GB2035886A - A mould suitable for moulding non-polar expanded plastics material - Google Patents
A mould suitable for moulding non-polar expanded plastics material Download PDFInfo
- Publication number
- GB2035886A GB2035886A GB7938310A GB7938310A GB2035886A GB 2035886 A GB2035886 A GB 2035886A GB 7938310 A GB7938310 A GB 7938310A GB 7938310 A GB7938310 A GB 7938310A GB 2035886 A GB2035886 A GB 2035886A
- Authority
- GB
- United Kingdom
- Prior art keywords
- mould
- expanded
- moulding
- mould cavity
- plastics material
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 239000000463 material Substances 0.000 title claims abstract description 33
- 239000004033 plastic Substances 0.000 title claims abstract description 27
- 229920003023 plastic Polymers 0.000 title claims abstract description 27
- 238000000465 moulding Methods 0.000 title claims abstract description 15
- 239000007788 liquid Substances 0.000 claims abstract description 14
- 230000005855 radiation Effects 0.000 claims abstract description 12
- 239000011148 porous material Substances 0.000 claims abstract description 10
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 6
- 239000011324 bead Substances 0.000 claims abstract description 6
- 235000012211 aluminium silicate Nutrition 0.000 claims abstract description 4
- 239000000919 ceramic Substances 0.000 claims abstract description 4
- 239000005995 Aluminium silicate Substances 0.000 claims abstract description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 3
- 239000004927 clay Substances 0.000 claims abstract description 3
- 229910052570 clay Inorganic materials 0.000 claims abstract description 3
- NLYAJNPCOHFWQQ-UHFFFAOYSA-N kaolin Chemical compound O.O.O=[Al]O[Si](=O)O[Si](=O)O[Al]=O NLYAJNPCOHFWQQ-UHFFFAOYSA-N 0.000 claims abstract description 3
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 238000010521 absorption reaction Methods 0.000 claims description 4
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 238000003825 pressing Methods 0.000 claims description 3
- -1 faience Substances 0.000 abstract description 6
- 229920001296 polysiloxane Polymers 0.000 abstract description 3
- 239000004794 expanded polystyrene Substances 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 239000004698 Polyethylene Substances 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920002635 polyurethane Polymers 0.000 description 2
- 239000004814 polyurethane Substances 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 239000004115 Sodium Silicate Substances 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- 230000002745 absorbent Effects 0.000 description 1
- 239000002250 absorbent Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 description 1
- 229910002113 barium titanate Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000002984 plastic foam Substances 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 229910052911 sodium silicate Inorganic materials 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
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
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
- B29C33/3814—Porous moulds
-
- 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
- B29C44/00—Shaping by internal pressure generated in the material, e.g. swelling or foaming ; Producing porous or cellular expanded plastics articles
- B29C44/34—Auxiliary operations
- B29C44/3415—Heating or cooling
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2909/00—Use of inorganic materials not provided for in groups B29K2803/00 - B29K2807/00, as mould material
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Casting Or Compression Moulding Of Plastics Or The Like (AREA)
- Molding Of Porous Articles (AREA)
Abstract
A mould suitable for moulding non-polar expanded plastics material is constructed wholly, body 1 and mould lining 2, from a material having a low or zero loss angle, in which the mould lining 2 is made from a porous material, capable of absorbing liquids, the surface 3 of the mould lining 2 adjacent the body 1 of the mould being made impermeable. e.g. by the application of silicones. The porous material used for the mould lining 2 may be a ceramic, faience, silica, alumina, clay or kaolin. Pre- expanded beads of plastic material 5 are introduced into the mould and are subjected to UHF radiation. <IMAGE>
Description
SPECIFICATION
A mould suitable for moulding non-polar expanded plastics material, a process for using such a mould and the products thereof
The present invention relates to a mould suitable for moulding non-polar expanded plastics material such as, for example, expanded polystyrene, expanded polyethylene,. or expanded polyurethane, to a process for using such a mould and to the products thereof.
The development of plastics materials during the last decades has been overwhelming.
