CH641402A5 - PROCEDURE FOR MAKING THROUGH CASTING A COMPENSATION CONTINUE LENS OR OPTICAL IN SYNTHETIC RESINS curable. - Google Patents

Description

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CLAIMS 12. Procedure according to claim 1 characterized

1. Manufacturing process by compensating casting from the fact that the detachment of the lens from the continuous half-release of lenses or optical means in synthetic resin resins by immersion in hot aqueous bath subjected to cold setting agents, characterized by the fact that: ultrasonic quences between 20 and 70 KHz.

- a tubular sheath of plastic material is formed. 5. Method according to claims 1 and 12, characteristically indeformable, chemically compatible with the fact that the aqueous bath is constituted by a monomer solution and thermally stable at the polyurethane temperatures. of detergent.

authorization,

- molds are positioned within the sheath as desired -

at a distance from each other, so that they delimit with the 10

side wall of the sheath itself a cavity of equal diameter The present invention relates to a process for the le to that of the half-molds, the position of each half-mold manufacturing by means of continuous compensation casting of lenses with respect to the sheath being maintained only by friction or optical means in polymerizable synthetic resins.

along the edges, For decades now, the technological world has addressed the

- a tank is formed outside this cavity with its attention to the search for forming methods through the municant with the cavity itself through at least one opening polymerization in a mold of one or more monomers capable of being preformed, to provide solids endowed with particular characteristics.

- it is introduced by pouring into the cavity, through the optical industry in this direction for the so called preformed opening, thermosetting monomer cata- production of lenses or other optical means and in practice the various ones until filled the cavity itself and partially, the Serbian- 20 techniques tend to overcome the obstacles that the process of clearing, merizzation poses both at the level of chemical characteristics-

- the pro-physical mold of the object related to the theoretical optimum polymer is homogeneously heated, both calling for the passage of the excess monomer from the cavity of the level of chemical-physical characteristics of the object related to the mold to the compensation tank during the expansion of the monomer to the polymer obtained, as in the geometry of the object, and the passage in the opposite direction during the 25. These techniques have particularly addressed the subsequent contraction, up to the gel phase, of thermosetting polymers which, compared to thermoplastics I offer-

- polymerization of the monomer is continued, the physical and chemical characteristics and advantages of which are more suitable for contraction from the beginning of the gel phase are compensated for use as optical means, for example lenses. The monomer only by mutual approach of the two half-molds, constituting the now generalized raw material and the

- at the end of the polymerization, it separates from the two half-prints diethylene glycol-bis-allyl carbonate (and its copolymers) of formula: plus the lens obtained.

2. Process according to claim 1 characterized = CH2

from the fact that diethylene glycol-bis-O is used as monomer

allyl carbonate (CR-39). CH2-CH2-O-CH-O-CH2-CH2-CH

2. Process according to claim 1, characterized by the fact that diethylene glycol-bis- better known with the CR-39 brand is used as monomer, which is added with a cata-allyl carbonate and its copolymers. liiser, or rather a free radical initiator, allows

4. Process according to claims 1 to 3, characterized by the gradual homopolymer or cap polymerization. The fact that isopropyl peroxydicarbonate of formula: diethylene glycol-bis-allyl-carbonate catalyzed with isopropyl- is used as monomer

peroxydicarbonate. CH3 ,. ^ / CH3

Method according to claims 1 to 4 characters - _ ^> CH-0-C0-0-0-C0-0-CHC ^ '

deriving from the fact that CH3 ^ -CH3 is used as monomer

diethylene glycol-bis-allyl carbonate catalyzed with isopropyl peroxycarbonate with the addition of 2- (2-hydroxy- 5-methylphenyl) benzotria- 45 known as I.P.P. it is the preferred initiator in that it allows it as a UV absorber. polymerization at lower temperatures and in more cycles

6. Process according to claims from 1 to 5 short characteristics if compared to benzoyl peroxide or to other peroxides oxidized by the fact that the catalyzed monomer is subjected, and equally usable. In practice, the forming methods of optionally additives, at a thermal cycle of 15 hours with a lens in CR-39 or its copolymers, involve the gradual introduction-thermal excursion from + 40 ° C to + 110 ° C. I know of the monomer or catalyzed in liquid or prepolime form

7. Method according to claims 1 to 6, characterized up to the syrupy between two glass lenses spaced apart by the fact that the compensation tank is obtained from them by a T-seal and held together by a spring. The by deformation of a portion of the tubular sheath. gasket spacer can be shaped according to

