SELF-ADHESIVE MULTI-LAYER ITEM AND METHOD FOR THE PRODUCTION THEREOF

Abstract

A self-adhesive multi-layer item comprising: 1) a dorsal support DO having a top face SI1 and a bottom face SI2, 2) at least one layer of silicone release coating RC applied to the top face SI1 of the dorsal support DO and which is prepared by irradiation of a curable silicone composition C not containing any solvent and comprising, as constituents: a) at least one functionalized organopolysiloxane A b) an effective amount of at least one type I photoinitiator P of the family of acylphosphine oxide derivatives of formula (III) 3) at least one adhesive PSA, preferably at least one pressure-sensitive adhesive PSA, applied on the layer of silicone release coating, 4) a frontal support FR applied on the adhesive PSA of the component 3), and 5) optionally at least one layer of silicone release coating RC applied on the bottom face SI2 of the dorsal support DO and which is prepared by application and irradiation of said curable silicone composition C, and on this same layer, there is at least one adhesive PSA, preferably at least one pressure-sensitive adhesive PSA.

Claims

1. A self-adhesive multi-layer item comprising: 1) a dorsal support DO having a top face SI1 and a bottom face SI2, 2) at least one layer of silicone release coating RC applied to the top face SI1 of the dorsal support DO and which is prepared by irradiation of a curable silicone composition C not containing any solvent and comprising, as constituents: a) at least one functionalized organopolysiloxane A comprising: a1) at least one unit of formula (I) below:
R.sub.aZ.sub.bSiO.sub.(4-a-b)/2(I) in which formula: the symbols R, which may be identical or different, each represent a linear or branched C.sub.1 to C.sub.18 alkyl group, a C.sub.6 to C.sub.12 aryl or aralkyl group, which is optionally substituted, optionally with halogen atoms, or an alkoxy radical OR.sup.4 with R.sup.4 being a hydrogen atom or a hydrocarbon-based radical comprising from 1 to 10 carbon atoms, the symbols Z are monovalent radicals of formula -y-(Y).sub.n in which: y represents a linear or branched C.sub.1-C.sub.18 polyvalent alkylene radical optionally extended by C.sub.1 to C.sub.4 oxyalkylene or polyoxyalkylene divalent radicals, which is optionally substituted with a hydroxyl radical, Y represents an alkenylcarbonyloxy monovalent radical, and n is equal to 1, 2 or 3, and a is an integer equal to 0, 1 or 2, b is an integer equal to 1 or 2 and the sum a+b=1, 2 or 3; and a2) optionally units of formula (II) below:
R.sub.aSiO.sub.(4-a)/2(II) in which formula: the symbols R, which may be identical or different, each represent a linear or branched C.sub.1 to C.sub.18 alkyl group, a C.sub.6 to C.sub.12 aryl or aralkyl group, which is optionally substituted, optionally with halogen atoms, and a is an integer equal to 0, 1, 2 or 3, and b) an effective amount of at least one type I photoinitiator P of the family of acylphosphine oxide derivatives of formula (III) below: ##STR00015## in which formula: the symbol R.sup.5 is a monovalent radical OR.sup.8 with the symbol R.sup.8 being a hydrocarbon-based radical comprising from 1 to 8 carbon atoms; the symbol R.sup.6 is a phenyl radical optionally substituted with: one or more halogen atom(s), a hydrocarbon-based radical comprising from 1 to 8 carbon atoms, a hydrocarbon-based alkoxy radical comprising from 1 to 8 carbon atoms, and/or a hydrocarbon-based thio radical comprising from 1 to 8 carbon atoms; and the symbol R.sup.7 represents a hydrocarbon-based radical comprising from 1 to 12 carbon atoms, a benzyl radical or a phenyl radical optionally substituted with one or more halogen atom(s), a hydrocarbon-based radical comprising from 1 to 8 carbon atoms, a hydrocarbon-based alkoxy radical comprising from 1 to 8 carbon atoms and/or a cycloalkyl radical; 3) at least one adhesive PSA, optionally at least one pressure-sensitive adhesive PSA, applied on the layer of silicone release coating, 4) a frontal support FR applied on the adhesive PSA of the component 3), and 5) optionally at least one layer of silicone release coating RC applied on the bottom face SI2 of the dorsal support DO and which is prepared by application and irradiation of said curable silicone composition C, and on this same layer, there is at least one adhesive PSA, optionally at least one pressure-sensitive adhesive PSA.

