WO2017000923A1

WO2017000923A1 - Low-temperature nylon powder material for selective laser sintering and preparation method therefor

Info

Publication number: WO2017000923A1
Application number: PCT/CN2016/088738
Authority: WO
Inventors: 史玉升; 闫春泽; 史云松; 傅轶; 汪艳; 魏青松; 刘洁; 李晨辉; 郑立; 王雁国
Original assignee: 广东银禧科技股份有限公司
Priority date: 2015-06-30
Filing date: 2016-07-05
Publication date: 2017-01-05
Also published as: CN104910616B; CN104910616A

Abstract

The present invention relates to the technical field of polymer composites, in particular to a low-temperature nylon powder material for selective laser sintering. The low-temperature nylon powder material mainly comprises nylon 12 particles, dodecanedioic acid, double amino-terminated polyethylene glycol, deuterated trifluoroacetic acid, antioxidant, solvent, nucleating agent, plasticizer and silane coupling agent. The low-temperature nylon powder material is prepared by the following steps: uniformly mixing the dodecanedioic acid and nylon 12 particles and putting into a reaction kettle; adding double amino-terminated polyethylene glycol and deuterated trifluoroacetic acid into the reaction kettle; heating and starting stirring to obtain a product; putting the product together with antioxidant, solvent, nucleating agent, plasticizer and silane coupling agent into the reaction kettle, and closing the kettle with a cover; vacuumizing the reaction kettle and introducing nitrogen displacement for protection; starting stirring and reducing the temperature of the kettle body to room temperature; taking out the materials, drying and performing ball milling; and drying the powder to obtain powder with good sphericity and fluidity. The low-temperature nylon powder material provided by the present invention has the characteristics of low preheating temperature, wide preheating window, good aging resistance and adaptability to table boards of various specifications.

Description

Low-temperature nylon powder material for selective laser sintering and preparation method thereof

Technical field

The invention relates to the technical field of polymer composite materials, in particular to a low temperature nylon powder material for selective laser sintering and a preparation method thereof.

Background technique

Additive manufacturing (commonly known as 3D printing, also known as rapid prototyping & manufacturing) technology is a new advanced manufacturing technology involving computer, control, machinery, materials and many other sciences. It breaks the traditional process of material deformation molding and removal molding. It uses a layer-by-layer manufacturing and superimposed additive molding method to theoretically produce any complex three-dimensional solid parts.

Selective Laser Sintering (SLS) technology is a current mainstream additive manufacturing technology. Polymer powder material is the earliest and most widely used SLS material. It melts or softens during laser sintering, crystallizes and densifies during cooling, and causes volume shrinkage, which affects the precision of the formed part. At present, non-crystalline polymer materials developed at home and abroad include polystyrene (PS), polycarbonate (PC), acrylonitrile-butadiene-styrene copolymer (ABS), etc., and the density of SLS molded parts is low. The mechanical properties are not high, and it needs to be post-treated to be used as functional parts with low mechanical properties. The semi-crystalline polymer material not only has a densified volume shrinkage similar to that of a non-crystalline material in the SLS process, but also a volume change caused by melt recrystallization causes a large volume shrinkage. Therefore, the warpage deformation caused by the volume shrinkage is large, the process is difficult to control, and research and development are difficult. However, its SLS molded parts have high density, good strength and toughness and can be directly used as functional parts. Therefore, the use of such materials for SLS manufacturing will have great potential for development. At present, crystalline polymer materials for SLS mainly include nylon (PA), polyethylene wax, and the like.

Nylon 12 (Polyamide 12, PA12) is a semi-crystalline thermoplastic material with a melting point of 170-180 ° C. It is easy to form and process, and has a wide molding temperature range. Nylon 12 has good flexibility, chemical stability, oil resistance and wear resistance. It is widely used in water meters and other commercial equipment such as optical fiber, cable sleeves, mechanical cams, automobiles, sliding mechanisms and bearings. The nylon 12 powder can be laser sintered to produce high-density, high-strength molded parts that can be directly used as functional parts. However, during the SLS forming process, the nylon 12 has a high preheating temperature and is prone to aging degradation; in addition, the preheating temperature window is narrow (1-2 ° C), and the molded part is easily warped and deformed. This makes the nylon 12SLS molding process complicated, difficult to promote, and can not be applied to domestic large-scale SLS equipment.