8. Process according to claims from 1 to 6, characteristics of the two lenses to ensure their sealing and distanced from the fact that the compensation tank is applied loose or deform elastically for the same purpose, externally to the tubular sheath corresponding to the cavity Considered that the catalyzed monomer, introduced in the form delimited by the two half-molds. liquid in the molds thus formed, solidifies at the end of a

9. Process according to claims from la 6, thermal or radiant character, causing strong retractions, tridified by the fact that the compensation tank is obtained dimensional (14% in the case of the homopolymer CR-39) can be attached inside the sheath tubular, above the half-mold 60 marsi that another function of the spring is to make compresses-upper. re the spacer from the lenses making up the mold so

10. Process according to claims 1, characterized in this way, up to the intermediate gel stage, to avoid that pressure springs are applied to the two half-molds, losses of liquid monomer from the mold, while subsequently after reaching the gel phase. after the gel phase the pressure exerted will have the function of

11. Process according to claims 1 and 10, characterized by deforming the thermoplastic or elastic spacer, in order to make it improper by the fact that pressure springs are applied which are said to act as an obstacle to the mold adhesion-at least one plate in the shape of an oscillating meniscus in all polymers. Said deformation can be understood both as directions on the relative fixing pin. squeezing the spacer or as an expansion of the seal

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nition. The mold-polymer adhesion is necessary to avoid possible breakages of the polymer or of the mold due to strong tensions that occur in the shrinking polymer or to prevent at least on the useful surfaces of the polymer air infiltrations which, inhibiting the polymerization, could cause irreparable damage.

The lenses in CR-39 or its copolymers that are obtained can have imperfect perimeters for air bubbles. Air passages, even after the gel phase, cause bubbles and voids or a soft perimeter band of the polymer and so also the possible chemical reactivity between the material constituting the gasket and the catalyzed monomer. However, the significant reduction in the diameter of the lens in CR-39 or its copolymers obtained with respect to the diameter of the lenses making up the mold is common to all processes, and this is due to the following causes:

a) the internal cavity of the mold is reduced by the space occupied by the tongue which acts as a spacer;

b) the retraction of the polymer being three-dimensional also takes place on the perimeter further reducing the diameter, especially for the negative or diverging lenses;

c) any perimeter defects (air bubbles, sucks or band of soft polymer) further reduce the useful diameter for the depth concerned.

These defects are normally determined in the perimeter, since the dislocation of the molds with the concave part facing upwards is now widespread, while the dislocation of the molds with the convex part upwards would produce the same defects in the center of the polymer lenses making them unusable. By concavity and convexity we mean the external one of the molds themselves.

The opening of the mold takes place by removing the sealing gasket and levering with a wedge in the space previously occupied by the spacer between the two glass lenses, normally adhering to the polymer. This done, a polymeric lens is extracted which is finished at the surface level but highly tensioned due to the shrinkage which will be further subjected to heat treatment in order to obtain the structural distinction.

This treatment, or stress relieving, is normally applied on all molded plastic materials, on glass, on metals. The duration of said treatment, correlated to the temperature necessary to obtain the desired effect, is variable, that is, relative to the state of tension existing on the piece and the degree of polymerization of the polymer.

This first exhibition has the function of roughly indicating the techniques in progress conditioned by the phenomenon of the polymerization process and is the extract of the author's experimental research and documentation referable also to patents, among which we cite US-PS 2.403.112 , US-PS 2.464.062, US-PS 3.171.869, US-PS 3.038.210, US-PS 2.964.501, FR-PS 2.171.073, FR-PS 1.541.889, FR-PS 1.204.627, FR-PS 1.462.519, DE-PS 1.062.003, GB-PS 1,402,573.

This invention takes into account the multiple factors which have hitherto led to technical and / or economic drawbacks in the manufacture of lenses or optical media in CR-39 and its copolymers. This process analyzes, designs and solves the manufacture of lenses or optical media in CR-39 and its copolymers in a completely new way with reference to the basic chemical preparations of the components, the methods and means of polymerization, the geometries of the objects obtainable without reductions, to the possible unification of the polymerization cycles for all thicknesses and to obtaining a polymer calculated according to particular needs of absorption and transmission of electromagnetic energy.

