DD135623B1 - Process for the production of optical adhesives based on epoxy resin polyaddition products - Google Patents

Description

Tite l: Process for producing optical adhesives

based on epoxy resin polyaddition products

Field of application of the invention

The invention relates to the production of optical adhesives based on epoxy resins, in which the adhesive effect is based on a transition to the solid state by polyaddition reactions at room temperature, the influence of which is also possible by controlled application of elevated temperatures in case of need.

The adhesives of the invention are used for bonding finished, complicated optical components with each other with high accuracy requirements for optical systems, the center thickness-diameter ratios of the individual optical components down to 1:15 and the form factors down to values of> 0.4 be.

In addition, the optical adhesives according to the invention are equally applicable to the temporary attachment of optical Eohteilen and semi-finished products with each other and on support bodies to edit them simultaneously with high precision and productivity individually or in increased numbers zv. can.

C h ar ak t e ri st ik ._d he ja ekann t ші

Since optical adhesives themselves have to be regarded as optical media, the guarantee of optical purity, freedom from streaks and the lowest possible

In the interest of maximum spectral permeability, great importance is attached to self - coloring or largely colorlessness. Even such parameters as refractive index, V value, dispersion and the lowest possible stress birefringence must be ensured in accordance with the demands to be placed on the optical components to be bonded. During the bonding process or during the stabilization and solidification of the adhesive bond no discoloration, turbidity, crystal precipitations, blistering, segregation or the like may occur, which lead to a deterioration of the optical properties.

Closely related to this are some application properties which, in contrast to the multitude of known adhesives for technical-mechanical purposes, are of increased importance in optical adhesives or even must be given in addition. Thus , the viscosity-time or viscosity-temperature dependence comes in the interest of combining a technologically long processing time and an optimally short time to achieve the adhesive effect or stabilization of the bond for optimal technological applicability, to ensure defined, reproducible in close tolerances Adhesive layer thicknesses and to carry out any necessary corrections and adjustments before curing the greatest importance au. In close connection with this, the lowest possible volume shrinkage during the bonding or hardening process leads to the avoidance of mechanical stresses which lead to deformations of the optical surfaces and to stress cracking in the adhesive layer and thus to a reduction of the optical functional parameters.

In the interest of realizing high optical performance parameters and lowering the processing overhead, low processing temperatures are of great importance; the least possible or

do not differ from the room temperature.

Of great technical and economic importance is also the ability to be able to separate the adhesive bonds after a reasonable period of time without high technological complexity and without damaging the optical parts, to correct defective bonding or to supply the parts of Y / eiterbearbeitung.

Of application-related interest is a good stability of the adhesive layer and adhesion to the surfaces of various optical media in conjunction with a functional temperature and climatic stability and resistance to Y / asser xmä organic solvents. On the other hand, it is of technological and economic interest in the case of the separation of adhesive bonds, the surfaces of the optical components with certain selected organic solvents such. For example, acetone, lower alcohols, halogenated carbon env env / ass first off and their mixtures completely free of the adhesive residues and clean.

Finally, the physiological effects of the compounds used as optical adhesives or as their components are of particular importance.

After first known technical solutions for bonding optical components to optical systems or for attaching optical blanks on a support to the shaping processing in the application of hot melt adhesives on & er based on natural resins and synthetic resins (DL-WP 44815; DL-V / P 46 3І9 ) and polymerization adhesives based on . Methacrylic acid esters (DL-WP 44 676) existed, offered epoxy resin-amine hardener combinations as polyaddition or Pol; ykondensationsklebstoff e bee t conditions to meet the requirements in terms of application technology and optical aspects in their entirety optimally.

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It is already known to use aliphatic polyamines which contain at least two nitrogen-bonded hydrogen atoms and at least one nitrogen-bonded carbocyclic radical as curing agents in epoxy resin-amine systern to extend the processing time over the application of unsubstituted, aliphatic polyamines and their to reduce TrübungsanfEiligkeit caused by the effects of moisture. (DT-PS 1,019,461) are of substantial Tfachteil, however, is that these positive effects can only be realized with the aid of a high proportion of organic solvents, as are customary in paint systems, but in optical adhesives harmful.

