuring, the photocurable coating becomes a photocurable coating, and more precisely, the photocurable coating becomes a crosslinked photocurable coating.

Step 4, shearing and mixing:

and (3) cutting, chopping, grinding, shredding or crushing the material obtained in the step (3) or the agglomerated material obtained in the step (3), uniformly mixing by using a screw granulator, and preparing into granules, or shearing and mixing by using an open mill or an internal mixer, and then crushing, crushing or preparing into granules by using the screw granulator to obtain the toughened thermoplastic plastic with the photocureable coating distributed in a continuous phase in a dispersion phase. The toughened thermoplastic still maintains the flowability of the thermoplastic.

Step 5, forming:

and (4) carrying out compression molding, injection molding, extrusion molding or calendaring molding on the granules obtained in the step (4) to prepare the toughened thermoplastic plastic product.

Many rigid thermoplastics have inadequate toughness or impact strength for various applications. Thermoplastics such as polyvinyl chloride, chlorinated polyvinyl chloride, polymethyl methacrylate, polyamides, polycarbonates, polyesters, acrylics, acrylonitrile-styrene-butadiene polymers, acrylonitrile-styrene polymers, polyurethanes, polyoxymethylene, polyphenylene oxide, polysulfone, polyethersulfone, polyphenylene sulfide, and the like may be toughened using the disclosed methods. Polymer alloys of these plastics, thermoplastics containing glass beads, glass or carbon fibres, flame retardants, antistatic agents, UV-protection agents, antibacterial agents or conductive fillers, can also be toughened in this way. The thermoplastic to be toughened is transparent, translucent or opaque and may also be coloured, including black.

The photocurable coating consists of a photocurable oligomer and a photoinitiator, consists of a photocurable oligomer, a photocurable monomer and a photoinitiator, or consists of the photocurable oligomer, the photocurable monomer, the photoinitiator and one or more selected from a coinitiator, a solvent, a plasticizer, a diluent, a pigment, a color paste, a filler, an antifoaming agent, a leveling agent, a coupling agent and a wetting dispersant. That is, the photocurable coating must comprise at least two materials: the light-curable oligomer and the photoinitiator.

The light-curable oligomer is one or more of light-curable pure acrylate polymer, polyurethane acrylate, polyurethane methacrylate, unsaturated polyester, epoxy acrylate, epoxy methacrylate, polyester acrylate, polyether acrylate, organic silicon acrylate polymer, epoxy resin and water-based light-curable oligomer, or a mixture of the oligomer and solvent, diluent or light-curable monomer. Photocurable oligomers may also be referred to as photocurable oligomers. The photocurable oligomer having a high viscosity can be diluted with a monomer, a solvent or the like in preparing a coating.

The photocurable monomer is a monofunctional, difunctional, trifunctional, or higher functional monomer, or a mixture of such monomers. The functional group herein is a carbon-carbon double bond which can participate in radical polymerization, or a functional group including a carbon-carbon double bond, such as vinyl, allyl, propenyl, etc.

The photo-curable coating at least contains a photo-curable oligomer with double functional groups, three functional groups or multiple functional groups, or at least contains a photo-curable monomer with double functional groups, three functional groups or multiple functional groups, so that the photo-curable coating forms a three-dimensional network structure after photo-curing.

At present, many companies at home and abroad produce photocurable oligomers and monomers, and the photocurable oligomers and monomers have various types and are sufficiently supplied, so that the photocurable coating which can be used for toughening various thermoplastics can be prepared according to the existing photocurable oligomers and monomers.

The photoinitiator is a class I or class II photoinitiator; the I, II type photoinitiator is selected from one or the combination of more than two of benzophenone, 1-hydroxy-cyclohexyl-phenyl ketone, benzoin dimethyl ether, 2-hydroxy-2-methyl-1-phenyl-1-acetone, 2, 4, 6-trimethylbenzoyl-diphenyl phosphine oxide and isopropyl thioxanthone; the photoinitiator is a single photoinitiator or a combination of two or more photoinitiators. For example, a photoinitiator that is susceptible to causing a superficial layer to cure and a photoinitiator that is susceptible to causing a deep layer to cure may be added simultaneously to the photocurable coating.