It is believed that the expansion and all the monomers, their capitals, catalysts and initiators can be used as a total or partial series of the claims as obvious of this invention when the same logic, methods and dispositions are applied to the same problems or the same purposes and / or are obtained even partially the results.

Monomer - The diethylene glycol-bis-allyl carbonate or CR-39 monomer is available on the market with a remarkable degree of purity, apparently at about 99.150%. Gas chromatographic analyzes indicate (fig. 1) the presence of allyl carbonate and a substance not clearly known.

During the column separation on the occasion of the aforementioned analyzes it was possible to ascertain that the retention times of the polluting substances are lower than that of the monomer, this indicates a greater volatility. An experimental series was carried out in order to eliminate impurities and it was discovered that by subjecting the monomer to heating at temperatures ranging from 50 ° C to 90 ° C, the disappearance of the allyl carbonate and its possible partial polymerization readable analytically in the area determined by the previously mentioned unknown product which, consequently, can also be considered a polymer of allyl carbonate. This could be ascertained during monomer heating deliberately prolonged over time at a temperature of 90 ° C in static tanks. The monomer analysis denounced a significant increase in the polymer caused by allyl carbonate, since the elimination of allyl carbonate was partially prevented by the static nature of the bath. This established, a monomer refining system was developed as per examples.

Example 1

By gradually heating the CR-39 monomer to temperatures ranging from 50 ° C to 90 ° C, partial elimination of the. allyl carbonate obviously related to the time-temperature-quantity treated ratio. Lower temperature = longer duration of treatment / higher temperature = shorter duration of treatment. As an indication, the following is specified: CR-39 monomer quantity = 1 liter; average thermal value 70 ° C for 4 hours plus gradual heating and cooling times from / to room temperature. Titer of the treated monomer: 99.158% (fig. 1); Titer of the monomer obtained: 99.484% (fig. 2).

Example 2

By gradually heating the CR-39 monomer at temperatures ranging from 50 ° C to 90 ° C, activating the baths with mixing in order to homogenise and accelerate the process of eliminating the allyl carbonate if the partial elimination has obviously been obtained at all temperatures related to time-temperature-quantity ratios treated as in example 1.

As an indication, the following is specified: quantity of treated CR-39 monomer = 1 liter; average thermal value 70 ° C for 4 hours plus gradual heating and cooling times from / to room temperature. Titer of the treated monomer: 99.158% (fig. 1); Titer of the monomer obtained: 99.713% (fig. 3).

Example 3

By heating with the methods described in Example 1 but by carrying out the operations under vacuum, the following was obtained: quantity of treated CR-39 monomer = 1 liter; average thermal value 70 ° C for 4 hours plus gradual heating and cooling times from / to room temperature. Titer of the treated monomer: 99.158% (fig. 1); Title of the monomer obtained: 99.686 (fig. 4).

Example 4

By heating with the methods described in example 2, but by carrying out the operations under vacuum, the following was obtained: treated monomer CR-39 = 1 liter; average thermal value

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70 ° C for 4 hours plus gradual heating and cooling times from / to room temperature. Titer of the treated monomer: 99.158% (fig. 1); Titer of the monomer obtained: 100% (fig. 5).

Example 5

By heating with the methods described in Examples 1, 2, 3, 4, the total dehydration of the monomer was also obtained. Spectrophotometric analyzes in the visible range from 400 to 700 nm obtain exceptional linearity and transmission from the CR-39 monomer thus purified.

Initiator - Isopropyl peroxycarbonate or I.P.P. of the trade is added to the CR-39 monomer in the average percentage of 3%, an almost generalized standard. All procedures therefore refer to this percentage even if it is possible to use higher or lower percentages for particular needs. The I.P.P. Even though it can be considered pure as an industrial product that is difficult to manipulate, it actually contains traces of water and free chlorine ions.

This is detectable by infrared spectrophotometric analysis (fig. 6). In order to start an experimental series aimed at ascertaining the influence of chlorine ions on the polymerization within the scope of the present invention, isopropyl peroxycarbonate was synthesized by means of a reaction between sodium peroxide and isopropyl chlorate-formate previously purified to 99.99%. Once obtained, the product was used after 1, 2, 3, 4, 5 washings in H2O. Each of the washes corresponded to a relative decrease in chlorine ions. By polymerizing the CR-39 monomer with the addition of 3% isopropyl peroxycarbonate from the above wash sequence, a clearly yellowish polymer corresponding to the use was obtained according to a gradual thermal cycle of 15 hours from + 40 ° C to + 110 ° C. percar-bonate washed once, yellow / 2 washes, pale yellow / 3 washes, straw / 4 washes, colorless / 5 washes. It could thus be established how the more accentuated presence of chlorine ions determines the yellowing of the polymer.

