Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
  • B29C71/02—Thermal after-treatment
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
  • B29C71/0063—After-treatment of articles without altering their shape; Apparatus therefor for changing crystallisation

Definitions

• the invention relates to a method for producing a plastic part, comprising heating a plastic mass to a mold temperature equal to or above a melting temperature, wherein the plastic mass is thermoformable from the melting temperature and subsequent
• the invention further relates to a device comprising a manufactured according to one of claims 1 to 29 plastic part.
• the conversion temperature which is lower than the melting temperature, as well as the retention of the molding on the conversion temperature for a defined conversion period, it allows the molecular and / or crystalline structure of the plastic after its formation changed to a molding, which partially significant improvements in the properties of the plastic part can be achieved.
• These improvements relate to both mechanical properties and resistance to chemical weathering as well as resistance to thermally induced degradation or degeneration of the molecular structure at high temperatures.
• hot forming is understood as meaning any transformation of plastic substance softened under the action of heat, in particular also master-molding methods, such as casting techniques.
• the adjustment of the temperature of the molding to conversion temperature is preferably carried out with air as a tempering medium, for example in a hot air oven.
• Further preferred tempering media are liquid metals, oil baths or particularly preferably salt baths with which the process time with respect to air may be reducible, in particular by 25%.
• liquid tempering the mold part is preferably immersed.
• the other process conditions correspond to those with air as tempering medium.
• the plastic composition is at least partially made of an at least partially crystalline thermoplastic, wherein In particular, aggregates such as fibers are present. Due to the partial crystallinity, the plastic composition is particularly well suited to carry out a conversion of the molecular structure according to the inventive method.
• the plastic mass consists essentially of a polyamide.
• a polyamide 66 is particularly preferred.
• it may also be a polyamide 6, a polyamide 46 or a polymer blend in which at least one component, in particular two components from the group of polyamide 6, polyamide 66 and polyamide 46 is.
• a corresponding improvement should be achievable by the process according to the invention, since polyamides are semicrystalline and have different crystalline phases and an amorphous phase.
• the plastic material may also be a polyethylene or a polypropylene. It may also be a polyamide 12, as it finds use in about hoses; In this case, a preparation according to the invention can lead to improved gas-tightness or blocking action in relation to the guided medium due to increased crystallinity. Furthermore, it can be a Polyoxymethylene act, in which the already tribologically favorable properties of this substance are further optimized by a further improvement of the crystallinity by the inventive method. Likewise, any other plastic is conceivable in which an improvement of the mechanical and / or chemical properties and / or stability at high temperatures can be achieved by a method according to the invention.
• the conversion temperature is not more than about 50 0 C below the melting temperature. More preferably, the conversion temperature is not more than 30 0 C, further preferably not more than about 15 C and more preferably not more than about 10 0 C below the melting temperature. It should be noted that, depending on the type of plastic in general, a particularly suitable conversion temperature is present, which is regularly below, but relatively close to the melting temperature. It has been found that not every high temperature leads to a successful treatment of the plastic. Rather, a treatment temperature that is too far away from the melting temperature, also no beneficial effect, but only lead to degeneration of the molded plastic part. For example, it is generally known to the person skilled in the art that polyamides in the temperature range from 160 ° C. to fast yellowish discolorations and correspondingly degenerate, ie become brittle and cracked. The opposite effects in a heat treatment just below the melting temperature of a polyamide molding were therefore not to be expected.
• the plastic mass before step c. of the process to an intermediate temperature, in particular room temperature, is cooled.
• the process step c can be carried out so that the conversion temperature is reached at a certain rate of a change in temperature. This takes into account the fact that in certain cases, a phase transformation of the plastic may be favored by the course of a change in temperature and not only by a constant temperature.
