Adhesion promoter

Abstract: An adhesion promoter which is a silane or polysiloxane having in each molecule at least one organic group possessing aliphatic unsaturated group and at least one organic group possessing amino group or having in each molecule at least one organic group possessing both aliphatic unsaturation and an amino group is useful for improving the adhesion of radiation curable organopolysiloxane compositions to substrates.

Description: The present invention relates to an adhesion promoter for organopolysiloxane compositions which are cured by radiation, such as by an electron beam and ultraviolet radiation. While heating is primarily used in the prior art to cure organopolysiloxane compositions, this approach does require high temperatures and long curing times. Accordingly, the last several years have been witness to research into compositions and methods by which curing can be conducted at lower temperatures and in shorter times. This research has resulted in the appearance of organopolysiloxane compositions which are cured by exposure to radiation such as an electron beam, ultraviolet radiation, etc. Such compositions are exemplified by compositions which are obtained by mixing a photosensitizer into the mixture of a mercapto groupcontaining organopolysiloxane and a vinyl group-containing organopolysiloxane as described in Canadian Patent No. 1,019,693 issued to Gant October 25, 1977, and by compositions composed of photosensitizer plus organopolysiloxane having acryloxy or methacryloxy groups as described in Japanese Patent Publication Number 53-2911 [2,911/78]. However, these organopolysiloxane compositions do not adhere well to the surfaces of various substrates, such as plastics, rubbers, metals, etc., after curing, and as a consequence are easily removed by rubbing with the finger, etc. EP-A-0 081 444 is concerned with liquid organopolysiloxane compositions which are readily photocured by UV radiation in thin layers to form a variety of non-stick coatings on various cellulosic materials. Hardening is improved by combining an aminopolyalkoxysilane (1) with an hydroxysilyl-ended polysiloxane (2) which is free of Si-H bonds and is also free of organic radicals with "activated" (photoactive) ethylenic unsaturation. Photoactive radicals such as acryloxy and methacryloxy radicals are accordingly excluded from the polysiloxane (2) but the latter may include alkenyl radicals having 2 to 4 carbon atoms, such as vinyl radicals, provided these represent at most 5% of the totality of the hydrocarbon radicals carried by the organopolysiloxane (2). Mixtures of such polysiloxanes (2) may also be used. The aminopolyalkoxysilylated compound (1) may also carry various substituents and may comprise mixtures thereof. In order that the combination of the compounds (1) and (2) may harden to an acceptable viscosity, generally between 20 and 20,000 mPa/s, and preferably between 50 and 3000 mPa/s, the ratio of Sibonded hydroxyls (OH) carried by the compound (2) to that of Si-bonded alkoxys OR) carried by the compound (1) is generally not greater than 1, preferably between 0.1 and 1, and more preferably between 0.1 and 0.9. Conventional condensation catalysts such as the alkyl titanates, e.g. triisopropyl titanate (TIPT), are generally employed. The object of the present invention is to provide an adhesive promoter which, in contrast to the state of the art, when blended into a radiation-curable organopolysiloxane or a composition thereof, will generate a substantial increase in adhesion for various substrates. This invention relates to an organopolysiloxane composition comprising: a) a radiation-curable organopolysiloxane selected from the group consisting of mercaptoalkylcontaining organopolysiloxanes, organopolysiloxanes having alkenyl groups, acryloxycontaining organopolysiloxanes, methacryloxycontaining organopolysiloxanes, styryl-containing organopolysiloxanes, acrylamide-containing organopolysiloxanes, methacrylamide-containing organopolysiloxanes, and mixtures thereof, and b) from 0.1 to 30 parts by weight per 100 parts by weight of component (a) of an adhesion promoter selected from the group consisting of copolymers composed of vinylmethyl-siloxane units, aminopropylmethylsiloxane units and dimethyl siloxane units; copolymers composed of acryloxypropylmethyl-siloxane units, aminopropylmethylsiloxane units and dimethylsiloxane units; cohydrolyzates of vinyl-containing alkoxysilane and aminoalkylcontaining alkoxysilane; copolymers composed of trimethylsiloxy units, gamma-acryloxypropylmethylsiloxane units, gamma-aminopropylsiloxane units and dimethylsiloxane units; copolymers composed of trimethylsiloxy units, gammaaminopropylmethylsiloxane