Patent Application
20230416563
This invention pertains to a silicone emulsion and methods for its preparation and use. More particularly, this invention pertains to an aqueous silicone emulsion, which is curable to form a silicone release coating suitable for use on various substrates, including paper and plastic.
Curable silicone compositions can be coated on substrates and cured to form coatings to improve or change various properties of the substrates. The substrates to which the compositions are applied can contain one or more materials. Such materials can be fibrous, which may be cellulosic, e.g., paper substrates such as paper or cardboard. The paper may be glazed or unglazed, calendared or un-calendared. Alternatively, the substrate can be plastics-based instead of paper-based, comprising for example acrylic, polycarbonate or polyethylene terephthalate material, or it can be a laminate paper/plastics.
Curable silicone compositions can be aqueous, solvent based or solventless compositions. Solventless compositions, such as SYL-OFF™ 7000 Coating from Dow Silicones Corporation of Midland, Michigan, USA, can be applied at a relatively high thickness (≥1 μm) and suffer from the drawback that they cannot be coated at reduced thickness using existing coating machinery. Furthermore, due to relatively high viscosities of the solventless compositions, undesirable misting during processing, and surface defects in the resulting coating, can occur particularly at high production speeds.
Aqueous compositions may be desired in several applications such as those requiring well controlled low thickness deposition and those bound to food regulations (e.g., food contact applications). A coated paper suitable for food contact applications may be obtained by treating a paper substrate with a compound or composition for forming a layer on the paper. A known treatment is based on fluorinated compounds that are able to provide non-stick properties by forming a film having low surface energy, which is resistant to chemical agents thereby providing oil, fat and water repellence to the treated paper. However environmental and health concerns were raised about fluorinated compounds, and the industry trend is to restrict or ban their use by various regulations, especially in the food packaging industry.
Another approach has been to treat a paper substrate with a mixture of polyvinyl alcohol and a chromate-fatty acid complex. However the use of heavy metal such as chromium has also raised environmental and health concerns in food packaging related uses. Other treatments may confer some oleophobicity to the paper, but they often require relatively high amounts of material to be effective and form a thick coating on the paper, which may be detrimental to the mechanical properties and durability upon creasing or folding of the paper. Furthermore, use of high amounts of material may not be cost effective.
A silicone release coating emulsion comprises: (A) an aliphatically unsaturated polyorganosiloxane composition comprising a hexenyl-functional polyorganosiloxane, (B) a polyorganohydrogensiloxane, (C) a hydrosilylation reaction catalyst, (D) a hydrosilylation reaction inhibitor, (E) water, (F) a buffer, and one or both of (G) a surfactant and (H) a polyvinyl alcohol.
The silicone release coating emulsion (emulsion) described above may optionally further comprise an additional starting material selected from the group consisting of (I) a biocide, (J) an anti-foam, and (K) a combination of both (I) and (J). Alternatively, the emulsion may consist essentially of (A) the aliphatically unsaturated polyorganosiloxane composition comprising the hexenyl-functional polyorganosiloxane, (B) the polyorganohydrogensiloxane, (C) the hydrosilylation reaction catalyst, (D) the hydrosilylation reaction inhibitor, (E) water, (F) the buffer, and one or both of (G) the surfactant and (H) the polyvinyl alcohol; and optionally the additional starting material selected from the group consisting of (I) the biocide, (J) the anti-foam, and (K) the combination of both (I) and (J). Alternatively, the emulsion may consist of (A) the aliphatically unsaturated polyorganosiloxane composition comprising the hexenyl-functional polyorganosiloxane, (B) the polyorganohydrogensiloxane, (C) the hydrosilylation reaction catalyst, (D) the hydrosilylation reaction inhibitor, (E) water, (F) the buffer, and one or both of (G) the surfactant and (H) the polyvinyl alcohol; and optionally the additional starting material selected from the group consisting of (I) the biocide, (J) the anti-foam, and (K) the combination of both (I) and (J).
Starting material (A) in the emulsion described above is an aliphatically unsaturated polyorganosiloxane composition. The amount of starting material (A) in the emulsion is 100 weight parts. Starting material (A) the aliphatically unsaturated polyorganosiloxane composition comprises (A1) a hexenyl-functional polyorganosiloxane and optionally (A2) a vinyl-functional polyorganosiloxane.
Starting material (A1) is the hexenyl-functional polyorganosiloxane. The hexenyl-functional polyorganosiloxane may have unit formula (A1-I):
(R13SiO1/2)a(R12R2SiO1/2)b(R12SiO2/2)c(R1R2SiO2/2)d(SiO4/2)e, where each R1 is an independently selected alkyl group or aryl group, R2 is a hexenyl group, subscript a is 0 to 4, subscript b is 0 to 4, subscript c is 0 to 400, subscript d is 0 to 50, and subscript e is 0 or 1, with the provisos that (a+b)=2 to 4, (b+d)≤2, (a+b+c+d) is 15 to 400. Suitable alkyl groups for R1 may have 1 to 6 carbon atoms, such as methyl, ethyl, propyl (including isopropyl and n-propyl), butyl (including n-butyl, t-butyl, sec-butyl, and isobutyl), pentyl (including linear, branched and cyclic 5 carbon groups), and hexyl (including linear, branched and cyclic hexyl groups). Suitable aryl groups include for R1 may have 6 to 20 carbon atoms, such as phenyl, tolyl, xylyl, naphthyl, and styryl. Alternatively the aryl group may be phenyl. Alternatively, each R1 may be methyl or ethyl. Alternatively, each R1 may be methyl or phenyl. Alternatively, each R1 may be methyl. The hexenyl-functional polyorganosiloxane may be linear or branched.
Alternatively, the hexenyl-functional polyorganosiloxane may be linear, when subscript e=0. The linear hexenyl-functional polyorganosiloxane may comprise unit formula (A1-II): (R13SiO1/2)a(R12R2SiO1/2)b(R12SiO2/2)c(R1R2SiO2/2)d, where R1 and R2 are as described above, subscript a is 0, 1 or 2; subscript b is 0, 1 or 2; subscript c is 0 to 400; and subscript d is 0 to 50; with the provisos that (a+b)=2, (b+d)≤2, and (a+b+c+d) is 15 to 400.
Alternatively, the hexenyl-functional polyorganosiloxane may comprise a hexenyl-endblocked polydialkylsiloxane of unit formula (A1-III): (R12R2SiO1/2)2(R12SiO2/2)c, where each R1 is an alkyl group as described above, R2 is as described above, and subscript c is 15 to 400.
Alternatively, the hexenyl-functional polyorganosiloxane may comprise a poly(dialkyl/alkylhexenyl)siloxane of unit formula (A1-IV):
(R2R12SiO1/2)2(R12SiO2/2)c(R1R2SiO2/2)d, where each R1 is an alkyl group, R2 is as described above, subscript c is 0 to 400, and subscript d is 2 to 50.
Starting material (A1) may comprise a linear hexenyl-functional polyorganosiloxane such as
Methods of preparing linear hexenyl-functional polydiorganosiloxanes described above for starting material (A1), such as hydrolysis and condensation of the corresponding organohalosilanes and oligomers or equilibration of cyclic polydiorganosiloxanes, are known in the art, see for example U.S. Pat. No. 3,284,406 to Nelson; U.S. Pat. No. 4,772,515 to Hara et al.; U.S. Pat. No. 5,169,920 to Okawa; U.S. Pat. No. 5,317,072 to Bokerman et al.; and U.S. Pat. No. 6,956,087 Lai et al., which disclose preparing linear polydiorganosiloxanes with alkenyl groups. Hexenyl-functional polydiorganosiloxanes may be prepared by varying appropriate starting materials used in such methods.
In addition to (or instead of) the above described linear hexenyl-functional polydiorganosiloxane, starting material (A1) may comprise a branched hexenyl-functional polyorganosiloxane. The branched hexenyl-functional polyorganosiloxane may have >0 to 5 mol % of quadrifunctional units when in formula (A1-I), subscript e has a value sufficient to provide >0 to 5 mol % of quadrifunctional units.
For example, the branched hexenyl-functional polyorganosiloxane may comprise a Q branched polyorganosiloxane of unit formula (A1-V):
(R13SiO1/2)q(R12R2SiO1/2)r(R12SiO2/2)s(SiO4/2)t, where R1 and R2 are as described above, and subscripts q, r, s, and t have average values such that 2≥q≥0, 4≥r≥0, 995≥s≥4, t=1, (q+r)=4, and (q+r+s+t)>50. Alternatively, the quantity (q+r+s+t) may have a value sufficient to impart a viscosity >170 mPa·s measured by rotational viscometry (as described below with the test methods). Alternatively, viscosity may be >170 mPa·s to 1000 mPa·s, alternatively >170 to 500 mPa·s, alternatively 180 mPa·s to 450 mPa·s, and alternatively 190 mPa·s to 420 mPa·s. Suitable branched hexenyl-functional polyorganosiloxanes for starting material (A1) can be made by known methods. For example, the branched hexenyl-functional polyorganosiloxanes for starting material (A1) (where subscript e >0 in the unit formula above) are exemplified by those disclosed in U.S. Pat. No. 6,806,339 to Cray et al. and U.S. Patent Publication 2007/0289495 to Cray et al. by varying appropriate starting materials.