In order to extend the pot life corresponding to a relatively slow increase in initial viscosity as a function of time in the curing of epoxy resins with amine hardeners, it is also known to use polyamines as curing agents which contain, in addition to secondary, also primary amino groups attached to tertiary carbon atoms are, (DT-PS 1 038 278). The same aim is the use of Cyanalkylierungsprodukten aüphatischer polyamines as a hardener for epoxy resins. (DT-PS 1 034 856; DT-OS 2 164 O99)> However, it is disadvantageous that the extended pot life or slowed G-elbildung is associated with a likewise greatly extended curing time or with the need to perform the curing at elevated temperatures ,

It is also part of the prior art to use N-oxyalkylalkylenepolyamines as amine curing agents for epoxy resins. (DT-PS 1 022 004). The associated advantages of improved physiological safety of these hardeners and hardening at low temperatures, however, are associated with the lack of very rapid curing and short processing time,

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To improve the viscosity-time behavior in terms of extending the processing time with low initial viscosity of the epoxy hard Hart-Gemi se hes, it is also possible to use as amine hardener combinations of at least 3 amine hydrogen atoms containing polyamines with aliphatic-cycloaliphatic-substituted, disecondary amines whose secondary nitrogen atoms are linked by a polymethylene chain of at least 4 carbon atoms. (DT-AS 1 770 539).

In addition, it is known to use N-substituted diamino compounds for the curing of epoxide compounds, in which 3 amino hydrogen atoms are available for curing due to the presence of primary and secondary amino groups. (DT-OS 2 043 141).

All of these known in the art epoxy resin-Aminhärter Sy3teme have the common deficiency, with improvement of certain technological and mechanical properties (extension of the processing time, increase of impact, bending, tensile strength, heat resistance, water resistance, chemical resistance, etc.) that harden them into insoluble, infusible, cross-linked products.

However, the advantageous properties that are relevant for epoxy-resin adhesives for technical-mechanical purposes are not directly related to the parameters and their combinations which are additionally required and described in the beginning especially for optical adhesives. In order to realize these application-technical and optical properties, which are particularly important for Spoxharss amine systems as optical adhesives, simultaneously and to optimum extent, combinations of aliphatic or cycloaliphatic-substituted di- and polyamines with low molecular weight aromatic epoxy base resins have been proposed which, compared to conventional tech-

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nisch-mechanical adhesives have been modified with a very high proportion of monofunctional reactive diluents and plasticizers.

Although these optical adhesives already meet most of the demands made on them, the processing time (pot life) for some of the technological requirements was still too short, the stabilization and solidification of the adhesive compound takes too long and the high proportion of reactive diluents had negative Effects on the physiological properties, causing an increased burden of work safety measures. In addition, the bonds did not correspond to very high optical requirements for very thin optical components with strongly curved surfaces and very different thickness dimensions due to the still too high volume shrinkage especially after exceeding the gel point.

Also known is an optical adhesive based on little or no modified low molecular weight aromatic Epoxidgrundharzen and W- or "K, N'-substituted aliphatic diamines with a relatively long aliphatic chain between the amine functions. (DL-7 / Γ 122 258). Although this already ensures high optical demands and simultaneously improved performance properties, the adhesive compositions without shares of reactive diluents show a not always optimal combination of parameters. So there is z. For example, too high an initial viscosity and an excessive increase in viscosity with respect to the requirements of a flow production of optical systems. This immediately causes further deficiencies that the uniformity of the adhesive thickness is not in the respectively required tight tolerances during the also relatively short Processing time can be guaranteed. The additive used to reduce these disadvantages reactive Ver ~

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thinner and softener leads only to partial success. In many cases these are also physiologically active compounds.