units, vinylmethylsiloxane units and dimethylsiloxane units; and copolymers composed of trimethylsiloxy units, N-beta-(aminoethyl)-gamma-aminopropylmethylsiloxane units and dimethylsiloxane units, wherein some of the amino hydrogens have been reacted with acrylic chloride to provide the acrylic group. The invention also relates to a method of providing a substrate with an improved radiation-cured organopolysiloxane coating, which method comprises blending into a radiation-curable organopolysiloxane as defined just above as component (a), from 0.1 to 30 parts by weight of an adhesion promoter (b) as defined above per 100 parts by weight of component (a); coating the substrate with the resulting composition; and exposing the coated substrate to radiation to form a radiation-cured coating on said substrate. The invention also relates to the use of a component as defined hereinbefore for component (b), as an adhesion promoter in a composition comprising a radiation curable organosiloxane component (a), also as defined hereinbefore, wherein the component (b) is added to the component (a) in a proportion of 0.1 to 30 parts by weight of (b) per 100 parts by weight of (a). The organopolysiloxane adhesion promoters of the invention have, in each molecule, at least one organic group possessing aliphatic unsaturation and at least one organic group possessing an amino group, or at least one organic group possessing both aliphatic unsaturation and the amino group. The organic groups possessing aliphatic unsaturation are exemplified by lower alkenyl groups such as vinyl, allyl and propenyl, for example, and gamma-acrylamidopropyl, and gamma-methacrylamidopropyl, and the amino containing organic groups are exemplified by aminoalkyl groups such as aminomethyl, aminoethyl and aminopropyl, for example. Organic groups possessing both aliphatic unsaturation and the amino groups are exemplified by the N-beta-(aminoethyl)gamma-aminopropyl group which has been acrylamidated or methacrylamidated at an amino group. Preferred radiation curable compositions comprise a radiation curable organopolysiloxane according to the invention as defined hereinbefore as component (a), and from 0.1 to 30 parts by weight of an adhesion promoter composition as defined above per 100 parts by weight of component (a) , the radiation-curable organopolysiloxane. Preferred examples of the organopolysiloxane compositions described as component (b) include cohydrolyzates of vinyltrimethoxysilane and N-beta(aminoethyl)-gamma-aminopropyltrimethoxysilane; copolymers consisting of trimethylsiloxy units, gammaacryloxypropylmethylsiloxane units, gammaaminopropylsiloxane units and dimethylsiloxane units; copolymers consisting of trimethylsiloxy units, gammaaminopropylmethylsiloxane units, vinylmethylsiloxane units and dimethylsiloxane units; and copolymers consisting of trimethylsiloxy units, N-beta(aminoethyl)gamma-aminopropylmethylsiloxane units and dimethylsiloxane units wherein some of the amino hydrogens are reacted with acrylic chloride to provide the acrylic group. The organopolysiloxanes of the invention may be, for example, cohydrolysis condensates involving vinyl-containing alkoxysilanes such as vinylmethylsiloxane-aminopropylmethylsiloxane-dimethylsiloxane copolymers composed of vinylmethylsiloxane units, aminopropylmethylsiloxane units, and dimethylsiloxane units; acryloxypropylmethylsiloxane-aminopropylmethylsiloxanedimethylsiloxane copolymers; and organopolysiloxanes obtained by the acrylamidation of part of the amino groups of an aminoalkyl group-containing organopolysiloxane. Preferred among these are organopolysiloxanes obtained by the cohydrolysis condensation of vinyl-containing alkoxysilane and aminoalkyl-containing alkoxysilane, vinylmethylsiloxane-aminopropylmethylsiloxanedimethylsiloxane copolymers, and acryloxypropylmethylsiloxane-aminopropylmethylsiloxanedimethylsiloxane copolymers. The cohydrolysis condensates of vinyl-containing alkoxysilane and aminoalkyl-containing alkoxysilane are particularly preferred. As examples of the synthesis of such organopolysiloxanes, one can cite the reaction of vinylbenzyl chloride with gamma-(2-aminoethyl) aminopropyltrimethoxysilane; the reaction of benzyl chloride with aminopropyltrialkoxysilane; the cohydrolysis in the presence of traces of water of vinyl- containing alkoxysilane, such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(beta-methoxyethoxy)silane, etc., with aminoalkyl-containing alkoxysilane such as aminomethyltri- methoxysilane, beta-aminoethyltrimethoxysilane, gamma- aminopropyltrimethoxysilane, N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane, etc.; the partial amidation of the amino