• the forming takes place in step b. in a casting process, in particular an injection molding process, whereby the process according to the invention can be connected to a customary series production.
• the adjustment of the conversion temperature in step c takes place while the plastic material is in a mold.
• other tools such as special ovens are avoided and a particularly fast process flow is possible, whereas increased effort is required by the possibly special design of the injection mold.
• a heating to the conversion temperature takes place immediately after the forming of the plastic mass and after a process-related cooling, wherein prior to heating still contains a considerable residual heat from the forming process in the plastic mass and thus serves to save energy.
• the reshaped plastic mass is used to set the conversion temperature in an oven, in particular a hot-air oven.
• an oven in particular a hot-air oven.
• the plastic parts can be introduced during the annealing in a suitable support form or holder.
• any other conventional type of heating can be selected, for example by infrared radiation or, depending on the suitability of the material by microwave irradiation.
• a protective gas atmosphere such as nitrogen or argon
• the conversion period is not less than about one minute. More preferably, the conversion period is not less than about 5 minutes, more preferably not less than about 30 minutes. More preferably, the period is not less than 100 minutes, more preferably about 120 minutes.
• an optimum of the material properties has resulted in the latter time range. In general, it depends on the type of plastic used, which conversion period is sufficient to achieve the improvement of the properties of the plastic.
• the conversion period is generally not more than about three hours. This ensures, on the one hand, that cost savings caused by the revaluation of low-grade plastics are not consumed again by energy consumption or other expense.
• the plastic composition comprises a portion of a crystallization accelerator, in particular glass fibers or mineral nanoparticles, which optionally serves as a nucleating agent.
• a crystallization accelerator in particular glass fibers or mineral nanoparticles, which optionally serves as a nucleating agent.
• a conversion of a crystalline phase with unfavorable properties into a crystalline phase with favorable properties at the conversion temperature can be quite preferred.
• the admixed crystallization accelerator serves. In process steps c. and / or d. Then the conversion takes place in a favorable crystalline phase by tempering.
• the object of the invention is achieved for a device by the features of claim 30, since in the device, a plastic part according to the invention is used and thus the device can be produced more cheaply than would be possible in the case of particularly high quality starting materials for the plastic part.
• the device is a heat exchanger for a motor vehicle.
• the plastic part is particularly preferred
• the plastic part may be a housing part of a coolant box of a main engine radiator for a motor vehicle.
• the plastic part may preferably be a housing part of an oil cooler, a part of an interior heating of a motor vehicle, a component of a thermostat, a component of a fuel heater, a conduit, in particular for guiding oil, coolant or air or a rotor of a fan.
• the plastic part may be a conduit, in particular a hose, in a refrigeration cycle of an air conditioning system, in particular of a motor vehicle.
• a plastic compound consists of the product Ultramid® PA66-GF30 (product code: A3HG6HRsw) from the manufacturer BASF AG. This is a glass-fiber-reinforced polyamide 66. This customary plastic mass is first heated to a casting temperature after any necessary pre-drying. The melting temperature of this plastic determined according to ISO 11357-1 / -3 is 260 0 C. The recommended Casting temperature, which is initially heated in the present process is about 290 0 C. The recommended temperature of the mold is about 85 0 C.
• the heated to its casting temperature polymer is first injected in a conventional manner at normal pressures in the preheated to 85 0 C mold, wherein the shape of the casting is a heat exchanger housing part, in particular a container part of a charge air cooler of a motor vehicle. Due to the normally high temperature differences between the mold and the injected plastic mass the so molded plastic part cools, at least in its edge regions usually quickly to temperatures somewhat above 100 0 C.. In particular, a temperature range of 240 - 250 0 C passed through relatively quickly, whereas the region at about 160 0 C is passed through more slowly.