2. The self-adhesive multi-layer item as claimed in claim 1, wherein the dorsal support DO is chosen from the group made up of: polymer films and papers.

3. The self-adhesive multi-layer item as claimed in claim 1, wherein the frontal support FR is chosen from the group made up of: cellulose-based derivatives, metal sheets, polycarbonates, polyethylene films, polyethylene terephthalate films, polypropylene films and vinyl films.

4. The self-adhesive multi-layer item as claimed in claim 1, wherein the effective amount of photoinitiator P is between 0.1% and 5% by weight relative to the weight of the functionalized organosiloxane or organopolysiloxane A, and optionally between 0.1% and 3% by weight relative to the weight of the functionalized organosiloxane or organopolysiloxane A.

5. The self-adhesive multi-layer item as claimed in claim 1, wherein the photoinitiator P is ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate.

6. The self-adhesive multi-layer item as claimed in claim 1, wherein said item is a self-adhesive label or a self-adhesive tape.

7. A self-adhesive multi-layer item comprising: 1) a dorsal support DO having a top face SI1 and a bottom face SI2, 2) at least one layer of silicone release coating RC applied on the top face SI1 of the dorsal support DO and which is prepared by irradiation of a curable silicone composition C not containing any solvent and comprising as constituents: a) at least one functionalized organopolysiloxane A comprising: a1) at least one unit of formula (I) below:
R.sub.aZ.sub.bSiO.sub.(4-a-b)/2(I) in which formula: the symbols R, which may be identical or different, each represent a linear or branched C.sub.1 to C.sub.18 alkyl group, a C.sub.6 to C.sub.12 aryl or aralkyl group, which is optionally substituted, optionally with halogen atoms, or an alkoxy radical OR.sup.4 with R.sup.4 being a hydrogen atom or a hydrocarbon-based radical comprising from 1 to 10 carbon atoms, the symbols Z are monovalent radicals of formula -y-(Y).sub.n in which: y represents a linear or branched C.sub.1-C.sub.18 polyvalent alkylene radical optionally extended by C.sub.1 to C.sub.4 oxyalkylene or polyoxyalkylene divalent radicals, which is optionally substituted with a hydroxyl radical, Y represents an alkenylcarbonyloxy monovalent radical, and n is equal to 1, 2 or 3, and a is an integer equal to 0, 1 or 2, b is an integer equal to 1 or 2 and the sum a+b=1, 2 or 3; and a2) optionally units of formula (II) below:
R.sub.aSiO.sub.(4-a)/2(II) in which formula: the symbols R, which may be identical or different, each represent a linear or branched C.sub.1 to C.sub.18 alkyl group, a C.sub.6 to C.sub.12 aryl or aralkyl group, which is optionally substituted, optionally with halogen atoms, and a is an integer equal to 0, 1, 2 or 3, and b) an effective amount of at least one type I photoinitiator P of the family of acylphosphine oxide derivatives of formula (III) below: ##STR00016## in which formula: the symbol R.sup.5 is a monovalent radical OR.sup.8 with the symbol R.sup.8 being a hydrocarbon-based radical comprising from 1 to 8 carbon atoms; the symbol R.sup.6 is a phenyl radical optionally substituted with: one or more halogen atom(s), a hydrocarbon-based radical comprising from 1 to 8 carbon atoms, a hydrocarbon-based alkoxy radical comprising from 1 to 8 carbon atoms, and/or a hydrocarbon-based thio radical comprising from 1 to 8 carbon atoms; and the symbol R.sup.7 represents a hydrocarbon-based radical comprising from 1 to 12 carbon atoms, a benzyl radical or a phenyl radical optionally substituted with one or more halogen atom(s), a hydrocarbon-based radical comprising from 1 to 8 carbon atoms, a hydrocarbon-based alkoxy radical comprising from 1 to 8 carbon atoms and/or a cycloalkyl radical; 3) at least one adhesive PSA, optionally at least one pressure-sensitive adhesive PSA, applied on the bottom face SI2 of the dorsal support DO.