groups of an aminoalkyl-containing polysiloxane using acrylic chloride or methacrylic chloride in a molar deficiency based on the amino groups in said polysiloxane; and copolymerization of a vinyl group-containing siloxane with an aminoalkyl group-containing siloxane. The adhesion promoter of the invention is used by adding and blending it into a silicone composition which can be cured by exposure to radiation such as an electron beam, ultraviolet radiation, etc. In such a case, the adhesion promoter can be used as the single species, or as the mixture of two or more species. Radiation-curable organopolysiloxanes and their compositions into which the adhesion promoter of the present invention may be blended are exemplified by compositions having as their essential component at least one type of mercaptoalkyl group-containing organopolysiloxane organopolysiloxane having alkenyl groups such as vinyl, allyl, propenyl, etc., acryloxy group-containing or methacryloxy group-containing organopolysiloxane, styryl group-containing organopolysiloxane, or acrylamide-containing or methacrylamide-containing organopolysiloxane, and containing as necessary various additives such as, for example, reinforcing fillers, extender fillers, dyes and pigments, heat stabilizers, flame retardants, etc. The quantity of addition of this invention's adhesion promoter to the radiation-curable organopolysiloxane or composition thereof will depend on the type of organopolysiloxane, and on whether optional additives are present, and if so, on their type and compounding proportions. As a consequence, this value cannot be given unconditionally, but roughly will be 0.1 to 30 weight parts. Radiation-curable organopolysiloxane compositions which contain the invention's adhesion promoter have an excellent radiation curability, and adhere well to diverse substrates in contact with such compositions during their curing. Examples The invention will be explained in the following with reference to illustrative examples. In the examples, parts = parts by weight and curability and adhesion testing was conducted as follows. Curability and adhesion testing The radiation-curable organopolysiloxane composition containing adhesion promoter was coated on the surface of the substrate and then cured by exposure to radiation. The surface of the obtained cured coating was then rubbed with a finger ten times. Curing of the coating was taken to be unsatisfactory when a cloudiness was induced, a condition denoted as "smearing." Furthermore, in the event of exfoliation, adhesion by the coating to the substrate was also taken to be unsatisfactory, a condition denoted as "rub off." EXAMPLE 1 An electron beam-curable organopolysiloxane composition was prepared in the form of the mixture of 50 parts of a trimethylsiloxy-terminated dimethylsiloxane-gamma- mercaptopropylmethylsiloxane copolymer having ten gamma-mercaptopropylmethylsiloxane units in each molecule and having a degree of polymerization of 200, and 50 parts of a dimethylvinylsiloxy-terminated dimethylsiloxanemethylvinylsiloxane copolymer having 3 methylvinylsiloxane units and a degree of polymerisation of 300. 148 Parts vinyltrimethoxysilane (SZ6300 from Toray Silicone Co., Ltd.) and 228 parts N-beta-(aminoethyl)-gamma- aminopropyltrimethoxysilane (SH6020 from Toray Silicone Co., Ltd.) were placed in a three-neck flask equipped with stirrer and reflux condenser. This was stirred at 50°C for 10 minutes while 6 g ion-exchanged water was added dropwise in order to prepare an adhesion promoter in the form of the cohydrolyzate of vinyltrimethoxysilane and N-beta-(aminoethyl )-gamma-aminopropyltrimethoxysilane. One part of this adhesion promoter was added and mixed to homogeneity into 100 parts of the electron beam-curable organopolysiloxane composition. The obtained mixture was uniformly applied in a thickness of 1.0 g per square meter on polyethylene-laminated paper, and was then cured by exposure to a 5 Mrad electron beam. The cured coating was tested for curability and adhesion, and these results are reported in Table 1. For comparison, compositions were prepared in which one contained only vinyltrimethoxysilane in place of the above adhesion promoter (Comparison Example 1), and in which one contained only N-beta-(aminoethyl)gamma-aminopropyltrimethoxysilane in place of the above adhesion promoter (Comparison Example 2). These compositions were tested for curability and adhesion, and these results are reported in Table 1 as Comparison Example 1 and Comparison Example 2, respectively. PROPERTY Example 1 Comparison Example 1 Comparison Example 2 smear no yes no rub off no --- yes EXAMPLE 2 2 Parts benzophenone was added and blended into 100 parts of the electron beam-curable organopolysiloxane composition whose preparation is described in Example 1 to afford an ultraviolet-curable organopolysiloxane composition. To 100 parts of this composition was added 10 parts of a trimethylsiloxy- terminated organopolysiloxane (degree of polymerization = 70) composed of gamma-acryloxypropylmethylsiloxane units : gamma-aminopropyl-methylsiloxane units : dimethylsiloxane units in a 3 : 3 : 64 molar ratio, followed by mixing to homogeneity. This was applied in a thickness of 1.0 g per square meter on glassine paper, and was then exposed to ultraviolet energy from a 160 kW/cm mercury lamp for 1 second at a distance of 10 cm. The curability and adhesion of the cured coating were then evaluated, and these results are reported in Table 2. For comparison, the curability and adhesion of the above ultraviolet-curable organopolysiloxane composition, without the addition of the adhesion promoter, were evaluated as above, and these results are reported in Table 2 as Comparison Example 3. PROPERTY Example 2 Comparison Example 3 smear no no rub off no yes EXAMPLE 3 To prepare the adhesion promoter, a mixture of aminoethylaminopropyldimethoxysilane hydrolyzate, polydimethylsiloxane cyclics, polymethylvinylsiloxane cyclics, and hexamethyldisiloxane was equilibrated to afford a trimethylsiloxy-terminated organopolysiloxane (degree of polymerization = 202) composed of gamma-aminopropylmethylsiloxane units : vinylmethylsiloxane units : dimethylsiloxane units in a 5 : 5 : 190 molar ratio. An electron beam-curable organopolysiloxane composition was prepared by mixing 50 parts of this organopolysiloxane to homogeneity with 50 parts of a trimethylsiloxy-terminated organopolysiloxane composed of mercaptopropylmethylsiloxane units : dimethylsiloxane units in a 15 : 185 molar ratio. The resulting composition was uniformly applied at 1.0 g per square meter on polyethylene-laminated paper, and was then cured by exposing this coated surface to a 1 Mrad electron beam. Curability and adhesion tests were then conducted on this cured coating, and the these results are reported in Table 5. For comparison, a composition was prepared which contained, in place of the above adhesion promoter, a trimethylsiloxy-terminated organopolysiloxane composed of vinylmethylsiloxane units : dimethylsiloxane units in a 5 : 190 molar ratio. It was subjected to curability and adhesion testing, and these results are also reported in Table 3 as Comparison Example 4. PROPERTY Example 3 Comparison Example 4 smear no no rub off no yes EXAMPLE 4 To prepare an organopolysiloxane having both the acrylic group and amino group in the same molecule, acrylic chloride (at 0.8 moles per 1 mole amino hydrogen in the following polysiloxane) was added to and reacted with a trimethylsiloxy- terminated organopolysiloxane (degree of polymerization = 77) composed of 5 moles N-beta-(aminoethyl)-gamma- aminopropylmethylsiloxane units and 70 moles dimethylsiloxane units. An ultraviolet-curable organopolysiloxane composition was prepared by mixing 5 parts dimethyl benzil ketal into the electron beam-curable organopolysiloxane composition used in Example 1. Ten parts of the organopolysiloxane prepared as described above was added to 100 parts of this UV-curing organopolysiloxane composition. This mixture was uniformly applied at 0.3 g per square meter on polyethylene film, followed by exposure to ultraviolet radiation from a 160 W/cm high-pressure mercury lamp for 0.05 seconds. The curability and adhesion were then evaluated, and these results are reported in Table 4. For comparison, organopolysiloxane in which all amino groups were amidated was synthesized as above with the exception that the acrylic chloride was added at twice the above quantity. Using this organopolysiloxane in place of the above adhesion promoter, the curability and adhesion of the cured coating were examined as above, and these results are reported in Table 4 as Comparison Example 5. PROPERTY Example 4 Comparison Example 5 smear no no rub off no yes Effects of the Invention Because the adhesion promoter of the present invention is a polysiloxane having in each molecule at least one organic group possessing aliphatic unsaturation and at least one organic group possessing the amino group, or a polysiloxane having in each molecule at least one organic group containing both aliphatic unsaturation and the amino group, when it is blended into a radiation (electron beam, ultraviolet radiation, etc.)-curable organopolysiloxane or composition thereof, it characteristically provides a substantial improvement in the adhesion of such organopolysiloxanes or their compositions to various substrates.