Their rate of growth is much greater than that of practically all other industrial products. This is particularly true for expanded plastics materials or plastic foam, which, due to their specific mechanical and thermal properties, have found very wide uses in, for example, the construction of packing and refrigeration industries. Any progress, any improvement in the manufacture of expanded plastics materials has accordingly a considerable direct economic influence in very numerous industrial fields.
Known or proposed processes for moulding expanded plastics materials may be classed in several categories:
(a) those which use direct injection of steam into the mould.
(b) those which use mould cavities having electrically conducting surfaces;
(c) those which use induction circuits and metal mould impressions presenting eddy current losses;
(d) those which use high-frequency fields for heating and softening the plastics material;
(e) those which use ultra-high frequencies (UHF); such processes are particularly advantageous since they do not require any capacitive circuit, allow the use of low voltages and ensure a great homogeneity of the moulded expanded plastics materials obtained thereby.
Thus, French Patent No 2 298 571 and
U.S. Patent No. 4 173 608 of the present
Applicants describe a process for manufacturing expanded non-polar plastics material by means of ultra-high frequency radiation in a resonant cavity and U.S. Patent Application
Serial Number 842 314, also in the name of the present Applicants, describes a mould of which only the mould cavity is made from a material having high dielectric losses, absorbing the UHF radiation.
The technology for moulding expanded plastics materials by means of the UHF process using moulds made from non-absorbent non-polar materials but whose mould cavity alone absorbs the UHF radiation, though it has caused undeniable progress to be made in the expanded plastics material industry, still presents however a number of dis-advantages, which are principally the following:
The need to have mould cavities having precise electrical characteristics (and particularly the tangent 8) requiring the incorporation in the mould cavity of additives possessing loss factors linear with the temperature and/or cancelling out for a certain temperature.These additives (for example carbon, titanium oxide, barium titanate, etc.) are often costly, the preparation of such mould cavities always difficult, and the mechanical characteristics of such mould cavities are sometimes unsatisfactory.
There is thus a need for an improved mould suitable for moulding non-polar expanded plastics material.
According to the present invention there is provided a mould suitable for moulding nonpolar expanded plastics material, which is constructed wholly, body and mould cavity, from a material having a low or zero loss angle, in which the mould cavity is made from a porous material capable of absorbing liquids and whose capacity of absorption is in the range of from 0.01 to 1 ml per second and per cm2 of surface for a polar liquid whose viscosity is close to that of water, the surface of the mould cavity adjacent the body of the mould being made impermeable. Such a mould, while ensuring an excellent gradient and an excellent distribution of the temperature, is simple in design, requires no spectral additive which absorbs the UHF radiation and produces finished moulded work-pieces, perfectly dry, and accordingly time stable.Additionally such a mould may afford substantial economies of energy required to melt superficially the plastics material contained in the mould.
Though the mould cavity is transparent to
UHF radiation when dry, its porous nature causes it to absorb UHF radiation when a polar liquid (such as, for example, water) is added, for this liquid is immediately absorbed by the pores of said mould cavity.
Preferably the porous material used for manufacturing the mould cavity is a ceramic, faience, porous silica, alumina, clay or kaolin.
Several mould cavities may be assembled together so as to provide a mould having a large area.
Advantageously the porous material forming the mould cavity possesses an absorption capacity between 0.1 and 1 ml per second per cm2 of surface, for a polar liquid whose viscosity is close to that of water.
The mould cavity may be prepared by pressing, pouring of slip or the like.
Preferably the porous surface of the mould cavity is made impermeable over definite delimited areas.
According to another aspect of the present invention there is provided a process for moulding expanded plastic materials, such as, for example, expanded polystyrene, expanded polyethylene or expanded polyurethane by means of a mould as hereinbefore described, in which firstly an appropriate amount of polar liquid is distributed in the mould cavity, the mould is closed as soon as the polar liquid has been absorbed, pre-expanded beads of plastics material are introduced and the whole is subjected to UHF radiation.
For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying single figure drawing which shows in section part of a mould according to the present invention.
