WO2020014871A1

WO2020014871A1 - Dual initiation curing system for improving printing layer veins and preparation method therefor

Info

Publication number: WO2020014871A1
Application number: PCT/CN2018/096000
Authority: WO
Inventors: 赵�卓; 冯玉林; 黄立; 张志飞; 贺晓宁; 方绚莱
Original assignee: 深圳摩方新材科技有限公司
Priority date: 2018-07-17
Filing date: 2018-07-17
Publication date: 2020-01-23

Abstract

Provided are a dual initiation curing system for improving printing layer veins and a preparation method therefor. The system comprises, in percentages by weight: 10 - 90 wt% of an active oligomer, 20 - 50 wt% of an active diluent, 0.2 - 6 wt% of a photoinitiator, 0.2 - 3 wt% of a thermal initiator, 0.1 - 5 wt% of a light absorber and 1.5 – 5 wt% of other auxiliary agents. Through the introduction of the thermal initiator into a photosensitive resin system, the heat release of free radical polymerization is used for further initiating the thermal initiator; and the continued reaction and curing of an insufficiently cured active oligomer and active diluent are promoted, so that the problem of a sample performance defect due to curing nonuniformity is solved.

Description

Double-initiation curing system for improving print layer texture and preparation method thereof

Technical field

The invention belongs to the field of 3D printing, and particularly relates to a double-priming system for improving the texture of a printing layer and a preparation method thereof.

Background technique

The basic principles of 3D printing can be summarized as stacked manufacturing, which can be divided into the following types: stereolithography (SLA), digital light processing (DLP), selective laser sintering (SLS), fused deposition / fuse deposition (FDM) ), Layered solid manufacturing (LOM), electron beam fuse deposition (EBFF) and other forming processes. Based on various conditions, different technologies have their own advantages and disadvantages.

The printing process is generally: designing a three-dimensional solid model through modeling software, slicing the model according to the designed solidified layer thickness using the slicing software, and importing the sliced file into the control software; then the above model is processed point by point / Layer-by-layer exposure curing, when a layer is processed, a section of the sample is generated; then, the molding platform is raised or lowered by a distance of the solidified layer thickness, and the above steps are repeated, and the layered layering is accumulated to form a three-dimensional solid model.

In the current 3D printing technology based on surface projection micro stereolithography (DLP), the DMD micro-lens matrix is usually used to provide the exposed image. The DMD chip integrates a large number of micro-lenses, and the single-pixel switch is realized by controlling the deflection angle of the micro-lenses, and the gray scale is realized by the time of opening and closing. However, because the microlenses are square, this results in a sawtooth phenomenon on the edges of the two-dimensional graphics of the XY plane with arcs. This results in a large surface roughness of the final printed sample, which is difficult to directly apply to the sample printing with high accuracy requirements. In addition, due to the existence of a certain gap in each micro-lens, this results in the incomplete filling of light in the entire exposed area, and there are countless small gaps. In the case where the uniformity of the exposure intensity distribution of the printed area is required (such as optical components), there is an internal unevenness problem, which affects the performance of the final sample.

3D printing technology adopts a layer-by-layer stacking method to realize the manufacture of three-dimensional structures. In order to control the thickness of each layer of exposure and curing, a light absorber is generally added to the resin material. During the exposure process, the light begins to decay after entering the resin liquid surface, and the attenuation of an exposure layer thickness is 0. Therefore, in the exposure of each layer, there is also a non-uniformity in light intensity, which in turn causes non-uniformity in the print sample from top to bottom. As shown in Figure 1, this unevenness directly causes problems in the strength, hardness, and optical properties of the final printed sample.

At present, in the 3D printing technology based on surface projection micro stereolithography (DLP), a DMD micro-lens matrix is generally used to provide an exposed image. The DMD chip integrates a large number of micro-lenses. By controlling the deflection angle of the micro-lenses, a single pixel switch can be realized, and the gray scale can be realized by the on and off time. However, because the microlenses are square, this results in a sawtooth phenomenon on the edges of the two-dimensional graphics of the XY plane with arcs. This results in a large surface roughness of the final printed sample, which is difficult to directly apply to the sample printing with high accuracy requirements. In addition, due to the existence of a certain gap in each micro-lens, this results in the incomplete filling of light in the entire exposed area, and there are countless small gaps. In the case where the uniformity of the exposure intensity distribution of the printed area is required (such as optical components), there is an internal unevenness problem, which affects the performance of the final sample.