Each time the isopropyl peroxydicarbonate was washed, a lighter fraction related to the same product partially degraded by loss of oxygen was separated. In order to obtain an isopropyl peroxydicarbonate purified as much as possible from free chlorine ions and from fractions partially degraded by loss of oxygen, the following steps were taken:

Example 6

They were melted in a refrigerated bain-marie + 9 ° C 100 gr. by I.P.P. of the trade having a melting point of + 8 ° C. H2O refrigerated at + 9 ° C was added in which a few drops of pyridine had been dissolved. After stirring and settling the phases were separated. We proceeded to wash twice with treated H2O isopropyl peroxycarbonate, taking care to separate not only the water but also the lighter fraction of the percarbonate corresponding to the partially degraded or oxygen-depleted product. At this point the I.P.P. it was purified (fig. 7).

Example 7

By refreezing the I.P.P. purified according to the method described in Example 6 and leaving to reflow resulted in a melting temperature of + 9 ° C instead of + 8 ° C corresponding to the starting product.

Example 8

Two specimens prepared with the same CR-39 monomer and under the same polymerization conditions, catalyzed respectively with the addition of I.P.P. commercial 3% and I.P.P. purified according to the method described in example 6

denounced the following differences: at 53 ° C after 4 hours of gradual thermal rise induced by 40 ° C the monomer was present in the polymer in the percentage of 52% in the specimen with added I.P.P. commercial while the method described the monomer present in the polymer was 34%. This indicates that it was achieved with the use of I.P.P. without greater catalytic activity which in other words is the equivalent of the possibility of reducing the percentage quantities with respect to the P.P.P. commercial and times and degrees of heating to obtain a polymer value X. Furthermore, the specimen produced by I.P.P. cleansed it was perfectly colorless.

Additives - The monomers are normally added with UV absorbers to protect the polymers from the degradation caused by these radiations. Said UV absorbers often present solution difficulties with consequent negative effects both as regards their homogeneous distribution at the moment, both for the optical effects of diffraction or dispersion that a bad solution and distribution could cause, and for the yellow, yellow coloring effects. greenish, orange-yellow or transmission interference in the visible electromagnetic field, induced to the polymer in a more or less pronounced way, according to the qualitative and quantitative choice. With reference to the present invention, 2- (2-hydros-si-5-methylphenyl) benzotriazole has been selected as an absorber. An experimental series was carried out aimed at establishing the optimal quantity of said UV absorber to be added to the CR-39 monomer with particular regard to the interferences that said addition can generate in the polymer as regards the transmission of visible light and the methods of solution. This was done as follows:

Example 9

The perfect solution and distribution of 2- (2-hydroxy-5-methylphenyl) benzotriazole was obtained in the chosen percentage of 0.0125% in the monomer CR-39 pure or catalyzed with I.P.P. inducing the container ultrasonic frequencies between 20 and 70 KHertz. The chosen percentage of 0.0125% of 2- (2-hydroxy-5-methylphenyl) benzotriazole resulted in a good absorption in the CR-39 polymer in the UV field while the transmission in the visible is almost linear on specimens of 4 m / M of thickness (fig. 8).

Example 10

By ultrasound the perfect solution and distribution of 2- (2-hydroxy-5-methylphenyl) benzotriazole in the monomer CR-39 pure or catalyzed with I.P.P. in the chosen percentage of 0.0100%. The percentage of 0.0100% of additive resulted in spectra in the polymer almost similar to that described in Example 9 on specimens of 6 m / m thickness.

Example 11

By ultrasound the perfect solution and distribution of 2- (2-hydroxy-5-methylphenyl) benzotriazole in the monomer CR-39 pure or catalyzed with I.P.P. in the chosen percentage of 0.0150%. The percentage of 0.0150% of additive determined in the polymer spectra almost similar to that described in Example 9 on specimens of 2 m / m thickness.