The coinitiator is one or more of compounds prepared by Michael addition reaction of triethylamine, diethanolamine, triethanolamine, N-methylethanolamine, N-dimethylethanolamine, N-diethylethanolamine, ethyl 4-dimethylaminobenzoate, diethylamine or diethanolamine and difunctional acrylate or polyfunctional acrylate;

the solvent is alcohols, esters, ketones, aromatic hydrocarbons, alcohol ethers, ether ester solvents with the boiling point lower than 200 ℃, dimethyl sulfoxide, N-dimethylformamide, dimethyl carbonate, nitromethane, nitroethane, 1-nitropropane and water;

the plasticizer is phthalate, phosphate, polyalcohol and dibasic fatty acid ester compounds with the boiling point higher than 280 ℃ under normal pressure;

the diluent is a liquid mixture containing the solvent, the plasticizer or the monomer.

In addition to the above-mentioned substances, a thermoplastic resin or a polymer compatibilizer may be contained in the photocurable coating. The thermoplastic resin and the polymeric compatibilizer may be dissolved in the photocurable coating. The photocurable coating may contain 0.5-10% of a thermoplastic resin and/or 0.2-5% of a polymeric compatibilizer; polymeric compatibilizers used include, but are not limited to, maleic anhydride, acrylic or glycidyl methacrylate grafted polyolefins or polyolefin elastomers, block copolymers of polysiloxanes and polycarbonates, styrene-maleic anhydride copolymers, and styrene-acrylonitrile-glycidyl methacrylate copolymers.

The photocureable coating is formed by ultraviolet light curing of the photocureable coating adhered to the surface of the polycarbonate material. The photocurable coating is in a liquid or paste flowable state to facilitate adhesion to the surface of the thermoplastic to be toughened. The viscosity of the photocurable coating can be between 100-. Depending on the viscosity, the photocurable coating can be applied to the surface of the thermoplastic by various methods, such as spraying, draw-coating, and the like.

The photocuring reaction (simply referred to as "photocuring") in the present invention is basically an ultraviolet curing reaction. The light source used for photocuring may be a mercury lamp, an electrodeless lamp, a metal halide lamp or an LED lamp that can generate ultraviolet light. The uv light from the light source causes the photoinitiator used to generate free radicals, which initiate the polymerization and crosslinking of the oligomers and monomers.

After the photocurable coating is solidified, the photocurable coating and the thermoplastic are subjected to shearing mixing and granulation, and a screw granulator can be used. The screw granulator may be a single screw, twin screw and triple screw granulator. Of course, it is also possible to use an open mill or internal mixer for shearing and mixing and then to use a screw granulator for granulation, thus obtaining granules of toughened thermoplastic plastics.

The screw pelletizer used for the shear mixing may be a twin-screw pelletizer having a kneading section with a shear block or a kneading block. The presence of the shear blocks or kneading blocks is intended to enhance the shearing action and thus to make the distribution of the photocurable coating more uniform in the matrix of the thermoplastic.

In addition to toughening new thermoplastic materials by the disclosed method, toughening can also be applied to recycled or virgin thermoplastic materials by the disclosed method. The nozzle or regrind may be broken up into particles having an average weight of no more than 2g by a plastic breaker prior to application of the photocurable coating.

The thermoplastic to be toughened may also be pellets obtained by the processes described above or articles made from the pellets obtained or crushed materials of the articles obtained. That is, toughening of thermoplastics allows for recycling of the process.

The invention can provide a preparation method of toughened thermoplastic plastics, which effectively overcomes the defect of impact resistance of the thermoplastic plastics by shearing and mixing the photocuring coating and the thermoplastic plastics, improves the toughness of the thermoplastic plastics, and basically keeps other mechanical properties and heat resistance of the thermoplastic plastics unchanged.

In addition, many manufacturers of oligomers and monomers for photocurable coatings at home and abroad are available, raw materials such as various oligomers, monomers, photoinitiators and the like are sufficiently supplied, manufacturers for producing equipment such as photocuring machines and the like are also available, and a person skilled in the art can easily select the raw materials for toughening and modifying the photocurable coatings so as to meet various requirements on the performance of thermoplastics. Therefore, the method has good application prospect.

Drawings

FIG. 1 shows the results of ball drop tests on the respective materials.

Detailed Description

In order to make the technical solutions of the present invention more clear and obvious to those skilled in the art, the following examples are given for illustration. It should be noted that the following examples are not intended to limit the scope of the claimed invention.

In the examples, tests were carried out in accordance with ISO standards, except that the falling ball impact test was carried out in accordance with the Enterprise standards. Determining the density of the material according to ISO 1183-1; testing the melt mass flow rate of the material according to ISO 1133, wherein the testing condition is 300 ℃/1.2 kg; testing the tensile strength and the elongation at break of the material according to ISO 527-1, wherein the tensile rate is 50 mm/min; testing the notch impact strength of the material according to ISO180 standard, and preparing a V-shaped notch with the notch depth of 2mm by using a notch sampling machine; the Vicat softening temperature of the material was tested according to ISO 306/B50.

Example 1

Photocurable coatings are prepared from photocurable oligomers, monomers, and photoinitiators. The oligomer used was a urethane acrylate diluted with isobornyl acrylate having a glass transition temperature (Tg) of-33 ℃ manufactured by Sartomer Saddoman under the trade name CN966J75NS, isobornyl acrylate also being a product of Sartomer Saddoman, USA under the trade name SR506 NS. The monomer used was tetrahydrofuran acrylate (THFA) manufactured by Taiwan Happy materials industries, Inc. under the trade name EM 214. The photoinitiator used was 2-hydroxy-2-methyl-1-phenyl-1-propanone, a product of Ciba under the trade name Darocur 1173 (1173 for short).

The thermoplastic to be toughened is polyamide PA66 containing 30% of glass beads and 10% of glass fibers, black pellets, product of French AD MAJORIS, under the trademark PA66 GB30+ GF10-VENYL UWGB407H-7727 (in this example abbreviated to PA 7727).

The above-mentioned photocurable oligomer and monomer are mixed in a weight ratio of 4:1, and the addition amount of the photoinitiator 1173, 1173 is 5% of the total weight of the photocurable oligomer and monomer. Stirring was carried out to obtain a photocurable coating material, abbreviated as "C41" in this example.

Formulation ZRGX-PA-052901 is a single PA7727, new stock. Of the formulations ZRGX-PA-052902, ZRGX-PA-052903 and ZRGX-PA-052904, PA7727 and C41Mixing C41 and PA7727 at a ratio of 100:10, 100:4 and 100:4, respectively, stirring, allowing C41 to coat on the surface of PA7727 particles, allowing the PA7727 particles coated with photocurable coating C41 to pass through a medium pressure mercury lamp equipped with a light intensity of 1000mW/cm at a speed of 2cm/s ²4 times, while turning the particles so that the C41 on the surface of the PA7727 particles was fully cured.

The pellets of the above materials (PA7727 virgin material and PA7727 having a photocurable coating on the surface) were pelletized by a single-screw pelletizer. The single-screw granulator has a screw diameter of 25mm and a length-diameter ratio of 25: 1. The speed of rotation was 200rpm and the barrel and head temperature was 310 ℃.

After the pellets of the formulations ZRGX-PA-052901, ZRGX-PA-052902 and ZRGX-PA-052903 were passed through the single-screw pelletizer once or twice, 5g of each of the extruded materials was taken from the head nozzle of the pelletizer and was hot-pressed into a sheet of 1.0mm in 2 seconds after extrusion, and after standing at room temperature for 2 hours, the sheets obtained from the four formulations were subjected to a falling ball impact test at room temperature, wherein the falling balls were solid steel balls having a chromium plating layer on the surface, the weight was 500g, and the height was 150 cm. The state of the sheets (respectively designated as 1, 2, 3 and 4) of the above four formulations after the ball drop test is shown in fig. 1.

