CA1272981A

CA1272981A - Laminating acrylate sheet to sheets of glass to produce safety glass

Info

Publication number: CA1272981A
Application number: CA000487495A
Authority: CA
Inventors: Massimo Meoni
Original assignee: Polivar SpA
Current assignee: Polivar SpA
Priority date: 1984-07-31
Filing date: 1985-07-25
Publication date: 1990-08-21
Anticipated expiration: 2007-08-21
Also published as: DE3566635D1; EP0172143A1; US4734143A; ATE39080T1; ES545724A0; EP0172143B1; IT8448672A0; IT1177945B; JPH0472783B2; ES8706527A1; JPS6144740A

Abstract

ABSTRACT

A method of producing safety glass, comprising the steps of polymerizing, in the form of a continuous ribbon, a mixture of polymerizable monomers including a composition of polymerizable monomers, a plasticizer and an effective amount of a catalyst of the azo or peroxy series, between a pair of transparent films of plastic material which is inert to the polymerization reaction and transparent to visible infrared and ultraviolet light, by exposing said polymerizable mixture between said films to a first irradiation with light in the ultraviolet and infrared spectrum range and then subsequently exposing said polymerizable mixture between said films to a second irradiaiton with light in the infrared spectrum range but absent light in said ultraviolet range, the ultraviolet irradiation to which said polymerizable mixture is exposed being no more than about 10% of the total irradiation, the mixture of polymerizable monomers being irradiated for a total of 45 minutes to 3 hours, so as to form a covered elastomeric polymerized resin sheet. Both of the films are removed from the covered elastomeric polymerized resin sheet to form an uncovered elastomeric polymerized resin sheet. The uncovered elastomeric polymerized resin is bonded between two sheets of glass adjacent top and bottom surfaces of said uncovered polymerized resin sheet to form a safety glass.

Description

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1) Societ~ Italiana Vetro SIV S.p.A.

2) Polivar S~poA~

A PROCESS FOR THE PRODUCTION OF A CONTINUOUS
COMPOSITE RIBBON INCLUDING AN ACRYLAT~ RESIN FILM
TO BE USED IN SAFETY LAMINATED GLASS PANELS AND
PRODUCT THEREBY OBTAINED
DISCLOSURE
Background of the in~ention 1. Field of the invention The present invention relates to a process for the production, in industrial quantities, of an elastomeric film, particularly useful as an intermediate layer for safety laminated glass panels, said film being obtained as a composite continuous ribbon~ interposed between two prot0ctive -films, by means o-f a continuous process o polymerization o-f a mixture of acrylate resin in a closed polymerization cell, formed by the two protecti~e ilms themselves, made of a transparent materia~. Safe~y : glass panels presently in commerce are constituted generally of two layers of glass bonded by an intermedi-~ 15 : ate layer of a plastic material~
: ~ In order to be defined as a safety glass, a glass ~; : article o~ manufacture must have a large capability of : absorbing shock energy, a high tear and splitting strength in order to prevent the rupture of the inter-.
mediate layer o~ plastic material by the glass splinters~
; a sufficient adhesion between the layers for minimizing ; the scattering and projection of glass splinters, in the ~; event of a breakage, and a hîgh optical quality, in ~: order to satisfy the regulations presently in force for 25 such articles of manufacture. ~.
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Description of the rriOr Art _ ____ _ __ In the prior art, as an intermediate plastic material, a relatively thick film of plastified polyvinyl butyral is used, which hereinafter will be referred to as PVB.
Such a film is produced by processes which are well known. Equally well known and commonly utilized is the technology for using the film in the manufacture o- safety laminated glass panels.
There is, however, a strong trend to replace P~B with other polymeric films, in order to reach the objective of appreciable reduction of the manufacturing costs for laminated glass panels. Presently, indeed, the cost of the PVB film amounts to about 30-40% of the production costs of a safety laminated glass panel.
In the prior art several attempts have been made to obtain films as an alternative to PVB, obtained from compositions of difEerent materials. U.S. Patents 3,509,015, 3,764,457,