8. A process for preparing a self-adhesive multi-layer item as defined in claim 1, comprising a) to d): a) a curable silicone composition C not containing any solvent and comprising, as constituents: a) at least one functionalized organopolysiloxane A comprising: a1) at least one unit of formula (I) below:
R.sub.aZ.sub.bSiO.sub.(4-a-b)/2(I) in which formula: the symbols R, which may be identical or different, each represent a linear or branched C.sub.1 to C.sub.18 alkyl group, a C.sub.6 to C.sub.12 aryl or aralkyl group, which is optionally substituted, optionally with halogen atoms, or an alkoxy radical OR.sup.4 with R.sup.4 being a hydrogen atom or a hydrocarbon-based radical comprising from 1 to 10 carbon atoms, the symbols Z are monovalent radicals of formula -y-(Y).sub.n in which: y represents a linear or branched C.sub.1-C.sub.18 polyvalent alkylene radical optionally extended by C.sub.1 to C.sub.4 oxyalkylene or polyoxyalkylene divalent radicals, which is optionally substituted with a hydroxyl radical, Y represents an alkenylcarbonyloxy monovalent radical, and n is equal to 1, 2 or 3, and a is an integer equal to 0, 1 or 2, b is an integer equal to 1 or 2 and the sum a+b=1, 2 or 3; and a2) optionally units of formula (II) below:
R.sub.aSiO.sub.(4-a)/2(II) in which formula: the symbols R, which may be identical or different, each represent a linear or branched C.sub.1 to C.sub.18 alkyl group, a C.sub.6 to C.sub.12 aryl or aralkyl group, which is optionally substituted, optionally with halogen atoms, and a is an integer equal to 0, 1, 2 or 3, and b) an effective amount of at least one type I photoinitiator P of the family of acylphosphine oxide derivatives of formula (III) below: ##STR00017## in which formula: the symbol R.sup.5 is a monovalent radical OR.sup.8 with the symbol R.sup.8 being a hydrocarbon-based radical comprising from 1 to 8 carbon atoms; the symbol R.sup.6 is a phenyl radical optionally substituted with: one or more halogen atom(s), a hydrocarbon-based radical comprising from 1 to 8 carbon atoms, a hydrocarbon-based alkoxy radical comprising from 1 to 8 carbon atoms, and/or a hydrocarbon-based thio radical comprising from 1 to 8 carbon atoms; and the symbol R.sup.7 represents a hydrocarbon-based radical comprising from 1 to 12 carbon atoms, a benzyl radical or a phenyl radical optionally substituted with one or more halogen atom(s), a hydrocarbon-based radical comprising from 1 to 8 carbon atoms, a hydrocarbon-based alkoxy radical comprising from 1 to 8 carbon atoms and/or a cycloalkyl radical; is prepared by mixing constituents; b) between 0.1 and 5 g per m.sup.2 of the composition C obtained is applied on the top face SI1 of a dorsal support DO in order to obtain the dorsal support DO coated with the composition C, c) the dorsal support DO coated with the composition C is then subjected to ultraviolet radiation in order to cure, by polymerization and/or crosslinking, the composition C making it possible to obtain a layer of silicone release coating RC, and d) d1) or d2) is carried out: d1) at least one adhesive PSA, optionally a pressure-sensitive adhesive PSA, is applied on the layer of silicone release coating RC, and then a frontal support FR is applied on the adhesive PSA, d2) an adhesive construction AD is prepared by applying, on a frontal support FR, at least one adhesive PSA, optionally one pressure-sensitive adhesive PSA, then the adhesive construction AD is joined with the dorsal support DO coated with the composition C prepared in c) in such a way that the adhesive PSA is located between the dorsal support DO and the frontal support FR, and e) optionally, the composition C obtained in a) is also applied on the bottom face SI2 of the dorsal support DO and is then subjected to ultraviolet radiation in order to cure, by polymerization and/or crosslinking, the composition C making it possible to obtain a layer of silicone release coating RC on the bottom face SI2 of the dorsal support DO, and subsequently at least one adhesive PSA, optionally at least one pressure-sensitive adhesive PSA, is applied on this same layer of silicone release coating RC.