SLS molded nylon plastic features have the advantages of high strength, high speed and no post-treatment. Therefore, nylon powder material has become the main direction of SLS material development. However, the existing commercialized nylon powder has a high SLS preheating temperature and a narrow preheating temperature window, and has not yet been commercialized in China. The problems are as follows:

(1) The preheating temperature is too high (160-180 °C), which causes the overall temperature of the SLS equipment to rise accordingly. Lasers and their galvanometer scanning systems generally require operation at lower temperatures (room temperature). High temperature preheating is very detrimental to the stability of SLS equipment, and it is easy to cause galvanometer lasers. The scanning system has problems such as temperature drift.

(2) The preheating temperature window is narrow (1-2 °C), which requires the powder bed temperature of the SLS equipment to be uniform and precise temperature control. This not only greatly increases the cost of SLS equipment, but also makes it difficult to implement the technology. 3D Systems and EOS's direct laser-sintered nylon equipments are all small work surfaces, and laser sintering of nylon on large work surface equipment is still not possible. The SLS equipment sold by Huazhong University of Science and Technology Rapid Manufacturing Center in recent years is a large work surface. SLS device.

(3) The nylon powder is easily aged under high temperature, which causes the mechanical properties of the SLS parts to drop drastically, and the laser sintering performance deteriorates. In order to avoid aging, foreign countries have strict requirements on the atmosphere when laser-sintered nylon, all under the protection of N2 gas, and strictly control the oxygen content in the atmosphere. Even so, at least 30% of the new powder is required. The price of nylon powder is extremely high, and the large amount of powder can not be reused is a serious waste. It is difficult for domestic enterprises to accept such high operating costs, which makes SLS technology lose its competitive advantage in directly preparing plastic functional parts. The SLS equipment developed in China is operated under air atmosphere, so it can not meet the requirements of laser sintered nylon powder.

(4) The preheating time of the nylon powder before molding is long, and the cooling procedure after forming is also very strict, so that the molding cycle is long, and the utilization rate of the SLS equipment is lowered.

(5) Since the preheating temperature is close to the melting point of nylon, the crystal enthalpy of nylon is very large, and the cumulative effect of heat during forming is very obvious. The powder around the sintered body is easily melted or agglomerated, and the excess heat must be taken away by gas. And the laser power and preheating temperature all change with the change of the shape and structure of the sintered cross section, the operation is very complicated, the automation cannot be realized, and it is difficult to promote to production.

The patented technologies currently disclosed for selective laser sintering of nylon powder are:

1. A method for preparing a nylon powder for selective laser sintering - Application No.: 201010597529.8

2. Nylon powder material for laser sintering rapid prototyping products - application number: 02110361.5

3. A nylon composite powder material for selective laser sintering - application number: 201010239448.0

4. Selective laser sintering of nylon/aluminum powder composite powder material-application number: 201010251726.4

5. Method for preparing nylon coated metal powder material - application number: 200710051795.9

6. Method for preparing nylon coated ceramic powder material - application number: 200710051863.1

Can not meet the above requirements. For the above reasons, it is still very difficult to realize the commercialization of existing nylon powder on domestic equipment.

Summary of the invention

The object of the present invention is to provide a low-temperature nylon powder material for selective laser sintering with the advantages of low preheating temperature, wide preheating window, good anti-aging performance, and various specifications for the above-mentioned deficiencies in the prior art. The characteristics of the countertop.

Another object of the present invention is to provide a method for preparing a low temperature nylon powder material for selective laser sintering, which has the characteristics of high yield, good toughness, uniform particle size, and good sphericity.

The object of the invention is achieved by the following technical solution:

A low temperature nylon powder material for selective laser sintering consisting of the following raw materials by weight:

The invention utilizes twelve carbon dibasic acid, double-end amino polyethylene glycol and deuterated trifluoroacetic acid to synthesize a nylon soft segment polymer, and synthesizes a nylon elastomer with nylon to obtain high tensile strength and low temperature impact strength. , good flexibility, high elastic recovery rate; low glass transition temperature, can maintain the impact strength and flexibility without changing in the low temperature environment of -40 ~ 0 °C; small change in flexibility, high melting point, Vicat The softening temperature is high.

Further, a low temperature nylon powder material for selective laser sintering is composed of the following raw materials by weight:

Wherein, the antioxidant is composed of phenols or phosphites or thioesters. The invention adds a specific antioxidant, which can effectively slow down the aging progress of the material, and the material of the invention still has good impact strength and tensile strength after repeated laser sintering. The phenolic antioxidant is the antioxidant 1010 or the antioxidant 1076, the phosphite antioxidant is the antioxidant 3010, and the thioester antioxidant is the antioxidant DLTP.

Wherein the solvent consists of ethanol, methyl ethyl ketone, diethylene glycol, and water. The solvent of the invention combines an organic solvent and an inorganic solvent, and can effectively improve the fluidity and compatibility of the material during the synthesis reaction, and the overall performance of the material is more stable.

Wherein, the solvent contains 90-100 parts of ethanol, 5-15 parts of methyl ethyl ketone, 1-5 parts of diethylene glycol, 5-15 parts of water, and a specific mixing ratio of ethanol, methyl ethyl ketone, diethylene glycol and water can further improve the material. Mixing uniformity and stability.

Wherein, the plasticizer is a mixture of one or more of hexane, glycerin, paraben, and sulfonamide. The invention combines the plasticizer to enhance the bending strength of the material and improve the mechanical properties of the material.

Wherein, the nucleating agent is any one of silica, colloidal graphite, lithium fluoride, boron nitride, and aluminum borate. The addition of the nucleating agent facilitates the nucleation reaction of various components and the mixing of materials, and improves the stability of the material.

A method for preparing a low temperature nylon powder material for selective laser sintering, comprising the following preparation steps:

Step 1. Mix the dodecane dibasic acid and the nylon 12 particles into the reaction vessel uniformly, add the double-end amino polyethylene glycol and the deuterated trifluoroacetic acid to the reaction vessel, seal, vacuum, and charge the carbon dioxide. The initial pressure of the autoclave was made 0.1-0.3 MPa.

Step 2: Heating, gradually increase the temperature of the reaction vessel to 170-190 ° C, start stirring, continue to raise the temperature to 190-210 ° C, open the exhaust valve, and reduce the pressure in the autoclave to 1.3-1.5 MPa for 0.4-0.6 hours. Slow and uniform pressure reduction, the pressure in the reactor is reduced to normal pressure within 1.8-2.2 hours, maintained at normal pressure for 0.4-0.7 hours, stirring is stopped, the product is taken out into a cold water tank, and finally dried to obtain a product.

Step 3: Put the above products together with an antioxidant, a solvent, a nucleating agent, a plasticizer and a silane coupling agent into the reaction vessel, close the kettle lid, vacuum the reaction vessel, and protect with a nitrogen gas replacement. The reactor was slowly warmed to 150-190 ° C and incubated for 2-3 hours.

Step 4: Turn on the stirring to lower the temperature of the kettle body to room temperature, take out the material, dry it in the air for 10-12 hours, add the displacer to the powder for ball milling for 3-4 hours, and then put the ball milled powder into the vacuum oven. After drying for 46-48 hours, a powder having good sphericity and fluidity can be obtained.

Wherein the displacer is a mixture of one or both of acetone or methanol and water, preferably, the acetone in the displacer: methanol = 2:3:8.

More specifically, a method for preparing a low temperature nylon powder material for selective laser sintering comprises the following preparation steps:

Step 1. Mix the dodecane dibasic acid and the nylon 12 particles into the reaction vessel uniformly, add the double-end amino polyethylene glycol and the deuterated trifluoroacetic acid to the reaction vessel, seal, vacuum, and charge the carbon dioxide. The initial pressure of the reactor was adjusted to 0.2 MPa.

Step 2: Heating, gradually increase the temperature of the reactor to 180 ° C, start stirring, continue to raise the temperature to 200 ° C, open the exhaust valve, reduce the pressure in the kettle to 1.4 MPa, maintain a slow and uniform pressure drop for 0.5 hours, and make the reaction vessel The pressure was lowered to normal pressure within 2 hours, maintained at normal pressure for 0.5 hour, stirring was stopped, the product was taken out into a cold water tank, and finally dried to obtain a product.

Step 3: The above product and an antioxidant, a solvent, a nucleating agent, a plasticizer and a silane coupling agent are closed, and the autoclave is vacuum-treated, and nitrogen gas is introduced and replaced by nitrogen for 3 times. Protection, the reactor was slowly warmed to 150-190 ° C and incubated for 2-3 hours.

Step 4: Turn on the stirring to lower the temperature of the kettle body to room temperature, take out the material, dry it in the air for 10-12 hours, add the displacer to the powder for ball milling for 4 hours, and then dry the ball milled powder into a vacuum oven. After drying for 48 hours, a powder having good sphericity and fluidity can be obtained.

The invention has the beneficial effects of the present invention, a low temperature nylon powder material for selective laser sintering, a segmented block nylon copolymer having a soft segment, that is, a nylon elastomer, for selective laser sintering, the present invention The material has the following characteristics: high tensile strength and low-temperature impact strength, good flexibility, high elastic recovery rate, low glass transition temperature, and can maintain impact strength and flexibility at a low temperature of -40 to 0 °C. No change; the change in flexibility is small, the melting point is high, and the Vicat softening temperature is high. Therefore, it is suitable for use at high temperatures, and the nylon elastomer of the present invention can maintain good tensile properties even under high temperature conditions in which other types of thermoplastic elastomers have not been tested. Specifically, the present invention also has the following advantages:

1. Preheating temperature: has a lower preheating temperature (120-150 ° C) and a wider preheating temperature window (20-40 ° C), greatly increasing the recycling rate of the powder, for SLS equipment Low accuracy requirements can reduce the cost of SLS equipment and maintain the stability of SLS equipment.

2. Anti-aging: It has strong anti-oxidation, which greatly increases the recycling rate of powder, reduces production cost and improves production efficiency.

3. High toughness.

4. Uniform particle size and good sphericity.

Another advantageous effect of the present invention is that the method has prepared a segmented block nylon copolymer having a soft segment, that is, a nylon elastomer, which is used for selective laser sintering, has high productivity, and has excellent comprehensive performance of nylon materials, and is suitable for Existing countertop equipment of various sizes and sizes.

detailed description

In order to facilitate the understanding of those skilled in the art, the present invention will be further described in conjunction with the embodiments, which are not intended to limit the invention.

Example 1

A method for preparing a low temperature nylon powder material for selective laser sintering: comprising the following preparation steps:

Step 3: The above product and an antioxidant, a solvent, a nucleating agent, a plasticizer and a silane coupling agent are closed, and the autoclave is vacuum-treated, and nitrogen gas is introduced and replaced by nitrogen for 3 times. Protection, the reactor was slowly warmed to 150 ° C and incubated for 3 hours.

Step 4: Turn on the stirring to lower the temperature of the kettle body to room temperature, take out the material, dry it in the air for 10 hours, then add the displacer to the powder for ball milling for 4 hours, then put the ball milled powder into a vacuum oven to dry 48 In the hour, a powder having good sphericity and fluidity can be obtained.

The weight fraction of each component in this embodiment is:

Example 2

Step 1. Mix the dodecane dibasic acid and the nylon 12 particles into the reaction vessel uniformly, add the double-end amino polyethylene glycol and the deuterated trifluoroacetic acid to the reaction vessel, seal, vacuum, and charge the carbon dioxide. The initial pressure of the reactor was set to 0.3 MPa.

Step 2: Heating, gradually increase the temperature of the reaction vessel to 190 ° C, start stirring, continue to raise the temperature to 210 ° C, open the exhaust valve, reduce the pressure in the autoclave to 1.3 MPa, maintain a slow and even pressure drop of 0.4 hours, and make the reaction vessel The pressure was lowered to normal pressure in 1.8 hours, maintained at normal pressure for 0.7 hours, stirring was stopped, the product was taken out into a cold water tank, and finally dried to obtain a product.

Step 3: The above product and an antioxidant, a solvent, a nucleating agent, a plasticizer and a silane coupling agent are closed, and the autoclave is vacuum-treated, and nitrogen gas is introduced and replaced by nitrogen for 3 times. Protection, the reactor was slowly warmed to 150 ° C and incubated for 2 hours.

The weight fraction of each component in this embodiment is:

Example 3

Step 1. Mix the dodecane dibasic acid and the nylon 12 particles into the reaction vessel uniformly, add the double-end amino polyethylene glycol and the deuterated trifluoroacetic acid to the reaction vessel, seal, vacuum, and charge the carbon dioxide. The initial pressure of the autoclave was made 0.1 MPa.

Step 2: Heating, gradually increase the temperature of the reaction vessel to 170 ° C, start stirring, continue to raise the temperature to 190 ° C, open the exhaust valve, reduce the pressure in the autoclave to 1.5 MPa, and maintain a slow and uniform pressure drop for 0.6 hours. The pressure was lowered to normal pressure in 2.2 hours, maintained at normal pressure for 0.4 hours, stirring was stopped, the product was taken out into a cold water tank, and finally dried to obtain a product.

Step 3: The above product and an antioxidant, a solvent, a nucleating agent, a plasticizer and a silane coupling agent are closed, and the autoclave is vacuum-treated, and nitrogen gas is introduced and replaced by nitrogen for 3 times. Protection, the reactor was slowly warmed to 190 ° C and incubated for 2 hours.

Step 4: Turn on the stirring to lower the temperature of the kettle body to room temperature, take out the material, dry it in the air for 12 hours, then add the displacer to the powder for ball milling for 3 hours, and then put the ball milled powder into a vacuum oven to dry. In the hour, a powder having good sphericity and fluidity can be obtained.

The weight fraction of each component in this embodiment is:

Example 4

Step 2: Heating, gradually increase the temperature of the reaction vessel to 175 ° C, start stirring, continue to raise the temperature to 205 ° C, open the exhaust valve, reduce the pressure in the autoclave to 1.4 MPa, maintain a slow and uniform pressure drop for 0.5 hours, and make the reaction vessel The pressure was lowered to normal pressure within 2 hours, maintained at normal pressure for 0.6 hours, stirring was stopped, the product was taken out into a cold water tank, and finally dried to obtain a product.

Step 3: The above product and an antioxidant, a solvent, a nucleating agent, a plasticizer and a silane coupling agent are closed, and the autoclave is vacuum-treated, and nitrogen gas is introduced and replaced by nitrogen for 3 times. Protection, the reactor was slowly warmed to 170 ° C and held for 2.5 hours. Step 4: Turn on the stirring to reduce the temperature of the kettle body to room temperature, take out the material, dry it in the air for 12 hours, then add the displacer to the powder for ball milling for 3 hours, then put the ball milled powder into a vacuum oven to dry 48 In the hour, a powder having good sphericity and fluidity can be obtained.

The weight fraction of each component in this embodiment is:

Performance test 1:

The low temperature nylon powder material prepared by the present invention is subjected to a sintering test on equipment of different mesa sizes, and the following experimental data is obtained:

设备台面尺寸/mmEquipment table size / mm	320×320320×320	400×400400×400	500×500500×500
最低预热温度/℃Minimum preheating temperature / °C	123123	128128	135135
结块温度/℃Agglomeration temperature / °C	160160	160160	160160
预热温度窗口/℃Preheating temperature window / °C	3737	3232	2525

The above table describes the preheating temperature and the agglomeration temperature of the nylon elastomer on different sizes of the countertop. The nylon material of the present invention is also applicable to the workbench of either the large countertop or the small countertop, the preheating temperature is low, and the preheating window is The width is wide.

Performance Test 2:

The pure PA12 and the low temperature nylon powder material of the present invention were sintered into a sample on a SLS apparatus and tested, and the following experimental data were obtained:

According to the above table, the density, tensile strength, flexural strength and flexural modulus of the sintered sample of the low-temperature nylon powder material of the present invention are significantly lower than that of the pure nylon 12SLS sample, but the impact strength is increased, and the present invention Nylon powder has a significant toughening effect on the overall part.

Performance Test 3:

The low temperature nylon powder material of the present invention was subjected to three processing tests, and the test results were as follows:

As can be seen from the above table, the nylon powder of the present invention maintains good mechanical properties after three times of laser sintering.

The above-described embodiments are a preferred embodiment of the present invention, and the present invention can be implemented in other ways, and any obvious alternatives are within the scope of the present invention without departing from the inventive concept.

Claims

A low temperature nylon powder material for selective laser sintering, characterized by: consisting of the following raw materials by weight:
A low-temperature nylon powder material for selective laser sintering according to claim 1, which is composed of the following raw materials by weight:
A low temperature nylon powder material for selective laser sintering according to claim 1, wherein said antioxidant is composed of phenols and phosphites or phenols and thioesters.
A low temperature nylon powder material for selective laser sintering according to claim 1, wherein the solvent consists of ethanol, methyl ethyl ketone, diethylene glycol, and water.
A low-temperature nylon powder material for selective laser sintering according to claim 4, wherein: 90-100 parts of ethanol in the solvent, 5-15 parts of methyl ethyl ketone, and 1-5 parts of diethylene glycol, 5-15 parts of water.
The low temperature nylon powder material for selective laser sintering according to claim 1, wherein the plasticizer is one of hexanediol, glycerin, paraben, and sulfonamide. Or a mixture of multiples.
The low temperature nylon powder material for selective laser sintering according to claim 1, wherein the nucleating agent is silica, colloidal graphite, lithium fluoride, boron nitride or aluminum borate. Any one.
A method for preparing a low temperature nylon powder material for selective laser sintering according to any one of claims 1 to 7, which comprises the following preparation steps:

Step 1. Mix the dodecane dibasic acid and the nylon 12 particles into the reaction vessel uniformly, add the double-end amino polyethylene glycol and the deuterated trifluoroacetic acid to the reaction vessel, seal, vacuum, and charge the carbon dioxide. And the initial pressure of the reactor is 0.1-0.3 MPa;

Step 2: Heating, gradually increase the temperature of the reaction vessel to 170-190 ° C, start stirring, continue to raise the temperature to 190-210 ° C, open the exhaust valve, and reduce the pressure in the autoclave to 1.3-1.5 MPa for 0.4-0.6 hours. Slow and uniform pressure reduction, the pressure in the reactor is reduced to normal pressure within 1.8-2.2 hours, 0.4-0.7 hours under normal pressure, stirring is stopped, the product is taken out from the reactor into a cold water tank, and finally dried. Obtaining a product;

Step 3: Put the above products together with an antioxidant, a solvent, a nucleating agent, a plasticizer and a silane coupling agent into the reaction vessel, close the kettle lid, vacuum the reaction vessel, and protect with a nitrogen gas replacement. , the reactor is slowly heated to 150-190 ° C, and incubated for 2-3 hours;

Step 4: Turn on the stirring to lower the temperature of the kettle body to room temperature, take out the material, dry it in the air for 10-12 hours, add the displacer to the powder, perform ball milling for 3-4 hours, and then put the ball milled powder into the vacuum. Drying in an oven for 46-48 hours gives a powder product.
A method of preparing a low temperature nylon powder material for selective laser sintering according to claim 8, wherein the displacer is a mixture of one or both of acetone or methanol and water.
A method for preparing a low temperature nylon powder material for selective laser sintering according to claim 8, comprising the following steps of preparing:

Step 1. Mix the dodecane dibasic acid and the nylon 12 particles into the reaction vessel uniformly, add the double-end amino polyethylene glycol and the deuterated trifluoroacetic acid to the reaction vessel, seal, vacuum, and charge the carbon dioxide. And the initial pressure of the reactor is 0.2 MPa;

Step 2: Heating, gradually increase the temperature of the reaction vessel to 180 ° C, start stirring, continue to raise the temperature to 200 ° C, open the exhaust valve, reduce the pressure in the autoclave to 1.4 MPa, and after 0.5 hours, continue to slowly and evenly reduce the pressure, so that The pressure in the reactor was reduced to normal pressure within 2 hours, maintained at normal pressure for 0.5 hours, stirring was stopped, the product was taken out into a cold water tank, and finally dried to obtain a product;

Step 3: The above product and the remaining reactant antioxidant, solvent, nucleating agent, plasticizer, silane coupling agent are put into the reaction kettle, the kettle lid is closed, the reaction kettle is vacuumed, and nitrogen gas is introduced. And the nitrogen is replaced by nitrogen for 3 times for protection, the reactor is slowly heated to 150-190 ° C, and incubated for 2-3 hours;

Step 4: Turn on the stirring to lower the temperature of the kettle body to room temperature, take out the material, dry it in the air for 10-12 hours, add the displacer to the powder for ball milling for 4 hours, and then dry the ball milled powder into a vacuum oven. After 48 hours of drying, a powder product was obtained.