In technologically necessary separations of the bonds, the adhesive layer can not be completely detached from the optical parts and surfaces with the specific organic solvents. For a thermal separation of the adhesive layers relatively high temperatures are necessary, which are harmful for highly complicated optical components. Finally, the diamines used as polyaddition components are relatively difficult to access.

Object of the invention:

The object of the present invention is a process for the production of optical adhesives which reduces or eliminates the shortcomings described, but retains the advantages set forth in Japanese Patent 122,258. Of particular interest is the improvement of the viscosity-time maintenance of the adhesive formulations in terms of a further slower increase in viscosity during the processing time (extended pot life), v / ob egg the time for the stabilization and solidification of the adhesive bond at room temperature according to the technological requirements not extended and the previously technologically necessary storage time of the glued assemblies is even reduced. At the same time the Löslichkeitscigenaohaften and the thermal behavior of the adhesive layers should be improved so that the optical adhesives equally as an optical medium for bonding highly complicated optical components to optical systems, as well as temporary attachment of optical blanks and half-times on support bodies for further shaping processing can be used.

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In addition, the physiological properties to be further improved to reduce the technological burden on occupational health and safety.

Exposition dos ^"7 it ens of He-making;

The object of the invention is, without the known additives of conventional, physiologically active, reactive Verdiinnungsmitteln such. Eliminate as monofunctional Glycidäthern or plasticizers to the epoxy base resins, the causes of the technological and physiological defects and still maintain the favorable optical and performance properties of the known optical adhesives and improve. Particular attention should be paid to the amine component in epoxy adhesives, as most of the amines used to date are physiologically active, leading to allergy and dermatitis.

Surprisingly, and unforeseeably has been found that the physiologically acceptable N, l ^i? Dibenzyl-äthyleiidiamin addition to its action as a Polya & ditionskouponente despite the relatively small length of the aliphatic carbon chain between the amine functions simultaneously acts as a reactive diluent, and an internal plasticizer, and also a reduction in the initial viscosity and causing a slowing of the viscosity increase as a function of time according to the objective,

According to the invention, the object is achieved by a process for the preparation of optical adhesives based on unmodified, low molecular weight, containing at least two epoxy groups per molecule epoxy resins, which i3t characterized in that as a polyaddition component for epoxy resins Ιί, ϋ-Γ-dibenzyl-ethylenediamine If appropriate, further amino polyaddition co-polyones having two amine hydrogenators per molecule in an amount of from 0.5 to 49 mol% or those containing three or more reactive amine-hydrogen salts are also used.

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8toff functions per molecule of 0.5 to 30 mol%, based on the total amount of amine, for improving the technologically relevant parameters of the adhesive approaches in the context of the objective of the invention can be added. Without limiting the process thereby somehow, for such additives according to the invention as amino polyaddition with 2 N-H-Punktionen per molecule, for example, N, lf'-methyl-3-aminomethyl-3,5,5-. trimethylcyclohexylamine and N, N'-dimethyl ~ 2,2,4 (2,4,4) -trimethylhexamethylenediamine-1,6 particularly suitable.

In an analogous manner, as additional amine components with three or more NH functions per molecule z. N-cyclohexyl-2,2,4 (2,4,4) -trimethylhexamethylenediamine-1,6; N-benzylethylenediamine N-cyclohexylpropylenediamine-1,3; To mention J-aminomethyl-S 1 -5-trimethylcyclohexylamine and 2,2,4 (2,4,4) -trimethylhexamethylenediamine-1,6 ,

Execution examples:

The invention will be explained below with reference to exemplary embodiments and a corresponding drawing, wherein on the abscissa the reaction time in minutes, on the left ordinate the dynamic viscosity η in centipoise (cP) and on the right ordinate the dynamic viscosity

did η in the analogous SI units (NsnT), in both cases on a logarithmic scale. The curves 1, 2, 3 and 5 have the following meaning:

Curve 1; Viscosity-time dependence of an optical adhesive according to the invention according to Example 1 using Н, гР ~ І) іЪепзу1-ethylenediamine as a polyaddition component. Curve 2: Viscosity-time dependence of an optical Klebötoffs according to the invention according to Example 2 under Verv / endang a mixture of Ν, Ν'-dibenzyl-ethylenedianine and N-benzyl-ethylenediamine. as polyaddition components.