Example 12

By ultrasound the perfect solution and distribution of very high percentages with respect to those described in Examples 9, 10, 11 of 2- (2-hydroxy-5-methylphenyl) benzotriazole in pure monomer 0 catalyzed with I.P.P. or with benzoyl peroxide such as to allow the preparation of easily controllable concentrates which were then diluted in large quantities

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quantity of pure monomer or catalyzed at the percentages required - Example 17

derate. 2 or more glass lenses were slid inside a tubular band as in example 16 of calculated diameter Example 13 so as to produce elasticity or sliding friction in the

Catalysis - By mechanical stirring, a CR-39 purified and dehydrated spacer-monomer was previously introduced or formed with the de- tore modalities of desired height and of a minimum thickness such as to be allowed in examples 1, 2, 3, 4 with 3% of IPP purified to stop the sliding of the lenses (fig. 10 in which:

from example 6 and with 0.0125% of 2- (2-hydroxy-5-methylphenyl) 1 = tubular band; 2 = lenses; 3 = cavity; 4 = spacer), benzotriazole as per examples 9 and 12, filtering everything in decompression. io Example 18

2 or more glass lenses were slid inside Example 14 with a tubular band as in example 16 of almost diameter

By means of ultrasonic induction, monomer equal to the same was mixed in which CR-39 had been previously introduced or purified and dehydrated in the manner described in the form of a spacer as in Example 17.

examples 1, 2, 3, 4 with 3% of I.P.P. purified as per example 15

pious 6 or with benzoyl peroxide and with 0.0125% of Example 19

2- (2-hydroxy-5-methylphenyl) benzotriazole as per examples 9 and 12 The molds prepared as per examples 16, 17, 18 were filtered in total under decompression. filled with catalyst CR-39 monomer as per examples 13,

14 and displaced horizontally with the convex part facing Example 15 20 upwards. Catalyzed monomer was added to the channel

With monomer CR-39 catalyzed and additivated as per the perimeter consisting partly of the surface of the lens super-examples 13 and 14 and subjected to a thermal polymerization cycle and partly from the inner wall of the tubular (fig. Ile fig. clear, almost colorless. Said po 12, respectively perspective view and sectional view, in limers compared to a preparation of the normal type, have: 1 = tubular band; 2 = lenses; 5 = catalyzed monomer), had a course of faster and more uniform polymerization 25

with reference to the reactive saturation in times X for cycles Example 20

thermal Y and for thickness Z. Said polymers also exhibited the molds prepared as per examples 16, 17, 18 were exceptional physico-chemical characteristics detected by analyzes filled with monomer CR-39 catalyzed as per examples 13, si thermal differential colorimetric and tests of chemical inertia and displaced horizontally with the concave part facing ver-ca. From all the examples it is easy to see how the methods described 30 are high. The catalyzed monomer was added to the cavity to be the improvement or the variant of the same techniques of the upper lens until it reaches the inner wall of the gradually applied while the doses correspond to values that are post-tubular (fig. 13 and fig. 14 where: 1 = tubular band; 2 = lenses; they have been varied while adopting the same techniques (the end of the 5 = catalyzed monomer).

the author in the detailed description of the invention is

that of referring to the same claims the intersection of the 35 Example 21

techniques, doses and / or their partitioning. The states prepared as per examples 16, 17, 18 have been

Continuous compensation principle of the molds - The re-filled with CR-39 monomer catalyzed as per examples 13, traction of the CR-39 polymer and its copolymers determines to re-15 and displaced horizontally as from examples 19, 20. The bands groove the the need to apply mostly tubular empirical devices have been equipped with a tank, or shaped in such a way to buffer a vast negative phenomenology. Normally, connected to the internal cavity of the molds which has been polymerized at variable thermal cycles, it is filled with catalyzed monomer. Said tank is conditioned by the thicknesses of the polymer while other devices constructed covering the perimeters totally or partially refer to the means for assembling the molds and / or tro of the tubular band outside and / or inside (fig. A intermediate manipulation As a rule, there is a tendency to lengthen 15 and Fig. 16 in which: 1 = tubular band; 2 = lenses; 5 = also monomer strongly the thermal cycles for increased thickness of the catalyzed material; 6 = tank).

