JP2001513465A - Method and apparatus for thermoforming thermoplastic resin - Google Patents

Abstract

  (57) [Summary] The present invention relates to a method for thermoforming a thermoplastic resin. This method is based on a method in which the blank absorbs radiation at a specific time, with the thermoplastic resin absorbing radiation at a lower absorption rate than at longer wavelengths, or from a radiation source having a maximum intensity in the emission wavelength region transmitting the radiation at a higher transmission rate. A blank, preform or similar semi-finished product is heated to a moldable temperature so as to be exposed to a specific intensity of radiation, and then molded in a molding apparatus. The invention further relates to an apparatus for thermoforming a thermoplastic resin. This equipment includes a heating device for heating a blank, preform or similar semi-finished product to a temperature at which it can be molded, and a molding device for molding a heated blank, particularly a blow molding (stretch blow molding) device, a deep drawing device. Or a similar molding tool, wherein the heating device is configured so that the maximum intensity of the radiation source is within the emission wavelength range where the thermoplastic absorbs the incident radiation at a lower absorption rate than at longer wavelengths. A radiation source with adjusting means for adjusting the emission spectrum.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a method and an apparatus for molding a thermoplastic resin using the heating method described in Claims 1 and 12.

A crucial point in such a method and apparatus is that the blank must have a molding temperature profile suitable for the end product to be manufactured. If the end product has a complex shape, and especially if it is desired that the thickness of the end product be small, the above-mentioned temperature profile may be relatively complicated and / or the entire outer surface of the molding Over time. What is desired is to obtain a temperature that is approximately constant over the entire wall thickness, ie the "depth" of the blank. To achieve this, the molding process has previously been performed using hot air sources or infrared radiators, in particular, or often using heated dies that operate in several stages (eg, deep drawing stages, etc.). Was. In these procedures, heat tends to be applied substantially only to the surface of the blank, so that
To obtain a constant temperature inside the material, i.e. throughout the thickness of the material, it is necessary to rely on heat transfer by heat conduction inside the material. This time, in order to transfer the heat, it is necessary to carry out the heating relatively slowly, that is to say for so long that thermal equilibrium (over the entire thickness of the material) can occur. As a result, methods and apparatus as described above must be sophisticated, and are therefore prone to failure. In particular, it is obviously difficult to tune the system to obtain a suitable temperature profile over the entire spatial range of the blank.

[0003] It is an object of the present invention to further develop the above-described method and apparatus to provide simplified blank heating with improved temperature accuracy.

[0004] This object is achieved by a method according to claim 1 and an apparatus according to claim 12.

An important feature of the present invention is that the blank is heated with radiation of a specific intensity from a radiation source such that the energy for raising the temperature is absorbed not only on the outer surface of the blank but also inside the material. It is in. This means that the energy can actually penetrate into the material and therefore be absorbed near the surface of the blank before penetrating into it, as occurs with normal long wavelengths. This is achieved by adjusting the maximum intensity of the radiation source with respect to the absorption / transmission properties of the thermoplastic to be processed.

The maximum intensity is in the near-infrared region, especially 0.8 to 1.4 μm, preferably 0.8 to 1 μm.
. Preferably, it is in the region of 0 μm, ie the region whose wavelength is much shorter than the wavelength corresponding to the maximum intensity of a typical thermal radiation source. Heating is preferably performed fairly uniformly and quickly throughout the depth of the blank. This result is obtained with a radiator having at least a substantially continuous radiation spectrum. This is because when the maximum intensity is set to a short wavelength as proposed in the present invention, the intensity of the radiation increases in proportion to almost the fourth power of the temperature of the radiator.

After a specified time, in order to emit radiation so that the temperature profile established in the blank is suitable for the particular molding device, in an optical device, in particular a mirror, grating or radiation optics Preferably, radiation is applied to the blank using a similar device known in the art. That is to say, instead of adjusting or changing the radiation source, for example, as its energy supply means, it "tunes" the radiation actually reaching the blank according to requirements. The invention is advantageous in that the devices normally used for radiation optics can be used because the maximum intensity of the radiation is in the above-mentioned wavelength range.

[0008] The present invention provides that the flux density of the radiation incident on the object to be heated, ie the blank, is
When 0.5 MW / ^{m 2} greater than when particularly greater than 1 MW / ^{m 2,} is particularly advantageous.

[0009] The wavelength of maximum intensity is adjusted by adjusting the temperature of the heating element, in particular by regulation [ie
Measurement and Feedback of Related Radiation Dose]. In this regard, it is particularly preferred to adjust the filament temperature of the halogen lamp. For the purposes of the present invention, the filament temperature needs to be relatively high (to produce the required short wavelength), which is unusually high for halogen lamps, but it is still important to use It is preferable to take appropriate measures to ensure a long pot life of the halogen lamp used. In particular, special cooling devices are provided for this purpose in the (quartz) glass body region and the base region of the halogen lamp.