Sheets (5, 6, 7, 8, respectively) made from the four formulations of extrudate were left at room temperature for 72 hours and tested under the same ball drop impact test conditions, the state after the ball drop test being shown in fig. 1.

The result of ball drop test shows that the new PA66 material has poor impact resistance, the prepared sheet is impacted by ball drop and is split into four lobes, and the new PA66 material is modified by our method, so that the impact resistance is obviously improved. When 4 parts of the photocurable coating used was added per 100 parts of the new PA66, the resulting sheet was broken into two lobes by ball impact, whereas when 10 parts of the photocurable coating used was added, the sheet was not broken into two or more lobes by ball impact, showing good impact resistance.

The falling ball impact test is carried out after the sheet is made and is placed for 2h or 72h, and the result of the sample shows that the placing time has little influence on the result of the falling ball impact test, and the result is shown in figure 1.

Example 2

A photocurable coating is prepared according to the following formula: 35 parts of polyester acrylate, 55 parts of acrylic acid-2-ethyl hexyl (2-EHA) (Tg of-70 ℃), 3 parts of 1, 6-hexanediol diacrylate (HDDA), 3 parts of a photoinitiator 1173 and 2 parts of a photoinitiator 369. The components are mixed evenly and stored away from light for standby.

The polyester acrylate (curable oligomer) used in this example was produced by chemical ltd, dengtai, under the trade name CT-UV400, and has a functional group number of 2, and it has characteristics of moderate curing speed, moderate flexibility, and good adhesion to polyethylene terephthalate (PET), oriented polypropylene (OPP), polyvinyl chloride (PVC), glass, and other substrates. 2-EHA and HDDA are products of Sartomer corporation, USA.

The prepared photo-curable coating is coated on the surface of a certain weight of recycled transparent hard PVC film with the thickness of 0.15mm by blade coating. The thickness throughout the coating is no more than 0.05 mm. Then, the photocurable coating on the surface of the film was cured into a coating film by passing the film through a photocuring machine (100W/cm) equipped with a high-pressure mercury lamp at a speed of 2.5 cm/s. The recycled rigid PVC film with UV coating thus gained 8.0% weight.

The PVC film with the coating film is rolled into small strips and fed into a double-screw granulator to obtain modified PVC granules. The diameter of a screw of the double-screw granulator is 50.5mm, the length-diameter ratio is 32, the rotating speed of the screw is 225rpm during granulation, the temperature of a charging barrel of a charging section is 170 ℃, and the temperature from the charging barrel of a melting section to a machine head is 185 ℃.

For comparison, virgin (i.e., uncoated) recycled rigid PVC film was fed to a twin-screw pelletizer to obtain an "unmodified PVC pellet" under the same pelletizing process conditions.

The above two pellets were prepared into test specimens by the same injection molding process.

For further comparison, we prepared a "common modified PVC pellet" using the following process: the coating is firstly coated on a film of a recycled hard PVC film in the same proportion (the proportion of the photo-curable coating and the recycled hard PVC film), the film is twisted into small strips, the small strips are fed into a double-screw granulator and granulated to obtain a common modified PVC granular material, then the granular material is prepared into a sample through an injection molding process, and the sample is passed through a photo-curing machine once, twice or four times to cure the photo-curable coating mixed in the sample.

The samples were left in the laboratory for 24 hours, and then the physical properties of each sample were measured at room temperature. The laboratory temperature is 21-25 deg.C and relative humidity is 45-55%.

The results obtained are shown in Table 1. The test results of the samples obtained by passing the samples prepared from the "ordinary modified PVC pellets" through the photo-curing machine once or twice are not shown because the Vicat softening temperature and the notched impact strength are slightly lower than those of the samples obtained by passing the samples through the photo-curing machine four times.

TABLE 1 Properties of modified and unmodified PVC pellets

As can be seen from the table, the impact resistance of the "modified PVC pellets" obtained by the method disclosed by the invention is greatly improved, and the impact resistance and tensile strength are also much better than those of the "ordinary modified PVC pellets".

Example 3

The materials, formulation, preparation and testing used in this example were the same as in example 2, except that an open mill having a roll diameter of 160mm and a two roll speed ratio of 1.2:1 was used for shear mixing. The roll temperature during mixing is 180 +/-3 ℃, the rotating speed of a front roll is about 8rpm, the mixing time of each material is about 7.5min, 4 thin passes are included, and the roll gap during thin passes is about 0.5 mm. After mixing uniformly, the sheet was taken out, and then each test sample was prepared by a flat vulcanizing machine.

The method comprises the steps of preparing an unmodified PVC sample from a recovered hard PVC film without the photo-curable coating, mixing the recovered hard PVC film coated with the photo-curable coating after a photo-curing process to prepare a modified PVC sample, and performing photo-curing on the recovered hard PVC film coated with the photo-curable coating after a mixing process to prepare a common modified PVC sample.

The notched impact strengths of the "unmodified PVC" sample, the "modified PVC" sample and the "ordinary modified PVC" sample in this example were 3.8kJ/cm, respectively²、33.6kJ/cm²And 13.7kJ/cm²The test result shows that the photocurable coating coated on the recovered hard PVC film is firstly cured and then sheared and mixed, the obtained material has the best impact resistance, and the notch impact strength of the material is far higher than that of an unmodified PVC sample and a common modified PVC sample.

The test results of this example, in combination with the test results of example 2, also show that different shear mixing processes, such as a shear mixing process using a twin-screw granulator or a shear mixing process using an open mill, have little effect on the impact resistance of the resulting blend of PVC and photocurable coating.

Example 4

The photocurable coating formulation used in example 4 was prepared by adding 25 parts of ethyl acetate to the photocurable coating formulation of example 2 to reduce the viscosity of the photocurable coating.

Spraying the obtained coating on the surface of a recovered hard PVC film, drying the coating, increasing the weight of the recovered hard PVC film by 8%, carrying out photocuring by using the process conditions of example 2, and granulating by using a double-screw granulator to obtain the PVC modified granules with the notch impact strength of 35.8kJ/m²Slightly higher notched impact strength than the "modified PVC pellets" obtained in example 2.

Example 5

Formulation of photocurable coating CC1 used in this example: 50 parts of polyester acrylate (CT-UV400, chemical industry of Jinan Changtai), 15 parts of tetrahydrofuran acrylate (THFA), 25 parts of 2-ethylhexyl acrylate (2-EHA), 2 parts of 1, 6-hexanediol diacrylate (HDDA), 3 parts of ethylene-methyl acrylate copolymer (EMA, the content of methyl acrylate is 8-40%, products of DuPont company in the United states), 3 parts of photoinitiator TPO and 2 parts of photoinitiator 369. Dissolving EMA in a mixed solution of THFA and HDDA, uniformly mixing all the components, and storing in dark for later use.

The photocurable coating formulation CC2 used was the same as the photocurable coating formulation CC1, except that EMA was not included in formulation CC 2.

The two photo-curable coatings are respectively coated on the surface of a polycarbonate pellet in a mixing and stirring manner, and the ratio of the polycarbonate to the photo-curable coatings is 100: 5. The pellet is available under the brand name PC02-10, wherein the maximum weight of each pellet is no more than 0.20g, and is produced by Ningbo Zhejiang iron galenical chemical Co.

A mixture of polycarbonate and photocurable coating was prepared in two processes: process I is a process as claimed in claim 1, wherein the photocurable coating composition applied to the surface of the polycarbonate pellets is photocured under the photocuring conditions of example 1, and then the resultant mixture is subjected to shear mixing and pelletization by means of a twin-screw pelletizer. Process II is carried out by granulating polycarbonate granules coated with a photocurable coating on the surface by means of a twin-screw granulator, and then subjecting the granules obtained to photocuring or light irradiation under the photocuring conditions as in example 1.

The twin-screw granulator used had a diameter of 35.6mm and a length to diameter ratio of 40 for each screw. The temperature of the feeding section of the double-screw granulator is 215 +/-3 ℃, the temperature of the melting section is 275 +/-3 ℃, the temperature of the homogenizing section is 260 +/-3 ℃, the temperature of a machine head is 240 +/-3 ℃, the rotating speed of a screw is 300rpm, the material is water-cooled and granulated after coming out of the double-screw granulator, and is dried in a 120 ℃ oven for 4 hours after being kept stand for 24 hours, and then the injection molding process is carried out to prepare a test sample; the injection temperature is 270-290 ℃, and the setting temperature of the mold temperature machine is 100-120 ℃. After the injection molding is finished, the test specimens are placed in a greenhouse for 24 hours and then subjected to various tests.

The effect of different photocurable coatings (formulations CC1 and CC2) and different blend preparation processes (process I and process II) on the blend properties is shown in table 2.

TABLE 2 Effect of the preparation of Photocurable coatings and blends thereof

As can be seen from Table 2, the photocurable coating CC1 contained a small amount of EMA, and both the tensile strength and notched Izod impact strength of the resulting blend were increased using either Process I or Process II. The notched impact strength of the blend prepared by Process I is significantly higher than that of the blend prepared by Process II.

Example 6

The photocurable oligomers and monomers used in this example were products from Sartomer company.

Photocurable coating formulation CC 30: 50 parts of urethane acrylate (CN965, functionality 2, Tg-37 ℃), 40 parts of caprolactone acrylate (SR495B, functionality 1, Tg-53 ℃), 2 parts of (3) ethoxylated trimethylolpropane triacrylate (SR454, functionality 3, Tg-40 ℃), 3 parts of pentaerythritol triacrylate (SR444, functionality 3, Tg 103 ℃), 3 parts of photoinitiator TPO, 2 parts of photoinitiator 369.

Formulation CC31 of photocurable coating as comparative example: 50 parts of urethane acrylate (CN968, functionality 6, Tg 145 ℃), 40 parts of isobornyl acrylate (functionality 88 ℃, Tg), 2 parts of 1, 6-hexanediol diacrylate (SR238, functionality 2, Tg 43 ℃), 3 parts of pentaerythritol triacrylate (SR444, functionality 3, Tg 103 ℃), 3 parts of photoinitiator TPO, 2 parts of photoinitiator 369.

Formulation CC32 of photocurable coating as comparative example: 50 parts of an epoxy acrylate oligomer (CN104, functionality 2, Tg 145 ℃), 40 parts of isobornyl methacrylate (SR423, functionality 1, Tg 110 ℃), 2 parts of dipropylene glycol diacrylate (SR508, functionality 2, Tg 40 ℃), 3 parts of trimethylolpropane triacrylate (SR351, functionality 3, Tg 62 ℃), 3 parts of photoinitiator TPO, 2 parts of photoinitiator 369.

The above photocurable coatings were respectively applied to the surface of a polycarbonate pellet (brand PC02-10, referred to as virgin stock) by mixing and stirring. The ratio of polycarbonate to photocurable coating was 100: 5. Using Process I as described in example 5, blends of polycarbonates were prepared.

The physical properties of the virgin materials and the respective blends were also tested, and the results are shown in Table 3.

TABLE 3 Effect of the formulation of the Photocurable coating on the Properties of the blends

Is a new polycarbonate material and does not contain a photo-curable coating.

As can be seen from Table 3, photocurable coating CC30 contains oligomers or monomers with a lower Tg (with a Tg much lower than room temperature), blends made from polycarbonate and CC30 have an optimum notched Izod strength much higher than polycarbonate virgin material, while photocurable coatings CC31 and CC32 have both oligomers and monomers with a Tg higher than room temperature, and blends made from polycarbonate and photocurable coating CC31 or CC32 have notched Izod strength even lower than polycarbonate virgin material. Therefore, the selection of oligomers and monomers with Tg much lower than room temperature to formulate photocurable coatings is important to achieve good impact resistance.

The embodiments described above are intended to facilitate one of ordinary skill in the art in understanding and using the present invention. It will be readily apparent to those skilled in the art that various modifications can be readily made to the embodiments, for example, photo-curing and electron beam curing are both radiation curing methods, electron beam curable coatings are used in place of photo-curable coatings, and electron beam curing machines are used in place of photo-curing machines, and similar toughening effects are contemplated by and are within the scope of the invention, and that such modifications and improvements are intended to be within the scope of the invention or are not intended to be limiting.

Claims

1. A method for preparing toughened thermoplastic plastics is characterized by comprising the following steps:

step 1, preparing a photocurable coating: mixing the light-curable oligomer, the light-curable monomer and the photoinitiator, and uniformly stirring to obtain the light-curable coating; the photocurable coating is transparent or semitransparent liquid, paste or paste; the photocureable coating contains at least one photocureable oligomer or monomer with the glass transition temperature lower than 0 ℃; the average functionality of the photocurable oligomer and the photocurable monomer constituting the photocurable coating is greater than 1.0;

step 2, coating: coating 2.5-50 parts by weight of the photocurable coating obtained in the step 1 on 100 parts by weight of the thermoplastic to be toughened, so that the surface or part of the surface of the thermoplastic to be toughened is coated with a coating layer with the average thickness of not more than 1 mm; the thermoplastic to be toughened is thermoplastic granules with the weight of each granule not more than 2g, thermoplastic sheets with the thickness not more than 5mm, thermoplastic wires with the diameter not more than 6mm, thermoplastic strips with the thickness not more than 5mm, and thermoplastic nozzle materials or reclaimed materials; the coating mode of the granules is spraying, dipping, curtain coating and brush coating; the coating mode of the sheet or the strip is coating by a drawing coating, a roller coating, a dip coating, a knife coating, a spray coating, a curtain coating or a screen printing method; or, putting the photo-curable coating obtained in the step 1 and the thermoplastic to be toughened together and uniformly stirring the mixture to ensure that the photo-curable coating is adhered to the surface of the thermoplastic to be toughened; or, before or after coating the thermoplastic to be toughened with the photo-curable coating, crushing or pulverizing the thermoplastic by a crusher or a pulverizer;

step 3, photocuring: irradiating the coated thermoplastic plastic obtained in the step 2 with ultraviolet rays to partially or completely cure the coating material coated on the surface of the thermoplastic plastic; the coated thermoplastic is continuously or intermittently flipped, twisted, agitated, vibrated, rotated or blown while or during irradiating the coated thermoplastic with one or more directional sources of ultraviolet light; after the curing is finished, or drying is carried out at 50-120 ℃ to remove or partially remove low molecular organic matters in the coating, including solvents, diluents, unpolymerized monomers, photoinitiators and low molecular compounds decomposed by the photoinitiators, and remove moisture in the thermoplastic plastics and the coating;

step 4, shearing and mixing: cutting, chopping, grinding, shredding or crushing the material obtained in the step 3 or the agglomerated material obtained in the step 3 by a crusher, uniformly mixing by using a screw granulator, and preparing into granules, or cutting and mixing by using an open mill or an internal mixer, and then crushing, crushing or preparing into granules by using the screw granulator to obtain the toughened thermoplastic plastic with the photocuring coating distributed in a continuous phase in a dispersion phase;

step 5, forming: and (4) carrying out compression molding, injection molding, extrusion molding or calendaring molding on the granules obtained in the step (4) to prepare the toughened thermoplastic plastic product.

2. The process for preparing a toughened thermoplastic according to claim 1, wherein: the thermoplastic plastic is selected from one of polyvinyl chloride, chlorinated polyvinyl chloride, polymethyl methacrylate, polyamide, polycarbonate, polyester, acrylic plastic, acrylonitrile-styrene-butadiene polymer, acrylonitrile-styrene polymer, polyurethane, polyformaldehyde, polyphenyl ether, polysulfone, polyether sulfone and polyphenylene sulfide; the thermoplastic is transparent, semitransparent or opaque thermoplastic with single component or polymer alloy containing the thermoplastic, thermoplastic containing glass beads, glass fibers or carbon fibers, or thermoplastic containing flame retardant, antistatic agent, ultraviolet resistant agent, antibacterial agent or conductive filler.

3. The process for preparing a toughened thermoplastic according to claim 1, wherein: the photo-curable coating consists of a photo-curable oligomer and a photoinitiator, consists of a photo-curable oligomer, a photo-curable monomer and a photoinitiator, or consists of the photo-curable oligomer, the photo-curable monomer, the photoinitiator and one or more selected from co-initiators, solvents, plasticizers, diluents, pigments, color pastes, fillers, defoaming agents, flatting agents, coupling agents and wetting and dispersing agents;

the photocurable coating comprises, by weight, 100 parts of photocurable oligomer, 0.5-10 parts of photoinitiator, 0-100 parts of photocurable monomer, 0-10 parts of co-initiator, 0-100 parts of solvent, 0-100 parts of diluent, 0-50 parts of plasticizer, 0-5 parts of pigment, 0-5 parts of color paste, 0-50 parts of filler, 0-2.5 parts of defoaming agent, 0-2.5 parts of flatting agent, 0-2.5 parts of coupling agent and 0-2.5 parts of wetting dispersant;

the photocurable oligomer is one or more of photocurable pure acrylate polymer, polyurethane acrylate, polyurethane methacrylate, unsaturated polyester, epoxy acrylate, epoxy methacrylate, polyester acrylate, polyether acrylate, organic silicon acrylate polymer, epoxy resin and aqueous photocurable oligomer, or a mixture of the oligomers and a solvent, a diluent or a photocurable monomer;

the photocurable monomer is a monofunctional, difunctional, trifunctional or higher functional monomer, or a mixture of these monomers;

the photo-curable coating at least contains one type of bi-functional group, tri-functional group or multi-functional group photo-curable oligomer or at least contains one type of bi-functional group, tri-functional group or multi-functional group photo-curable monomer;

the photoinitiator is a class I or class II photoinitiator; the I, II type photoinitiator is selected from one or the combination of more than two of benzophenone, 1-hydroxy-cyclohexyl-phenyl ketone, benzoin dimethyl ether, 2-hydroxy-2-methyl-1-phenyl-1-acetone, 2, 4, 6-trimethylbenzoyl-diphenyl phosphine oxide and isopropyl thioxanthone; the photoinitiator is a single photoinitiator or a combination of two or more photoinitiators.

4. The process for preparing a toughened thermoplastic according to claim 1, wherein: the photocurable coating contains 0.5-10 wt% of a thermoplastic resin and/or 0.2-5 wt% of a polymeric compatibilizer; the polymeric compatibilizer includes maleic anhydride, acrylic or glycidyl methacrylate grafted polyolefin or polyolefin elastomer, block copolymers of polysiloxane and polycarbonate, styrene-maleic anhydride copolymers, and styrene-acrylonitrile-glycidyl methacrylate copolymers.

5. The process for preparing a toughened thermoplastic according to claim 1, wherein: the viscosity of the photocurable coating prepared in step 1 measured at 25 ℃ with a rotational viscometer was 100-200000 Pa-s.

6. The process for preparing a toughened thermoplastic according to claim 1, wherein: the light source used for photocuring in step 3 is a mercury lamp, an electrodeless lamp, a metal halide lamp or an LED lamp.

7. The method of making a toughened thermoplastic article according to claim 1, wherein: the screw pelletizer used for shear mixing in step 4 is a single screw, twin screw or triple screw pelletizer.

8. The process for preparing a toughened thermoplastic according to claim 1, wherein: the screw pelletizer used for shearing and mixing in the step 4 is a double screw pelletizer or a three screw pelletizer with mixing sections having shear blocks.

9. The process for preparing a toughened thermoplastic according to claim 1, wherein: the thermoplastic to be toughened is a nozzle material or a reclaimed material of the thermoplastic; the nozzle or regrind is crushed by a plastic crusher into particles having an average weight of not more than 2.5g before being coated with the photocurable coating.

10. The process for preparing a toughened thermoplastic according to claim 1, wherein: the thermoplastic to be toughened is the granules obtained by the methods, or the product prepared from the granules, or the broken material of the product.