9. The process as claimed in claim 8, wherein, in d) and/or e), an adhesive PSA, optionally a pressure-sensitive adhesive PSA, is applied in the form of an aqueous emulsion and is then dried.

10. The process as claimed in claim 8, wherein, in c), the ultraviolet radiation has a wavelength of between 100 and 400 nanometers, limits included.

11. An irradiation-curable silicone composition C which does not contain any solvent and which comprises as constituents: a) at least one functionalized organosiloxane or organopolysiloxane A comprising: a1) at least one unit of formula (I) below:
R.sub.aZ.sub.bSiO.sub.(4-a-b)/2(I) in which formula: the symbols R, which may be identical or different, each represent a linear or branched C.sub.1 to C.sub.18 alkyl group, a C.sub.6 to C.sub.12 aryl or aralkyl group, which is optionally substituted, optionally with halogen atoms, or an alkoxy radical OR.sup.4 with R.sup.4 being a hydrogen atom or a hydrocarbon-based radical comprising from 1 to 10 carbon atoms, the symbols Z are monovalent radicals of formula -y-(Y).sub.n in which: y represents a linear or branched C.sub.1-C.sub.18 polyvalent alkylene radical optionally extended by C.sub.1 to C.sub.4 oxyalkylene or polyoxyalkylene divalent radicals, which is optionally substituted with a hydroxyl radical, Y represents an alkenylcarbonyloxy monovalent radical, and n is equal to 1, 2 or 3, and a is an integer equal to 0, 1 or 2, b is an integer equal to 1 or 2 and the sum a+b=1, 2 or 3; and a2) optionally units of formula (II) below:
R.sub.aSiO.sub.(4-a)/2(II) in which formula: the symbols R, which may be identical or different, each represent a linear or branched C.sub.1 to C.sub.18 alkyl group, a C.sub.6 to C.sub.12 aryl or aralkyl group, which is optionally substituted, optionally with halogen atoms, and a is an integer equal to 0, 1, 2 or 3, and b) an effective amount of at least one type I photoinitiator P of the family of acylphosphine oxide derivatives of formula (III) below: ##STR00018## in which formula: the symbol R.sup.5 is a monovalent radical OR.sup.8 with the symbol R.sup.8 being a hydrocarbon-based radical comprising from 1 to 8 carbon atoms; the symbol R.sup.6 is a phenyl radical optionally substituted with: one or more halogen atom(s), a hydrocarbon-based radical comprising from 1 to 8 carbon atoms, a hydrocarbon-based alkoxy radical comprising from 1 to 8 carbon atoms, and/or a hydrocarbon-based thio radical comprising from 1 to 8 carbon atoms; and the symbol R.sup.7 represents a hydrocarbon-based radical comprising from 1 to 12 carbon atoms, a benzyl radical or a phenyl radical optionally substituted with one or more halogen atom(s), a hydrocarbon-based radical comprising from 1 to 8 carbon atoms, a hydrocarbon-based alkoxy radical comprising from 1 to 8 carbon atoms and/or a cycloalkyl radical.

12. The irradiation-curable silicone composition C as claimed in claim 11, wherein the photoinitiator P is ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate.

13. A substrate at least partially coated with a release coating prepared by application of the curable silicone composition C as defined in claim 11 and irradiation by ultraviolet radiation so as to bring about crosslinking thereof.

14. An irradiation-curable silicone composition C as defined in claim 11, in the field of one or more of self-adhesive labels, of bands including envelopes, of graphic arts, of medical and hygiene care and of construction and insulation.

15. A substrate at least partially coated with a release coating as defined in claim 13, in the field of one or more of self-adhesive labels, of bands including envelopes, of graphic arts, of medical and hygiene care and of construction and insulation.

