CN113174016A - Low-viscosity flexible photosensitive resin for 3D printing and preparation method and application thereof - Google Patents

Abstract

The invention provides a low-viscosity flexible photosensitive resin for 3D printing and a preparation method and application thereof. The low-viscosity flexible photosensitive resin for 3D printing comprises the following components in parts by weight: 30-50 parts of acrylic ester; 3-5 parts of a photoinitiator; 45-60 parts of an active diluent; 0-1.5 parts of an auxiliary agent; wherein the viscosity of the acrylate is 20-300 cps; the active diluent is a mixture of an ester active diluent and an ether active diluent in a weight ratio of 1: 0.8-2. According to the invention, the acrylate with low viscosity is selected as the prepolymer, and is matched with the specific active diluent, so that the viscosity of the photosensitive resin can be effectively reduced, and the curing rate and the cured toughness of the photosensitive resin can be greatly improved.

Description

Low-viscosity flexible photosensitive resin for 3D printing and preparation method and application thereof

Technical Field

The invention belongs to the technical field of 3D printing materials, and particularly relates to a low-viscosity flexible photosensitive resin for 3D printing, and a preparation method and application thereof.

Background

Additive Manufacturing (also known as 3D printing) is a technology for Manufacturing an object by using a bondable material such as powder, metal, or plastic and printing layer by layer on the basis of a digital model file. 3D printing technology has been rapidly developed and applied in recent decades, and various techniques for building three-dimensional prototypes have been developed. Additive manufacturing technology standard ASTM F2792-12 divides additive manufacturing technology into seven major categories: adhesive jetting, direct energy deposition, material extrusion, material jetting, powder bed melting, lamination, and slot photo-polymerization.

Inkjet printing technology belongs to the class of material ejection and is defined as an additive manufacturing process that is achieved by selective deposition of droplets of a modeling material. The 3D ink-jet printing can mainly adopt two types of materials, namely a thermotropic phase change material and a photocuring material, as forming materials for printing. The problem of poor mechanical properties is generally existed in the photocuring material that the thermal phase change material is subjected to cross-linking polymerization. In practice, the requirements for materials for inkjet 3D printing are mainly: firstly, the nozzle is a fine hole, so that the fluidity of the material is required to be very good, and the viscosity is generally below 50 cps; secondly, the material curing time is required to be short, generally within 2s, because the nozzle moves at a high speed, and thirdly, because the material is placed in a material groove in a printer in a working state and a non-working state, the printer works with a working temperature of 45-70 ℃, the material is required to have stability when being stored for a long time at a certain temperature.

The light curing molding technology (SLA), also called selective curing of liquid photosensitive resin, is a popular direction in recent years, and the principle of the technology is that ultraviolet light with certain wavelength and intensity is used to irradiate liquid photosensitive resin raw materials to rapidly generate a crosslinking reaction to generate a cured product.

As known from photo-curing mechanism, the material inevitably has double bonds to participate in the reaction during the use process, and the double bond reaction generates a large shrinkage stress in the material, so that the material lacks the effect of releasing stress, and the material is large in brittleness. At present, the brittleness problem of the material is mainly improved by adding rubber components, for example, modified butadiene rubber is introduced into a formula of a 3D printing material in Chinese patent CN105199178A, and a component of solid rubber is added into the formula in Chinese patent CN105175651A, so that the method has the advantages of greatly improving the impact strength, but the curing time is long (15-60 s), and the application in actual printing is limited.

Meanwhile, the shrinkage stress generated by the double bond in the free radical polymerization in the reaction process can also cause the warping deformation of the printed product, and the precision of the product can be affected if the product is serious. Chinese patent CN110527030A provides a 3D printing photosensitive resin with the shrinkage rate below 1% and a preparation method thereof, and the patent reduces the polarity of monomers and oligomers by adding filler components such as silicon dioxide, iron oxide yellow powder, talcum powder and the like to realize the reduction of shrinkage, and has the defects of increased viscosity of a system and limited application range.

In addition, according to the principle of SLA, the printing material has high requirements on photocuring time, incomplete curing and low one-time curing degree can influence printing precision, and the photocuring time of the conventional 3D printing photosensitive resin is long.