To set the intensity to a level suitable for the requirements, the distance between the radiation source and the blank is adjusted, preferably selectively or additively, and / or an optical filter such as a grating or gray filter A device and / or chopper device is used.

[0011] When using the method of the present invention for the production of polyethylene bottles in a particular industrial field, a preferred procedure is to have a specific heating or irradiation time of substantially less than 10 seconds, It is particularly preferred that: As a result, not only is the ordinary blank or preform heated uniformly, but also the production speed is increased.

The transfer of the preform to the forming tool, especially to the stretch blow molding mechanism, is preferably carried out immediately after exposing the preform to radiation, so that there is little period of non-irradiation. This ensures that the predetermined temperature profile along the preform body (especially by optics) cannot be altered by heat conduction inside the preform.

When producing deep drawn parts, it is preferred that the blank be formed substantially with a cold tool to eliminate significant heat transfer from the tool to the blank. This can be achieved, in particular, by shaping the blank in one deep drawing step. As a result, the predetermined temperature profile of the blank (especially by optical means) is substantially maintained. Furthermore, the possibility of adhesion between the blank and the deep drawing tool, which is particularly dangerous for deep drawing tools in which the blank is heated by the tool itself, is eliminated.

The apparatus of the present invention may be used in a wavelength range where the maximum intensity of the radiation source may be such that the incident radiation absorption of the thermoplastic material is lower or the incident radiation transmittance or permeability may be higher than at longer wavelengths. And a radiation source having an adjustment mechanism for adjusting an emission wavelength region of the radiation source. This radiation source has a maximum intensity in the near-infrared region, especially in the range of 0.
It is preferable that the thickness be in the range of 8 to 1.4 μm, particularly preferably 0.8 to 1.0 μm. The radiation penetrates to a depth corresponding to the thickness of the blank to be processed, and the blank is not only heated at its surface, but also initially (ie, without depending on thermal equilibrium due to heat conduction) inside it Enough to be heated
It must have low absorption or high transmission.

The radiation optics is preferably provided with mirrors, gratings or similar devices so that the blank can be heated with a temperature profile that is optimal for its forming.

In a halogen lamp, preferably provided as a radiation source, or a similar irradiation device with a heating element, the filament temperature is preferably regulated by a rectifier. The rectifier receives measured signals from sensors (pyrometers) designed to keep the filament temperature, and therefore the wavelength range where the maximum intensity of the radiation source is present, and according to the preset conditions described above, these signals are measured. Adjust the parameters.

Furthermore, the intensity is adjusted (by capturing the interference or comparing the set value with the measured value) so that a desired temperature profile is obtained within a predetermined irradiation time. This intensity setting can be done by changing the distance between the radiation source and the blank, and / or by means of optical filters, and / or by a chopper device. By such means, radiation is sent to the blank as a so-called "packet". With a chopper device, the chopper speed is selected such that the duration of the "packet" is very short for the entire time the blank is energized.

In the manufacture of PET bottles, the blank is placed in the source area for a time of 10 seconds or less, preferably 5 seconds or less, and then changes the established temperature profile (by optics). Prepare to remove from this region so that the temperature equilibrium does not occur. In addition or as an alternative, the entire apparatus for making PET bottles may be brought into stations (radiation sources, molding tools) in sufficient proximity to each other.
And a sufficiently fast conveyor to ensure that blanks and preforms remain exposed to heatable radiant energy for a substantial amount of time before being formed in stretch blow molding equipment. Absent. Such measures can also maintain the temperature profile established in the preform.

In the production of deep drawn parts (in relation to the deep drawing dies previously used)
If a deep drawing die having a relatively low temperature is used, and preferably only one deep drawing die is provided, the blank can be formed in one deep drawing step. Here again, the invention is advantageous in that the provision of the appropriate radiant energy does not substantially change the previously established temperature profile.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GE, GH, GM, HR, HU, ID, IL, IS, JP, KE, KG, KP , KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZW (71) Applicants: Industry Servis, Gesellschaft, Für, Innovation, Technology-Transfer, Und, consulting, fur, thermiche, projesuanlagen, embeher INDUSTRIESERVIS GES ELLSCHAFT FUNER INNO VATION TECHNOLOGIE- TRANSFER UND CONS Kkumyuru - Hui felt, Brooke Mueller, Shutora over Se, 27 (72) inventor Kai, car. E. Bale Brookmühlhuifert, Germany, Brookmüller, Strasse, 27 (72) Inventor Liner, Gauss Brookmüll-Heufeld, Germany, Brookmueller, Straße, 27F term (reference) 4F201 AA24 AH55 AR11 BA03 BC01 BC21 BN41 4F208 AA24 AH55 AR11 LA04 LB01 LH24

Claims (21)