Description

EXAMPLE

[0230] The compositions are prepared by mixing one or more silicone oils A according to formula (IV) described above and a photoinitiator P, the structures of which are given in detail below.

TABLE-US-00001 TABLE 1 Structures of the acryloxy-functionalized organopolysiloxanes Com- pound A R.sup.1 R.sup.2 R.sup.3 a b d c A1 CH.sub.3 [00007] CH.sub.3 85 7 0 0 A2 CH.sub.3 [00008] CH.sub.3 220 4 0 0 A3 CH.sub.3 [00009] CH.sub.3 16 5 0 0 A4 CH.sub.3 [00010] [00011] 90 4 0 0 A5 CH.sub.3 Not present in the formula [00012] 80 0 0 0

TABLE-US-00002 TABLE 2 Photoinitiators Photoinitiators Structures P1 = Irgacure? 1173 from BASF [00013] P2 = Tego? A18 from Evonik P3 = (ethyl (2,4,6- trimethylbenzoyl)phenyl- phosphinate) CAS No. 84434-11-7 [00014]

Coating Process

[0231] The silicone compositions are coated by means of a Rotomec coating controller on various supports (polyester or polypropylene). The machine speed is 50 or 100 m/min with a mercury lamp power fixed at 100 W/cm for carrying out the crosslinking under UV. This depositing is controlled by XRF measurement. At the outlet of the machine, the tests carried out are the smear, the rub-off, the dewetting and the measurement of silicone extractables.

Tests Carried Out on the Supports Coated with Silicone Release Coatings: [0232] Deposit: Testing of the silicone deposit coated on the surface by silicon X-ray fluorescence analysis (Lab-X 3000 from Oxford). An X-ray tube excites the electron layer of the silicon atoms, which causes an X-ray emission proportional to the amount of silicon excited. This value or number of counts is converted by calculation (using the calibration line) into an amount of silicone. [0233] Smear: Qualitative testing of the surface polymerization by the finger trace method which consists in: [0234] placing the sample of support coated with silicone to be tested on a flat and rigid surface; [0235] making a trace with the end of the finger by pressing moderately but firmly; and [0236] examining by eye the trace thus made, preferably in low-angle light. The presence of even a very slight trace can thus be seen by the difference in shininess of the surface.
The assessment is qualitative. The Smear is quantified with the following grades: [0237] A: very good, no trace of a finger [0238] B: slightly less good, trace barely visible [0239] C: clear trace [0240] D: very clear trace and oily appearance of the surface, product barely polymerized,
that is to say a grade of A to D, from the best result to the poorest. [0241] Rub-off: Testing of the ability of the silicone to adhere to the flexible support by scrubbing by moving the finger back and forward, which consists in: [0242] placing the sample of support coated with silicone to be tested on a flat and rigid surface, the silicone being on the upper face. [0243] moving the end of the finger back and forward ten times (along a length of approximately 10 cm) while moderately but firmly pressing. [0244] examining by eye the appearance of the scrubbing. The scrubbing corresponds to the appearance of a fine white powder or of small balls which roll under the finger.
The assessment is qualitative. The scrubbing is quantified with the following grades: [0245] 10: very good, no appearance of scrubbing after 10 back and forward movements [0246] 1: very poor, scrubbing from the first backward movement.
The grade corresponds to the number of back and forward movements (from 1 to 10) starting from which scrubbing appears.
That is to say a grade of 1 to 10, from the worst to the best result. [0247] Dewetting: Assessment of the degree of polymerization of the silicone layer by evaluation of the transfer of silicone onto an adhesive brought into contact with the coating by means of an ink with a standardized surface tension. The method is as follows: [0248] Select a sample of approximately 20?5 cm of the silicone-coated paper to be characterized, taken in the direction of unwinding (machine direction). [0249] Cut a length of ? 15 cm of adhesive tape, then place it adhesive side down on the paper to be tested, without folds, while exerting a pressure ten times by sliding the finger along the length of the adhesive tape (Scotch 3 M adhesive tape, reference 610, width: 25 mm). [0250] Remove the adhesive tape and deposit it flat, adhesive-treated part upward. [0251] With a (disposable) cotton bud, deposit on the adhesive-treated part of the tape a trace of ink along a length of approximately 10 cm (inks of the brand Sherman or Ferarini and Beneli having a surface tension ? 30 dynes/cm and a viscosity of 2 to 4 mPa/s). Immediately start the timer. [0252] It is considered that the dewetting phenomenon phase has been entered when the line of ink changes appearance, then stop the timer. [0253] The depositing of the ink on the adhesive-treated part of the tape must be done within 2 minutes following the silicone coating. [0254] If the result obtained is <10 seconds, it is considered that there is migration of silicone on the adhesive, and that the polymerization is not complete. [0255] A grade of 0 to 10 corresponding to the time elapsed in seconds before the observation of the dewetting phenomenon will be given. [0256] If the result obtained is 10 seconds, it is considered that the polymerization is complete. In this case, a grade of 10 will be given, meaning that the result is very good. [0257] Note the grade obtained and the ink used (name, brand, surface tension, viscosity). [0258] Extractables: Measurement of the amount of silicone which is not grafted to the network formed during polymerization. These silicones are extracted from the film by immersion of a sample, in MIBK for a minimum period of 24 h, as soon as said sample has exited the machine. This is measured by flame absorption spectroscopy.