Referring now to the accompanying drawing, a mould of the invention is shown, which is suitable for moulding non-polar plastic material. This mould has a surface of separation 3 between a mould cavity 2 and a body 1 of the mould which surface is made impermeable, for example, by application of silicones. The vapour of the polar liquid such as, for example water, absorbed by mould cavity 2, escapes through pores 4 towards plastic beads 5 situated between the male and female parts of mould cavity 2 in order to weld them together. Not only the body 1 but also the mould cavity 2 are made from material substantially transparent to UHF radiation.
The loss angle of the mould of the invention is very low; tg 8 < 1 .10-4 for the frequency f=2.45 GHz.
In order to obtain, for example, boxes made from expanded polystyrene with dimensions 10 x 5 x 5cm and a thickness of 0.5cm, one proceeds, for example, as follows : an appropriate mould is chosen in which the total thickness of the mould cavity is 1.5cm, the material of the mould cavity being made from white porous ceramic, having a capacity of absorption in the range of from 0.01 to 1 ml per second and per cm2 of surface, preferably 0.1 SmI of water per second and per cm2, (more preferably 0.1 ml per second and per cm2) the surface 3 of the mould cavity being made impermeable to silicones. 3g of water are introduced, which are immediately absorbed by the mould cavity then, after the mould has been closed, 6g of polystyrene beads are added by means of an injector provided for this purpose (not shown in the figure).Then the mould is subjected to UHF radiation in a resonant cavity for example (not shown in the figure) for 20 seconds. Since filling of the mould and striping require about 30 seconds, the whole cycle takes approximately 50 seconds. If, when the beads are welded, there remains some trace of water, this is immediately reabsorbed by the porous mould cavity, the expanded polystyrene box obtained remaining perfectly dry. The residual water in the finished product is always less than 3% (compared with 20 to 25% of humidity remaining for objects moulded by a conventional process). As soon as the water has disappeared from the pores 4 of the mould cavity 2, i.e. as soon as the mould cavity has become dry, the heating stops automatically. The resonant cavity and the press which are not shown in the accompanying drawing are, for example, those described in U.S. Patent No. 4 173 606 and U.S.
Patent Application Serial No. 842 314.
As the porous surface of the mould cavity 2 can be made impermeable over definite delimited areas it is possible under certain conditions to use directed steam jets, to "occult" certain parts of the surface of the mould cavity which, made non-porous, will not absorb polar liquid and will thus remain transparent to the UHF radiation during moulding.
A mould according to the present invention is of simple design, is robust and economical and allows, because of the different shapes which the mould cavities may assume, moulded objects of many desired sizes and shapes to be obtained.
The mould cavity may be preferred by pressing or pouring of slip. It is precisely the nature of the slip (nature of the clays and kaolins used, the possible addition of sodium carbonate and/or of sodium silicate), its fluidity and its ability to flow which allow any desired porosity and any desired shape of mould cavities to be mechanical rectified since these mould cavities may be mechanically rectified and assembled to obtain moulds of any shape and any size, accordingly, moulded objects of any shape and any size can be obtained.
Claims (9)
1. A mould suitable for moulding nonpolar expanded plastics material, which is constructed wholly, body and mould cavity, from a material having a low or zero loss angle, in which the mould cavity is made from a porous material capable of absorbing liquids and whose capacity of absorption is in the range of from 0.01 to 1 ml per second and per cm2 of surface for a polar liquid whose viscosity is close to that of water, the surface of the mould cavity adjacent the body of the mould being made impermeable.
2. A mould according to claim 1, in which the porous material used for manufacturing the mould cavity is a ceramic, faience, porous silica, alumina, clay or kaolin.
3. A mould according to claim 1 or claim 2, having several mould cavities assembled together so as to provide a mould having a large area.
4. A mould according to any one of claims 1 to 3, in which the mould cavity is prepared by pressing, pouring of slip or the like.
5. A mould according to any one of claims 1 to 4, in which the porous surface of the mould cavity is made impermeable over definite delimited areas.