• the formation of the ⁇ -phase of crystallites preferably takes place for polyamide 66, whereas in the latter temperature range of about 160 ° C., preference is given to the formation of ⁇ -crystallites. It is therefore to be expected that the solidified and cooled plastic part has a high proportion of ⁇ crystal phase and of amorphous, ie not crystallized, phase. The proportion of mechanically and chemically very stable ⁇ -phase in the plastic part is therefore relatively small. However, these are presumptions that represent only a scientifically not yet confirmed explanatory attempt for the favorable effects occurring in the course of the method according to the invention.
• the still warm plastic part is then immediately spent in a heating oven, in which it is heated to a temperature of 250 0 C.
• This temperature is referred to as the conversion temperature and is in the present example 10 ° C below the melting point of the plastic mass.
• the plastic part for a period of at least 5 minutes, present about 120 minutes, left. Subsequently, the plastic part is removed from the hot air oven and cooled without further measures to room temperature.
• the post-treated by annealing in the hot air oven casting has compared to the prior art non-treated casting, which is cooled immediately after leaving the mold to room temperature, significantly improved mechanical properties and resistance to chemical influences and temperature influences.
• the inventively post-treated plastic part of the glass fiber reinforced polyamide 66 at temperatures well above 200 0 C can be used.
• the temperature-induced degeneration of the material is improved compared to a non-treated plastic part of the same plastic mass many times over.
• the above plastic material shows improvements in material properties at conversion temperatures from about 30 0 C below the melting temperature, ie from about 230 0 C. Further approximation of the conversion temperature to the melting temperature than about 5- 10 0 C is not recommended, otherwise too strong softening and thus the molding undergoes an impermissibly large change in shape.
• the treated plastic part was subjected to a load test and compared with an untreated, but similarly injection molded part.
• the load consisted in the storage of the plastic parts in a - practically in practice so hardly occurring - 130 0 C hot water-glycol mixture (50:50, standard engine coolant) over 1000 hours.
• the breaking strength of the untreated plastic part had dropped to 18% of the initial value and that of the treated according to the invention to 34%.
• the value of the untreated part had fallen to 31% and that of the treated according to the invention to 55%. This results in approximately a doubling of the resistance to 130 0 C hot water-glycol mixture. In practice, this can be decisive as to whether a plastic part can be used, for example, for a cooler housing or not.
• the plastic composition is made by the company Ticona
• 66 has a melting point or softening point of about 260 0 C. Again, a tempering over a period of at least several leads
• the plastic composition consisted of a glass fiber-free polyamide 66, namely Ultramid® from BASF with the product designation "A3Ksw.” Again, a tempering at 10 0 C below the melting point over a period of 30 minutes and over a period of time 120 minutes to improve the material properties, and in addition a significant change in the crystal structure was confirmed by structural analysis measurements.
• the plastic mass of a glass fiber-free polyamide 6 Again, a tempering at 10 0 C below the melting point over a period of 30 minutes and over a period of 120 minutes to improve the material properties, in addition, a significant Change in crystal structure was confirmed by structural analysis.
• the plastic mass consisted of a polypropylene, namely "Stamylan P4935" of the
• material properties would be achieved by the method according to the invention by changes in the molecular or crystalline structure of the simple and inexpensive plastic, as otherwise under conventional manufacturing processes of plastic parts only by highly stabilized plastics, ie plastics with a particularly complex formulation of additives, are achieved can.

Landscapes

• Chemical & Material Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Extrusion Moulding Of Plastics Or The Like (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=36601216

Family Applications (1)

Country Status (6)

Families Citing this family (7)

Family Cites Families (7)

• 2006
  • 2006-03-21 BR BRPI0609596-8A patent/BRPI0609596A2/pt not_active Application Discontinuation
  • 2006-03-21 JP JP2008503407A patent/JP2008534320A/ja active Pending
  • 2006-03-21 CN CNA2006800105806A patent/CN101151143A/zh active Pending
  • 2006-03-21 EP EP06723599A patent/EP1907196A2/de not_active Withdrawn
  • 2006-03-21 US US11/887,432 patent/US20080281051A1/en not_active Abandoned
  • 2006-03-21 WO PCT/EP2006/002598 patent/WO2006103013A2/de not_active Ceased

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events