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Curve 3: Viscosity-time dependence of an optical adhesive according to the invention according to Example 3 using a mixture of N, N'-dibenzyl-ethylenediamine and N, F-dimethyl-3-aminomethyl-3,5,5-trimethylcyclohexylamine as polyaddition components Curve 5: Viscosity-time dependence of a known optical adhesive for comparison according to DL-WP 122 258, Example 1 using N, N'-dimethyl-3-aminomethyl-3,5,5-trimethylcyclohexylamine as polyaddition component *

Important property parameters of the exemplary embodiments of the invention are summarized in the attached table

Example 1.

For б, 1604g2,2-bis- (4'-hydroxyphenyl) -propane diglycidyl ether (epoxy-equivalent 192.8, as measured by WC ROSS, J, Chem. Soc. (London), 1950, 2257), the equivalent Amount of 3.8396 g Ν, Ιί'-dibenzylethylenediamine added. In the course of 10 minutes, the adhesive batch is thoroughly mixed by stirring and is then ready for use at room temperature for bonding optical parts together to form optical assemblies or for temporarily fixing optical blanks on supporting bodies for shaping.

Example . ».

To 3.0848 g of 2,2-bis (4'-hydroxyphenyl) -propane diglycidyl ether

(Epoxy equivalent 192.8 according to ROSS) will be T, 2017 g

(^ mnol) N, N'-dibenzylethylenediamine and 0.3004 g (2mole)

Added H-benzyl-ethylenediamine. In the course of

10 minutes, the Klebstoffansata gat is mixed and then for bonding, as described in Example 1,

ready to use.

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Example 3.

To 8.0892 g of 2,2-bis ~ (4 ^{<hydroxyphenyl)} propane-Diglycidäther (epoxy equivalent 192.8 Ross) 2.6436 g (11 mmol) of N, N'-dibenzyl-ethylenediamine, and 1.9834 g (10 mmol) Ν, ΙΤ ¹ -dimethyl-3-aminomethyl-3,5, S-trimethylcyclohexylamine added. In the course of 10 minutes, the adhesive mixture is well mixed and then ready for bonding, as described in Example 1, ready for use.

Example 4.

An adhesive batch produced according to Example 1 serves for the bonding of optical parts to optical assemblies. Ifach bonding, for example, the following temperature program is maintained during the stabilization and solidification of the adhesive: 2 days prior time at room temperature, 1 day at +40 ⁰ C, 1 day at +45 ⁰ C, 1 day at +50 ⁰ C, for 3 days at + 55 ⁰ C and 4 days at +60 ⁰ C.

On these 17eise glued and cooled in the usual way optics assemblies need to secure their puncture parameters, such as optical and mechanical voltage freedom, temperature and climatic resistance, stable adjustment state u. a. m. no longer the otherwise technologically necessary storage time.

The table summarizes some important performance parameters of the adhesive formulations prepared according to Examples 1 to 3 according to the invention. For comparison, Example No. 5 indicates the analog values of an optical adhesive, which according to DL- ¹ , ?? 122 258, Example 1, using U, li'-dimethyl-3-aminome't: h.yl-3,5,5-trimethylcyclohexylamine (ΪΤ, ΪΡ-dimethyl-IPD) and analogously to the present invention without the addition of reactive diluent (phenyl glycidyl ether). (See DL-WP 122 258, Tab. 1, line 3).

The viscosity measurements were carried out with the device RHEOTEST RV with the cone-and-plate device, where n _t is the dynamic viscosity at 25 ⁰ C after 10 minü-

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Mixing means. The separation temperature was determined on bonded lenses of diameter 30 mm and a center thickness of 2 mm.