Starting material (A2) is the vinyl-functional polyorganosiloxane. The vinyl-functional polyorganosiloxane may have unit formula (A2-I):
(R13SiO1/2)i(R12R3SiO1/2)f(R12SiO2/2)g(R1R3SiO2/2)h(SiO4/2)j, where each R1 is an independently selected alkyl group or aryl group as described above, R3 is a vinyl group, subscript i is 0 to 4; subscript f is 0 to 4; subscript g is 0 to 1400; subscript h is 0 to 200; and subscript j is 0 or 1; with the provisos that (i+f)=2 to 4, (f+h)≤2, and (i+f+g+h) is 15 to 1400. Alternatively, subscript g may be 0 to 1200. The vinyl-functional polyorganosiloxane may be linear or branched. For example, when subscript j=0, the vinyl-functional polyorganosiloxane may be linear.
Alternatively, the linear vinyl-functional polyorganosiloxane may comprise unit formula (A2-II): (R13SiO1/2)i(R12R3SiO1/2)f(R12SiO2/2)g(R1R3SiO2/2)h, where R1 is an independently selected alkyl group or aryl group as described above, R3 is a vinyl group, subscript i is 0, 1, or 2; subscript f is 0, 1, or 2; subscript g is 0 to 1200; and subscript h is 0 to 200; with the provisos that (i+f)=2, (f+h)≤2, (i+f+g+h) is 15 to 1200.
Alternatively, the linear vinyl-functional polyorganosiloxane may comprise a vinyl-endblocked polydialkylsiloxane of unit formula (A2-III) (R12R3SiO1/2)2(R12SiO2/2)g, where each R1 is an alkyl group as described above, R3 is a vinyl group, and subscript g is 15 to 1200.
Alternatively, the linear vinyl-functional polyorganosiloxane may comprise a poly(dialkyl/alkylvinyl)siloxane of unit formula (A2-IV):
(R3R12SiO1/2)2(R12SiO2/2)g(R1R3SiO2/2)h, where each R1 is an alkyl group as described above, R3 is a vinyl group, subscript g is 0 to 1200; subscript h is 2 to 200.
Starting material (A2) may comprise a linear vinyl-functional polyorganosiloxane such as
Methods of preparing linear vinyl-functional polydiorganosiloxanes described above for starting material (A2), such as hydrolysis and condensation of the corresponding organohalosilanes and oligomers or equilibration of cyclic polydiorganosiloxanes, are known in the art, see for example U.S. Pat. Nos. 3,284,406; 4,772,515; 5,169,920; 5,317,072; and 6,956,087.
In addition to (or instead of) the above described linear vinyl-functional polydiorganosiloxane, starting material (A2) may comprise a branched vinyl-functional polyorganosiloxane. The branched vinyl-functional polyorganosiloxane may have >0 to 5 mol % of quadrifunctional units to the branched vinyl-functional polyorganosiloxane. For example, the branched vinyl-functional polyorganosiloxane may unit formula (A2-V): (R13SiO1/2)q(R12R3SiO1/2)r(R12SiO2/2)s(SiO4/2)t, where R1 and R3 are as described above, and subscripts q, r, s, and t have average values such that 2≥q≥0, 4≥r≥0, 995≥s≥4, t=1, (q+r)=4, and (q+r+s+t)>50. Alternatively, the quantity (q+r+s+t) may have a value sufficient to impart a viscosity >170 mPa·s measured by rotational viscometry (as described below with the test methods). Alternatively, viscosity may be >170 mPa·s to 1000 mPa·s, alternatively >170 to 500 mPa·s, alternatively 180 mPa·s to 450 mPa·s, and alternatively 190 mPa·s to 420 mPa·s. Suitable branched vinyl-functional polyorganosiloxanes for starting material (A2) are known in the art and can be made by known methods, exemplified by those disclosed in U.S. Pat. No. 6,806,339 and U.S. Patent Publication 2007/0289495.
Starting material (A) the aliphatically unsaturated polyorganosiloxane composition is present in the emulsion in an amount of 100 weight parts (e.g., amount of starting material (A1) and amount of starting material (A2) combined=100 weight parts). The amount of starting material (A1) the hexenyl-functional polyorganosiloxane in (A) is 25 weight parts to 100 weight parts, and the amount of starting material (A2) in (A) is 0 to 75 weight parts. Alternatively, starting material (A1) may be present in an amount of 25 to <100 weight parts, alternatively >25 weight parts to <100 weight parts, alternatively 50 weight parts to <100 weight parts, and alternatively >50 weight parts to <100 weight parts. Starting material (A2) may be present in an amount of 0 to 75 weight parts, alternatively >0 to 75 weight parts, alternatively >0 to <75 weight parts, alternatively >0 to 50 weight parts, and alternatively >0 to <50 weight parts.
The selection of starting material (A1), starting material (A2) and the amounts of each will depend on various factors including the substrate on which the emulsion will be coated and the desired properties of the release coating prepared from the emulsion. For example, starting material (A1) may be a hexenyl-endblocked polydialkylsiloxane, and starting material (A2) may be a vinyl-endblocked polydialkylsiloxane. Alternatively, starting material (A1) may be a poly(dialkyl/alkylhexenyl)siloxane, and starting material (A2) may be a vinyldialkylsiloxy-endblocked polydialkylsiloxane of unit formula. Alternatively, starting material (A1) may be a poly(dialkyl/alkylhexenyl)siloxane, and starting material (A2) may be a poly(dialkyl/alkylvinyl)siloxane.
Alternatively, when starting material (A1) is a hexenyl-endblocked polydialkylsiloxane and starting material (A2) is a vinyl-endblocked polydialkylsiloxane, the amount of (A1) may be at least 50 weight parts, alternatively at least 75 weight parts, and at the same time up to <100 weight parts, alternatively up to 90 weight parts; and the amount of (A2) may be >0, alternatively at least 10 weight parts and at the same time up to 50 weight parts, alternatively up to 25 weight parts; each provided that the amounts of (A1) and (A2) total 100 weight parts. Alternatively, when starting material (A1) is a poly(dialkyl/alkylhexenyl)siloxane and starting material (A2) is a poly(dialkyl/alkylvinyl)siloxane, the amount of (A1) may be at least >50 weight parts, alternatively at least 75 weight parts, and alternatively at least 90 weight parts, and at the same time the amount of (A1) may be up to <100 weight parts, alternatively up to 90 weight parts. And, the amount of (A2) may be at least >0, alternatively at least 10 weight parts, while at the same time the amount of (A2) may be up to <50 weight parts, alternatively up to 25 weight parts. The above combinations of (A1) and (A2) may be particularly useful in making emulsions for preparing release coatings on paper substrates.
Alternatively, when starting material (A1) is a poly(dialkyl/alkylhexenyl)siloxane and starting material (A2) is a poly(dialkyl/alkylvinyl)siloxane, the amount of (A1) may be at least >25 weight parts, alternatively at least 33 weight parts, alternatively at least 50 weight parts, while at the same time the amount of (A1) may be up to <100 weight parts, alternatively up to 90 weight parts, alternatively up to 75 weight parts and alternatively up to 67 weight parts. And, the amount of (A2) may be at least 10 weight parts, alternatively at least 33 weight parts, alternatively at least 50 weight parts while at the same time the amount of (A2) may be up to 67 weight parts, alternatively up to 50 weight parts. The above combinations of (A1) and (A2) may be particularly useful in making emulsions for preparing release coatings on plastic substrates.
Starting material (B) in the emulsion is a polyorganohydrogensiloxane. The polyorganohydrogensiloxane may have unit formula
(R13SiO1/2)w(R12HSiO1/2)x(R12SiO2/2)y(R1HSiO2/2)z, where R1 is as described above, subscript w is 0, 1, or 2; subscript x is 0, 1, or 2; subscript y is 0 to 250, and subscript z is 1 to 250; with the provisos that (w+x)=2; (x+z)≥3; and a quantity (w+x+y+z) is 10 to 300. Alternatively, subscript w may be 2, and subscript x may be 0. Alternatively, subscript y may be >0 to 250.
Suitable polyorganohydrogensiloxanes for use herein are exemplified by:
Polyorganohydrogensiloxanes are also commercially available, such as those available from Gelest, Inc. of Morrisville, Pennsylvania, USA, for example, HMS-H271, HMS-071, HMS-993, HMS-301, HMS-301 R, HMS-031, HMS-991, HMS-992, HMS-993, HMS-082, HMS-151, HMS-013, HMS-053, and HMS-HM271. Methods of preparing linear and branched polyorganohydrogensiloxanes suitable for use herein, such as hydrolysis and condensation of organohalosilanes, are well known in the art, as exemplified in U.S. Pat. No. 2,823,218 to Speier, U.S. Pat. No. 3,957,713 to Jeram et al. and U.S. Pat. No. 4,329,273 to Hardman, et al.