3,900,446 and 4,241,140 disclose examples of compositions of mixtures for obtaining intermediate layers of transparent polyurethane material, suitable to be utilized in safety laminated glass panels.
Also polymers based on vinyl chloride have been proposed. U.S. Patent No. 4,389,508 provides, as an example, an intermediate layer constituted of a thermoplastic resin resulting from the polymerization of vinyl chloride (80-98.5~) and a glycidylmethacrylate, suitably mixed with a plasticizer.
It is also known from the prior art that it is possible to use as intermediate layers acrylic polymers as taught by French Patent No. 2,101,083. In this French patent, however, the technique for obtaining the intermediate layer of acrylic resin .~ .

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consists in casting between the glass panels to be laminated said acrylic resin in liquid form, that subsequently polymerizes ln situ The prior art provides useful suggestions as to how to obtain alternative products to the Pvs presently utilized in the large industrial productions of safety laminated glass panels (in particular wind shields for cars and glaze unit for buildings).
However, the prior art does not suggest how to produce, on industrial scale, elastomerlc films which may replace PVB both in a large industrial production process, nor does it suggest the use oE such films in the lamination of sa-ety glass panels, using technologies similar to those utilized for PVB. As a matter of fact, the alternative ~ilms of the prior art are produced in quantities which are not appropriate for industrial use. In addition, it is necessary to modify existing industrial equipment before the alternative films can be used in the production of the laminated glass panels.
French Patent No. 2,101,083, which teaches the use of acrylic polymers as intermediate layers, requires extensive modi~ications in the technology which is now used in the production of safety laminated glass panels on an industrial scale.
Insofar as the production of PVB films is concerned, the prior art uses a heat polymerization process and a subsequent extrusion of the film. Moreover, in order to avoid the seIf-bonding of the coiled film, the same film must be dusted with ~alc or powders, or be maintained under an atmosphere with a defined relative humidity and at a temperature below 0 centrigrade degrees. U.S. Patents 3,872,197, 3,988,098, 4,211,742 and French Patents 2,214,716 and 2,294,038 disclose a continuous polymerizatlon for obtaining rlgid acrylic sheets haviny a thickness equaI or greater than 2 millimeters. The polymerization is performed by a thermal process which is carried out between two endless conveyor ribbons that operate as a polymerization cell.
The product is a ri~id sheet, that cannot be coiled and that ~ cannot be utilized as intermediate layer for safety glass panels.
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Summary of the Inventlon According to one aspect of the present invention, there is provided a film of thermoplastic material based on acrylate resins, as an alternative to PV8 for the use as an intermediate layer in safety glass panels, that moreover is produced by means of a continuous photopolymerization process, the film being coiled into coils protected by two thin films adjacent to it, in order to avoid the problem of the self-bonding during the storage. The two protective films are the same ilms that during the photopolymerization process constitute the mold for the acrylic film.
According to another aspect of the present invention, there is provided a method of producing safety glass, comprising the steps of: polymerizing, in the form of a continuous ribbon, a mixture of polymerizable monomers including: A) one part by weight of a composition of polymerizable ~onomers including 60 to 97 parts by weight acrylic or methacrylic ester, 0 to 2 parts by weight acryl.ic or methacrylic acid, 0 to 5 parts by weight N-2-vinylpyrrolidone, 0 to 5 parts by weight acrylic or methacrylic acid ester including glycidyl groups; B) 0.16 to 1.2 parts by weight of a plasticizer selected from the class consistinq of adipic acid, isophthalic acid, phthalic acid, sebacic acid, epoxy derivatives and polyester derivativess and C) an effective amount of a catalyst of the azo or peroxy series, `:

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- 4a -between a pair of transparent organic polymeric films inert to said polymerizing and transparent to visible infrared and visible ultraviolet light by exposing said polymeriæable mixture between said films to a first irradiation with light in the infrared and visible ultraviolet spectrum range and then subsequently exposing said polymerizable mixture between said films to a second irradiation with light in the infrared spectrum range absent light in said visible ultraviolet range, the amount of visible ultraviolet irradiation to which said polymerizable mixture is exposed being no more than about 10~ of the total irradiation, the mixture of polymerizable monomers being irradiated for a total of 45 minutes to 3 hours, so as to form a covered elastomeric polymerized resin sheet; removing both of said films from said covered elastomeric polymerized resin sheet to form an uncovered elastomeric polymerized resin sheet; bonding said uncovered elastomeric polymerized resin between two sheets of glass adjacent top and bottom surfaces of said uncovered polymerized resin sheet to form a safety glass.
According to yet another aspect of the present invention, there is provided a method of producing a continuous sheet of polymerized resin, comprising the steps of polymerizing, in the form of a continuous ribbon, a mixture oE
polymerizable monomers including: A) one part by weight of a composition of polymerizable monomers including 60 to 97 parts by : weight acrylic or methacrylic ester, 0 to 2 parts by weight acrylic or methacrylic acid, 0 to S parts by weight :: .
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- 4b N~2-vinylpyrrolidone, 0 to 5 parts by weight acrylic or methacrylic acid ester including glycidyl groups; (B) 0.16 to 1.2 parts by weight of a plasticizer selected Erom the class consisting of adipic acid, isophthalic acid, phthalic acid, sebacic acid, epoxy derivatives and polyester derivatives; and (C) an effective amount of a catalyst of the azo or peroxy series, between a pair of transparent organic polymeric films inert to said polymerizing and transparent to infrared and visible ultraviolet light by exposing said polymerizable mixture between said films to a first irradiation with light in the infrared spectrum and visible ultraviolet range and then subsequently exposing said polymerizable mixture between said films to a second irradiation with light in the infrared spectrum range absent light in said visible ultraviolet range, the amount of visible ultraviolet irradiation to which said polymerizable mixture is exposed being no more than about 10% of the total irradiation, the mixture of polymerizable monomers being irradiated for a total of 45 minutes to 3 hours, so as to form a covered flexible elastomeric polymeri~ed resin sheet.
~ ccording to yet another aspect of the present invention, there is provided a windable composite ribbon, comprising two external release iilms of transparent plastic resin of less than 50 microns thickness and a self-supporting, flexible intermediate elastomeric layer having a thickness of 0.4 to 2 millimeters, said ribbon having been produced by:
polymerizing, in the form of a continuous ribbon, a mixture of .

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- 4c -polymerizable monomers including: A) one part by weight of a composition of polymerizable monomers including 60 to 97 parts by weight acrylic or methacrylic ester, 0 to 2 parts by weight acrylic or methacrylic acid, 0 to 5 parts by weight N-2-vinylpyrrolidone, 0 to 5 parts by weight acrylic or methacrylic acid ester including glycidyl groups (B) 0.16 to 1.2 parts by weight of a plastisizer selected from the class consisting of adipic acid, isophthalic acid, phthalic acid, sebacic acid, epoxy derivatives and polyester derivatives and (C) an effective amount of a catalyst of the azo or peroxy series, between a pair of transparent organic polymeric films inert to said polymerizing and transparent to infrared and visible ultraviolet light by exposing said polymerizable mixture between said films to a first irradiation with light in the infrared spectrum and visible ultraviolet range and then subsequently exposing said polymerizable mixture between said films to a second irradiation with light in the infrared spectrum range absent light in said visible ultraviolet range, the amount of visible ultraviolet irradiation to which said polymeri~able mixture is exposed being no more than about 10~ of the total irradiation, the mixture of polymerizable monomers being irradiated for a total of 45 minutes to 3 hours, so as to form a covered flexible elastomeric polymerized resin sheet.
According to yet another aspect of the present invention, there is provided a method of production of safety glaes in which the intermediate layer of the composite ribbon ' ,.: . .. .

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obtained with the above mentioned process is laminated between glass panels to provide an intermediate layer in the form of a film of transparent elastomeric acrylate resin of the above cited kind.
Conse~uently, according to the present invention a film is obtained suitable for use as an intermediate layer for safety glass panels, which may be substituted for PVB. The film has a thickness between 0.4 and 2 millimeters and a width of up to 2 meters~ The film will not bond to itself when formed into a coil and it can therefore be transported without problems of self-bonding. It can also tolerate the conditions of temperature and humidity which are normally encountered during the storage.
The film may be utilized in a pre-existing plants which manufacture safety glass panels without requiring any modifications to the plant.
Brief Description of the Drawings In the following, several examples of embodiments of the present invention will be disclosed, making reference to the single figure of the attached drawing that represents schematically an apparatus for the production of the composite?
eibbon, th~t realizes the process according to the invention.
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represents schematically an apparatus for the production of the composite ribbon, that realizes the process according to the invention.
_escription of th~_preferred embodiments A continuous conveyor belt l that receives movement from the rollers 2, 2' actuated by a motor 3, operates as a support for a ~ransparent film Pl that is uncoiled from a coil 4.
Said transparent film Pl constitutes the bottom sup-port over which the composition to be polymerized is cast uniormly. A feed tank 5 delivers the composition to be polymerized. The distribution and the metering of the composition are performed by means of a delivery hopper that adjusts the flow by means of an automatic pressure regulator (not represented) that permits that the compo-sition be cast in a uniform and constant manner.
A thickness control doctor blade 6 provides to main-~ tain constant the thickness of the composition on the - film Pl.
A coil 7 provides a second transparent film P2, that is laid upon the composition to be polymerized. A roller 8 that operates also as a tensioning idler for the film P2, provides for the fine thickness control and the coupling of the system comprised of Pl, composition, P2.
Insofar as the transparent films are concerned, it has been found that polyethylenterephthalate with a thick-ness not greater than 50 micrometers is suitable for this purpose.
The lateral walls of the polymerization cell are folded over by inserting the edge ends of the two films Pl and P~
in two L-shaped guideways 9 perpendicular to the transport plane and located at the two ends, that provide to fold ~:
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upwards ~he lateral ends and to maintain them adherent each other.
The two transparent films Pl and P2 consequently consti-tute the wall of a polymerization cell or mold that is paid off in a con~inuous way.
The polymerization cell 9 transported by the belt 1, enters into a polymerization tunnel 10 where the composi-tion is subjected to polymerization by irradia~ion with light radiation.
It has been found that in order to obtain a product with physical-mechanical characteristic suitable for the intended use, the kind of irradiation must be of the mixed type: visible ultraviolet ~UV) plus infrared (IR), where the percentage of visible UV should not be greater than 10% of the total.
After the polymerization step a cutter 11 provides for ; the trimming of the cell on both its sides.
The composite ribbon 12 constituted of the two ex-ternal films Pl and P2, as well as of the internal poly-merized film after a second IR irradiation, is coiled over a roller 13 and stored without any other particular measure.
In the drawing the rollers 14 indicate transport rol-lers for the composite ribbon 12.
Two acrylate compositions,hereinafter described, have been utllized as main components of the feed mixtures in a process aecording to the invention.
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A mixture comprising, by weight:
30 - 90 to 100% and preferably~94 to 97% of acrylic and, or, methacrylic esters; ~
- 0 to 2% of acrylic or methacrylic acid;

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- O to 5~ of vinyl esters, in particular N-2-vinyl-pyrrolidone;
- O to 5~ of acrylic and, or,me~hacrylic esters having hydroxyl groups and7 or, glycidyl groups;
- radicalic catalysts of the azoic and peroxy series;
is thermally partially bulk polymerized with a con-version between 3 and 25~. A part by weight of the above said mixture is disperded in 0.16 to 1.2 parts and ; preferably in 0.9 to 1.1 parts by weight of a plasti-cizer compatible with the above said mono-polymeric systems, said plasticizer being a member of the class of derivatives of adipic acid, isophthalic acid, phtha-lic acid, sebacic ac;d, epoxy derivatives, polyester derivatives.
Composition A2 The acrylic mixture comprises by weight:
- 10 to 40% and preferably 18 to 35% of acrylic and, or, methacrylic polymers;
- O to 2~ of acrylic or methacrylic acid;
- O to 5~ of vinyl esters, preferably N~2~vinylpyrroli-done;
- O to 5~ of esters of acrylic and, or, methacrylic acid having glycidyl groups;
- 60 to 90~ and preferably 65 to 80% of acrylic and, or, methacrylic esters.
One part in weight of the above said mixture is disperded in 0.16 to 1 2 parts by weight and preferably 0.9 to 1.1 parts by weight of a plasticizer compatible with the above said mono-polymeric systems, said plasticizer being a member of the class of derivatives ` o~ adipic acid, isophthalic acid, phthalic acid, sebacic acid and epoxy and polyester derivatives.

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Production tests have been performed according to the process objec-t of the invention with the above said mixtures, the characteristics of said tests being reported as an example in the following examples.
Example 1 A mixture of the A2 type containing 1.5 parts by weight of glycidylmethacrylate, 1 part of N-2-vinylpyrrolidone, 2.5 parts of 2-ethylhexylacrylate, 1 part of butyleneglycoldimethacrylate, 45.5 parts of dibutylphthalate, 13.65 parts of polymethylmethacrylate, 31.85 parts of methylmethacrylate, is additioned to 3 parts of DAROCUR (Trade Mark) photoinitiator and 0.02 parts of bis-(4 t.butyl-cyclohexyl)-peroxy-dicarbonate and 0.01 parts of azo-bis-valeronitrile. Such mixture has been cast continuously between sheets of polyethylene-terephthalate having a thickness not greater than 50 micrometers in order to form a resin of a thickness equal to 1~0.1 millimeters. The sandwich thus formed is passed through a first tunnel of mixed irradiation with visible UV+IR, where the UV irradiation is equal to 5~ of the total irradiation and a second IR tunnel, so that the total irradiation UV~IR is effected for a time of 90 minutes.
The resulting film after having been freed of the protection films of polyethylenterephthalate, that have constituted the polymerization cell, were placed between two glass plates of 300x300 millimeters, each 2.5 millimeters thick, and the resulting sandwich, after having been subjected to a press was placed in autoclave under a pressure of 10 ATE (atmosphere gauge pressure) and a temperature of 110 centigrade dégrees for one hour.

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Having performed the test prescribed by the regulations on 10 specimens, positive results have been obtained according to rule ECE 43 (European Community Standards).
Example 2 A mixture of the A2 type containing 47 parts of dloctylphthala-te, 16 67 parts of polymethylmethacry~ate, 33.84 parts of methylmethacrylate, has been added to 2.5 parts of IRGACUR (Trade Mark) photoinitiator and it has been continuously cast and thermo-photo-polymerized as in Example 1, with a UV irradiation corresponding to 10~ of the total and with a total polymerization time corresponding to 60 minutes.
The resulting film, after having been freed from the protective films was placed between two glass plates of 300x300 millimeters and 2.5 millimeters in thickness, previously coated with a silane primer.
The sandwich has been initially subjected to a press and then placed in autoclave under 11 Ate and 120 centigrade degrees for 2 hours.
The results of the tests performed on lO specimens have been positive according to Rule ECE 43.
Example 3 A mixture like the one disclosed in Example 2, but containing also 0.01 parts of methacrylic acid, has been continuously cast and thermo-photopolymerized as disclosed in Example 2 for a total polymerization time corresponding to 150 minutes.
The resulting film, after being stripped of the protective film, has been placed between glass plates of 300x300 millimeters and 2.5 millimeters of thickness ,~
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and the resulting sandwich, after having been subject to a press, has been placed in autoclave under 7 Ate and 110 centigrade degrees for 2 hours.
Also in this case the specimens subjected to tests gave positive results according to rule ECE 43.
Example 4 A mixture of the Al type containing 47 parts of dioctylphthalate, 50.4 parts of methylmethacrylate, previously p~e-polymerized, in the presence of 100 ppm of bis-(4-t.-butyl-cyclohexyl)-peroxy-carbonate and 100 ppm of azo-bis-valeronitrile and 100 ppm of lauryl-; mercaptane, up to a conversion degree of 13%, after having been additioned with 2.5 parts of IRGACUR photo-initiator, has been treated as in foregoing example.
The tests performed on 5 specimens gave a positive ac-cording to rule ECE 43.
The invention resolves therefore the problem of producing with low costs and on industrial scale a film obtained from acrylate resin, suitable for safety laminated glass panels, that can also be easily transpor-ted and stored.
By means of the present invention the resul~ is obtained o~ introducing on the market a product alter~
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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of producing safety glass, comprising the steps of:
polymerizing, in the form of a continuous ribbon, a mixture of polymerizable monomers including:
a) one part by weight of a composition of polymerizable monomers including 60 to 97 parts by weight acrylic or methacrylic ester, 0 to 2 parts by weight acrylic or methacrylic acid, 0 to 5 parts by weight N-2-vinylpyrrolidone, 0 to 5 parts by weight acrylic or methacrylic acid ester including glycidyl groups;
b) 0.16 to 1.2 parts by weight of a plasticizer selected from the class consisting of adipic acid, isophthalic acid, phthalic acid, sebacic acid, epoxy derivatives and polyester derivatives and c) an effective amount of a catalyst of the azo or peroxy series, between a pair of transparent organic polymeric films inert to said polymerizing and transparent to visible infrared and visible ultraviolet light by exposing said polymerizable mixture between said films to a first irradiation with light in the infrared and visible ultraviolet spectrum range and then subsequently exposing said polymerizable mixture between said films to a second irradiation with light in the infrared spectrum range absent light in said visible ultraviolet range, the amount of visible ultraviolet irradiation to which said polymerizable mixture is exposed being no more than about 10% of the total irradiation, the mixture of polymerizable monomers being irradiated for a total of 45 minutes to 3 hours, so as to form a covered elastomeric polymerized resin sheet;
removing both of said films from said covered elastomeric polymerized resin sheet to form an uncovered elastomeric polymerized resin sheet;
bonding said uncovered elastomeric polymerized resin between two sheets of glass adjacent top and bottom surfaces of said uncovered polymerized resin sheet to form a safety glass.

2. The method of claim 1, further comprising the steps of winding said covered elastomeric polymerized resin sheet into a coil and unwinding said coil prior to the step of removing said films.

3. The method of claim 1, wherein said transparent plastic resin forming said external films is selected from the class consisting of polypropylene, polyethylene, polyamide, polyester.

4. The method of claim 1, wherein said transparent plastic resin forming said external films is a polyethylene terephthalate

5. A method of producing a continuous sheet of polymerized resin, comprising the steps of:
polymerizing, in the form of a continuous ribbon, a mixture of polymerizable monomers including:
A) one part by weight of a composition of polymerizable monomers including 60 to 97 parts by weight acrylic or methacrylic ester, 0 to 2 parts by weight acrylic or methacrylic acid, 0 to 5 parts by weight N-2-vinylpyrrolidone, 0 to 5 parts by weight acrylic or methacrylic acid ester including glycidyl groups;
(B) 0.16 to 1.2 parts by weight of a plasticizer selected from the class consisting of adipic acid, isophthalic acid, phthalic acid, sebacic acid, epoxy derivatives and polyester derivatives; and (C) an effective amount of a catalyst of the azo or peroxy series, between a pair of transparent organic polymeric films inert to said polymerizing and transparent to infrared and visible ultraviolet light by exposing said polymerizable mixture between said films to a first irradiation with light in the infrared spectrum and visible ultraviolet range and then subsequently exposing said polymerizable mixture between said films to a second irradiation with light in the infrared spectrum range absent light in said visible ultraviolet range, the amount of visible ultraviolet irradiation to which said polymerizable mixture is exposed being no more than about 10% of the total irradiation, the mixture of polymerizable monomers being irradiated for a total of 45 minutes to 3 hours, so as to form a covered flexible elastomeric polymerized resin sheet.

6. The method of claim 5, further comprising the step of removing both of said films from said covered elastomeric polymerized resin sheet to form an uncovered elastomeric polymerized resin sheet.

7. A windable composite ribbon, comprising two external release films of transparent plastic resin of less than 50 microns thickness and a self-supporting, flexible intermediate elastomeric layer having a thickness of 0.4 to 2 millimeters, said ribbon having been produced by:
polymerizing, in the form of a continuous ribbon, a mixture of polymerizable monomers including:

A) one part by weight of a composition of polymerizable monomers including 60 to 97 parts by weight acrylic or methacrylic ester, 0 to 2 parts by weight acrylic or methacrylic acid, 0 to 5 parts by weight N-2-vinylpyrrolidone, 0 to 5 parts by weight acrylic or methacrylic acid ester including glycidyl groups;
(B) 0.16 to 1.2 parts by weight of a plasticizer selected from the class consisting of adipic acid, isophthalic acid, phthalic acid, sebacic acid, epoxy derivatives and polyester derivatives and (C) an effective amount of a catalyst of the azo or peroxy series, between a pair of transparent organic polymeric films inert to said polymerizing and transparent to infrared and visible ultraviolet light by exposing said polymerizable mixture between said films to a first irradiation with light in the infrared spectrum and visible ultraviolet range and then subsequently exposing said polymerizable mixture between said films to a second irradiation with light in the infrared spectrum range absent light in said visible ultraviolet range, the amount of visible ultraviolet irradiation to which said polymerizable mixture is exposed being no more than about 10% of the total irradiation, the mixture of polymerizable monomers being irradiated for a total of 45 minutes to 3 hours, so as to form a covered flexible elastomeric polymerized resin sheet.

8. A composite ribbon according to claim 7, wherein said resin forming the external films is polyethylene terephthalate resin.

9. A safety glass panel comprising two sheets of glass having an intermediate layer in the form of a composite ribbon comprising a film of a transparent elastomeric acrylate resin having a thickness in the range of 0.4 to 2 millimeters, said ribbon having been produced by:
polymerizing, in the form of a continuous ribbon, a mixture of polymerizable monomers including;
a)one part by weight of a composition of polymerizable monomers including 60 to 97 parts by weight acrylic or methacrylic ester, 0 to 2 parts by weight acrylic or methacrylic acid, 0 to 5 parts by weight N-2-vinylpyrrolidone, 0 to 5 parts by weight acrylic or methacrylic acid ester including glycidyl groups;
b) 0.16 to 1.2 parts by weight of a plasticizer selected from the class consisting of adipic acid, isophthalic acid, phthalic acid, sebacic acid, epoxy derivatives and polyester derivatives; and c) an effective amount of a catalyst of the azo or peroxy series, between a pair of transparent organic polymeric films inert to said polymerizing and transparent to infrared and visible ultraviolet light by exposing said polymerizable mixture between said films to a first irradiation with light in the infrared spectrum and visible ultraviolet range and then subsequently exposing said polymerizable mixture between said films to a second irradiation with light in the infrared spectrum range absent light in said visible ultraviolet range, the amount of visible ultraviolet irradiation to which said polymerizable mixture is exposed being no more than about 10% of the total irradiation, the mixture of polymerizable monomers being irradiated for a total of 45 minutes to 3 hours, so as to form a covered flexible elastomeric polymerized resin ribbon, and wherein said films were removed before the ribbon was located between the two sheets of glass to form the intermediate layer.