Therefore, there is a need to develop an SLA printing material with low viscosity, fast curing speed and excellent mechanical properties.

Disclosure of Invention

The invention aims to overcome the defects of high viscosity, low curing speed and poor mechanical properties (such as toughness) of a 3D printing material in the prior art, and provides a low-viscosity flexible photosensitive resin for 3D printing, which has low viscosity, high toughness and short curing time. The low-viscosity flexible photosensitive resin for 3D printing has the viscosity of 13-25 cps at 55 ℃ and can be completely cured within 2s, the tensile strength of a consumable material obtained by printing is 14-20 MPa, the elongation at break is 144-195%, and the volume shrinkage is within 6%.

Another object of the present invention is to provide a method for preparing the low viscosity flexible photosensitive resin for 3D printing.

Another object of the present invention is to provide an application of the low viscosity flexible photosensitive resin for 3D printing in preparing a 3D printing material.

In order to achieve the purpose, the invention adopts the following technical scheme:

a low-viscosity flexible photosensitive resin for 3D printing comprises the following components in parts by weight:

wherein the viscosity of the acrylate at 25 ℃ is 20-300 cps;

the active diluent is a mixture of an ester active diluent and an ether active diluent in a weight ratio of 1: 0.8-2.

The inventor of the invention discovers through a great deal of research that the light-cured resin with high light-curing speed and low viscosity can be prepared by selecting the acrylate prepolymer with low viscosity and cooperatively matching with the specific reactive diluent.

The reason for this is probably that the acrylate prepolymer with lower viscosity is selected, so that the prepared photo-curing resin reaction system has lower viscosity, which is beneficial to the beginning of the synthesis reaction; however, in general, as the synthesis reaction proceeds, the viscosity of the reaction system increases to a certain extent, and through further research, the inventors of the present invention found that, if an ester reactive diluent and an ether reactive diluent are compounded, the viscosity of the reaction system during the synthesis process can be effectively reduced, and further, a photocurable resin with a lower viscosity and a faster photocuring rate can be prepared, and at the same time.

Preferably, the acrylate has a viscosity of 80 to 200cps at 25 ℃.

Preferably, the weight ratio of the ester reactive diluent to the ether reactive diluent is 1: 1-1.5.

Preferably, the acrylate is one or both of a urethane acrylate or an epoxy acrylate.

Further preferably, the urethane acrylate is one or both of an aromatic urethane acrylate and an aliphatic acrylate.

Preferably, the photoinitiator is one or a combination of phenyl bis (2,4, 6-trimethylbenzoyl) phosphine oxide, 2,4, 6-trimethylbenzoyl diphenyl phosphine oxide, ethyl 2,4, 6-trimethylbenzoyl phosphonate, diaryl iodonium hexafluorophosphate salt or triaryl iodonium hexafluorophosphate salt.

Preferably, the ester reactive diluent is mono-and/or multifunctional, and is further preferably one or a combination of more of 2-hydroxypropyl methacrylate, diethylene glycol dimethacrylate or dipentaerythritol hexaacrylate. The mono-and/or multi-functionality ester reactive diluent is selected, so that the prepared photocuring resin has high photocuring rate and good mechanical properties after photocuring.

Preferably, the ether reactive diluent is one or two of polyethylene glycol diglycidyl ether or 1, 4-butanediol diglycidyl ether.

Preferably, the auxiliary agent is one or a combination of several of a sensitizer, a leveling agent and a polymerization inhibitor.

Preferably, the sensitizer is one or a combination of N-methyldiethanolamine, N '-ethyl p-dimethylaminobenzoate or N, N' -dimethylamino benzamide.

Preferably, the leveling agent is one or a combination of more of Glide 100, Glide 432, Glide 435, Glide 440, Flow 300, Flow425, BYK 333, BYK 371, BYK 373, BYK 361, perenol s71uv, perenol s83uv or EFKA 3883.

Preferably, the polymerization inhibitor is one or two of p-hydroxyanisole and 2, 6-di-tert-butyl-p-cresol.