Starting material (B) the polyorganohydrogensiloxane is used in the emulsion in an amount sufficient to provide a molar ratio of silicon bonded hydrogen atoms in starting material (B) to a combined amount of vinyl and hexenyl groups in starting material (A) (i.e., an SiH/Vi ratio) of 1.2/1 to 3.0/1, alternatively 1.4/1 to 2.5/1.
Starting material (C) in the emulsion is a hydrosilylation reaction catalyst. This catalyst will promote a reaction between the alkenyl groups in starting material (A) and the silicon bonded hydrogen atoms in starting material (B). Said catalyst may comprise a metal selected from Fe, Ni, Co, Zr, Ti, or a platinum group metal. Alternatively, the metal may comprise the platinum group metal. The platinum group metal may be selected from the group consisting of platinum, rhodium, ruthenium, palladium, osmium, and iridium. Alternatively, the platinum group metal may be platinum. The hydrosilylation reaction catalyst may be (C-I) a radiation activatable catalyst, i.e., capable of catalyzing hydrosilylation reaction after irradiation (exposure to actinic radiation, e.g., exposure to visible or UV light), (C-II) a hydrosilylation catalyst activatable by means other than irradiation, e.g., capable of catalyzing hydrosilylation reaction without irradiation, such as by heating, or (C-III) a combination of both (C-I) and (C-II).
Suitable radiation activatable catalysts for use as starting material (C-I) may be activated by exposure to radiation with a wavelength of 200 nm to 500 nm. Suitable radiation activatable hydrosilylation reaction catalysts include cyclopentadienyl platinum complexes such as η5-cyclopentadienyl)tri(α-alkyl)platinum (IV); cyclopentadienyltrimethylplatinum and trimethyl(methylcyclopentadienyl)platinum (IV), cyclooctadienyl platinum complexes such as η4-1,5-cyclooctadienediarylplatinum complexes; and Pt(II)-ß diketonate complexes such as bis(acetylacetonato)platinum (II). Examples of cyclopentadienyl platinum complexes are known in the art and are disclosed, for example in U.S. Pat. No. 4,510,094 to Drahnak; U.S. Pat. No. 4,600,484 to Drahnak; U.S. Pat. No. 4,916,169 to Boardman et al.; U.S. Pat. No. 6,127,446 to Butts; U.S. Pat. No. 6,451,869 to Butts; U.S. Pat. No. 6,376,569 to Oxman et al.; U.S. Pat. No. 8,088,878 to Koellnberger; and CN101925608B. Cyclooctadienyl platinum complexes are disclosed, for example, in U.S. Pat. No. 6,046,250 to Boardman et al. Platinum (II) beta-diketonate catalysts are disclosed, for example, in EP0398701B1 to Oxinan et al; U.S. Pat. No. 8,642,674 to Ikeno; and CN104031602A. U.S. Patent Application Publication 2005/0154079 to Walker et al.; U.S. Patent Application Publication 2011/0171400A1 to Thompson et al. and JP 03865638 B2 to Ikeno each disclose various radiation activatable hydrosilylation reaction catalysts as well.
Alternatively, the hydrosilylation reaction catalyst may be (C-II) a hydrosilylation catalyst activatable by means other than irradiation. For example, (C-II) may be (C-II-1) the platinum group metal, described above; (C-II-2) a compound of such a metal, for example, chloridotris(triphenylphosphane)rhodium(I) (Wilkinson's Catalyst), a rhodium diphosphine chelate such as [1,2-bis(diphenylphosphino)ethane]dichlorodirhodium or [1,2-bis(diethylphospino)ethane]dichlorodirhodium, chloroplatinic acid (Speier's Catalyst), chloroplatinic acid hexahydrate, platinum dichloride, and (C-II-3) a complex of a compound, (C-II-2), with an alkenyl functional organopolysiloxane oligomer, or (C-II-4) a platinum group metal compound microencapsulated in a matrix or coreshell type structure. Complexes of platinum with alkenyl functional organopolysiloxane oligomers include 1,3-diethenyl-1,1,3,3-tetramethyldisiloxane complexes with platinum (Karstedt's Catalyst) and Pt(0) complex in tetramethyltetravinylcyclotetrasiloxane (Ashby's Catalyst). Alternatively, the hydrosilylation reaction catalyst may be (C-II-5) a compound or complex, as described above, microencapsulated in a resin matrix. Specific examples of suitable platinum-containing catalysts for (C-II) include chloroplatinic acid, either in hexahydrate form or anhydrous form, or a platinum-containing catalyst which is obtained by a method comprising reacting chloroplatinic acid with an aliphatically unsaturated organosilicon compound such as divinyltetramethyldisiloxane, or alkene-platinum-silyl complexes as described in U.S. Pat. No. 6,605,734 to Roy. These alkene-platinum-silyl complexes may be prepared, for example by mixing 0.015 mole (COD)PtCl2 with 0.045 mole COD and 0.0612 moles HMeSiCl2, where COD represents cyclooctadienyl and Me represents methyl. Other exemplary hydrosilylation reaction catalysts are described in U.S. Pat. No. 2,823,218 to Speier; U.S. Pat. No. 3,159,601 to Ashby; U.S. Pat. No. 3,220,972 to Lamoreaux; U.S. Pat. No. 3,296,291 to Chalk, et al.; U.S. Pat. No. 3,419,593 to Willing; U.S. Pat. No. 3,516,946 to Modic; U.S. Pat. No. 3,814,730 to Karstedt; U.S. Pat. No. 3,928,629 to Chandra; U.S. Pat. No. 3,989,668 to Lee, et al.; U.S. Pat. No. 4,766,176 to Lee, et al.; U.S. Pat. No. 4,784,879 to Lee, et al.; U.S. Pat. No. 5,017,654 to Togashi; U.S. Pat. No. 5,036,117 to Chung, et al.; and U.S. Pat. No. 5,175,325 to Brown; and EP 0 347 895 A to Togashi, et al. U.S. Patent Application Publication 2019/0367744 to Chevalier et al. discloses both (C-II) radiation activatable catalysts and (C-II) catalysts activatable by means other than radiation (e.g., heat activatable catalysts). Other hydrosilylation reaction catalysts that may be used herein are as disclosed in “Hydrosilylation reaction of olefins: recent advances and perspectives,” by Y. Nakajima and S. Shimada, RSC Adv., 2015, 5, 20603-20616 and “Hydrosilylation, Advances in Silicon Science,” Chapter 1, Hydrosilylation of Alkenes and Their Derivatives, B. Marciniec (ed.) DOI 10.1007/978-1-4020-8172-9 1, © Springer Science+Business Media B.V. 2009 (pp. 2-49). Suitable hydrosilylation reaction catalysts for starting material (C-II) are commercially available, for example, SYL-OFF™ 4000 Catalyst and SYL-OFF™ 2700 are available from Dow Silicones Corporation of Midland, Michigan, USA.
Starting material (C) may be one hydrosilylation reaction catalyst or a combination of two or more of the hydrosilylation reaction catalysts described above. For example, starting material (C) may be a combination of (C-I) and (C-II), e.g., when both exposure to radiation and heating will be used for hydrosilylation reaction. Alternatively, starting material (C) may be a combination of two or more radiation activatable catalysts, such as a combination of a cyclopentadienyl platinum complex and a Pt(II)-ß diketonate complex. One skilled in the art would recognize that certain catalyst species may be activated by either irradiating or heating, as described herein and that when a combination of two or more catalysts is used, the catalyst species selected will differ from one another.
The amount of (C) the hydrosilylation reaction catalyst in the emulsion will depend on various factors including the selection of starting materials (A) and (B); and their respective contents of alkenyl groups and silicon bonded hydrogen atoms, and the amount of (D) hydrosilylation reaction inhibitor present in the composition, however, the amount of catalyst is sufficient to catalyze hydrosilylation reaction of SiH and alkenyl groups, alternatively the amount of catalyst is sufficient to provide at least 10 ppm, alternatively at least 15 ppm, alternatively at least 20 ppm, alternatively at least 50 ppm, and alternatively at least 100 ppm, by mass of the platinum group metal based on combined amounts of starting materials (A), (B), (C), (D), (E), (F), and (G) in the composition. At the same time, the amount of catalyst is sufficient to provide up to 1,000 ppm, alternatively up to 800 ppm, alternatively up to 500 ppm, and alternatively up to 100 ppm by mass of the platinum group metal, based on combined weights of starting materials (A) and (B) in the emulsion.
Starting material (D) in the emulsion is a hydrosilylation reaction inhibitor. Starting material (D) is a hydrosilylation reaction inhibitor (inhibitor) that may be used for altering the hydrosilylation reaction, as compared to a composition containing the same starting materials but with the inhibitor omitted. Starting material (D) may be, for example, (D1) an acetylenic alcohol, (D2) a silylated acetylenic alcohol, (D3) an ene-yne compound, (D4) a triazole, (D5) a phosphine, (D6) a mercaptan, (D7) a hydrazine, (D8) an amine, (D9) a fumarate, (D10) a maleate, (D11) an ether, (D12) carbon monoxide, (D13) an alkenyl-functional siloxane oligomer, and (D14) a combination of two or more thereof. Alternatively, the hydrosilylation reaction inhibitor may be selected from the group consisting of (D1) an acetylenic alcohol, (D2) a silylated acetylenic alcohol, (D9) a fumarate, (D10) a maleate, (D13) a combination of two or more thereof. Alternatively, the hydrosilylation reaction inhibitor may be selected from the group consisting of (D1) an acetylenic alcohol, (D2) a silylated acetylenic compound, (D9) a fumarate, (D10) a maleate, (D13) carbon monoxide, and (D14) a combination of two or more thereof.
Acetylenic alcohols are exemplified by 3,5-dimethyl-1-hexyn-3-ol, 1-butyn-3-ol, 1-propyn-3-ol, 2-methyl-3-butyn-2-ol, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 3-phenyl-1-butyn-3-ol, 4-ethyl-1-octyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol, and 1-ethynyl-1-cyclohexanol, and a combination thereof. Alternatively, the inhibitor may be a silylated acetylenic compound. Without wishing to be bound by theory, it is thought that adding a silylated acetylenic compound reduces yellowing of the reaction product prepared from hydrosilylation reaction as compared to a reaction product from hydrosilylation of starting materials that do not include a silylated acetylenic compound or that include an organic acetylenic alcohol inhibitor, such as those described above. The silylated acetylenic compound is exemplified by (3-methyl-1-butyn-3-oxy)trimethylsilane, ((1,1-dimethyl-2-propynyl)oxy)trimethylsilane, bis(3-methyl-1-butyn-3-oxy)dimethylsilane, bis(3-methyl-1-butyn-3-oxy)silanemethylvinylsilane, bis((1,1-dimethyl-2-propynyl)oxy)dimethylsilane, methyl(tris(1,1-dimethyl-2-propynyloxy))silane, methyl(tris(3-methyl-1-butyn-3-oxy))silane, (3-methyl-1-butyn-3-oxy)dimethylphenylsilane, (3-methyl-1-butyn-3-oxy)dimethylhexenylsilane, (3-methyl-1-butyn-3-oxy)triethylsilane, bis(3-methyl-1-butyn-3-oxy)methyltrifluoropropylsilane, (3,5-dimethyl-1-hexyn-3-oxy)trimethylsilane, (3-phenyl-1-butyn-3-oxy)diphenylmethylsilane, (3-phenyl-1-butyn-3-oxy)dimethylphenylsilane, (3-phenyl-1-butyn-3-oxy)dimethylvinylsilane, (3-phenyl-1-butyn-3-oxy)dimethylhexenylsilane, (cyclohexyl-1-ethyn-1-oxy)dimethylhexenylsilane, (cyclohexyl-1-ethyn-1-oxy)dimethylvinylsilane, (cyclohexyl-1-ethyn-1-oxy)diphenylmethylsilane, (cyclohexyl-1-ethyn-1-oxy)trimethylsilane, and combinations thereof. The silylated acetylenic compound useful as the inhibitor herein may be prepared by methods known in the art, for example, U.S. Pat. No. 6,677,407 to Bilgrien, et al. discloses silylating an acetylenic alcohol described above by reacting it with a chlorosilane in the presence of an acid receptor.
Alternatively, the inhibitor may be an ene-yne compound such as 3-methyl-3-penten-1-yne; 3,5-dimethyl-3-hexen-1-yne; and a combination thereof. Alternatively, the inhibitor may comprise a triazole, exemplified by benzotriazole. Alternatively, the inhibitor may comprise a phosphine. Alternatively, the inhibitor may comprise a mercaptan. Alternatively, the inhibitor may comprise a hydrazine. Alternatively, the inhibitor may comprise an amine. Amines are exemplified by tetramethyl ethylenediamine, 3-dimethylamino-1-propyne, n-methylpropargylamine, propargylamine, 1-ethynylcyclohexylamine, or a combination thereof. Alternatively, the inhibitor may comprise a fumarate. Fumarates include dialkyl fumarates such as diethyl fumarate, dialkenyl fumarates such as diallyl fumarate, dialkoxyalkyl fumarates such as bis-(methoxymethyl)ethyl fumarate. Alternatively, the inhibitor may comprise a maleate. Maleates include dialkyl maleates such as diethyl maleate, dialkenyl maleates such as diallyl maleate, and dialkoxyalkyl maleates such as bis-(methoxymethyl)ethyl maleate. Alternatively, the inhibitor may comprise an ether.
Alternatively, the inhibitor may comprise carbon monoxide. Alternatively, the inhibitor may comprise an alkenyl-functional siloxane oligomer, which may be cyclic or linear such as methylvinylcyclosiloxanes exemplified by 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetrahexenylcyclotetrasiloxane, 1,3-divinyl-1,3-diphenyl-1,3-dimethyldisiloxane; 1,3-divinyl-1,1,3,3-tetramethyldisiloxane; and a combination of two or more thereof. The compounds useful as inhibitors described above are commercially available, e.g., from Sigma-Aldrich Inc. or Gelest, Inc., and Suitable inhibitors for use herein are exemplified by those described as stabilizer E in U.S. Patent Application Publication 2007/0099007 at paragraphs [0148] to [0165].
Starting material (D) may be one hydrosilylation reaction inhibitor or a combination of two or more of the hydrosilylation reaction inhibitors described above. The amount of inhibitor used will depend on various factors including the desired reaction rate, the particular inhibitor used, and the selection and amounts of each of starting materials (A) to (C). However, when present, the amount of inhibitor may be >0 parts by mass, alternatively 0.02 weight part to 0.8 weight part, per 100 weight parts of starting material (A).
Starting material (E) is water, which is not generally limited, and may be utilized neat (i.e., without any carrier vehicles/solvents), and/or pure (i.e., free of minerals and/or other impurities). For example, the water may be processed or unprocessed prior to its combination with other starting materials in the emulsion. Examples of processes that may be used for purifying the water include distilling, filtering, deionizing, and combinations of two or more thereof, such that the water may be deionized, distilled, and/or filtered. Alternatively, the water may be unprocessed (e.g. may be tap water, i.e., provided by a municipal water system or well water, used without further purification). The water may be utilized in any amount, which will be selected by one of skill in the art, depending on various factors, including the desired dilution of the emulsion. However, the amount of water may be 30% to 99%, alternatively 50% to 99%, alternatively 50% to 95%, based on combined weights of all starting materials in the emulsion.
A buffer system (buffer) for maintaining a desired pH of the emulsion may be any suitable buffer, which may comprise a mono or polyprotic acid and its conjugate base. For example, a buffer comprising HCO3−/CO32− and H2PO4−/HPO42− described as agent F in U.S. Patent Application Publication 2007/0099007 at paragraphs [00145] to [00147] may be used herein. The buffer may comprise NaCO3 and NaHCO3; and/or citric acid and a citrate salt such as potassium citrate or sodium citrate. The amount of the buffer may be >0, alternatively at least 0.2 weight parts and alternatively at least 0.4 weight parts, per 100 weight parts of starting material (A). At the same time, the amount of buffer may be up to 1.6 weight parts, alternatively up to 1.5 weight parts, alternatively up to 1.25 weight parts, per 100 parts of starting material (A).
The surfactant used to emulsify may be nonionic or ionic. Alternatively, the surfactant may be nonionic. Suitable surfactants may be selected from may be selected from those that are known and the art and are commercially available. Suitable nonionic surfactants include alkylphenols, fatty alcohols or fatty acids with alkylene oxide groups, such as ethylene oxide or propylene oxide groups. Suitable ionic surfactants include anionic surfactants such as sulfates, sulfonates, phosphates, and sulfosuccinates. Suitable surfactants for use herein are exemplified by those described as surfactant (G) in U.S. Patent Application Publication 2007/0099007 at paragraphs [0167] to [0176]. The amount of surfactant depends on various factors, including whether starting material (H) the polyvinyl alcohol compound, is present, however the amount of surfactant may be 0 to 3 weight parts, per 100 weight parts of starting material (A), alternatively from 0 to 2 weight parts, alternatively from 0 to 1 weight parts, alternatively from 0 to 0.3 weight parts.
Starting material (H) in the emulsion is a polyvinyl alcohol compound. Polyvinyl alcohol compounds are known in the art and are disclosed, for example in U.S. Patent Application Publication 2007/0099007 at paragraphs [0172] and [0173]. Polyvinyl alcohol compounds may be made by saponification of polyvinylacetate, so up to 15% of polyvinylacetate may remain in the polyvinyl alcohol compound used herein. Alternatively, the polyvinyl alcohol compound may be 80% to 98% polyvinyl alcohol (with the balance being 20% to 2% polyvinylacetate). The polyvinyl alcohol compound may have a minimum viscosity of 5 cP at 4% aqueous solution at 20° C. The amount of the polyvinyl alcohol compound depends on various factors, including whether starting material (G) the surfactant, is present, however the amount of polyvinyl alcohol may be 0 to 10 weight parts, alternatively 0 to 5 weight parts, and alternatively 0 to 3.0 weight parts, per 100 weight parts of starting material (A). However, at least one of (G) the surfactant and (H) the polyvinyl alcohol is present in the emulsion. The amount of (G), (H), or the combination of both (G) and (H) may be at least 5.0 weight part per 100 parts by weight of starting material (A).
Starting material (I) is an optional biocide that may be added to the emulsion. Biocides are known in the art, for example, the biocide is exemplified by (I1) a fungicide, (I2) an herbicide, (I3) a pesticide, (I4) an antimicrobial agent, and a combination of two or more thereof. Exemplary biocides are disclosed, for example, in U.S. Pat. No. 9,221,041 to Brandstadt, et al. The biocide is optional. However, when used, the biocide may be present in an amount up to 1.0 weight parts, per 100 weight parts of starting material (A).
The emulsion may optionally further comprise starting material (J) an anti-foaming agent (anti-foam). The amount of starting material (J) may be up to 0.2 weight parts, per 100 weight parts of starting material (A). Suitable anti-foams are exemplified by emulsions containing silica and polydimethylsiloxanes. Such anti-foams are commercially available from Dow Silicones Corporation of Midland, Michigan, USA.
One or more additional starting materials may be added to the emulsion described herein. The one or more additional starting materials may be selected from the group consisting of a bactericidal agent (e.g., sorbic acid), a colorant (e.g., dye or pigment), a filler (e.g., silica), and a wetting agent (e.g., a glycol such as propylene glycol or ethylene glycol). Suitable additional starting materials for use herein are exemplified by the additives described in U.S. Patent Application Publication 2007/0099007 at paragraphs [0177] to [0190] and U.S. Patent Application Publication 2002/0061365 at paragraphs [0055] to [0056].
Notwithstanding the description above, the emulsion described herein is free of stabilizers selected from aliphatic polyethers, (co)polyacrylamides, polysaccharides, and polyacrylates. These stabilizers are long and flexible hydrophilic macromolecules of high molecular weights. As used herein, “free of stabilizers selected from aliphatic polyethers, (co)polyacrylamides, polysaccharides, and polyacrylates” means that such macromolecules are not intentionally added to the emulsion. The emulsion may contain none, or a non-detectable amount, of such macromolecules. If any such macromolecules are present in one or more of the starting materials used in the emulsion, any amount is insufficient to change the properties of any release coating prepared from the emulsion.
The emulsion described herein is also free of unreactive organopolysiloxanes. As used herein, “unreactive organopolysiloxanes” are polysiloxanes, which do not undergo hydrosilylation reaction with starting materials (A) and (B). Such unreactive organopolysiloxanes may have formula (R1)eSiO(4-e)/2, where R1=monovalent, optionally substituted hydrocarbon radicals with 1 to 10 carbon atoms from the group consisting of substituted and unsubstituted alkyl, phenyl, and phenylalkyl radicals which may be the same or different within the molecule, and e may be integers between 1 and 3. Examples of unreactive organopolysiloxanes are α,ω-trialkylsiloxy-terminated polydialkylsiloxanes, such as α,ω-trimethylsiloxy-terminated polydimethylsiloxanes. As used herein, “free of unreactive organopolysiloxanes” means that such unreactive organopolysiloxanes are not intentionally added to the emulsion. The emulsion may contain none, or a non-detectable amount, of such unreactive organopolysiloxanes. If any such unreactive organopolysiloxanes are present as impurities in one or more of the starting materials used in the emulsion, any amount thereof is insufficient to change the properties of any release coating prepared from the emulsion. Without wishing to be bound by theory, it is thought that the presence of unreactive organopolysiloxanes in release coatings prepared from the emulsion described herein may be detrimental to the performance of the release coating by, for example, by increasing extractables and/or decreasing anchorage on certain substrates as compared to release coatings prepared from emulsions which are free of unreactive organopolysiloxanes.
The emulsion may be prepared by combining the starting materials described above, in the amounts described above, in any order of addition, optionally with a master batch, and optionally under shear. Alternatively, the emulsion may be formed by subjecting said starting materials to high shear, for example in a mixer of the rotor and stator type or in an apparatus applying increased shear such as a high pressure homogenizer, microfluidizer, colloid mill, or sonolator (ultrasonic mixer). To avoid premature reaction during formation of the emulsion, some of the starting materials may be emulsified separately. For example, all or a portion of starting material (A) may be emulsified in the absence of starting material (B), starting material (B) being added subsequently. Alternatively, starting materials (A) and (B) may be emulsified in the absence of catalyst, with the catalyst being emulsified and added separately.
The present invention also provides a process of preparing a coated substrate with the emulsion. The method comprises disposing the emulsion on a surface of the substrate. The method further comprises curing at an elevated temperature, such as 50° C. to 120° C. to remove water and cure starting materials (A) and (B), thereby giving the coated substrate.
The emulsion may be disposed or dispensed on the surface of the substrate in any suitable manner. Typically, the emulsion is applied in wet form via a wet coating technique. In certain embodiments, the emulsion is applied by i) spin coating; ii) brush coating; iii) drop coating; iv) spray coating; v) dip coating; vi) roll coating; vii) flow coating; viii) slot coating; ix) gravure coating; or x) a combination of any of i) to ix). Typically, disposing the emulsion on the substrate results in a wet deposit on the substrate, which is subsequently dried and cured to give the coated substrate, which comprises a cured silicone release coating on the substrate.
The substrate is not limited and may be any substrate. The substrate may have an integrated hot plate or an integrated or stand-alone furnace for drying and curing the deposit. The substrate may optionally have a continuous or non-continuous shape, size, dimension, surface roughness, and other characteristics. In certain embodiments, the substrate has a softening point temperature at the elevated temperature.
The substrate may comprise a plastic, which maybe a thermosetting and/or thermoplastic. Alternatively, the substrate may comprise a paper, which may be suitable for food contact applications. Specific examples of suitable substrates include polyamides (PA); polyesters such as polyethylene terephthalates (PET), polybutylene terephthalates (PET), polytrimethylene terephthalates (PTT), polyethylene naphthalates (PEN), and liquid crystalline polyesters; polyolefins such as polyethylenes (PE), polypropylenes (PP), and polybutylenes; styrenic resins; polyoxymethylenes (POM); polycarbonates (PC); polymethylenemethacrylates (PMMA); polyvinyl chlorides (PVC); polyphenylene sulfides (PPS); polyphenylene ethers (PPE); polyimides (PI); polyamideimides (PAI); polyetherimides (PEI); polysulfones (PSU); polyethersulfones; polyketones (PK); polyetherketones (PEK); polyvinyl alcohols (PVA); polyetheretherketones (PEEK); polyetherketoneketones (PEKK); polyarylates (PAR); or polyethernitriles (PEN); celluloses such as triacetylcellulose, diacetylcellulose, or cellophane; and paper such as Kraft paper.
The emulsion, or wet deposit, is typically dried and cured at the elevated temperature for a period of time. The period of time is typically sufficient to effect curing, i.e., cross-linking, of starting materials comprising (A) and (B). In certain embodiments, the period of time is from greater than 0 to 8 hours, alternatively from greater than 0 to 2 hours, alternatively from greater than 0 to 1 hour, alternatively from greater than 0 to 30 minutes, alternatively from greater than 0 to 15 minutes, alternatively from greater than 0 to 10 minutes, alternatively from greater than 0 to 5 minutes, alternatively from greater than 0 to 2 minutes. The period of time depends on various factors including the elevated temperature selected, desired film thickness, and amount of water.
Curing typically has a dwell time of 1 to 50 seconds; alternatively 2 to 10 seconds. Dwell time, as used herein, refers to the time during which the starting materials comprising (A) and (B) are subjected to the elevated temperature. Dwell time is distinguished from cure time, as there may be ongoing curing even after the wet deposit, or partially cured reaction intermediary thereof is no longer subjected to the elevated temperature, which typically initiates curing. Alternatively, the coated article may be prepared on a conveyor belt in an oven, and the dwell time may be calculated by dividing a length of the oven (e.g., in meters) by a line speed of the conveyor belt (e.g., in meters/sec).
The period of time may be broken down into cure iterations, e.g., a first-cure and a post-cure, with the first-cure being, for example, one hour and the post cure being, for example, three hours. The elevated temperature may be independently selected from any temperature above room temperature in such iterations and may be the same in each iteration.
Depending on a thickness and other dimensions of the film and coated substrate, the coated substrate can be formed via an iterative process. For example, a first deposit may be formed and subjected to a first elevated temperature for a first period of time to give a partially cured deposit. Then, a second deposit may be disposed on the partially cured deposit and subjected to a second elevated temperature for a second period of time to give a second partially cured deposit. The partially cured deposit will also further cure during exposure to the second elevated temperature for the second period of time. A third deposit may be disposed on the second partially cured deposit and subjected to a third elevated temperature for a third period of time to give a third partially cured deposit. The second partially cured deposit will also further cure during exposure to the second elevated temperature for the second period of time. This process may be repeated, for example, from 1 to 50 times, to build the coated article as desired. A composite is of partially cured layers is typically subjected to a final post-cure, e.g. at the elevated temperature and period of time above. Each elevated temperature and period of time may be independently selected and may be the same as or different from one another. When the article is formed via the iterative process, each deposit may also be independently selected and may differ in terms of components selected in the composition and/or their amounts. Alternatively still, each iterative layer may be fully cured, rather than only being partially cured, in such an iterative process.