Claims: An organopolysiloxane composition comprising: a) a radiation-curable organopolysiloxane selected from the group consisting of mercaptoalkylcontaining organopolysiloxanes, organopolysiloxanes having alkenyl groups, acryloxycontaining organopolysiloxanes, methacryloxycontaining organopolysiloxanes, styryl-containing organopolysiloxanes, acrylamide-containing organopolysiloxanes, methacrylamide-containing organopolysiloxanes, and mixtures thereof, and b) from 0.1 to 30 parts by weight per 100 parts by weight of component (a) of an adhesion promoter selected from the group consisting of copolymers composed of vinylmethyl-siloxane units, aminopropylmethylsiloxane units and dimethyl siloxane units; copolymers composed of acryloxypropylmethyl-siloxane units, aminopropylmethylsiloxane units and dimethylsiloxane units; cohydrolyzates of vinyl-containing alkoxysilane and aminoalkyl-containing alkoxysilane; copolymers composed of trimethylsiloxy units, gamma-acryloxypropylmethylsiloxane units, gamma-aminopropylsiloxane units and dimethylsiloxane units; copolymers composed of trimethylsiloxy units, gamma-aminopropylmethylsiloxane units, vinylmethylsiloxane units and dimethylsiloxane units; and copolymers composed of trimethylsiloxy units, N-beta-(aminoethyl)-gamma-aminopropylmethylsiloxane units and dimethylsiloxane units, wherein some of the amino hydrogens have been reacted with acrylic chloride to provide the acrylic group. A composition according to Claim 1, wherein the organopolysiloxane compound wherein said adhesion promoter (b) is a cohydrolyzate of vinyltrimethoxy silane and N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane. A composition according to Claim 1, wherein said adhesion promoter (b) is a copolymer consisting of trimethylsiloxy units, gamma-acryloxypropylmethylsiloxane units, gamma-aminopropylsiloxane units and dimethylsiloxane units. A composition according to Claim 1, wherein said adhesion promoter (b) is a copolymer consisting of trimethylsiloxy units, gamma-aminopropylmethylsiloxane units, vinylmethylsiloxane units and dimethylsiloxane units. A composition according to Claim 1, wherein said adhesion promoter (b) is a copolymer consisting of trimethylsiloxy units, N-beta-(aminoethyl)-gamma-aminopropylmethylsiloxane units and dimethylsiloxane units, some of the amino hydrogens being reacted with acrylic chloride to provide the acrylic group. The use of a component as defined at (b) in Claim 1 as an adhesion promoter in a composition comprising a radiation-curable organosiloxane component (a) as also defined in Claim 1, said component (b) being added to said component (a) in a proportion of 0.1 to 30 parts by weight of (b) per 100 parts by weight of (a). A method of providing a substrate with an improved radiation-cured organopolysiloxane coating, which method comprises blending into a radiationcurable organopolysiloxane defined as component (a) in Claim 1 above, from 0.1 to 30 parts by weight per 100 parts by weight of component (a), of an adhesion promoter as defined at (b) in any one of Claims 1 to 5; coating the substrate with the resulting composition; and exposing the coated substrate to radiation to form a radiation-cured coating on said substrate.

Inventors: HAMADA YUJI, MASAOKA HIROSHI, SASAKI SHOSAKU, HAMADA, YUJI, MASAOKA, HIROSHI, SASAKI, SHOSAKU
Applicants: TORAY SILICONE CO, TORAY SILICONE CO., LTD.
Application year: 1987
Main classification: C08K5
IPC codes: C09D4, C08K5, C08L83, C08F290, C09J4, C08F299, C09J155, C08G77, C09D183