CA1135913A - Production process of lenses made of polymerizable synthetics resins - Google Patents
Production process of lenses made of polymerizable synthetics resinsInfo
- Publication number
- CA1135913A CA1135913A CA000327575A CA327575A CA1135913A CA 1135913 A CA1135913 A CA 1135913A CA 000327575 A CA000327575 A CA 000327575A CA 327575 A CA327575 A CA 327575A CA 1135913 A CA1135913 A CA 1135913A
- Authority
- CA
- Canada
- Prior art keywords
- polymerizable
- mold
- accordance
- monomer
- cavity
- 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.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00009—Production of simple or compound lenses
- B29D11/00413—Production of simple or compound lenses made by moulding between two mould parts which are not in direct contact with one another, e.g. comprising a seal between or on the edges
-
- 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
- B29C33/0038—Moulds or cores; Details thereof or accessories therefor with sealing means or the like
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
- G02B1/04—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of organic materials, e.g. plastics
- G02B1/041—Lenses
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
- B29L2031/76—Office equipment or accessories
- B29L2031/7602—Maps
Abstract
ABSTRACT OF THE DISCLOSURE:
Production process of lenses made of polymerizable synthetic resins. According to the production process lenses made of synthetic resins may be obtained through casting of a catalized monomer which is polymerized up to the hardening point by warming it within a mold formed from two or more glass lenses, assembled together by means of a perimetrical gasket and a spring. In the process the shrinkage of the polymer being formed is compensated through catalized monomer kept in presence of air outside of the mold, from where it may flow into the interior of the mold where is no air. According to the process it is possible to obtain transparent and practically colourless lenses made from polymer, showing outstanding physico-chemical characteristics and possessing a diameter almost equal to that of the glass lenses forming the mold.
Production process of lenses made of polymerizable synthetic resins. According to the production process lenses made of synthetic resins may be obtained through casting of a catalized monomer which is polymerized up to the hardening point by warming it within a mold formed from two or more glass lenses, assembled together by means of a perimetrical gasket and a spring. In the process the shrinkage of the polymer being formed is compensated through catalized monomer kept in presence of air outside of the mold, from where it may flow into the interior of the mold where is no air. According to the process it is possible to obtain transparent and practically colourless lenses made from polymer, showing outstanding physico-chemical characteristics and possessing a diameter almost equal to that of the glass lenses forming the mold.
Description
,r~ .
The presen-t invention refers to a production process oE lenses and optical means made of polyrnerizable synthetic resins, through a continuous compensation casting.
In the last decades the technological world has been paying attention to the research after molding methods based on the mold polymerization of one or more monomers, likely to produce solids provided with special characteristics.
The optical industry has been engaging in such a direction to produce lenses or ot;her optical means: in practice, the various technologies aim at overcoming the obstacles occur-ring during the polymerization process, such as:
- physico-chemical characteristics of the product, correlated to the theoretically optimal polymer, - physico-chemical characteristics of the product, correlated to the polymer obtained;
- shape of the product.
These technologies have been directed, in particular, towards the casting of thermohardening polymers, as the latter offer physico-chemical characteristics and other advantages better suited, when used as optical means, f.i. lenses, than the thermoplastic polymers. By now, entered into general use is the diethyleneglycol-bis-allyl-carbonate ~and its copolymers) ~-having the formula:
. ~CH2--CH2-0-CO--O-CH2-CH = CH2 "
~i ~ O\
;`! CH2--cH2--O-cO-O--cH2-cH = CH2 .
better known under the trade-mark CR-39. The latter with the addition of a catalyzer (or better said, of a free-radicals starterl, polymerizes to an homopolymer or to a copolymer.
The preferred starter is the isopropyl-dicarbonate-peroxide having the formula:
CH , CH~
CH3/ 3 ~ ;
~ ' , known as I.P.P.. The latter infacts, allows the polymerization to run at a lower temperature and wi.thin shorter cycles, when compared to the benzoyl-peroxide or to other peroxides, which also may be used. In practice the casting methods of a lens made of CR-39 or its copolymers, include the introduction o~
catalyzed monomer/s, in the fluid state, or prepolymerized up to the syrupy state, between two g].ass lenses, kept together by means of a spring, and kept at a given distance from each other, through a T section gasket. The gasket distancer may be shaped according to the curvature of both lenses, to secure tightness and separation, or to the same end it may become elastically deformed. The catalyzed monomer, added as a fluid in the molds thus formed, solidifies at the end of a thermic or radiating cycle, producing strong tridimensional shrinkings (14% in the case of the CR-39 homopolymer). Thus a further function of the spring is to contihuously squeeze the distancer of the lenses forming the mold, until the fluid reaches the intermediate gel state, to avoid the leakage of fluid monomer from the mold. On the other hand, after the gel phase has been reached, the pressure of the spring, shall straïn the thermoplastic or elastic distancer, to facilitate the adherence mould/polymer. Such a strain may be considered as a squeezing of the distancer or as an expansion of the gasket.
The mold/polymer adherence is required to avoid possible breakages of the polymer or of the mold, due to the strong tensions wh.ich occur when the polymer shrinks, and to avoid, at least on the usable surface of the polymer, air : infiltrations which, by hindering the polymerization, would cause irreparable damages to the product.
The lenses thus obtained, made of CR-39j or its copolymers, may present faulty perimeters, due to air bubbles.
Air leakages, even after the gel phase is ended, may cause air
The presen-t invention refers to a production process oE lenses and optical means made of polyrnerizable synthetic resins, through a continuous compensation casting.
In the last decades the technological world has been paying attention to the research after molding methods based on the mold polymerization of one or more monomers, likely to produce solids provided with special characteristics.
The optical industry has been engaging in such a direction to produce lenses or ot;her optical means: in practice, the various technologies aim at overcoming the obstacles occur-ring during the polymerization process, such as:
- physico-chemical characteristics of the product, correlated to the theoretically optimal polymer, - physico-chemical characteristics of the product, correlated to the polymer obtained;
- shape of the product.
These technologies have been directed, in particular, towards the casting of thermohardening polymers, as the latter offer physico-chemical characteristics and other advantages better suited, when used as optical means, f.i. lenses, than the thermoplastic polymers. By now, entered into general use is the diethyleneglycol-bis-allyl-carbonate ~and its copolymers) ~-having the formula:
. ~CH2--CH2-0-CO--O-CH2-CH = CH2 "
~i ~ O\
;`! CH2--cH2--O-cO-O--cH2-cH = CH2 .
better known under the trade-mark CR-39. The latter with the addition of a catalyzer (or better said, of a free-radicals starterl, polymerizes to an homopolymer or to a copolymer.
The preferred starter is the isopropyl-dicarbonate-peroxide having the formula:
CH , CH~
CH3/ 3 ~ ;
~ ' , known as I.P.P.. The latter infacts, allows the polymerization to run at a lower temperature and wi.thin shorter cycles, when compared to the benzoyl-peroxide or to other peroxides, which also may be used. In practice the casting methods of a lens made of CR-39 or its copolymers, include the introduction o~
catalyzed monomer/s, in the fluid state, or prepolymerized up to the syrupy state, between two g].ass lenses, kept together by means of a spring, and kept at a given distance from each other, through a T section gasket. The gasket distancer may be shaped according to the curvature of both lenses, to secure tightness and separation, or to the same end it may become elastically deformed. The catalyzed monomer, added as a fluid in the molds thus formed, solidifies at the end of a thermic or radiating cycle, producing strong tridimensional shrinkings (14% in the case of the CR-39 homopolymer). Thus a further function of the spring is to contihuously squeeze the distancer of the lenses forming the mold, until the fluid reaches the intermediate gel state, to avoid the leakage of fluid monomer from the mold. On the other hand, after the gel phase has been reached, the pressure of the spring, shall straïn the thermoplastic or elastic distancer, to facilitate the adherence mould/polymer. Such a strain may be considered as a squeezing of the distancer or as an expansion of the gasket.
The mold/polymer adherence is required to avoid possible breakages of the polymer or of the mold, due to the strong tensions wh.ich occur when the polymer shrinks, and to avoid, at least on the usable surface of the polymer, air : infiltrations which, by hindering the polymerization, would cause irreparable damages to the product.
The lenses thus obtained, made of CR-39j or its copolymers, may present faulty perimeters, due to air bubbles.
Air leakages, even after the gel phase is ended, may cause air
- 2 - .
3~.q3 bubbles and cavities, or the formation of a perimetrical soft polymer stripe, or a possible chemical reactivity between the gasket material and the catalyzed monomer. A feature co~non to all processes is, any how, an appreciable reduction of the diameter of a lens made of CR-39 and its copolymers, with respect to the diameter of the lenses forming the mold. This is due to following reasons:
(A) the internal mold cavity is reduced by the space occupied by the sealing gasket, acting as distancer.
0 (B) the tridimensional shrinkage of the polyrner involves also the perimetrical stripe, thus further reducing the diameter of the product, particularly in the case of negative or diverging lenses.
(C) possible perimetrical faults (air bubbles, air suctions and a stripe of soft polymer) equally reduce the usable diameter by the affected depth.
These faults generally occur in the perimetrical stripe, as by now it is generally preferred to position the molds with their concave side upwards. Whereas the positioning of the molds with their convex side upwards, would originate the same faults at the center of the polymeric lenses, thus rendering the lenses worthless. Concavity and convexity are referred to the external side of the molds.
After the sealing gasket has been removed, the opening of the mold is carried out by lntroducing a wedge into the slot previously occupied by the distancer, and using it as a lever between the two glass lenses, which normally adhere to the ~ i polymer. The polymeric lens thus extracted is complete, so ~ar as the surfaces are concerned, but sharply tensioned due to the shrinkage. To achiéve its structural distension, the lens has then to be submitted to a thermic treatment~
This treatment, or temper distension, is currently ., ~ 3 applied to all mold plastic materials, to the glass, and tometals. The duration of the treatment, to obtain the c1esired effect, depends upon the temperature, related to the s-tate of tension exis-ting in the product and to the grade of polymeriza-tion of the polymer.
The above disclosure aims to provide a preliminary information on the prior art related to the polymerization process. It is a summary of experimental researches, carried out by the author, and of documents deriving from patents.
Among the latter the following ones are mentioned: US-PS
2.403.112/US-PS 2.464.062/ US~PS 3.171.869/UP-PS 3.038.210/-US-PS 2.964.501/ FR-PS 2.171.073/FR-PS 1.541.889/FR-PS
1.204.627!E'R-PS 1.462.519 DE-PS 1.062.003/GB-PS 1.402.573.
The present invention takes into consideration the numerous disadvantages of a technical and/or of an economical nature, which occur in the production of lenses or optical means made of CR-39 and its copolymers. The present process studies, plans and solves the problem of producing lenses or optical means made of CR-39 and its copolymers, in a completely new manner, with reference to:
- the chemical basic preparation of the components;
- the ways and the means of polymerization - the shape of the articles, obtainable without any reduction - the possible unification of the polymerization cycles, for all given thicknesses ~.
- the obtention of a polymer foreseen according special adsorption and transmission requirements of the electro- -magnetic energy.
In particular the present invention provides a poly-meri~ation process.for producingr by way of molding and con-tinuous compensation, lenses and optical means, from a p~lymer-izable thermohardening plastics material, said process comprising : _ 4 _ ~ - .
/5~
the steps oE:
- forming a tubuIar sleeve of a plast.ic material substantially indeformable, said plas-tic material being : chemically compatible with said polymerizable material and thermically stable at the temperature of polymerization, - positioning mold halveswithin said sleeve at the required distance from each other, so that they define, . with the lateral wall of khe sleeve, a cavity having a diameter equal to that of the mold halves, the position of each mold half with respect to the sleeve being only kept by friction of the ` mold half rim, over the sleeve wall, ;l - forming outside of said cavlty a compensation re-servoir communicating with said cavity through at least a pre-formed passage way, - introducing into the cavity, through said preformed passage way, catalysed polymerizable thermohardening plastics . material until said cavity is completely filled and said compen- ~:.
sation reservoir is partially filled, : ~ - submitting said mold to homogeneous heating to :
thereby cause a passage of polymerizable material in excess from the cavity of the mold, into the compensation reservoir, during the state of expansion of the polymerizable material, and a passage in the opposite dlrection during the subsequent stage of shrinkage of:the polymerizable material, until the `
, ~ .
gel stage lS reached, - continuing the heating of the mold.until the poly-merization of the polymerizable~material is completed, the final ; shrinkage of t:he latter, from the beginning of the gel stage, being only compensated through the approaching of the mold halves to each other, ~ - removlng the two mold halves from the lens thus .~ obtained when the polymerization of the polymerizable material ? ~L35~13 has been completed.
In accordance with -the present invention, catalysed polymerizable material may be submitted to a thermic cycle o 15 hours with a gradual thermic increase of from about +40C to 110C.
In the present invention, it is considered as obvious, to extend to all monomers, copolymers of the same, catalyzers or starters, likely to be used, the total or partial series of the claims, when th same reasoning, methods and devices, are ~~~~ ~~~
_ . .. . ... _ .. . .. __ ... _ _ __ .. . ~ . .. . .
~-31. 3rS~
applied to solve the same problems or to attain the same aims, and when the same results are obtained, even if only partial ones.
MO~OMER - The diethyleneglycol-bis-allyl~carbonate, or CR-39, is to be found on the market at a high purity grade i.e. about 99,150%. Gas chromatographic analysis indicates the presence of allyl-carbonate and of a not well identified su~stance.
(Fig. 1).
During the colur~ separation perormed on occasion of the a.m. analysis, it was stated that the impurities are more volatile i.e. have shorter retention times than the monomer. An experimental series was then carried out to eliminate the impurities and it was discovered the following:
- the allyl carbonate is eliminated when the monomer is submitted to a warming up at a temperatuxe of 50-90C;
- this elimination is possibly due to a partial polymerization of the allyl carbonate as it may be analytically stated by observing the area referring to the a.m. unidentified product - the latter may, as a consequence, be considered as a polymer of the allyl carbonate.
The above was confirmed during the warming up of the monomer, carried out on purpose o~ a longer time span, at a temperature of 90C, in static tanks. As the elimination of the àllyl carbonate was partially suppressed, due to the tanks staticity, the analysis of the monomer revealed an appreciable increase of the polymer, caused by the allyl carbonate. These facts having been ascertained, a depurating system of the monomer was set up, as indicated in following example:
EXAMPLE NR. 1 The monomer CR-39 was gradually warmed up, at tempera-tures in the range of 50-90C.
The partial elimination of the allyl carbonate obtained .
, ~ ~. , .
`'~ ' ~ 1 3r5~
at all the a.m. temperatures was obviously related to the ratios: time - temperature - quantity treated.
In practice at a lower temperature, a longer duration of the operation was required; whereas at higher temperature corresponded a shorter duration of the treatment.-Thus for instance:
- Quantity of the treated monomer CR-39: 1 Liter;
- Average thermic value: 70C during four hours ~ the warming up *ime and the time of the gradual cooling down to room temperature.
- Strength of the monomer, before treatment: 99,158 (Fiy. 1).
- Strength of the monomer, after treatment: 99,484 (Fig. 2).
EXAMPLE NR.2 Through gradual warming up of the monomer CR-39, at temperatures in the range of 50-90C, under active stirring, to homogenize the fluid and accelerate the elimination of allyl carbonate, the latter was partially eliminated according to the ratio time - temperature - quantity treated, (as in example N 1). Thus for instance:
- Quantity of the treated monomer CR-39. 1 Liter, - Average thermic value: 70C during 4 hours ~ the warming up time and the time of the graduai cooling down to room tem~erature;
- Strength of the monomer, before treatment: 99,158. (Fig. 1).
- Strength of the monomer after treatment: 99,713. (Fig. 3).
EXAMPLE NR 3.
Through warming up of the monomer CR-39, according to the conditions described in the Example N. 1, but carrying out the operations under vacuum, we obtained:
- Quantity of the treated monomer CR-39: 1 liter; -~
- Average thermic value: 70C during 4 hours ~ the warming up time and the time of the gradual cooling down to room . ~ . :
r~i~3 1~ 3 tempera-ture, ~ Strength of the monomer before -treatment: 99,158 (Fig. 1).
- Strength of the monomer after treatment: 99,686. (Fig. ~).
EXAMPLE NR. 4 Through warming up of the monomer CR-39, according to the conditions described in the Example N 2, but carrying out the operation under vacuum, we obtained;
- Quantity of the treated monomer CR-39: 1 liter, - Average thermic vaLue: 70C during 4 hours + the warming up time and the time of the gradual cooling down to room temperature;
- Strength of the monorner before treatment: 99,158. (Fig. 1).
- Strength of the monomer after treatment: 100%. (Fig. 5).
Through warming up of the monomer according to the conditions described in the Examples N 1,2,3 and 4 the total dehydratation of the monomer, was also obtained. Spectropho-tometric analysis, in the visible field from 400 to 700 nm, give for the thus depurated monomer CR-39, outstanding linearity and transmission.
STARTER - As a generally accepted rule the isopropyl-dicar-bonate-pero~ide, known under the commercial name of I~P.P., is added to monomer CR-39, in a percentage of 3%. This percentage has been adopted in all processes, though a higher or a lower percentage may be adopted, for special purpose.
Even if the I.P.P. of the commerce, may be considered as pure, being an industry product difficult to be synthetized and handled, it contains in practice spurs of water and free chlorine ions.
The above may be observed from the infrared spectro-photometric ana:Lysis (Fig. 6)~ To start a series of tests aiming at ascertaining the influence of the chlorine ions on , .,; . . . . ~ ,. . .
the polymerization, in the frame of the present invention, the isopropyl-dicarbonate-peroxide was synthetized through reaction between sodium peroxide and isopropyl-chloroformiate, (previously purified up to 99,99%). The product obtained was used, after 1,2,3,4,5 water leachings. Each leaching produced an appreciable reduction of the chlorine ions. By polymerizing the monomer CR-39, with the addition of 3% of isopropyl~dicarbonate-peraxide (obtained from the a.m. repetitive leachings), according to a gradual thermic cycle of 15 hours, from +40C to fllooc~ we obtained:
- after 1 leaching only: a frankly yellow polymer, - after 2 leachings: a yellow polymer, - after 3 leachings: a pale yellow polymer, - after 4 leachings: a straw-yellow polymer, - after 5 leachings: 2 colourless polymer.
It was thus ascertained that the yellowing of the ;
polymer depends upon an higher content of chlorine ions.
On the other hand, when leaching with water the isopropyl-dicarbonate~peroxide, we separated a lighter fraction of the same product partially degraded, due to deoxygenation.
To obtain an isopropyl-dicarbonate-peroxide, with the highest grade of purity from free chlorine ions, and degraded deoxygenated fractions, we followed the following line of operations.
EXAMPLE NR ~
In a bain-marie, cooled to +9C we melted 100gr, of commercial I.P.P. having a point of fusion of -~ 8C. We added H20 cooled to ~ 9C , into which some drops of pyridin had been solved. After stirring and decanting, the phases were separated.
We then washed twice, with H20, the isopropyl-di-carbonate-peroxide and carefully separated, together with the 3~
water, the ligh-ter fraction of the isopropyl-dicarbonate-peroxide, corresponding to the partially degraded or deoxy-genated product. At this point a purified I.P.P. had been obtained. (Fig. 7).
EXAMPLE NR. 7 When the I.P.P., purified according to the above described method (Example N 6), was frozen again and after-wards brought to melting, we observed a me]ting point of -~ 9C
(instead ~ 8C of the starting material).
EXAMPLE NR. 8 Two test samples prepared with the same CR-39 monomer, catalyzed under the same polymerization conditions , respectively with the addition of 3% of - Commercial I.P.P., and - I.P.P. depurated according to the method described in Example N 6 above;
showed following differences, at 53C, after 4 hours of gradual induced warming up from 40.
- in the test sample added with commercial I.P.P. the monomer was present in the polymer in a percentage of 52%; and - in the test sample added with I.P.P., depurated according to the described method, the monomer was present in the polymer, in a percentage of 34%.
In other words, the use of depurated I.P.P. (when compared with that of commercial I.P.P.) causes a higher catalytic activity, likely to allow to obtain a given polymeric value, with:
- reduced percentages of the starter, - shorter times of reaction, and - lower temperatures.
Furthermore the test sample, obtained from purified I.P.P., was perfectly colourless.
g ', ' ' . : '`
~3~ 3 ADDITIVES The addition to the monomers of additives which absorb the U.V. radiation, allow the protection of polymers from the degr~dation caused by the said radiation.
As the U.V. absorbers are not easily soluble, follow~
ing drawbacks may be observed in the polymer according to the quality and quantity o~ the absorber used:
- optical distortion (diffraction and dispersion), due to the unsatisfactory distribution of the absorbers, within the monomer, - yellow green yellow, orange yellow colour of the product, - transmission intererence in th,e visible electromagnetic ~ield.
With reference to the present invention we selected as absorber the 2 - (2-hydroxy-5-methyl-phenyl) benzo-triazole.
To establish the optimal quantity of said U.V. absorber, to be added to the monomer CR-39, with respect to the interferences likely to be caused in the polymer by said addition, so far as the transmission of the visible light is concerned, and the solution methods.
The Operations were carried out as follows:
EXAMPLE NR. 9 We obtained a highly satisfactory solution and distribution of 2 (2 hydroxy-5-methyl-phenyl) benzotriazole, in the percentage of 0,0125% in the purified monomer CR-39, (or catalyzed with I.P.P.) by inducing to the container, ultrasonic frequencies in the range of 20-70 KHertz. The selected percentage of 0,0125% of 2.(2.hydroxy-5-methyl--phenyl) benzotriazole caused in the polymer CR-39, on test samples of 4 mm of thickness, a good U.V. absorption and an ~`
almost linear transmission in the visible field. (Fig. 8).
EXAMPLE NR. 10 With the use of ultrasounds we obtained the perfect solution and distribution of 2(2-hydroxy- -5-methyl-phenyl) benzotriazole in the monomer CR~39, both pure or catalyzed with I~P.P., in the selected percentage of 0,0100%. The latter percentage of additive originated in the polymer spectra close to what has been described in Example N 9, on test samples of 6 mm of thickness.
EXAMPLE NR~ 11 With the use of ultrasounds, it was possible to obtain the perfect solution and distribution of 2(2-hydroxy-5-methyl-phenyl) benzotriazole, in the monomer CR-39, both pure or catalyzed with I.P.P., in the selected percentage of 0,0150%.
The spectra thus originated in the polymer were close to those described in Example N 9, on test samples of 2 mm of thickness.
EXA~PLE NR. 12 With the use of ultrasounds it was possible to obtain the perfect solution and distribution of a very high percentage of 2(2~hydroxy-5-methyl-phenyl) benzotriazole, with respect to those described in the Examples N 9,10 and 11 above, both in the pure monomer or catalyzed with I.P.P. or with benzoyl-peroxide. It was thus possible to obtain the preparation of easily tested concentrates, which later on were diluted in the desired percentage, in large quantities of pure of catalyzedmonomer.
EXAMPLE NR. 13 CATALYSIS- Under mechanical stirring we mixed:
- CR-39 monomer, depurated and dehydrated as indicated in Examples N 1,2,3 and 4 above, wlth - 3% of I.P.P. depurated as in Example N 6 above, and - 0,0125% of 2(2~hydroxy-5-methyl-phenyl) benzotriazole, as in Examples N 9 and 12 above, the whole being filtèred, under decompression.
EXAMPLE NR. 14 Through ultrasonic induction we mixed:
-- 11 _ ,. :.
.
3L.31.3,5~ 3 - CR-39 monomer, purified and dehydrated as indicated in Examples N 1,2,3 and ~ above, with - 3% of I.P.P. depurated as in Exa~ple N 6 above, and - 0,0125 of 2(2-hydroxy-5-methyl-phenyl) benzotriazole, as in Examples N 9 and 12 above, the whole being filtered under decompression.
EXAMPLE NR. 15 With CR-39 monomer, catalyzed and with the addition of additive, as indicated in the Examples N 13 and 1~ above, and submitted to a thermical cycle of polymerization, we obtained practically colourless transparent polymers. The latter, if compared with polymers obtained through a current preparation showed a quicker and more uniform polymerization cycle, with reference to the reactive saturation within a time X, for thermical cycles Y and thickness Z. Furthermore said polymers showed outstanding physico--chemical characteristics, as observed through thermic differential calorimetric analysis, and tests of chemical inertia.
It may be observed that the methods described in the examples above are an improvement or a variant of the techni-ques already followed up to now, whereas the proportions of the components correspond to values which may be modified, even though following the same techniques. ;;
The Author, in describing the invention in detail, aims at leading towards the same claims, the combination of the various techniques, proportions and/or the share of individual components.
PRINCIPLE OF CONTINUOUS MOLDS COMPENSATION- The shrinkage of CR-39 polymer and its copolymers, causes - as a rule - the need of introducing devices, of an empirical nature to eliminate all possible drawbacks. Generally the polymerization has been carried out with variable thermical cycles, according to the - 12 _ ~ 3~
thickness of the polymer. Other devices refer to the ways of assembling the molds and/or to intermediate manipulations.
As a rule, with the increase in the thickness of the polymer the duration of the thermic cycles was extended, even to the outmost; the molds filled with the catalyzed monomer were kept at a low temperature (about -~ 40C) for a long span of time, to slow down the reaction's speed and to reduce, so far as possible, the ~egative effects of the shrinkage of the polymers.
Within the frame of the present invention we ound ; a satisfactory solution to the problem through a continuous molds compensation, wherein the catalyzed monomer i9 likely to fill the cavities, formed during the polymerization, due to the shrinkage of the polymer. The above is possible as the CR-39 monomer, and its copolymers, with addition of peroxide or percarbonate as catalyzer, pol~merize only partially and, in any case very slowly, in the presence of air, and rema1n in a fluld state for a long span of time.
We assembled as follows, molds for the casting of optical lenses.
, EXAMP1E NR. 16 Two or more glass lenses, were introduced and brought to slide down within a tubular stripe of polyethilene (or of a different material, which would not react with the catalyzed monomer). me diameter of the tube was kept within such dimensions as to originate sliding elasticity or friction, and -to allow the positioning of the lenses at the desired dlstance from each other. Thus one or more cavities were created by the lenses' curvature. (Fig. 9 wherein 1 = tubular stripe; 2 = lenses; 3 = cavity).
EXAMPLE NR. 17 Two or more glass lenses were introduced and brought ~13~ f~ L3 -to slide down within a tubular s-tripe, as in the Example ~. 16 above, of such a diameter to originate s:Liding elasticity or friction. Beforehand we had introduced or created in the tubular stripe a distancer having a desired length and a minimum thickness, to cause the interruption of the sliding of the lenses. (Fig. 10 wherein: 1 - tubular stripe' 2 =
lenses; 3 ~ cavity; 4 = distancer).
EXAMPLE NR. 18 Two or more glass lenses were slided down a tubular stripe, as in Example N 16 above, the diameter of the tube being about the~same as that of the lenses. A distancer had been introduced or casted beforehand in the tube, as in Example N 17 above.
EXAMPLE NR. 19 The molds prepared according to Examples N 16,17 and 18 above, were filled with CR-39 monomer, catalyzed according to Examples N 13 and 14 above, and positioned with their convex side upwards. The catalyzed monomer was added in the perimetrical channel, partially formed from the surface of the higher situated lens, and partially from the internal wall of the tube. (Fig. 11 and Fig. 12, wherein: 1 = tube, 2 =
lenses; 5 = catalyzed monomer).
EXAMPLE NR. 20 The molds prepared according to Examples N 16, 17 and 18 above, were filled with CR-39 monomer, catalyzed accord-ing to Examples N 13 and 14 above, and positioned with their concave side upwards. Catalyzed monomer was added in the internal cavity of the higher situated lens, up to reach the internal walI of the tube. (Fig~ 13 and Fig. 14, wherein:
1 = tube; 2 = lenses; 5 = catalyzed monomer).
EXAMPLE NR. 21 The molds prepared according to Examples N 16, 17 _ 14 -~3 ~ ~
and 18 above, were ~illed wi-th CR--39 monomer, catalyzed accord-ing to Examples N 13 and 14 above, and positioned horizontally, according to Examples N 19 and 20 above. The tubular stripes were provided with, or formed as, a receptacle communicating with the internal cavity of the molds. The receptacle was also filled with the catalyzed monomer~ Said receptacle had been made by totally or partially covering the perimeter of the tube inside and/or outside. (Fig. 15 and Fig. 16, wherein:
1 = tube, 2 = lenses; 5 - catalyzed monomer; 6 = receptacle).
EXAMPLE NR. 22 The molds prepared according to Examples N 16, 17 and 18 above, were filled with CR-39 monomer, catalyzed according to Examples N~ 13 and 14 above, and positioned vertically. The external tubular stripes were provided with, or formed as, a receFtacle communicating with the internal cavity of the molds. Said receptacle was aLso filled with the catalyzed monomer. (Fig. 17, wherein: 1 = tubular strip, 2 = lenses; 5 = catalyzed monomer, 6 - receptacle).
EXAMPLE NR. 23 ~11 the molds prepared and positioned as indicated in the Examples above, the cavities of which corresponded to the shape of every type of lens (vertical, convergent, divergent, cylindrical, lenticular, bifocal; prismatic etc.) were submitted, in an oven, to the same thermic cycle of 15 hours (Fig. 18).
me vertical stroke appearing in the cycle, indicates, as it will be further explained, the moment where the springs were applied to the molds, i.e. when the gel phase of the monomer had been completed. The perfectly polymerized lenses thus obtained, showed finished surfaces and various curves and thicknesses. Their diameter was practically equal to that of the glass lenses forming the simple or multiple molds (with a very low reduction equal, as an average to 0,7 %)~
_ 15 -. . .
.. q~
It was thus experimentally confirmed how the continu-ous compensation had operated, according to the ways and means described in the Examples above, establishing a continuous flow of polymerizable monomer from the outside into the inside of the molds, compensating the shrinkages, hindering the suctions and/or the creation of air bubbles, which would have caused the separation of the polymer from the mold.
~ he flow from the exterior to the interior had been made possible by means of preformed passages or through capillar-ity. The polymers thus obtained had a particularly homogene-ous aspect.
SELF-POSITIONING SPRING ~ Many CR-39 lenses, available on the market,~when examined with polarized light, show tensions which cannot be removed, even submitting the polymers to heat-treat-ment. In the frame of the present invention we considered the convenience of applying a pressure on the lenses forming the mold, after the polymer had reached the gel phase. It was then decided to introduce a spring, likely to lean on every kind of curved or plain surface, and to position itself through homogeneous contact on the whole of the support surface, to ` avoid localized high pressure, likely to cause the breaking of the molde or of the polymers, or unacceptable pressures on the polymers themselves.
EXAMPLE NR. 24 We built whlch springs, easily lean on the molds, by means of the compression of levers 7, 8, causing the elastic opening of the pressers 9, I0. The latter, consisting of small saucers 11, 12, shaped as a meniscus, may swing in all directions around pins 13, 14. Said springs adapt to whichever molds assembly including curves or various plains and by means of the swinging of the small plates, allow a perfect adherence, likely to exert an even pressure, very useful to the production ' ~ ' . ~. ., , , , ;. , ~ .. ~ . .
3~ ~
of regular polymers. (Fig. 19 and Fig. 20).
EXAMPLE NR. 25 Spring3 as in Example N 24 above, but provided with only one small saucer. (Fig~ 21).
OPENING OF T~E MOLDS - The lens mad.e of C~-39 and its copolymers, is strongly adherent to the casti:ng mold, thus the separation from each other is a problem dif~icult to solve, particularly in the frame of the present invention. In fact, as the diameter of the polymer obtained, is practically equal to the molds, it is impossible to achieve a mechanical separation by means of a wedge or a similar tool. In the frame of the present invention it was discovered that ultrasounds in the range of 20-70 KHertz, induced in a tank filled with water, in which the molds had been immersed, after the polymerization of their content, caused the separation of the polymers from the molds.
.. EXAMPLE NR. 26 To separate the polymer from the glass lenses, forming the molds,.the latter were immersed in warm water baths, after which ultrasonic frequencies in the range of 20-70 KHertz were induced.
In all cases, after some minutes, the polymer separated from the molds. The duration of the operation depended upon the bath tem.perature: it was shorter for an higher temperature and vice versa.
; EXAMPLE NR. 27 To carry out at the same time the separation of the polymer obtained from the glass lenses constituting the molds, and a first washing up of the latter, the molds were immersed in warm baths of water solution of any type of cleansing usbstance (such as detergent, detersive, degreasing, emulsify-ing or saporification agent, solvent, acid or alcaline sub-stance). In every case, within some minutes from the induction :`~
to the bath of ultrasonic frequencies, in the range of 20-70 KHertz, the polymer separated from the molds: the relation:
duration of the operation/bath temperature was the same as indicated in the Example N 26.
From the above it appears evident that the described process and/or the means object of the present invention, which allow the production of quality lenses or other optical means, made of CR-39 and its copolymers, may be directly or indirectly related to the whole field of applications of casted homo- :
polymers and copolymers with reference to the casting of whichever product, and the applicability or the selection of a whichever polymerizable resin. It also clearly appears that the examples - though referring to specific realizations of the present invention, cannot be considered as limiting the latter.
: It is underlined that the process as a whole, attains in a synergistic manner, the advantages obtainable by means of each described operation or means, with respect to their individual Euncti~s ' '' '~
" ',' ; :~
,
(A) the internal mold cavity is reduced by the space occupied by the sealing gasket, acting as distancer.
0 (B) the tridimensional shrinkage of the polyrner involves also the perimetrical stripe, thus further reducing the diameter of the product, particularly in the case of negative or diverging lenses.
(C) possible perimetrical faults (air bubbles, air suctions and a stripe of soft polymer) equally reduce the usable diameter by the affected depth.
These faults generally occur in the perimetrical stripe, as by now it is generally preferred to position the molds with their concave side upwards. Whereas the positioning of the molds with their convex side upwards, would originate the same faults at the center of the polymeric lenses, thus rendering the lenses worthless. Concavity and convexity are referred to the external side of the molds.
After the sealing gasket has been removed, the opening of the mold is carried out by lntroducing a wedge into the slot previously occupied by the distancer, and using it as a lever between the two glass lenses, which normally adhere to the ~ i polymer. The polymeric lens thus extracted is complete, so ~ar as the surfaces are concerned, but sharply tensioned due to the shrinkage. To achiéve its structural distension, the lens has then to be submitted to a thermic treatment~
This treatment, or temper distension, is currently ., ~ 3 applied to all mold plastic materials, to the glass, and tometals. The duration of the treatment, to obtain the c1esired effect, depends upon the temperature, related to the s-tate of tension exis-ting in the product and to the grade of polymeriza-tion of the polymer.
The above disclosure aims to provide a preliminary information on the prior art related to the polymerization process. It is a summary of experimental researches, carried out by the author, and of documents deriving from patents.
Among the latter the following ones are mentioned: US-PS
2.403.112/US-PS 2.464.062/ US~PS 3.171.869/UP-PS 3.038.210/-US-PS 2.964.501/ FR-PS 2.171.073/FR-PS 1.541.889/FR-PS
1.204.627!E'R-PS 1.462.519 DE-PS 1.062.003/GB-PS 1.402.573.
The present invention takes into consideration the numerous disadvantages of a technical and/or of an economical nature, which occur in the production of lenses or optical means made of CR-39 and its copolymers. The present process studies, plans and solves the problem of producing lenses or optical means made of CR-39 and its copolymers, in a completely new manner, with reference to:
- the chemical basic preparation of the components;
- the ways and the means of polymerization - the shape of the articles, obtainable without any reduction - the possible unification of the polymerization cycles, for all given thicknesses ~.
- the obtention of a polymer foreseen according special adsorption and transmission requirements of the electro- -magnetic energy.
In particular the present invention provides a poly-meri~ation process.for producingr by way of molding and con-tinuous compensation, lenses and optical means, from a p~lymer-izable thermohardening plastics material, said process comprising : _ 4 _ ~ - .
/5~
the steps oE:
- forming a tubuIar sleeve of a plast.ic material substantially indeformable, said plas-tic material being : chemically compatible with said polymerizable material and thermically stable at the temperature of polymerization, - positioning mold halveswithin said sleeve at the required distance from each other, so that they define, . with the lateral wall of khe sleeve, a cavity having a diameter equal to that of the mold halves, the position of each mold half with respect to the sleeve being only kept by friction of the ` mold half rim, over the sleeve wall, ;l - forming outside of said cavlty a compensation re-servoir communicating with said cavity through at least a pre-formed passage way, - introducing into the cavity, through said preformed passage way, catalysed polymerizable thermohardening plastics . material until said cavity is completely filled and said compen- ~:.
sation reservoir is partially filled, : ~ - submitting said mold to homogeneous heating to :
thereby cause a passage of polymerizable material in excess from the cavity of the mold, into the compensation reservoir, during the state of expansion of the polymerizable material, and a passage in the opposite dlrection during the subsequent stage of shrinkage of:the polymerizable material, until the `
, ~ .
gel stage lS reached, - continuing the heating of the mold.until the poly-merization of the polymerizable~material is completed, the final ; shrinkage of t:he latter, from the beginning of the gel stage, being only compensated through the approaching of the mold halves to each other, ~ - removlng the two mold halves from the lens thus .~ obtained when the polymerization of the polymerizable material ? ~L35~13 has been completed.
In accordance with -the present invention, catalysed polymerizable material may be submitted to a thermic cycle o 15 hours with a gradual thermic increase of from about +40C to 110C.
In the present invention, it is considered as obvious, to extend to all monomers, copolymers of the same, catalyzers or starters, likely to be used, the total or partial series of the claims, when th same reasoning, methods and devices, are ~~~~ ~~~
_ . .. . ... _ .. . .. __ ... _ _ __ .. . ~ . .. . .
~-31. 3rS~
applied to solve the same problems or to attain the same aims, and when the same results are obtained, even if only partial ones.
MO~OMER - The diethyleneglycol-bis-allyl~carbonate, or CR-39, is to be found on the market at a high purity grade i.e. about 99,150%. Gas chromatographic analysis indicates the presence of allyl-carbonate and of a not well identified su~stance.
(Fig. 1).
During the colur~ separation perormed on occasion of the a.m. analysis, it was stated that the impurities are more volatile i.e. have shorter retention times than the monomer. An experimental series was then carried out to eliminate the impurities and it was discovered the following:
- the allyl carbonate is eliminated when the monomer is submitted to a warming up at a temperatuxe of 50-90C;
- this elimination is possibly due to a partial polymerization of the allyl carbonate as it may be analytically stated by observing the area referring to the a.m. unidentified product - the latter may, as a consequence, be considered as a polymer of the allyl carbonate.
The above was confirmed during the warming up of the monomer, carried out on purpose o~ a longer time span, at a temperature of 90C, in static tanks. As the elimination of the àllyl carbonate was partially suppressed, due to the tanks staticity, the analysis of the monomer revealed an appreciable increase of the polymer, caused by the allyl carbonate. These facts having been ascertained, a depurating system of the monomer was set up, as indicated in following example:
EXAMPLE NR. 1 The monomer CR-39 was gradually warmed up, at tempera-tures in the range of 50-90C.
The partial elimination of the allyl carbonate obtained .
, ~ ~. , .
`'~ ' ~ 1 3r5~
at all the a.m. temperatures was obviously related to the ratios: time - temperature - quantity treated.
In practice at a lower temperature, a longer duration of the operation was required; whereas at higher temperature corresponded a shorter duration of the treatment.-Thus for instance:
- Quantity of the treated monomer CR-39: 1 Liter;
- Average thermic value: 70C during four hours ~ the warming up *ime and the time of the gradual cooling down to room temperature.
- Strength of the monomer, before treatment: 99,158 (Fiy. 1).
- Strength of the monomer, after treatment: 99,484 (Fig. 2).
EXAMPLE NR.2 Through gradual warming up of the monomer CR-39, at temperatures in the range of 50-90C, under active stirring, to homogenize the fluid and accelerate the elimination of allyl carbonate, the latter was partially eliminated according to the ratio time - temperature - quantity treated, (as in example N 1). Thus for instance:
- Quantity of the treated monomer CR-39. 1 Liter, - Average thermic value: 70C during 4 hours ~ the warming up time and the time of the graduai cooling down to room tem~erature;
- Strength of the monomer, before treatment: 99,158. (Fig. 1).
- Strength of the monomer after treatment: 99,713. (Fig. 3).
EXAMPLE NR 3.
Through warming up of the monomer CR-39, according to the conditions described in the Example N. 1, but carrying out the operations under vacuum, we obtained:
- Quantity of the treated monomer CR-39: 1 liter; -~
- Average thermic value: 70C during 4 hours ~ the warming up time and the time of the gradual cooling down to room . ~ . :
r~i~3 1~ 3 tempera-ture, ~ Strength of the monomer before -treatment: 99,158 (Fig. 1).
- Strength of the monomer after treatment: 99,686. (Fig. ~).
EXAMPLE NR. 4 Through warming up of the monomer CR-39, according to the conditions described in the Example N 2, but carrying out the operation under vacuum, we obtained;
- Quantity of the treated monomer CR-39: 1 liter, - Average thermic vaLue: 70C during 4 hours + the warming up time and the time of the gradual cooling down to room temperature;
- Strength of the monorner before treatment: 99,158. (Fig. 1).
- Strength of the monomer after treatment: 100%. (Fig. 5).
Through warming up of the monomer according to the conditions described in the Examples N 1,2,3 and 4 the total dehydratation of the monomer, was also obtained. Spectropho-tometric analysis, in the visible field from 400 to 700 nm, give for the thus depurated monomer CR-39, outstanding linearity and transmission.
STARTER - As a generally accepted rule the isopropyl-dicar-bonate-pero~ide, known under the commercial name of I~P.P., is added to monomer CR-39, in a percentage of 3%. This percentage has been adopted in all processes, though a higher or a lower percentage may be adopted, for special purpose.
Even if the I.P.P. of the commerce, may be considered as pure, being an industry product difficult to be synthetized and handled, it contains in practice spurs of water and free chlorine ions.
The above may be observed from the infrared spectro-photometric ana:Lysis (Fig. 6)~ To start a series of tests aiming at ascertaining the influence of the chlorine ions on , .,; . . . . ~ ,. . .
the polymerization, in the frame of the present invention, the isopropyl-dicarbonate-peroxide was synthetized through reaction between sodium peroxide and isopropyl-chloroformiate, (previously purified up to 99,99%). The product obtained was used, after 1,2,3,4,5 water leachings. Each leaching produced an appreciable reduction of the chlorine ions. By polymerizing the monomer CR-39, with the addition of 3% of isopropyl~dicarbonate-peraxide (obtained from the a.m. repetitive leachings), according to a gradual thermic cycle of 15 hours, from +40C to fllooc~ we obtained:
- after 1 leaching only: a frankly yellow polymer, - after 2 leachings: a yellow polymer, - after 3 leachings: a pale yellow polymer, - after 4 leachings: a straw-yellow polymer, - after 5 leachings: 2 colourless polymer.
It was thus ascertained that the yellowing of the ;
polymer depends upon an higher content of chlorine ions.
On the other hand, when leaching with water the isopropyl-dicarbonate~peroxide, we separated a lighter fraction of the same product partially degraded, due to deoxygenation.
To obtain an isopropyl-dicarbonate-peroxide, with the highest grade of purity from free chlorine ions, and degraded deoxygenated fractions, we followed the following line of operations.
EXAMPLE NR ~
In a bain-marie, cooled to +9C we melted 100gr, of commercial I.P.P. having a point of fusion of -~ 8C. We added H20 cooled to ~ 9C , into which some drops of pyridin had been solved. After stirring and decanting, the phases were separated.
We then washed twice, with H20, the isopropyl-di-carbonate-peroxide and carefully separated, together with the 3~
water, the ligh-ter fraction of the isopropyl-dicarbonate-peroxide, corresponding to the partially degraded or deoxy-genated product. At this point a purified I.P.P. had been obtained. (Fig. 7).
EXAMPLE NR. 7 When the I.P.P., purified according to the above described method (Example N 6), was frozen again and after-wards brought to melting, we observed a me]ting point of -~ 9C
(instead ~ 8C of the starting material).
EXAMPLE NR. 8 Two test samples prepared with the same CR-39 monomer, catalyzed under the same polymerization conditions , respectively with the addition of 3% of - Commercial I.P.P., and - I.P.P. depurated according to the method described in Example N 6 above;
showed following differences, at 53C, after 4 hours of gradual induced warming up from 40.
- in the test sample added with commercial I.P.P. the monomer was present in the polymer in a percentage of 52%; and - in the test sample added with I.P.P., depurated according to the described method, the monomer was present in the polymer, in a percentage of 34%.
In other words, the use of depurated I.P.P. (when compared with that of commercial I.P.P.) causes a higher catalytic activity, likely to allow to obtain a given polymeric value, with:
- reduced percentages of the starter, - shorter times of reaction, and - lower temperatures.
Furthermore the test sample, obtained from purified I.P.P., was perfectly colourless.
g ', ' ' . : '`
~3~ 3 ADDITIVES The addition to the monomers of additives which absorb the U.V. radiation, allow the protection of polymers from the degr~dation caused by the said radiation.
As the U.V. absorbers are not easily soluble, follow~
ing drawbacks may be observed in the polymer according to the quality and quantity o~ the absorber used:
- optical distortion (diffraction and dispersion), due to the unsatisfactory distribution of the absorbers, within the monomer, - yellow green yellow, orange yellow colour of the product, - transmission intererence in th,e visible electromagnetic ~ield.
With reference to the present invention we selected as absorber the 2 - (2-hydroxy-5-methyl-phenyl) benzo-triazole.
To establish the optimal quantity of said U.V. absorber, to be added to the monomer CR-39, with respect to the interferences likely to be caused in the polymer by said addition, so far as the transmission of the visible light is concerned, and the solution methods.
The Operations were carried out as follows:
EXAMPLE NR. 9 We obtained a highly satisfactory solution and distribution of 2 (2 hydroxy-5-methyl-phenyl) benzotriazole, in the percentage of 0,0125% in the purified monomer CR-39, (or catalyzed with I.P.P.) by inducing to the container, ultrasonic frequencies in the range of 20-70 KHertz. The selected percentage of 0,0125% of 2.(2.hydroxy-5-methyl--phenyl) benzotriazole caused in the polymer CR-39, on test samples of 4 mm of thickness, a good U.V. absorption and an ~`
almost linear transmission in the visible field. (Fig. 8).
EXAMPLE NR. 10 With the use of ultrasounds we obtained the perfect solution and distribution of 2(2-hydroxy- -5-methyl-phenyl) benzotriazole in the monomer CR~39, both pure or catalyzed with I~P.P., in the selected percentage of 0,0100%. The latter percentage of additive originated in the polymer spectra close to what has been described in Example N 9, on test samples of 6 mm of thickness.
EXAMPLE NR~ 11 With the use of ultrasounds, it was possible to obtain the perfect solution and distribution of 2(2-hydroxy-5-methyl-phenyl) benzotriazole, in the monomer CR-39, both pure or catalyzed with I.P.P., in the selected percentage of 0,0150%.
The spectra thus originated in the polymer were close to those described in Example N 9, on test samples of 2 mm of thickness.
EXA~PLE NR. 12 With the use of ultrasounds it was possible to obtain the perfect solution and distribution of a very high percentage of 2(2~hydroxy-5-methyl-phenyl) benzotriazole, with respect to those described in the Examples N 9,10 and 11 above, both in the pure monomer or catalyzed with I.P.P. or with benzoyl-peroxide. It was thus possible to obtain the preparation of easily tested concentrates, which later on were diluted in the desired percentage, in large quantities of pure of catalyzedmonomer.
EXAMPLE NR. 13 CATALYSIS- Under mechanical stirring we mixed:
- CR-39 monomer, depurated and dehydrated as indicated in Examples N 1,2,3 and 4 above, wlth - 3% of I.P.P. depurated as in Example N 6 above, and - 0,0125% of 2(2~hydroxy-5-methyl-phenyl) benzotriazole, as in Examples N 9 and 12 above, the whole being filtèred, under decompression.
EXAMPLE NR. 14 Through ultrasonic induction we mixed:
-- 11 _ ,. :.
.
3L.31.3,5~ 3 - CR-39 monomer, purified and dehydrated as indicated in Examples N 1,2,3 and ~ above, with - 3% of I.P.P. depurated as in Exa~ple N 6 above, and - 0,0125 of 2(2-hydroxy-5-methyl-phenyl) benzotriazole, as in Examples N 9 and 12 above, the whole being filtered under decompression.
EXAMPLE NR. 15 With CR-39 monomer, catalyzed and with the addition of additive, as indicated in the Examples N 13 and 1~ above, and submitted to a thermical cycle of polymerization, we obtained practically colourless transparent polymers. The latter, if compared with polymers obtained through a current preparation showed a quicker and more uniform polymerization cycle, with reference to the reactive saturation within a time X, for thermical cycles Y and thickness Z. Furthermore said polymers showed outstanding physico--chemical characteristics, as observed through thermic differential calorimetric analysis, and tests of chemical inertia.
It may be observed that the methods described in the examples above are an improvement or a variant of the techni-ques already followed up to now, whereas the proportions of the components correspond to values which may be modified, even though following the same techniques. ;;
The Author, in describing the invention in detail, aims at leading towards the same claims, the combination of the various techniques, proportions and/or the share of individual components.
PRINCIPLE OF CONTINUOUS MOLDS COMPENSATION- The shrinkage of CR-39 polymer and its copolymers, causes - as a rule - the need of introducing devices, of an empirical nature to eliminate all possible drawbacks. Generally the polymerization has been carried out with variable thermical cycles, according to the - 12 _ ~ 3~
thickness of the polymer. Other devices refer to the ways of assembling the molds and/or to intermediate manipulations.
As a rule, with the increase in the thickness of the polymer the duration of the thermic cycles was extended, even to the outmost; the molds filled with the catalyzed monomer were kept at a low temperature (about -~ 40C) for a long span of time, to slow down the reaction's speed and to reduce, so far as possible, the ~egative effects of the shrinkage of the polymers.
Within the frame of the present invention we ound ; a satisfactory solution to the problem through a continuous molds compensation, wherein the catalyzed monomer i9 likely to fill the cavities, formed during the polymerization, due to the shrinkage of the polymer. The above is possible as the CR-39 monomer, and its copolymers, with addition of peroxide or percarbonate as catalyzer, pol~merize only partially and, in any case very slowly, in the presence of air, and rema1n in a fluld state for a long span of time.
We assembled as follows, molds for the casting of optical lenses.
, EXAMP1E NR. 16 Two or more glass lenses, were introduced and brought to slide down within a tubular stripe of polyethilene (or of a different material, which would not react with the catalyzed monomer). me diameter of the tube was kept within such dimensions as to originate sliding elasticity or friction, and -to allow the positioning of the lenses at the desired dlstance from each other. Thus one or more cavities were created by the lenses' curvature. (Fig. 9 wherein 1 = tubular stripe; 2 = lenses; 3 = cavity).
EXAMPLE NR. 17 Two or more glass lenses were introduced and brought ~13~ f~ L3 -to slide down within a tubular s-tripe, as in the Example ~. 16 above, of such a diameter to originate s:Liding elasticity or friction. Beforehand we had introduced or created in the tubular stripe a distancer having a desired length and a minimum thickness, to cause the interruption of the sliding of the lenses. (Fig. 10 wherein: 1 - tubular stripe' 2 =
lenses; 3 ~ cavity; 4 = distancer).
EXAMPLE NR. 18 Two or more glass lenses were slided down a tubular stripe, as in Example N 16 above, the diameter of the tube being about the~same as that of the lenses. A distancer had been introduced or casted beforehand in the tube, as in Example N 17 above.
EXAMPLE NR. 19 The molds prepared according to Examples N 16,17 and 18 above, were filled with CR-39 monomer, catalyzed according to Examples N 13 and 14 above, and positioned with their convex side upwards. The catalyzed monomer was added in the perimetrical channel, partially formed from the surface of the higher situated lens, and partially from the internal wall of the tube. (Fig. 11 and Fig. 12, wherein: 1 = tube, 2 =
lenses; 5 = catalyzed monomer).
EXAMPLE NR. 20 The molds prepared according to Examples N 16, 17 and 18 above, were filled with CR-39 monomer, catalyzed accord-ing to Examples N 13 and 14 above, and positioned with their concave side upwards. Catalyzed monomer was added in the internal cavity of the higher situated lens, up to reach the internal walI of the tube. (Fig~ 13 and Fig. 14, wherein:
1 = tube; 2 = lenses; 5 = catalyzed monomer).
EXAMPLE NR. 21 The molds prepared according to Examples N 16, 17 _ 14 -~3 ~ ~
and 18 above, were ~illed wi-th CR--39 monomer, catalyzed accord-ing to Examples N 13 and 14 above, and positioned horizontally, according to Examples N 19 and 20 above. The tubular stripes were provided with, or formed as, a receptacle communicating with the internal cavity of the molds. The receptacle was also filled with the catalyzed monomer~ Said receptacle had been made by totally or partially covering the perimeter of the tube inside and/or outside. (Fig. 15 and Fig. 16, wherein:
1 = tube, 2 = lenses; 5 - catalyzed monomer; 6 = receptacle).
EXAMPLE NR. 22 The molds prepared according to Examples N 16, 17 and 18 above, were filled with CR-39 monomer, catalyzed according to Examples N~ 13 and 14 above, and positioned vertically. The external tubular stripes were provided with, or formed as, a receFtacle communicating with the internal cavity of the molds. Said receptacle was aLso filled with the catalyzed monomer. (Fig. 17, wherein: 1 = tubular strip, 2 = lenses; 5 = catalyzed monomer, 6 - receptacle).
EXAMPLE NR. 23 ~11 the molds prepared and positioned as indicated in the Examples above, the cavities of which corresponded to the shape of every type of lens (vertical, convergent, divergent, cylindrical, lenticular, bifocal; prismatic etc.) were submitted, in an oven, to the same thermic cycle of 15 hours (Fig. 18).
me vertical stroke appearing in the cycle, indicates, as it will be further explained, the moment where the springs were applied to the molds, i.e. when the gel phase of the monomer had been completed. The perfectly polymerized lenses thus obtained, showed finished surfaces and various curves and thicknesses. Their diameter was practically equal to that of the glass lenses forming the simple or multiple molds (with a very low reduction equal, as an average to 0,7 %)~
_ 15 -. . .
.. q~
It was thus experimentally confirmed how the continu-ous compensation had operated, according to the ways and means described in the Examples above, establishing a continuous flow of polymerizable monomer from the outside into the inside of the molds, compensating the shrinkages, hindering the suctions and/or the creation of air bubbles, which would have caused the separation of the polymer from the mold.
~ he flow from the exterior to the interior had been made possible by means of preformed passages or through capillar-ity. The polymers thus obtained had a particularly homogene-ous aspect.
SELF-POSITIONING SPRING ~ Many CR-39 lenses, available on the market,~when examined with polarized light, show tensions which cannot be removed, even submitting the polymers to heat-treat-ment. In the frame of the present invention we considered the convenience of applying a pressure on the lenses forming the mold, after the polymer had reached the gel phase. It was then decided to introduce a spring, likely to lean on every kind of curved or plain surface, and to position itself through homogeneous contact on the whole of the support surface, to ` avoid localized high pressure, likely to cause the breaking of the molde or of the polymers, or unacceptable pressures on the polymers themselves.
EXAMPLE NR. 24 We built whlch springs, easily lean on the molds, by means of the compression of levers 7, 8, causing the elastic opening of the pressers 9, I0. The latter, consisting of small saucers 11, 12, shaped as a meniscus, may swing in all directions around pins 13, 14. Said springs adapt to whichever molds assembly including curves or various plains and by means of the swinging of the small plates, allow a perfect adherence, likely to exert an even pressure, very useful to the production ' ~ ' . ~. ., , , , ;. , ~ .. ~ . .
3~ ~
of regular polymers. (Fig. 19 and Fig. 20).
EXAMPLE NR. 25 Spring3 as in Example N 24 above, but provided with only one small saucer. (Fig~ 21).
OPENING OF T~E MOLDS - The lens mad.e of C~-39 and its copolymers, is strongly adherent to the casti:ng mold, thus the separation from each other is a problem dif~icult to solve, particularly in the frame of the present invention. In fact, as the diameter of the polymer obtained, is practically equal to the molds, it is impossible to achieve a mechanical separation by means of a wedge or a similar tool. In the frame of the present invention it was discovered that ultrasounds in the range of 20-70 KHertz, induced in a tank filled with water, in which the molds had been immersed, after the polymerization of their content, caused the separation of the polymers from the molds.
.. EXAMPLE NR. 26 To separate the polymer from the glass lenses, forming the molds,.the latter were immersed in warm water baths, after which ultrasonic frequencies in the range of 20-70 KHertz were induced.
In all cases, after some minutes, the polymer separated from the molds. The duration of the operation depended upon the bath tem.perature: it was shorter for an higher temperature and vice versa.
; EXAMPLE NR. 27 To carry out at the same time the separation of the polymer obtained from the glass lenses constituting the molds, and a first washing up of the latter, the molds were immersed in warm baths of water solution of any type of cleansing usbstance (such as detergent, detersive, degreasing, emulsify-ing or saporification agent, solvent, acid or alcaline sub-stance). In every case, within some minutes from the induction :`~
to the bath of ultrasonic frequencies, in the range of 20-70 KHertz, the polymer separated from the molds: the relation:
duration of the operation/bath temperature was the same as indicated in the Example N 26.
From the above it appears evident that the described process and/or the means object of the present invention, which allow the production of quality lenses or other optical means, made of CR-39 and its copolymers, may be directly or indirectly related to the whole field of applications of casted homo- :
polymers and copolymers with reference to the casting of whichever product, and the applicability or the selection of a whichever polymerizable resin. It also clearly appears that the examples - though referring to specific realizations of the present invention, cannot be considered as limiting the latter.
: It is underlined that the process as a whole, attains in a synergistic manner, the advantages obtainable by means of each described operation or means, with respect to their individual Euncti~s ' '' '~
" ',' ; :~
,
Claims (13)
1. A polymerization process for producing, by way of molding and continuous compensation, lenses and optical means, from a polymerizable thermohardening plastics material, said process comprising the steps of:
- forming a tubular sleeve of a plastic material substantially indeformable, said plastic material being chemically compatible with said polymerizable material and thermically stable at the temperature of polymerization, - positioning mold halves within said sleeve at the required distance from each other, so that they define, with the lateral wall of the sleeve, a cavity having a diameter equal to that of the mold halves, the position of each mold half with respect to the sleeve being only kept by friction of the mold half rim, over the sleeve wall, - forming outside of said cavity a compensation reservoir communicating with said cavity through at least a preformed passage way, - introducing into the cavity, through said preformed passage way, catalysed polymerizable thermohardening plastics material until said cavity is completely filled and said compensation reservoir is partially filled, - submitting said mold to homogeneous heating to thereby cause a passage of polymerizable material in excess from the cavity of the mold, into the compensation reservoir, during the state of expansion of the polymerizable material, and a passage in the opposite direction during the subsequent stage of shrinkage of the polymerizable material, until the gel stage is reached, - continuing the heating of the mold until the polymerization of the polymerizable material is completed, the final shrinkage of the latter, from the beginning of the gel stage, being only compensated through the approaching of the mold halves to each other, - removing the two mold halves from the lens thus obtained when the polymerization of the polymerizable material has been completed.
- forming a tubular sleeve of a plastic material substantially indeformable, said plastic material being chemically compatible with said polymerizable material and thermically stable at the temperature of polymerization, - positioning mold halves within said sleeve at the required distance from each other, so that they define, with the lateral wall of the sleeve, a cavity having a diameter equal to that of the mold halves, the position of each mold half with respect to the sleeve being only kept by friction of the mold half rim, over the sleeve wall, - forming outside of said cavity a compensation reservoir communicating with said cavity through at least a preformed passage way, - introducing into the cavity, through said preformed passage way, catalysed polymerizable thermohardening plastics material until said cavity is completely filled and said compensation reservoir is partially filled, - submitting said mold to homogeneous heating to thereby cause a passage of polymerizable material in excess from the cavity of the mold, into the compensation reservoir, during the state of expansion of the polymerizable material, and a passage in the opposite direction during the subsequent stage of shrinkage of the polymerizable material, until the gel stage is reached, - continuing the heating of the mold until the polymerization of the polymerizable material is completed, the final shrinkage of the latter, from the beginning of the gel stage, being only compensated through the approaching of the mold halves to each other, - removing the two mold halves from the lens thus obtained when the polymerization of the polymerizable material has been completed.
2. The process in accordance with claim 1, wherein said polymerizable thermohardening plastics material is diethylen-eglycol-bis-allyl-carbonate.
3. The process in accordance with claim 1, wherein diethyleneglycol-bis-allyl-carbonate and its copolymers are used as said polymerizable thermohardening plastics material.
4. The process in accordance with claim 1, wherein diethyleneglycol-bis-allyl-carbonate is used as said polymer-izable thermohardening plastics material, catalysed with iso-propyl dicarbonate-peroxide.
5. The process in accordance with claim 1, wherein said polymerizable thermohardening plastics material is diethyl-energlycol-bis-allyl-carbonate catalysed with isopropyl dicar-bonate-peroxide, to which, 2-(2-hydroxy-5-methyl-phenyl) benzo-triazole is added, as an U.V. absorbed additive.
6. The process in accordance with claim 1, wherein the catalysed polymerizable material is submitted to a thermic cycle of 15 hours with a gradual thermic increase of from about + 40°C to 110°C.
7. The process in accordance with claim 1, wherein the compensation reservoir is obtained through modification of a por-tion of the tubular sleeve.
8. The process in accordance with claim 1, wherein the compensation reservoir is put close to the exterior of the tubular sleeve, in a position corresponding to the cavity delimited by the two mold halves.
9. The process in accordance with claim 1, wherein the axis of the tubular sleeve is kept vertical and the compensation reservoir is obtained within the tubular sleeve, above the higher mold half.
10. The process in accordance with claim 1, wherein after the gel stage of the polymerizable material has been reached, compression springs are applied to the two mold halves.
11. The process in accordance with claim 10, wherein the compression springs which are applied to the mold halves, comprise at least a contact saucer, shaped as a meniscus, adapted to swing in each direction around an articolation pin.
12. The process in accordance with claim 1, wherein the removal of the lens from the mold halves is obtained by means of the immersion in a warm water bath, submitted to ultrasonic frequencies, comprised between 20 and 70 KHz.
13. The process in accordance with claim 1, wherein the water bath is a solution of a detergent substance.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT23319/78A IT1094754B (en) | 1978-05-12 | 1978-05-12 | PROCESS FOR THE MANUFACTURE BY CONTINUOUS COMPENSATION CASTING OF LENSES OR OPTICAL MEDIA IN POLYMERIZABLE SYNTHETIC RESINS |
| IT23319A/78 | 1978-05-12 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1135913A true CA1135913A (en) | 1982-11-23 |
Family
ID=11206027
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000327575A Expired CA1135913A (en) | 1978-05-12 | 1979-05-11 | Production process of lenses made of polymerizable synthetics resins |
Country Status (22)
| Country | Link |
|---|---|
| JP (1) | JPS54149765A (en) |
| AT (1) | AT391296B (en) |
| AU (1) | AU526381B2 (en) |
| BE (1) | BE876149A (en) |
| BR (1) | BR7902929A (en) |
| CA (1) | CA1135913A (en) |
| CH (1) | CH641402A5 (en) |
| DE (2) | DE2954548C2 (en) |
| DK (1) | DK162590C (en) |
| ES (1) | ES480497A1 (en) |
| FR (1) | FR2425314A1 (en) |
| GB (1) | GB2021474B (en) |
| GR (1) | GR67597B (en) |
| HK (1) | HK73587A (en) |
| IE (1) | IE48438B1 (en) |
| IL (1) | IL57252A0 (en) |
| IT (1) | IT1094754B (en) |
| LU (1) | LU81249A1 (en) |
| MX (1) | MX151517A (en) |
| NL (1) | NL7903713A (en) |
| NO (1) | NO162009C (en) |
| SE (1) | SE432219B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| IT1191569B (en) * | 1986-02-28 | 1988-03-23 | Nuova Sil Spa | MOLD FOR THE PRODUCTION THROUGH CASTING OF ORGANIC LENSES |
| US6511311B1 (en) | 1998-09-30 | 2003-01-28 | Novartis Ag | Lens mold carriers |
| ATE229427T1 (en) * | 1998-09-30 | 2002-12-15 | Novartis Erfind Verwalt Gmbh | CARRIER FOR LENS SHAPES |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1166582A (en) * | 1955-12-30 | 1958-11-13 | Combined Optical Ind Ltd | Method and apparatus for molding lenses and other precision optical elements |
| FR1204627A (en) * | 1958-04-25 | 1960-01-27 | Lentilles Ophtalmiques Special | Improvements in the manufacture of optical and ophthalmic lenses in thermosetting synthetic resins |
| US3171869A (en) * | 1959-12-07 | 1965-03-02 | Bausch & Lomb | Process for manufacturing curved optical articles |
| US3251908A (en) * | 1962-12-05 | 1966-05-17 | Computing Devices Canada | Method and apparatus for making a curved surface |
| DE2303551C3 (en) * | 1973-01-25 | 1981-05-14 | Transformatoren Union Ag, 7000 Stuttgart | Plant for the production of castings from synthetic resin in the die casting process |
| DE2312934C3 (en) * | 1973-03-15 | 1980-01-24 | Et. Dentaire Ivoclar, Schaan (Liechtenstein) | Method and device for the production of dental prostheses made of plastic |
| GB1511901A (en) * | 1974-05-06 | 1978-05-24 | Bausch & Lomb | Forming lenses and lens blanks |
| US4008031A (en) * | 1975-08-22 | 1977-02-15 | Weber Hermann P | Apparatus for injection molding lenses |
-
1978
- 1978-05-12 IT IT23319/78A patent/IT1094754B/en active
-
1979
- 1979-05-04 AT AT0334779A patent/AT391296B/en not_active IP Right Cessation
- 1979-05-04 CH CH419379A patent/CH641402A5/en not_active IP Right Cessation
- 1979-05-07 DE DE2954548A patent/DE2954548C2/de not_active Expired - Fee Related
- 1979-05-07 GR GR59036A patent/GR67597B/el unknown
- 1979-05-07 DE DE19792918323 patent/DE2918323A1/en not_active Ceased
- 1979-05-07 NO NO791516A patent/NO162009C/en unknown
- 1979-05-08 GB GB7915824A patent/GB2021474B/en not_active Expired
- 1979-05-08 SE SE7904019A patent/SE432219B/en not_active IP Right Cessation
- 1979-05-09 BE BE6/46827A patent/BE876149A/en not_active IP Right Cessation
- 1979-05-10 DK DK195179A patent/DK162590C/en active
- 1979-05-10 MX MX177595A patent/MX151517A/en unknown
- 1979-05-11 BR BR7902929A patent/BR7902929A/en unknown
- 1979-05-11 FR FR7912078A patent/FR2425314A1/en active Granted
- 1979-05-11 NL NL7903713A patent/NL7903713A/en not_active Application Discontinuation
- 1979-05-11 ES ES480497A patent/ES480497A1/en not_active Expired
- 1979-05-11 CA CA000327575A patent/CA1135913A/en not_active Expired
- 1979-05-11 IL IL57252A patent/IL57252A0/en not_active IP Right Cessation
- 1979-05-11 LU LU81249A patent/LU81249A1/en unknown
- 1979-05-12 JP JP5763979A patent/JPS54149765A/en active Pending
- 1979-05-14 AU AU47032/79A patent/AU526381B2/en not_active Ceased
- 1979-08-08 IE IE1245/79A patent/IE48438B1/en not_active IP Right Cessation
-
1987
- 1987-10-07 HK HK735/87A patent/HK73587A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| IL57252A0 (en) | 1979-09-30 |
| SE432219B (en) | 1984-03-26 |
| DE2918323A1 (en) | 1979-12-06 |
| ES480497A1 (en) | 1979-12-16 |
| DK195179A (en) | 1979-11-13 |
| DK162590B (en) | 1991-11-18 |
| DE2954548C2 (en) | 1992-07-23 |
| AT391296B (en) | 1990-09-10 |
| IE48438B1 (en) | 1985-01-23 |
| GR67597B (en) | 1981-08-31 |
| GB2021474A (en) | 1979-12-05 |
| CH641402A5 (en) | 1984-02-29 |
| FR2425314B1 (en) | 1984-01-13 |
| IT7823319A0 (en) | 1978-05-12 |
| ATA334779A (en) | 1990-03-15 |
| NO162009B (en) | 1989-07-17 |
| IT1094754B (en) | 1985-08-02 |
| NO791516L (en) | 1979-11-13 |
| AU4703279A (en) | 1979-11-29 |
| NO162009C (en) | 1989-10-25 |
| AU526381B2 (en) | 1983-01-06 |
| SE7904019L (en) | 1979-11-13 |
| BR7902929A (en) | 1979-12-04 |
| JPS54149765A (en) | 1979-11-24 |
| HK73587A (en) | 1987-10-16 |
| DK162590C (en) | 1992-04-06 |
| LU81249A1 (en) | 1979-09-10 |
| FR2425314A1 (en) | 1979-12-07 |
| BE876149A (en) | 1979-09-03 |
| NL7903713A (en) | 1979-11-14 |
| MX151517A (en) | 1984-12-10 |
| IE791245L (en) | 1979-11-12 |
| GB2021474B (en) | 1982-08-11 |
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