The deposit may comprise a wet film, and the iterative process may be wet-on-wet, depending on a cure state of the partially cured layer. Alternatively, the iterative process may be wet-on-dry. The coated substrate, which comprises the film formed from the emulsion on the substrate, may have varying dimensions, including relative thicknesses of the film and the substrate. When cured, the resulting silicone release coating has a thickness that may vary depending upon its end use application. Typically, the silicone release coating has a thickness of from greater than 0 to <1 μm, alternatively from greater than 0 to 0.9 μm, alternatively from greater than 0 to 0.75 μm, alternatively from greater than 0 to 0.5 μm, alternatively from greater than 0 to 0.25 μm, alternatively from greater than 0 to 0.2 μm. However, other thicknesses are contemplated, e.g. from 0.05 μm to 0.2 μm. For example, the thickness of the film may be from 0.1 μm to 10 μm; alternatively from 0.15 μm to 5 μm; alternatively from 0.2 μm to 2 μm; and alternatively from 0.2 μm and 0.6 μm. Alternatively, when the substrate is plastic, the film may have a thickness of from 0.05 to <1 μm, alternatively from 0.05 to 0.9 μm, alternatively from 0.05 to 0.8 μm. Alternatively, when the substrate is paper, the film may have a thickness of from 0.2 to <1 μm, alternatively from 0.2 to 0.9 μm, alternatively from 0.2 to 0.8 μm, alternatively from 0.2 μm to 0.7 μm, alternatively from 0.2 μm to 0.6 μm; alternatively 0.2 μm to 0.5 μm; and alternatively from 0.2 μm to 0.3 μm.
The coated substrate may be utilized in diverse end use applications. For example, the coated substrate may be utilized in coating applications, packaging applications, adhesive applications, fiber applications, fabric or textile applications, construction applications, transportation applications, (opto)electronics applications such as device fabrication, electrical applications, photonics applications, and food contact applications such as bakery release. Alternatively, when the substrate is paper, the coated substrate may be used in food contact applications such as bakery release. Alternatively, when the substrate is plastic, the coated substrate may be used in (opto)electronics applications such as device fabrication.
These examples are intended to illustrate the invention to one of ordinary skill in the art and are not to be construed as limiting the invention set forth in the claims. The starting materials used in these examples are described below in Table 1.
Starting materials with the DOWSIL™ and SYL-OFF trademarks are commercially available from DSC, which means Dow Silicones Corporation of Midland, Michigan, USA.
NMR spectroscopy was used to determine the vinyl content, hexenyl content and SiH content of starting materials in Table 1 as follows. Nuclear Magnetic Resonance (NMR) spectra were obtained on a NMR BRUKER AVIII (400 MHz), using a silicon-free 10 mm tube and CDCl3/Cr(AcAc)3 solvent. Chemical shifts for 29Si-NMR spectra were referenced to internal solvent resonance and are reported relative to tetramethylsilane.
Dynamic viscosity of starting materials in Table 1 was measured as follows. Dynamic viscosity (DV) was measured with a Brookfield Viscometer DV-I Prime equipped with spindle 2 to 4, at speed from 20 to 100 rpm and at a temperature of 25° C.
In this Reference Example 1, samples of base emulsions were prepared by combining the starting materials and their amounts as shown below in the tables. Amounts of each starting material are in weight %. The preparation of base emulsion was made in the lab. The pH buffered water containing water, citric acid monohydrate and sodium hydroxide was first weighed and blended. The polymers were weighed and blended separately, and the surfactants were added under mixing. The buffered water was then poured and stirred for 5 minutes. The premix was then emulsified using the High Pressure Sonolator at 100 bars until targeted particle size was reached. The recovered quantity was blended with the hydrosilylation inhibitor and the biocide package.
In this Reference Example 2, samples of emulsions (Bath/Emulsion) were prepared as follows: A base emulsion prepared as described in Reference Example 1 was combined with a catalyst emulsion (C-1) or (C-2), water, and an antifoam, which are described in Table 1. Amounts in weight parts are shown in Table 5.
In this Reference Example 3, bakery paper substrates were treated with emulsions prepared as described in Reference Example 2 with an average silicon coat weight of 0.32 g/m2. Silicon coat weight, post-cure extractables, water uptake, and anchorage were evaluated as follows:
Silicon coat weights were measured by X-ray Fluorescence using an Oxford lab-x3500 XRF Analyzer after silicon elemental calibration with samples' standards. An XRF measure of a blank substrate was performed prior to 3 measures of coated-paper samples leading to an average silicon coat weight or thickness expressed in g/m2.
The water resistance of paper substrates was tested by the conventional absorption test known as Cobb test described for instance in TAPPI 441 om-04 test method. Samples were exposed to water for 45 seconds and the amount of water absorbed after a total of 60 seconds was measured by the weight. The “Cobb value” represented the mass of absorbed water expressed in g/m2. The lower the Cobb value, the higher the water resistance of the substrate. A Cobb value of less than 20 g/m2 was desired by some customers, and a Cobb value less than 15 g/m2 was desired by other customers.
The anchorage test provided a quantitative determination of the rub-off resistance of silicone release coating anchoring on the substrate after an abrasion test. The silicon content of a coated substrate was determined by XRF before and after rub-off with an abrasion tester and was expressed as a % of Si left after rub-off compared to 100% initially coated. The higher the Si % left after rub-off the higher the anchorage or abrasion resistance.
Silicone extractables in % of a coated paper was measured by its silicone CW before vs. after (20 min) immersion in MIBK. The solvent dissolves uncured silicone and the percentage loss is determined. This test is carried out immediately after the paper was coated and after 24 h aging at RT, called immediate extractable (‘IM Ext’) and post-cure extractable (‘PC Ext’). The results are reported in Table 6.
The results in Table 6 showed that the comparative samples, which did not contain a hexenyl-functional polyorganosiloxane (i.e., 1 and 3) produced release coatings with insufficient anchorage or water uptake that was higher than desired for a bakery paper application.
The release coating made with the emulsion containing sample 8 from Table 3 showed much higher anchorage (92.2 vs. 82.7%) thus better abrasion resistance than sample 1 from Table 2. Without wishing to be bound by theory, it is thought that when a hexenyldimethylsiloxy-endblocked polydimethylsiloxane was used (in sample 8) instead of a vinyldimethylsiloxy-endblocked polydimethylsiloxane (in sample 1), higher anchorage (higher abrasion resistance) reduced the dust formation. The water uptake, or Cobb value, was also significantly lower (13.1 vs. 16.7 g/m2) when a hexenyldimethylsiloxy-endblocked polydimethylsiloxane was used instead of a vinyldimethylsiloxy-endblocked polydimethylsiloxane, and higher water resistance is a benefit for food contact applications; e.g. for release of steam from food and water resistance for frozen food.
Samples 10 and 12 from Table 3, contained 1% or 2% unreactive trimethylsiloxy-endblocked PDMS, respectively, and produced release coatings with similar to superior anchorage compared to that produced by sample 3 (90.6 and 92.9 vs. 91.3%) with again a significant reduction in water uptake (13.8 and 12.5 vs. 15.9 g/m2).
In this Reference Example 4, bakery papers were treated with emulsions prepared as described in Reference Example 2 with an average silicon coat weight of 0.44 g/m2. The resulting samples were evaluated as described above in Reference Example 3. In addition, air barrier and baking residues were evaluated as follows.
The air permeability of different paper substrates was measured with an L&W Air Permeability Tester by sensing the air flow through the sample and the pressure difference across the two sides. Standard test methods SCAN-P 26:78 or TAPPI 536 om-12 for ‘Resistance of paper to passage of air (high-pressure Gurley method)’ was applied. The air permeability was expressed in Gurley seconds or Gurley unit. The higher the time in Gurley, the lower the air permeability of a paper specimen, the better the air barrier.
The bakery release or baking test measured the quantity of food left on a substrate after oven baking and release. Coated paper samples were folded into molds and weighed. Cake dough containing 4 eggs, 80 g of sugar, 80 and 85 g of potato and wheat flours respectively, and 5.5 g of baking powder were processed at room temperature with a universal kitchen machine and placed into the molds prior to oven baking. The finished baked products were cooled down. The coated paper to be tested was then removed from the baked product and the quantity of baked product still adhering to the paper was weighed and converted in g/m2. The lower the bakery release values the better. The results are reported in Table 7.