Summary of the invention

The invention provides a dual-initiation system for improving the texture of a printing layer, which comprises, by weight percentage, 10-90 wt% of active oligomers, 20-50 wt% of reactive diluent, 0.2-6 wt% of photoinitiator, and 0.2- 3 wt%, light absorbing agent 0.1-5% by weight, and other auxiliaries 1.5-5%.

The invention provides a method for improving defects in a printed sample due to pixel gap, Z-direction layer pattern, and uneven exposure within a layer by introducing a dual curing system into a 3D printed photosensitive resin material. In general, the principle of 3D printing is to use ultraviolet laser to cure liquid resin materials that are very sensitive to ultraviolet light. The resin tank is filled with liquid photosensitive resin, and the liquid resin is processed according to the cross-section information of each layer of the part under computer control. The surface is scanned point by line / layer by layer. The scanned resin undergoes photopolymerization and instantaneously cures to form a thin layer, and then the molding platform moves a layer height. When the liquid resin covers the surface of the cured part with new liquid resin, it is scanned / exposed and cured again. The solidified layer is bonded to the solidified layer on the front, and this process is repeated until the entire part is manufactured.

The polymerization degree curve of the photosensitive resin is shown in FIG. 3. It can be seen that after curing to a certain degree, the active double bond functional group in the system is basically consumed, and the performance of the material reaches a stable state. The uneven exposure caused by the above reasons will cause the curing degree of some resins to fail to reach this stable state, and then affect the performance of printed products. Therefore, the second type of initiation system is introduced into the photosensitive resin, and when the degree of photo-curing is insufficient, the curing reaction is initiated again, so that all the resin materials reach a stable curing degree, and the performance defects of the printed samples caused by the difference in curing degree are eliminated. In the process of radical polymerization initiated by ultraviolet light, a large amount of heat can be released, and its energy can trigger a variety of radical thermal initiators, thereby initiating a secondary polymerization reaction. Therefore, during the printing process, firstly, the photo radical polymerization of the resin system is initiated by exposure to form a certain geometric shape. Due to the exothermicity of the free radical reaction, the thermal initiator in the system can be initiated in the exposed area, further initiating the polymerization of the resin. This can solve the uneven curing degree in the layer caused by the attenuation of light inside the resin, and then improve the performance defects caused by the uneven curing degree in the final printed sample.

Preferably, the reactive oligomer uses acrylate, acrylamide, and silane acrylate; and the reactive diluent uses bifunctional or polyfunctional alkyl acrylate, alkoxy acrylate, or ethylene glycol acrylate.

Preferably, the photoinitiator is a free radical type photoinitiator which has absorption under ultraviolet light of 250-440 nm, and the free radical type photoinitiator is phenylbis (2,4,6-trimethylbenzoyl) Phosphine oxide, ethyl 2,4,6-trimethylbenzoylphosphonate, diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide, bis 2,6-difluoro-3- Pyrrolephenylferrocene, 2-isopropylthiaxanthone, 4-phenylbenzophenone, 2-phenylbenzyl-2-dimethylamine-1- (4-morpholinebenzylphenyl) One or more of methyl ethyl ketone.

Preferably, the thermal initiator is a thermal initiator having an initiation temperature of 60-90 ° C, and the thermal initiator is azobisisobutyronitrile, azobisisoheptonitrile, cumene hydroperoxide, or dibenzoyl peroxide. One or more of acyl, dodecanoyl peroxide, and dicumyl peroxide.

Preferably, the light absorber is a light absorber capable of absorbing 250-440 nm ultraviolet light, and the light absorber is 2,4-dihydroxyxylone, 2-hydroxy-4-n-octyloxybenzophenone, 2 -(2ˊ-hydroxy-5ˊ-methylphenyl) benzotriazole, 2- (2-hydroxy-3-tert-butyl-5-methylphenyl) -5-chlorobenzotriazole, monobenzene One or more of resorcinol formate and 2- (4,6-diphenyl-1,3,5-triazine-2) -5-n-hexaneoxyphenol.

Preferably, the functional auxiliaries include a defoaming agent, a leveling agent and an adhesion promoter, and the addition amount of each auxiliary is 0.5-4%; the antifoaming agent uses aliphatic amide, polyethylene glycol, modified polydiethylene At least one of methylsiloxane and silicone-free polymer solution; leveling agent using polyacrylate compound, polyether / polyester / aralkyl-modified dimethylsiloxane solution, and fluorocarbon At least one of a modified polyacrylate copolymer solution; the adhesion promoter uses at least one of an aminosilane, a phosphate polymer, and an epoxysilane oligomer.

Preferably, the acrylate is at least one of pure acrylate, epoxy acrylate, urethane acrylate, and polyester acrylate.

Correspondingly, the present invention also provides a method for preparing a photosensitive resin, comprising the steps of: stirring an oligomer, a reactive diluent, a photoinitiator, a thermal initiator, a light absorber, and a functional auxiliary at a moderate mixing speed (500-1000 revolutions / min) for 5-15 hours, and then stirred at high speed (greater than 1000, less than or equal to 1500 revolutions / min) for 0.5-1 hours to obtain a uniform photocuring system.

Preferably, the viscosity of the light curing system is in the range of 100-3000 cp.

Correspondingly, the present invention also provides a light curing molding process method, which includes the following steps:

Step A: Use a modeling software, such as SolidWorks, AutoCAD to design a three-dimensional solid model, use slicing software, such as magics, to slice the model according to the designed solidified layer thickness, and import the sliced file to the light curing rapid prototyping machine. In the control software;

Step B: Place the photo-curing system under a light-curing rapid prototyping machine to perform point-by-point / layer-by-layer exposure curing. When one layer is processed, a section of the sample is generated; then the molding platform is raised or lowered by one curing layer thickness, that is 15-50μm distance;

Step C: Repeat the above steps, layer by layer, accumulate and form, and obtain a three-dimensional solid model.

Preferably, the wavelength of the photo-curing rapid prototyping machine is 355 nm, 365 nm, 385 nm, 405 nm, or 420 nm.

Preferably, the light curing rapid prototyping machine adopts SLA or DLP.

The beneficial effects of the present invention:

1. The invention can overcome the performance defect of the printed sample caused by the uneven curing degree at the interlayer interface caused by the layer-by-layer molding process during the 3D printing process.

2. The invention can improve the performance defects of the printed sample caused by uneven exposure caused by the gap between the pixels between each layer (laser spot or DMD lens) and uneven curing.

3. In the present invention, a thermal initiator is introduced into the photosensitive resin system, and the thermal initiator is further induced by the exothermic heat of radical polymerization, so as to promote the continuous reaction and curing of the active oligomer and reactive diluent with insufficient curing. So as to solve the problem of sample performance defects caused by uneven curing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of uneven exposure within a layer during printing.

Figure 2 shows the gap between DMD micromirrors.

FIG. 3 is a degree of polymerization curvature of the photosensitive resin.

detailed description

The preferred embodiments of the present invention are described in further detail below:

Example 1

According to the weight percentage, the active oligomer polyurethane acrylate 25%, polyester acrylate 20%, polyethylene glycol diacrylate 20%, reactive diluent acrylmorpholine 15%, isopropyl acrylate 10%, light Initiator phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide 3%, leveling agent acrylate compound 2%, defoamer polyethylene glycol 400 2%, light absorber 2,4 -Dihydroxyxylone 1%, thermal initiator dibenzoyl peroxide 2%, mixed at 500 rpm / min for 5h, and then 1200 rpm / min for 0.5h, to obtain a uniform photocuring system.

A three-dimensional solid model is designed by the modeling software. The slice software is used to slice the model according to the designed solidified layer thickness. The sliced file is imported into the light curing rapid prototyping machine control software, and the light curing system is placed in the SLA light. Under the curing rapid prototyping machine, the wavelength is 355nm for point-by-point exposure curing. When one layer is processed, a cross-section of the sample is generated; then the molding platform is raised or lowered by a distance of 15 μm, and the above steps are repeated, layer by layer. Cumulative molding to obtain a three-dimensional solid model.

Example 2

By weight percentage, active oligomer polyurethane acrylate 20%, polyester acrylate 25%, polyethylene glycol diacrylate 20%, reactive diluent acrylmorpholine 10%, isopropyl acrylate 15%, photoinitiated Agent 2,4,6-trimethylbenzoylphosphonic acid ethyl ester 3%, leveling agent polyether modified dimethylsiloxane solution 2%, defoamer modified polydimethylsiloxane 2 %, Light absorber 2-hydroxy-4-n-octyloxybenzophenone 1%, thermal initiator azobisisobutyronitrile 2% mixed, stirred at 800 rpm for 15h, and then 1200 rpm at high speed Stir for 1 h to obtain a uniform photo-curing system.

A three-dimensional solid model is designed by the modeling software. The slice software is used to slice the model according to the designed solidified layer thickness. The sliced file is imported into the light curing rapid prototyping machine control software, and the light curing system is placed on the DLP light. Under the curing rapid prototyping machine, the wavelength is 365nm for point-by-point exposure curing. When one layer is processed, a cross-section of the sample is generated; then the molding platform is raised or lowered by a distance of 25 μm, and the above steps are repeated, layer by layer. Cumulative molding to obtain a three-dimensional solid model.

Example 3

By weight percentage, active oligomer polyurethane acrylate 20%, polyester acrylate 20%, polyethylene glycol diacrylate 25%, reactive diluent acrylmorpholine 12%, isopropyl acrylate 13%, photoinitiated Agent diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide 3%, leveling agent polyester modified dimethylsiloxane solution 2%, defoamer aliphatic amide 2%, light Absorbent 2- (2ˊ-hydroxy-5ˊ-methylphenyl) benzotriazole 1%, thermal initiator azobisisoheptonitrile 2%, mixed at 1000 rpm for 10h, and then 1500 rpm / min was stirred for 0.7 h to obtain a uniform photo-curing system.

A three-dimensional solid model is designed by the modeling software. The slice software is used to slice the model according to the designed solidified layer thickness. The sliced file is imported into the light curing rapid prototyping machine control software, and the light curing system is placed in the SLA light. Under the curing rapid prototyping machine, the wavelength is 385nm for layer-by-layer exposure curing. When one layer is processed, a cross-section of the sample is generated; then the molding platform is raised or lowered by a distance of 30 μm, and the above steps are repeated, layer by layer. Cumulative molding to obtain a three-dimensional solid model.

Example 4

By weight percentage, active oligomer polyurethane acrylate 30%, polyester acrylate 20%, polyethylene glycol diacrylate 15%, reactive diluent acrylmorpholine 11%, isopropyl acrylate 14%, photoinitiated Agent bis 2,6-difluoro-3-pyrrolephenylferrocene 3%, leveling agent aralkyl modified dimethylsiloxane solution 2%, antifoam agent polyethylene glycol 400 2%, light Absorbent 2- (2-hydroxy-3-tert-butyl-5-methylphenyl) -5-chlorobenzotriazole 1%, thermal initiator 2% cumene hydroperoxide mixed, 900 rpm Stir for 12 hours per minute, and then stir at 0.8 rpm for 0.8 hours at high speed to obtain a uniform photo-curing system.

A three-dimensional solid model is designed by the modeling software. The slice software is used to slice the model according to the designed solidified layer thickness. The sliced file is imported into the light curing rapid prototyping machine control software, and the light curing system is placed on the DLP light. Under the curing rapid prototyping machine, the wavelength is 405nm for layer-by-layer exposure curing. When one layer is processed, a cross-section of the sample is generated; then the molding platform is raised or lowered by a distance of 40 μm of the curing layer. Cumulative molding to obtain a three-dimensional solid model.

Example 5

By weight percentage, active oligomer polyurethane acrylate 22%, polyester acrylate 25%, polyethylene glycol diacrylate 18%, reactive diluent acrylmorpholine 14%, isopropyl acrylate 11%, photoinitiated 2% isopropylthioanthrone, leveling agent fluorocarbon modified polyacrylate copolymer solution 2%, defoamer polyethylene glycol 400%, light absorber resorcinol monobenzoate Ester, 2- (4,6-diphenyl-1,3,5-triazine-2) -5-n-hexaneoxyphenol 1%, thermal initiator dibenzoyl peroxide 2%, medium speed Stir at 700 rpm for 8h, and then stir at 1500 rpm for 0.6h to obtain a uniform photocuring system.

A three-dimensional solid model is designed by the modeling software. The slice software is used to slice the model according to the designed solidified layer thickness. The sliced file is imported into the light curing rapid prototyping machine control software, and the light curing system is placed on the DLP light. Under the curing rapid prototyping machine, the wavelength is 420nm for layer-by-layer exposure curing. When one layer is processed, a cross-section of the sample is generated; then the molding platform is raised or lowered by a distance of 35 μm of the cured layer. Cumulative molding to obtain a three-dimensional solid model.

Comparative Example 1

The formula of the initiator is not heated, and the diluent isopropyl acrylate is increased to 100%. The other conditions are the same as in Example 1.

Comparative Example 2

The initiator formulation is not heated, and the diluent isopropyl acrylate is increased to 100%. The other conditions are the same as in Example 2.

Comparative Example 3

The initiator formulation is not heated, and the diluent isopropyl acrylate is increased to 100%. The other conditions are the same as those in Example 3.

Comparative Example 4

The initiator formulation is not heated, and the diluent isopropyl acrylate is increased to 100%. The other conditions are the same as those in Example 4.

