CN104385608A

CN104385608A - Polyamide powder for laser sintering and preparation method thereof

Info

Publication number: CN104385608A
Application number: CN201410519283.0A
Authority: CN
Inventors: 许小曙; 谭锐; 范小寒; 边宏
Original assignee: Hunan Farsoon High Tech Co Ltd
Current assignee: Hunan Farsoon High Tech Co Ltd
Priority date: 2014-09-30
Filing date: 2014-09-30
Publication date: 2015-03-04
Anticipated expiration: 2034-09-30
Also published as: CN104385608B

Abstract

The invention discloses a polyamide powder for laser sintering and a preparation method thereof. The preparation method is characterized by comprising rapidly cooling a polyamide solution to a temperature lower than the crystallization temperature of polyamide by 15-20 DEG C, then heating to the crystallization temperature of polyamide, and slowly cooling until polyamide powder is precipitated. The difference value of the initial melting temperature Tmo and the initial crystallization temperature Tco of polyamide powder prepared by employing the method is increased, the powder is narrow in particle size distribution and good in fluidity, and the polyamide powder is especially suitable for selective laser sintering.

Description

A kind of laser sintered polyamide powder and preparation method thereof

Technical field

The present invention relates to a kind of polyamide powder and preparation method thereof, the polyamide powder adopting the method to prepare is particularly useful for Selective Laser Sintering.

Background technology

Selective laser sintering is a kind of method manufacturing three-dimensional body by optionally fusing multiple powder bed, the method allows do not use tool processes and only according to the multiple overlapping layers of the 3-D view of object to be produced by laser sintering powder, need obtain 3D solid.The method mainly uses thermoplastic polymer.Patent US6136948 and WO9606881 is described in detail the method that this use polymer powder manufactures three-dimensional body.

Silon powder material may be used for Selective Laser Sintering to manufacture three-dimensional body.When carrying out selective laser sintering to polyamide powder, be often preheating to the temperature between its FCTA temprature (Tco) and incipient melting temperature (Tmo) to polyamide powder, this temperature section is called as " sintering window ".It is generally acknowledged that the sintering window of powder is large as far as possible, can avoid like this occurring distortion (or curling) phenomenon in sintering workpiece fabrication.In fact, after laser beam effect, the sample temperature at sintering position higher than the FCTA temprature Tco of powder, but adds the new colder powder of last layer the temperature at instance element place can be caused to be reduced to below Tco, and causes distortion.In addition, the domain size distribution of powder particle and mobile performance also have very important impact, centralized particle diameter to laser sintered, and the powder of good fluidity often can improve the effect of laser sintering process.

Polyamide powder generally adopts solvent precipitation to prepare, and is dissolved in suitable solvent by polyamide, is heated to uniform temperature and material is fully dissolved, then cool precipitation.The polyamide powder particle that sintering window is larger in order to obtain, domain size distribution is more concentrated, people obtain often through improvement sedimentation process.Patent CN1077582C mentions carrying out nucleating step higher than during polyamide precipitation temperature 2 to 20 DEG C, and then isothermal precipitation can obtain the polyamide powder of narrow domain size distribution and low-porosity; Patent WO20130901174 mentions by heat-treating in the temperature close to its fusing point thermoplastic, can improve sintering window; Patent CN102399371 refer to the polyamide precipitation powder that a kind of cool-down method by two stages obtains centralized particle diameter, and its first stage is cooled to higher than Precipitation Temperature 5 ~ 25 DEG C, and second stage is cooled to precipitation temperature again.These methods can improve some laser sintered performance of polyamide powder preferably, but still can not reach the effect making us being satisfied with very much.

Summary of the invention

Therefore the invention provides a kind of polyamide powder and preparation method thereof, fusing point Tm and the incipient melting temperature Tmo of the polyamide powder adopting the method to prepare obtain effective raising, Tmo and FCTA temprature Tco difference increase, the narrow diameter distribution of powder simultaneously, good fluidity, is especially applicable to selective laser sintering.

The present invention can realize by the following method: first dissolve polyamide, then by polyamide solution fast cooling to lower than its crystal Precipitation Temperature 15 ~ 20 DEG C, be warming up to the temperature that its crystal is separated out subsequently, then slow cooling is separated out to polyamide powder.