Preparation of Self-Adhesive Multi-Layer Items

[0259] Standardized adhesive-treated supports TESA7475 (support=PET?adhesive=acrylic) and TESA4651 (support=acrylic-coated cloth?adhesive=natural rubber) are complexed on the silicone liner produced above (=support coated with a silicone coating obtained by crosslinking under UV) in order to form a multi-layer item. Tensile tests are carried out in order to determine the detachment forces before and after aging and also the values of subsequent adhesion and of loop-tack. These tests are described hereinafter.

Test Carried Out on the Multi-Layer Items Obtained

[0260] Subsequent adhesion (SubAd in the tables): Measurement of verification of the preservation of adhesivity of the adhesives (TESA 7475) having been in contact with the silicone coating according to the FINAT 11 test (FTM 11) known to those skilled in the art. In this case, the reference test specimen is PET and the adhesives remained in contact with the silicone surface to be tested for 1 day at 70? C. and 7 days at 70? C.

[0261] The results are expressed in % preservation of adhesive force of the reference tape: CA=(Fm2/Fm1)?100 in

with: [0262] Fm2=Mean tape detachment forces after 20 h contact with silicone-treated support; and [0263] Fm1=Mean tape detachment forces without contact with silicone-treated support. [0264] Loop-tack: The loop-tack test consists of the determination of the force required to separate, at 300 mm/min, a loop of adhesive (TESA 7475) brought into contact, with no pressure, with a standard material. The ratio of the result between a clean adhesive and an adhesive complexed for 1 day at 23? C. makes it possible to assess the loss of adhesivity according to the FINAT 9 (FTM9) test known to those skilled in the art.

[0265] The final result will be the mean of the three measurements expressed in N/Inch (unit: 1 inch=2.54 cm). [0266] Release: The measurements of peeling forces were carried out with the standardized adhesives TESA 4651 and TESA 7475. The test specimens of the multi-layer item (adhesive in contact with silicone surface) were stored for 1 day at 23? C., 1 day at 70? C. and 7 days at 70? C. under the required pressure conditions, then tested at low peeling speed according to the FINAT 3 (FTM 3) test known to those skilled in the art.

[0267] The detachment force is expressed in cN/inch and is measured using a dynamometer, after placing the samples under pressure either at ambient temperature (23? C.) or at a higher temperature for accelerated aging tests (generally 70? C.).

[0268] The results are reported in table 3 below.

TABLE-US-00003 TABLE 3 Results of the evaluation of the multi-layer items. Coatings obtained using silicone oil comprising pendant acrylate functions. Comparative Comparative Example 1 Item example 1 example 2 (invention) Composition A1 100 100 100 P1 1 P2 1 P3 1 Support Lumirror polyester film Speed 100 m/min Lamp 100 W/cm Deposit (g/m.sup.2) 1.07 1.09 1.05 Reaction by-product: yes no no benzaldehyde Reaction by-product: yes yes no isopropanol Coating characterization Smear A A A Rub-off 10 10 10 Dewetting 10 10 10 Extractables (100 cm.sup.2) (%) 3.05 3.42 3.45 Multi-layer item characterization SubAd 1 d@70? C. 1.0 1.0 1.0 (ref TESA 7475) SubAd 1 d@70? C. (%) 90 89 89 SubAd 7 d@70? C. 0.94 1.01 0.98 (ref TESA 7475) SubAd 7 d@70? C. (%) 94 100 97 Loop tack (N) according to 23.8 25.1 22.5 FINAT3 (1 d@23? C.) Loop tack (%) according to 111 117 105 FINAT3 (1 d@23? C.) Release Tesa 7475 1 d @ 23? C. 8.6 8.7 8.4 1 d @ 70? C. 11.73 10.37 10.23 7 d @70? C. 16.43 12.56 12.38 Release Tesa 4651 1 d @ 23? C. 26.9 28.1 25.9 1 d @ 70? C. 43.1 35.4 32.2 7 d @70? C. 70.1 70.3 71.7
Contrary to comparative tests 1 and 2, example 1 according to the invention does not exhibit any release of benzaldehyde or of isopropanol during the UV-crosslinking of the silicone composition coated on a polyester film; the crosslinking of the coating is optimal and the peeling forces of the adhesive of the multi-layer item are satisfactory even after aging.

TABLE-US-00004 TABLE 4 Coatings obtained from a silicone oil comprising pendant acrylate functions or from a mixture of 2 silicone oils comprising pendant acrylate functions - varying amounts of photoinitiators. Item Examples according to the invention Composition Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Ex. 13 A1 100 100 99 99 97.5 97.5 97.5 95 95 95 A2 1 1 2.5 2.5 2.5 5 5 5 P3 2 4 2 4 1 2 4 1 2 4 Support OPP CR30 film (Innovia) Speed 50 m/min Lamp 100 W/cm Deposit (g/m.sup.2) 1.01 0.94 0.97 0.86 0.93 1.00 0.91 0.90 0.85 0.89 RC coating characterization Smear A A A A A A A A A A Rub-off @ 0 d 10 10 10 10 10 10 10 10 10 10 Rub-off @ 7 d 10 10 10 10 10 10 10 10 10 10 Extractions (%) 3.8 3.8 3.7 5.1 5.4 5.2 5.0 4.2 4.7 4.8 Multi-layer item characterization Subadhesion 0.95 0.94 0.88 0.97 0.93 0.94 0.98 0.92 0.9 0.9 1 d@23? (ref Tesa7475) Subadhesion 99.0 97.9 91.7 101.0 96.9 97.9 102.1 95.8 93.8 93.8 1 d@23? C. (%) Release TESA7475 1 d @ 23? C. 3.8 4.7 3.6 4.5 2.9 3.6 4.7 2.9 3.5 5.3 1 d @ 70? C. 5.3 7.4 5.3 7.5 4.0 5.1 7.6 4.0 5.6 8.8 7 d @ 70? C. 7.5 27.8 7.7 9.3 5.9 7.0 9.9 6.0 8.3 11.6 Release TESA4651 1 d @ 23? C. 10.1 13.4 8.3 11.5 6.1 7.4 12.2 5.6 7.4 12.9 1 d @ 70? C. 17.8 26.9 13.4 23.2 9.3 12.7 23.8 9.3 13.7 28.2 7 d @ 70? C. 22.2 39.3 17.8 29.1 14.5 15.7 31.0 14.0 17.4 36.4
All the examples according to the invention exhibit no release of benzaldehyde and/or isopropanol during the UV-crosslinking of the silicone compositions based on an oil comprising acrylate functions according to the invention or on the mixture of two oils comprising acrylate functions according to the invention, coated on a polypropylene film. Furthermore, the crosslinking of the coatings is optimal and the peeling forces of the adhesive of the multi-layer items are correct, regardless of the photoinitiator concentration.