The preparation method of the low-viscosity flexible photosensitive resin for 3D printing comprises the following steps:

s1, uniformly mixing acrylic ester, an active diluent and an auxiliary agent under a light-proof condition to obtain a mixture;

s2, adding a photoinitiator into the mixture obtained in the step S1, reacting for 10-30 min at 45-70 ℃, and filtering and degassing to obtain the low-viscosity flexible photosensitive resin for 3D printing.

Preferably, the temperature of the mixing in the step S1 is 45-70 ℃.

Preferably, the filtration is to filter the mixture by using a micro-porous filtration membrane with the pore diameter of 0.22-0.45 μm.

Preferably, the degassing mode is one or a combination of several of reduced pressure degassing, normal pressure degassing or stirring degassing, and further preferably reduced pressure degassing.

Preferably, the degassing time is 10-120 min, and more preferably 15-30 min.

The application of the low-viscosity flexible photosensitive resin for 3D printing in the preparation of 3D printing materials is also within the protection scope of the invention.

Compared with the prior art, the invention has the following beneficial effects:

according to the invention, the acrylate with low viscosity is selected as the prepolymer, and is matched with the specific active diluent, so that the viscosity of the photosensitive resin can be effectively reduced, and the curing rate and the cured toughness of the photosensitive resin can be greatly improved. The low-viscosity flexible photosensitive resin for 3D printing has the viscosity of 13-26 cps at 55 ℃ and can be completely cured within 2s, the tensile strength of a consumable material obtained by printing is 14-20 MPa, the elongation at break is 144-195%, and the volume shrinkage is within 6%.

Detailed Description

The present invention is further illustrated by the following specific examples, which are not intended to limit the invention in any way. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Examples 1 to 15

The embodiment provides a low-viscosity flexible photosensitive resin for 3D printing, which is specifically prepared by the following steps:

s1, adding acrylate, an active diluent and an auxiliary agent into a light-proof container, and uniformly mixing at 45-70 ℃ to obtain a mixture;

s2, adding a photoinitiator into the mixture obtained in the step S1, reacting for 10-30 min at 45-70 ℃, filtering the mixture by using a microporous filtering membrane with the aperture of 0.22-0.45 mu m, and degassing under reduced pressure for 30min under the vacuum degree of 0.1MPa to obtain the low-viscosity flexible photosensitive resin for 3D printing.

TABLE 1 raw material components (parts by weight) of the examples

Comparative example 1

This comparative example provides a photosensitive resin, which is different from example 1 in that the ether-based reactive diluent is replaced with the ester-based reactive diluent, 2-hydroxypropyl methacrylate.

Comparative example 2

This comparative example provides a photosensitive resin, which is different from example 1 in that an ester-based diluent is replaced with an ether-based reactive diluent, polyethylene glycol diglycidyl ether.

Comparative example 3

This comparative example provides a photosensitive resin, which is different from example 1 in that the reactive diluent is replaced with tetrahydrofuran acrylate, which is a common tetrahydrofuran-based reactive diluent.

Comparative example 4

The comparative example provides a photosensitive resin, which is different from example 1 in that an acrylate is replaced with an aliphatic polyurethane hexaacrylate RJ822 having a viscosity of 350 to 500 cps.

Performance testing

The photosensitive resins prepared in the examples and comparative examples were subjected to performance tests, and the specific test items and test methods were as follows:

1. viscosity: the dynamic viscosity values of the photosensitive resins prepared in examples and comparative examples were measured under the conditions of 55 deg.C (the operating temperature of an ink jet printer) in accordance with GB/T10247-1988;

2. storage stability: judging the storage stability by the storage time of reaching the viscosity of 30cps according to GB/T7123.2-2002, wherein the longer the storage time is, the better the storage stability is;

3. curing time: the photosensitive resins prepared in examples and comparative examples were coated to obtain a sample having a thickness of 100 μm, the sample was irradiated with light, the time from the start of the irradiation with light to the completion of the reaction was defined as the time from the complete curing of the surface of the sample,the difference between the two is the time required by the complete curing of the sample, wherein the irradiation intensity of the ultraviolet light is 8W/cm²The determination standard of the surface complete curing is that a finger touches the surface of the cured film, and the surface is considered to be completely cured without leaving fingerprint traces (consistent with the test method of patent CN 107501477A);

4. mechanical properties: after consumables obtained by 3D printing of the photosensitive resins prepared in the examples and the comparative examples are prepared into tensile sample bars according to ASTM D412-2016, the tensile strength and the elongation at break of the consumables are tested;

5. volume shrinkage: consumables obtained by 3D printing of the photosensitive resin prepared in each embodiment and the comparative example are tested according to GB/T6488-2008 standard;

6. quick rebound ability: after the tensile specimen of ASTM D412-2016 was folded in half, it was checked whether the specimen could be recovered in about 1 second.

The results of the above tests are shown in Table 2.

Table 2 results of performance test of examples and comparative examples

As can be seen from the results in Table 2, the viscosity of the photosensitive resin prepared by the embodiments of the invention is 13-26 cps at 55 ℃, and the curing time is within 2 s; the 3D printing consumable prepared by the method has good mechanical properties, the tensile strength is 14-20 MPa, the elongation at break is 144-195%, the volume shrinkage rate is within 6%, and the 3D printing consumable has quick resilience capability of recovering about 1 s.

Compared with the prior art, the photosensitive resin prepared by the method has the advantages that a single ester reactive diluent and a single ether reactive diluent are selected in comparative examples 1 and 2, the viscosity of the prepared photosensitive resin is higher at the working temperature, the photocuring rate is lower, the toughness after curing is also lower, and the comprehensive performance is poorer than that of the photosensitive resin; comparative example 3 only selects other common reactive diluents, and the photo-curing rate of the prepared photosensitive resin is slower; comparative example 4, since the acrylate having a high viscosity was selected, the viscosity was high even though the reactive diluent of the present invention was selected, and thus it could not be used as a 3D printing material.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (10)

1. The low-viscosity flexible photosensitive resin for 3D printing is characterized by comprising the following components in parts by weight:

wherein the viscosity of the acrylate at 25 ℃ is 20-300 cps;

the active diluent is a mixture of an ester active diluent and an ether active diluent in a weight ratio of 1: 0.8-2.

2. The low viscosity flexible photosensitive resin for 3D printing according to claim 1, wherein the acrylate has a viscosity of 80 to 200cps at 25 ℃.

3. The low viscosity flexible photosensitive resin for 3D printing according to claim 1, wherein the weight ratio of the ester reactive diluent to the ether reactive diluent is 1:1 to 1.5.

4. The low viscosity flexible photosensitive resin for 3D printing according to claim 1, wherein the acrylate is one or both of urethane acrylate or epoxy acrylate.

5. The low viscosity flexible photosensitive resin for 3D printing according to claim 1, wherein the photoinitiator is one or more of phenyl bis (2,4, 6-trimethylbenzoyl) phosphine oxide, 2,4, 6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4, 6-trimethylbenzoyl phosphonate, diaryliodonium hexafluorophosphate or triaryliodonium hexafluorophosphate.

6. The low viscosity flexible photosensitive resin for 3D printing according to claim 1, wherein the ester reactive diluent is a mono-and/or multi-functional ester reactive diluent, and the ester reactive diluent is one or more of 2-hydroxypropyl methacrylate, diethylene glycol dimethacrylate or dipentaerythritol hexaacrylate.

7. The low viscosity flexible photosensitive resin for 3D printing according to claim 1, wherein the ether reactive diluent is one or both of polyethylene glycol diglycidyl ether and 1, 4-butanediol diglycidyl ether.

8. The low-viscosity flexible photosensitive resin for 3D printing according to claim 1, wherein the auxiliary agent is one or more of a sensitizer, a leveling agent or a polymerization inhibitor.

9. The method for preparing the low viscosity flexible photosensitive resin for 3D printing according to any one of claims 1 to 8, comprising the steps of:

s1, uniformly mixing acrylic ester, an active diluent and an auxiliary agent under a light-proof condition to obtain a mixture;

s2, adding a photoinitiator into the mixture obtained in the step S1, reacting for 10-30 min at 45-70 ℃, and filtering and degassing to obtain the low-viscosity flexible photosensitive resin for 3D printing.

10. Use of the low viscosity flexible photosensitive resin for 3D printing according to any one of claims 1 to 8 for preparing a 3D printing material.