[Claims] 1. A blank, preform or similar semi-finished product is heated to a moldable temperature and then molded using a molding device, in particular a blow molding (stretch blow molding) device, a deep drawing device or a similar molding tool. A method of thermoforming a thermoplastic resin, wherein the thermoplastic resin absorbs radiation at a lower absorptivity than at longer wavelengths or has a maximum intensity in an emission wavelength region that transmits radiation at a higher transmittance. A method for thermoforming a thermoplastic resin, comprising exposing a blank to radiation of a specific intensity from a radiation source for a specific time. 2. The method according to claim 1, wherein the maximum intensity is in the near infrared region. 3. The method according to claim 2, wherein the maximum intensity is at a wavelength between 0.8 and 1.4 μm, preferably between 0.8 and 1.0 μm. 4. The method according to claim 1, wherein the thermoplastic resin has a maximum intensity in a wavelength region having an absorption band of not more than 75%, preferably not more than 50%. . 5. A radiation, which is applied to the blank by means of an optical device, in particular a mirror, a grating or a similar radiation optical device, so that after a certain time has elapsed, a temperature profile is established in the blank that matches the forming device. 5. The method according to claim 1, wherein the radiation is carried out. 6. The method according to claim 1, wherein the wavelength of the maximum intensity is adjusted by an adjusting process, in particular by adjusting the temperature of the heating element, in particular the filament of the halogen lamp. Or the method of claim 1. 7. Adjusting the intensity by an adjustment process, in particular by adjusting the distance between the radiation source and the blank, and / or by an optical filter device such as a grating and / or a gray filter and / or by a chopper device. The method according to any one of claims 1 to 6, characterized in that: 8. The method for producing a PET bottle according to claim 1, wherein said specific time is substantially 10 seconds or less, preferably 5 seconds or less. The method according to any one of claims 1 to 4. 9. A method for forming a preform substantially immediately after exposure to radiation, without spending a considerable amount of time during which the preform is not irradiated in a forming tool, in particular a stretch blow molding apparatus. 9. The method according to item 8, wherein 10. The method of claim 1, wherein the blank is formed using a tool at substantially room temperature and there is no significant heat transfer from the tool to the blank. Item 10. The method according to any one of items 9 to 9. 11. The method according to claim 10, wherein the blank is formed in a single deep drawing step.
The method described in the section. 12. An apparatus for thermoforming a thermoplastic resin, comprising: a heating device for heating a blank, a preform or a similar semi-finished product to a moldable temperature; and a molding device for forming a heated blank. In particular, comprising a blow molding (stretch blow molding) device, a deep drawing device, or a similar forming tool, wherein the heating device absorbs incident radiation into the thermoplastic with a lower absorption rate than at longer wavelengths, or Thermoforming thermoplastics, characterized in that it comprises a radiation source with means for adjusting the emission spectrum of the radiation source so that the maximum intensity of the radiation source is within the emission wavelength range transmitted with high transmittance Equipment for doing. 13. The apparatus according to claim 12, wherein the radiation source is configured and adjusted such that its maximum intensity is in the near infrared region. 14. A radiation source whose maximum intensity is between 0.8 and 1.4 μm, preferably between 0.8 and 1.4 μm.
Apparatus according to claim 13, characterized in that it is constructed and tuned to be in the wavelength range of 0 µm. 15. The radiation source is constructed and adjusted such that its maximum intensity is in a wavelength range in which the thermoplastic resin has an absorption band of not more than 75%, preferably not more than 50%. An apparatus according to claim 12, wherein: 16. The radiation source is a halogen lamp or similar radiation device having a heating element, and the regulating means comprises a rectifier for regulating and regulating the temperature of the radiation device, in particular the filament of the halogen lamp. Apparatus according to any one of claims 12 to 15, wherein the apparatus comprises: 17. Adjusting the intensity of the energy applied to the blank, including a distance adjustment mechanism and / or an optical filter device such as a grating or gray filter and / or a chopper device to establish a specific distance between the radiation source and the blank. Apparatus according to any one of claims 12 to 16, characterized in that it comprises a strength adjusting device. 18. A PET, characterized in that the timing device is configured to apply radiation of a specific intensity to the blank for a specific time of substantially less than 10 seconds, preferably less than 5 seconds.
Apparatus according to claim 12 for producing bottles. 19. A molding tool, particularly a stretch blow molding apparatus, wherein the radiation source is formed such that the preform is molded substantially immediately after exposure to radiation without spending substantial time when the preform is not irradiated. In a production line that operates substantially continuously,
Apparatus according to claim 12, for producing PET bottles, characterized in that it is arranged substantially immediately before the molding apparatus. 20. The molding apparatus is substantially non-heated so that the blank can be molded with a tool at substantially normal temperature without heat transfer that would increase the temperature of the blank. Apparatus according to any one of claims 12 to 17 for producing deep drawn parts. 21. Apparatus according to claim 20, wherein a single deep drawing tool is provided.