TABLE-US-00005 TABLE 5 Coatings obtained from a mixture of two silicone oils comprising acrylate functions which are respectively pendant and at the chain ends: Comparative Item example 3 Example 14 Composition A3 30 30 A5 70 70 P2 2 P3 2 Support Lumirror PET film Speed 50 m/min Lamp 100 W/cm Deposit (g/m.sup.2) 0.75 0.73 Reaction by-product: no no benzaldehyde Reaction by-product: isopropanol yes no RC coating characterization Smear B A Rub-off 2 10 Dewetting 0 10 Extractables (100 cm.sup.2) (%) 17.4 7.3 Multi-layer item characterization SubAd 1 d@70? C. (ref TESA 7475) ND 0.9 SubAd 1 d@70? C. (%) ND 84.9 SubAd 7 d@70? C. (ref TESA 7475) ND 0.92 SubAd 7 d@70? C. (%) ND 85.44 Loop tack (N) according to FINAT3 ND 20.8 (1 d@23? C.) Loop tack (%) according to FINAT3 ND 75.9 (1 d@23? C.) Release Tesa 7475 1 d @ 23? C. ND 6.52 1 d @ 70? C. ND 7.9 7 d @70? C. ND 20.2 Release Tesa 4651 1 d @ 23? C. ND 13.69 1 d @ 70? C. ND 11.5 7 d @70? C. ND 11.94 ND = not determined since high content of extractables
Contrary to comparative example 3, example 14 according to the invention exhibits no release of benzaldehyde or of isopropanol during the UV-crosslinking of the silicone composition based on two silicone oils comprising acrylate functions according to the invention, coated on a polyester film. Furthermore, the crosslinking of the coating and the peeling forces of the adhesive of the multi-layer item are correct.

[0269] The photoinitiator used in comparative example 3 does not allow satisfactory crosslinking of the composition based on two silicone oils comprising acrylate functions which are respectively pendant and at the chain ends (content of extractables 17.4%).

TABLE-US-00006 TABLE 6 Coatings obtained from a mixture of a silicone oil comprising pendant acrylate functions and of a silicone oil comprising chain-end and pendant acrylate functions. Example 15 Item Invention Composition A3 30 A4 70 P3 2 Support Lumirror PET film Speed 50 m/min Lamp 100 W/cm RC coating characterization Deposit (g/m.sup.2) 0.74 Smear A Rub-off 10 Extractables (100 cm.sup.2) dosage value 3.6 Extractables (100 cm.sup.2) (%) 6.5 Multi-layer item characterization Subadhesion 1 d@70? c. (ref Tesa 0.85 7475) Subadhesion 1 d@70? c. (%) 79.73 Subadhesion 7 d@70? c. (ref Tesa 0.89 7475) Subadhesion 7 d@70? c. (%) 82.91 Loop tack (N) according to FINAT3 19.42 (1 d@23? C.) Loop tack (%) according to FINAT3 70.90 (1 d@23? C.) Release TESA 7475 1 d @ 23? C. 7.685 1 d @ 70? C. 7.885 7 d @70? C. 16.365 Release TESA 4651 1 d @ 23? C. 10.155 1 d @ 70? C. 10.6 7 d @70? C. 36.18
Example 15 according to the invention exhibits no release of benzaldehyde and/or isopropanol during the UV-crosslinking of a composition comprising a mixture of a silicone oil comprising acrylate functions which are solely pendant and of a silicone oil comprising pendant and chain-end acrylate functions.

[0270] Furthermore, the crosslinking of the coating and the peeling forces of the adhesive of the multi-layer item are correct.

[0271] All of these examples clearly show that the use of a photoinitiator of acylphosphine oxide type, and more particularly ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate, during the production of a self-adhesive multi-layer item makes it possible, on the one hand, to protect the operators and the environment and, on the other hand, to produce optimal properties regardless of the acrylate silicone oils used in the silicone composition employed, which is not the case with the photoinitiators that are most widely used industrially.