The results in Table 7 show that the release coating made with Sample 1 from Table 2 suffered from the drawback of a low abrasion resistance as evidenced by low anchorage of 81.9% and a low air barrier of 833. By increasing the content of the hexenyldimethylsiloxy-endblocked polydimethylsiloxane over the vinyldimethylsiloxy-endblocked polydimethylsiloxane in the base emulsions, abrasion resistance (anchorage) was increased, as shown by the release coatings prepared with samples 15-18 from Table 3. Without wishing to be bound by theory, it is thought that that under the conditions tested, a maximum value for anchorage was achieved when the ratio of hexenyldimethylsiloxy-endblocked polydimethylsiloxane to vinyldimethylsiloxy-endblocked polydimethylsiloxane was reached in sample 18 because of increasing the amount of hexenyldimethylsiloxy-endblocked polydimethylsiloxane to 90% or 100% (with a corresponding decrease of vinyldimethylsiloxy-endblocked polydimethylsiloxane to 10% or to 0) in samples 19 and 20, respectively, did not significantly change anchorage. The data in Table 7 further shows that as the amount of hexenyldimethylsiloxy-endblocked polydimethylsiloxane increased from 75% to 100%, the air barrier property improved (increased), but baking residues property was detrimentally impacted (increased). However, samples 15-20 produced coated papers suitable for use for preparing bakery papers.
In this Reference Example 5, bakery papers were treated with emulsions prepared as described in Reference Example 2 with an average silicon coat weight of 0.45 g/m2. The resulting samples were evaluated as described above in Reference Example 3. The results are shown below in Table 8.
Varying the relative amounts of vinyldimethylsiloxy-terminated poly(dimethyl/methylvinyl)siloxane and hexenyldimethylsiloxy-terminated poly(dimethyl/methylhexenyl)siloxane was evaluated, and the results are shown above in Table 8. The combination of both polyorganosiloxanes dramatically improved cure (as shown by a drop in post cure extractables % from 18.9 using only a vinyldimethylsiloxy-terminated poly(dimethyl/methylvinyl)siloxane in the base emulsion, down to 9.5 when a 90:10 ratio of hexenyldimethylsiloxy-terminated poly(dimethyl/methylhexenyl)siloxane and vinyldimethylsiloxy-terminated poly(dimethyl/methylvinyl)siloxane was used), improved anchorage from 85.9 up to 90.4 and positively reduced water uptake from 13.2 down to 12.4. These examples showed that when only 10% hexenyldimethylsiloxy-terminated poly(dimethyl/methylhexenyl)siloxane was used in the base emulsion formulated into a release coating composition on a paper substrate, the resulting release coating did not have the desired water uptake for a food contact application. Surprisingly, the best performance under the conditions tested herein was obtained when a combination of 90% hexenyldimethylsiloxy-terminated poly(dimethyl/methylhexenyl)siloxane and 10% vinyldimethylsiloxy-terminated poly(dimethyl/methylvinyl)siloxane was used because this sample (13) produced a release coating with the lowest water uptake and highest anchorage of the samples tested (including sample 2, which used 100% vinyldimethylsiloxy-terminated poly(dimethyl/methylvinyl)siloxane (no hexenyl) and 14, which used 100% hexenyldimethylsiloxy-terminated poly(dimethyl/methylhexenyl)siloxane (no vinyl).
In this Reference Example 6, PET film substrates were treated with emulsions prepared as described in Reference Example 2 with an average silicon coat weight of 0.2 g/m2. A combination of a vinyl-functional polyorganosiloxane and a hexenyl-functional polyorganosiloxane was used in base emulsions. The resulting samples were evaluated as described above in Reference Example 3. The results are shown below in Table 9.
The release coatings prepared from emulsions containing vinyldimethylsiloxy-endblocked polydimethylsiloxanes (5 and 6) showed high extractables (over 10%) and poor (low) anchorage to (and thus poor abrasion resistance on) PET films. Sample 6, which included 1% trimethylsiloxy-endblocked polydimethylsiloxane had even worse anchorage and extractables than Sample 5, which did not include a trimethylsiloxy-endblocked polydimethylsiloxane. Although sample 7 had a decrease in extractables as compared to samples 5 and 6, the extractables of sample 7 were still higher than desired (>5%), and the anchorage value of 41.9% was still quite low. Without wishing to be bound by theory, it is thought that the presence of an unreactive organopolysiloxane (such as the 1% of trimethylsiloxy-endblocked polydimethylsiloxane in sample 6) will detrimentally affect (increase) extractables in release coatings prepared from emulsions containing even small amounts of unreactive organopolysiloxanes (e.g., 1% to 2%). Therefore, the emulsions described herein are free of unreactive organopolysiloxanes (such as the trimethylsiloxy-endblocked polydimethylsiloxanes described in Table 1).
Release coatings prepared from samples 21 and 22 (which included a combination of a hexenyldimethylsiloxy-endblocked poly(dimethyl/methylhexenyl)siloxane and a vinyldimethylsiloxy-endblocked polydimethylsiloxane) had the lowest extractables and consequently the highest abrasion resistance of the samples tested in Table 9. Without wishing to be bound by theory, it is thought that lowering extractables was due to the addition of the polyorganosiloxane with the hexenyl group.
In this Reference Example 7, the study in Reference Example 6 was repeated under different coating conditions (average coat weight of 0.2 g/m2) focusing at using a poly(dimethyl/methylhexenyl)siloxane blended at different ratios with a poly(dimethyl/methylvinyl)siloxane.
Table 10 below shows that again the release coating made from sample 7 (which contained a vinyldimethylsiloxy-endblocked poly(dimethyl/methylvinyl)siloxane and no hexenyl-functional polyorganosiloxane) had the lowest anchorage (lowest abrasion resistance) under the conditions tested. The anchorage increased with increasing amount of hexenyldimethylsiloxy-endblocked poly(dimethyl/methylhexenyl)siloxane in the base emulsion. At a 50:50 ratio of poly(dimethyl/methylvinyl)siloxane:poly(dimethyl/methylhexenyl)siloxane, the anchorage more than doubled, then plateaued above that ratio.
In Table 10, an optimum of performance was found at a 50:50 ratio of the poly(dimethyl/methylhexenyl)siloxane:poly(dimethyl/methylvinyl)siloxane in the base emulsion. Without wishing to be bound by theory, this further demonstrates that including both a hexenyl-functional polyorganosiloxane and a vinyl-functional polyorganosiloxane in the base emulsion leads to a release coating on a PET film substrate with benefits to one or more of the extension of the cure (lowered extractables), and increased anchorage (increased abrasion resistance).
Without wishing to be bound by theory, it is further thought that combining a hexenyl-functional polyorganosiloxane, particularly a poly(dimethyl/methylhexenyl)siloxane and a vinyl-functional polyorganosiloxane in an emulsion as described herein may provide one or more benefits (over a comparable release coating emulsion containing the vinyl-functional polyorganosiloxane but not the hexenyl-functional polyorganosiloxane), particularly on plastic film substrates such as PET. For example, it is thought that cure speed improves, extractables will decrease by a factor up to 5, anchorage will increase by a factor up to two.
Problems to be Addressed: The use of silicone emulsions for coating paper substrates for food contact applications, thereby providing the paper substrate, e.g., bakery paper, with release performance and water resistance is desired as an attractive alternative to the health concerns related to fluorinated materials and chromium containing materials for the same application. However, paper machine in-line runnability issues, such as dust formation has been a major difficulty for the use of silicone emulsions.
Furthermore, the use of silicone emulsions for coating other substrates, such as plastic films, is also desirable for many applications, including but not limited to labels, general tapes and liners for sun block film and water proofing tapes. Furthermore, release liners with a release coating on a plastic film substrate also find use in the (opto)electronics industry where a release coating with a smooth surface and minimal or no dust is desired. There are industry needs for silicone emulsions, which are stable, and which can be cured to form release coatings with high SAS (Subsequent Adhesion Strength) and low and stable release force.
Solution: The silicone emulsion described herein is versatile in that it can be used to prepare a release coating on various substrates, including both paper substrates and plastic film substrates. The silicone emulsion described herein can be used to prepare a release coating on a paper substrate suitable for food contact applications. The silicone emulsion can be applied to a paper substrate and cured to form a release coating thereon with no or minimal dust formation (as shown in the examples above where the anchorage test method described above shows a high percentage of silicone release coating remaining on the substrate after the test.
Furthermore, the silicone release coating emulsion described herein has lower viscosity than previously disclosed solventless curable silicone compositions. Without wishing to be bound by theory, it is thought that the emulsion described herein enables better control of the thickness of the silicone release coating to be prepared, and a lower range of thicknesses, at the same coating speeds used for solventless processes, and with no mist observed during the process of applying the emulsion to the substrate. This can provide environmental, health, and safety benefits, financial benefits in lower costs of production, and coating quality benefits (in that eliminating mist reduces or eliminates surface defects). Furthermore, the thin layer of silicone release coating achieved on paper substrates may make the coated papers more favorable for composting/recycling as less silicone release coating is deposited on the surface of the substrate. Furthermore, the emulsion described herein may produce silicone release coatings with additional technical advantages over solventless curable silicone compositions due to thinner coating, faster cure, and deeper section cure, than achievable with a thicker solventless coating. Furthermore the emulsion described herein may produce a silicone release coating with other benefits (as compared to a coating produced with a solventless curable silicone composition), such as lower extractables, thereby minimizing migration onto food or sensitive (opto)electronic components that could be contaminated, anchorage/abrasion resistance above 90%, low/no mist, lower dust formation, and/or lower cost. Furthermore, the emulsion described herein produces a smooth silicone release coating surface with lower coating weight, which can minimize risks of blocking issues. This is both important for, e.g., bakery paper during oven baking or microwaving to have a thin/breathable substrate to let the vapor out for proper cooking, and also for multilayer ceramic capacitor (MLCC) and polarizer film applications to have high quality coatings. The emulsion described herein may also allow hydrophilic additives to be added, such as anti-static additives, or anchorage additives such as alkoxyorganosilanes, which are not readily soluble or dispersible in solventless viscous curable silicone compositions.
In this application, all amounts, ratios, and percentages are by weight unless otherwise indicated. The amounts of all starting materials in an emulsion or other composition total 100% by weight. The SUMMARY and ABSTRACT are hereby incorporated by reference. The articles ‘a’, ‘an’, and ‘the’ each refer to one or more, unless otherwise indicated by the context of specification. The singular includes the plural unless otherwise indicated. The transitional phrases “comprising”, “consisting essentially of”, and “consisting of” are used as described in the Manual of Patent Examining Procedure Ninth Edition, Revision 08.2017, Last Revised January 2018 at section § 2111.03 I., II., and III. The abbreviations used herein have the definitions in Table 11. The disclosure of ranges includes the range itself and also anything subsumed therein, as well as endpoints. For example, disclosure of a range of, for example, 15 to 400 includes the subsets of, for example, 15 to 137, 138 to 265, and 266 to 400, as well as any other subset subsumed in the range. Similarly, the disclosure of Markush groups includes the entire group and also any individual members and subgroups subsumed therein. For example, disclosure of the Markush group (i) α,ω-dimethylhydrogensiloxy-terminated poly(dimethylsiloxane/methylhydrogensiloxane), (ii) α,ω-dimethylhydrogensiloxy-terminated polymethylhydrogensiloxane, (iii) α,ω-trimethylsiloxy-terminated poly(dimethylsiloxane/methylhydrogensiloxane), (iv) α,ω-trimethylsiloxy-terminated polymethylhydrogensiloxane, (v) α-dimethylhydrogensiloxy-ω-trimethylsiloxy-terminated poly(dimethylsiloxane/methylhydrogensiloxane), (vi) α-dimethylhydrogensiloxy-ω-trimethylsiloxy-terminated polymethylhydrogensiloxane, (vii) a combination of two or more thereof, includes the member (iii) α,ω-trimethylsiloxy-terminated poly(dimethylsiloxane/methylhydrogensiloxane) individually; the subgroup (iii) α,ω-trimethylsiloxy-terminated poly(dimethylsiloxane/methylhydrogensiloxane) and (iv) α,ω-trimethylsiloxy-terminated polymethylhydrogensiloxane, and any other individual member and subgroup subsumed therein.
The following abbreviations used in this application have the definitions described below in Table 11.
In a first embodiment, a silicone release coating emulsion comprises:
In a second embodiment, in the emulsion of the first embodiment, starting material (A1) is present in an amount of 25 weight parts to <100 weight parts, and starting material (A2) is present in an amount of >0 to 75 weight parts.
In a third embodiment, in the emulsion of the first embodiment or the second embodiment, (B) the polyorganohydrogensiloxane has unit formula
(R13SiO1/2)w(R12HSiO1/2)x(R12SiO2/2)y(R1HSiO2/2)z, where subscript w is 0, 1, or 2; subscript x is 0, 1, or 2; subscript y is 0 to 250, and subscript z is 1 to 250; with the provisos that (w+x)=2; (x+z)≥3; and a quantity (w+x+y+z) is 10 to 300.
In a fourth embodiment, in the emulsion of any one of the first to third embodiments, (B) the polyorganohydrogensiloxane is selected from the group consisting of: (i) α,ω-dimethylhydrogensiloxy-terminated poly(dimethylsiloxane/methylhydrogensiloxane),
In a fifth embodiment, in the emulsion of any one of the first to fourth embodiments, (B) the polyorganohydrogensiloxane is present in an amount sufficient to provide an SiH/Vi ratio of 1.4/1 to 2.5/1.
In a sixth embodiment, in the emulsion of any one of the first to fifth embodiments, the hydrosilylation reaction catalyst is selected from the group consisting of (C-I) a radiation activatable catalyst, (C-II) a hydrosilylation catalyst activatable by means other than irradiation, and (C-III) a combination of both (C-I) and (C-II).
In a seventh embodiment, in the emulsion of any one of the first to sixth embodiments, (C) the hydrosilylation reaction catalyst is selected from the group consisting of (C1) a metal selected from the group consisting of platinum, rhodium, ruthenium, palladium, osmium, and iridium; (C2) a compound of the metal; (C3) a complex of the metal or the compound; and (C4) the compound or the complex microencapsulated in a resin matrix or coreshell type structure.
In an eighth embodiment, in the emulsion of any one of the first to seventh embodiments, (D) the hydrosilylation reaction inhibitor is selected from the group consisting of (D1) an acetylenic alcohol, (D2) a silylated acetylenic alcohol, (D3) an ene-yne compound, (D4) a triazole, (D5) a phosphine, (D6) a mercaptan, (D7) a hydrazine, (D8) an amine, (D9) a fumarate, (D10) a maleate, (D11) an ethers, (D12) carbon monoxide, and (D13) a combination of two or more thereof.
In a ninth embodiment, in the emulsion of any one of the first to eighth embodiments, (D) the hydrosilylation reaction inhibitor is selected from the group consisting of (D1) an acetylenic alcohol, (D2) a silylated acetylenic alcohol, (D9) a fumarate, (D10) a maleate, (D13) a combination of two or more thereof.
In a tenth embodiment, in the emulsion of any one of the first ninth embodiments, (F) the buffer system comprises a mono- or poly-protic acid and its conjugate base.
In an eleventh embodiment, in the emulsion of any one of the first to tenth embodiments, (G) the surfactant is present and comprises a nonionic surfactant.
In a twelfth embodiment, in the emulsion of any one of the first to eleventh embodiments, (H) the polyvinyl alcohol is present.
In a thirteenth embodiment, the emulsion of any one of the first to twelfth embodiments further comprises starting material (I) up to 1.0 weight parts, per 100 weight parts of starting material (A), of a biocide.
In a fourteenth embodiment, the emulsion of any one of the first to thirteenth embodiments further comprises starting material (J) up to 0.2 weight parts, per 100 weight parts of starting material (A), of an anti-foam.
In a fifteenth embodiment, in the emulsion of any one of the preceding embodiments,
In a sixteenth embodiment, in the emulsion of the fifteenth embodiment,
In a seventeenth embodiment, in the emulsion of the fifteenth embodiment,
In an eighteenth embodiment, a process comprises:
In a nineteenth embodiment, in the process of the eighteenth embodiment, the substrate is paper.
In a twentieth embodiment, in the emulsion of the fifteenth embodiment,
In a twenty-first embodiment, in the emulsion of the fifteenth embodiment,
In a twenty-second embodiment, a process comprises:
In a twenty-third, in the process of the twenty-second embodiment, the substrate is plastic.
In a twenty-fourth embodiment, in the emulsion or process of any one of the preceding embodiments, each R1 is methyl.
In a twenty-fifth embodiment, a silicone release coating emulsion comprises
In a twenty-sixth embodiment, in the emulsion of the twenty-fifth embodiment, starting material (A1) is present in an amount of 75 weight parts to 90 weight parts, and starting material (A2) is present in an amount of 10 weight parts to 25 weight parts
In a twenty-seventh embodiment, in the emulsion of the twenty-fifth embodiment, starting material (A1) is present in an amount of >50 weight parts to <100 weight parts, and starting material (A2) is present in an amount of >0 to <50 weight parts.
In a twenty-eighth embodiment, in the emulsion of the twenty-fifth embodiment, starting material (A1) is present in an amount of 33 weight parts to 90 weight parts, and starting material (A2) is present in an amount of 10 weight parts to 67 weight parts.
In a twenty-ninth embodiment, in the process of the nineteenth embodiment, the process produces a silicone release coating with a thickness of 0.2 to <1 μm on the substrate.
In a thirtieth embodiment, in the process of the twenty-ninth embodiment, the process produces a silicone release coating with a thickness of 0.2 to 0.6 μm on the substrate.
In a thirty-first embodiment, in the process of the twenty-third embodiment, the process produces a silicone release coating with a thickness of 0.05 to <1 μm on the substrate. release coating with a thickness of 0.2 to 0.6 μm on the substrate.
In a thirty-second embodiment, in the process of the thirty-first embodiment, the process produces a silicone release coating with a thickness of 0.05 to 0.6 μm on the substrate.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 63/152,354 filed on 23 Feb. 2021 under 35 U.S.C. § 119 (e). U.S. Provisional Patent Application Ser. No. 63/152,354 is hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2022/015433 | 2/7/2022 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 63152354 | Feb 2021 | US |