Comparative Example 5

The initiator formulation is not heated, and the diluent isopropyl acrylate is increased to 100%. The other conditions are the same as those in Example 5.

In Examples 1-5 and Comparative Examples 1-5, a DLP and a 3D printing device were manufactured by using a 405nm light source to print and mold. The comparison performance is shown in Table 1:

Table 1

The above is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without deviating from the concept of the present invention, several simple deductions or replacements can be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

A dual-initiation curing system for improving the texture of a printing layer is characterized in that, in terms of weight percentage, it includes: active oligomer 10-90wt%, reactive diluent 20-50wt%, photoinitiator 0.2-6wt%, thermal initiator 0.2-3 wt%, light absorbing agent 0.1-5 wt%, and other auxiliaries 1.5-5%.
The dual-initiation curing system for improving the texture of a printing layer according to claim 1, wherein the reactive oligomer uses acrylate, acrylamide, and silane acrylate; and the reactive diluent uses a bifunctional or polyfunctional alkyl group. Acrylate, alkoxyacrylate or ethylene glycol acrylate.
The dual-initiation curing system for improving the texture of a print layer according to claim 1, wherein the photo-initiator is a free-radical photo-initiator which absorbs under 250-440 nm ultraviolet light, and the free-radical photo-initiator Phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide, ethyl 2,4,6-trimethylbenzoylphosphonic acid, diphenyl (2,4,6-trimethyl) Benzoyl) phosphine oxide, bis 2,6-difluoro-3-pyrrolephenylferrocene, 2-isopropylthioanthrone, 4-phenylbenzophenone, 2-phenylbenzyl- One or more of 2-dimethylamine-1- (4-morpholine benzylphenyl) butanone.
The dual-initiation curing system for improving the print layer texture according to claim 1, wherein the thermal initiator is a thermal initiator having an initiation temperature of 60-90 ° C, and the thermal initiator is azobisisobutyronitrile, One or more of azobisisoheptonitrile, cumene hydroperoxide, dibenzoyl peroxide, lauryl peroxide, and dicumyl peroxide.
The dual-initiation curing system for improving the texture of a printing layer according to claim 1, wherein the light absorber is a light absorber capable of absorbing 250-440 nm ultraviolet light, and the light absorber is 2,4-dihydroxyxylene Ketone, 2-hydroxy-4-n-octyloxybenzophenone, 2- (2ˊ-hydroxy-5ˊ-methylphenyl) benzotriazole, 2- (2-hydroxy-3-tert-butyl- 5-methylphenyl) -5-chlorobenzotriazole, resorcinol monobenzoate, 2- (4,6-diphenyl-1,3,5-triazine-2) -5- One or more of n-hexaneoxyphenol.
The dual-initiation curing system for improving the texture of a print layer according to claim 1, wherein the functional assistants include a defoaming agent, a leveling agent, and an adhesion promoter, and the additive amount ranges from 0.5 to 4%. ; Antifoaming agent using at least one of aliphatic amide, polyethylene glycol, modified polydimethylsiloxane and silicone-free polymer solution; leveling agent using polyacrylate compound, polyether / At least one of a polyester / aralkyl-modified dimethylsiloxane solution and a fluorocarbon-modified polyacrylate copolymer solution; an adhesion promoter using an aminosilane, a phosphate polymer, and an epoxy At least one of silane oligomers.
The dual-initiation curing system for improving the texture of a print layer according to claim 2, wherein the acrylate is at least one of pure acrylate, epoxy acrylate, urethane acrylate, and polyester acrylate.
A method for preparing a dual-initiation curing system for improving the texture of a print layer according to claim 1, comprising the steps of: oligomer, reactive diluent, photoinitiator, thermal initiator, light absorber 2. The functional additive is stirred at a medium speed for 5-15h at a certain ratio, and then stirred at high speed for 0.5-1h to obtain a uniform light curing system.
The method according to claim 8, wherein the viscosity of the obtained photocuring system is 100-3000 cp.
A light curing molding process method is characterized in that it includes the following steps:

Step A: Design a three-dimensional solid model by modeling software, slice the model according to the designed solidified layer thickness using the slicing software, and import the sliced file into the light curing rapid prototyping machine control software;

Step B: Place the dual-initiation curing system for improving the print layer texture according to claim 1 under a light-curing rapid prototyping machine to perform point-by-point / layer-by-layer exposure curing. When one layer is processed, a section of the sample is generated. ; Then the molding platform rises or falls a distance of a solidified layer thickness;

Step C: Repeat the above steps, layer by layer, accumulate and form, and obtain a three-dimensional solid model.