I will file and keep the molds filled with monomer catalyzed at low temperature (+ 40 ° C) for a long time on- Example 22

to slow down the reactive kinetics and decrease as far as possible. The molds prepared as per examples 16, 17, 18 were negative phenomenology determined by the retraction of the poly-filled monomer CR-39 catalyzed as per examples 13, mere. Within the scope of the present invention, 14 and vertically located have been thought of. The external tubular bands have solved the problem by means of a continuous compensation of the tea equipped, or shaped in this way, with a communicating mold tank with catalyzed monomer capable of replacing the voids with the internal cavity of the molds. Said tank was determined by the retraction of the polymer in formation, which was in turn filled with catalyzed monomer (fig. 17 in which:

exploiting the fact that the CR-39 monomer and its copolymers, 1 = tubular band; 2 = lenses; 5 = catalyst monomer; with the addition of a peroxide or percarbonate catalyst poly ss 6 = tank).

it merizes only partially and in any case very slowly in the presence of air, maintaining its fluidity for a long time. So- Example 23

No molds have been assembled for the formation of optical lenses with all the molds prepared and located in the ways described in the following: previous examples whose internal cavities corresponded to the geometries of all types of lenses, neutral, convergent, divergen-Example 16 ti, cylindrical, lenticular, bifocal, prismatic etc. They were

2 or more glass lenses were slid inside the oven subjected to the same thermal cycle of 15 hours (fig. 18). a tubular band in polyethylene or other non-reactive material The cut that appears on the cycle corresponds to the moment in which, with the catalyzed monomer, with a diameter calculated as described below, the springs were applied to produce elasticity or sliding friction such as to allow the molds, that is, after the monomer had passed the phase of fixing the lenses at the desired distance so as to gel. Perfectly polymerized lenses have been obtained and by creating one or more cavities determined by the curvature of the finished surfaces, of each curve and thickness and pres-des diameter (fig. 9: 1 = tubular band, 2 = lenses, 3 = cavity). as long as it is equal to the diameter of the glass lenses constituting the

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molds (single or multiple) with a very slight reduction by 0.7%.

Thus, the function exercised by the continuous compensation of monomer catalyzed through the methods and means described in the previous examples remained experimentally confirmed, which determined a continuous flow between the outside and the inside of the polymerizable monomer molds, compensating for the retractions, preventing sucks and / or formation of air bubbles and consequent polymer-mold detachments. The external-internal flow was made possible by preformed passages or by capillarity. The polymers obtained were particularly homogeneous.

Self-displacement spring - On several CR-39 lens productions on the market there are voltages readable in polarized light which appear to be immovable even with heat treatment of polymers. Considering the need, in the context of the present invention, to apply pressure on the lenses making up the molds after reaching the polymer gel phase, it was decided to use a spring capable of adapting to any curved or flat surface and of dislocating with a contact homogeneous on the entire support surface in order to avoid pressure peaks capable of inducing breaks both in the molds as in the polymers or particular tensions on the polymers themselves.

Example 25

Springs as in example 24 but with only one plate (fig. 21).

Mold opening - The release of the lenses in CR-39 and its copolymers, which are strongly adherent to the molds, poses a considerable problem especially with reference to the present invention since, since the polymer formed with a diameter almost equal to the molds, it is impossible to perform actions mechanical through wedges or other. Within the scope of the present invention it has been discovered that the action of ultrasounds comprised between 20 and 70 KHertz induced in aqueous baths in which the molds had been immersed after polymerization of their content, determined their easy detachment.

15 Example 26

In order to detach the glass lenses making up the molds from the polymer obtained inside them, they have been immersed in hot aqueous baths inducing ultrasonic frequencies between 20 and 70 KHerz. In any case, after some 20 minutes the polymer was detached from the molds while the duration of the treatment was always relative to the temperature of the baths. More temperature = less time / less temperature = more time.

Example 24

Springs have been built which are easily applied to the compression molds of the levers 7, 8 which determine the elastic opening of the pressers 9, 10 which are made up of meniscus-shaped plates 11, 12 applied so as to be able to oscillate on the pins 13, 14 in all directions. These springs have allowed adaptability to any assembly of molds with different curves or planes and have determined, thanks to the possibility of oscillating the plates, a perfect adherence capable of exerting a homogeneous pressure which has proved to be very useful for obtaining regular polymers (fig. 19 and fig. 20).

25 Example 27

In order to detach the glass lenses making up the molds from the polymer obtained inside them and at the same time obtain a first washing of the molds, they have been immersed in hot baths consisting of aqueous solutions 30 of any detergent, detergent, degreaser, saponifying, emulsifying, solvent, alkaline or acid, inducing ultrasonic frequencies between 20 and 70 KHz in the baths.

In any case, after a few minutes the polymer was detached from the molds while the duration of the treatment was 35 relative to the temperature of the baths as in example 26.

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