In solution fast cooling process described in the present invention, polymer segment mobility decrease fast in polyamide solution can be made, thus form crystal fast, control amount of crystals.Subsequently by solution warms to crystal Precipitation Temperature, the crystal that when can make fast cooling, crystallization is perfect not dissolves again, the crystal that crystallization is perfect then can become nucleus in slow cooling process, the high polymer making not formed crystal with it for nucleator grows, thus can the quantity of crystallization control thing and crystal size.Slow cooling process now ensure that the trend of crystallization, and the mobility of high polymer is comparatively strong simultaneously, and crystal fully can grow Sum fanction arrangement, and final precipitation obtains envisioned polyamide powder.

The rate of temperature fall of the quick cooling stage described in the present invention preferably adopts-1.5 DEG C/min ~-2.5 DEG C/min, and the rate of temperature fall in slow cooling stage preferably adopts-0.05 DEG C/min ~-0.15 DEG C/min.

With laser to polyamide powder selective sintering time, it is generally acknowledged that particle size is suitable, the particle diameter of narrow distribution range is ideal, preferable particle size mean value is that the powder of 40 ~ 60 μm is as agglomerated material, be less than 110 μm according to the particle diameter of polyamide powder of the present invention, mean particle size is 50 ~ 60 μm.

Polyamide powder incipient melting temperature (Tmo) according to the present invention improves 10 ~ 15 DEG C, and its FCTA temprature is substantially constant, and both differences (sintering window) increase.

In addition, angle of repose is the important indicator weighing powder flowbility.In the present invention, the flowing angle of repose of polyamide powder is effectively laser sintered lower than all carrying out when 40 °, and polyamide powder flowing angle of repose according to the present invention is 35 ° ~ 38 °.

Described polyamide can be selected from one or more in PA6, PA11, PA12, PA66, PA610, PA612, PA1010, PA1012, PA1212.

Cooling involved in the present invention can adopt the common methods such as cooling water temperature, and Precipitation process can adopt existing method to monitor.

After temperature-fall period of the present invention terminates, by system temperature fast cooling to room temperature, take out material and carry out Separation of Solid and Liquid, carry out drying process to pressed powder, this is the common method of this area dusty material post processing.

Polyamide powder precipitating preparation method simple process provided by the invention is feasible, and adopt polyamide powder centralized particle diameter prepared by the method, powder good sphericity, powder flowbility is good, and thermal property is excellent, is particularly suitable for selective laser sintering.

Accompanying drawing explanation

Fig. 1 be enforcement 1 with process modification before powder DSC comparison diagram;

Fig. 2 be enforcement 2 with process modification before powder DSC comparison diagram;

Fig. 3 be enforcement 3 with process modification before powder DSC comparison diagram;

Fig. 4 be enforcement 4 with process modification before powder DSC comparison diagram;

Fig. 5 be enforcement 5 with process modification before powder DSC comparison diagram.

Detailed description of the invention

In following examples, domain size distribution test measures according to DIN ISO 3310-1, and thermal performance test uses DSC(differential scanning calorimetry) to test, fluidity testing uses funnel method to measure according to DIN ISO 4324.

Embodiment 1

In 30L magnetic agitation reactor, add PA1212 pellet 3kg, ethanol 24kg, pass into high pure nitrogen to pressure 0.3MPa, open and stir; Make temperature in the kettle be increased to 145 DEG C with the speed of 1.5 DEG C/min, be incubated 1h at this temperature; After constant temperature terminates, adopt cooling water temperature, make temperature in the kettle be down to 90 DEG C with the cooldown rate of 2.0 DEG C/min, then heating makes to be warming up to 110 DEG C in still, then makes temperature in the kettle be down to 90 DEG C, to precipitating end with the speed of 0.15 DEG C/min; Strengthening cooling water flow makes temperature in the kettle be down to room temperature, takes out material, centrifugation, powder solid vacuum drying 8h.Gained pressed powder performance is in table 1 and Fig. 1.

This embodiment Sieving and casing is distributed as:

<32 μm: 0.6%(weight)

<38 μm: 1.8%(weight)

<45 μm: 3.9%(weight)

<53 μm: 22.1%(weight)

<63 μm: 55.5%(weight)

<75 μm: 75.8%(weight)

<90 μm: 92.5%(weight)

<106 μm: 98.6%(weight)

<110 μm: 100%(weight)

Powder flowbility is:

Angle of repose: 35.56 °

Collapse angle: 30.12 °

Declinate: 5.44 °

Powder hot property:

Incipient melting temperature Tmo:182.36 DEG C

Melting point onset Tm:190.06 DEG C

Embodiment 2

In 30L magnetic agitation reactor, add PA1212 pellet 3kg, ethanol 24kg, pass into high pure nitrogen to pressure 0.3MPa, open and stir; Make temperature in the kettle be increased to 145 DEG C with the speed of 1.5 DEG C/min, be incubated 1h at this temperature; After constant temperature terminates, adopt cooling water temperature, make temperature in the kettle be down to 90 DEG C with the speed of 2.0 DEG C/min, then heating makes to be warming up to 108 DEG C in still, then makes temperature in the kettle be down to 90 DEG C with the speed of 0.12 DEG C/min, precipitation terminates; Strengthening cooling water flow makes temperature in the kettle be down to room temperature, takes out material, centrifugation, powder solid vacuum drying 8h.Gained pressed powder performance is in table 1 and Fig. 2.

Embodiment 3

In 30L magnetic agitation reactor, add PA1212 pellet 3kg, ethanol 24kg, pass into high pure nitrogen to pressure 0.3MPa, open and stir; Make temperature in the kettle be increased to 145 DEG C with the speed of 1.5 DEG C/min, be incubated 1h at this temperature; After constant temperature terminates, adopt cooling water temperature, make temperature in the kettle be down to 90 DEG C with the speed of 2.0 DEG C/min, then heating makes to be warming up to 106 DEG C in still, then makes temperature in the kettle be down to 90 DEG C with the speed of 0.09 DEG C/min, precipitation terminates; Strengthening cooling water flow makes temperature in the kettle be down to room temperature, takes out material, centrifugation, powder solid vacuum drying 8h.Gained pressed powder performance is in table 1 and Fig. 3.

Embodiment 4

In 30L magnetic agitation reactor, add PA6 pellet 3kg, ethanol 24kg, pass into high pure nitrogen to pressure 0.3MPa, open and stir; Make temperature in the kettle be increased to 145 DEG C with the speed of 1.5 DEG C/min, be incubated 1h at this temperature; After constant temperature terminates, adopt cooling water temperature, make temperature in the kettle be down to 90 DEG C with the speed of 2.0 DEG C/min, then heating makes to be warming up to 106 DEG C in still, then makes temperature in the kettle be down to 90 DEG C with the speed of 0.03 DEG C/min, precipitation terminates; Strengthening cooling water flow makes temperature in the kettle be down to room temperature, takes out material, centrifugation, powder solid vacuum drying 8h.Gained pressed powder performance is in table 1 and Fig. 4.

Embodiment 5

In 30L magnetic agitation reactor, add PA6 pellet 3kg, ethanol 24kg, pass into high pure nitrogen to pressure 0.3MPa, open and stir; Make temperature in the kettle be increased to 145 DEG C with the speed of 1.5 DEG C/min, be incubated 1h at this temperature; After constant temperature terminates, adopt cooling water temperature, make temperature in the kettle be down to 90 DEG C with the speed of 2.0 DEG C/min, then heating makes to be warming up to 105 DEG C in still, then makes temperature in the kettle be down to 90 DEG C with the speed of 0.01 DEG C/min, precipitation terminates; Strengthening cooling water flow makes temperature in the kettle be down to room temperature, takes out material, centrifugation, powder solid vacuum drying 8h.Gained pressed powder performance is in table 1 and Fig. 5.

Table 1 embodiment 1 ~ 5 relevant parameter and powder property

Claims

1. a preparation method for laser sintered polyamide powder, is characterized in that, by polyamide solution fast cooling to lower than its crystal Precipitation Temperature 15 ~ 20 DEG C, be warming up to its crystal Precipitation Temperature subsequently, then slow cooling is separated out to polyamide powder.

2. method according to claim 1, the rate of temperature fall in described fast cooling stage is-1.5 DEG C/min ~-2.5 DEG C/min, the rate of temperature fall in described slow cooling stage is-0.05 DEG C/min ~-0.15 DEG C/min.

3. method according to claim 1 and 2, is characterized in that one or more that described polyamide can be selected from PA6, PA11, PA12, PA66, PA610, PA612, PA1010, PA1012, PA1212.

4. a laser sintered polyamide powder, is characterized in that, described polyamide powder is obtained by right 1 or 2 preparation method.

5. powder according to claim 4, is characterized in that, this polyamide powder incipient melting temperature improves 10 ~ 15 DEG C.

6. powder according to claim 4, it is characterized in that, the particle diameter of this polyamide powder is less than 110 μm, and mean particle size is 50 ~ 60 μm.

7. powder according to claim 4, it is characterized in that, the flowing angle of repose of this polyamide powder is 35 ° ~ 38 °.