The pot life is the time to the beginning of the thread-pulling of the adhesive mixture.

The attached graph illustrates the viscosity-time behavior of the adhesive compositions prepared according to the invention for a reaction period of up to 8 hours, the comparison using curve 5 being based on the same example as in the table.

On the basis of the examples cited, the performance properties of the optical adhesives produced according to the method of the invention improved with respect to the prior art. Particularly noteworthy is first the much lower viscosity n ^. _Q ^ g _t ^, which in combination with the simultaneous strong slowed increase in viscosity as a function of time outstanding, technological processing capabilities, especially in an optical flow production offers. (See attached table and graphical representation of the viscosity-temperature dependence). This ensures reproducible adhesive layer thicknesses over tight processing times within tight tolerances.

These advantages are achieved in contrast to the prior art without the addition of reactive diluents, which are partially physiologically active. Related to this, in turn, is the further technological advantage shown by the table of lowering the separation temperature for the thermal solution of adhesion in the case of corrections or for technological reasons, which up to now could only be achieved with the addition of reactive diluents. It should be noted that in the additional application of aminic polyaddition with more than two N-H-FunktIonen the upper Uengenbegrenaungen invention are to be observed so

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the described advantages of the invention, in particular the thermal separability and the solubility properties in organic solvents are retained.

In the field of optical-physical properties, further advantages can be achieved with the method according to the invention. With interferometric investigation methods, no deformation affecting the imaging quality is detectable on optical active surfaces, which would occur in the case of mechanical stress states in the adhesive layer (plano-glued planar parts of diameter = 30 mm, thickness = 2 mm). Likewise, optical adhesives produced according to the invention are free from stress birefringence. A stress on the bonded optical parts at temperatures of +55 ⁰ G and -40 ⁰ C causes no detectable at low temperature reduction of these advantageous properties.

In addition, it should be emphasized in relation to the chemical properties that in addition to the already mentioned thermicehen separability the adhesive bonds by selected organic solvents such. As acetone, lower alcohols, halogenated hydrocarbons and mixtures thereof are completely soluble after 30 days storage without application of elevated temperatures and without remaining adhesive residues.

The erfindungsgemäß, Ν'-dibenzyl-ethylenediamine used according to the invention as a polyaddition component is used in other context as an additive to medicaments. The physiological safety of this component and the avoidable addition of partially physiologically active reactive diluents due to their use in accordance with the invention have further substantially improved the physiological properties of optical adhesives. Of importance is the easy technical accessibility of N, üH-Diben2yl-ethylenedianiins. The processing of the optical adhesives according to the invention is, in the case of

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door feasible. The technologically necessary storage time can be shortened by using a suitable Temperaturprogranuns without Kachteile.

table

Example ITr. Pot life t fst d J; 25 ⁰ C Viscosity,,"? CcPj at 25 ⁰ C Чѣо ^{+ 4h} · Tgennt emperature Cc]; after 30 days Volume s chrumpfvmg [%]; Solidification at 25 C ^ to ^{+ 1h} · 900 4960 2500 25000 1 2 3 5 4 - δ 6-7 8-9 3 290 400 440 850 125 140 120 160 - 170 4.5 4.6 4.5 4.17

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Claims (1)

A method for Hera distribution of optical adhesives based on uniaodified, low molecular weight, containing at least two epoxy groups per molecule epoxy resins, characterized in that is used as the polyaddition component for epoxy resins H, N'-Mbenzyl-äthylendiaiain, where appropriate, further aminiache PolyadditionökoTiiponenten rait two Ашіп-Y / ass first of fat omen per molecule in an amount of. From 0.5 to 49 Hol-fo or 3-ol with three or more reactive amine-hydrogen functionalities per molecule of 0.5 to 30 molar%, based on the total amount of amine. Hiei? U