6. A process for moulding expanded plas tics material by means of a mould according to any one of claims 1 to 5, in which firstly an appropriate amount of polar liquid is distributed in the mould cavity, the mould is closed as soon as the polar liquid has beeb absorbed, pre-expanded beads of plastics material are introduced and the whole is subjected to UHF radiation.
7. Objects made from expanded plastic materials obtained by means of moulds according to any one of claims 1 to 5 and using the process according to claim 6.
8. A mould suitable for moulding nonpolar expanded plastics material, substantially as hereinbefore described with reference to the accompanying drawing.
9. A process for moulding expanded plastics material by means of a mould according to any one of claims 1 to 5, substantially as hereinbefore described with reference to the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR7832338A FR2441474A1 (en) | 1978-11-16 | 1978-11-16 | IMPROVEMENTS IN MOLDS AND ESPECIALLY MOLDS FOR MOLDING EXPANDED PLASTICS |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2035886A true GB2035886A (en) | 1980-06-25 |
Family
ID=9214952
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7938310A Withdrawn GB2035886A (en) | 1978-11-16 | 1979-11-06 | A mould suitable for moulding non-polar expanded plastics material |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS5577541A (en) |
| BE (1) | BE879874A (en) |
| CH (1) | CH633217A5 (en) |
| DE (1) | DE2945690A1 (en) |
| ES (1) | ES486072A0 (en) |
| FR (1) | FR2441474A1 (en) |
| GB (1) | GB2035886A (en) |
| IT (1) | IT1125668B (en) |
| NL (1) | NL7908373A (en) |
| SE (1) | SE7909381L (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2489738A1 (en) * | 1980-09-11 | 1982-03-12 | Isobox Sa | NEW MOLDS DESIGNED FOR THE MANUFACTURE OF EXPANDED, NON-POLAR PLASTIC MATERIALS USING ULTRA-HIGH FREQUENCY RADIATION |
| JPS58124629A (en) * | 1982-01-20 | 1983-07-25 | Toyoda Gosei Co Ltd | Dielectric heat-vulcanizing method |
| JPS5948113A (en) * | 1982-09-13 | 1984-03-19 | Nippon Kobunshi Kagaku Kk | Mold for high-frequency forming |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1508963A (en) * | 1962-04-17 | 1968-03-25 | ||
| US3289253A (en) * | 1964-01-22 | 1966-12-06 | Robert B Buonaiuto | Molds |
-
1978
- 1978-11-16 FR FR7832338A patent/FR2441474A1/en active Granted
-
1979
- 1979-11-06 GB GB7938310A patent/GB2035886A/en not_active Withdrawn
- 1979-11-07 BE BE1/9592A patent/BE879874A/en not_active IP Right Cessation
- 1979-11-12 IT IT27213/79A patent/IT1125668B/en active
- 1979-11-13 DE DE19792945690 patent/DE2945690A1/en not_active Withdrawn
- 1979-11-14 CH CH1016579A patent/CH633217A5/en not_active IP Right Cessation
- 1979-11-14 SE SE7909381A patent/SE7909381L/en unknown
- 1979-11-15 NL NL7908373A patent/NL7908373A/en not_active Application Discontinuation
- 1979-11-16 ES ES486072A patent/ES486072A0/en active Granted
- 1979-11-16 JP JP14941279A patent/JPS5577541A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| IT7927213A0 (en) | 1979-11-12 |
| FR2441474A1 (en) | 1980-06-13 |
| ES8100956A1 (en) | 1980-12-01 |
| CH633217A5 (en) | 1982-11-30 |
| BE879874A (en) | 1980-05-07 |
| ES486072A0 (en) | 1980-12-01 |
| DE2945690A1 (en) | 1980-05-29 |
| NL7908373A (en) | 1980-05-20 |
| IT1125668B (en) | 1986-05-14 |
| JPS5577541A (en) | 1980-06-11 |
| FR2441474B1 (en) | 1981-08-21 |
| SE7909381L (en) | 1980-05-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |